ALBERT

Description: Aims Afforestation causes important alterations in SOM content and composition that affect the soil functions and C balance. The aim of this study was to identify the mechanisms that determine the changes in SOM composition following afforestation of grasslands. Methods The study included 4 chronosequences and 5 paired plots comprising pastures and land afforested with Pinus radiata . The SOM was characterized by 13 C CP-MAS NMR spectroscopy and differential scanning calorimetry. Results During the first 10–20 year after afforestation, the changes in SOM content varied from slight gains to large losses (〉40 %). The analyses revealed that even SOM compounds considered resistant to decomposition were degraded during this time. The SOM gains, observed 20 year after stand establishment, were favoured by the higher recalcitrance of pine litter and possibly by soil acidification. The concentrations of most SOM compounds, particularly the stable compounds, were higher at the end of the rotation. The low degree of protection, along with the favourable climatic conditions, may also explain the rapid decomposition of SOM, including resistant compounds, in these soils. DSC analysis complemented the information about SOM composition provided by other techniques. Conclusions The accumulation of stable SOM compounds at the end of the rotation suggests a longer soil C turnover in these afforested soils, which may alleviate the gradual loss of SOC in intensively managed forest soils.

Description: Background and aims Plant nutrient uptake from coarse soil (2–4 mm diameter) has been demonstrated for only a limited number of nutrients, and the nutritional contribution of coarse soil when present with fine soil (material 〈2 mm diameter) in realistic ratios is unknown. We conducted a seedling pot trial to investigate the functional relevance of this soil fraction to plant nutrition. Methods Fine soil was mixed with either coarse soil, or the equivalent volume of inert glass chips, in ratios identical to those occurring naturally in soil sampled from two depths at each of two sites. Seedlings of Nothofagus solandri var. cliffortioides and Weinmannia racemosa were planted in the soil mixtures and harvested after 9 months. Results The content of nitrogen, phosphorous, potassium, magnesium and other elements in the above ground seedling tissue was significantly increased by the presence of coarse soil. The coarse soil fraction also contributed proportionally much more to plant nutrient uptake than fine soil on a mass per mass basis. Conclusions Coarse soil is excluded from conventional soil analysis, so is possible that soil nutrient capital is systematically underestimated. This has implications for land management and studies of plant dynamics in relation to nutrient supply.

Description: How do local topological changes affect the global operation and stability of complex supply networks? Studying supply networks on various levels of abstraction, we demonstrate that and how adding new links may not only promote but also degrade stable operation of a network. Intriguingly, the resulting overloads may emerge remotely from where such a link is added, thus resulting in nonlocal failures. We link this counter-intuitive phenomenon to Braess’ paradox originally discovered in traffic networks. We use elementary network topologies to explain its underlying mechanism for different types of supply networks and find that it generically occurs across these systems. As an important consequence, upgrading supply networks such as communication networks, biological supply networks or power grids requires particular care because even adding only single connections may destabilize normal network operation and induce disturbances remotely from the location of structural change and even global cascades of failures.

Description: Structural and magnetic transitions of Ni 47.5- x Co x Mn 37.5 Sn 15 ( x  = 0, 1, 2 and 3.5) alloys were confirmed and studied by magnetic and resistivity measurements. Though a large magnetic entropy change ( Δ S M ) ~ 9.5 J/kg K was obtained for x  = 3.5 due to a change of only 1.5 T magnetic field, hysteresis losses limited its refrigerant capacity to a significant extent. A maximum –69% magnetoresistance was obtained due to a structural transition in the same sample in presence of 8 T field. It was found that the same material can be used for practical applications within a wide range of temperature as it shows large magnetoresistance at remote temperatures far below from its structural transition point.

Description: We investigate the dynamical interplay between magnetic and ferroelectric orders in a multiferroics with distorted spiral order. We find that the combing effect of the distortion of the spiral order and the effective spin anisotropy induced by the spin-lattice coupling results in the lifting of the degenerate gapped mode at the ordering wave vector, which is qualitatively in agreement with the experimental observations. In analogy to the perfect spiral spin structure, the electromagnon can be assigned to spin wave mode of the distorted helimagnet at the ordering wave vector. The electromagnon in the distorted helimagnets is also affected by the helix distortion which can be experimentally controlled.

Description: We report a study on thermodynamic properties of a two-dimensional electron gas confined in a sector of a circular cylinder immersed in a dc magnetic field perpendicular to its axis. This field configuration produces on the electrons in the curved surface, effects similar to a non-homogeneous magnetic field on a flat system. We study these effects by calculating the energy spectra for different curvature radius and symmetries of the magnetic field with respect to the surface. The analysis of the density of states, chemical potential and specific heat of these systems helps to understand the correlation between the externally controlled symmetry and their physical properties.

Description: During the past few years, users’ membership in the online system (i.e. the social groups that online users joined) were widely investigated. Most of these works focus on the detection, formulation and growth of online communities. In this paper, we study users’ membership in a coupled system which contains user-group and user-object bipartite networks. By linking users’ membership information and their object selection, we find that the users who have collected only a few objects are more likely to be “influenced” by the membership when choosing objects. Moreover, we observe that some users may join many online communities though they collected few objects. Based on these findings, we design a social diffusion recommendation algorithm which can effectively solve the user cold-start problem. Finally, we propose a personalized combination of our method and the hybrid method in [T. Zhou, Z. Kuscsik, J.G. Liu, M. Medo, J.R. Wakeling, Y.C. Zhang, Proc. Natl. Acad. Sci. 107 , 4511 (2010)], which leads to a further improvement in the overall recommendation performance.

Description: Realistic models of α -helix proteins are composed of three covalently-bonded strands, each of which is made of hydrogen-bonded peptide units. The modulational instability analysis of such complex molecular systems is carried out in this work. We show that the exciton-vibron coupling parameter contributes to the explosion and expansion of instability regions. The right choice of the modulational instability parameters leads to the formation of excitonic modulated pulse-like structures. It is argued that covalent bonds are compressed during the process of energy transport, while hydrogen bond oscillations display regular trains of breather-like objects. We also argue that the probable way of energy transport, from modulational instability, is through hydrogen bonds.

Description: Background and aims Lateral tree-scale variability in plantations should be taken into account when scaling up from point samples, but appropriate methods for sampling and calculation have not been defined. Our aim was to define and evaluate such methods. Methods We evaluated several existing and new methods, using data for throughfall, root biomass and soil respiration in mature oil palm plantations with equilateral triangular spacing. Results Three ways of accounting for spatial variation within the repeating tree unit (a hexagon) were deduced. For visible patch patterns, patches can be delineated and sampled separately. For radial patterns, measurements can be made in radial transects or a triangular portion of the tree unit. For any type of pattern, including unknown patterns, a triangular sampling grid is appropriate. In the case studies examined, throughfall was 79 % of rainfall, with 95 % confidence limits being 62 and 96 % of rainfall. Root biomass and soil respiration, measured on a 35-point grid, varied by an order of magnitude. In zones with steep gradients in parameters, sampling density has a large influence on calculated mean values. Conclusions The methods defined here provide a basis for representative sampling and calculation procedures in studies requiring scaling up from point sampling, but more efficient methods are needed.

Description: A novel allotrope of carbon with P 2/ m symmetry was identified during an ab initio minima-hopping structural search which we call M 10-carbon. This structure is predicted to be more stable than graphite at pressures above 14.4 GPa and consists purely of s p 3 bonds. It has a high bulk modulus and is almost as hard as diamond. A comparison of the simulated X-ray diffraction pattern shows a good agreement with experimental results from cold compressed graphite.

Description: It is shown that the defect-deformational (DD) cooperative nucleation of ordered ensembles of nanoparticles on isotropic surfaces of solids with the participation of quasi-Rayleigh waves can be described by a closed two-dimensional nonlinear DD equation of the Kuramoto-Sivashinsry (KS) type. A solution to the linearized DDKS equation describes the threshold appearance of the periodic surface strain modulation accompanied by the simultaneous formation of adatom (surface defect) piles at extrema of the surface strain. Numerical solutions to the DDKS equation in linear and nonlinear regimes describe the formation of three types of surface structures of adatom piles (clusters): lamellar-like structures, cellular disordered and hexagonal ordered ones. In the well-developed nonlinear regime, generated ensembles of nanoparticles become trimodal regarding their size distribution due to the generation of the second harmonics, degenerate parametric decay and summation of wavevectors of DD gratings taking part in the DD selforganization. The selforganizing periodic cellular DD surface structure can serve as a selforganized template for the subsequent growth of nanoparticles in the processes of atoms deposition.

Description: Background Plants must acquire at least 14 mineral nutrients from the soil to complete their life cycles. Insufficient availability or extreme high levels of the nutrients significantly affect plant growth and development. Plants have evolved a series of mechanisms to adapt to unsuitable growth conditions where nutrient levels are too low or too high. microRNAs (miRNAs), a class of small RNAs, are known to mediate post-transcriptional regulation by transcript cleavage or translational inhibition. Besides regulating plant growth and development, miRNAs are well documented to regulate plant adaptation to adverse environmental conditions including nutrient stresses. Scope In this review, we focus on recent progress in our understanding of how miRNAs are involved in plant response to stresses resulting from deficiency in nutrients, such as nitrogen, phosphorus, sulfur, copper and iron, as well as toxicities from heavy metal ions. Conclusions Accumulated evidence indicates that miRNAs play critical roles in sensing the abundance of nutrients, controlling nutrient uptake and phloem-mediated long-distance transport, and nutrient homeostasis. miRNAs act as systemic signals to coordinate these physiological activities helping plants respond to and survive nutrient stresses and toxicities. Knowledge about how miRNAs are involved in plant responses to nutrient stresses promise to provide novel strategies to develop crops with improved nutrient use efficiency which could be grown in soils with either excessive or insufficient availability of nutrients.

Description: Ab initio computational methods are used to study the relevance of van der Waals interactions in the case of a hydrogen molecule adsorption on the Ru(0001) surface. In addition to the clean surface, the effects of ruthenium adatom and vacancy on the process are studied. The adsorption characteristics are analyzed in terms of two dimensional cuts of the potential energy surface (PES). Based on the earlier studies for such systems, we mostly concentrate on the trajectories where the hydrogen molecule approaches the surface in parallel orientation. The results indicate that for a clean Ru(0001) the calculations applying the non-local van der Waals potentials yield higher barriers for the dissociation of the H 2 molecule. Of the high symmetry sites on Ru(0001), the top site is found to be the most reactive one. The vacancy and ruthenium adatom sites exhibit high dissociation barriers compared with the clean surface.

Description: In the present paper, the site-percolation problem corresponding to linear k -mers (containing k identical units, each one occupying a lattice site) on a simple cubic lattice has been studied. The k -mers were irreversibly and isotropically deposited into the lattice. Then, the percolation threshold and critical exponents were obtained by numerical simulations and finite-size scaling theory. The results, obtained for k ranging from 1 to 100, revealed that (i) the percolation threshold exhibits a decreasing function when it is plotted as a function of the k -mer size; and (ii) the phase transition occurring in the system belongs to the standard 3D percolation universality class regardless of the value of k considered.

Description: The nonlinear Landau-Zener tunneling of a Bose-Fermi mixture in a double-well potential is studied in the present paper. The effect of interaction parameters on bosonic and fermionic tunneling probability is studied for the mixture of 40 K- 87 Rb. The tunneling phenomena of the system can be controled by adjusting sweeping rate, intraspecies interaction, interspecies interaction and the numbers of bosons and fermions. It is noted that there are three different regions in phase diagram: self-trapping (ST), complete tunneling (CT) and incomplete tunneling (ICT).

