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  • Articles  (26,802)
  • Oxford University Press  (26,802)
  • National Academy of Sciences
  • Public Library of Science
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (25,809)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (993)
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  • 1
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    Underplanting is a practical silvicultural method for regenerating and diversifying conifer stands in Britain (2020)
    Oxford University Press
    Details
    Publication Date: 2020-07-30
    Description: There is a strong policy move in Britain to improve forest resilience to climate change by increasing stand structural and species diversity. Although currently little used in Britain, the technique of underplanting allows regeneration and diversification of stands while avoiding some of the disadvantages of clearfelling. Two experiments were examined: (1) the growth and survival of five underplanted conifer species of differing shade tolerance in a shelterwood and (2) compared performance of underplanted and open-grown Douglas-fir seedlings on restocking sites. Underplanted Sitka spruce, Norway spruce, noble fir, European silver fir and Douglas-fir were all able to survive and grow. However increased exposure following overstorey removal resulted in some damage and ‘socketing’, especially to taller seedlings, particularly Douglas-fir. This may be linked to poor root development when growing under an overstorey. Microclimate conditions on some underplanted sites were more sheltered from extreme climatic conditions, and in some cases this improved survival of Douglas-fir seedlings. However, seedling growth rates were reduced compared with those on open sites probably due to lower light levels. Underplanting may help to improve establishment success of some species, particularly in exposed areas. However, the shelter benefits of underplanting must be carefully balanced against the trade-off with lower light, and underplanting is likely to be more successful where low canopy density is maintained.
    Print ISSN: 0015-752X
    Electronic ISSN: 1464-3626
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 2
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    Is Xylella fastidiosa a serious threat to European forests? (2020)
    Oxford University Press
    Details
    Publication Date: 2020-08-06
    Description: The recent emergence of Olive Quick Decline Syndrome in Italy, caused by Xylella fastidiosa, has drawn attention to the risks posed by this vector-borne bacterium to important crops in Europe (especially fruit trees and grapevine). Comparatively very little is known on actual and potential impacts of this pathogen in forests, in the native (North American) and introduced (European) regions, respectively. The present review aims to address important questions related to the threat posed by X. fastidiosa to European forests, such as the following: What are the symptoms, hosts and impact of bacterial leaf scorch caused by X. fastidiosa on trees in North America? Which forest tree species have been found infected in the introduction area in Europe? How does X. fastidiosa cause disease in susceptible hosts? Are there any X. fastidiosa genotypes (subspecies and sequence types) specifically associated with forest trees? How is X. fastidiosa transmitted? What are the known and potential vectors for forest trees? How does vector ecology affect disease? Is the distribution of X. fastidiosa, especially the strains associated with trees, restricted by climatic factors? Is disease risk for trees different in forest ecosystems as compared with urban settings? We conclude by pointing to important knowledge gaps related to all these questions and strongly advocate for more research about the Xylella-forest pathosystems, in both North America and Europe.
    Print ISSN: 0015-752X
    Electronic ISSN: 1464-3626
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 3
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    Effects of Native Tree Planting on Soil Recovery in Tropical Montane Cloud Forests (2020)
    Oxford University Press
    Details
    Publication Date: 2020-07-06
    Description: The tropical montane cloud forest is one of the most biodiverse ecosystems on Earth and is one of the areas most threatened by anthropogenic disturbance. This study assessed the temporal impact on soil properties (organic carbon, total nitrogen, cation exchange capacity, bulk density) following establishment of native tree species in two degraded tropical montane cloud forest areas with different soil types and land-use intensities in south-east Mexico. In Pueblo Nuevo, Chiapas, Pinus chiapensis and Alnus spp. were established at two sites with humic Nitisols with low and moderate disturbance levels, respectively. In Xalapa, Veracruz, plum pine (Podocarpus matudae), American hornbeam (Carpinus caroliniana), Oaxaca walnut (Juglans pyriformis Liebm.), and sweetgum (Liquidambar styraciflua) were established on a grassland-covered humic Andosol with a high level of disturbance. After 16 years, soil properties had generally improved, although in the initial years after planting, the values declined, indicating a possible negative impact because of disturbance during tree establishment. Land-use intensity prior to tree establishment influenced the level of recovery in soil properties. The Pueblo Nuevo sites, with low to moderate disturbance levels, regained soil quality faster than the highly disturbed Xalapa site, despite better initial soil quality in the latter.
    Print ISSN: 0015-749X
    Electronic ISSN: 1938-3738
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 4
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    Modelling variation in wood stiffness of Pinus ponderosa using static bending and acoustic measurements (2020)
    Oxford University Press
    Details
    Publication Date: 2020-08-01
    Description: Wood removed in Southwestern US forest restoration treatments currently has limited markets and thus low value. One important property of wood in structural products is its stiffness (measured as modulus of elasticity), which is known to vary systematically within trees. Directly measuring wood stiffness is expensive, time consuming and destructive. Therefore, we tested samples of ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) from northern Arizona destructively in bending and also non-destructively using acoustic velocity (AV) methods. In total, we tested multiple pith-to-bark small clear (2.54 × 2.54 × 40.64 cm) samples from up to four heights in 103 trees. We first measured the standing-tree AV of sample trees, then the AV of small clear samples, and finally measured wood stiffness using three point static bending tests. We found that a Michaelis–Menten curve was a good fit to the radial profile of wood stiffness, with a steep increase outward from the pith that approached an asymptote. The AV of small clear samples, coupled with measured volumetric density values, approximated the static modulus of elasticity values with high accuracy (r2 = 0.86). At the stand level, a model predicting standing tree AV from tree morphology fit the data well (r2 = 0.77). Results indicate that southwestern ponderosa pine contains outerwood with relatively high stiffness that could be suitable for structural products. However, when assessed using wood stiffness, the trees take a long time to reach maturity (~50 years) and thus the corewood proportion is large. AV measurements are a good way to assess variability within and among stands and thus could be employed to segregate the resource by expected stiffness values. Segregation could help identify stands not suitable for structural uses and direct them toward more appropriate products.
    Print ISSN: 0015-752X
    Electronic ISSN: 1464-3626
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 5
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    The 17th Symposium on Systems Analysis in Forest Resources: An Introduction and Synthesis (2020)
    Oxford University Press
    Details
    Publication Date: 2020-07-03
    Description: The 17th Symposium on Systems Analysis in Forest Resources was held in Suquamish, Washington, United States on August 27–30, 2017. The goal of this international meeting was to bring together operations researchers, remote sensing scientists, and the government to facilitate the exchange and implementation of systems science in forestry and conservation. The essay that follows is a summary of the outcome of the Symposium, as well as an introduction to the eight research articles that were selected for publication in this Special Issue. Each of the papers was presented at the Symposium and has undergone rigorous peer review. The papers represent a broad disciplinary scope within system analysis ranging from forest economics and management science to remote sensing. The problems addressed within these disciplines also vary, from wildfire mitigation, supply-chain optimization, bioenergy logistics, and participatory forest planning to fuel assessment. The technical tools the authors applied to these problems are equally diverse: game theory, dynamic programming, stochastic optimization, multiobjective decision theory, structure-from-motion, and airborne laser scanning.
    Print ISSN: 0015-749X
    Electronic ISSN: 1938-3738
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 6
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    Cover Page (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-11
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 7
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    Too Busy to Eat with the Kids? Parental Work and Children's Eating (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-11
    Description: Parents influence their children's eating behavior by providing access to certain types of food, creating enjoyable mealtimes and associations with food, and by role modeling. In this study we investigate the association between parental employment and parental time spent eating with their children. Using data from the 2001/02 German Time Budget Survey, we explore associations between time spent eating with children and labor force participation in Germany. We find that parental labor force participation is negatively associated with time spent eating with children. Each additional hour of work per day by the mother is associated with a 2.4 minute decrease in the amount of time the mother spends eating with her children. For paternal hours of work, we find that the more time a father spends working, the less time the child spends eating with the father or with both parents. Overall, we find evidence of mother inter-gender time substitution and some amount of time/food away from home substitution. Understanding how parents allocate their time, where they are most likely to eat, and what drives these decisions is an important endeavor since parents play a critical role in shaping and reinforcing their children's eating practices.
    Keywords: D13 - Household Production and Intrahousehold Allocation
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 8
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    Exploring the Role of Incentives in Agricultural Extension Programs (2015)
    Oxford University Press
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    Publication Date: 2015-08-11
    Description: While many governments subsidize extension programs, financial incentives for participation in extension programs are rare and little is known about such initiatives. This article assesses whether a financial incentive for an agricultural extension program for dairy farmers in Ireland has an impact on the type of farmer that participates in extension services. The findings reveal that financial incentives encourage participation, especially with cohorts of farmers that previously eschewed such programs. Several aspects of the overall economic effectiveness of the extension program are discussed and policy recommendations are outlined.
    Keywords: Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q16 - R&D ; Agricultural Technology ; Agricultural Extension Services
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 9
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    Trade Liberalization versus Climate Change Policy for Reducing Greenhouse Gas Emissions in Agriculture: Some Insights from Norway (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-11
    Description: Using a mathematical programming model of Norwegian agriculture, we explore interconnections between trade liberalization and reductions in greenhouse gas (GHG) emissions. We show that the Doha Round proposals for a new agreement on agriculture through the World Trade Organization would not generate significant reductions in emissions. Further trade liberalization would reduce emissions by cutting agricultural production but would not change production methods. Imposing a carbon tax would lead both to a reduction in output and the extensification of production. In contrast, if farmers are allowed to claim a credit for carbon sequestration the effect is to intensify agricultural production.
    Keywords: F18 - Trade and Environment, Q17 - Agriculture in International Trade, Q54 - Climate ; Natural Disasters ; Global Warming
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 10
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    A Wicked Problem? Cost Containment in the Women, Infants and Children Program (2015)
    Oxford University Press
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    Publication Date: 2015-08-11
    Description: The Special Supplemental Nutrition Program for Women, Infants and Children (WIC) Program is a key part of America's safety net, but its structure fails to incentivize participants to be cost-conscious in their purchases and may cause retailers to attach excessive markups to WIC products. We investigate cost containment in the WIC Program, with a focus on California. Results show that smaller vendors often charge considerably higher prices for WIC foods than their larger counterparts. However, larger vendors do not mark up WIC foods more or promote them less than comparable control products. Cost containment can be improved by targeting WIC Program sales to larger vendors when it is possible to do so without compromising participant access, and using large-vendor prices as a benchmark to limit prices set by smaller vendors.
    Keywords: D12 - Consumer Economics: Empirical Analysis, I38 - Government Policy ; Provision and Effects of Welfare Programs, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 11
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    Crop Prices, Agricultural Revenues, and the Rural Economy1 (2015)
    Oxford University Press
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    Publication Date: 2015-08-11
    Description: Policy makers in the United States often justify agricultural subsidies by stressing that agriculture is the engine of the rural economy. We use the increase in crop prices in the late 2000s to estimate the marginal effect of increased agricultural revenues on local economies in the U.S. Heartland. We find that $1 more in crop revenue generated 64¢ in personal income, with most going to farm proprietors and workers (59%) or nonfarmers who own farm assets (36%). The evidence suggests a weak link between revenues and nonfarm income or employment, or on population. Cuts to agricultural subsidies are therefore likely to have little effect on the broader rural economy in regions like the Heartland.
    Keywords: J43 - Agricultural Labor Markets, O13 - Agriculture ; Natural Resources ; Energy ; Environment ; Other Primary Products
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 12
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    A Chat about Insurance: Experimental Results from Rural Bangladesh (2015)
    Oxford University Press
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    Publication Date: 2015-08-11
    Description: Farmers throughout the developing world face multiple sources of uninsured risk to agricultural production and household assets. In this paper, we present results from an experimental demand-elicitation exercise in rural Bangladesh to shed light on smallholder farmers' interest in formal insurance products. We propose a suite of insurance and savings products, and we randomly vary the price of one insurance option (area-yield insurance) and the presence of one of the savings options (group savings). Consistent with economic theory, farmers buy more of the insurance products that cover the risks they primarily face. However, because farmers are subject to a variety of risks, they do not focus on only one type of insurance; instead, they evenly split their endowment between life and disability insurance and agricultural insurance. Demand for area-yield insurance falls with price; we also observe important cross-price elasticities with other insurance products. The presence of group savings does not alter demand for insurance, though group savings is found to be a particularly popular risk management tool, especially when decisions are made in groups.
    Keywords: C93 - Field Experiments, G22 - Insurance ; Insurance Companies, O13 - Agriculture ; Natural Resources ; Energy ; Environment ; Other Primary Products, O16 - Economic Development: Financial Markets ; Saving and Capital Investment ; Corporate Finance and, Q14 - Agricultural Finance
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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  • 13
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    Subscription Page (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-11
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 14
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    Revisiting the Supplemental Nutrition Assistance Program cycle of food intake: Investigating heterogeneity, diet quality, and a large boost in benefit amounts (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-11
    Description: The monthly cycle of daily food intake among adult participants in the Supplemental Nutrition Assistance Program is examined using data from the 2007–10 National Health and Nutrition Examination Survey. Exogenous variation in interview and benefit receipt dates provides means for identification, and a difference-in-differences specification is used to account for the large boost in benefits that began in April 2009 via the American Recovery and Reinvestment Act (ARRA). Caloric intake declined as much as 25% at the end of the month prior to ARRA, but not after implementation. Few differences were observed for diet quality measures or among subgroups. Increases in SNAP benefit amounts may help smooth food intake over the benefit month.
    Keywords: D12 - Consumer Economics: Empirical Analysis, E21 - Consumption ; Saving ; Wealth, I38 - Government Policy ; Provision and Effects of Welfare Programs
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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  • 15
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    Deception in Experiments: Towards Guidelines on use in Applied Economics Research (2015)
    Oxford University Press
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    Publication Date: 2015-08-11
    Description: Many applied economics journals ban the use of deception in experiments, which contrasts with the policies in other academic disciplines. We examine the cases for and against deception, and describe the ways deception can be employed in applied economics experiments. We create a general ranking of harms from deception in experiments and present evidence from a survey (conducted in summer 2014) of agricultural and applied economists eliciting attitudes towards ten different deceptive practices. Survey respondents view inflicting physical or psychological harm on participants and not making promised payments as the most severe forms of deception. Less severe forms of deception include providing participants with incomplete product information and conducting an experiment using participants who are not aware they are part of an experiment. Finally, we provide recommendations for policies addressing deception in experiments.
    Keywords: C80 - General, C81 - Methodology for Collecting, Estimating, and Organizing Microeconomic Data, C90 - General
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 16
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    Supply Response, Marginal Cost, and Soil Erosion Implications of Stover-based Biofuels (2015)
    Oxford University Press
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    Publication Date: 2015-08-11
    Description: Existing economic analysis of corn stover as an energy feedstock has not considered potential changes in land use associated with different stover prices. We estimate the response of corn stover supply density to its price driven by changes in land use and examine its implications for a processing plant's pricing strategy and marginal cost, as well as associated changes in soil erosion. We find that plants will exploit the intensive margin as well as the extensive margin to secure additional amounts of stover. Our results show, counterintuitively, that a market for stover may result in lower soil erosion due to reallocations of land to continuous corn with removal, which, combined with no-till farming, results in lower soil erosion than the baseline without stover removal. Also contrary to expectations, using cover crops with stover removal may result in higher soil erosion due to land use changes within the fuel shed associated with optimal pricing.
