Biomedical subjects
Publications and source records attributed to D Biswas.
Polygonalization of any smooth billiard boundary can be carried out in several ways. We show here that the semiclassical description depends on the polygonalization process and the results can be inequivalent. We also establish that generalized tangent polygons are closest to the corresponding smooth billiard and for de Broglie wavelengths larger than the average length of the edges, the two are semiclassically equivalent.
Periodic orbits are the central ingredients of modern semiclassical theories and corrections to these are generally nonclassical in origin. We show here that, for the class of generic polygonal billiards, the corrections are predominantly classical in origin owing to the contributions from closed almost-periodic (CAP) orbit families. Furthermore, CAP orbit families outnumber periodic families but have comparable weights. They are hence indispensable for semiclassical quantization.
Intermittent or marginally stable repellers are commonly associated with a power law decay in the survival fraction. We demonstrate how the presence of weak additive noise alters the spectrum of the Perron-Frobenius operator significantly, giving rise to exponential decays even in systems that are otherwise regular. Implications for ballistic transport in marginally stable miscrostructures are also discussed.
Campylobacter jejuni isolates obtained from human and animal sources showed different invasion levels into human embryonic intestinal (INT-407) cells. There was no significant relation between the degree of invasion and cytotoxins production. The depolymerization of both microfilaments by cytochalasin-D and microtubules by colchicine, demecolcine and nocodazole or stabilization of microtubules by paclitaxel reduced the invasiveness of C. jejuni, although microfilament depolymerization showed greater inhibition than microtubule depolymerization. Interference with receptor-mediated endocytosis by G-strophanthin and monodansylcadaverine and inhibition of endosome acidification by monensin reduced the number of viable intracellular C. jejuni cells. Furthermore inhibition of only host protein kinases by staurosporine, but not phosphoinositide 3-kinase by wortmannin or protein kinase-C by calphostin-C, significantly reduced invasion of epithelial cells by C. jejuni. These data suggest that the internalization mechanism triggered by C. jejuni is strikingly different from the microfilament-dependent invasion mechanism exhibited by many of the well-studied enteric bacteria such as enteroinvasive strains of Escherichia coli, Salmonella typhimurium, Shigella flexneri, Yersinia enterocolitica and Yersinia pseudotuberculosis.
A cross sectional study on hypertension was done on 294 subjects aged 30 years and above. 150 households were selected randomly representing 50 households from each locality inhabited exclusively by the rural Mizos, indigenous rural Assamese and the tea-garden workers respectively, in the northeastern region of India. Blood pressure was measured by sphygmo-manometer in sitting posture. Anthro-pometric measurements were taken using standard procedure for measuring height, weight, waist and hip girth. Information on age, sex, ethnicity, literacy, alcohol intake, smoking pattern, physical activity, occupation, amount of salt consumption was collected using a standard and pre-tested questionnaire. Significant differences were observed in both the systolic and diastolic blood pressure levels among the three different ethnic groups selected for this study (p < 0.0001). Multiple regression analyses indicated that in Mizos, age, waist circumference and alcohol intake were independently associated with increase in systolic blood pressure whereas smoking was found to be negatively associated with systolic blood pressure (R2 = 0.391, p < 0.001). Factors, which were the best predictors of diastolic blood pressure, were age and body mass index [(kg/m2) (R2 = 0.227, p < 0.001)]. In the rural Assamese population, the best predictors of systolic blood pressure were age and waist circumference (R2 = 0.263, p = 0.018). For the diastolic blood pressure, age, alcohol intake and body mass index were important correlates (R2 = 0.131, p < 0.001). In the tea garden community, important predictors of systolic blood pressure were age, gender and marital status (R2 = 0.187, p < 0.001). On the other hand, age and alcohol intake were best predictors for diastolic blood pressure (R2 = 0.09, p < 0.001).
The reasons of virulent resurgence of malaria and the measures adopted for its control in a metropolitan city by Calcutta Municipal Corporation is discussed in detail along with proper references. Publicity compaign, especially among school students, has been stressed.
