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21.
Anindya Datta Amitava Raychaudhuri Sreerup Raychaudhuri Surajit Chakrabarti 《Zeitschrift fur Physik C Particles and Fields》1996,72(3):449-460
Many extensions of the Standard Model includeSU(2) L ×U(1) Y singlet higgs bosons,h 0, and also vector-like fermions which couple to it. The production and detection possibilities of such singlet neutral scalars at hadron colliders are considered for different scenarios of vectorlike fermions. We find that for some values of masses and couplings, detection at the CERN large hadron collider (LHC) appears to be a distinct possibility, while at the Fermilab Tevatron upgrade theh 0 might be observed only in very favourable circumstances. 相似文献
22.
23.
Surajit?Dasgupta Neven?Bilic Tapas?K.?DasEmail author 《General Relativity and Gravitation》2005,37(11):1877-1890
We demonstrate that a spherical accretion onto astrophysical black holes, under the influence of Newtonian or various post-Newtonian
pseudo-Schwarzschild gravitational potentials, may constitute a concrete example of classical analogue gravity naturally found
in the Universe. We analytically calculate the corresponding analogue Hawking temperature as a function of the minimum number
of physical parameters governing the accretion flow. We study both the polytropic and the isothermal accretion. We show that
unlike in a general relativistic spherical accretion, analogue white hole solutions can never be obtained in such post-Newtonian
systems. We also show that an isothermal spherical accretion is a remarkably simple example in which the only one information–the
temperature of the fluid, is sufficient to completely describe an analogue gravity system. For both types of accretion, the
analogue Hawking temperature may become higher than the usual Hawking temperature. However, the analogue Hawking temperature
for accreting astrophysical black holes is considerably lower compared with the temperature of the accreting fluid. 相似文献
24.
We report measurements of birefringence
of several nematic liquid crystals having transverse as well as longitudinal dipole moments in thin (1.4 to
) and thick (7 to
cells. Rubbed polyimide-coated glass plates are used to get planar alignment of the nematic director in these cells. We find significant enhancement (6 to
) of
(
, where S is the orientational order parameter) in thin cells in all compounds with aromatic cores even at temperatures far (
C) below the nematic-isotropic transition point. The enhancement is larger in compounds having several phenyl rings and lower if the number of phenyl rings is reduced. In a compound that does not have an aromatic core no significant enhancement is observed, implying that the strength of the surface potential depends on the aromaticity of the cores. Assuming a perfect orientational order at the surface, calculations based on the Landau-de Gennes theory show that the thickness averaged enhancement of S is sharply reduced as the temperature is lowered in the nematic phase. The measured order parameter S is further enhanced in thin cells because of the stiffening of the elastic constant which reduces the thermal fluctuations of the nematic director. The combined effect is however too small at low temperatures to account for the experimental data.Received: 22 February 2004, Published online: 24 May 2004PACS:
61.30.-v Liquid crystals - 61.30.Pq Microconfined liquid crystals: droplets, cylinders, randomly confined liquid crystals, polymer dispersed liquid crystals, and porous systems - 61.30.Hn Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitionsSurajit Dhara: Present address: Department of Physics, Birla Institute of Technology and Science, Pilani 333 031, India. 相似文献
25.
In this present investigation, we describe the steady state current voltage (I–V) characteristic of Crystal violet dye dispersed
solid state photoelectrochemical cell (PEC). Typical behavior of dark current-voltage characteristic by increasing and decreasing
external bias voltage has a similar form like hysterisis in nature. Although we have already observed this hysterisis nature
in case of both forward and reverse bias condition, yet it is clear that the reverse hysterisis curve is more prominent than
forward hysterisis. In this paper, we are getting double values of current (I) for a single value voltage, which is also helpful
to understand the charge transport process through disordered materials. As the bias increases, the distribution of traps
depth, which is exponential in nature, changes toward order state (resulting increase in disordered parameter α) This means
that as α increases, it tends to reach the most order state of material. When external bias voltage is at 3.5 V, the value
of disorder parameter becomes 1, and when bias voltage is beyond 3.5 V, the diffusion comes enhanced in nature. 相似文献
26.
Surajit Saha Surjeet Singh R. Suryanarayanan A.K. Sood 《Journal of solid state chemistry》2011,184(8):2204-2208
Here we report a temperature-dependent Raman study of the pyrochlore “dynamic spin-ice” compound Pr2Sn2O7 and compare the results with its non-pyrochlore (monoclinic) counterpart Pr2Ti2O7. In addition to phonon modes, we observe two bands associated with electronic Raman scattering involving crystal field transitions in Pr2Sn2O7 at ∼135 and 460 cm−1 which couple strongly to phonons. Anomalous temperature dependence of phonon frequencies that are observed in pyrochlore Pr2Sn2O7 are absent in monoclinic Pr2Ti2O7. This, therefore, confirms that the strong phonon-phonon anharmonic interactions, responsible for the temperature-dependent anomalous behavior of phonons, arise due to the inherent vacant sites in the pyrochlore structure. 相似文献
27.
