Solving Set Constraint Satisfaction Problems using ROBDDs

In this paper we present a new approach to modeling finite set domain constraint problems using Reduced Ordered Binary Decision Diagrams (ROBDDs). We show that it is possible to construct an efficient set domain propagator which compactly represents many set domains and set constraints using ROBDDs. We demonstrate that the ROBDD-based approach provides unprecedented flexibility in modeling constraint satisfaction problems, leading to performance improvements. We also show that the ROBDD-based modeling approach can be extended to the modeling of integer and multiset constraint problems in a straightforward manner. Since domain propagation is not always practical, we also show how to incorporate less strict consistency notions into the ROBDD framework, such as set bounds, cardinality bounds and lexicographic bounds consistency. Finally, we present experimental results that demonstrate the ROBDD-based solver performs better than various more conventional constraint solvers on several standard set constraint problems

The threatened status of restricted-range coral reef fish species

Coral reefs are the most diverse ecosystem in the sea. Throughout the world they are being overfished, polluted and destroyed, placing biodiversity at risk. To date, much of the concern over biodiversity loss has centred on local losses and the possibility of global extinction has largely been discounted. However, recent research has shown that 24% of reef fish species have restricted ranges (< 800 000 km(2)), with 9% highly restricted (< 50 000 km(2)). Restricted-range species are thought to face a greater risk of extinction than more widespread species since local impacts could cause global loss. We searched for information on status in the wild and characteristics of 397 restricted-range reef fish species. Fish body size, habitat requirements and usefulness to people were compared with those of a taxonomically-matched sample of more widespread species. We found that on average species with restricted ranges were significantly smaller (mean total length 19.1 cm versus 24.4 cm), tended to have narrower habitat requirements and were less used by people. Greater habitat specificity will tend to increase extinction risk while, if real, more limited usefulness (equivalent to exploitation) may reduce risk. Fifty-eight percent of restricted-range species were considered common/abundant in the wild and 42% uncommon/rare. Population status and threats to 319 species for which data were available were assessed according to the categories and criteria of the IUCN red list of threatened animals. A number of species were found to be rare, were exploited and had highly restricted ranges overlapping areas where reef degradation is particularly severe, placing them at a high risk of extinction. Five species were listed as Critically Endangered, two of them possibly already extinct in the wild, one as Endangered and 172 as Vulnerable. A further 126 species fell into Lower Risk categories and 11 were considered Data Deficient. Given the intensity of impacts to reefs, the broad geographical areas affected and the large numbers of restricted-range species, global extinctions seem likely. Urgent management action is now crucial for the survival of several species of reef fishes

Dynamics of the formation of a hydrogel by a pathogenic amyloid peptide: islet amyloid polypeptide

Many chronic degenerative diseases result from aggregation of misfolded polypeptides to form amyloids. Many amyloidogenic polypeptides are surfactants and their assembly can be catalysed by hydrophobic-hydrophilic interfaces (an air-water interface in-vitro or membranes in-vivo). We recently demonstrated the specificity of surface-induced amyloidogenesis but the mechanisms of amyloidogenesis and more specifically of adsorption at hydrophobic-hydrophilic interfaces remain poorly understood. Thus, it is critical to determine how amyloidogenic polypeptides behave at interfaces. Here we used surface tensiometry, rheology and electron microscopy to demonstrate the complex dynamics of gelation by full-length human islet amyloid polypeptide (involved in type II diabetes) both in the bulk solution and at hydrophobic-hydrophilic interfaces (air-water interface and phospholipids). We show that the hydrogel consists of a 3D supramolecular network of fibrils. We also assessed the role of solvation and dissected the evolution over time of the assembly processes. Amyloid gelation could have important pathological consequences for membrane integrity and cellular functions

Making Optimum Use of the Limited Agricultural Resources of the Tribal Areas of S.W. Matabeleland

A ZJE article on agricultural rural development in Rhodesia's province of South West |Matebeleland.The title of this paper requires that it should at least:- a) Define the area under consideration. b) Outline its physical characteristics so that its agricultural resources may be established. c) Outline its socio-economic environment in order to discover what pressures there are on these resources, and to establish the development needs of the region. d) Propose how to make best use of the resources in the light of (c) above

Tribal Trust Land Development Corporation Limited: Rural Development in Rhodesia

A Zimbabwe Journal of Economics conference paper on the need for rural development in Rhodesia (now Zimbabwe.