A Shigella flexneri strain, cured of the large 220-kb virulence plasmid, expresses adhering and invading ability in confluent monolayers of HeLa cells similar to its parent strain. Invasion by both the parent and the cured strains resulted in alteration of the monomeric actin (G) in the total actin pool of HeLa cells. Other indicators of invasive characteristics of virulent Shigella strains such as production of keratoconjunctivitis in guinea pig eye in vivo, Congo red binding and expression of contact hemolysin however, indicated loss of invasive properties in the plasmid cured strain. Further, pretreatment of bacterial cells with para-bromophenacyl bromide (p-BPB), a specific chemical inhibitor of phospholipase A, adversely affected adhesion to and invasion of HeLa cells in vitro, irrespective of the presence of the 220-kb plasmid indicating the possible involvement of the enzyme phospholipase A in the invasion process. Adherence of both the strains to guinea pig colonic epithelial cells (CECs) in vitro was reduced significantly on pretreatment of bacteria or CECs with p-BPB. Expression of exocellular enzymes viz. protease, elastase, phospholipase A and phospholipase C were not related to the large plasmid.
The zeros of the Husimi function provide a minimal description of individual quantum eigenstates and their distribution is of considerable interest. We provide here a numerical study for pseudointegrable billiards which suggests that the zeros tend to diffuse over phase space in a manner reminiscent of chaotic systems but nevertheless contain a subtle signature of pseudointegrability. We also find that the zeros depend sensitively on the position and momentum uncertainties (Delta q and Delta p, respectively) with the classical correspondence best when Delta q = Delta p = square root of [Planck's constant/2]. Finally, short-range correlations seem to be well described by the Ginibre ensemble of complex matrices.
105 workers of 29 roadside restaurants along a highway in Assam were interviewed for their habits, educational status and were examined for their hygienic status and presence of communicable diseases (STDs,TB etc). Most of them were young, males with 40% literacy; more than half were unmarried. About 30% of them were alcoholic and smokers and 2.9% were addicted to cannabis. The hygienic conditions of the workers were poor. More than one third had sexual contact with multiple sex partners or commercial sex workers and 2% were engaged in homosexual activity. Most of them did not use condom. 25.7% of them had genital lesions suggestive of sexually transmitted disease, 11.8% showed gram negative diplococci in urethral smears and 5.1% were VDRL reactive. Skin infections followed by gastrointestinal disorders and respiratory tract infections were other prevalent problems. 70.6% were positive for intestinal parasites and 22.2% were sputum positive for acid fast bacilli. However all the collected blood samples were negative for HIV.
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A laboratory-based study of diagnosed bacterial meningitis in the national paediatric hospital identified 852 cases of meningitis in the 8-year period 1987-1994. There were 587 culture-positive cases, of which Haemophilus influenzae (47%) and Streptococcus pneumoniae (32%) accounted for 80%. H. influenzae showed a remarkable increase of 700% during the study period. Most of the H. influenzae cases (90%) occurred in the 1st 2 years of life. Analysis of culture-negative specimens by antigen detection in the last 2 years also revealed the predominance of H. influenzae (71.4%) and S. pneumoniae (22.4%). Typing of H. influenzae isolates during this time showed that 98% of the strains were type b. This retrospective hospital-based study indicated a pronounced increase in the incidence of H. influenzae meningitis and strongly supports the need for large-scale Hib vaccination for young children. However, such nationwide intervention will probably need to be based on a prospective on a prospective and population-based surveillance of H. influenzae infections.
One hundred sixty-five invasive Streptococcus pneumoniae strains were isolated from children under five at Dhaka Shishu (Children's) Hospital during the period 1992 to 1995. Ninety-four strains were from cerebrospinal fluid, and 71 were from blood. More than 91% of the strains were isolated from patients aged 24 months or less. Predominant serotypes were, in descending order 7F, 12F, 14, 15B, 18, 5, and 22A. These comprised 70% of all isolates. The marked differences in serotype distribution in different countries indicate the need for a sentinel surveillance study for the countries of South Asia, particularly Bangladesh, China, India, and Pakistan.
A seven year old girl in a rural area of Upper Assam was found to be infected with Fasciola hepatica. The girl gave history of eating watercress. Besides the presence of eggs in the stools, her liver was enlarged and tender. Liver function tests revealed hepato-biliary involvement with increase in serum AKP and ALT. Ultrasonography revealed presence of adult fluke in gall bladder, and a marginal thickening of gall bladder wall. However, the echo pattern of her liver parenchyma was normal. The case is reported for its public health significance and is a maiden report from north eastern India.
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Fourteen strains of Shigella spp. were isolated from patients aged 5-12 yr, hospitalized with dysentery during 1995-1996. The strains isolated were Shigella dysenteriae 1, S. flexneri and S.sonnei. All but one of the 14 strains were sensitive to ciprofloxacin and norfloxacin. The MIC of both the fluoroquinolones was 15 micrograms/ml for the resistant S.dysenteriae 1 strain (NRM4). Therefore, the careful use of antimicrobials is required for therapy of Shigellosis.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.