Description: Background and aims (i) compare the concentrations of total polyphenols (TP) and condensed tannins (CT), and CT profiles in different organs of mature trees and seedlings of eight true mangrove species in Hong Kong; (ii) examine the antioxidant activities of CT and (iii) relate the non-enzymatic antioxidative defence system with the vertical zonation pattern of mangrove species. Methods Mature trees and seedlings of eight species were collected from a Hong Kong mangrove swamp to determine TP and CT concentrations and the antioxidant activities of CT. Results According to TP concentrations, the true mangrove species could be broadly classified into three groups, (i) Lumnitzera racemosa and Aegiceras corniculatum 〉 (ii) Heritiera littoralis , Excoecaria agallocha , Bruguiera gymnorrhiza and Kandelia obovata 〉 (iii) Acanthus ilicifolius and Avicennia marina . The last two are pioneer species in the most foreshore location. They also had significantly lower antioxidant activities, CT concentrations and different CT profiles than the other six species in mid- and low-tides. Conclusions Classification of the eight true mangrove species into three groups based on polyphenols was similar to their vertical zonation from land to sea. The relationships between these antioxidants and zonation should be further verified by transplantation studies.

Description: Background and aims Soil phosphorus (P) indices that have been originally developed and applied to agricultural soils for predicting P uptake by plants were examined in a pot experiment to determine the most suitable index for P availability in bauxite-processing residue sand (BRS). Methods Pot trials with ryegrass were established using BRS that had been amended with various organic (greenwaste compost, biochar and biosolids) and inorganic (zeolite) materials and different levels of di-ammonium phosphate fertiliser. Soil P availability indices tested included anion-exchange membrane (AEM-P), 0.01 M calcium chloride (CaCl 2 -P), Colwell-P, and Mehlich 3-P. Results AEM-P was found to most closely reflect the available P status in BRS across all treatments, and had the strongest associations with plant P uptake compared to Colwell-P, Mehlich 3-P and CaCl 2 -P. AEM-P was more closely correlated with P uptake by ryegrass than other P indices, while Colwell-P was closely related to leaf dry matter. Interestingly, a strong inverse relationship between plant indices and pH in BRS growth media was observed, and an adequate level of plant P uptake was found only in 15 year-old rehabilitated BRS with pH 〈 8.0. Conclusions AEM-P was found to be the most suitable index for evaluating P availability in highly alkaline BRS and pH was an important parameter affecting uptake of P by ryegrass. Importantly, time is required (〉 5 years) before improved uptake of P by plants can be observed in rehabilitated residue sand embankments.

Description: Background & aims Herbivore-driven changes to soil properties can influence the decomposition rate of organic material and therefore soil carbon cycling within grassland ecosystems. We investigated how aboveground foraging mammalian and invertebrate herbivores affect mineral soil decomposition rates and associated soil properties in two subalpine vegetation types (short-grass and tall-grass) with different grazing histories. Methods Using exclosures with differing mesh sizes, we progressively excluded large, medium and small mammals and invertebrates from the two vegetation types in the Swiss National Park (SNP). Mineral soil decomposition rates were assessed using the cotton cloth (standard substrate) method between May and September 2010. Results Decomposition displayed strong spatio-temporal variability, best explained by soil temperature. Exclusion of large mammals increased decomposition rates, but further exclusion reduced decomposition rates again in the lightly grazed (tall-grass) vegetation. No difference among treatments was found in the heavily grazed (short-grass) vegetation. Heavily grazed areas had higher decomposition rates than the lightly grazed areas because of higher soil temperatures. Microbial biomass carbon and soil C:N ratio were also linked to spatio-temporal decomposition patterns, but not to grazing history. Conclusions Despite altering some of the environmental controls of decomposition, cellulose decomposition rates in the SNP’s subalpine grasslands appear to be mostly resistant to short-term herbivore exclusion.

Description: Background Our recent publication (Warren et al., Plant Soil 366:683–693, 2013 ) described how pulses of deuterium oxide (D 2 O) or H 2 O combined with neutron radiography can be used to indicate root water uptake and hydraulic redistribution in maize. This technique depends on the large inherent differences in neutron cross-section between D and H atoms resulting in strong image contrast. Scope and Conclusions However, as illustrated by Carminati and Zarebanadkouki ( 2013 ) there can be a change in total water content without a change in contrast simply by a change in the relative proportions of D 2 O and H 2 O. We agree with their premise and detailed calculations (Zarebanadkouki at al. 2012 , 2013 ), and present further evidence that mixing of D 2 O and H 2 O did not confound evidence of hydraulic redistribution in our study.

Description: Background and aims The growth of green plants depends not only on photosynthesis, but also on the successful remobilization and translocation of seed phosphorus (P) reserves to the vegetative parts of the developing seedling during early growth. Remobilization and photosynthesis are therefore two parallel and co-coinciding processes involved in better seedling establishment and early growth. Methods A study was conducted to evaluate the priority of developing maize seedlings to translocate the remobilized seed P reserves and external P uptake to seedling root and shoot sinks during 4 weeks of early growth. Two fluxes of P in growing seedlings, one from seed remobilized P reserves and one from external P uptake, were distinguished by labelling external nutrient solution P with 32 P. Results The seedling phytomass was equally distributed between seedling roots and shoots for 530 cumulated degree days after sowing. Seedlings partitioned up to 71 % of P from seed reserves and up to 68 % of P acquired from the nutrient solution, to the shoots, depending on the seed P content and P concentration in the nutrient solution. It appears that accumulation of P slows down in seedling roots corresponds to the translocative functions of root P towards shoots for start of photosynthesis. Conclusions Our results suggest that the major part of seed P reserves and external P uptake were used in early development of the seedling and the preferred sink was seedling shoots.

Description: Background and aims Nickel (Ni) has become a major heavy metal contaminant. The form of nitrogen nutrition remarkably affects IRT1 expression in roots. IRT1 has an activity of transporting Ni 2+ into root cells. Therefore, nitrogen-form may affect Ni accumulation and toxicity in plants. The assumption was investigated in this study. Methods The Arabidopsis plants were treated in Ni-contained growth solutions with either nitrate (NO 3 − ) or ammonium (NH 4 + ) as the sole N source. After 7-day treatments, Ni concentration, IRT1 expression, Ni-induced toxic symptoms and oxidative stress in plants were analyzed. Results The NO 3 − -fed plants contained a higher Ni concentration, had a greater IRT1 expression in roots, and developed more severe toxic symptoms in the youngest fully expanded leaves, compared with the NH 4 + -fed plants. The Ni-induced growth inhibition was also more significant in NO 3 − -fed plants. Interestingly, Ni exposure resulted in greater hydrogen peroxide (H 2 O 2 ) and superoxide radical (O 2 . − ) accumulations, more severe lipid peroxidation and more cell death in NO 3 − -fed plants, whereas the opposite was true for NH 4 + -fed plants. Furthermore, the Ni-enhanced peroxidase (POD) and superoxide dismutase (SOD) activities were greater in NO 3 − -fed plants Conclusion NO 3 − nutrition promotes Ni uptake, and enhances Ni-induced growth inhibition and oxidative stress in plants compared with NH 4 + nutrition.

Description: Background and aims Brassica napus has high boron (B) demand, but significant genotype differences exist with respect to B deficiency. The aim of this research was to elucidate the relationship between the different sensitivities of Brassica napus cultivars to low B stress and the characteristics of B uptake and transport to characterise the regulation of B efficiency in Brassica napus . Methods B-efficient and B-inefficient Brassica napus cultivars were used to compare the uptake and transport of B using the stable isotope 10 B tracer and grafting experiments, as well as expression of B transporters by RT-PCR. Results B-efficient cultivars have significant advantages with regard to B limitation. The B-efficient cultivar HZ showed less severe B deficiency symptoms and higher dry biomass than the B-inefficient cultivars LW and LB. Both the amount of total B and the 10 B concentration and accumulation in the shoots and roots of B-efficient HZ were higher than those of B-inefficient cultivars. In B-inefficient LW, the amount of total B and the 10 B that was transported into shoots was less than in the other three cultivars and the content and accumulation of total B and 10 B in the roots of B-inefficient LB were the lowest among all of the cultivars. When the roots of B-efficient HZ were used as stocks, the grafted plants showed B-efficient characteristics, such as mild B deficiency symptoms, and higher dry biomass and B accumulation, regardless of whether they originated from B-efficient or B-inefficient cultivars. In contrast, the grafted plants with B-inefficient LW used as stocks were B-inefficient. The expressions of BnBOR1;1c , BnBOR1;2a and BnNIP5;1 were up-regulated in roots under low B stress compared with the normal B condition. However, there was no obvious difference in the expressions of the three genes or of four other BnBOR1s between B-efficient and B-inefficient cultivars in low or normal B environments. Conclusions These results indicate that the B efficiency of Brassica napus is controlled primarily by roots, which allow more uptake and accumulation of B in B-efficient cultivars than B-inefficient cultivars in a low B environment. However the molecular mechanism regulating B efficiency in Brassica napus remains to be determined.

Description: Aims Application of carbon (C) and nitrogen (N) isotopes is an essential tool to study C and N flows in plant-soil-microorganisms systems. When targeting single plants in a community the tracers need to be added via e.g., leaf-labeling or stem-feeding approaches. In this study we: (i) investigated if bicarbonate can be used to introduce 14 C (or 13 C) into white clover and ryegrass, and (ii) compared the patterns of 14 C and 15 N allocation in white clover and ryegrass to evaluate the homogeneity of tracer distribution after two alternative labeling approaches. Methods Perennial ryegrass and white clover were pulse labeled with 15 N urea via leaf-labeling and 14 C either via a 14 CO 2 atm or with 14 C bicarbonate through leaf-labeling. Plants were sampled 4 days after labeling and prepared for bulk isotope analysis and for 14 C imaging to identify plant parts with high and low 14 C activity. Subsequently, plant parts with high and low 14 C activity were separated and analyzed for 15 N enrichment. Results Bicarbonate applied by leaf-labeling efficiently introduced 14 C into both white clover and ryegrass, although the 14 C activity in particular for white clover was found predominantly in the labeled leaf. Using 14 C imaging for identification of areas with high (hotspots) and low 14 C activity showed that 14 C was incorporated very heterogeneously both when using bicarbonate and CO 2 as expected when using pulse labeling. Subsequent analysis of 15 N enrichment in plant parts with high and low 14 C activity showed that 15 N also had a heterogeneous distribution (up to two orders of magnitude). Conclusion Bicarbonate can efficiently be used to introduce 14 C or 13 C into plant via the leaf-labeling method. Both 14 C and 15 N showed heterogeneous distribution in the plant, although the distribution of 15 N was more even than that of 14 C.

