The Physics of Cluster Mergers

Clusters of galaxies generally form by the gravitational merger of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. Some of the basic physical properties of mergers will be discussed, with an emphasis on simple analytic arguments rather than numerical simulations. Semi-analytic estimates of merger rates are reviewed, and a simple treatment of the kinematics of binary mergers is given. Mergers drive shocks into the intracluster medium, and these shocks heat the gas and should also accelerate nonthermal relativistic particles. X-ray observations of shocks can be used to determine the geometry and kinematics of the merger. Many clusters contain cooling flow cores; the hydrodynamical interactions of these cores with the hotter, less dense gas during mergers are discussed. As a result of particle acceleration in shocks, clusters of galaxies should contain very large populations of relativistic electrons and ions. Electrons with Lorentz factors gamma~300 (energies E = gamma m_e c^2 ~ 150 MeV) are expected to be particularly common. Observations and models for the radio, extreme ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles accelerated in these mergers are described.Comment: 38 pages with 9 embedded Postscript figures. To appear in Merging Processes in Clusters of Galaxies, edited by L. Feretti, I. M. Gioia, and G. Giovannini (Dordrecht: Kluwer), in press (2001

Co-limitation towards lower latitudes shapes global forest diversity gradients

The latitudinal diversity gradient (LDG) is one of the most recognized global patterns of species richness exhibited across a wide range of taxa. Numerous hypotheses have been proposed in the past two centuries to explain LDG, but rigorous tests of the drivers of LDGs have been limited by a lack of high-quality global species richness data. Here we produce a high-resolution (0.025° × 0.025°) map of local tree species richness using a global forest inventory database with individual tree information and local biophysical characteristics from ~1.3 million sample plots. We then quantify drivers of local tree species richness patterns across latitudes. Generally, annual mean temperature was a dominant predictor of tree species richness, which is most consistent with the metabolic theory of biodiversity (MTB). However, MTB underestimated LDG in the tropics, where high species richness was also moderated by topographic, soil and anthropogenic factors operating at local scales. Given that local landscape variables operate synergistically with bioclimatic factors in shaping the global LDG pattern, we suggest that MTB be extended to account for co-limitation by subordinate drivers

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

Taxonomic Appraisal of Conifers of Kashmir Himalaya

The wealth of vegetation that adorns the earth shows a vast array of floristic diversity ranging from microscopic algae to gigantic Eucalyptus. Among these, gymnosperms, particularly conifers, constitute an important floristic component of evergreen forests by virtue of their multidimensional ecological and socio-economic values. In view of their immense importance, a thorough study has been undertaken to explore the conifers of Kashmir. During the present investigation, a total of 16 species, spread over 9 genera in 3 families, were recorded. Among these, the family Pinaceae with 7 species in 4 genera is the most dominant, while Taxodiaceae with 2 species in 2 genera is the least represented. Out of the total taxa 7 species, belonging to 5 genera, are exotic and exist in cultivation only

Development of a flexible shear-stack for shaking table testing of geotechnical problems

SIGLEAvailable from British Library Document Supply Centre- DSC:DX178308 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Recovery and Restoration of Some Critically Endangered Endemic Angiosperms of the Kashmir Himalaya

Floristic diversity constitutes an indispensable resource-base for the human livelihood. Plants, being vital components of the biodiversity and the ecosystems they form, are essential for human progress and survival. In the recent past, however, human actions have brought a large number of plant species at the brink of extinction. One of the conservative estimates suggests that 60,000 to 100,000 plant species are threatened worldwide. These include a large number of endemic taxa, which being of considerable phytogeographic importance, need immediate attention of the botanists and conservationists. The Kashmir Himalaya harbours a rich angiosperm-flora, about 152 species of which are endemic exclusively to the Kashmir region. Many of these endemics are of great economic value, especially in food and fodder, local and commercial medicine, etc. Due to over-exploitation, habitat destruction and other anthropogenic activities, together with their innate sensitiveness, many of these endemics have become rare and threatened. This necessitates a thorough study of the threatened endemics of Kashmir so as to pave way for their conservation. The present study aims to dilate upon the taxonomy and the ex situ conservation aspects of five critically endangered endemic flowering-plant species of the Kashmir Himalaya, viz. Aquilegia nivalis, Aconitum kashmiricum, Lagotis cashmeriana, Megacarpaea polyandra and Saussurea costus

Ethno-Veterinary Medicinal Uses of Some Plant Species by the Gujar Tribe of the Kashmir Himalaya

The documentation of biodiversity and its traditional use(s) by the ethnic communities have assumed priority due to the rampant loss of biodiversity, the looming threats of biopiracy and the increasing patent wars on bio-resources. In view of this, the present paper describes in detail the ethno-veterinary medicinal uses of some angiosperm plant species by the Gujar tribe of the Kashmir Himalaya; with the sole objective of documentation of this secret treasure-trove of valuable ethno-botanic knowledge. In the present investigation, each plant species has been provided with the scientific name, local name, growth form, altitudinal range and present status of occurrence; followed by part(s) used, mode of preparation, method of use and the dosage

Cultivation of Salix L. - A Potential Bio-energy Crop in the Kashmir Himalaya, India

Salix is considered to be a golden crop among the tree canopy and Salix cultivation is known to be a practicable concept to get the best possible return in yield and profit. The eventual aim of present scientific activity was to produce maximum biomass/hectare of different Salix species/cultivars in the Kashmir Valley for resource oriented activities. Theseventeen accessions of various Salix species/cultivars were identified from different aggregates and cultivated under Short Rotation Coppice (SRC) method in natural as well as controlled conditions for three consecutive years. Various growth attributes of different Salix species/cultivars which were taken into consideration for the present study includes, the size of the leaves (length as well as breadth), number of branches per cutting, length of the branches and the number of leaves per branch.Salix babylonica showed the maximum (8cm, 11cm, 15cm) leaf length in first, second and third year of cultivation respectively, while minimum values for same was recorded for Salix pycnostachya. The number of branches per cutting also showed an increase in biomass in all the species/cultivars during the three years of cultivation. Salix babylonica showed the maximum length of branches in the first two years while Salix viminalis recorded the maximum in the last year. Salix babylonica depicted the highest number of leaves per branch during the three years of the experiment. During the three years of cultivation of different Salix species/cultivars, all the seventeen accessions showed an increase in biomass in all the attributes