1,920 research outputs found
Evolution of electromagnetic and Dirac perturbations around a black hole in Horava gravity
The evolution of electromagnetic and Dirac perturbations in the spacetime
geometry of Kehagias-Sfetsos(KS) black hole in the deformed Horava-Lifshitz(HL)
gravity is investigated and the associated quasinormal modes are evaluated
using time domain integration and WKB methods. We find a considerable deviation
in the nature of field evolution in HL theory from that in the Schwarzschild
spacetime and QNMs region extends over a longer time in HL theory before the
power-law tail decay begins. The dependence of the field evolution on the HL
parameter are studied. In the time domain picture we find that the
length of QNM region increases with . But the late time decay of field
follows the same power-law tail behavior as in the case of Schwarzschild black
hole.Comment: The article was fully rewritten, references added, to appear in MPL
The index of projective families of elliptic operators: the decomposable case
An index theory for projective families of elliptic pseudodifferential operators is developed under two conditions. First, that the twisting, i.e. Dixmier-Douady, class is in H2(X; Z)[H1(X; Z) H3(X; Z) and secondly that the 2-class part is trivialized on the total space of the fibration. One of the features of this special case is that the corresponding Azumaya bundle can be refined to a bundle of smoothing operators. The topological and the analytic index of a projective family of elliptic operators associated with the smooth Azumaya bundle both take values in twisted K-theory of the parameterizing space and the main result is the equality of these two notions of index. The twisted Chern character of the index class is then computed by a variant of Chern-Weil theory.V. Mathai, R.B. Melrose and I.M. Singe
Probiotic effects of lactic acid bacteria against Vibrio alginolyticus in Penaeus (Fenneropenaeus) indicus (H. Milne Edwards)
Cell free extracts of four strains of Lactic acid bacteria (LAB) viz. Lactobacillus. acidophilus,
Streptococcus.cremoris, Lactobacillus bulgaricus –56 and Lactobacillus bulgaricus –57 inhibited
growth of Vibrio alginolyticus in nutrient broth. The antagonism of LAB to Vibrio
alginolyticus was further confirmed by streak plating wherein suppression of growth of Vibrio
was obtained.
Juveniles of Penaeus indicus (average weight 0.985 ± 0.1 g) on administering orally a
moist feed base containing 5 × 106 cells·g of the four LAB probionts for a period of four weeks
showed better survival (56 to 72%) when challenged with V. alginolyticus by intra-muscular
injection of 0.1 ml containing 3 × 109 cells·ml. Animals maintained on a diet devoid of bacterial
biomass exhibited 80% mortality
T-duality for principal torus bundles
In this paper we study T-duality for principal torus bundles with H-flux. We
identify a subset of fluxes which are T-dualizable, and compute both the dual
torus bundle as well as the dual H-flux. We briefly discuss the generalized
Gysin sequence behind this construction and provide examples both of non
T-dualizable and of T-dualizable H-fluxes.Comment: 9 pages, typos removed and minor corrections mad
Experimental Assessment of Mouse Sociability Using an Automated Image Processing Approach
Mouse is the preferred model organism for testing drugs designed to increase sociability. We present a method to quantify mouse sociability in which the test mouse is placed in a standardized apparatus and relevant behaviors are assessed in three different sessions (called session I, II, and III). The apparatus has three compartments (see Figure 1), the left and right compartments contain an inverted cup which can house a mouse (called “stimulus mouse”). In session I, the test mouse is placed in the cage and its mobility is characterized by the number of transitions made between compartments. In session II, a stimulus mouse is placed under one of the inverted cups and the sociability of the test mouse is quantified by the amounts of time it spends near the cup containing the enclosed stimulus mouse vs. the empty inverted cup. In session III, the inverted cups are removed and both mice interact freely. The sociability of the test mouse in session III is quantified by the number of social approaches it makes toward the stimulus mouse and by the number of times it avoids a social approach by the stimulus mouse. The automated evaluation of the movie detects the nose of the test mouse, which allows the determination of all described sociability measures in session I and II (in session III, approaches are identified automatically but classified manually). To find the nose, the image of an empty cage is digitally subtracted from each frame of the movie and the resulting image is binarized to identify the mouse pixels. The mouse tail is automatically removed and the two most distant points of the remaining mouse are determined; these are close to nose and base of tail. By analyzing the motion of the mouse and using continuity arguments, the nose is identified. © 2016 Journal of Visualized Experiments
Fast and Compact Distributed Verification and Self-Stabilization of a DFS Tree