    Keywords: Q15 - Land Ownership and Tenure ; Land Reform ; Land Use ; Irrigation, Q24 - Land, Q42 - Alternative Energy Sources
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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  • 17
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    Calculations of effectiveness factors and the criteria of mass transfer effect for high-temperature methanation (HTM) catalyst (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: Natural gas is an extremely important bridge fuel to a low-carbon energy economy for improving local air quality. Coal to synthetic natural gas (SNG) is an effective way to convert the high-carbon energy (coal) into the low-carbon energy with rich hydrogen (natural gas). For the modern coal to SNG industry, the high-temperature methanation (HTM) catalyst plays an important role, and the advanced evaluation process should necessitate the elimination of mass transfer effect. Some simple but effective model catalysts, such as slab and sphere, can be very helpful in defining the reaction conditions, and thus facilitating the evaluation process for real HTM catalysts. In this work, slab and sphere model catalysts were adopted to derive mass transfer and reaction-coupled equations, the numerical methods were used to solve the coupled equations for the concentration profiles in catalysts, and the effectiveness factors were accordingly calculated. By taking advantage of the Thiele module and the Weisz–Prater module , the criteria for the elimination of mass transfer effect in the HTM catalyst evaluation process were successfully defined. This work also complements the Weisz–Prater criterion by incorporating ‘negative reaction orders’.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 18
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    A novel low-carbon space conditioning system incorporating phase-change materials and earth-air heat exchangers (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The energy expended for conditioning buildings around the world is worryingly large and increasing every year. Currently, almost half of houses around the world use some type of energy-expensive conventional air-conditioning system. These systems are high emitters of gases such as carbon dioxide and so high contributors to climate change. Consequently, alternatives must be considered. Earth–air heat exchangers (EAHEs) and phase-change materials (PCMs) may be options; they have, however, limitations. This paper proposes a novel hybrid space-conditioning system combining EAHEs with PCMs, which uses surfaces as sources of heating or cooling to provide better temperature distribution across a space and comfort enhancement with low energy use. The idea is to use an EAHE to provide cool air to discharge the PCM, consequently helping to overcome most of the limitations of both strategies. Two of a series of experiments undertaken to test the proposed system are reported in this article. The EAHE + PCM system compared with a reference room could decrease temperature swings by up to 47%. The system was proved to work although further work is required to make it commercially viable.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 19
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    3D analysis of the incident diffuse irradiance on the building's surfaces in an urban environment (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The design of a future building with very high-energy efficiency demands from the architect to study the available solar resources in this urban environment. The purpose of the presented methodology is to study the variations in all components of the incident solar radiation daily, monthly and seasonally for all building facades. This is realized in the computer program 3D–SOLARIA. In the focus of the paper is the estimation of the background component of the incident diffuse solar irradiation on a building facade under orthogonally obstructed sky, using anisotropic sky view factors.
    Keywords: Sustainable/low carbon buildings
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 20
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    An integrated approach for sustainable design and assessment of residential building envelope: part I (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The assessment of building envelope sustainability using existing building performance assessment methods is still a challenge and yet to be fully addressed. This is due to the single-dimensional nature and lack of integration of sustainable performance values. Besides, the issue of sustainability assessment in the building envelope requires considering many factors including life cycle considerations. As such, in an effort to develop an integrated approach that combines relevant sustainable development factors and life cycles, an integrated performance model (IPM) was developed. The IPM is an essential tool developed to aid the sustainable design of the residential building envelope that can reduce carbon emission and whole residential building energy consumption and ensure sustainable performance of the building envelope.
    Keywords: Sustainable/low carbon buildings
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 21
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    Towards the generation of distributed electric power: self-consumption with net balance (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The results and considerations on one self-consumption photovoltaic installation with net balance in Granada (South of Spain) are presented and discussed in this paper. The use of the building (one faculty) makes it optimal for this kind of consumption. Finally, the potential benefits and problems of self-consumption with net balance are presented.
    Keywords: Solar energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 22
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    Numerical investigation of turbulent flow heat transfer and pressure drop of AL2O3/water nanofluid in helically coiled tubes (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: Passive convective heat transfer enhancement can be achieved by improving the thermo-physical properties of the working fluid, changing flow geometry or both. This work presents a numerical study to investigate the combined effect of using helical coils and nanofluids on the heat transfer characteristics and pressure losses in turbulent flow regime. The developed computational fluid dynamics models were validated against published experimental data and empirical correlations. Results have shown that combining the effects of alumina (Al 2 O 3 ) nanoparticles and tube coiling could enhance the heat transfer coefficient by up to 60% compared with that of pure water in straight tube at the same Reynolds number. Also, results showed that the pressure drop in helical coils using Al 2 O 3 nanofluid for volume fraction of 3% was six times that of water in straight tubes (80% of the pressure drop increase is due to nanoparticles addition), while the effect of Reynolds number on the pressure drop penalty factor was found to be insignificant.
    Keywords: Other low-carbon energy technologies
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 23
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    Control strategies for indoor environment quality and energy efficiency--a review (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The demand for better indoor environment has led to a wide use of heating, ventilating and air conditioning (HVAC) systems. However, this demanding cannot be sustained without a strategy to reduce the energy consumption of HVAC systems. Employing advanced HVAC control is one of the strategies to maintain high-quality indoor thermal comfort with low energy consumption. This paper reviews the development of control technologies for HVAC systems. It summarizes the problems in existing reviews and gives a future perspective on HVAC control systems for occupant comfort and energy efficiency.
    Keywords: Built environment and low-carbon society
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 24
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    Long-term stand dynamics of managed spruce-fir-beech mountain forests in Central Europe: structure, productivity and regeneration success (2015)
    Oxford University Press
    In: Forestry
    Details
    Publication Date: 2015-08-07
    Description: With a total area of several million hectares, mountain forests of Norway spruce ( Picea abies (L.) Karst.), silver fir ( Abies alba Mill.) and European beech ( Fagus sylvatica L.) connect the beech-covered lowlands and spruce-dominated alpine regions and still represent the most natural though managed forests in Europe. For sustaining their unique functions and services, their natural gap dynamics are emulated by the combined shelterwood–femel-coupe system. In the 1970s, 22 long-term experimental plots were established in the Bavarian Alps in order to substantiate the formerly mainly experience-based silvicultural prescriptions. After more than 40 years of successive surveys including the integrated evaluation of the old stands and the measurement of natural regeneration, analyses reveal: (1) The reduction of overstorey density is generally associated with a proportional reduction of the overstorey stand growth. So, the recommended 20–40 per cent density reduction of a combined shelterwood–femel coupe may reduce the mean annual increment also by ~20–40 per cent, but part of this loss is compensated by the additional growth of the regeneration. (2) Over time, the natural regeneration is continuously augmented by new recruitment of seedlings and saplings. (3) However, even 40 years after initiating regeneration, spruce is rare in the regeneration compared with fir, beech and other broadleaved species. Further observation will show whether spruce will catch up with the other species or whether it requires either larger disturbances than gap and femel coupes, or possibly planting. Based on these findings, a refined shelterwood–femel-coupe system is proposed and its advantages and disadvantages are discussed.
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    Tracer gas technique for measurement of air infiltration and natural ventilation: case studies and new devices for measurement of mechanical air ventilation in ducts (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-16
    Description: In buildings without mechanical ventilation, the fresh air needed by the occupants is supplied only by air infiltration or natural ventilation. Its quantification by analytical methods is difficult, and so experimental methods such as the tracer gas technique are very useful. In this work, several case studies are presented, where one may see the potential of this technique to detect small differences in building air tightness, due to different envelope elements, namely the type of window frames and location of blinds' boxes. The applicability of this technique to other spaces rather than buildings can also be analyzed. When dealing with mechanical ventilation, it is difficult to measure the duct air flow rate precisely, because of the minimum duct length necessary to obtain a good mixing of the tracer gas with the air, when conventional probes are used. Research was carried out with the development of new probes to overcome this situation, and results are also shown. With accurate measurements of air flow rates, it is possible to reduce CO 2 emissions due to air heating or cooling in buildings.
    Keywords: Built environment and low-carbon society
    Print ISSN: 1748-1317
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    Readdressing working fluid selection with a view to designing a variable geometry ejector (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-16
    Description: A number of factors influence the performance of an ejector, e.g. working fluid, geometry and operating conditions. In the present work, six low-environmental-impact working fluids were evaluated for their use in an ejector cooling system running on low-temperature thermal energy. The numerical analysis was based on a model applying the 1D constant-pressure mixing theory. Ejector performance was assessed for the temperatures of the generator, evaporator and condenser in the range of 80–120°C, 5–15°C and 25–40°C, respectively. The results indicated that owing to its high coefficient of performance and moderate operating pressures throughout the entire ejector cycle, isobutane is a good choice for a refrigerant. The area ratio required for running the ejector in critical mode, under changing operating conditions, varied in a significant range regardless of the selected refrigerant. This clearly indicates the importance of a variable geometry ejector design to strengthen the position of ejector cooling systems among other refrigeration technologies.
    Keywords: Other low-carbon energy technologies
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    Effect of three partial cutting practices on stand structure and growth of residual black spruce trees in north-eastern Quebec (2015)
    Oxford University Press
    In: Forestry
    Details
    Publication Date: 2015-08-07
    Description: Partial cutting practices are increasingly used in boreal forests for two major reasons: (1) maintaining age structure and tree diameter distribution according to the principles of ecosystem-based management and (2) increasing tree growth by decreasing competition. This study evaluated the effects of three different partial cutting treatments applied to even- and uneven-aged black spruce ( Picea mariana (Mill.) B.S.P.) stands in north-eastern Quebec, Canada. The effect of partial cutting was assessed by comparing treated and control plots in terms of age structure, diameter and spatial distribution, amount of deadwood and tree radial growth. Age structure and diameter distribution were not different from control plots after partial cuttings applied in both uneven-aged and even-aged stands, but lower deadwood basal area was observed. Tree radial growth generally increased in uneven-aged stands but can be limited by tree age and inter-tree competition. In even-aged stands, tree removal was more uniformly distributed and the overall reduction in inter-tree competition resulted in an increased tree radial growth. Overall, these results suggest that the studied partial cuttings were adequate for maintaining structural attributes and increasing tree growth, but adjustments should be made to treatments to increase the amount of deadwood to a level observed in natural forests and to lower inter-tree competition.
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    Effects of intensity of forest regeneration measures on stand development in a nationwide Swedish field experiment (2015)
    Oxford University Press
    In: Forestry
    Details
    Publication Date: 2015-08-07
    Description: The general belief that intense regeneration measures are financially viable and essential for high sustained yields of commercial forest products has been inadequately tested. This field experiment evaluates effects of three different regeneration intensities 24–27 years after clear-cutting of 14 sites across Sweden. The treatments, designated high (HI), normal (NI) and low (LI), respectively, consisted of: mechanical site preparation and planting of large seedlings at 2 x 2 m spacing, with supplemental planting and pre-commercial thinning (PCT) when deemed necessary; standard local practices; and natural regeneration with no site preparation, artificial regeneration or PCT. Average crop seedling densities were highest and lowest (3359 and 1662 ha –1 ) under the HI and LI treatments, respectively, 4–8 growing seasons after planting. After 24–27 years, HI also resulted in higher mean stem volume (90 m 3 ha –1 ) than LI (36 m 3 ha –1 ) but was not significantly different from NI (65 m 3 ha –1 ) and increasing the regeneration intensity was not consistently positive. In some cases, high planted seedling mortality and generally abundant natural regeneration resulted in minor (or no) differences between the treatments. The results illustrate that current Swedish regeneration standards may need revision in order to reflect contemporary societal and commercial demands.
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    Seasonal variability of foliar photosynthetic and morphological traits and drought impacts in a Mediterranean mixed forest (2015)
    Oxford University Press
    Details
    Publication Date: 2015-06-04
    Description: The Mediterranean region is a hot spot of climate change vulnerable to increased droughts and heat waves. Scaling carbon fluxes from leaf to landscape levels is particularly challenging under drought conditions. We aimed to improve the mechanistic understanding of the seasonal acclimation of photosynthesis and morphology in sunlit and shaded leaves of four Mediterranean trees ( Quercus ilex L., Pinus halepensis Mill., Arbutus unedo L. and Quercus pubescens Willd.) under natural conditions. V c,max and J max were not constant, and mesophyll conductance was not infinite, as assumed in most terrestrial biosphere models, but varied significantly between seasons, tree species and leaf position. Favourable conditions in winter led to photosynthetic recovery and growth in the evergreens. Under moderate drought, adjustments in the photo/biochemistry and stomatal/mesophyllic diffusion behaviour effectively protected the photosynthetic machineries. Severe drought, however, induced early leaf senescence mostly in A. unedo and Q. pubescens , and significantly increased leaf mass per area in Q. ilex and P. halepensis . Shaded leaves had lower photosynthetic potentials but cushioned negative effects during stress periods. Species-specificity, seasonal variations and leaf position are key factors to explain vegetation responses to abiotic stress and hold great potential to reduce uncertainties in terrestrial biosphere models especially under drought conditions.
    Print ISSN: 0829-318X
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    Mechanisms of induced susceptibility to Diplodia tip blight in drought-stressed Austrian pine (2015)
    Oxford University Press
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    Publication Date: 2015-06-04
    Description: Plants experiencing drought stress are frequently more susceptible to pathogens, likely via alterations in physiology that create favorable conditions for pathogens. Common plant responses to drought include the production of reactive oxygen species (ROS) and the accumulation of free amino acids (AAs), particularly proline. These same phenomena also frequently occur during pathogenic attack. Therefore, drought-induced perturbations in AA and ROS metabolism could potentially contribute to the observed enhanced susceptibility. Furthermore, nitrogen (N) availability can influence AA accumulation and affect plant resistance, but its contributions to drought-induced susceptibility are largely unexplored. Here we show that drought induces accumulation of hydrogen peroxide (H 2 O 2 ) in Austrian pine ( Pinus nigra Arnold) shoots, but that shoot infection by the blight and canker pathogen Diplodia sapinea (Fr.) Fuckel leads to large reductions in H 2 O 2 levels in droughted plants. In in vitro assays, H 2 O 2 was toxic to D. sapinea , and the fungus responded to this oxidative stress by increasing catalase and peroxidase activities, resulting in substantial H 2 O 2 degradation. Proline increased in response to drought and infection when examined independently, but unlike all other AAs, proline further increased in infected shoots of droughted trees. In the same tissues, the proline precursor, glutamate, decreased significantly. Proline was found to protect D. sapinea from H 2 O 2 damage, while also serving as a preferred N source in vitro. Fertilization increased constitutive and drought-induced levels of some AAs, but did not affect plant resistance. A new model integrating interactions of proline and H 2 O 2 metabolism with drought and fungal infection of plants is proposed.
