212 research outputs found
The Barrier Method: A Technique for Calculating Very Long Transition Times
In many dynamical systems there is a large separation of time scales between
typical events and "rare" events which can be the cases of interest. Rare-event
rates are quite difficult to compute numerically, but they are of considerable
practical importance in many fields: for example transition times in chemical
physics and extinction times in epidemiology can be very long, but are quite
important. We present a very fast numerical technique that can be used to find
long transition times (very small rates) in low-dimensional systems, even if
they lack detailed balance. We illustrate the method for a bistable
non-equilibrium system introduced by Maier and Stein and a two-dimensional (in
parameter space) epidemiology model.Comment: 20 pages, 8 figure
Computation of nucleation of a non-equilibrium first-order phase transition using a rare-event algorithm
We introduce a new Forward-Flux Sampling in Time (FFST) algorithm to
efficiently measure transition times in rare-event processes in non-equilibrium
systems, and apply it to study the first-order (discontinuous) kinetic
transition in the Ziff-Gulari-Barshad model of catalytic surface reaction. The
average time for the transition to take place, as well as both the spinodal and
transition points, are clearly found by this method.Comment: 12 pages, 10 figure
Evaluation of mulberry tree leaves based diets in Corriedale lambs
An experiment was conducted in two phases; phase-I, five experimental rations were prepared with incorporation of mulberry leaf meals replacing concentrates @ 0% (C), 20% (TR1), 40% (TR2), 60% (TR3) and 80% (TR4), respectively and TR4 was found the best in terms of IVDM, IVOM and IVNDF digestibility. In phase-II, TR4 was made in two forms, mash and CFBs and were fed to six corriedale lambs in group T1 and T2, respectively. The control group (C) was fed with conventional ration prepared in mash form as per NRC 1985. The fortnightly dry matter intake expressed as per cent of body weight in C, T1 and T2 groups were 3.77, 3.90 and 4.07, respectively, and were statistically significant between T2 and control group with highest value in T2 group. The digestibility coefficients of DM, OM, CP, EE and NDF differ significantly amongst the groups with highest values observed in group T2 followed by T1 and control. However, digestibility coefficient of CF differ significantly between control and other groups (T1 and T2), which were statistically at par with each other. However, the digestibility coefficient values of NFE differed significantly between T2 group and other groups that showed statistically non-significant. The DCP and TDN values differed significantly with positive balances of all nutrients amongst all treatment groups. Results revealed that mulberry leaves can replace up to 80% of concentrate mixture in corriedale lambs especially in CFB forms with positive effect on nutrient intake, digestibility and balances
The Harmonic Measure for critical Potts clusters
We present a technique, which we call "etching," which we use to study the
harmonic measure of Fortuin-Kasteleyn clusters in the Q-state Potts model for
Q=1-4. The harmonic measure is the probability distribution of random walkers
diffusing onto the perimeter of a cluster. We use etching to study regions of
clusters which are extremely unlikely to be hit by random walkers, having
hitting probabilities down to 10^(-4600). We find good agreement between the
theoretical predictions of Duplantier and our numerical results for the
generalized dimension D(q), including regions of small and negative q.Comment: 20 pages, 10 figure
Probing the dynamics and coherence of a semiconductor hole spin via acoustic phonon-assisted excitation
Spins in semiconductor quantum dots are promising local quantum memories to
generate polarization-encoded photonic cluster states, as proposed in the
pioneering Rudolph-Lindner scheme [1]. However, harnessing the polarization
degree of freedom of the optical transitions is hindered by resonant excitation
schemes that are widely used to obtain high photon indistinguishability. Here
we show that acoustic phonon-assisted excitation, a scheme that preserves high
indistinguishability, also allows to fully exploit the polarization selective
optical transitions to initialise and measure single spin states. We access the
coherence of hole spin systems in a low transverse magnetic field and directly
monitor the spin Larmor precession both during the radiative emission process
of an excited state or in the quantum dot ground state. We report a spin state
detection fidelity of granted by the optical selection rules
and a ~ns hole spin coherence time, demonstrating the potential of this
scheme and system to generate linear cluster states with a dozen of photonsComment: 3 figure
Lidocaine-loaded fish scale-nanocellulose biopolymer composite microneedles
Microneedle (MN) technology has emerged as an effective drug delivery system, and it has tremendous potential as a patient friendly substitute for conventional methods for transdermal drug delivery (TDD). In this paper, we report on the preparation of lidocaine-loaded biodegradable microneedles, which are manufactured from fish scale-derived collagen. Lidocaine, a common tissue numbing anaesthetic, is loaded in these microneedles with an aim of delivering the drug with controlled skin permeation. Evaluation of lidocaine permeation in porcine skin has been successfully performed using Franz diffusion cell (FDC) which has shown that the drug permeation rate increases from 2.5 to 7.5% w/w after 36 h and pseudo steady state profile is observed from 5.0 to 10.0% w/w lidocaine-loaded microneedle. Swelling experiments have suggested that the microneedles have negligible swellability which implies that the patch would stick to the tissue when inserted. The experiments on MN dissolution have depicted that the lidocaine loaded in the patch is lower than the theoretical loading, which is expected as there can be losses of the drug during initial process manufacture
