70 research outputs found
An Analytical Study on the Multi-critical Behaviour and Related Bifurcation Phenomena for Relativistic Black Hole Accretion
We apply the theory of algebraic polynomials to analytically study the
transonic properties of general relativistic hydrodynamic axisymmetric
accretion onto non-rotating astrophysical black holes. For such accretion
phenomena, the conserved specific energy of the flow, which turns out to be one
of the two first integrals of motion in the system studied, can be expressed as
a 8 degree polynomial of the critical point of the flow configuration.
We then construct the corresponding Sturm's chain algorithm to calculate the
number of real roots lying within the astrophysically relevant domain of
. This allows, for the first time in literature, to {\it
analytically} find out the maximum number of physically acceptable solution an
accretion flow with certain geometric configuration, space-time metric, and
equation of state can have, and thus to investigate its multi-critical
properties {\it completely analytically}, for accretion flow in which the
location of the critical points can not be computed without taking recourse to
the numerical scheme. This work can further be generalized to analytically
calculate the maximal number of equilibrium points certain autonomous dynamical
system can have in general. We also demonstrate how the transition from a
mono-critical to multi-critical (or vice versa) flow configuration can be
realized through the saddle-centre bifurcation phenomena using certain
techniques of the catastrophe theory.Comment: 19 pages, 2 eps figures, to appear in "General Relativity and
Gravitation
Hepatobiliary and pancreatic tuberculosis: A two decade experience
<p>Abstract</p> <p>Background</p> <p>Isolated hepatobiliary or pancreatic tuberculosis (TB) is rare and preoperative diagnosis is difficult. We reviewed our experience over a period two decades with this rare site of abdominal tuberculosis.</p> <p>Methods</p> <p>The records of 18 patients with proven histological diagnosis of hepatobiliary and pancreatic tuberculosis were reviewed retrospectively. The demographic features, sign and symptoms, imaging, cytology/histopathology, procedures performed, outcome and follow up data were obtained from the departmental records. The diagnosis of tuberculosis was based on granuloma with caseation necrosis on histopathology or presence of acid fast bacilli.</p> <p>Results</p> <p>Of 18 patients (11 men), 11 had hepatobiliary TB while 7 had pancreatic TB. Two-thirds of the patients were < 40 years (mean: 42 yrs; range 19–70 yrs). The duration of the symptoms varied between 2 weeks to 104 weeks (mean: 20 weeks). The most common symptom was pain in the abdomen (n = 13), followed by jaundice (n = 10), fever, anorexia and weight loss (n = 9). Five patients (28%) had associated extra-abdominal TB which helped in preoperative diagnosis in 3 patients. Imaging demonstrated extrahepatic bile duct obstruction in the patients with jaundice and in addition picked up liver, gallbladder and pancreatic masses with or without lymphadenopathy (peripancreatic/periportal). Preoperative diagnosis was made in 4 patients and the other 14 were diagnosed after surgery. Two patients developed significant postoperative complications (pancreaticojejunostomy leak <abbrgrp><abbr bid="B1">1</abbr></abbrgrp> intraabdominal abscess <abbrgrp><abbr bid="B1">1</abbr></abbrgrp>) and 3 developed ATT induced hepatotoxicity. No patient died. The median follow up period was 12 months (9 – 96 months).</p> <p>Conclusion</p> <p>Tuberculosis should be considered as a differential diagnosis, particularly in young patients, with atypical signs and symptoms coming from areas where tuberculosis is endemic and preoperative tissue and/or cytological diagnosis should be attempted before labeling them as hepatobiliary and pancreatic malignancy.</p
Peasants' Choices? Indian Agriculture and the Limits of Commercialization in Nineteenth-Century Bihar
The article attempts to distinguish and locate choices in agricultural production, with special reference to Bihar, India, during the nineteenth century. On the one hand, it considers closely managed and extensively irrigated areas, long involved in trade under the overall control of 'landlords', and, on the other hand, the expanding production of opium, and also of indigo and sugar (so-called 'forced' commercialization), identifying common features and continuities of production and marketing. Particular the importance of advance payments and local intermediaries is stressed. Thus, in contrast with the more usual evolutionary models, based on unitary categories and modes, the essay illustrates ecological, customary, collective, and local political constraints upon agricultural decisions; and this leads to the identification in turn of their different kinds and levels
Maritime order and connectivity in the Indian Ocean: the renewed significance of the Bay of Bengal
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Cerebral Cortical Lesions in Multiple Sclerosis Detected by MR Imaging at 8 Tesla
BACKGROUND AND PURPOSE:
Conventional imaging of ex-vivo brain at 1.5T in multiple sclerosis (MS) detects only a small fraction of the gray matter cerebral cortical lesions that can be detected by pathology. Our purpose was to examine if imaging at 8T can detect plaques in cortical gray matter (CGM) not evident at 1.5T.
METHODS:
An ex-vivo brain obtained at autopsy from a patient with MS was formalin fixed and 1 cm coronal slices were examined using MR imaging at 8T.
RESULTS:
Numerous cerebral cortical lesions not evident at 1.5T were seen at 8T. Lesions were easily identified using gradient-echo and spin-echo (SE) as well as diffusion images. MR imaging at 8T identified many of the types of plaques previously evident only by pathology. The magnitude of the cortical involvement in this 1 patient was severe. Lesions in the gray matter readily visible by high-field MR imaging were sometimes barely visible by pathology. MR imaging at 8T often facilitated the detection of such plaques by pathology.
CONCLUSION:
This study establishes the utility of high-field imaging at 8T in the delineation of plaques in the cerebral CGM in MS
Spatial inventory and ecological status of coral reefs of the Central Indian Ocean using Resourcesat-1
684-696Spatial inventory
of coral reef habitat at eco-morphological level has been carried out for the
Central Indian Ocean (CIO) using Resourcesat-1 satellite data. CIO covers
India, Sri Lanka, Bangladesh, Maldives and the British Indian Ocean Territory.
A comprehensive classification system has been evolved and standardized to map
the coral reefs of CIO. Coral reefs of the CIO occupy 18,252.13 sq km area.
Maldivian and Indian reefs cover 79.63% (14533.60 sq km) and 13.06% (2383.87 sq
km) of CIO reef area respectively. Coral reefs of British Indian Ocean
Territory enjoy pristine ecological status among the CIO reefs. In India,
Lakshadweep followed by Andaman and Nicobar islands have certain reefs which
may be termed as pristine with the rest being in vulnerable condition. Gulf of
Kachchh reefs are in degraded condition. Sri Lankan reefs are also in
vulnerable condition. Banladesh has a single reef which is in degrading
condition. This inventory is the first of its kind providing baseline data not
only for management and conservation but also forms an important input for
climate change studies
Ordning och Kaos : En receptionskritisk granskning av Jordan B. Petersons bibliska bruk av kön och sexualitet, samt hur hans narrativ förhåller sig till historisk-kritiska och feministiska läsningar av Genesis 1-3
It has recently been proposed that the model plant, Arabidopsis thaliana thale cress, uses a newly discovered genetic repair system to repair errors at the genetic level. A. thaliana uses information from the grandparent's genes as a basis for this correction --- so genetic information appears to skip a generation. We apply this gene repair strategy to a combinatory optimization problem, firstly comparing the performance of parent and grandparent based repair. Subsequent experiments expand our understanding of the GeneRepair algorithm, by examining the parameters of fitness and direction involved in the generepair process. Our results point to a tentative explanation as to why A. thaliana might have evolved such an apparently complex inheritance process
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