ALBERT

Description: The three-dimensional structure of incompressible flow in a narrow, open rectangular cavity in a flat plate was investigated with a focus on the flow topology of the time-averaged flow. The ratio of cavity length (in the direction of the flow) to width to depth was l:w:d=6:2:1. Experimental surface pressure data (in air) and particle image velocimetry data (in water) were obtained at low speed with free-stream Reynolds numbers of Rel = 3.4 × 105 in air and Rel = 4.3 × 104 in water. The experimental results show that the three-dimensional cavity flow is of the 'open' type, with an overall flow structure that bears some similarity to the structure observed in nominally two-dimensional cavities, but with a high degree of three-dimensionality both in the flow near the walls and in the unsteady behaviour. The defining features of an open-type cavity flow include a shear layer that traverses the entire cavity opening ultimately impinging on the back surface of the cavity, and a large recirculation zone within the cavity itself. Other flow features that have been identified in the current study include two vortices at the back of the cavity, of which one is barely visible, a weak vortex at the front of the cavity, and a pair of counter-rotating streamwise vortices along the sides of the cavity near the cavity opening. These vortices are generally symmetric about the cavity centre-plane. However, the discovery of a single tornado vortex, located near the cavity centreline at the front of the cavity, indicated that the flow within the cavity is asymmetric. It is postulated that the observed asymmetry in the time-averaged flow field is due to the asymmetry in the instantaneous flow field, which switches between two extremes at large time scales. © 2013 Cambridge University Press.

Description: SUMMARYChanges in the percentage of dry matter, sugars, starch and nitrogen present in Arran Banner and Majestic potato tubers during storage in clamps until July or later were studied in two seasons. In the first season, the ascorbic-acid content and the distribution of nitrogen between three fractions (insoluble, soluble coagulable, soluble non-coagulable) were also determined. In the second season, weighed samples of tubers were introduced into the clamps, so that changes in absolute amounts of the different constituents present in the tubers or sprouts could be measured. The effects of removing or retaining the soil cover on the clamps after early April were compared.

Description: A new quantitative, reproducible method for determining relative ages of unconsolidated Quaternary deposits containing granitic clasts has been developed and tested. The technique makes use of a microseismic timer to determine the compressional wave velocity (clast-sound velocity) in each clast of a group chosen from a single deposit. From these data a group mean velocity is determined that is proportional to the age of the deposit: the youngest deposits having the highest velocities. The clast-sound velocity method was used to study Quaternary deposits in the San Gabriel Valley and San Gabriel Mountains, California, using a previously proposed four-part age classification for the deposits. The clast-sound velocity group means for the four age groups were found to be statistically separable at better than 99% confidence. A velocity/age correlation curve was determined for these deposits using two radiocarbon dates and one paleomagnetic determination. This curve suggests that the clast-sound velocity method may be used to determine ages of deposits up to one million years old when calibrated with sufficient radiometric dates and may also be used as a tool for correlating undated deposits.

Description: Whether market-oriented conservation, by which we mean the promotion of markets for the products of intact ecosystems, protects biodiversity, and under what conditions, has been a subject of much research and debate. Our evaluation of three strategies of the market-oriented use of natural resources led us to conclude that, at least for these three strategies, market-oriented mechanisms of conservation are often socially, economically, or ecologically unsustainable, and that proposals for market-oriented conservation should be approached with caution (Crook & Clapp 1998). Shackleton's (2001) critique and extension of the conditions for market-oriented conservation offers many useful insights, although we question some of his interpretations. Herein we examine some of those extensions, and revisit the criteria for successful market-oriented conservation.

Description: Continuous records of the temperature of potatoes stored in clamps were made in 1942–3 (one clamp) and in 1943–4 (three clamps). In the first year, the temperatures at various positions in the clamp coverings were also recorded.The temperature at the middle of the potato heap showed a drift with time similar to that of mean air temperature. Deviations of mean air temperature from smooth trend, lasting for about a week, had no effect on the temperature of the potatoes; longerperiod deviations were reflected in the temperature of the potatoes after a lag of about a week. The difference in weekly mean temperature between potatoes and external air averaged about 1–5° C. in 1943–4. In 1942–3 it was greater, increasing to over 20° C. in April, because bacterial rotting of the potatoes following blight infection increased the rate of heat production and caused the clamp to collapse at the end of April.

Description: The destruction of forest ecosystems appears economically rational because many of the values of intact ecosystems are not recognized in land-use decisions. Many authors have suggested that the conservation of intact ecosystems requires that markets be extended to increase economic benefits derived from the standing forest to the point where they out-compete alternative, destructive land-uses. Three such strategies for market-oriented forest conservation are natural forest management for high-value timber, the collection of non-timber forest products, and biodiversity prospecting. In each case the proposed use of the ecosystem is likely to prove socially and economically unsustainable, or to generate significant alterations in ecosystem structure which endanger its diversity, or both. The success of market-oriented conservation requires that sustainable extraction of useful organisms over the long term yields more profit than destructive activities. The market-oriented conservation strategies examined, however, appear to yield too little profit to out-perform alternatives such as agricultural production or the replacement of forests by pastures or plantations. In each case, key factors limit profits. The slow growth rates of natural forests combined with discounting hinders natural forest management. In the case of non-timber forest products, the typically low density of resources in tropical forests creates disincentives for sustainable commercial production. The profitability of biodiversity prospecting is undermined by the low probability of discovering species with medicinal properties and developing countries' inability to capture the information value of the genetic content of species. Furthermore, each of the three strategies also has potentially negative ecological impacts. In the drive to increase profits, each is likely to degrade ecosystems through over-exploitation of the resource, and prompt simplification of the ecosystem through forest management designed to increase the density of profitable species. Ultimately, such activities are likely to lead to the loss of biodiversity.Several conditions must be met for market-oriented conservation to be effective. Scientific understanding of forest ecosystems, and the ecological knowledge of both users and regulators must be sufficiently advanced to allow appropriate management regimes to be designed to assure maintenance of the forest ecosystem despite alterations caused by resource harvesting. The natural reproduction rate of the harvested resource must also be sufficiently rapid to justify leaving most of the resource undisturbed to guarantee its reproduction. Furthermore, the resource must be more cheaply and reliably produced in a natural forest than in a plantation, than by a synthetic substitute, or replacement through domestication. Finally, even where ecological and economic conditions support market-oriented conservation, those making land-use decisions must be in a position to benefit from the sustainable harvest of forest resources. If they are unable to enforce exclusive rights to the forests, the conservation effect of market-oriented strategies is likely to prove elusive.Nevertheless, strategies for market-oriented forest conservation are a vital component of efforts to conserve biodiversity, and they must be improved to harness their full conservation potential. Resource management regulations, strong enforcement, and stable and secure property rights are essential preconditions. In addition, land-use planning should identify ecosystems with lower biological diversity where marketable products are concentrated at economic densities. Areas of high biological diversity will require non-market mechanisms to ensure their protection. In this context, there is no substitute for fully protected areas, and their expansion is vital.