Description: Background and aim In numerous areas, rice cultivated under flooded conditions is exposed simultaneously to iron excess and arsenic contamination. The impact of these combined stresses on yield-related parameters and As distribution and speciation in various plant parts remains poorly documented. Methods Rice (cv I Kong Pao) was exposed to iron excess (125 mg L −1 Fe 2 SO 4 ), arsenic (50 and 100 μM Na 2 HAsO 4 .7H 2 O) or a combination of those stressing agents in hydroponic culture until harvest. Plant growth, yield-related parameters, non protein thiols concentration and mineral nutrition were studied in roots and shoots. Arsenic speciation was determined by high-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry. Key Results Iron excess increased As retention by the roots in relation to the development of the root iron plaque but decreased As accumulation in the shoot. Arsenic concentration was lower in the grains than in the shoots. Iron stress reduced As accumulation in the husk but not in the dehusked grains. Iron excess decreased the proportion of extractable As(III) and As(V) in the grain while it increased the proportion of extractable As(III) in the shoot. Combined stresses (Fe+As) affected plant nutrition and significantly reduced the plant yield by limiting the number of grains per plant and the grain filling. Conclusions Fe excess had an antagonist impact on shoot As concentration but an additive negative impact on several yield-related parameters. Iron stress influences both As distribution and As speciation in rice.

Description: Background and aims Intermittently frozen ground in winter is expected to disappear over large areas in the temperate zone due to ongoing climate warming. The lack of soil frost influences plant soil interactions and needs to be studied in more detail. Methods Winter soil frost was avoided by belowground heating wires in a field experiment over two subsequent winters in a temperate grassland. Soil respiration, soil nitrogen availability and plant performance (aboveground biomass, root length at two depth levels, greenness, nutrient content) were compared between “no-frost” and reference plots which underwent repeated freeze-thaw cycles in both winters. Results Soil respiration increased in the “no-frost” treatment during the warming phase (+291 %). N-availability in the upper 10 cm of the soil profile was not affected, possibly due to increased plant N accumulation during winter (+163 %), increased plant N concentration (+18 %) and increased biomass production (+31.5 %) in the growing season. Translocation of roots into deeper soil layers without changes in total root length in response to the “no-frost” treatment, however, may be a sign of nutrient leaching. Conclusions The cumulative effect on carbon cycling due to warmer soils therefore depends on the balance between increased winter carbon loss due to higher soil biotic activity and enhanced plant productivity with higher nutrient accumulation in the growing season.

Description: Aims The aims of this work were to investigate the aluminum (Al) and phosphate (P) interactions in the regulation of root system architecture of Arabidopsis thaliana seedlings and the contribution of auxin signaling in primary and lateral root growth in response to Al toxicity. Methods Detailed analyses of root system architecture and cell division were performed in Arabidopsis WT seedlings and in low phosphorus insensitive mutants lpi1 - 3 and lpr1 - 1 lpr2 - 1 in response to Al. Expression studies of P-deficiency regulated phosphate transporter AtPT2 were also conducted. The role of auxin as a mediator of root morphogenetic changes by Al was evaluated by using the auxin-signaling mutants tir1 , tir1 afb2 afb3 , and arf7 arf19 . Results Al inhibited primary root growth by affecting cell cycle progression and causing differentiation of cells in the root meristem. These effects were reduced in low phosphorus insensitive lpi1 - 3 and low phosphate resistant lpr1 - 1 lpr2 - 1 Arabidopsis mutants. Al also activated the expression of the low phosphate-induced P transporter AtPT2 in roots. Lateral root formation by Al decreased in tir1 afb2 afb3 while arf7 arf19 mutants were highly resistant to Al in both primary root inhibition and lateral root induction. Conclusions Our results suggest that lateral root formation in response to Al toxicity and P deficiency may involve common signaling mechanisms, while a pathway involving ARF7 and ARF19 is important for primary root growth inhibition by Al.

Description: Aims Litter decomposition and subsequent nutrient release play a major role in forest carbon and nutrient cycling. To elucidate how soluble or bulk nutrient ratios affect the decomposition process of beech ( Fagus sylvatica L.) litter, we conducted a microcosm experiment over an 8 week period. Specifically, we investigated leaf-litter from four Austrian forested sites, which varied in elemental composition (C:N:P ratio). Our aim was to gain a mechanistic understanding of early decomposition processes and to determine microbial community changes. Methods We measured initial litter chemistry, microbial activity in terms of respiration (CO 2 ), litter mass loss, microbial biomass C and N (C mic and N mic ), non purgeable organic carbon (NPOC), total dissolved nitrogen (TDN), NH 4 + , NO 3 - and microbial community composition (phospholipid fatty acids – PLFAs). Results At the beginning of the experiment microbial biomass increased and pools of inorganic nitrogen (N) decreased, followed by an increase in fungal PLFAs. Sites higher in NPOC:TDN (C:N of non purgeable organic C and total dissolved N), K and Mn showed higher respiration. Conclusions The C:N ratio of the dissolved pool, rather than the quantity of N, was the major driver of decomposition rates. We saw dynamic changes in the microbial community from the beginning through the termination of the experiment.

Description: Background and aims Grazing may influence nutrient cycling in several ways. In productive mountain grasslands of central Argentina cattle grazing maintain a mosaic of different vegetation patches: lawns, grazed intensively and dominated by high quality palatable plants, and open and closed tussock grasslands dominated by less palatable species. We investigated if differences in the resources deposited on soil (litter and faeces) were associated with litter decomposition rates and soil nitrogen (N) availability across these vegetation patches. Methods We compared the three vegetation patches in terms of litter and faeces quality and decomposability, annual litterfall and faeces deposition rate. We determined decomposition rates of litter and faces in situ and decomposability of the same substrates in a common garden using “litter bags”. We determined soil N availability (with resin bags) in the vegetation patches. Also, we performed a common plant substrates decomposition experiment to assess the effect of soil environment on decomposition process. This technique provides important insights about the soil environmental controls of decomposition (i.e. the sum of soil physicochemical and biological properties, and microclimate), excluding the substrate quality. Results The litter quality and faeces deposition rate were higher in grazing lawns, but the total amounts of carbon (C) and nitrogen (N) deposited on soil were higher in tussock grasslands, due to higher litterfall in these patches. The in situ decomposition rates of litter and faeces, and of the two common plant substrates were not clearly related to either grazing pressure, litterfall or litter quality (C, N, P, lignin, cellulose or hemicellulose content). In situ litter decomposition rate and soil ammonium availability were correlated with the decomposition rates of both common plant substrates. This may suggest that difference in local soil environment among patch types is a stronger driver of decomposition rate than quality or quantity of the resource that enter the soil. Conclusions Our results show that, although high grazing pressure improves litter quality and increases faeces input, the reduction in biomass caused by herbivores greatly reduces C and N input for the litter decomposition pathway. We did not find an accelerated decomposition rate in grazing lawns as proposed by general models. Our results point to soil environment as a potential important control that could mask the effect of litter quality on field decomposition rates at local scale.

Description: Background and aims Cd uptake has been shown to increase during conditions of Fe deficiency. This study tested the hypothesis that Fe-deficiency-responsive genes, particularly OsNRAMP1, play a role in the increased Cd uptake that occurs when rice is grown in aerobic soil conditions. Methods Plants were grown in aerobic or flooded soil conditions. Uptake of Cd was compared to levels of expression of candidate metal transporters and to metal ion availability in soil. Results Plants grown with intermittent soil flooding experienced a predominantly aerobic root environment and had the highest plant Cd uptake. Stronger upregulation of OsNRAMP1 was detected in plants grown in unflooded soil than in flooded soil. However, these transcriptional responses were not linked to an increase in Cd uptake. Overexpression of OsNRAMP1 was not found to increase the uptake of Cd in rice in soil or solution culture. In contrast, there were large differences in availability of Cd, Fe and Mn between flooded and aerobic soils, which were linked to changes in Cd uptake. Conclusions Aerobic soil conditions favour Cd uptake through increased Cd availability and decreased competition between Cd and Fe rather than through the increased expression of the Fe transporters themselves.

Description: Background and aims Intensive land use has led to degradation and abandonment of Portuguese oak woodlands, and subsequent shrub encroachment may have altered the spatial heterogeneity of soil C and N pools. The aim of this study was to evaluate the effects of shrub invasion on soil C and N dynamics in an oak woodland in Southern Portugal. Methods Soil was sampled beneath and outside scattered Quercus suber L. canopies, considering non-encroached areas and areas encroached by shrubs ( Cistus ladanifer L. or Cistus salviifolius L.). Results The spatial heterogeneity of soil C and N contents was mainly associated with tree presence. Outside tree canopies, the labile C pools were larger (mainly beneath C . ladanifer ) and C cycling was faster in encroached areas than in non-encroached areas. Net and gross N mineralization and urease and protease activities were also higher in encroached than in non-encroached areas; however, the metabolic quotient and the Cmicrobial/Corganic ratio were not significantly affected. Beneath the tree canopy, significant effects of encroachment included a small increase in soil labile C and the enzymatic activity beneath C . ladanifer . Conclusions The results indicate the potential capacity of shrub encroachment to accumulate soil organic C in the long term. The rate of soil C and N turnover promoted by shrub encroachment may depend on the Cistus species present.

Description: Aims Decreased expression of TaNAM genes by RNAi results in delayed senescence and decreased grain protein, iron, and zinc concentrations. Here, we determined whether NAM expression level alters onset of senescence under stress conditions, whether delayed senescence in the TaNAM -RNAi line resulted in improved tolerance to post-anthesis abiotic stress, and determined the effects of post-anthesis abiotic stress on N and mineral remobilization and partitioning to grain. Methods Greenhouse-grown WT and TaNAM -RNAi wheat were characterized in two studies:three levels of N fertility or water limitation during grain fill. Studies were conducted under both optimal and heat stress temperatures. Senescence onset was determined by monitoring flag leaf chlorophyll. Results Under optimal tempertures, TaNAM -RNAi plants had a yield advantage at lower N. TaNAM -RNAi plants had delayed senescence relative to the WT and lower grain protein and mineral concentrations, N remobilization efficiency, and partitioning of N and most minerals to grain. Conclusions Nutritional quality of TaNAM -RNAi grain was consistently lower than WT. Delayed senescence of TaNAM -RNAi plants provided a yield advantage under optimal temperatures but not under water or heat stress. Discovery of specific NAM protein targets may allow separation of the delayed senescence and nutrient partitioning traits, which could be used for improvement of wheat.

Description: Aims Nitrification inhibitors (NI) formulated on granulated ammonium sulphate nitrate (ASN) are an option to minimize nitrate leaching into ground waters and emissions of the greenhouse gas N 2 O. This paper focuses (a) on the development of an analytic enabling to extract and quantify the NI 3,4-dimethylpyrazolephosphate (DMPP), marketed since 1999. The efficiency of DMPP has been studied in laboratory and field soils. Here the DMPP analytic and the behaviour of a nitrifying bacterial consortium enriched from a field soil and exposed to zero, field applied and a 10 fold higher DMPP concentration than the recommended one for field application are in the focus. Methods For extracting DMPP quantitatively from soils a method connected to a HPLC analytic has been developed by us and was standardized in laboratory experiment with a silt clay field soil (allochtone Vega). The method is detailed described here. Its reliability has been tested in a 3 years field trial under varying cropping systems and climatic conditions asides the influence of DMPP on CO 2 −, CH 4 − and N 2 O- emissions, measured by the closed chamber method. Parallel a nitrifying bacterial consortium of the silty clay field soil was enriched and subjected to 0, the recommended DMPP concentration for field applications and a 10 times higher one. In incubation experiments the conversion of ammonium to nitrite and nitrate in presence and absence of DMPP was spectrophotometer determined and pH-shifts with a scaled litmus paper. In sacrificed flasks at the end of incubation morphological changes of the bacteria involved were studied by transmission electron microscope (TEM). Results The ammonium, nitrite and nitrate determinations and the TEM pictures show that in presence of the field applied DMPP concentration the nitrifying activity returned around 30 days later than in the control and the cells were slightly enlarged. In presence of a 10 times higher DMPP concentration a recovery was prevented. DMPP prolongs, compared with dicyandiamide (DCD), the period of nitrifiers’ inhibition and reduced N 2 O− and CO 2 − the emissions (Weiske et al., Biol Fertil Soils 34:109–117, 2001a , Nutr Cycl Agroecosys 60:57–64, b ). Conclusions With the method developed by us the stability of DMPP in agricultural soils can be satisfyingly and reproducible studied down to a detection limit of 0.01 μg DMPP g −1 dry soil. The morphological changes in the nitrifying consortium due to DMPP concentrations are in agreement with the recovery rate found by nitrite and nitrate formation.