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    Heterogeneity of competition at decameter scale: patches of high canopy leaf area in a shade-intolerant larch stand transpire less yet are more sensitive to drought (2015)
    Oxford University Press
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    Publication Date: 2015-06-04
    Description: Small differences in the sensitivity of stomatal conductance to light intensity on leaf surfaces may lead to large differences in total canopy transpiration ( E C ) with increasing canopy leaf area ( L ). Typically, the increase of L would more than compensate for the decrease of transpiration per unit of leaf area ( E L ), resulting in concurrent increase of E C . However, highly shade-intolerant species, such as Larix principis-rupprechtii Mayr., may be so sensitive to increased shading that such compensation is not complete. We hypothesized that in such a stand, windfall-induced spatial variation at a decameter scale would result in greatly reduced E L in patches of high L leading to lower E C than low competition patches of sparse canopy. We further hypothesized that quicker extraction of soil moisture in patches of lower competition will result in earlier onset of drought symptoms in these patches. Thus, patches of low L will transition from light to soil moisture as the factor dominating E L . This process should progressively homogenize E C in the stand even as the variation of soil moisture is increasing. We tested the hypotheses utilizing sap flux of nine trees, and associated environmental and stand variables. The results were consistent with only some of the expectations. Under non-limiting soil moisture, E L was very sensitive to the spatial variation of L , decreasing sharply with increasing L and associated decrease of mean light intensity on leaf surfaces. Thus, under the conditions of ample soil moisture maximum E C decreased with increasing patch-scale L . Annual E C and biomass production also decreased with L , albeit more weakly. Furthermore, variation of E C among patches decreased as average stand soil moisture declined between rain events. However, contrary to expectation, high L plots which transpired less showed a greater E L sensitivity to decreasing stand-scale soil moisture, suggesting a different mechanism than simple control by decreasing soil moisture. We offer potential explanations to the observed phenomenon. Our results demonstrate that spatial variation of L at decameter scale, even within relatively homogeneous, single-species, even-aged stands, can produce large variation of transpiration, soil moisture and biomass production and should be considered in 1-D soil–plant–atmosphere models.
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    Extraction and estimation of the quantity of calcium oxalate crystals in the foliage of conifer and hardwood trees (2015)
    Oxford University Press
    Details
    Publication Date: 2015-06-04
    Description: The main goal of this study was to develop a method for the extraction and indirect estimation of the quantity of calcium oxalate (CaOx) in the foliage of trees. Foliar tissue was collected from a single tree of each species (five conifers and five hardwoods) for comparison of extractions in different solvents using 10 replicates per species from the same pool of tissue. For each species, calcium (Ca) and oxalate were extracted sequentially in double deionized water and 2N acetic acid, and finally, five replicate samples were extracted in 5% (0.83N) perchloric acid (PCA) and the other five in 2N hydrochloric acid (HCl); three cycles of freezing and thawing were used for each solvent. Total ions were extracted by microwave digestion. Calcium was quantified with an inductively coupled plasma emission spectrophotometer method and oxalate was eluted and quantified using a high performance liquid chromatography method. This experiment was repeated again with two conifer and two hardwood species using four trees per species, and two analytical replicates for each tree. We report here that, regardless of age of individual trees within a species, time of collection or species type, the third extraction in PCA or HCl resulted in near equimolar quantities of Ca and oxalate ( r 2  ≥ 0.99). This method provides an easy estimate of the quantity of CaOx crystals using a small sample of foliar tissue. An additional benefit of PCA is that it precipitates the nucleic acids and proteins, allowing the quantification of several free/soluble metabolites such as amino acids, polyamines, organic acids and inorganic elements all from a single sample extract.
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    Beyond physical health and safety: supporting the wellbeing of workers employed in the forest industry (2015)
    Oxford University Press
    In: Forestry
    Details
    Publication Date: 2015-08-07
    Description: A healthy, productive and resilient workforce is important to any industry, and supporting the wellbeing of workers is a key factor in achieving this. Worldwide, the forest industry is amongst the most physically dangerous industries to work in. Workplace health and safety strategies have traditionally focused on improving the physical safety of forestry workplaces. It is equally important to consider the broader wellbeing of workers, not only to ensure their quality of life, but also to support a healthy and sustainable workforce with low turnover. To do this, it is critical to understand the work-related factors that affect worker wellbeing. We examine this via a survey of workers in the Australian forest industry. We find that work-related factors known to influence wellbeing in other industries, such as income, job security and workplace culture, are strongly correlated with forest worker wellbeing, that negative perceptions of the forest industry by those outside it are associated with lower levels of worker wellbeing and that the extent to which a forest industry worker has a strong work-related social identity is associated with their wellbeing. Our findings highlight the importance of implementing workplace strategies that consider wellbeing in broader terms than the traditional focus on physical safety.
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    Preventive control of Botryosphaeria canker affecting Quercus suber in southern Spain (2015)
    Oxford University Press
    In: Forestry
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    Publication Date: 2015-08-07
    Description: Botryosphaeria canker is likely the most injurious disease for cork production in the Mediterranean Basin. The exclusion of Benomyl, the standard commercial product used to prevent Botryosphaeria canker, from the EU Pesticide Database in 2003 necessitates the search for new alternatives to prevent cork oak cankering. In vitro experiments showed that every fungicide tested at 10 3 mg l –1 active ingredient was effective in reducing mycelial growth of Diplodia corticola . An initial field experiment showed that cork oak trunks sprayed with Thiophanate-methyl, Carbendazim, Difenoconazole, Pyraclostrobin or Copper-Calcium Sulphate under low-humidity environmental conditions exhibited significant decreases in the number and length of trunk lesions, 3 years post-treatment, compared with untreated trees. A second field experiment conducted under extremely wet conditions showed that only Thiophanate-methyl was effective, 2.5 years after treatments, when sprayed just after peeling. Finally, in a third field experiment, under wet conditions, the preventive effectiveness of Thiophanate-methyl, Copper-Calcium Sulphate and a mix of both fungicides was confirmed, although no synergistic effect of the mixture was measured. Copper-Calcium Sulphate or Thiophanate-methyl, when applied immediately after trunk peeling, is effective for preventive control of Botryosphaeria canker on cork oak and may be considered as an effective replacement for Benomyl.
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    Constructal optimization of a disc-shaped body with cooling channels for specified power pumping (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The thermal performance of a disc-shaped heat generation body with cooling channels is investigated by using constructal theory based on previous model of heat convection on a disc and previous analytical method of heat conduction on a disc. By taking minimum dimensionless maximum thermal resistance as optimization objective, the optimal aspect ratio of the elemental sector in the radial-pattern disc is obtained for the specified power pumping of the elemental sector; the optimal width ratio of the first-order and elemental cooling channels and the optimal dimensionless radius of the elemental sector are obtained for the specified power pumping of the disc. There exists a critical radius of the disc to determine whether the radial-pattern design and branched-pattern design should be adopted. These conclusions are different from those obtained by Wechsatol et al. 's model, and the essential reason for these differences is that the power pumping is specified in this article, but not the specified flow rate number in Wechsatol et al. 's model. Finally, the assumption about the heat capacity of the coolant and the thermal conductivity of the disc is validated. An analytical method is introduced in this article, which can provide another thought for the constructal optimization of disc with heat convection. The optimal constructs of the discs are obtained for the specified power pumping, which provides some different guidelines for the design of disc with heat convection.
    Keywords: Other low-carbon energy technologies
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    Theoretical investigation of hot box solar cookers having conventional and finned absorber plates (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: In this paper, solar box cookers with ordinary and finned absorber plates are theoretically investigated in terms of thermodynamic performance parameters. For a typical summer and winter day, temperatures of solar cooker components such as glass cover, internal air, absorber plate, cooking vessel and the liquid are determined theoretically versus time. The analysis is carried out for conventional and finned absorber plates, and accuracy of the results is verified by a previously published experimental work. Energy and exergy efficiencies of box-type solar cookers are plotted versus time for various cases. The methodology presented in this paper enables to make a preliminary evaluation of ordinary and modified solar box cookers with respect to changes in main environmental parameters such as temperature and illumination intensity. Some recommendations are also made to enhance the power outputs of the aforementioned solar cookers.
    Keywords: Solar energy technologies
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    Design of a celestial vault image capture device for its application in the solar radiation field (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: The sun is the more plentiful source of natural power that we have in the Earth. However, the amount of radiation reaching the Earth's surface depends on astronomical and climatic factors. One of the factors exerting a greater influence is cloudiness. For that reason, it is important to quantify its influence on solar radiation. According to that, in this work, a prototype to capture images of the celestial vault is designed and implemented to be able to measure parameters related to the cloud properties and, later, to determine their influence on solar radiation.
    Keywords: Solar energy technologies
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    Investigation of concentrating and nonconcentrating evacuated tube solar water heaters using 2D particle imaging velocimetry (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: Under transient climatic conditions, solar water heaters using heat pipes are more effective at capturing incident solar radiation than other equivalent sized solar water heaters. The cost must be reduced to improve uptake of such systems. To investigate two methods were considered by this study: thermosyphon fluid flow and reflective concentrators. A physical reconfigurable laboratory model of the manifold and associated condensers of a heat-pipe-evacuated tube system were fabricated; fluid circulation was via thermosyphonic action, particle imaging velocimetry derived velocity maps and the use of concentrators was simulated. When condenser spacing was doubled, the Nusselt number increased by 43%, the velocity by 55% but the heat transfer efficiency of the model manifold decreased by 9%. Potential annual energy savings of 10 207 GWh could be realized if such systems could be successfully fabricated.
    Keywords: Solar energy technologies
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    The impact of surface characteristics on ambient temperature at urban micro scale: comparative field study in two climates (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: This paper presents the results of two field studies to examine the differences in ambient temperatures in a micro-scale environment (at distances of 50–200 m between measuring points) in two different climates during typical summer weather conditions at two similar sites in terms of construction and activities. The analysis considered the land use around the measuring locations split into three categories (built, green and open) as well as climatic conditions and studied the effect of these on ambient temperature at each measuring location. It was found that, similarly to macro-scale studies at the urban level, measuring locations with a higher green cover have a lower ambient temperature compared with measuring locations with a higher built and/or open land cover. The results provide measured evidence in two different climates that small green areas distributed within the urban environment can provide a reduction in the ambient temperature thus contributing to the mitigation of urban heat island.
    Keywords: Built environment and low-carbon society
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    Computational study of a 2D capillary pump evaporator (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: Capillary pump loop (CPL) is a two-phase heat transfer device considered as a useful solution for thermal control applications in spacecrafts, satellites and electronic components. The purpose of this paper is to study various aspects of the working state of the CPL evaporator. A two-dimensional computational model was developed in order to analyze the flow and the phase transformation inside a cylindrical evaporator. At the present analysis, different cases were studied by changing liquid saturation temperature, inclination angle of the evaporator and the length of the porous heated wick. Water, ammonia, acetone and freon-134 were used as working liquids for numerical experiments. Results present the evaporator capability to vaporize each working liquid and find out its possibility of dry-out causing failure. This information is useful in choosing the best working liquid for an evaporator, enabling bigger amounts of heat to be transferred.
    Keywords: Other low-carbon energy technologies
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    Failure of natural ventilation strategy in a sustainable house in China (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: In recent years, the concept of green building is becoming popular in China. Architects and engineers have the opportunity to actually implement green building practices. This paper reveals the failure of a naturally ventilated LEED-certified townhouse development project in China mentioned in recent research. The house owners made great alterations for the purpose of decoration, which removed or minimized the effectiveness of natural ventilation elements in the original design. The research shows that the houses show ‘International Style’ because the natural ventilation design principles were not fully applied in the design and the localized natural ventilation strategies were not fully considered by means of computational simulation in the design stage. Also, the lack of communication between designers and the owners caused the removal of most natural ventilation elements of these houses during the occupancy period. The authors advocate three criteria to avoid failures of natural ventilation design: localized/ climate adaptive design, relationship among design elements and design intention awareness.
    Keywords: Sustainable/low carbon buildings
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    Design guideline for application of earth-to-air heat exchanger coupled with solar chimney as a natural heating system (2015)
    Oxford University Press
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    Publication Date: 2015-08-16
    Description: In the present paper, design of solar chimney (SC) and earth-to-air heat exchanger (EAHE) to meet the thermal need of flat buildings are studied regarding adaptive thermal comfort criteria. Investigation on the effects of geometric features shows that the design of SC with the air gap and outlet sizes of 0.2 m and also EAHE with the diameter and length of 0.5 and 25.0 m reveals better performance. Thermal comfort analysis shows that the SC is capable to power the underground heating system during few hours of the sunny days even at the ambient temperature as low as 0°C and the heating demand of 1000 W without needing the auxiliary devices. In addition, the required numbers of SCs and the underground air channels are strongly influenced by environmental outdoor conditions and heating demand of building and are approximately calculated by: $$\hbox{ room }\phantom{\rule{0.08em}{0ex}}\hbox{ volume/50 }\phantom{\rule{0.08em}{0ex}}\hbox{ and }\phantom{\rule{0.08em}{0ex}}\hbox{ 2 }\times (\hbox{ room }\phantom{\rule{0.08em}{0ex}}\hbox{ volume/50 })+\hbox{ 1, }$$ respectively.
    Keywords: Other low-carbon energy technologies
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    Adaptive facade design for the daylighting performance in an office building: the investigation of an opening design strategy with cellular automata (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-16
    Description: Daylighting has an important role in sustainable architecture as it affects the energy consumption in a building. Especially for an office building, daylight helps not only to reduce the load on artificial lighting but also to promote work efficiency through promoting good human health, well-being and user comfort. The objective of this research is to develop an innovative façade design strategy that comes from the development of digital technology and dynamic daylight performance measuring methods. Thus, the various parameters are studied through the computational process of cellular automata (CA) to generate the several alternative opening patterns on the building façade. Each CA design value was tested under static and dynamic sky condition to analyze the quality and quantity of daylight and visual comfort throughout the year. The results were compared to find an optimum alternative design in terms of the daylighting design criteria, from building code, standard and design guidelines for the office building. Finally, research of an adaptive façade design strategy was concluded with the results from the above hybridization of generative and performative design methodology. This study discovers the architectural design approach from the CA and it will make not only progress in building façade esthetics, but also human comfort with building sustainability.