Domadia PN Bhunia A Ramamoorthy A Bhattacharjya S 《Journal of the American Chemical Society》2010,132(51):18417-18428
Lipopolysaccharide (LPS) provides a well-organized permeability barrier at the outer membrane of Gram-negative bacteria. Host defense cationic antimicrobial peptides (AMPs) need to disrupt the outer membrane before gaining access to the inner cytoplasmic membrane or intracellular targets. Several AMPs are largely inactive against Gram-negative pathogens due to the restricted permeation through the LPS layer of the outer membrane. MSI-594 (GIGKFLKKAKKGIGAVLKVLTTG) is a highly active AMP with a broad-spectrum of activities against bacteria, fungi, and virus. In the context of LPS, MSI-594 assumes a hairpin helical structure dictated by packing interactions between two helical segments. Residue Phe5 of MSI-594 has been found to be engaged in important interhelical interactions. In order to understand plausible structural and functional inter-relationship of the helical hairpin structure of MSI-594 with outer membrane permeabilization, a mutant peptide, termed MSI-594F5A, containing a replacement of Phe5 with Ala has been prepared. We have compared antibacterial activities, outer and inner membrane permeabilizations, LPS binding affinity, perturbation of LPS micelles structures by MSI-594 and MSI-594F5A peptides. Our results demonstrated that the MSI-594F5A has lower activities against Gram-negative bacteria, due to limited permeabilization through the LPS layer, however, retains Gram-positive activity, akin to MSI-594. The atomic-resolution structure of MSI-594F5A has been determined in LPS micelles by NMR spectroscopy showing an amphipathic curved helix without any packing interactions. The 3D structures, interactions, and activities of MSI-594 and its mutant MSI-594F5A in LPS provide important mechanistic insights toward the requirements of LPS specific conformations and outer membrane permeabilization by broad-spectrum antimicrobial peptides. 相似文献
28.
Surajit Chattopadhyay Ujjal Debnath 《International Journal of Theoretical Physics》2011,50(2):315-324
Purpose of the present paper is to view the correspondence between Ricci and other dark energies. We have considered the Ricci
dark energy in presence of dark matter in non-interacting situation. Subsequently, we have derived the pressure and energy
density for Ricci dark energy. The equation of state parameter has been generated from these pressure and energy density.
Next, we have considered the correspondence between Ricci and other dark energy models, namely tachyonic field, DBI-essence
and new agegraphic dark energy without any interaction and investigated possible cosmological consequences. 相似文献
29.
Dipak Ghosh Argha Deb Subrata Biswas Pasupati Mandal Asok Kumar Mallick Prabir Kumar Haldar 《Indian Journal of Physics》2009,83(10):1463-1485
This paper presents an investigation of compound hadrons (pions and protons) distribution emitted from 24Mg-AgBr and 12C-AgBr interactions both at 4.5 AGeV and 32S-AgBr interactions at 200 AGeV. The study includes azimuthal correlations (two particle and three particle), azimuthal asymmetry
and fractal behaviour. This paper reveals some interesting results. 相似文献
30.
Membrane Disruption and Enhanced Inhibition of Cell‐Wall Biosynthesis: A Synergistic Approach to Tackle Vancomycin‐Resistant Bacteria
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Venkateswarlu Yarlagadda Dr. Sandip Samaddar Dr. Krishnamoorthy Paramanandham Dr. Bibek R. Shome Dr. Jayanta Haldar 《Angewandte Chemie (International ed. in English)》2015,54(46):13644-13649
Resistance to glycopeptide antibiotics, the drugs of choice for life‐threatening bacterial infections, is on the rise. In order to counter the threat of glycopeptide‐resistant bacteria, we report development of a new class of semi‐synthetic glycopeptide antibiotics, which not only target the bacterial membrane but also display enhanced inhibition of cell‐wall biosynthesis through increased binding affinity to their target peptides. The combined effect of these two mechanisms resulted in improved in vitro activity of two to three orders of magnitude over vancomycin and no propensity to trigger drug resistance in bacteria. In murine model of kidney infection, the optimized compound was able to bring bacterial burden down by about 6 logs at 12 mg kg?1 with no observed toxicity. The results furnished in this report emphasize the potential of this class of compounds as future antibiotics for drug‐resistant Gram‐positive infections. 相似文献