We present algorithms for distributed verification and silent-stabilization
of a DFS(Depth First Search) spanning tree of a connected network. Computing
and maintaining such a DFS tree is an important task, e.g., for constructing
efficient routing schemes. Our algorithm improves upon previous work in various
ways. Comparable previous work has space and time complexities of bits per node and respectively, where is the highest
degree of a node, is the number of nodes and is the diameter of the
network. In contrast, our algorithm has a space complexity of bits
per node, which is optimal for silent-stabilizing spanning trees and runs in
time. In addition, our solution is modular since it utilizes the
distributed verification algorithm as an independent subtask of the overall
solution. It is possible to use the verification algorithm as a stand alone
task or as a subtask in another algorithm. To demonstrate the simplicity of
constructing efficient DFS algorithms using the modular approach, We also
present a (non-sielnt) self-stabilizing DFS token circulation algorithm for
general networks based on our silent-stabilizing DFS tree. The complexities of
this token circulation algorithm are comparable to the known ones
Validation of EORTC quality-of-life questionnaire in Indian women with operable breast cancer
Background: The European Organization for Research and Treatment of Cancer (EORTC) module QLQ-C30 and the breast cancer-specific module BR-23 have been validated world-wide to assess the quality of life ( QOL) in women with breast cancer. No such study has been published on Indian women using EORTC questionnaires. Methods: QOL was assessed in relation to surgery, adjuvant chemotheraphy, radiation therapy and hormone therapy in 299 Indian women with operable breast cancer (OBC) at the Breast Unit of Tata Memorial Hospital( TMH), Mumbai, from October 1998 to September 2001. The QLQ-C30 module was used to assess physical health, emotional, cognitive and social functioning, and the BR-23 module to assess breast cancer treatment-related symptoms. Assessment was done at 3 visits: visit 1 ( after surgery); visit 2 ( during adjuvant therapy) and visit 3 ( on completion of adjuvant therapy). Results: Of the 299 women at first visit, 274 (91.6%) completed the visit 2 questionnaire and 239 ( 80%) completed the visit 3 questionnaire. Only those women who filled the questionnaires at all 3 visits were included as 'valid visits' for analysis ( 193 of 299; 64.5%). The reliability and validity of the English and translated versions of the questionnaires were tested by Cronbach alpha (0.61-0.96) and item-scale correlation (0.63-0.93). Women with breast conversion treatment had a superior body image as compared to those with mastectomy (p<0.01). Physical, emotional and cognitive functions were not related to the type of surgery. Global QOL, physical, sexual and role functioning were found to deteriorate with chemo-therapy ( p≤0.01). Radiotherapy had only local adverse wffects (p<0.001), while hormone theraphy had no adverse impact on QOL. Conclusion: QLQ-C30 and BR-23 questionnaires can be used reliably to assess QOL in Indian patients. The translated versions were found to be valid for further use in clinical trials on Indian women with breast cancer
Universality in the emergence of oscillatory instabilities in turbulent flows
Spontaneous emergence of periodic oscillations due to self-organization is
ubiquitous in turbulent flows. The emergence of such oscillatory instabilities
in turbulent fluid mechanical systems is often studied in different
system-specific frameworks. We uncover the existence of a universal scaling
behaviour during self-organization in turbulent flows leading to oscillatory
instability. Our experiments show that the spectral amplitude of the dominant
mode of oscillations scales inversely with the Hurst exponent of a fluctuating
state variable following an inverse power law relation. Interestingly, we
observe the same power law behaviour with a constant exponent near -2 across
various turbulent systems such as aeroacoustic, thermoacoustic and aeroelastic
systems.Comment: 5 pages, 4 figures and supplementary informatio
Global strain-induced scalar potential in graphene devices
By mechanically distorting a crystal lattice it is possible to engineer the
electronic and optical properties of a material. In graphene, one of the major
effects of such a distortion is an energy shift of the Dirac point, often
described as a scalar potential. We demonstrate how such a scalar potential can
be generated systematically over an entire electronic device and how the
resulting changes in the graphene work function can be detected in transport
experiments. Combined with Raman spectroscopy, we obtain a characteristic
scalar potential consistent with recent theoretical estimates. This direct
evidence for a scalar potential on a macroscopic scale due to deterministically
generated strain in graphene paves the way for engineering the optical and
electronic properties of graphene and similar materials by using external
strain
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