Description: We present the exact solution, obtained by means of the Transfer Matrix (TM) method, of the 1D Hubbard model with nearest-neighbor (NN) and next-nearest-neighbor (NNN) Coulomb interactions in the atomic limit ( t  = 0). The competition among the interactions ( U , V 1 , and V 2 ) generates a plethora of T  = 0 phases in the whole range of fillings. U , V 1 , and V 2 are the intensities of the local, NN and NNN interactions, respectively. We report the T  = 0 phase diagram, in which the phases are classified according to the behavior of the principal correlation functions, and reconstruct a representative electronic configuration for each phase. In order to do that, we make an analytic limit T  → 0 in the transfer matrix, which allows us to obtain analytic expressions for the ground state energies even for extended transfer matrices. Such an extension of the standard TM technique can be easily applied to a wide class of 1D models with the interaction range beyond NN distance, allowing for a complete determination of the T  = 0 phase diagrams.

Description: The electronic structures of the Fe-doped perovskite ruthenates BaRu 1− x Fe x O 3 with x  = 0, 0.25, 0.5, 0.625, 0.75, and 1 are investigated through density-functional calculations. Large exchange splitting and small crystal field splitting are found in BaFeO 3 , and a contrary scenario can take place on BaRuO 3 as expected since the Ru atom has a highly extended 4 d orbital. The small exchange splitting and extended 4 d states are the reasons why the obtained spin magnetic moment (0.628 μ B ) is significantly lower than the spin only value (2 μ B ) for the t 2 g 3↑  t 2 g 1↓ electronic configuration for Ru 4+ ion. Further investigations suggest that Fe substitution at the Ru sites can suppress the bandwidths of Ru 4 d orbital, leading to the half-metallic behaviour in BaRu 1− x Fe x O 3 with x  = 0.625 and 0.75. The different orbital feature of the Ru 4+ ions in BaRu 0.375 Fe 0.625 O 3 is presented, which reflects the influence of Fe dopant on Ru 4 d orbitals.

Description: Current-driven domain wall dynamics is studied theoretically in the spin-valve nanostrips with parallel, perpendicular and tilted polarizers by Lagrangian formalism. In this description, the Slonczewski and field-like spin-transfer torques act as a Coulomb-type dissipation and an effective magnetic field, respectively. Considering a Walker profile, the wall behavior is governed by the dynamic equations about the center position, the out-of-plane angle, and the width of walls. It is found that the wall precesses after the steady motion breaks down for the parallel polarizer. The field-like spin-transfer torque favors a rapid increase of the steady velocity. The average velocity in the precession is nearly proportional to the current density. On the other hand, there is no precession for the perpendicular and tilted polarizers. Under the perpendicular polarizer, the wall stops when increasing current density. Moreover, there exist hysteresis and tri-stability for a large spin polarization. Under the tilted polarizer, it can be observed hysteretic, linear and nonlinear dependence of the wall velocity on the increasing current density. In the hysteresis, the wall experiences a switching of polarity or a reversal of motion.

Description: Background and aims Adequate zinc (Zn) in maize ( Zea mays L.) is required for obtaining Zn-enriched grain and optimum yield. This study investigated the impact of varying Zn fertilizer placements on Zn accumulation in maize plant. Methods Two pot experiments with same design were conducted to investigate the effect of soil Zn heterogeneity by mixing ZnSO 4 ·7H 2 O (10 mg Zn kg −1 soil on an average) in 10–15, 0–15, 25–30, 0–30, 30–60 and 0–60 cm soil layers on maize root growth and shoot Zn content at flowering stage in experiment-1, and assessing effects on grain Zn accumulation at mature stage in experiment-2. Results In experiment-1, Zn placements created a large variation in soil DTPA-Zn concentration (0.3–29.0 mg kg −1 ), which induced a systemic and positive response of root growth within soil layers of 0–30 cm; and shoot Zn content was increased by 102 %–305 % depending on Zn placements. Supply capacity of Zn in soil, defined as sum of product of soil DTPA-Zn concentration and root surface area at different soil layers, was most related to shoot Zn content ( r  = 0.82, P  〈 0.001) via direct and indirect effects according to path analysis. In experiment-2, Zn placements increased grain Zn concentration by up to 51 %, but significantly reduced the grain Zn harvest index from 50 % by control to about 30 % in average. Conclusion Matching the distribution of soil applied Zn with root by Zn placement was helpful to maximize shoot Zn content and grain Zn concentration in maize.

Description: Background and Aims Wetting-drying cycles are important environmental processes known to enhance aggregation. However, very little attention has been given to drying as a process that transports mucilage to inter-particle contacts where it is deposited and serves as binding glue. The objective of this study was to formulate and test conceptual and mathematical models that describe the role of drying in soil aggregation through transportation and deposition of binding agents. Methods We used an ESEM to visualize aggregate formation of pair of glass beads. To test our model, we subjected three different sizes of sand to multiple wetting-drying cycles of PGA solution as a mimic of root exudates to form artificial aggregates. Water stable aggregate was determined using wet sieving apparatus. Results A model to predict aggregate stability in presence of organic matter was developed, where aggregate stability depends on soil texture as well as the strength, density and mass fraction of organic matter, which was confirmed experimentally. The ESEM images emphasize the role of wetting-drying cycles on soil aggregate formation. Conclusions Our experimental results confirmed the mathematical model predictions as well as the ESEM images on the role of drying in soil aggregation as an agent for transport and deposition of binding agents.

Description: Background and aims Many plant growth-promoting endophytes (PGPE) possessing 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity can reduce the level of stress ethylene and assist their host plants cope with various biotic and abiotic stresses. However, information about the endophytic bacteria colonizing in the coastal halophytes is still very scarce. This study aims at isolating efficient ACC deaminase-producing plant growth-promoting (PGP) bacterial strains from the inner tissues of a traditional Chinese folk medicine Limonium sinense (Girard) Kuntze, a halophyte which has high economic and medicinal values grown in the coastal saline soils. Their PGP activity and effects on host seed germination and seedling growth under salinity stress were also evaluated. Methods A total of 126 isolates were obtained from the surface sterilized roots, stems and leaves of L. sinense (Girard) Kuntze. They were initially selected for their ability to produce ACC deaminase as well as other PGP properties such as production of indole-3-acetic acid (IAA), N 2 -fixation, and phosphate-solubilizing activities and subsequently identified by the 16S rRNA gene sequencing. For selected strains, seed germination, seedling growth, and flavonoids production in axenically growth L. sinense (Girard) Kuntze seedlings at different NaCl concentrations (0–500 mM) were quantified. Results Thirteen isolates possessing ACC deaminase activity were obtained. The 16S rRNA gene sequencing analysis showed them to belong to eight genera: Bacillus , Pseudomonas , Klebsiella , Serratia , Arthrobacter , Streptomyces , Isoptericola , and Microbacterium . Inoculation with four of the selected ACC deaminase-producing strains not only stimulated the growth of the host plant but also influenced the flavonoids accumulation. All four strains could colonize and can be re-isolated from the host plant interior tissues. Conclusions These results demonstrate that ACC deaminase-producing habitat-adapted symbiotic bacteria isolated from halophyte could enhance plant growth under saline stress conditions and the PGPE strains could be appropriate as bioinoculants to enhance soil fertility and protect the plants against salt stress.

Description: Aims The objective of this study was to investigate the effects of future warming and drought on (1) the biochemical composition of above-ground biomass of forage plants ( Festuca arundinacea and Dactylis glomerata ), (2) the potential mineralization of this material in soil, and (3) its priming effect on native soil organic matter. Methods We sampled above-ground plant material from spring regrowth and summer regrowth of a climate change experiment. While in spring, the plants were well watered, the summer regrowth was exposed to drought and elevated temperature (+3 °C) by infrared heating of the canopy during 3 weeks. We assessed the elemental and isotopic composition, lignin and non-cellulosic carbohydrate content and composition of plant material grown under all three conditions. Its mineralization potential in soil and priming effects were evaluated during laboratory incubation. Results Warming had no significant effect on elemental and stable isotope composition of both plant materials. In contrast, it resulted in reduction of lignin content for both plant species and decrease of the lignin-to-N ratio for F. arundinacea and increased non-cellulosic carbohydrate content for D. glomerata . Summer regrowth was characterised by increase of δ 13 C values, which is consistent with variations in stomatal conductance due to water shortage. Moreover, summer drought induced an increase in N content leading to decrease of the C/N ratio and increase of lignin-to-N ratio of summer regrowth compared to spring regrowth. Differences in decomposition were small, while priming effects were more strongly altered by the different exposure to enviromental. Conclusion Our results provide direct experimental evidence that extreme climatic events (high temperature and precipitation deficit) have an influence on soil carbon storage particularly through their effect on priming of native soil organic matter induced by altered plant litter. These effects seem to be governed by alterations of stoichiometry and to a smaller extent by alterations of plant chemical composition.

Description: The effects of nonlinearities in the equations of motion of thermally fluctuating systems are investigated based on the Langevin equation. We identify the first terms in the expansions of equilibrium correlation functions and dynamic susceptibilities in powers of the thermal noise strength. The resulting expressions are explicitly evaluated for the case of overdamped diffusion in two monostable but anharmonic potentials, as well as in a double-well potential. The comparison to the results of numerical simulations allows to estimate the range of validity of our analytical results. Moreover, we provide a simple method to detect nonlinearities in the fluctuating time series data of a system in thermal equilibrium and discuss the resulting implications for the dynamics of composite systems. Finally, our findings shed light on the limitations of a recently introduced linear dynamic convolution theory, for which we derive a first-order correction term.

Description: We investigate the effect of a transverse field on a cylindrical core/shell spin-1 Ising nanowire, within the effective-field theory based on a probability distribution technique, in order to clarify how the relevant thermodynamic quantities such a magnetizations, hysteresis loops, compensation behaviors, are influenced by a transverse field. From these studies, following interesting phenomena are found. (i) Beside a singly hysteresis loop, double, triple or even quadruple hysteresis loops occurs in the system. (ii) The P and N types of compensation behavior are obtained in addition to the Q-, R- and S-types. We also compare our results with some experimental and theoretical results and find in a qualitatively good agreement.

Description: We introduce a new test for detection of power-law cross-correlations among a pair of time series – the rescaled covariance test. The test is based on a power-law divergence of the covariance of the partial sums of the long-range cross-correlated processes. Utilizing a heteroskedasticity and auto-correlation robust estimator of the long-term covariance, we develop a test with desirable statistical properties which is well able to distinguish between short- and long-range cross-correlations. Such test should be used as a starting point in the analysis of long-range cross-correlations prior to an estimation of bivariate long-term memory parameters. As an application, we show that the relationship between volatility and traded volume, and volatility and returns in the financial markets can be labeled as the power-law cross-correlated one.

