A computational model for three-dimensional incompressible wall jets with large cross flow

A computational model for the flow field of three dimensional incompressible wall jets prototypic of thrust augmenting ejectors with large cross flow is presented. The formulation employs boundary layer equations in an orthogonal curvilinear coordinate system. Simulation of laminar as well as turbulen wall jets is reported. Quantification of jet spreading, jet growth, nominal separation, and jet shrink effects due to corss flow are discussed

Tropical rainforest bird community structure in relation to altitude, tree species composition, and null models in the Western Ghats, India

Studies of species distributions on elevational gradients are essential to understand principles of community organisation as well as to conserve species in montane regions. This study examined the patterns of species richness, abundance, composition, range sizes, and distribution of rainforest birds at 14 sites along an elevational gradient (500-1400 m) in the Kalakad-Mundanthurai Tiger Reserve (KMTR) of the Western Ghats, India. In contrast to theoretical expectation, resident bird species richness did not change significantly with elevation although the species composition changed substantially (<10% similarity) between the lowest and highest elevation sites. Constancy in species richness was possibly due to relative constancy in productivity and lack of elevational trends in vegetation structure. Elevational range size of birds, expected to increase with elevation according to Rapoport's rule, was found to show a contrasting inverse U-shaped pattern because species with narrow elevational distributions, including endemics, occurred at both ends of the gradient (below 800 m and above 1,200 m). Bird species composition also did not vary randomly along the gradient as assessed using a hierarchy of null models of community assembly, from completely unconstrained models to ones with species richness and range-size distribution restrictions. Instead, bird community composition was significantly correlated with elevation and tree species composition of sites, indicating the influence of deterministic factors on bird community structure. Conservation of low- and high-elevation areas and maintenance of tree species composition against habitat alteration are important for bird conservation in the southern Western Ghats rainforests.Comment: 36 pages, 5 figures, two tables (including one in the appendix) Submitted to the Journal of the Bombay Natural History Society (JBNHS

Radio recombination lines from the largest bound atoms in space

In this paper, we report the detection of a series of radio recombination lines (RRLs) in absorption near 26 MHz arising from the largest bound carbon atoms detected in space. These atoms, which are more than a million times larger than the ground state atoms are undergoing delta transitions (n~1009, Delta n=4) in the cool tenuous medium located in the Perseus arm in front of the supernova remnant, Cassiopeia A. Theoretical estimates had shown that atoms which recombined in tenuous media are stable up to quantum levels n~1500. Our data indicates that we have detected radiation from atoms in states very close to this theoretical limit. We also report high signal-to-noise detections of alpha, beta and gamma transitions in carbon atoms arising in the same clouds. In these data, we find that the increase in line widths with quantum number (proportional to n^5) due to pressure and radiation broadening of lines is much gentler than expected from existing models which assume a power law background radiation field. This discrepancy had also been noted earlier. The model line widths had been overestimated since the turnover in radiation field of Cassiopeia A at low frequencies had been ignored. In this paper, we show that, once the spectral turnover is included in the modeling, the slower increase in line width with quantum number is naturally explained.Comment: 5 pages, 4 figures, accepted for publication in MNRA

A consistent design procedure for supercritical airfoils in free air and a wind tunnel

A computational inverse procedure for transonic airfoils in which shapes are determined supporting prescribed pressure distributions is presented. The method uses the small disturbance equation and a consistent analysis-design differencing procedure at the airfoil surface. This avoids the intermediate analysis-design-analysis iterations. The effect of any openness at the trailing edge is taken onto account by adding an effective source term in the far field. The final results from a systematic expansion procedure which models the far field for solid, ideal slotted, and free jet tunnel walls are presented along with some design results for the associated boundary conditions and those for a free flight

Role of neutral metabolites in microbial conversion of 3ß-acetoxy-19-hydroxycholest-5-ene into estrone