    Keywords: Sustainable/low carbon buildings
    Print ISSN: 1748-1317
    Electronic ISSN: 1748-1325
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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    Transcriptional responses of Norway spruce (Picea abies) inner sapwood against Heterobasidion parviporum (2015)
    Oxford University Press
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    Publication Date: 2015-09-25
    Description: The white-rot fungus Heterobasidion parviporum Niemelä & Korhonen establishes a necrotrophic interaction with Norway spruce ( Picea abies (L.) H.Karst.) causing root and butt rot and growth losses in living trees. The interaction occurs first with the bark and the outer sapwood, as the pathogen enters the tree via wounds or root-to-root contacts. Later, when the fungus reaches the heartwood, it spreads therein creating a decay column, and the interaction mainly occurs in the inner sapwood where the tree creates a reaction zone. While bark and outer sapwood interactions are well studied, little is known about the nature of the transcriptional responses leading to the creation of a reaction zone. In this study, we sampled bark and sapwood both proximal and distal to the reaction zone in artificially inoculated and naturally infected trees. We quantified gene expression levels of candidate genes in secondary metabolite, hormone biosynthesis and signalling pathways using quantitative polymerase chain reaction. An up-regulation of mainly the phenylpropanoid pathway and jasmonic acid biosynthesis was found at the inoculation site, when inoculations were compared with wounding. We found that transcriptional responses in inner sapwood were similar to those reported upon infection through the bark. Our data suggest that the defence mechanism is induced due to direct fungal contact irrespective of the tissue type. Understanding the nature of these interactions is important when considering tree breeding-based resistance strategies to reduce the spread of the pathogen between and within trees.
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 45
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    Does reduced precipitation trigger physiological and morphological drought adaptations in European beech (Fagus sylvatica L.)? Comparing provenances across a precipitation gradient (2015)
    Oxford University Press
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    Publication Date: 2015-09-25
    Description: Global warming and associated decreases in summer rainfall may threaten tree vitality and forest productivity in many regions of the temperate zone in the future. One option for forestry to reduce the risk of failure is to plant genotypes which combine high productivity with drought tolerance. Growth experiments with provenances from different climates indicate that drought exposure can trigger adaptive drought responses in temperate trees, but it is not well known whether and to what extent regional precipitation reduction can increase the drought resistance of a species. We conducted a common garden growth experiment with five European beech ( Fagus sylvatica L.) populations from a limited region with pronounced precipitation heterogeneity (816–544 mm year –1 ), where phylogenetically related provenances grew under small to large water deficits. We grew saplings of the five provenances at four soil moisture levels (dry to moist) and measured ~30 morphological (leaf and root properties, root : shoot ratio), physiological (leaf water status parameters, leaf conductance) and growth-related traits (above- and belowground productivity) with the aim to examine provenance differences in the drought response of morphological and physiological traits and to relate the responsiveness to precipitation at origin. Physiological traits were more strongly influenced by provenance (one-third of the studied traits), while structural traits were primarily affected by water availability in the experiment (two-thirds of the traits). The modulus of leaf tissue elasticity reached much higher values late in summer in plants from moist origins resulting in more rapid turgor loss and a higher risk of hydraulic failure upon drought. While experimental water shortage affected the majority of morphological and productivity-related traits in the five provenances, most parameters related to leaf water status were insensitive to water shortage. Thus, plant morphology, and root growth in particular, did respond to reduced water availability with higher phenotypic plasticity than did physiology. We conclude that beech provenances exposed to different precipitation regimes have developed some genotypic differences with respect to leaf water status regulation, but these adaptations are associated with only minor adaptation in plant morphology and they do not affect the growth rate of the saplings.
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    Vegetation-zonation patterns across a temperate mountain cloud forest ecotone are not explained by variation in hydraulic functioning or water relations (2015)
    Oxford University Press
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    Publication Date: 2015-09-25
    Description: Many studies have demonstrated linkages between the occurrence of fog and ecophysiological functioning in cloud forests, but few have investigated hydraulic functioning as a determining factor that explains sharp changes in vegetation. The objective of this study was to compare the plant water status during cloud-immersed and non-immersed conditions and hydraulic vulnerability in branches and roots of species across a temperate, mountain fog ecotone. Because cloud forests are often dark, cool and very moist, we expected cloud forest species to have less drought-tolerant characteristics (i.e., lower P e and P 50 —the pressures required to induce a 12 and 50% loss in hydraulic conductivity, respectively) relative to non-cloud forest species in adjacent (lower elevation) forests. Additionally, due to the ability of cloud forest species to absorb cloud-fog water, we predicted greater improvements in hydraulic functioning during fog in cloud forest species relative to non-cloud forest species. Across the cloud forest ecotone, most species measured were very resistant to losses in conductivity with branch P 50 values from –4.5 to –6.0 MPa, hydraulic safety margins ( min – P 50 ) 〉1.5 MPa and low calculated hydraulic conductivity losses. Roots had greater vulnerabilities, with P 50 values ranging from –1.4 to –2.5 MPa, leading to greater predicted losses in conductivity (~20%). Calculated values suggested strong losses of midday leaf hydraulic conductance in three of the four species, supporting the hydraulic segmentation hypothesis. In both cloud forest and hardwood species, s were greater on foggy days than sunny days, demonstrating the importance of fog periods to plant water balance across fog regimes. Thus, frequent fog did not result in systemic changes in hydraulic functioning or vulnerability to embolism across our temperate cloud forest ecotone. Finally, roots functioned with lower hydraulic conductivity than branches, suggesting that they may serve as more sensitive indicators of hydraulic functioning in these mesic, foggy ecosystems.
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    Volatile organic compounds emitted from silver birch of different provenances across a latitudinal gradient in Finland (2015)
    Oxford University Press
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    Publication Date: 2015-09-25
    Description: Climate warming is having an impact on distribution, acclimation and defence capability of plants. We compared the emission rate and composition of volatile organic compounds (VOCs) from silver birch ( Betula pendula (Roth)) provenances along a latitudinal gradient in a common garden experiment over the years 2012 and 2013. Micropropagated silver birch saplings from three provenances were acquired along a gradient of 7° latitude and planted at central (Joensuu 62°N) and northern (Kolari 67°N) sites. We collected VOCs emitted by shoots and assessed levels of herbivore damage of three genotypes of each provenance on three occasions at the central site and four occasions at the northern site. In 2012, trees of all provenances growing at the central site had higher total VOC emission rates than the same provenances growing at the northern site; in 2013 the reverse was true, thus indicating a variable effect of latitude. Trees of the southern provenance had lower VOC emission rates than trees of the central and northern provenances during both sampling years. However, northward or southward translocation itself had no significant effect on the total VOC emission rates, and no clear effect on insect herbivore damage. When VOC blend composition was studied, trees of all provenances usually emitted more green leaf volatiles at the northern site and more sesquiterpenes at the central site. The monoterpene composition of emissions from trees of the central provenance was distinct from that of the other provenances. In summary, provenance translocation did not have a clear effect in the short-term on VOC emissions and herbivory was not usually intense at the lower latitude. Our data did not support the hypothesis that trees growing at lower latitudes would experience more intense herbivory, and therefore allocate resources to chemical defence in the form of inducible VOC emissions.
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    High rates of virus-induced gene silencing by tobacco rattle virus in Populus (2015)
    Oxford University Press
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    Publication Date: 2015-09-25
    Description: Virus-induced gene silencing (VIGS) has been shown to be an effective tool for investigating gene functions in herbaceous plant species, but has rarely been tested in trees. The establishment of a fast and reliable transformation system is especially important for woody plants, many of which are recalcitrant to transformation. In this study, we established a tobacco rattle virus (TRV)-based VIGS system for two Populus species, Populus euphratica and P.   x   canescens . Here, TRV constructs carrying a 266 bp or a 558 bp fragment of the phytoene desaturase (PDS) gene were Agrobacterium -infiltrated into leaves of the two poplar species. Agrobacterium -mediated delivery of the shorter insert, TRV2 -PePDS 266 , into the host poplars resulted in expected photobleaching in both tree species, but not the longer insert, PePDS 558 . The efficiency of VIGS was temperature-dependent, increasing by raising the temperature from 18 to 28 °C. The optimized TRV–VIGS system at 28 °C resulted in a high silencing frequency and efficiency up to 65–73 and 83–94%, respectively, in the two tested poplars. Moreover, syringe inoculation of Agrobacterium in 100 mM acetosyringone induced a more efficient silencing in the two poplar species, compared with other agroinfiltration methods, e.g., direct injection, misting and agrodrench. There were plant species-related differences in the response to VIGS because the photobleaching symptoms were more severe in P.   x   canescens than in P. euphratica. Furthermore, VIGS-treated P. euphratica exhibited a higher recovery rate (50%) after several weeks of the virus infection, compared with TRV-infected P.   x   canescens plants (20%). Expression stability of reference genes was screened to assess the relative abundance of PePDS mRNA in VIGS-treated P. euphratica and P.   x   canescens. PeACT7 was stably expressed in P. euphratica and UBQ-L was selected as the most suitable reference gene for P.   x   canescens using three different statistical approaches, geNorm, NormFinder and BestKeeper. Quantitative real-time PCR showed significant reductions in PDS transcripts (55–64%) in the photobleached leaves of both VIGS-treated poplar species. Our results demonstrate that the TRV-based VIGS provides a practical tool for gene functional analysis in Populus sp., especially in those poplar species which are otherwise recalcitrant to transformation.
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    Carbon isotope composition of latex does not reflect temporal variations of photosynthetic carbon isotope discrimination in rubber trees (Hevea brasiliensis) (2015)
    Oxford University Press
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    Publication Date: 2015-11-21
    Description: Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees ( Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex ( 13 C-L), leaf soluble compounds ( 13 C-S) and bulk leaf material ( 13 C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in 13 C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6 on average) with more variable 13 C values than those of untapped trees. 13 C-L was higher and more stable across seasons than 13 C-S and 13 C-B, with a maximum seasonal difference of 0.7 for tapped trees and 0.3 for untapped trees. 13 C-B was lower in tapped than in untapped trees, increasing from August (middle of the rainy season) to April (end of the dry season). Differences in 13 C-L and 13 C-B between tapped and untapped trees indicated that tapping affects the metabolism of both laticiferous cells and leaves. The lack of correlation between 13 C-L and 13 C-S suggests that recent photosynthates are mixed in the large pool of stored carbohydrates that are involved in latex regeneration after tapping.
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    Non-structural carbon dynamics and allocation relate to growth rate and leaf habit in California oaks (2015)
    Oxford University Press
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    Publication Date: 2015-11-21
    Description: Trees contain non-structural carbon (NSC), but it is unclear for how long these reserves are stored and to what degree they are used to support plant activity. We used radiocarbon ( 14 C) to show that the carbon (C) in stemwood NSC can achieve ages of several decades in California oaks. We separated NSC into two fractions: soluble (~50% sugars) and insoluble (mostly starch) NSC. Soluble NSC contained more C than insoluble NSC, but we found no consistent trend in the amount of either pool with depth in the stem. There was no systematic difference in C age between the two fractions, although ages increased with stem depth. The C in both NSC fractions was consistently younger than the structural C from which they were extracted. Together, these results indicate considerable inward mixing of NSC within the stem and rapid exchange between soluble and insoluble pools, compared with the timescale of inward mixing. We observed similar patterns in sympatric evergreen and deciduous oaks and the largest differences among tree stems with different growth rates. The 14 C signature of carbon dioxide (CO 2 ) emitted from tree stems was higher than expected from very recent photoassimilates, indicating that the mean age of C in respiration substrates included a contribution from C fixed years previously. A simple model that tracks NSC produced each year, followed by loss (through conversion to CO 2 ) in subsequent years, matches our observations of inward mixing of NSC in the stem and higher 14 C signature of stem CO 2 efflux. Together, these data support the idea of continuous accumulation of NSC in stemwood and that ‘vigor’ (growth rate) and leaf habit (deciduous vs evergreen) control NSC pool size and allocation.
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Overexpression of gibberellin 20-oxidase1 from Pinus densiflora results in enhanced wood formation with gelatinous fiber development in a transgenic hybrid poplar (2015)
    Oxford University Press
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    Publication Date: 2015-11-21
    Description: Gibberellins (GAs) are important regulators of plant shoot biomass growth, and GA 20-oxidase (GA20ox) is one of the major regulatory enzymes in the GA biosynthetic pathway. Previously, we showed that the expression levels of a putative GA20ox1 (i.e., PdGA20ox1 ) in stem tissue of 3-month-old seedlings of 12 families of Pinus densiflora were positively correlated with stem diameter growth across those same families growing in an even-aged 32-year-old pine forest (Park EJ, Lee WY, Kurepin LV, Zhang R, Janzen L, Pharis RP (2015) Plant hormone-assisted early family selection in Pinus densiflora via a retrospective approach. Tree Physiol 35:86–94). To further investigate the molecular function of this gene in the stem wood growth of forest trees, we produced transgenic poplar lines expressing PdGA20ox1 under the control of the 35S promoter (designated as 35S::PdGA20ox1). By age 3 months, most of the 35S::PdGA20ox1 poplar trees were showing an exceptional enhancement of stem wood growth, i.e., up to fourfold increases in stem dry weight, compared with the nontransformed control poplar plants. Significant increases in endogenous GA 1 , its immediate precursor (GA 20 ) and its catabolite (GA 8 ) in elongating internode tissue accompanied the increased stem growth in the transgenic lines. Additionally, the development of gelatinous fibers occurred in vertically grown stems of the 35S::PdGA20ox1 poplars. An analysis of the cell wall monosaccharide composition of the 35S::PdGA20ox1 poplars showed significant increases in xylose and glucose contents, indicating a qualitative increase in secondary wall depositions. Microarray analyses led us to find a total of 276 probe sets that were upregulated (using threefold as a threshold) in the stem tissues of 35S::PdGA20ox1 poplars relative to the controls. ‘Cell organization or biogenesis’- and ‘cell wall’-related genes were overrepresented, including many of genes that are involved in cell wall modification. Several transcriptional regulators, which positively regulate cell elongation through GA signaling, were also upregulated. In contrast, genes involved in defense signaling were appreciably downregulated in the 35S::PdGA20ox1 stem tissues, suggesting a growth versus defense trade-off. Taken together, our results suggest that PdGA20ox1 functions to promote stem growth and wood formation in poplar, probably by activating GA signaling while coincidentally depressing defense signaling.