Description: Background and aim Saccharothrix algeriensis NRRL B-24137, isolated from a Saharan soil, has been described as a potential biocontrol agent against Botrytis cinerea and other phytopathogens. However, the plant protection mechanisms involved still need to be described. The aim of this study was to determine this protection phenomenon as well as parts of the mechanisms involved, using Arabidopsis thaliana seedlings and B. cinerea . Methods The bacterial colonization process was evaluated on A. thaliana seedlings using fluorescence in situ hybridization. Protection of A. thaliana seedlings inoculated with NRRL B-24137 against B. cinerea was then evaluated. Parts of the mechanisms involved in the systemic protection against B. cinerea were evaluated using known mutants of genes involved in jasmonate (JA)/ethylene (ET)/salicylic acid (SA) signaling. Other Arabidopsis mutants, AtrhbohD-3 , AtrhbohF-3 , and ups1-1 were also screened to determine other parts of the mechanisms involved. Results The results showed that the strain NRRL B-24137 colonized, epi- and endophytically, the roots of Arabidopsis seedlings but the strain was not a systemic colonizer during the time of the experiment. The strain NRRL B-24137 also reduced B. cinerea symptoms and the protection was linked to known mechanisms of induced systemic resistance (ISR; JA/ET signaling), as well as to functionality of AtrbohF oxidase and of UPS1. Crosstalk between ET/JA and SA signaling could also be involved. Conclusions The isolate NRRL B-24137, after colonizing the root systems of A. thaliana , induces an ISR against B. cinerea , which is JA/ET dependent, but could also require SA crosstalk and protection could also require NAPDH oxidases and UPS1 functionalities.

Description: Background and aims The effect of forest cover distribution and plant litter input on soil organic carbon were analyzed to better understand the dynamics of carbon cycling across ecosystems on the “Natural Oriented Reserve Bosco delle Pianelle”. Fluorescence spectroscopy represents a very useful tool to characterize soil organic matter properties, since it allows to directly monitor the molecular status of a fluorophore depending on its chemical environment, as well as on its structure, substituents of the aromatic moieties, and molecular weight. Here, fluorescence analysis was performed on humic acids isolated from four litters (HALs) and their underlying soils (HAs) at three depths. Methods All samples were collected from a protected forest area, Southern Italy, under different plant covering: Quercus ilex L. (Q), mixed Carpinus betulus L. and Carpinus orientalis Mill. (CC), Pinus halepensis L. (P), and mixed Quercus trojana Webb. and Quercus ilex L. (QQ). Results Data obtained showed a fast decomposition process for P and QQ litters, with HAs in the underlying soils characterized by the presence of simple, highly fluorescent structural components also in the deepest layers. On the contrary, a slow decomposition process was observed for Q and CC litters, whose underlying soil HAs were characterized by an increasing aromatic polycondensation and humification degree from the surface to the deepest layers, as supported by low values of fluorescence intensity and high wavelength maxima. Conclusions Results obtained indicate that P and QQ species promote C accumulation and stock in the underlying soils, thanks to a greater decomposition of their litter, and fluorescence spectroscopy is a very simple and suitable method to evaluate the influence of three species distribution on soil organic carbon pools.

Description: An analytical expression is derived for the electron thermionic current from heated metals by using a non equilibrium, modified Kappa energy distribution for electrons. This isotropic distribution characterizes the long high energy tails in the electron energy spectrum for low values of the index κ and also accounts for the Fermi energy for the metal electrons. The limit for large κ recovers the classical equilibrium Fermi-Dirac distribution. The predicted electron thermionic current for low κ increases between four and five orders of magnitude with respect to the predictions of the equilibrium Richardson-Dushmann current. The observed departures from this classical expression, also recovered for large κ , would correspond to moderate values of this index. The strong increments predicted by the thermionic emission currents suggest that, under appropriate conditions, materials with non equilibrium electron populations would become more efficient electron emitters at low temperatures.

Description: We describe linear and nonlinear transport across a strongly interacting single impurity Anderson model quantum dot with intermediate coupling to the leads, i.e. with tunnel coupling Γ of the order of the thermal energy k B T . The coupling is large enough that sequential tunneling processes (second order in the tunneling Hamiltonian) alone do not suffice to properly describe the transport characteristics. Upon applying a density matrix approach, the current is expressed in terms of rates obtained by considering a very small class of diagrams which dress the sequential tunneling processes by charge fluctuations. We call this the “dressed second order” (DSO) approximation. One advantage of the DSO is that, still in the Coulomb blockade regime, it can describe the crossover from thermally broadened to tunneling broadened conductance peaks. When the temperature is decreased even further ( k B T 〈 Γ ), the DSO captures Kondesque behaviours of the Anderson quantum dot qualitatively: we find a zero bias anomaly of the differential conductance versus applied bias, an enhancement of the conductance with decreasing temperature as well as universality of the shape of the conductance as function of the temperature. We can without complications address the case of a spin degenerate level split energetically by a magnetic field. In case spin dependent chemical potentials are assumed and only one of the four chemical potentials is varied, the DSO yields in principle only one resonance. This seems to be in agreement with experiments with pseudo spin [U. Wilhelm, J. Schmid, J. Weis, K.V. Klitzing, Physica E 14 , 385 (2002)]. Furthermore, we get qualitative agreement with experimental data showing a cross-over from the Kondo to the empty orbital regime.

Description: We use the Schwinger boson mean field theory to study the effect of frustration and dimerization in the quantum ferrimagnetic model in one and two-dimensions. We calculate the spin reduction, the gap of the antiferromagnetic branch, and the spin fluctuation at T  = 0 K. At finite temperature, the long-range order is destroyed because of the disappearance of the Bose condensation. The free energy, the magnetic susceptibility and the spin correlations at T  = 0 K, are calculated. The effects of frustration and dimerization are discussed.

Description: We considerer that a population of individuals governed by the Nagumo model is subjected to a crisis that stimulates a predisposition towards aggregation. We assume that this trend is based on the physical mechanisms of attraction between individuals. Then we describe the post-crisis dynamics and find possible states of survival (stationary solutions). We see a dynamic rich in options with several possible survival responses.

Description: We study a disordered 2D electron gas with a spectral node in a vicinity of the node. After identifying the fundamental dynamical symmetries of this system, the spontaneous breaking of the latter by a Grassmann field is studied within a nonlinear sigma model approach. This allows us to reduce the average two-particle Green’s function to a diffusion propagator with a random diffusion coefficient. The latter has non-degenerate saddle points and is treated by the conventional self-consistent Born approximation. This leads to a renormalized chemical potential and a renormalized diffusion coefficient, where the DC conductivity increases linearly with the density of quasiparticles. Applied to the special case of Dirac fermions, our approach provides a comprehensive description of the minimal conductivity at the Dirac node as well as for the V-shape conductivity inside the bands.

Description: In the present contribution we apply first principles calculations to investigate the electronic structures and stability of BN hydrogenated monolayers which include a substitutional carbon atom. For comparison, additional C hydrogenated structures are considered. The obtained results demonstrate that BN chair-like monolayers are more stable than boat-like configurations. It is found that the most stable structures present bond angles quite similar to the characteristic one observed for s p 3 hybridization. Moreover, a net magnetic moment arises from the introduction of a substitutional carbon impurity. In addition, the results indicate that carbon substitutionals can induce a remarkable reduction of the work function.

Description: Using a recently proposed algorithmic scheme for correlation dimension analysis of hyperchaotic attractors, we study two well-known hyperchaotic flows and two standard time delayed hyperchaotic systems in detail numerically. We show that at the transition to hyperchaos, the nature of the scaling region changes suddenly and the attractor displays two scaling regions for embedding dimension M  ≥ 4. We argue that it is an indication of a strong clustering tendency of the underlying attractor in the hyperchaotic phase. Because of this sudden qualitative change in the scaling region, the transition to hyperchaos can be easily identified using the discontinuous changes in the dimension ( D 2 ) at the transition point. We show this explicitely for the two time delayed systems. Further support for our results is provided by computing the spectrum of Lyapunov Exponents (LE) of the hyperchaotic attractor in all cases. Our numerical results imply that the structure of a hyperchaotic attractor is topologically different from that of a chaotic attractor with inherent dual scales, at least for the two general classes of hyperchaotic systems we have analysed here.

Description: We have investigated the realizability of the controlled-not (cnot) gate and characterized the gate operation by quantum process tomography for a chain of qubits, realized by electrons confined in self-assembled quantum dots embedded in the spin field-effect transistor. We have shown that the cnot gate operation and its process tomography are performable by using the spin exchange interaction and several local qubit rotations within the coherence time of qubits. Moreover we have taken into account the fluctuation of operation time and the imperfection of polarization of channel electrons as sources of decay of fidelity. The cnot process fidelity decreases only by at most 5% by the fluctuation of the operation time and its values as high as 0.49 and 0.72 are obtained for the channel spin polarizations of 0.6 and 0.8, respectively.

Description: The multivariable theory of nucleation in Langevin’s approach [N.V. Alekseechkin, J. Chem. Phys. 124 , 124512 (2006); N.V. Alekseechkin, J. Chem. Phys. 129 , 024512 (2008)] is applied to the problem of vapor bubbles formation in a liquid with arbitrary viscosity. The obtained expression for the nucleation rate of bubbles is valid for arbitrary relations between the kinetic parameters controlling the nucleation process: viscosity, inertia of a liquid, the rate of evaporation into a bubble and the rate of heat exchange between the bubble and ambient liquid. So, the presented theory yields a complete description of the vapor-bubbles nucleation kinetics in single-component liquids. Limiting cases with respect to the mentioned parameters are considered, in particular, the low-viscosity limit. It is shown that the low- and high-viscosity nucleation rates differ from each other qualitatively and quantitatively. The possibility of application of the theory to cavitation in superfluid helium-4 is discussed.

Description: The electronic and magnetic properties of 6H-SiC with Mn impurities have been calculated using GGA formalism. Various configurations of Mn sites were considered. It was found that 6H-SiC doped with Mn atoms possess a moment for both types of substitution. The Mn atom at Si site possesses larger magnetic moment than Mn atom at C site. The energy levels appearing in the band gap due to vacancies and due to Mn impurities are determined and the calculated densities of states (DOSs) are used to analyse the different value of the magnetic moments for different types of substitution. A model that explains the magnetic moment at Mn site is proposed.

Description: Aims The objective of our study was to confirm if hydraulic lift (HL) promotes nutrient uptake in field-grown plants in the same way as demonstrated previously in pot-grown plants. Methods We conducted a field experiment in an agroforestry system, over an entire growing season that included a dry period and a wet period. We used a shallow-root crop plant, mung bean ( Vigna radiata L.), intercropped with walnut ( Juglans regia L.) and jujube ( Zizyphus jujube Mill.), as an indicator for the presence of HL and its effects on nutrient uptake. To monitor HL, we artificially applied deuterium isotope to the deep roots of trees. Results We demonstrated the presence of a natural nitrogen, phosphorus, and potassium gradient along the soil depth, and the occurrence of HL, evidenced by deuterium signature in the shallow soil layers and V. radiata stem, only during the dry season. J. regia and Z. jujube both had deep root systems, but the former species exhibited stronger HL to the shallow soil than the latter. Meanwhile, the upper soil layers of J. regia had significantly higher moisture content, and the intercropped V. radiata had higher nutrient content. Conclusion HL can facilitate water uptake by V. radiata from the upper soil layers in the field condition during the dry season, which relates to nutrient acquisition by the crop.

