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Search Results: 1 - 10 of 139676 matches for " Birinchi K. Sarma "
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Genetic Patterns of Domestication in Pigeonpea (Cajanus cajan (L.) Millsp.) and Wild Cajanus Relatives
Mulualem T. Kassa, R. Varma Penmetsa, Noelia Carrasquilla-Garcia, Birinchi K. Sarma, Subhojit Datta, Hari D. Upadhyaya, Rajeev K. Varshney, Eric J. B. von Wettberg, Douglas R. Cook
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039563
Abstract: Pigeonpea (Cajanus cajan) is an annual or short-lived perennial food legume of acute regional importance, providing significant protein to the human diet in less developed regions of Asia and Africa. Due to its narrow genetic base, pigeonpea improvement is increasingly reliant on introgression of valuable traits from wild forms, a practice that would benefit from knowledge of its domestication history and relationships to wild species. Here we use 752 single nucleotide polymorphisms (SNPs) derived from 670 low copy orthologous genes to clarify the evolutionary history of pigeonpea (79 accessions) and its wild relatives (31 accessions). We identified three well-supported lineages that are geographically clustered and congruent with previous nuclear and plastid sequence-based phylogenies. Among all species analyzed Cajanus cajanifolius is the most probable progenitor of cultivated pigeonpea. Multiple lines of evidence suggest recent gene flow between cultivated and non-cultivated forms, as well as historical gene flow between diverged but sympatric species. Evidence supports that primary domestication occurred in India, with a second and more recent nested population bottleneck focused in tropical regions that is the likely consequence of pigeonpea breeding. We find abundant allelic variation and genetic diversity among the wild relatives, with the exception of wild species from Australia for which we report a third bottleneck unrelated to domestication within India. Domesticated C. cajan possess 75% less allelic diversity than the progenitor clade of wild Indian species, indicating a severe “domestication bottleneck” during pigeonpea domestication.
Controllable optical bistability and cooling of a mechanical oscillator in a hybrid optomechanical system
Bijita Sarma,Amarendra K. Sarma
Physics , 2015,
Abstract: We investigate theoretically the effect of optical feedback from a cavity containing an ultracold two level atomic ensemble, on the bistable behavior shown by mean intracavity optical field in an optomechanical cavity resonator. It turns out that the optical bistability can be controlled by tuning the frequency and power of the driving laser and is largely affected by the presence of the atomic ensemble in the feedback cavity. In essence, our work emphasizes the possibility of realization of a controllable optical switch depending on the hybrid interaction, commanding lower threshold power than a single optomechanical cavity. Further, we study the aspect of optomechanical cooling of the mechanical oscillator in this hybrid system and the time evolution of the mean phonon number indicates ground-state cooling of the oscillator in the unresolved sideband regime.
Optical bistability and cooling of a mechanical oscillator induced by radiation pressure in a hybrid optomechanical system
Bijita Sarma,Amarendra K. Sarma
Physics , 2015,
Abstract: We investigate theoretically the effect of optical feedback from a cavity containing an ultracold two level atomic ensemble, on the bistable behavior shown by mean intracavity optical field and the ground state cooling effect of the mechanical oscillator in an optomechanical cavity resonator. The optical bistability can be controlled by tuning the frequency and power of the single driving laser as well as by varying the atom-cavity coupling strength in the atomic cavity. Study of the cooling of the mechanical oscillator, in both good and bad cavity limits, reveals that the hybrid system is more efficient in cooling in comparison to a generic optomechanical setup, even at room temperature. In essence, our work emphasizes the impact of the coupling with the atomic cavity on the radiation pressure effects in the optomechanical cavity.
Cavity optomechanical cooling of a mechanical resonator in presence of a quantum well
Bijita Sarma,Amarendra K. Sarma
Physics , 2015,
Abstract: Ground state cooling of micromechanical oscillator is a paradigmatic goal for observing quantum mechanical effects in cavity optomechanics. We study theoretically the ground state cooling of a mechanical oscillator in an optomechanical cavity in presence of a quantum well placed inside the cavity. Due to mode tailoring in presence of the quantum well, the cavity response gets modified and leads to asymmetric heating and cooling processes. This facilitates the cooling of the mechanical oscillator even in the unresolved-sideband regime, via inhibition of Stokes scattering.
Decay-Time Asymmetries at the B-Factories
K. V. L. Sarma
Physics , 1993, DOI: 10.1007/BF02908086
Abstract: Absract (Invited talk at the X DAE High Energy Physics symposium in December 1992, held at Tata Institute of Fundamental Research, Bombay)
Nobel Leptons
K. V. L. Sarma
Physics , 1995,
Abstract: The 1995 Nobel Prize in Physics is shared equally by the American physicists Frederick J. Reines and Martin L. Perl for their pioneering experimental contributions to lepton physics. Following is a brief account of their discoveries.
Recent Results in Neutrino Physics
K. V. L. Sarma
Physics , 1994, DOI: 10.1142/S0217751X9500036X
Abstract: This is a survey of the current experimental information on some of the interesting issues in neutrino physics: neutrino species, neutrino masses, neutrino magnetic moments, solar neutrinos, and the atmospheric neutrino anomaly.
Solitary wave solution to the generalized nonlinear Schrodinger equation for dispersive permittivity and permeability
Amarendra K. Sarma
Physics , 2010, DOI: 10.1140/epjd/e2011-10288-0
Abstract: We present a solitary wave solution of the generalized nonlinear Schrodinger equation for dispersive permittivity and permeability using a scaling transformation and coupled amplitude-phase formulation. We have considered the third-order dispersion effect (TOD) into our model and show that soliton shift may be suppressed in a negative index material by a judicious choice of the TOD and self-steepening parameter.
Modulation instability in nonlinear complex parity-time (PT) symmetric periodic structures
Amarendra K. Sarma
Physics , 2014, DOI: 10.1364/JOSAB.31.001861
Abstract: We carry out a modulation instability (MI) analysis in nonlinear complex parity-time (PT) symmetric periodic structures. All the three regimes defined by the PT-symmetry breaking point or threshold, namely, below threshold, at threshold and above threshold are discussed. It is found that MI exists even beyond the PT-symmetry threshold indicating the possible existence of solitons or solitary waves, in conformity with some recent reports. We find that MI does not exist at the PT-symmetry breaking point in the case of normal dispersion below a certain nonlinear threshold. However, in the case of anomalous dispersion regime, MI does exist even at the PT-symmetry breaking point.
Modulational instability of few cycle pulses in optical fibers
Amarendra K. Sarma
Physics , 2010, DOI: 10.1209/0295-5075/92/24004
Abstract: We investigate the modulational instability of a mathematical model [based on the model proposed by T. Brabec and F. Krausz, Phys.Rev. Lett. 78, 3282(1997)] appropriate for few cycle optical pulses with pulse duration as short as one carrier oscillation cycle in the context of a standard silica fiber operating at the telecommunication wavelength 1550 nm.
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