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    Ponderosa pine resin defenses and growth: metrics matter (2015)
    Oxford University Press
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    Publication Date: 2015-11-21
    Description: Bark beetles (Coleoptera: Curculionidae, Scolytinae) cause widespread tree mortality in coniferous forests worldwide. Constitutive and induced host defenses are important factors in an individual tree’s ability to survive an attack and in bottom-up regulation of bark beetle population dynamics, yet quantifying defense levels is often difficult. For example, in Pinus spp., resin flow is important for resistance to bark beetles but is extremely variable among individuals and within a season. While resin is produced and stored in resin ducts, the specific resin duct metrics that best correlate with resin flow remain unclear. The ability and timing of some pine species to produce induced resin is also not well understood. We investigated (i) the relationships between ponderosa pine ( Pinus ponderosa Lawson & C. Lawson) resin flow and axial resin duct characteristics, tree growth and physiological variables, and (ii) if mechanical wounding induces ponderosa pine resin flow and resin ducts in the absence of bark beetles. Resin flow increased later in the growing season under moderate water stress and was highest in faster growing trees. The best predictors of resin flow were nonstandardized measures of resin ducts, resin duct size and total resin duct area, both of which increased with tree growth. However, while faster growing trees tended to produce more resin, models of resin flow using only tree growth were not statistically significant. Further, the standardized measures of resin ducts, density and duct area relative to xylem area, decreased with tree growth rate, indicating that slower growing trees invested more in resin duct defenses per unit area of radial growth, despite a tendency to produce less resin overall. We also found that mechanical wounding induced ponderosa pine defenses, but this response was slow. Resin flow increased after 28 days, and resin duct production did not increase until the following year. These slow induced responses may allow unsuccessfully attacked or wounded trees to resist future bark beetle attacks. Forest management that encourages healthy, vigorously growing trees will also favor larger resin ducts, thereby conferring increased constitutive resistance to bark beetle attacks.
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    Leaf-age effects on temperature responses of photosynthesis and respiration of an alpine oak, Quercus aquifolioides, in southwestern China (2015)
    Oxford University Press
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    Publication Date: 2015-11-21
    Description: Temperature responses and sensitivity of photosynthesis ( A n _ T ) and respiration for leaves at different ages are crucial to modeling ecosystem carbon (C) cycles and productivity of evergreen forests. Understanding the mechanisms and processes of temperature sensitivity may further shed lights on temperature acclimation of photosynthesis and respiration with leaf aging. The current study examined temperature responses of photosynthesis and respiration of young leaves (YLs) (fully expanded in current growth season) and old leaves (OLs) (fully expanded in last growth season) of Quercus aquifolioides Rehder and E.H. Wilson in an alpine oak forest, southwestern China. Temperature responses of dark respiration ( R dark ), net assimilation ( A n ), maximal velocity of carboxylation ( V cmax ) and maximum rate of electron transport ( J max ) were significantly different between the two leaf ages. Those differences implied different temperature response parameters should be used for leaves of different ages in modeling vegetation productivity and ecosystem C cycles in Q. aquifolioides forests and other evergreen forests. We found that RuBP carboxylation determined the downward shift of A n _ T in OLs, while RuBP regeneration and the balance between Rubisco carboxylation and RuBP regeneration made little contribution. Sensitivity of stomatal conductance to vapor pressure deficit changed in OLs and compensated part of the downward shift. We also found that OLs of Q. aquifolioides had lower A n due to lower stomatal conductance, higher stomatal conductance limitation and deactivation of the biochemical processes. In addition, the balance between R dark and A n changed between OLs and YLs, which was represented by a higher R dark / A n ratio for OLs.
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    Allocation of freshly assimilated carbon into primary and secondary metabolites after in situ 13C pulse labelling of Norway spruce (Picea abies) (2015)
    Oxford University Press
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    Publication Date: 2015-11-21
    Description: Plants allocate carbon (C) to sink tissues depending on phenological, physiological or environmental factors. We still have little knowledge on C partitioning into various cellular compounds and metabolic pathways at various ecophysiological stages. We used compound-specific stable isotope analysis to investigate C partitioning of freshly assimilated C into tree compartments (needles, branches and stem) as well as into needle water-soluble organic C (WSOC), non-hydrolysable structural organic C (stOC) and individual chemical compound classes (amino acids, hemicellulose sugars, fatty acids and alkanes) of Norway spruce ( Picea abies ) following in situ 13 C pulse labelling 15 days after bud break. The 13 C allocation within the above-ground tree biomass demonstrated needles as a major C sink, accounting for 86% of the freshly assimilated C 6 h after labelling. In needles, the highest allocation occurred not only into the WSOC pool (44.1% of recovered needle 13 C) but also into stOC (33.9%). Needle growth, however, also caused high 13 C allocation into pathways not involved in the formation of structural compounds: (i) pathways in secondary metabolism, (ii) C-1 metabolism and (iii) amino acid synthesis from photorespiration. These pathways could be identified by a high 13 C enrichment of their key amino acids. In addition, 13 C was strongly allocated into the n -alkyl lipid fraction (0.3% of recovered 13 C), whereby 13 C allocation into cellular and cuticular exceeded that of epicuticular fatty acids. 13 C allocation decreased along the lipid transformation and translocation pathways: the allocation was highest for precursor fatty acids, lower for elongated fatty acids and lowest for the decarbonylated n -alkanes. The combination of 13 C pulse labelling with compound-specific 13 C analysis of key metabolites enabled tracing relevant C allocation pathways under field conditions. Besides the primary metabolism synthesizing structural cell compounds, a complex network of pathways consumed the assimilated 13 C and kept most of the assimilated C in the growing needles.
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    Non-structural carbohydrates in woody plants compared among laboratories (2015)
    Quentin, A. G., Pinkard, E. A., Ryan, M. G., Tissue, D. T., Baggett, L. S., Adams, H. D., Maillard, P., Marchand, J., Landhäusser, S. M., Lacointe, A., Gibon, Y., Anderegg, W. R. L., Asao, S., Atkin, O. K., Bonhomme, M., Claye, C., Chow, P. S., Clement-Vidal, A., Davies, N. W., Dickman, L. T., Dumbur, R., Ellsworth, D. S., Falk, K., Galiano, L., Grünzweig, J. M., Hartmann, H., Hoch, G., Hood, S., Jones, J. E., Koike, T., Kuhlmann, I., Lloret, F., Maestro, M., Mansfield, S. D., Martinez-Vilalta, J., Maucourt, M., McDowell, N. G., Moing, A., Muller, B., Nebauer, S. G., Niinemets, U., Palacio, S., Piper, F., Raveh, E., Richter, A., Rolland, G., Rosas, T., Saint Joanis, B., Sala, A., Smith, R. A., Sterck, F., Stinziano, J. R., Tobias, M., Unda, F., Watanabe, M., Way, D. A., Weerasinghe, L. K., Wild, B., Wiley, E., Woodruff, D. R.
    Oxford University Press
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    Publication Date: 2015-11-21
    Description: Non-structural carbohydrates (NSC) in plant tissue are frequently quantified to make inferences about plant responses to environmental conditions. Laboratories publishing estimates of NSC of woody plants use many different methods to evaluate NSC. We asked whether NSC estimates in the recent literature could be quantitatively compared among studies. We also asked whether any differences among laboratories were related to the extraction and quantification methods used to determine starch and sugar concentrations. These questions were addressed by sending sub-samples collected from five woody plant tissues, which varied in NSC content and chemical composition, to 29 laboratories. Each laboratory analyzed the samples with their laboratory-specific protocols, based on recent publications, to determine concentrations of soluble sugars, starch and their sum, total NSC. Laboratory estimates differed substantially for all samples. For example, estimates for Eucalyptus globulus leaves (EGL) varied from 23 to 116 (mean = 56) mg g –1 for soluble sugars, 6–533 (mean = 94) mg g –1 for starch and 53–649 (mean = 153) mg g –1 for total NSC. Mixed model analysis of variance showed that much of the variability among laboratories was unrelated to the categories we used for extraction and quantification methods (method category R 2 = 0.05–0.12 for soluble sugars, 0.10–0.33 for starch and 0.01–0.09 for total NSC). For EGL, the difference between the highest and lowest least squares means for categories in the mixed model analysis was 33 mg g –1 for total NSC, compared with the range of laboratory estimates of 596 mg g –1 . Laboratories were reasonably consistent in their ranks of estimates among tissues for starch ( r = 0.41–0.91), but less so for total NSC ( r = 0.45–0.84) and soluble sugars ( r = 0.11–0.83). Our results show that NSC estimates for woody plant tissues cannot be compared among laboratories. The relative changes in NSC between treatments measured within a laboratory may be comparable within and between laboratories, especially for starch. To obtain comparable NSC estimates, we suggest that users can either adopt the reference method given in this publication, or report estimates for a portion of samples using the reference method, and report estimates for a standard reference material. Researchers interested in NSC estimates should work to identify and adopt standard methods.
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    Modelling an aggregate agricultural panel with application to US farm input demands (2015)
    Oxford University Press
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    Publication Date: 2015-05-26
    Description: A recent class of factor demand models is discussed and used to analyse US state-level production data. The approach accommodates output risk, heterogeneous technologies, technological change, endogenous variables, aggregation across agents and more general flexible functional forms than previous models. We find the approach to flexibility found in the consumer literature empirically useful in the analysis of producer behaviour as our results suggest that standard flexible models that have been ubiquitous in agricultural and industrial research are strongly rejected here in favour of a more general and flexible specification. Further, there is substantial heterogeneity of conditional own-price elasticities across states.
    Keywords: C30 - General, D20 - General, D80 - General, Q10 - General
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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    Simulating welfare effects of the European nutrition and health claims' regulation: the Italian yogurt market (2015)
    Oxford University Press
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    Publication Date: 2015-05-26
    Description: With the enactment of Regulation (EC) No. 1924/2006, 20 December 2006, ‘ On nutrition and health claims made on foods ’ several health claims can no longer be used on food products in European markets. We simulate the overall impact of the regulation on consumers and producers using the Italian yogurt market as a case study, and data prior to the introduction of the policy. We quantify welfare losses incurred if accepted claims were false, and simulate scenarios where rejected truthful health claims are removed, considering also the case where the products carrying them exit the market. We find that consumers can incur large welfare losses if approved claims are untruthful; if truthful claims are instead denied both consumers and producers may incur losses, with consumers being penalised more than producers.
    Keywords: L66 - Food ; Beverages ; Cosmetics ; Tobacco ; Wine and Spirits, M38 - Government Policy and Regulation, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 0165-1587
    Electronic ISSN: 1464-3618
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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    Growth, biomass allocation and photosynthetic responses are related to intensity of root severance and soil moisture conditions in the plantation tree Cunninghamia lanceolata (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: We employed the warm temperate conifer Cunninghamia lanceolata (Lamb.) Hook. as a model of plantation forest species to investigate ecophysiological responses to root treatments (control (0%), and ~25, 50 or 75% of the initial root mass) under well-watered and water-limited conditions. Our results indicated that total root dry mass accumulation was negatively associated with the severity of root pruning, but there was evidence of multiple compensatory responses. The plants exhibited higher instantaneous and long-term (assessed by carbon isotope composition, 13 C) water-use efficiency in pruning treatments, especially under low water availability. Root pruning also increased the fine root/total root mass ratio, specific root length and fine root vitality in both water availability treatments. As a result of the compensatory responses, under well-watered conditions, height, stem dry mass accumulation, leaf/fine root biomass ratio (L/FR), transpiration rate, photosynthetic capacity and photosynthetic nitrogen-use efficiency ( E N ) were the highest under 25% pruning. Yet, all these traits except L/FR and foliage nitrogen content were severely reduced under 75% pruning. Drought negatively affected growth and leaf gas exchange rates, and there was a greater negative effect on growth, water potential, gas exchange and E N when 〉25% of total root biomass was removed. The stem/aboveground mass ratio was the highest under 25% pruning in both watering conditions. These results indicate that the responses to root severance are related to the excision intensity and soil moisture content. A moderate root pruning proved to be an effective means to improve stem dry mass accumulation.
    Print ISSN: 0829-318X
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    Environmental drivers of cambial phenology in Great Basin bristlecone pine (2016)
    Oxford University Press
    Details
    Publication Date: 2016-08-03
    Description: The timing of wood formation is crucial to determine how environmental factors affect tree growth. The long-lived bristlecone pine ( Pinus longaeva D. K. Bailey) is a foundation treeline species in the Great Basin of North America reaching stem ages of about 5000 years. We investigated stem cambial phenology and radial size variability to quantify the relative influence of environmental variables on bristlecone pine growth. Repeated cellular measurements and half-hourly dendrometer records were obtained during 2013 and 2014 for two high-elevation stands included in the Nevada Climate-ecohydrological Assessment Network. Daily time series of stem radial variations showed rehydration and expansion starting in late April–early May, prior to the onset of wood formation at breast height. Formation of new xylem started in June and lasted until mid-September. There were no differences in phenological timing between the two stands, or in the air and soil temperature thresholds for the onset of xylogenesis. A multiple logistic regression model highlighted a separate effect of air and soil temperature on xylogenesis, the relevance of which was modulated by the interaction with vapor pressure and soil water content. While air temperature plays a key role in cambial resumption after winter dormancy, soil thermal conditions coupled with snowpack dynamics also influence the onset of wood formation by regulating plant–soil water exchanges. Our results help build a physiological understanding of climate–growth relationships in P. longaeva , the importance of which for dendroclimatic reconstructions can hardly be overstated. In addition, environmental drivers of xylogenesis at the treeline ecotone, by controlling the growth of dominant species, ultimately determine ecosystem responses to climatic change.
    Print ISSN: 0829-318X
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Monitoring intra-annual dynamics of wood formation with microcores and dendrometers in Picea abies at two different altitudes (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: Seasonal analyses of cambial cell production and day-by-day stem radial increment can help to elucidate how climate modulates wood formation in conifers. Intra-annual dynamics of wood formation were determined with microcores and dendrometers and related to climatic signals in Norway spruce ( Picea abies (L.) Karst.). The seasonal dynamics of these processes were observed at two sites of different altitude, Savignano (650 m a.s.l.) and Lavazè (1800 m a.s.l.) in the Italian Alps. Seasonal dynamics of cambial activity were found to be site specific, indicating that the phenology of cambial cell production is highly variable and plastic with altitude. There was a site-specific trend in the number of cells in the wall thickening phase, with the maximum cell production in early July (DOY 186) at Savignano and in mid-July (DOY 200) at Lavazè. The formation of mature cells showed similar trends at the two sites, although different numbers of cells and timing of cell differentiation were visible in the model shapes; at the end of ring formation in 2010, the number of cells was four times higher at Savignano (106.5 cells) than at Lavazè (26.5 cells). At low altitudes, microcores and dendrometers described the radial growth patterns comparably, though the dendrometer function underlined the higher upper asymptote of maximum growth in comparison with the cell production function. In contrast, at high altitude, these functions exhibited different trends. The best model was obtained by fitting functions of the Gompertz model to the experimental data. By combining radial growth and cambial activity indices we defined a model system able to synchronize these processes. Processes of adaptation of the pattern of xylogenesis occurred, enabling P. abies to occupy sites with contrasting climatic conditions. The use of daily climatic variables in combination with plant functional traits obtained by sensors and/or destructive sampling could provide a suitable tool to better investigate the effect of disturbances on response strategies in trees and, consequently, contribute to improving our prediction of tree growth and species resilience based on climate scenarios.