Description: The Íslendinga sögur – or Sagas of Icelanders – constitute a collection of medieval literature set in Iceland around the late 9th to early 11th centuries, the so-called Saga Age . They purport to describe events during the period around the settlement of Iceland and the generations immediately following and constitute an important element of world literature thanks to their unique narrative style. Although their historicity is a matter of scholarly debate, the narratives contain interwoven and overlapping plots involving thousands of characters and interactions between them. Here we perform a network analysis of the Íslendinga sögur in an attempt to gather quantitative information on interrelationships between characters and to compare saga society to other social networks.

Description: We report the quasiparticle band structure and optical absorption spectrum of bulk LiBr calculated from first-principles approaches. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into consideration, the optical excitation is investigated by solving the Bethe-Salpeter equation for the electron-hole two-particle Green’s function. The obtained results for the band gap and optical absorption spectrum are in good agreement with experimental measurements.

Description: The aim of this article is to present an overview about the preparation method and physical properties of a new hybrid system consisting of single-walled carbon nanotubes (SWNTs) wrapped by conjugated polymers. The technique firstly demonstrated in 2007 has attracted great interest because of the high purity of the resulting semiconducting SWNTs and the possibility of applying them in electronic devices. Here, we will review recent progresses regarding the preparation of these nano-hybrids, their photophysical properties and application in field-effect transistors and photovoltaic devices.

Description: In this paper, we propose a family of weighted extended Koch networks based on a class of extended Koch networks. They originate from a r -complete graph, and each node in each r -complete graph of current generation produces mr -complete graphs whose weighted edges are scaled by factor  h in subsequent evolutionary step. We study the structural properties of these networks and random walks on them. In more detail, we calculate exactly the average weighted shortest path length (AWSP), average receiving time (ART) and average sending time (AST). Besides, the technique of resistor network is employed to uncover the relationship between ART and AST on networks with unit weight. In the infinite network order limit, the average weighted shortest path lengths stay bounded with growing network order (0 〈  h  〈 1). The closed form expression of ART shows that it exhibits a sub-linear dependence (0 〈  h  〈 1) or linear dependence ( h  = 1) on network order. On the contrary, the AST behaves super-linearly with the network order. Collectively, all the obtained results show that the efficiency of message transportation on weighted extended Koch networks has close relation to the network parameters  h , m  and  r . All these findings could shed light on the structure and random walks of general weighted networks.

Description: Specific heat and magnetization measurements demonstrate that the antiferromagnetic (AFM) phase transition at T N  = 5.7 K of EuTiO 3 is rapidly suppressed with Sr doping in Eu x Sr 1− x TiO 3 . Close to x  = 0.25, T N  = 0 K and AFM order vanishes. Above this critical concentration a finite transition temperature to an AFM phase is observed. The exchange couplings are derived as a function of x and the corresponding low temperature phase diagram is presented.

Description: Going beyond the limitations of our earlier works [X. Zheng, F. Wang, C.Y. Yam, Y. Mo, G.H. Chen, Phys. Rev. B  75 , 195127 (2007); X. Zheng, G.H. Chen, Y. Mo, S.K. Koo, H. Tian, C.Y. Yam, Y.J. Yan, J. Chem. Phys. 133 , 114101 (2010)], we propose, in this manuscript, a new alternative approach to simulate time-dependent quantum transport phenomenon from first-principles. This new practical approach, still retaining the formal exactness of HEOM framework, does not rely on any intractable parametrization scheme and the pole structure of Fermi distribution function, thus, can seamlessly incorporated into first-principles simulation and treat transient response of an open electronic systems to an external bias voltage at both zero and finite temperatures on the equal footing. The salient feature of this approach is surveyed, and its time complexity is analysed. As a proof-of-principle of this approach, simulation of the transient current of one dimensional tight-binding chain, driven by some direct external voltages, is demonstrated.

Description: The dynamics of α -helical proteins with interspine coupling by taking into account long-range dipole-dipole interactions and some additional higher order molecular excitations is studied. The model Hamiltonian is transformed into a set of three classical lattice equations, which are further reduced in the multiple scales analysis to a set of three coupled nonlinear Schrödinger (3-CNLS) equations. The linear stability analysis of continuous wave solutions of these 3-CNLS equations is performed and it reveals that the modulational instability (MI) gain is deeply influenced by the long-range interactions (LRI) parameter. Some classes of exact traveling wave solutions are constructed via the solutions of a φ 4 model through the F-expansion method and representative wave structures are graphically displayed including localized and periodic solutions. In order to confirm the analytical approach, the numerical experiments show that the solitons are stable at 70 ps. These solitons, exhibited in the model, are a possible carrier of bio-energy transport in the protein molecules.

Description: It is well-known that cooperative properties such as magnetic ordering can depend on the samples’ dimensions ( D s) in a qualitative way. However, there have been no samples with well-defined non-integer D s. The dimension of a given sample has been always discussed on the anisotropy of the electronic/crystal/magnetic structures, which has no definition suitable for quantitative discussion on dimensions vs. properties. On the other hand a particular type of porous samples, i.e. fractal bodies, can have well-defined non-integer D s dependent exclusively on the geometrical feature of structures, and physical properties of such materials remains unexplored. This paper reports on magnetic ordering in samples covering 2.5 ≤  D  ≤ 3, in addition to a way of precise control of the fractal dimensions of given samples simply by wax (alkylketene dimer). The results show that the magnetic ordering temperatures, i.e. Néel temperatures ( T N s), of CoO depend on D , and rapidly enhance immediately below D  = 3. This means that one can control or enhance the critical temperature simply by tuning D with keeping the remaining magnetic properties unchanged.

Description: Aims and background Despite increasing knowledge of the role of allelochemicals in the productivity decline of replanted Chinese fir plantations, relatively little is known about the levels and sources of allelochemicals in relation to autoinhibition. Methods Allelopathic potential of litter, root exudates, and soils in successive rotations of Chinese fir plantations were detected. An allelochemical cyclic dipeptide (6-hydroxy-1,3-dimethyl-8-nonadecyl-[1,4]-diazocane-2,5-dione) from litter, root exudates, and soils in successive rotations was quantified. Results Extracts of leaf litter, fine root, and root exudates significantly inhibited the growth of Chinese fir germinants, and inhibition increased with successive rotations. Similar results were observed in the rhizosphere soil, basal soil, and bulk soil. The largest observed inhibition occurred in the rhizosphere soil. Furthermore, cyclic dipeptide was found in litter, root exudates, and soils, and the concentrations increased with successive rotations. The rhizosphere soil had the highest cyclic dipeptide level, followed by basal soil, while bulk soil contained the lowest concentration. There was a significant positive relationship between the inhibition of radicle growth of Chinese fir germinants and the concentration of cyclic dipeptide. Annual release of cyclic dipeptide through root exudation was 2.08–9.78 mol ha −1 annum, but the annual release of cyclic dipeptide through leaf litter decomposition was lowered to 0.32–1.41 mol ha −1 annum. Conclusions Cyclic dipeptide which caused autoinhibition of Chinese fir may be released into the soil through litter decomposition and root exudation. Root exudates provided more contributions to soil cyclic dipeptide levels than litter in Chinese fir plantations.

Description: Background and aims In the Central Negev hills (Israel) many ancient terraced wadis exist, which captured run-off and caused gradual soil aggradation, which enabled agricultural practices. In these terraces, dark colored soil horizons were observed, containing charcoal, as can be found in Terra Preta soils, suggesting higher fertility compared to natural soils. The aim of our investigation was to investigate these anthropogenic soils and to study the effects of charcoal and ash addition on soil properties and crop growth. Methods We investigated 12 soil profiles, focusing on possible differences between light and dark colored soil horizons. We also investigated the effects of amendment of charcoal and ash on the growth of wheat ( Triticum Aestivum L. ) in a 40-day pot experiment involving two water regimes. Results Results show that charcoal content in light and dark horizons were both low (〈0.2 %), but significantly lower bulk densities were found in dark colored horizons. In the crop experiment, charcoal addition resulted in decreased crop growth, while, in the water deficit regime, ash addition resulted in increased crop growth. Conclusions Considering the observed charcoal and the results from the crop experiment, we hypothesize that, in ancient run-off capturing agricultural systems, ash was purposefully added as fertilizer.

Description: We report low-temperature susceptibility and magnetisation data for the cubic pyrochlore Er 2 Ti 2 O 7 . By performing the measurements on single crystals we are able to establish the degree of magnetic anisotropy present in this compound and to determine the critical values for magnetic field induced transitions below the magnetic ordering temperature of 1.2 K. We also present a magnetic H - T phase diagram of this quantum XY antiferromagnet for different directions of an applied field.

Description: We simulate the three-dimensional quantum Heisenberg model with a spatially anisotropic ladder pattern using the first principles Monte Carlo method. Our motivation is to investigate quantitatively the newly established universal relation T N /√ c 3 ∝ ℳ s near the quantum critical point (QCP) associated with dimerization. Here T N , c , and ℳ s are the Néel temperature, the spinwave velocity, and the staggered magnetization density, respectively. For all the physical quantities considered here, such as T N and ℳ s , our Monte Carlo results agree nicely with the corresponding results determined by the series expansion method. In addition, we find it is likely that the effect of a logarithmic correction, which should be present in (3 + 1)-dimensions, to the relation T N /√ c 3 ∝ ℳ s near the investigated QCP only sets in significantly in the region with strong spatial anisotropy.

Description: Non-adiabatic effects in quantum escapes of a particle via a time-dependent potential barrier in a semi-infinite one-dimensional space are discussed. We describe the time-evolution of escape states in terms of scattering states of the open system with a time-periodic potential by Floquet’s theorem and the Lippmann-Schwinger equation, and calculate concretely the probability P ( t ) for a particle to remain in the initially confined region at time t in the case of a delta-function potential with a time-oscillating magnitude. The probability P ( t ) decays exponentially in time at early times, then decays as a power later, along with a time-oscillation in itself. We show that a larger time-oscillation amplitude of the potential leads to a faster exponential decay of P ( t ), while it can rather enhance the probability P ( t ) decaying as a power. An explanation based on an average of adiabatic decays of P ( t ) is given to describe qualitatively these contrastive properties of P ( t ) in different types of decay. By investigating quantitative differences between the survival probability given from a direct solution of the Schrödinger equation with the time-oscillating potential and that obtained by an average of adiabatic decays, we clarify non-adiabatic effects in the decay time and the power decay magnitude of P ( t ).

Description: Introduction In a recent paper, Warren et al. ( 2013 ) illustrated the potential of neutron radiography to visualize water dynamics in soil and plants. Methods After injection of deuterated water (D 2 O) in soil, the authors could monitor the changes of D 2 O concentration in roots. Results Based on the radiographs, the authors concluded that D 2 O was transported from roots growing in a wet soil region to roots in a dry region, proving hydraulic redistribution between roots. However, this interpretation depends on the correct estimation of D 2 O concentration in soil. Conclusions The experiments of Warren et al. ( 2013 ) could also be explained by diffusion of D 2 O from soil to roots, without hydraulic redistribution within the root system.

