Tapering photonic crystal fibers for generating self-similar ultrashort pulses at 1550 nm

K.S.N. wishes to thank the Council of Scientific and Industrial Research [No. 03(1264)/12/EMR-11] Government of India for the financial support.Peer reviewedPublisher PD

Nearly chirp- and pedestal-free pulse compression in nonlinear fiber Bragg gratings

Peer reviewedPublisher PD

Fission-fusion dynamics and group-size dependent composition in heterogeneous populations

Many animal groups are heterogeneous and may even consist of individuals of different species, called mixed-species flocks. Mathematical and computational models of collective animal movement behaviour, however, typically assume that groups and populations consist of identical individuals. In this paper, using the mathematical framework of the coagulation-fragmentation process, we develop and analyse a model of merge and split group dynamics, also called fission-fusion dynamics, for heterogeneous populations that contain two types (or species) of individuals. We assume that more heterogeneous groups experience higher split rates than homogeneous groups, forming two daughter groups whose compositions are drawn uniformly from all possible partitions. We analytically derive a master equation for group size and compositions and find mean-field steady-state solutions. We predict that there is a critical group size below which groups are more likely to be homogeneous and contain the abundant type/species. Despite the propensity of heterogeneous groups to split at higher rates, we find that groups are more likely to be heterogeneous but only above the critical group size. Monte-Carlo simulation of the model show excellent agreement with these analytical model results. Thus, our model makes a testable prediction that composition of flocks are group-size dependent and do not merely reflect the population level heterogeneity. We discuss the implications of our results to empirical studies on flocking systems.Comment: 19 pages, 8 figure

Designing a Biosensor Using a Photonic Quasi-Crystal Fiber with Fan-shaped Analyte Channel

Postprin

Generation of a train of ultrashort pulses using periodic waves in tapered photonic crystal fibres

Funding This work was supported by the Ministry of Education , Nigeria for financial support through the TETFUND scholarship 55 scheme; CSIR [grant number 03(1264)/12/EMR-II].Peer reviewedPostprin

Translationally Invariant Non-Fermi-Liquid Metals with Critical Fermi Surfaces: Solvable Models

We construct examples of translationally invariant solvable models of strongly correlated metals, composed of lattices of Sachdev-Ye-Kitaev dots with identical local interactions. These models display crossovers as a function of temperature into regimes with local quantum criticality and marginal-Fermi-liquid behavior. In the marginal-Fermi-liquid regime, the dc resistivity increases linearly with temperature over a broad range of temperatures. By generalizing the form of interactions, we also construct examples of non-Fermi liquids with critical Fermi surfaces. The self-energy has a singular frequency dependence but lacks momentum dependence, reminiscent of a dynamical mean-field-theory-like behavior but in dimensions d<∞. In the low-temperature and strong-coupling limit, a heavy Fermi liquid is formed. The critical Fermi surface in the non-Fermi-liquid regime gives rise to quantum oscillations in the magnetization as a function of an external magnetic field in the absence of quasiparticle excitations. We discuss the implications of these results for local quantum criticality and for fundamental bounds on relaxation rates. Drawing on the lessons from these models, we formulate conjectures on coarse-grained descriptions of a class of intermediate-scale non-Fermi-liquid behavior in generic correlated metals

Lump-like Structures in Scalar-field Models

In this work we investigate the presence of lump-like solutions in models described by a single real scalar field. We take advantage of a procedure recently used to describe explicit analytical solutions and we study several distinct models, showing how the parameters can be used to control the specific features of the lump-like structures. The proposed models are of direct interest to the construction of q-balls, to induce tachyonic excitations and gravitating structures of nontopological profile on braneworld models with a single extra dimension, to map solitons in optical fibers, and to describe collective excitations in Bose-Einstein condensates.Comment: 7 pages, 11 figure

Formulation and Evaluation of Pregabalin Loaded Eudragit S100 Nanoparticles

In this work, polymeric nanoparticles containing Pregabalin was prepared and optimized the ideal concentration of polymer based on its in vitro release profile for a period of 24hrs.The nanoparticles were prepared by solvent displacement method using various concentrations of Eudragit S100 (EPNP1-EPNP5). The prepared nanoparticles were characterized for its particle size, zeta potential, drug content, entrapment efficiency and invitro drug release profile. The preformulation study results confirmed the compatibility between the drug and other excipients used in the formulation. The optimized formulation was selected based on its particle size, entrapment efficiency and in vitro drug release profile. The formulation which contains 300mg of Eudragit S100 (EPNP5) was selected as optimized concentration for the controlled release of Pregabalin for a period of 24hrs

Pedestal free pulse compression of chirped optical solitons

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タミルナドゥ州の異なる農業気候地域のための気候変動に関連する複合脆弱性指標の開発

インドの農業は気象、特に降水量の変動に大きく影響を受ける。インド亜大陸の降水量の８０％は６月から９月の３ヶ月間に起こり、南西モンスーンとなる。旱魃がある地域で問題となる一方、洪水も別の地域で人間生活と農業にとって被害を及ぼし、平均的に氾濫しやすい土地の約３分の１は農地である。洪水となる過剰な雨量、不作をもたらす旱魃、財産に損害を与えるサイクロン等、気候の負の影響へは迅速な対応が求められる。その時々に気候の影響に対する社会の対処能力が試される。歴史的に社会の対処能力は地域的に試されてきており、社会は気候の変動にレジリアンスを持つ様に適応してきた。脆弱性とはその地域にすむ人口の経済システムの状態であり、また社会経済的な特徴でもある。本稿では、脆弱性の社会経済的な観点から、地域の発展段階およびさらに発展する能力を計る指標に焦点を当てた。Anand and Sen (1994)によって人間開発指標(Human Development Index: HDI)を計算するために開発された脆弱性指標の方法を基本とし、人口の脆弱性、気候の脆弱性、農業の脆弱性、就業の脆弱性を含めた。タミルナドゥ州の異なる農業気候地域で1980-2001 年までの３期間の指標を７地域で比較した結果、高降水量地域が一番脆弱性が高いことが明らかになった。脆弱性指標は、脆弱性をモニターし、脆弱性を低下させるための対策を開発し、優先順位を考え、またそれらの対策の効果を検討する際に潜在的に有効な方法であろう。和文のものは、英文の内容を要約したもの