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    Coordination between growth, phenology and carbon storage in three coexisting deciduous tree species in a temperate forest (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: In deciduous trees growing in temperate forests, bud break and growth in spring must rely on intrinsic carbon (C) reserves. Yet it is unclear whether growth and C storage occur simultaneously, and whether starch C in branches is sufficient for refoliation. To test in situ the relationships between growth, phenology and C utilization, we monitored stem growth, leaf phenology and stem and branch nonstructural carbohydrate (NSC) dynamics in three deciduous species: Carpinus betulus L., Fagus sylvatica L. and Quercus petraea (Matt.) Liebl. To quantify the role of NSC in C investment into growth, a C balance approach was applied. Across the three species, 〉95% of branchlet starch was consumed during bud break, confirming the importance of C reserves for refoliation in spring. The C balance calculation showed that 90% of the C investment in foliage (7.0–10.5 kg tree –1 and 5–17 times the C needed for annual stem growth) was explained by simultaneous branchlet starch degradation. Carbon reserves were recovered sooner than expected, after leaf expansion, in parallel with stem growth. Carpinus had earlier leaf phenology (by ~25 days) but delayed cambial growth (by ~15 days) than Fagus and Quercus , the result of a competitive strategy to flush early, while having lower NSC levels.
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    Scaling of photosynthesis and constitutive and induced volatile emissions with severity of leaf infection by rust fungus (Melampsora larici-populina) in Populus balsamifera var. suaveolens (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: Fungal infections result in decreases in photosynthesis, induction of stress and signaling volatile emissions and reductions in constitutive volatile emissions, but the way different physiological processes scale with the severity of infection is poorly known. We studied the effects of infection by the obligate biotrophic fungal pathogen Melampsora larici-populina Kleb., the causal agent of poplar leaf rust disease, on photosynthetic characteristics, and constitutive isoprene and induced volatile emissions in leaves of Populus balsamifera var. suaveolens (Fisch.) Loudon. exhibiting different degrees of damage. The degree of fungal damage, quantified by the total area of chlorotic and necrotic leaf areas, varied between 0 (noninfected control) and ~60%. The rates of all physiological processes scaled quantitatively with the degree of visual damage, but the scaling with damage severity was weaker for photosynthetic characteristics than for constitutive and induced volatile release. Over the whole range of damage severity, the net assimilation rate per area ( A A ) decreased 1.5-fold, dry mass per unit area 2.4-fold and constitutive isoprene emissions 5-fold, while stomatal conductance increased 1.9-fold and dark respiration rate 1.6-fold. The emissions of key stress and signaling volatiles (methanol, green leaf volatiles, monoterpenes, sesquiterpenes and methyl salicylate) were in most cases nondetectable in noninfested leaves, and increased strongly with increasing the spread of infection. The moderate reduction in A A resulted from the loss of photosynthetically active biomass, but the reduction in constitutive isoprene emissions and the increase in induced volatile emissions primarily reflected changes in the activities of corresponding biochemical pathways. Although all physiological alterations in fungal-infected leaves occurred in a stress severity-dependent manner, modifications in primary and secondary metabolic pathways scaled differently due to contrasting operational mechanisms.
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    Genetic variability and heritability of chlorophyll a fluorescence parameters in Scots pine (Pinus sylvestris L.) (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: Current knowledge of the genetic mechanisms underlying the inheritance of photosynthetic activity in forest trees is generally limited, yet it is essential both for various practical forestry purposes and for better understanding of broader evolutionary mechanisms. In this study, we investigated genetic variation underlying selected chlorophyll a fluorescence (ChlF) parameters in structured populations of Scots pine ( Pinus sylvestris L.) grown on two sites under non-stress conditions. These parameters were derived from the OJIP part of the ChlF kinetics curve and characterize individual parts of primary photosynthetic processes associated, for example, with the exciton trapping by light-harvesting antennae, energy utilization in photosystem II (PSII) reaction centers (RCs) and its transfer further down the photosynthetic electron-transport chain. An additive relationship matrix was estimated based on pedigree reconstruction, utilizing a set of highly polymorphic single sequence repeat markers. Variance decomposition was conducted using the animal genetic evaluation mixed-linear model. The majority of ChlF parameters in the analyzed pine populations showed significant additive genetic variation. Statistically significant heritability estimates were obtained for most ChlF indices, with the exception of DI 0 /RC, D0 and P0 ( F v / F m ) parameters. Estimated heritabilities varied around the value of 0.15 with the maximal value of 0.23 in the ET 0 /RC parameter, which indicates electron-transport flux from Q A to Q B per PSII RC. No significant correlation was found between these indices and selected growth traits. Moreover, no genotype  x  environment interaction (G  x  E) was detected, i.e., no differences in genotypes’ performance between sites. The absence of significant G  x  E in our study is interesting, given the relatively low heritability found for the majority of parameters analyzed. Therefore, we infer that polygenic variability of these indices is selectively neutral.
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    Transgenic poplar overexpressing the endogenous transcription factor ERF76 gene improves salinity tolerance (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: The ethylene response factor (ERF) family is one of the largest plant-specific transcription factor families, playing an important role in plant development and response to stresses. The ERF76 gene is a member of the poplar ERF transcription factor gene family. First, we validated that the ERF76 gene expressed in leaf and root tissues is responsive to salinity stress. We then successfully cloned the ERF76 cDNA fragment containing an open reading frame from di-haploid Populus simonii   x   Populus nigra and proved that ERF76 protein is targeted to the nucleus. Finally, we transferred the gene into the same poplar clone by the Agrobacterium -mediated leaf disc method. Using both RNA-Seq and reverse transcription-quantitative polymerase chain reaction, we validated that expression level of ERF76 is significantly higher in transgenic plants than that in the nontransgenic control. Using RNA-Seq data, we have identified 375 genes that are differentially expressed between the transgenic plants and the control under salt treatment. Among the differentially expressed genes, 16 are transcription factor genes and 45 are stress-related genes, both of which are upregulated significantly in transgenic plants, compared with the control. Under salt stress, the transgenic plants showed significant increases in plant height, root length, fresh weight, and abscisic acid (ABA) and gibberellin (GA) concentration compared with the control, suggesting that overexpression of ERF76 in transgenic poplar upregulated the expression of stress-related genes and increased the ability of ABA and GA biosynthesis, which resulted in stronger tolerance to salt stress.
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    Adaptive mechanisms and genomic plasticity for drought tolerance identified in European black poplar (Populus nigra L.) (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: Summer droughts are likely to increase in frequency and intensity across Europe, yet long-lived trees may have a limited ability to tolerate drought. It is therefore critical that we improve our understanding of phenotypic plasticity to drought in natural populations for ecologically and economically important trees such as Populus nigra L. A common garden experiment was conducted using ~500 wild P. nigra trees, collected from 11 river populations across Europe. Phenotypic variation was found across the collection, with southern genotypes from Spain and France characterized by small leaves and limited biomass production. To examine the relationship between phenotypic variation and drought tolerance, six genotypes with contrasting leaf morphologies were subjected to a water deficit experiment. ‘North eastern’ genotypes were collected at wet sites and responded to water deficit with reduced biomass growth, slow stomatal closure and reduced water use efficiency (WUE) assessed by 13 C. In contrast, ‘southern’ genotypes originating from arid sites showed rapid stomatal closure, improved WUE and limited leaf loss. Transcriptome analyses of a genotype from Spain (Sp2, originating from an arid site) and another from northern Italy (Ita, originating from a wet site) revealed dramatic differences in gene expression response to water deficit. Transcripts controlling leaf development and stomatal patterning, including SPCH , ANT , ER , AS1 , AS2 , PHB , CLV1 , ERL1–3 and TMM , were down-regulated in Ita but not in Sp2 in response to drought.
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    Gene expression analysis of disabled and re-induced isoprene emission by the tropical tree Ficus septica before and after cold ambient temperature exposure (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: Isoprene is the most abundant type of nonmethane, biogenic volatile organic compound in the atmosphere, and it is produced mainly by terrestrial plants. The tropical tree species Ficus septica Burm. F. (Rosales: Moraceae) has been shown to cease isoprene emissions when exposed to temperatures of 12 °C or lower and to re-induce isoprene synthesis upon subsequent exposure to temperatures of 30 °C or higher for 24 h. To elucidate the regulation of genes underlying the disabling and then induction of isoprene emission during acclimatization to ambient temperature, we conducted gene expression analyses of F. septica plants under changing temperature using quantitative real-time polymerase chain reaction and western blotting. Transcription levels were analyzed for 17 genes that are involved in metabolic pathways potentially associated with isoprene biosynthesis, including isoprene synthase ( ispS ). The protein levels of ispS were also measured. Changes in transcription and protein levels of the ispS gene, but not in the other assessed genes, showed identical temporal patterns to isoprene emission capacity under the changing temperature regime. The ispS protein levels strongly and positively correlated with isoprene emission capacity ( R 2  = 0.92). These results suggest that transcriptional regulation of ispS gave rise to the temporal variation in isoprene emission capacity in response to changing temperature.
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    Physiological integration of connected balsam poplar ramets (2016)
    Oxford University Press
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    Publication Date: 2016-08-03
    Description: Clonal integration between ramets can be an ecological advantage of clonal plant species in environments where resources are patchily distributed. We investigated physiological integration among Populus balsamifera L. ramets under drought stress in order to demonstrate water sharing between connected ramets. Pairs of connected ramets were grown in separate pots in the greenhouse where half of ramets had the parental root connection severed and half were left intact. Drought stress was applied to one ramet, and growth, specific leaf area (SLA), net photosynthesis, stomatal conductance, leaf water potential and carbon isotopic composition ( 13 C) were measured after an 8-week growing period. Droughted ramets connected to watered ramets were able to maintain high gas exchange activity and water potential, similar to watered ramets. Leaf water potential and SLA results showed that the root connection was more beneficial for proximal compared with distal ramets. The parental root connection also allowed droughted ramets to discriminate more against 13 C compared with severed ramets. In conclusion, this study shows compelling evidence of physiological integration of connected P. balsamifera ramets through water sharing.
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    What Can We Learn about the Effects of Food Stamps on Obesity in the Presence of Misreporting? (2016)
    Oxford University Press
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    Publication Date: 2016-07-09
    Description: There is an increasing perception among policy makers that food stamp benefits contribute positively to adult obesity rates. We show that these results are heavily dependent on one’s assumptions regarding the accuracy of reported food stamp participation. When allowing for misreporting, we find no evidence that Supplemental Nutrition Assistance Program participation significantly increases the probability of being obese or overweight among adults. Our results also highlight the inherent bias and inconsistency of common point estimates when ignoring misreporting, with treatment effects from instrumental variable methods exceeding the nonparametric upper bounds by over 200% in some cases.
    Keywords: C11 - Bayesian Analysis, I10 - General, I38 - Government Policy ; Provision and Effects of Welfare Programs
    Print ISSN: 0002-9092
    Electronic ISSN: 1467-8276
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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    Temperature Changes, Household Consumption, and Internal Migration: Evidence from Tanzania (2016)
    Oxford University Press
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    Publication Date: 2016-07-09
    Description: Large rural-urban wage gaps observed in many developing countries are suggestive of barriers to migration that keep potential migrants in rural areas. Using long panel data spanning nearly two decades, I study the extent to which migration rates are constrained by liquidity constraints in rural Tanzania. The analysis begins by quantifying the impact of weather variation on household welfare. The results show how household consumption co-moves with temperature, rendering households vulnerable to local weather events. These temperature-induced income shocks are then found to inhibit long-term migration among men, thus preventing them from tapping into the opportunities brought about by geographical mobility.
    Keywords: O12 - Microeconomic Analyses of Economic Development, O15 - Human Resources ; Human Development ; Income Distribution ; Migration, Q54 - Climate ; Natural Disasters ; Global Warming, R23 - Regional Migration ; Regional Labor Markets ; Population
    Print ISSN: 0002-9092
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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    A Declining Farm Workforce: Analysis of Panel Data from Rural Mexico (2016)
    Oxford University Press
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    Publication Date: 2016-07-09
    Description: Analysis of nationally representative individual-level panel data from 1980 to 2010 reveals a significant negative trend in the agricultural labor supply from rural Mexico, which is the primary source of hired workers for U.S. farms. These findings offer an explanation for the rise over time in U.S. farm wages. Concomitants of the agricultural transformation, including growth in the non-farm economy, falling birth rates, and an increase in rural education, accelerate the transition of rural Mexicans out of farm work. Higher U.S. farm wages and increased border enforcement slow the transition, but the combined impact of these offsetting variables is relatively small. A diminishing farm labor supply has far-reaching implications for farmers, farm labor organizers, rural communities, and agricultural workers.
    Keywords: J21 - Labor Force and Employment, Size, and Structure, J43 - Agricultural Labor Markets, O15 - Human Resources ; Human Development ; Income Distribution ; Migration, Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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    Sugar Coated, a documentary film directed by Michele Hozer. (2016)
    Oxford University Press
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    Publication Date: 2016-07-09
    Print ISSN: 0002-9092
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
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    Forest health in a changing world: effects of globalization and climate change on forest insect and pathogen impacts (2016)
    Oxford University Press
    In: Forestry
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    Publication Date: 2016-05-06
    Description: Forests and trees throughout the world are increasingly affected by factors related to global change. Expanding international trade has facilitated invasions of numerous insects and pathogens into new regions. Many of these invasions have caused substantial forest damage, economic impacts and losses of ecosystem goods and services provided by trees. Climate change is already affecting the geographic distribution of host trees and their associated insects and pathogens, with anticipated increases in pest impacts by both native and invasive pests. Although climate change will benefit many forest insects, changes in thermal conditions may disrupt evolved life history traits and cause phenological mismatches. Individually, the threats posed to forest ecosystems by invasive pests and climate change are serious. Although interactions between these two drivers and their outcomes are poorly understood and hence difficult to predict, it is clear that the cumulative impacts on forest ecosystems will be exacerbated. Here we introduce and synthesize the information in this special issue of Forestry with articles that illustrate the impacts of invasions of insects and pathogens, climate change, forest management and their interactions, as well as methods to predict, assess and mitigate these impacts. Most of these contributions were presented at the XXIV IUFRO World Congress in 2014.
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    Preparing for the invasion: efficacy of DNA barcoding to discern the host range of myrtle rust (Puccinia psidii) among species of Myrtaceae (2016)
    Oxford University Press
    In: Forestry
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    Publication Date: 2016-05-06
    Description: Puccinia psidii is a major threat to members of the Myrtaceae worldwide. New Zealand is still free of P. psidii but possesses significant Eucalyptus plantations as well as valuable native tree species such as Metrosideros excelsa and Leptospermum scoparium that could be at risk in the event of an incursion. As part of preparing for a potential incursion, we generated a barcode reference library for 〉100 diverse species of Myrtaceae occurring in New Zealand by sequencing internal transcribed spacer (ITS), external transcribed spacer (ETS) and maturase K ( matK ), or by obtaining relevant sequences from GenBank. The Myrtaceae DNA barcoding database will enable rapid identification of large numbers of host species in the event of a myrtle rust incursion. We undertook a comparative analysis of the ability for the three mentioned loci to discriminate species. Interspecific divergence was assessed by mean interspecific distance, prime and minimum interspecific distance; intraspecific variation was evaluated by mean intraspecific difference, and coalescent depth. Overall identification efficiency of the three loci sequenced was determined using BLAST1 and Near Distance methods. Barcoding gaps between inter- and intraspecific divergences were also analysed. ITS and ETS share similar mean interspecific distance, prime and minimum interspecific distance values – both higher than obtained for matK . In contrast, in terms of intraspecific variation, matK had higher values than ITS and ETS in all three metrics analysed. ITS had the highest identification success rate for species followed by matK and ETS, respectively, as measured by BLAST1 and Near Distance methods. Overall identification success rate increases when a combination of ITS and matK in particular is used. The sequence data are not only a valuable reference collection for a myrtle rust response but also a national botanical resource.