Description: Aims The mechanisms of belowground competition are not well understood. Addressing literature reports on competition-induced changes in tree fine root morphology, we conducted a growth experiment with tree saplings to investigate competition effects on important root morphological and functional traits in a root order-focused analysis. Methods European beech and European ash saplings were grown for 34 months in containers under greenhouse conditions in monoculture (2 conspecific plants), in mixture (1 beech and 1 ash) or as single plants. The root system was fractionated according to root orders and eight morphological and functional properties were determined. Results Root order was the most influential factor affecting the fine root traits (except for root diameter and δ 13 C); a significant species identity effect was found for root diameter, tissue density, N concentration and δ 13 C. Ash fine roots were thicker, but had lower tissue densities, contained more N and had systematically higher δ 13 C values than beech roots. The competition treatments had no significant effect on morphological root traits but altered δ 13 C in the 2nd root order. Conclusion Neither intra- nor interspecific root competition affected fine root morphology significantly suggesting that competition-induced root modification may not be a universal phenomenon in temperate trees.

Description: We report on the magnetic properties of four isomorphous compounds of a family of quinternary oxalates down to 60 mK. In all these materials, the magnetic Fe II ions with a strong magneto-crystalline anisotropy form a distorted kagome lattice, topologically equivalent to a perfect kagome one if nearest-neighbor interactions only are considered. All the compounds order at low temperature in an antiferromagnetic arrangement with magnetic moments at 120°. A remarkable magnetic behavior emerges below the Néel temperature in three compounds (with inter-kagome-layer Zr, Sn, Fe but not with Al): the spin anisotropy combined with a low exchange path network connectivity lead to domain walls intersecting the kagome planes through strings of free spins. These produce an unfamiliar slow spin dynamics in the ordered phase observed by AC susceptibility, evolving from exchange-released spin-flips towards a cooperative behavior on decreasing the temperature.

Description: We extend our previous approach [J. Kurzyk, W. Wójcik, J. Spalek, Eur. Phys. J. B 66 , 385 (2008); J. Spałek, J. Kurzyk, R. Podsiadły, W. Wójcik, Eur. Phys. J. B 74 , 63 (2010)] to modeling correlated electronic states and the metal-insulator transition by applying the so-called statistically consistent Gutzwiller approximation (SGA) to carry out self-consistent calculations of the renormalized single-particle Wannier functions in the correlated state. The transition to the Mott-Hubbard insulating state at temperature T  = 0 is of weak first order even if antiferromagnetism is disregarded. The magnitude of the introduced self-consistent magnetic correlation field is calculated and shown to lead to a small magnetic moment in the magnetically uniform state. Realistic value of the applied magnetic field has a minor influence on the metallic-state characteristics near the Mott-Hubbard localization threshold. The whole analysis has been carried out for an extended Hubbard model on a simple cubic (SC) lattice and the evolution of physical properties is analyzed as a function of the lattice parameter for the renormalized 1 s -type Wannier functions. Quantum critical scaling of the selected physical properties is analyzed as a function of the lattice constant R  →  R c  = 4.1 a 0 , where R c is the critical value for metal-insulator transition and a 0  = 0.53 Å is the Bohr radius. A critical pressure for metallization of solid atomic hydrogen is estimated and is ~10 2 GPa.

Description: Magnetic particles are largely utilized in several applications ranging from magnetorheological fluids to bioscience and from nanothechnology to memories or logic devices. The behavior of each single particle at finite temperature (under thermal stochastic fluctuations) plays a central role in determining the response of the whole physical system taken into consideration. Here, the magnetization evolution is studied through the Landau-Lifshitz-Gilbert formalism and the non-equilibrium statistical mechanics is introduced with the Langevin and Fokker-Planck methodologies. As result of the combination of such techniques we analyse the stochastic magnetization dynamics and we numerically determine the convergence time, measuring the velocity of attainment of thermodynamic equilibrium, as function of the system temperature.

Description: Background and aims Distinct metal distribution patterns within leaves of metal hyperaccumulating plants are repeatedly observed however, the presumable role of key structural biochemical molecules in determining and regulating their allocation remains largely unknown. We aimed to characterise in a spatially resolved manner the distribution of the main biochemical components in leaves of field-collected Cd/Zn-hyperaccumulating Noccaea praecox in order to relate them to metal distribution patterns at tissue level. Methods The biomolecular composition of the leaves was spatially analysed using synchrotron radiation Fourier Transform Infrared (FTIR) and the distribution of Zn with synchrotron radiation Low-Energy X-Ray Fluorescence (LEXRF) microspectroscopy was determined on the same tissues of interest (epidermis, sub-epidermis, mesophyll). Results In epidermal cells high proportion of free-carboxyl, nitro and phosphate groups standing for pectin, nitroaromatics, phytic and other organic acids were found. Adjacent mesophyll cells had higher proportions of proteins, carbohydrates and cellulosic compounds. Conclusions Pectin compounds were indicated as important components of Zn enriched epidermal cell walls. In addition, intense lignification of epidermal cell walls might limit leakage of the trapped metals back to the metabolically active and thus more sensitive mesophyll. Distribution of metal-binding compounds in particular cell types/tissues may therefore predispose metal distribution patterns and tolerance in leaves.

Description: We propose a lattice Monte Carlo model of two populations, predators and prey. We divide predators into cooperative predators and defective predators. Cooperative predators participate in hunting. On the other hand, defective predators only participate to dominate, i.e. take possession of, the food when a kill has already been made by a cooperative predator. Numerous factors have been taken into account in our research, such as individual mobility, predation and hunger time. The model we have constructed displays the features of the population that evolve through time and the spatial distribution of the population. We focus on the emergence of defective predators and how the parameters affect the system. The results indicate that prey can profit from the appearance of these defective predators in some specific situations. It has even been shown that the emergence of defective predators can sometimes save endangered systems.

Description: The remanent magnetization M r on easy-axis antiferromagnetic single crystal K 2 FeCl 5 ·H 2 O is investigated. The sign of the remanent magnetization depends on the direction of the applied magnetic field  H ; if it is perpendicular to the easy axis of antiferromagnet then the sign of the remanent magnetization is positive, i.e. it coincides with the sign of the magnetic field in which the sample was cooled down below  T N . Instead, if the magnetic field is directed along the easy axis then the sign of the remanent magnetization is negative and its absolute value is three orders of magnitude larger than usual magnetization M ( T N , H ).

Description: In this work, calculations and preliminary experimental data for determining the optimal condition for the selective bio-functionalization of magnetic tunneling junction (MTJ)-based biosensors are presented. Results on the detection of biomolecular recognition events employing MTJ-based sensor and magnetic beads are presented and interpreted through calculations, taking into account the dependence of the signal on the distribution of the beads with respect to the sensor. Furthermore, it is demonstrated by calculations that a significant increase in the sensor sensitivity and quantification capability can be achieved by selectively bio-functionalizing an area which corresponds to the sensor active area.

Description: In this work, by using the discrete dipole approximation (DDA), we have proposed a model for the growth of chiral nano-flower shaped sculptured nanoparticle in different sizes and different symmetries (e.g., 3-, 4- and 5-fold symmetries) and calculated the extinction spectra for these nanostructures identifying their plasmon peaks. Our results show that the extinction spectrum obtained experimentally for a chiral nano-flower sculptured thin film can be the result of the overlap of extinction spectra from an assembly of chiral nanoflowers forming the deposited thin film. Furthermore, we have investigated carefully the distribution of electric nearfields and have deduced the physical nature and direction of oscillations related to different plasmon peaks in the extinction spectra. Results show the existence of dipolar and quadrupolar oscillations in all structures while for the 4-fold symmetry chiral nano-flower, we have also observed octopolar oscillations. The calculated results are compared with the experimental results reported by us in [H. Savaloni, F. Haydari-Nasab, M. Malmir, Appl. Surf. Sci. 257 , 9044 (2011)]. In addition, using the homogenization theory we have shown that the optical response of metallic structures is affected by a limited thickness of thin film and further increase of the film thickness has no effect on the optical spectra.

Description: Aims Tree species affect herb layer species through their effects on soil quality and light regime but their relative importance and interactions are insufficiently known. Methods Pot experiment with soil taken from stands planted with tree species with contrasting effects on soil acidification, two light regimes and six forest perennials. Results The survival or growth of Mercurialis perennis, Lamium galeobdolon , Anemone nemorosa and Primula elatior was lower in the acid Alnus soils than in the less acid Fraxinus soils. By contrast, the acid tolerant Convallaria majalis and Dryopteris dilatata were barely affected by tree species. Light conditions had less impact than soil chemistry and did not compensate for unfavourable soil conditions. Ca and P concentrations increased in plants grown in Fraxinus soils. The Mg and Al shoot/root ratios of respectively one and two of the acid tolerant species was elevated in the most acid soil. Conclusions Tree species effects on forest perennials are mainly explained by increased Al concentrations under acidifying species. Changed plant concentrations and allocation are likely associated to Al antagonism. We found no light compensation for the soil effect on the studied species. However, light alters the plant nutrient concentrations and allocation which may suggest an indirect effect.

Description: We investigate the properties of a recently introduced asymmetric association measure, called inner composition alignment (IOTA), aimed at inferring regulatory links (couplings). We show that the measure can be used to determine the direction of coupling, detect superfluous links, and to account for autoregulation. In addition, the measure can be extended to infer the type of regulation (positive or negative). The capabilities of IOTA to correctly infer couplings together with their directionality are compared against Kendall’s rank correlation for time series of different lengths, particularly focussing on biological examples. We demonstrate that an extended version of the measure, bidirectional inner composition alignment (biIOTA), increases the accuracy of the network reconstruction for short time series. Finally, we discuss the applicability of the measure to infer couplings in chaotic systems.

Description: Aims The aim of this study was to determine whether goat grazing in the understory of a pine forest at Doñana Natural Park could accelerate the decomposition of the pine needles accumulated on the soil surface and, if so, through which mechanisms. Specifically, the roles of trampling (mechanical fragmentation) and nutrient enrichment through defecation (fertilization) were evaluated in terms of their effect on pine needle decomposition rates. Methods An experiment was conducted featuring the following 4 treatments: 1) intact needles (control), 2) trampled needles, 3) intact needles fertilized with liquid manure, and 4) trampled needles fertilized with liquid manure. Litter decomposition was determined as a function of mass loss over time, using the litter-bag method. Bags were recovered 4, 8, 16, 24 and 36 months after burial in soil, dried and weighed. Needle length, leaf mass per area and C and N concentration were also measured in the buried litter-bags. Results Four months after burial, mass loss was greater in the trampled (23–27 %) than non-trampled (14–16 %) treatments. However, from 8 months onwards, decomposition rates in the fertilized treatments were significantly higher than those in the non-fertilized treatments (between 5 % and 15 % less mass loss). Meanwhile, fertilized treatments presented higher N content (2.1 %) than the non-fertilized ones (1.2 %), with a significantly lower C:N ratio also found in the in the fertilized treatment. Conclusions Trampling and fertilization during grazing accelerates litter decomposition and thus promotes the incorporation of N into the system. Acceleration of decomposition reduces the accumulation of pine needles on the soil surface, reducing the risk of fire.

Description: We consider a simple mesoscopic model of an excitable thermochemical system for which the system temperature as a function of time has a form of irregular spikes. The interspike intervals are mapped onto elements of a formal alphabet. The time evolution of system temperature is represented by a string over this alphabet. We demonstrate that the entropy of such string reaches a minimum for the values of model parameters where the coherence resonance of interspike intervals is observed.

Description: We consider the influence of internal fluctuations on the behavior of a bistable thermochemical system with a low temperature stable focus surrounded by a stable limit cycle arising from the subcritical Hopf bifurcation. We use a master equation approach to study the transitions between basins of these attractors. Distribution functions of first passage times from the limit cycle to the focus are obtained for systems with various numbers of molecules and reaction heats. We consider in detail the specific, multi-peak form of the distributions caused by eccentric location of the limit cycles with respect to the focus.