Biotransformation of 3&#223;-acetoxy-19-hydroxycholest-5-ene (19-HCA, 6 g) by Moraxella sp. was studied. Estrone (712 mg) was the major metabolite formed. Minor metabolites identified were 5&#945;-androst-1-en-19-ol-3,17-dione (33 mg), androst-4-en-19-ol-3,17-dione (58 mg), androst-4-en-9&#945;,19-diol-3,17-dione (12 mg), and androstan-19-ol-3,17-dione (1 mg). Acidic metabolites were not formed. Time course experiments on the fermentation of 19-HCA indicated that androst-4-en-19-ol-3,17-dione was the major metabolite formed during the early stages of incubation. However, with continuing fermentation its level dropped, with a concomitant increase in estrone. Fermentation of 19-HCA in the presence of specific inhibitors or performing the fermentation for a shorter period (48 h) did not result in the formation of acidic metabolites. Resting-cell experiments carried out with 19-HCA (200 mg) in the presence of &#945;,&#945;'-bipyridyl led to the isolation of three additional metabolites, viz., cholestan-19-ol-3-one (2 mg), cholest-4-en-19-ol-3-one (10 mg), and cholest-5-en-3&#223;,19-diol (12 mg). Similar results were also obtained when n-propanol was used instead of &#945;,&#945;'-bipyridyl. Resting cells grown on 19-HCA readily converted both 5&#945;-androst-1-en-19-ol-3,17-dione and androst-4-en-19-ol-3,17-dione into estrone. Partially purified 1,2-dehydrogenase from steroid-induced Moraxella cells transformed androst-4-en-19-ol-3,17-dione into estrone and formaldehyde in the presence of phenazine methosulfate, an artificial electron acceptor. These results suggest that the degradation of the hydrocarbon side chain of 19-HCA does not proceed via C22 phenolic acid intermediates and complete removal of the C17 side chain takes place prior to the aromatization of the A ring in estrone. The mode of degradation of the sterol side chain appears to be through the fission of the C17-C20 bond. On the basis of these observations, a new pathway for the formation of estrone from 19-HCA in Moraxella sp. has been proposed

Rotating fermions in two dimensions: Thomas Fermi approach

Properties of confined mesoscopic systems have been extensively studied numerically over recent years. We discuss an analytical approach to the study of finite rotating fermionic systems in two dimension. We first construct the energy functional for a finite fermionic system within the Thomas-Fermi approximation in two dimensions. We show that for specific interactions the problem may be exactly solved. We derive analytical expressions for the density, the critical size as well as the ground state energy of such systems in a given angular momentum sector.Comment: Latex 15 pages, 3 ps. figures. Poster in SCES-Y2K, held at SAHA Institute of Nuclear Physics,Calcutta,October (2000

Magnetic phenomena at and near nu =1/2 and 1/4: theory, experiment and interpretation

I show that the hamiltonian theory of Composite Fermions (CF) is capable of yielding a unified description in fair agreement with recent experiments on polarization P and relaxation rate 1/T_1 in quantum Hall states at filling nu = p/(2ps+1), at and near nu = 1/2 and 1/4, at zero and nonzero temperatures. I show how rotational invariance and two dimensionality can make the underlying interacting theory behave like a free one in a limited context.Comment: Latex 4 pages, 2 figure

Structure of 9α,19-dihydroxy-4-androstene-3,17-dione

C19H26O4, M1 = 318.41, orthorhombic, P212121, a = 10.591 (1), b = 11.133 (1), c = 13.657 (2) Å, V – 1610.29 Å3, Z = 4, Dm (flotation in KI) = 1.301, Dx = 1.313 g cm-3, Mo Kα, Å = 0.7107 Å, μ = 0.85 cm-1, F(000) = 688, T = 293 K, R – 0.057 for 1253 significant reflections. The Å ring is disordered with atoms C(2) and O(19) occupying two possible sites. The molecules are held together by a hydrogen bond [O(9)…O(17) = 2.89 Å]

Clinico-epidemiological study of stasis eczema

Background: This study was done to determine the epidemiological aspects of stasis eczema and the association of various risk factors of the disease in the local population.Methods: This cross-sectional study was done at a tertiary hospital in southern India over a period of 1 year. Epidemiological and clinical data of stasis dermatitis patients above 20 years of age were recorded. Data was tabulated and analyzed using Microsoft excel software.Results: Of the study population of 120 prevalence is found to be highest in the age group of 50 to 60 years (42.5%) and males are more commonly affected. Occupation involving prolonged standing or sitting and lack of exercise activity is found to be a significant risk factor. The commonest skin finding in present study is eczema (80%). The most common complication was ulcer which was seen in 12.5% of our patients. Reticular veins are the most common dilated veins seen in our patients. About 70% of patients in present study fall under C4a stage of CEAP classification. About one half of symptomatic patients in present study (53.3%) had no radiological evidence of incompetent veins. Among patients with valvular incompetence, perforator veins were most commonly found to be incompetent (62.5%) followed by involvement of the saphenous venous system (23.2%).Conclusions: The study confirms the importance of environmental factors in the development of stasis eczema. There is a ten-fold higher prevalence of the disease in men in our population compared to previous studies which invariably reports a female preponderance