Analysis of Genetic Diversity of Persea bombycina ‘‘Som’’ Using RAPD-Based Molecular Markers
The utility of RAPD markers in assessing genetic diversity and phenetic
relationships in Persea bombycina, a major tree species for golden silk (muga)
production, was investigated using 48 genotypes from northeast India. Thirteen
RAPD primer combinations generated 93 bands. On average, seven RAPD fragments
were amplified per reaction. In a UPGMA phenetic dendrogram based on
Jaccard’s coefficient, the P. bombycina accessions showed a high level of genetic
variation, as indicated by genetic similarity. The grouping in the phenogram was
highly consistent, as indicated by high values of cophenetic correlation and high
bootstrap values at the key nodes. The accessions were scattered on a plot derived
from principal correspondence analysis. The study concluded that the high level of
genetic diversity in the P. bombycina accessions may be attributed to the species’
outcrossing nature. This study may be useful in identifying diverse genetic stocks of
P. bombycina, which may then be conserved on a priority basis
Exploring pre-main sequence variables of ONC: The new variables
Since 2004, we have been engaged in a long-term observing program to monitor
young stellar objects in the Orion Nebula Cluster. We have collected about two
thousands frames in V, R, and I broad-band filters on more than two hundred
nights distributed over five consecutive observing seasons. The high-quality
and time-extended photometric data give us an opportunity to address various
phenomena associated with young stars. The prime motivations of this project
are i) to explore various manifestations of stellar magnetic activity in very
young low-mass stars; ii) to search for new pre-main sequence eclipsing
binaries; and iii) to look for any EXor and FUor like transient activities
associated with YSOs. Since this is the first paper on this program, we give a
detailed description of the science drivers, the observation and the data
reduction strategies as well. In addition to these, we also present a large
number of new periodic variables detected from our first five years of
time-series photometric data. Our study reveals that about 72% of CTTS in our
FoV are periodic, whereas, the percentage of periodic WTTS is just 32%. This
indicates that inhomogeneities patterns on the surface of CTTS of the ONC stars
are much more stable than on WTTS. From our multi-year monitoring campaign we
found that the photometric surveys based on single-season are incapable of
identifying all periodic variables. And any study on evolution of angular
momentum based on single-season surveys must be carried out with caution.Comment: Accepted for publication by MNRAS, 26 pages, 17 figures, 6 table
Counter-current chromatography for the separation of terpenoids: A comprehensive review with respect to the solvent systems employed
Copyright @ 2014 The Authors.This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.Natural products extracts are commonly highly complex mixtures of active compounds and consequently their purification becomes a particularly challenging task. The development of a purification protocol to extract a single active component from the many hundreds that are often present in the mixture is something that can take months or even years to achieve, thus it is important for the natural product chemist to have, at their disposal, a broad range of diverse purification techniques. Counter-current chromatography (CCC) is one such separation technique utilising two immiscible phases, one as the stationary phase (retained in a spinning coil by centrifugal forces) and the second as the mobile phase. The method benefits from a number of advantages when compared with the more traditional liquid-solid separation methods, such as no irreversible adsorption, total recovery of the injected sample, minimal tailing of peaks, low risk of sample denaturation, the ability to accept particulates, and a low solvent consumption. The selection of an appropriate two-phase solvent system is critical to the running of CCC since this is both the mobile and the stationary phase of the system. However, this is also by far the most time consuming aspect of the technique and the one that most inhibits its general take-up. In recent years, numerous natural product purifications have been published using CCC from almost every country across the globe. Many of these papers are devoted to terpenoids-one of the most diverse groups. Naturally occurring terpenoids provide opportunities to discover new drugs but many of them are available at very low levels in nature and a huge number of them still remain unexplored. The collective knowledge on performing successful CCC separations of terpenoids has been gathered and reviewed by the authors, in order to create a comprehensive document that will be of great assistance in performing future purifications. © 2014 The Author(s)
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