Description: Magnetic nanoparticles were produced in ZnO single crystals using ion implantation of Ni along the [0001] channelling direction of ZnO. The particles were identified by X-ray diffraction and magnetization measurements as a distribution of superparamagnetic nickel nanoparticles having diameters in the range 2 − 3 nm. The depth distribution and size of the particles were determined using Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). The obtained results agree with magnetization and X-ray diffraction (XRD) data. From the determined depth distribution, the density change of implanted region of the material modified by the implantation procedure was estimated.

Description: Magnetic properties of Ising nanoparticles with spin-1/2 core and spin-3/2 shell structure are systematically studied by the use of the effective-field theory with correlations. Particular emphasis is given to the effects of the crystal-field, core and shell interactions and interface coupling on magnetizations, compensations points, magnetic susceptibilities and hysteresis behaviors. In order to confirm the stability of the solutions we also investigate the free energy of the system. According to values of Hamiltonian parameters, the system only undergoes a second-order phase transition. A number of characteristic behaviors are found, such as the existence of triple hysteresis loops for appropriate values of the system parameters affected by the crystal field, temperature, and interface coupling. Moreover, Q-, R-, N-, M-, P- and S-types of compensation behaviors in the Néel classification nomenclature exist in the system that are also strongly dependent on interaction parameters; hence, one or two compensation points have been found. The results are compared with those of recently published works and a qualitatively good agreement is found.

Description: Monte Carlo simulations of heterogeneous systems of copper at liquid-vapor equilibrium have been performed at several temperatures from 1400 to 2000 K, using the EAM potential of Zhou et al. [Phys. Rev. B 69 , 144113 (2004)]. Surface tension of the corresponding planar interfaces has been evaluated using thermodynamic and mechanical approaches. We have investigated the impact of the potential and the temperature on the surface tension of liquid copper. For the first time, calculation results are in very good agreement with experiments with a maximum deviation of 2% from experiments. Additionally, the Monte Carlo simulations provide a temperature coefficient (the derivative of surface tension in regard with temperature) in excellent agreement with the experimental coefficient. This was one of the main challenges of the present simulations.

Description: The classical preferential attachment model is sensitive to the choice of the initial configuration of the network. As the number of initial nodes and their degree grow, so does the time needed for an equilibrium degree distribution to be established. We study this phenomenon, provide estimates of the equilibration time, and characterize the degree distribution cutoff observed at finite times. When the initial network is dense and exceeds a certain small size, there is no equilibration and a suitable statistical test can always discern the produced degree distribution from the equilibrium one. As a by-product, the weighted Kolmogorov-Smirnov statistic is demonstrated to be more suitable for statistical analysis of power-law distributions with cutoff when the data is ample.

Description: Based on a two-dimensional atomistic model, we study the bifurcation associated with crack propagation and kinking. In the study, the varying parameter is the tensile and shear strain applied at the boundary. Both mode-I and mixed mode-I/II loading are considered.

Description: Firm growth process in the developing economies is known to produce divergence in their growth path giving rise to bimodality in the size distribution. Similar bimodality has been observed in wealth distribution as well. Here, we introduce a modified kinetic exchange model which can reproduce such features. In particular, we will show numerically that a nonlinear retention rate (or savings propensity) causes this bimodality. This model can accommodate binary trading as well as the whole system-side trading thus making it more suitable to explain the non-standard features of wealth distribution as well as firm size distribution.

Description: The browsing behavior of massive web users forms a flow network transporting user’ collective attention between websites. By analyzing the circulation of the collective attention we discover the scaling relationship between the impact of sites and their traffic. We construct three clickstreams networks, whose nodes were websites and edges were formed by the users’ switching between sites. The impact of site i , C i , is measured by the clickstreams controlled by this site in the circulation of clickstreams. We find that C i scales sublinearly with A i , the traffic of site i . Specifically, there existed a relationship C i  ~  A i γ ( γ  〈 1), which implies the decentralized structure of the clickstream circulation.

Description: We investigate the critical behavior of the three-dimensional random-field Ising model (RFIM) with a Gaussian field distribution at zero temperature. By implementing a computational approach that maps the ground-state of the RFIM to the maximum-flow optimization problem of a network, we simulate large ensembles of disorder realizations of the model for a broad range of values of the disorder strength  h and system sizes

Description: Within the composite operator method (COM), we report the solution of the Emery model (also known as p - d or three band model), which is relevant for the cuprate high- T c superconductors. We also discuss the relevance of the often-neglected direct oxygen-oxygen hopping for a more accurate, sometimes unique, description of this class of materials. The benchmark of the solution is performed by comparing our results with the available quantum Monte Carlo ones. Both single-particle and thermodynamic properties of the model are studied in detail. Our solution features a metal-insulator transition at half filling. The resulting metal-insulator phase diagram agrees qualitatively very well with the one obtained within dynamical mean-field theory. We discuss the type of transition (Mott-Hubbard (MH) or charge-transfer (CT)) for the microscopic (ab initio) parameter range relevant for cuprates getting, as expected a CT type. The emerging single-particle scenario clearly suggests a very close relation between the relevant sub-bands of the three- (Emery) and the single-band (Hubbard) models, thus providing an independent and non-perturbative proof of the validity of the mapping between the two models for the model parameters optimal to describe cuprates. Such a result confirms the emergence of the Zhang-Rice scenario, which has been recently questioned. We also report the behavior of the specific heat and of the entropy as functions of the temperature on varying the model parameters as these quantities, more than any other, depend on and, consequently, reveal the most relevant energy scales of the system.

Description: We perform a thorough study of the strainology of the Raman response in graphene, for different external perturbations, within the framework of a long-wavelength, effective field theory for the vibrational spectrum. We calculate the evolution of the G-peak for the cases of compressive and stretching strains, and we discuss our results in connection to the physics of the G-peak redshift due to bending/uniaxial strain and the G-peak blueshift due to a substrate. Furthermore, we calculate the Raman response for the cases of periodic buckling of nanoribbons and within a toy model for ripples, and in both cases we are able to obtain a rather broad, D-like-peak in the Raman spectrum, even for the case of defect free graphene. We discuss all our theoretical results in connection to recent Raman spectroscopy experiments.

Description: Spontaneous synchronization of an ensemble of metronomes placed on a freely rotating platform is studied experimentally and by computer simulations. A striking in-phase synchronization is observed when the metronomes’ beat frequencies are fixed above a critical limit. Increasing the number of metronomes placed on the disk leads to an observable decrease in the level of the emerging synchronization. A realistic model with experimentally determined parameters is considered in order to understand the observed results. The conditions favoring the emergence of synchronization are investigated. It is shown that the experimentally observed trends can be reproduced by assuming a finite spread in the metronomes’ natural frequencies. In the limit of large numbers of metronomes, we show that synchronization emerges only above a critical beat frequency value.

Description: Background and aims Cadmium (Cd) could activate activity of mitogen-activated protein kinase MPK6 in plants. In this study, we investigated the role of MPK6 in mediating Cd toxicity in plants. Methods The wild type Arabidopsis plants (WT) and the mpk6 - 2 mutants were subjected either 0 (Control) or 10 μM Cd treatment. Kinase activity of MPK6, nitric oxide (NO) level, Cd concentration, and oxidative stress were measured. Results In WT plants, Cd exposure rapidly stimulated kinase activity of MPK6. However, upon Cd exposure, mpk6 - 2 showed better growth than the WT. Although Cd-induced production of NO in roots was greater in WT than in mpk6 - 2 , there was no difference in Cd concentration between the two plants. Nevertheless, the Cd-induced hydroperoxide burst, lipid peroxidation and loss of membrane integrity, were all more severe in the WT than in mpk6 - 2 . Foliar applications of antioxidant ascorbic acid, vigorously improved the growth of both the WT and mpk6 - 2 under Cd exposure. Thereby the growth difference between these two plants was minimized. Conclusions Mutation of mpk6 enhances Cd tolerance in plants by alleviating oxidative stress, but did not affect cadmium accumulation in plants.

Description: Background and Aims The role and linkage of endophytic bacteria to resistance of peanut seeds to biotic stress is poorly understood. The aims of the present study were to survey the experimental (axenic) and control (conventional) peanut plants for the predominant endophytic bacteria, and to characterize isolates with activity against selected A. flavus strains. Methods Young axenic plants were grown from presumably bacteria-free embryos in the lab, and then they were grown in a field. Endophytic bacterial species were identified by the analysis of DNA sequences of their 16S-ribosomal RNA gene. DNA extracted from soil was also analyzed for predominant bacteria. Results Mature seeds from the experimental and control plants contained several species of nonpathogenic endophytic bacteria. Among the eight bacterial species isolated from seeds, and DNA sequences detected in soil, Bacillus thuringiensis was dominant. All B. amyloliquefaciens isolates, the second abundant species in seeds demonstrated activity against A. flavus . This effect was not observed with any other bacterial isolates. There was no significant difference in number and relative occurrence of the two major bacterial species between the experimental and conventionally grown control seeds. Conclusion Endophytic bacterial colonization derives from local soil and not from the seed source, and the peanut plant accommodates only selected species of bacteria from diverse soil populations. Some bacterial isolates showed antibiosis against A. flavus.

Description: Background and Aims Climate warming and increased atmospheric nitrogen (N) deposition both have the potential to increase plant productivity over the next century, yet they can also increase decomposition and respiration. Our aim was to examine the extent to which warming and N addition can, on balance, alter net ecosystem CO 2 exchange (NEE) in a grass-dominated system. Methods We measured NEE responses to warming and N addition over two growing seasons in a temperate old field using steady-state flow-through chambers, which allowed for the integrated measurement of respiration and photoassimilation effects on net CO 2 flux over diel periods. We also assessed the relationship between NEE and plant biomass responses to the warming and N treatments. Results In both years, our study system was a net source of carbon (C) during the snow-free season. N addition did not significantly affect diel NEE or dark respiration in either year, despite a doubling in aboveground plant biomass in response to N addition in the second year, and a corresponding increase in peak daily net CO 2 photoassimilation in N addition plots. The warming treatment also had no significant effect on NEE, although the flow-through chambers required warming to be temporarily halted during NEE measurements. Conclusions Overall, our results both highlight the potential divergence of plant and soil responses to N addition and demonstrate the capacity for a grass-dominated system to function as a net source of C in consecutive years.

Description: Background and aim Intuitively, access to water from the soil at key phenological stages is important for adaptation to drought. This study aimed to assess the temporal pattern of water extraction under terminal drought stress. Methods Pearl millet genotypes with varying levels of terminal drought tolerance were grown in a lysimetric system with a soil volume and plant spacing similar to field conditions. Water extraction was monitored until maturity under differing water regimes. Results The yield did not differ among genotypes under well-watered (WW) conditions, and the water extraction profile of WW plants was similar across all genotypes. In contrast, the yield of sensitive genotypes was 30–100 % lower than that of tolerant lines under water stress (WS). The total volumes of water extracted by tolerant and sensitive genotypes were similar under WS; however, tolerant genotypes extracted less water prior to anthesis, and more water after anthesis. Grain yield was positively related to the amount of water extracted during week three after panicle emergence. Increased water extraction after anthesis benefitted the tillers more than the main culm and was correlated with higher staygreen scores. Conclusion Increased water uptake after anthesis, which results from earlier water conservation during pre-anthesis, increases yield under terminal drought in pearl millet.