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

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Generation of Bragg solitons through modulation instability in a Bragg grating structure

In this article, we consider the continuous wave (cw) propagation through the nonlinear periodic structure that consists of alternating layers of both positive and negative Kerr coefficients along the propagation direction. We investigate the modulational instability (MI) conditions required for the generation of ultrashort pulses for the nonlinearity management system. We study the occurrence of MI at the top and bottom edges of the photonic band gap (PBG) where the forward and backward propagating waves are strongly coupled because of the presence of the grating structure. We also study the MI when cw is detuned from the edges of the PBG into the anomalous and normal dispersion regimes. In addition, we discuss the existence of gap solitons for the nonlinearity management system in the upper and lower branches of the dispersion curve through the MI gain spectra. We observe the generation of higher order solitons in the nonlinear periodic structure when the input power is increased beyond a certain critical level. Finally, we discuss the generation of higher order Bragg grating solitons through the intensity evolution of the forward and backward propagating fields

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

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

Method Development and Validation for the Simultaneous Estimation of Esomeprazole and Levosulpiride by using RPHPLC in its bulk and pharmaceutical dosage form

Esomeprazole is a compound that inhibits gastric acid secretion and is indicated in the treatment of gastroesophageal reflux disease (GERD), the healing of erosive esophagitis, and H. pylori eradication to reduce the risk of duodenal ulcer recurrence. Esomeprazole belongs to a new class of antisecretory compounds, the substituted benzimidazoles, that do not exhibit anticholinergic or H2 histamine antagonistic properties, but that suppress gastric acid secretion by specific inhibition of the H+/K+ATPase at the secretory surface of the gastric parietal cell. By doing so, it inhibits acid secretion into the gsatric lumen. This effect is dose-related and leads to inhibition of both basal and stimulated acid secretion irrespective of the stimulus. A simple, Accurate, precise method was developed for the simultaneous estimation of the esomeprazole and levosulpiride in Tablet dosage form. Chromatogram was run through ODS (150mm 4.6mm, 5μ). Mobile phase containing Buffer and Acetonitrie in the ratio of 32;68A was pumped through column at a flow rate of 1ml/min. Buffer used in this method was 0.01N KH2PO4 pH 5.4 buffer. Temperature was maintained at 30°C. Optimized wavelength for Esomeprazole and Levosulpiride was 290nm. Retention time of Esomeprazole and Levosulpiride were found to be 2.2min and 4.0min. %RSD of the Esomeprazole and Levosulpiride were and found to be 0.97 and 0.50 respectively. %Recover was Obtained as 100.08% and 101.16% for Esomeprazole and Levosulpiride respectively. LOD, LOQ values are obtained from regression equations of Esomeprazole and Levosulpiride were 0.10ppm, 0.34ppm and 1.04ppm, 0.29ppm respectively. Regression equation of Esomeprazole is y = 10568.x + 307.3, and of Levosulpiride is y = 11649.x + 1207

A Comparative study of Post TURP Outcome and Complications between BPH Patients Presenting With Or Without Acute Urinary Retention

INTRODUCTION : The prevalence rate of AUR in men with BPH is reported as high as 53%. Higher mortality and morbidity rates following TURP have been reported in previous studies. In our study we tried to analyze the post TURP complications between patients presenting with and without AUR AIM AND OBJECTIVE : To compare the post TURP outcome and complications of BPH patients presenting with and without AUR. MATERIALS AND METHODS : This is a prospective study. Patients who are admitted in Kilpauk Medical College and Govt Royapettah Hospital with LUTS due to BPH with and without AUR are included in the study. The study period was between January 2014 to December 2014, and totally 126 patients participated in this study, 74 with AUR and 52 AUR. Patients evaluated with History & Physical examination, DRE, USG KUB, and Uroflow & PVR. Patients who were more than 70 years, men with neurological disease, prostate cancer, urethral stricture, previous prostate or urethral surgery were excluded from this study. All patients were subjected to TURP using monopolar current with water as irrigation fluid. Post operative variables like TUR syndrome, persistent haematuria, need of blood transfusion, Post op UTI, sepsis, recatheterisation rate, resurgery, post op stricture, LUTS, Q max, PVR and length of hospital stay were compared between these groups RESULTS : Our study shows that the complications rate were more with patients who presented with AUR. Out of the above said complications, post op UTI, recatheterisation rate and length of hospital stay were significantly higher in AUR group. CONCLUSION : It is better to intervene earlier before the patients develop AUR in order to minimize the complications and to maximize the outcome

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

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Diabetes Mellitus: Can Stem Cells be the Answer?

This review aims to enlighten the readers regarding the past, present and future of stem cells in the treatment of Diabetes. Diabetes is one of the leading causes of morbidity and mortality, affecting more than 415 million people worldwide. It is estimated that one in ten adults will have diabetes by 2030. Diabetes is mainly due to reduction in β-cell mass which are responsible for insulin production. Exogenous administration of insulin is having good impact on restoring glucose homeostasis, but it does not entirely control the minute-to-minute fluctuations in systemic blood glucose. Recently cellular-based therapies have been established for exogenous insulin administration by modern pump technology. One of the most interesting therapies involves substitution of insulin producing islet cells by transplantation. But lack of donor material and lifelong immunosuppression made the technique unfeasible. These restrictions have led to exploration of other sources of β-cells, one of the prospects being the stem cells. Several types of stem cells have been used to make pancreatic β-cells, including human embryonic stem cells / induced pluripotent stem cells, pancreatic stem / progenitor cells, and non-pancreatic stem cells. There is also evidence of adult β-cells regeneration through β-cell replication and cellular reprogramming. Functional restoration of existing β-cells, transplantation of stem cells or stem cell-derived β-like cells might provide new opportunities for treatment. In conclusion it can be said that the research is still wide open to arrive at the efficient reprogramming of various types of stem cells to destine them towards functional β-cells

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