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    Elevational shifts in thermal suitability for mountain pine beetle population growth in a changing climate (2016)
    Oxford University Press
    In: Forestry
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    Publication Date: 2016-05-06
    Description: Future forests are being shaped by changing climate and disturbances. Climate change is causing large-scale forest declines globally, in addition to distributional shifts of many tree species. Because environmental cues dictate insect seasonality and population success, climate change is also influencing tree-killing bark beetles. The mountain pine beetle, Dendroctonus ponderosae , is a major disturbance in Pinus forests of the western US. Using a mechanistic, phenology-based demographic model driven by downscaled daily temperature data, we describe recent and future spatial and temporal thermal suitability for mountain pine beetle population growth in a topographically complex region. Trends in model-predicted growth rates among Global Climate Models were similar and suggest that, relative to future trends, mountain pine beetle population growth within the past 60 years was most optimal at middle elevations and least optimal at the lowest and highest elevations. This trend aligns with observed mountain pine beetle-caused tree mortality that was greatest at middle elevations between 1997 and 2013, as estimated from Aerial Detection Surveys. However, thermal suitability for optimal phenological synchrony was predicted to shift in recent years, and by the end of the century, the best thermal habitats for mountain pine beetle will be at the lowest and highest elevations. Mechanistic demographic models are valuable tools for modelling future thermal regimes that may be both beneficial and maladaptive for mountain pine beetle population growth and subsequent tree mortality.
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    Determining forest degradation, ecosystem state and resilience using a standard stand stocking measurement diagram: theory into practice (2016)
    Oxford University Press
    In: Forestry
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    Publication Date: 2016-05-06
    Description: Forest degradation is a major issue for policy-makers that is exacerbated by no clear and globally accepted definition of the term. For forest managers, a loss of forest productive capacity is one form of forest degradation. We present a quantitative method to assess forest degradation from a productivity perspective. Our method uses a standard stocking chart and calculation methods based on standard forest inventory data, to derive a clear threshold value for stocking, below which a forest should be considered degraded. The method is illustrated using the example of a self-regenerating Nothofagus production forest type from Chile. For that forest type, we determined that harvesting trees to below a specific basal area relative to site type, resulted in a loss of resilience, an unpredictable shift in ecosystem state, and a degraded condition. Our method illustrates how over-harvesting can degrade the long-term productivity of a stand and forest resilience. Nevertheless, it is important to consider that forests can also be degraded from other perspectives, such as loss of biodiversity, carbon, or protective functions as a result of excessive disturbances. Ecosystem management requires that managers consider degradation from a range of perspectives. We see the quantified approach used here as a way to provide practitioners with, in part, a transition from sustained yield to ecosystem management with an ultimate objective of providing a pathway towards adaptive management of complex systems and avoiding degradation.
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    Electronic ISSN: 1464-3626
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Analysis of costs and benefits of Asian longhorned beetle eradication in Italy (2016)
    Oxford University Press
    In: Forestry
    Details
    Publication Date: 2016-05-06
    Description: The Asian longhorned beetle (ALB), Anoplophora glabripennis (Coleoptera: Cerambycidae), is one of the most harmful invasive species in Europe and North America, causing enormous economic damage to broadleaved trees growing in urban parks and gardens. As a quarantine species, everywhere it has been introduced ALB has led to the application of expensive eradication programmes often associated with additional indirect costs due to the loss of ornamental value connected with the presence of trees in urban areas. The aims of this article are to quantify the impact of ALB in terms of tree mortality and their ornamental value during the first year eradication of an infestation in Northern Italy, and to perform an economic assessment of the eradication programme vs inaction. During the first year of eradication 367 ALB infested trees were removed from the infestation area at a total cost of about 48 000, comprising scientific advice (21 per cent), tree survey (38 per cent) and plant removal (41 per cent). The ornamental value of the infested trees was assessed at about 850 per tree. The ALB eradication programme allowed a reduction of 52 per cent of the damage expected in the following year, corresponding to an ornamental value of about 300 000. The ornamental value of the saved trees was ~6 times higher than the costs for their protection.
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Performance analysis of a cascaded solar Organic Rankine Cycle with superheating (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: A cascaded Organic Rankine Cycle (ORC) with scroll expanders is investigated in this paper, the system performances under various configurations are evaluated and the effect of superheating on the system efficiency is clarified. The efficiency of two-stage ORC system is 38.9% higher than that of single-stage system when R245fa is used as the working fluid, while the efficiency of two-stage ORC system is 10% lower than that of single stage when R134a is adopted. The specific work of single-stage ORC system with R245fa increases linearly with the degree of superheat. There is an optimal superheated degree for the system output power and efficiency, which is 35 K for the expansion ratio of 3.5 and 45 K for the expansion ratio of 5.
    Print ISSN: 1748-1317
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    Investigation of the effect of design parameters on power output and thermal efficiency of a Stirling engine by thermodynamic analysis (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: This article demonstrates a study on finite-time thermodynamic assessment and analysis of a Stirling heat engine. Finite-time thermodynamics is performed to specify the net thermal efficiency and power output of the Stirling system with finite-rate heat transfer, regenerative heat loss, conductive thermal bridging loss and finite regeneration process time. The model investigates effects of the inlet temperature of the heat source, the volumetric ratio of the engine, effectiveness of heat exchangers and heat capacitance rates on the net power output and thermal efficiency of the engine. Output power of the Stirling engine is maximized under two optimization scenarios. In the first scenario, the higher working temperature of the Stirling engine is considered as a decision design parameter (decision variable) while in the second scenario, in addition to the higher working temperature, the temperature ratio of the engine is also considered as a design parameter. Furthermore, the thermal efficiency of the cycle corresponding to the magnitude of the maximized power of the engine is evaluated. Finally, sensitivities of results towards shift in the thermal parameters of the engine are studied.
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    Energy saving potential of indirect evaporative cooler under Indian climates (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: Vapour compression refrigeration-based air conditioners are being used for comfort cooling in residences, offices and commercial buildings in many countries throughout the world. These systems consume substantial power and energy and produce harmful effect on environment by damaging ozone layer. This article presents an analytical evaluation of energy saving potential of an indirect evaporative cooler for summer months in Indian climates. Three climates likely to be suitable for indirect evaporative cooling, namely composite, hot and dry and moderate, have been selected for this purpose. The monthly average environmental data for three Indian cities namely Delhi, Jodhpur and Bangalore representing three different climates were used for this study. Summer month—May was selected for the study. It has been found that in order to produce same cooling effect under the same climatic conditions, the power needed by indirect evaporative cooler to be about 55% less than that needed by a conventional air conditioner. The performance of an indirect evaporative cooler in the climates, hot and dry and composite, has been found to be almost similar. Thus, substantial energy can be saved by using this alternative in summer months.
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    Development of a nano-heat transfer fluid carrying direct absorbing receiver for concentrating solar collectors (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: A MATLAB-based computer model to design a novel directly absorbing receiver system (DARS) for concentrating solar collectors employing nanofluid-based solar radiation volumetric absorption is presented. Graphene and aluminum nanosphere-based suspensions in Therminol VP-1 were simulated to identify the optimum thermo-geometric configuration of a DARS comprising a transparent all glass tubular absorber. Several particle concentrations were simulated scrutinizing the optical response of the two colloidal dispersions to yield a minimum supply temperature of 250°C; further investigated are the implications of fluid flow velocity upon system yield. The resulting temperature fields and geometric dimensions of the DARS are predicted. Findings demonstrate that the DARS is able to deliver heat at ~265°C with a receiver tube diameter of 5 mm opposed to commercially available 70-mm diameter metallic absorbers.
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    Mean-line modeling and CFD analysis of a miniature radial turbine for distributed power generation systems (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: Distributed power generation (DPG) based on organic Rankine cycle offers potential in the effective use of energy from low grade heat sources up to 200°C. In this regard, developing an effective expander plays a major role in determining the overall cycle efficiency. In this work mean-line modeling and CFD techniques are employed to develop a small-scale radial turbine for DPG systems with a power output of ~5 kWe. A parametric study is carried out using the mean-line approach to investigate the effects of key input parameters such as operating conditions, velocity ratio, rotational speed and rotor flow angles on the turbine rotor inlet diameter and overall performance. Results from the mean-line approach show that in order to achieve high power output, inlet total temperature, mass flow rate and pressure ratio should be increased. However, for reducing the rotor inlet diameter the velocity ratio should be decreased. CFD technique is then used to assess the flow field and to improve the blade loading by modification of blade angle distribution. CFD is also used to determine the minimum number of rotor blades and the results show that the value suggested by mean-line modeling overestimates this parameter. By using these two approaches a wide range of design configurations are explored and the most effective design is identified to be with specific diameter of 4.83 (rotor inlet diameter of 0.0787 m), specific speed of 0.433 (rotational speed of 55 000 rpm), 10 blades and output power of 4.662 kW.
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    Hybrid hydrogen PEM fuel cell and batteries without DC-DC converter (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: Concerns about greenhouse gases as well as the price and security of oil supply have acted as a spur to sustainable automobile development. The hydrogen fuel cells electric vehicle (HFCEV) is generally recognised by leading automobile manufacturers and scientists as one of the optimum technologies for long-term future low carbon vehicle. In a typical HFCEV power train, a DC–DC converter is required to balance the voltage difference between the fuel cells (FCs) stack and batteries. However, research shows that a considerable amount of energy generated by the hydrogen FCs stack is deplete during this conversion process as heat. This experiment aims to improve the power train efficiency by eliminating the DC–DC converter by finding the best combination of FC stack and batteries, matching the size and capacity of the electrical components.
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    Energy and exergy analysis of passive solar distillation systems (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: In this communication, a comprehensive thermodynamic model for exergy analysis of a passive solar distillation system is presented. Temperatures of basin-liner, saline water body and inner and outer glass cover are estimated theoretically with the help of a computer program using a set of typical design and operating parameters. Energy and exergy analysis of a single-effect, single-slope horizontal passive solar still has been carried out under climatic conditions of India. It has been shown that the passive solar still can produce 4.17 l/m 2 of freshwater daily. Energy and exergy efficiency of the solar still are 30.42 and 4.93%, respectively. Causes, quantity and place of exergy destruction have also been explored for further research and improvement in the design and performance of solar stills. Exergy destruction or irreversibility in the process of each component, i.e. basin-liner, saline water body and glass cover, has been evaluated as 3353, 1633 and 362 W/m 2 , respectively, corresponding to the total solar exergy input of 6958 W/m 2 on a typical day. Their corresponding exergy efficiencies are found to be 3.91, 17.67 and 42.36%. The global exergy efficiency of the solar still is also estimated as 23.14%, taking these exergy destructions into account. The basin-liner is identified as the component around which there is highest possibility of improvement.
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    Experimental study of a capillary pumped loop in comparison with the prediction of a 3D CFD (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: A comparison is presented between experimental and numerical results regarding the operation of a capillary pumped loop evaporator. Two cylindrical evaporators were tested, with different heated porous lengths, 20 and 40 mm, respectively. Both have 22 mm external diameter, 9 mm porous thickness and 80 mm porous length. The working liquid was water. The loop was made from copper tubes and the evaporator from copper porous wick covered with aluminum with grooves formed in the inner surface. All tests took place on a horizontal level using heat load applied to the evaporator surface from an 85-W electric resistance. The experimental measurements were compared with the predictions of a three-dimensional CFD model of the evaporator and were found to be in satisfactory agreement. For the 20-mm wick heated length evaporator CFD model with water initial temperature of 20°C the divergence with the experimental pressure drop mean value was 0 Pa for volume flow rates between 0.4 and 0.6 l/min and 50 Pa for the rest of the values. For 30°C the divergence was 0 Pa 〈0.4 l/min and 50 Pa for larger flow rates. Moreover, for 40°C the difference was up to 50 Pa from 0 to 0.9 l/min. In every case predictions were below the wick capillary limit. The computed outflow temperature presented a maximum difference of 1.5% compared with the experimental data, which is very satisfying. On the other hand, the predictions of the evaporator CFD model with a 40-mm wick heated length were even better.
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    A feasible energy-saving analysis of a new system for CO2 cryogenic capture (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: A new CO 2 cryogenic capture and liquefaction system has been proposed previously in order to separate CO 2 from exhausted gases and make it as a resource for industry. This system combines CO 2 cryogenic capture with N 2 /O 2 separation together. Its energy consumption is lower than the traditional amine solution capture process as theoretical analysis. In this study, the simulation of the proposed system with several improvements was carried out aiming to reduce the energy consumption further. Many heat exchangers were introduced and the heat exchanger arrangements were optimized to recycle the refrigeration capacity from the returned N 2 after the N 2 /O 2 separation. The discharge pressure of mixture gas from the compressor was reduced from 10 to 3.493 MPa. The simulation results showed that the compression work could be greatly reduced and the energy consumption of CO 2 capture in this new system after these improvements reached 2.884 GJ/ton CO 2 . The new system is promising because not only liquid or solid CO 2 could be produced but also N 2 and O 2 could be separated.
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    Spanish photovoltaic learning curve (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: Learning by doing, or learning through market experience, reduces costs for energy production technologies. This phenomenon is modelled by using experience curves which reflect the changes in the cost of the technology as it becomes increasingly used. This article calculates the Spanish photovoltaic (PV) learning curve over the period 2001–12 by using cost data from the PV sector itself (installers, distributors and even engineers) and determines the accuracy of the obtained progress ratio by using both the coefficient of determination R 2 and also the error PR , which is directly determined from fitting the data. The results show a curve with a strong structural change in the speed of cost reduction in October 2009.
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    An innovative psychometric solar-powered water desalination system (2016)
    Oxford University Press
    Details
    Publication Date: 2016-05-27
    Description: Important advances have been made in solar water desalination technology but their wide application is restricted by relatively high capital and running costs. Until recently, solar concentrator collectors had usually been employed to distill water in compact desalination systems. Currently, it is possible to replace these collectors by the more efficient evacuated tube collectors, which are now widely available on the market at lower prices. This paper describes the results of experimental and theoretical investigations of the operation of a novel small-scale solar water desalination technology using the psychometric humidification and dehumidification process coupled with a heat pipe evacuated tube solar collector with an aperture area of ~1.73 m 2 . Solar radiation during spring in the Middle East was simulated by an array of halogen floodlights. A synthetic brackish water solution was used for the tests and its total dissolved solids (TDSs) and electrical conductivity were measured. A mathematical model was developed to describe the system's operation. A computer program was written to solve the system of governing equations to perform the theoretical calculations of the humidification and dehumidification processes. The experimental and theoretical values for the total daily distillate output were found to be closely correlated. The test results demonstrate that, at temperatures of 55–60°C, the system produces ~5–6 kg/h of clean water with a high desalination efficiency. Following the experimental calibration of the mathematical model, it was demonstrated that the performance of the system could be improved to produce a considerably higher amount of fresh water.