Discovery of distant high luminosity infrared galaxies

We have developed a method for selecting the most luminous galaxies detected by IRAS based on their extreme values of R, the ratio of 60 micron and B-band luminosity. These objects have optical counterparts that are close to or below the limits of Schmidt surveys. We have tested our method on a 1079 deg^2 region of sky, where we have selected a sample of IRAS sources with 60 micron flux densities greater than 0.2 Jy, corresponding to a redshift limit z~1 for objects with far-IR luminosities of 10^{13} L_sun. Optical identifications for these were obtained from the UK Schmidt Telescope plates, using the likelihood ratio method. Optical spectroscopy has been carried out to reliably identify and measure the redshifts of six objects with very faint optical counterparts, which are the only objects with R>100 in the sample. One object is a hyperluminous infrared galaxy (HyLIG) at z=0.834. Of the remaining, fainter objects, five are ultraluminous infrared galaxies (ULIGs) with a mean redshift of 0.45, higher than the highest known redshift of any non-hyperluminous ULIG prior to this study. High excitation lines reveal the presence of an active nucleus in the HyLIG, just as in the other known infrared-selected HyLIGs. In contrast, no high excitation lines are found in the non-hyperluminous ULIGs. We discuss the implications of our results for the number density of HyLIGs at z<1 and for the evolution of the infrared galaxy population out to this redshift, and show that substantial evolution is indicated. Our selection method is robust against the presence of gravitational lensing if the optical and infrared magnification factors are similar, and we suggest a way of using it to select candidate gravitationally lensed infrared galaxies.Comment: 6 pages, accepted for publication in A&

Inlet spillage drag tests and numerical flow-field analysis at subsonic and transonic speeds of a 1/8-scale, two-dimensional, external-compression, variable-geometry, supersonic inlet configuration

Accurate spillage drag and pressure data are presented for a realistic supersonic inlet configuration. Results are compared with predictions from a finite-differencing, inviscid analysis computer procedure. The analytical technique shows good promise for the evaluation of inlet drag, but necessary refinements were identified. A detailed description of the analytical procedure is contained in the Appendix

Maintaining and restoring the ecological integrity of freshwater ecosystems: improving management by refining biological assessments

Water resources managers and conservation biologists need reliable, quantitative, and directly comparable methods for assessing the biological integrity of the world\u27s aquatic ecosystems. Large-scale assessments are constrained by the lack of consistency in the indicators used to assess biological integrity and our current inability to translate between indicators. In theory, assessments based on estimates of taxonomic completeness, i.e., the proportion of expected taxa that were observed (observed/expected, O/E) are directly comparable to one another and should therefore allow regionally and globally consistent summaries of the biological integrity of freshwater ecosystems. However, we know little about the true comparability of O/E assessments derived from different data sets or how well O/E assessments perform relative to other indicators in use. I compared the performance (precision, bias, and sensitivity to stressors) of O/E assessments based on five different data sets with the performance of the indicators previously applied to these data (three multimetric indices, a biotic index, and a hybrid method used by the state of Maine). Analyses were based on data collected from U.S. stream ecosystems in North Carolina, the Mid-Atlantic Highlands, Maine, and Ohio. O/E assessments resulted in very similar estimates of mean regional conditions compared with most other indicators once these indicators\u27 values were standardized relative to reference-site means. However, other indicators tended to be biased estimators of O/E, a consequence of differences in their response to natural environmental gradients and sensitivity to stressors. These results imply that, in some cases, it may be possible to compare assessments derived from different indicators by standardizing their values (a statistical approach to data harmonization). In situations where it is difficult to standardize or otherwise harmonize two or more indicators, O/E values can easily be derived from existing raw sample data. With some caveats, O/E should provide more directly comparable assessments of biological integrity across regions than is possible by harmonizing values of a mix of indicators. Read More: http://www.esajournals.org/doi/abs/10.1890/1051-0761(2006)016%5B1277%3AQBIBTC%5D2.0.CO%3B

What are riparian ecosystems and why are we worried about them

Riparian areas represent less than 2 percent of all terrestrial ecosystems, but they are functionally on of the most important features within natural landscapes. They are characterized by high biotic production and diversity; they moderate flood intensity and store water; and they maintain high water quality by acting as nutrient and sediment sinks. These ecological functions make them valuable areas for a variety of human uses including agriculture, timber and livestock production, recreation, and housing. Human use, however, has resulted in severe degradation of the functional health of many riparian ecosystems. Recognition of the value of the systems and the magnitude of existing and continuing degradation has generated a concerted effort by natural resources managers and researchers to develop strategies to protect and restore riparian areas. Issues requiring particular attention are (1) development of a generally accepted definition of riparian ecosystems, (2) development of a functionally useful classification scheme of riparian areas, (3) quantification of the specific ways that human use causes ecological dysfunction, (4) collection of data from which we can objectively prioritize efforts to preserve extant systems, and (5) development of ecologically sound strategies for the restoration of degraded areas