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    Thermal analysis of PCM-filled glass windows in hot summer and cold winter area (2016)
    Oxford University Press
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    Publication Date: 2016-05-27
    Description: Phase change material (PCM)-filled glass window was suitable for absorbing or releasing more heat than conventional glass window. Comparisons of thermal performance between PCM-filled glass windows and insulated glass windows (double glass windows filled with dry air and surrounded by sealing strips) were presented in this paper. A 3D unsteady model was built in FLUENT to obtain the internal and external surface temperature fluctuations of these windows in 48 h. Compared with insulated glass windows, thermal performance (especially the thermal regulation effect) of double glass windows filled with Na 2 SO 4 ·10H 2 O was quite satisfactory in sunny days of summer, while double glass windows filled with CaCl 2 ·6H 2 O had a better thermal performance in overcast and rainy days of summer. Because the phase change temperature of these PCM is higher than the ambient temperature in winter, the thermal regulation effects of them were not as good as expected.
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    Simultaneous synthesis of heat exchanger network with the non-isothermal mixing (2016)
    Oxford University Press
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    Publication Date: 2016-05-27
    Description: Optimization of heat exchanger network is attributed to improving the process industrial energy utilization ratio. Energy consumption reduction plays an important role in the low-carbon economic development. Several synthesis approaches for heat exchanger network have been proposed and extended during the last three decades. With the evolution of the computer technology, the simultaneous synthesis method via mathematic programming attracts a great deal of attention worldwide. However, some difficulties still need to be overcome, for instance, model simplification and computational complexity. In this work, the simultaneous stage-wise synthesis model without the assumption of isothermal mixing is presented and implemented using effective initialization strategies and a novel two-level algorithm. Three case studies illustrated the better performance of the initialization strategies and two-level algorithm for heat exchanger network synthesis problems, considering non-isothermal mixing.
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    Capturing atmospheric carbon: biological and nonbiological methods (2016)
    Oxford University Press
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    Publication Date: 2016-05-27
    Description: Atmospheric carbon dioxide is one of the primary greenhouse gases on earth and its continuous emission by manmade activities is leading to a rise in atmospheric temperature. On the other hand, various natural phenomena exist that contribute to the sequestration of atmospheric carbon dioxide, i.e. its capture and long-term storage. These phenomena include oceanic, geological and chemical processes happening on earth. In addition to the above-mentioned nonbiological methods, various biological methods viz. soil carbon sequestration and phytosequestration have also been contributing to fixation of atmospheric carbon. Phytosequestration is mainly performed by several photosynthetic mechanisms such as C 3 , C 4 and crassulacean acid metabolism (CAM) pathways of plants, carboxysomes of cyanobacteria and pyrenoids of microalgae. For an effective mitigation of global climate change, it is required to stabilize the CO 2 concentration to viable levels. It requires various permutations and combinations of naturally existing and engineering strategies. Although numerous strategies are in commodious use in the present times, the issues of sustainability and long-term stability still exist. We present an overview of the natural and manmade biological and nonbiological processes used today to reduce atmospheric CO 2 levels and discuss the scope and limitations of each of them.
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    Performance of U-tube solar water heater with vertical and inclined panels (2016)
    Oxford University Press
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    Publication Date: 2016-05-27
    Description: A conventional natural convection flat plate solar collector needs to be placed at an incline to the horizontal and exposed to the sun in order for the solar hot water heater system to work. This arrangement is satisfactory where there is ample roof top space to locate the collector and storage tank. In a high-rise apartment, space is at a premium and also the hot-water recticulation requires long lengths of piping to distribute the hot water supply to the individual apartment. Most every modern high-rise apartment has a balcony facing outward from the wall structure. Balcony-type solar water heaters (SWHs) are catching up fast in China. Their performance would depend on collector and storage tank designs and sizes, weather conditions (solar radiation intensity and ambient temperature) and direction in which the balconies are facing. This article compares the outdoor performance of two SWH systems incorporating the evacuated glass U-tube solar collectors operating under natural convection. The panels were tested in both the vertical and inclined positions using the same tank but at different times of the year. It was found that the inclined panel system performed better than the system with the vertical panel system.
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    Design and commission a zero-carbon building for hot and humid climate (2016)
    Oxford University Press
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    Publication Date: 2016-05-27
    Description: The Construction Industry Council (CIC) Zero-Carbon Building is a net zero-carbon building that was designed for local hot and humid climate of sub-tropical Hong Kong. Over 80 sustainability features of the architecture and building systems have considered the life-cycle carbon emissions, including the embodied carbon of construction materials, emissions associated with the construction process, the 50-years of operation and decommission of the building. The total life-cycle carbon emission was off-set by on-site renewable energy generated by photovoltaics (PV) and bio-diesel combined cooling heating and power (CCHP) system. To optimise the design, a series of climate-responsive strategies on passive architecture were applied to the construction of the building. These include the high-performance facade, effective air tightness and optimised window design that allows the application of natural ventilation and daylighting. Reduction of 20% energy demand was achieved by these passive designs. To further lower the carbon emission on operation, energy-efficient air-conditioning (A/C) systems using desiccant dehumidification, underfloor air supply and radiant cooling have also contributed on achieving an ultralow energy use value. Amalgamated saving of these passive and active systems are over 45% when compared with the design per existing local building energy codes.
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    Sap flow as a key trait in the understanding of plant hydraulic functioning (2015)
    Oxford University Press
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    Publication Date: 2015-04-30
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Water storage dynamics in the main stem of subtropical tree species differing in wood density, growth rate and life history traits (2015)
    Oxford University Press
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    Publication Date: 2015-04-30
    Description: Wood biophysical properties and the dynamics of water storage discharge and refilling were studied in the trunk of canopy tree species with diverse life history and functional traits in subtropical forests of northeast Argentina. Multiple techniques assessing capacitance and storage capacity were used simultaneously to improve our understanding of the functional significance of internal water sources in trunks of large trees. Sapwood capacitances of 10 tree species were characterized using pressure–volume relationships of sapwood samples obtained from the trunk. Frequency domain reflectometry was used to continuously monitor the volumetric water content in the main stems. Simultaneous sap flow measurements on branches and at the base of the tree trunk, as well as diurnal variations in trunk contraction and expansion, were used as additional measures of stem water storage use and refilling dynamics. All evidence indicates that tree trunk internal water storage contributes from 6 to 28% of the daily water budget of large trees depending on the species. The contribution of stored water in stems of trees to total daily transpiration was greater for deciduous species, which exhibited higher capacitance and lower sapwood density. A linear relationship across species was observed between wood density and growth rates with the higher wood density species (mostly evergreen) associated with lower growth rates and the lower wood density species (mostly deciduous) associated with higher growth rates. The large sapwood capacitance in deciduous species may help to avoid catastrophic embolism in xylem conduits. This may be a low-cost adaptation to avoid water deficits during peak water use at midday and under temporary drought periods and will contribute to higher growth rates in deciduous tree species compared with evergreen ones. Large capacitance appears to have a central role in the rapid growth patterns of deciduous species facilitating rapid canopy access as these species are less shade tolerant than evergreen species.
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    A portable NMR sensor to measure dynamic changes in the amount of water in living stems or fruit and its potential to measure sap flow (2015)
    Oxford University Press
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    Publication Date: 2015-04-30
    Description: Nuclear magnetic resonance (NMR) and NMR imaging (magnetic resonance imaging) offer the possibility to quantitatively and non-invasively measure the presence and movement of water. Unfortunately, traditional NMR hardware is expensive, poorly suited for plants, and because of its bulk and complexity, not suitable for use in the field. But does it need to be? We here explore how novel, small-scale portable NMR devices can be used as a flow sensor to directly measure xylem sap flow in a poplar tree ( Populus nigra L.), or in a dendrometer-like fashion to measure dynamic changes in the absolute water content of fruit or stems. For the latter purpose we monitored the diurnal pattern of growth, expansion and shrinkage in a model fruit (bean pod, Phaseolus vulgaris L.) and in the stem of an oak tree ( Quercus robur L.). We compared changes in absolute stem water content, as measured by the NMR sensor, against stem diameter variations as measured by a set of conventional point dendrometers, to test how well the sensitivities of the two methods compare and to investigate how well diurnal changes in trunk absolute water content correlate with the concomitant diurnal variations in stem diameter. Our results confirm the existence of a strong correlation between the two parameters, but also suggest that dynamic changes in oak stem water content could be larger than is apparent on the basis of the stem diameter variation alone.
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    Influence of stem temperature changes on heat pulse sap flux density measurements (2015)
    Oxford University Press
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    Publication Date: 2015-04-30
    Description: While natural spatial temperature gradients between measurement needles have been thoroughly investigated for continuous heat-based sap flow methods, little attention has been given to how natural changes in stem temperature impact heat pulse-based methods through temporal rather than spatial effects. By modelling the theoretical equation for both an ideal instantaneous pulse and a step pulse and applying a finite element model which included actual needle dimensions and wound effects, the influence of a varying stem temperature on heat pulse-based methods was investigated. It was shown that the heat ratio (HR) method was influenced, while for the compensation heat pulse and T max methods changes in stem temperatures of up to 0.002 °C s –1 did not lead to significantly different results. For the HR method, rising stem temperatures during measurements led to lower heat pulse velocity values, while decreasing stem temperatures led to both higher and lower heat pulse velocities, and to imaginary results for high flows. These errors of up to 40% can easily be prevented by including a temperature correction in the data analysis procedure, calculating the slope of the natural temperature change based on the measured temperatures before application of the heat pulse. Results of a greenhouse and outdoor experiment on Pinus pinea L. show the influence of this correction on low and average sap flux densities.
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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    Role of hydraulic and chemical signals in leaves, stems and roots in the stomatal behaviour of olive trees under water stress and recovery conditions (2015)
    Oxford University Press
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    Publication Date: 2015-04-30
    Description: The control of plant transpiration by stomata under water stress and recovery conditions is of paramount importance for plant performance and survival. Although both chemical and hydraulic signals emitted within a plant are considered to play a major role in controlling stomatal dynamics, they have rarely been assessed together. The aims of this study were to evaluate (i) the dynamics of chemical and hydraulic signals at leaf, stem and root level, and (ii) their effect on the regulation of stomatal conductance ( g s ) during water stress and recovery. Measurements of g s , water potential, abscisic acid (ABA) content and loss of hydraulic functioning at leaf, stem and root level were conducted during a water stress and recovery period imposed on 1-year-old olive plants ( Olea europaea L.). Results showed a strong hydraulic segmentation in olive plants, with higher hydraulic functioning losses in roots and leaves than in stems. The dynamics of hydraulic conductance of roots and leaves observed as water stress developed could explain both a protection of the hydraulic functionality of larger organs of the plant (i.e., branches, etc.) and a role in the down-regulation of g s . On the other hand, ABA also increased, showing a similar pattern to g s dynamics, and thus its effect on g s in response to water stress cannot be ruled out. However, neither hydraulic nor non-hydraulic factors were able to explain the delay in the full recovery of g s after soil water availability was restored.
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    A new type of vulnerability curve: is there truth in vine? (2015)
    Oxford University Press
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    Publication Date: 2015-04-30
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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  • 99
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    Simulating nectarine tree transpiration and dynamic water storage from responses of leaf conductance to light and sap flow to stem water potential and vapor pressure deficit (2015)
    Oxford University Press
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    Publication Date: 2015-04-30
    Description: For isohydric trees mid-day water uptake is stable and depends on soil water status, reflected in pre-dawn leaf water potential ( pd ) and mid-day stem water potential ( md ), tree hydraulic conductance and a more-or-less constant leaf water potential ( l ) for much of the day, maintained by the stomata. Stabilization of l can be represented by a linear relationship between canopy resistance ( R c ) and vapor pressure deficit ( D ), and the slope ( B D ) is proportional to the steady-state water uptake. By analyzing sap flow (SF), meteorological and md measurements during a series of wetting and drying ( D / W ) cycles in a nectarine orchard, we found that for the range of md relevant for irrigated orchards the slope of the relationship of R c to D , B D is a linear function of md . R c was simulated using the above relationships, and its changes in the morning and evening were simulated using a rectangular hyperbolic relationship between leaf conductance and photosynthetic irradiance, fitted to leaf-level measurements. The latter was integrated with one-leaf, two-leaf and integrative radiation models, and the latter gave the best results. Simulated R c was used in the Penman–Monteith equation to simulate tree transpiration, which was validated by comparing with SF from a separate data set. The model gave accurate estimates of diurnal and daily total tree transpiration for the range of md s used in regular and deficit irrigation. Diurnal changes in tree water content were determined from the difference between simulated transpiration and measured SF . Changes in water content caused a time lag of 90–105 min between transpiration and SF for md between –0.8 and –1.55 MPa, and water depletion reached 3 l h –1 before noon. Estimated mean diurnal changes in water content were 5.5 l day –1  tree –1 at md of –0.9 MPa and increased to 12.5 l day –1  tree –1 at –1.45 MPa, equivalent to 6.5 and 16.5% of daily tree water use, respectively. Sixteen percent of the dynamic water volume was in the leaves. Inversion of the model shows that md can be predicted from D and R c , which may have some importance for irrigation management to maintain target values of md . That relationship will be explored in future research.
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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    Grain Promotion and Food Consumption: Analysis of Chinese Provincial Data (2015)
    Oxford University Press
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    Publication Date: 2015-05-12
    Description: China has long struggled to achieve food security. In the era of a planned economy, local self-sufficiency was dictated by policy. With China's transition to a market economy, however, different policy schemes have been utilized, with greater emphasis placed on the role of market forces, especially in conjunction with China's accession to the World Trade Organization in 2001. Nevertheless, self-sufficiency in grain production remains a deeply rooted goal, and interventionist measures geared towards its achievement are still viewed as the most direct and effective means of food security. This paper examines how the well-being of China's rural population, proxied by measures of food consumption, is affected by the promotion of grain production. Our findings suggest that targeted households bear a disproportionate burden of food security policy, as it is currently implemented.
    Keywords: O12 - Microeconomic Analyses of Economic Development, Q12 - Micro Analysis of Farm Firms, Farm Households, and Farm Input Markets, Q18 - Agricultural Policy ; Food Policy
    Print ISSN: 2040-5790
    Electronic ISSN: 2040-5804
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Economics
    Published by Oxford University Press
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