108 research outputs found
Parametric triggering of vortices in toroidally trapped rotating Bose-Einstein condensates
We study the creation of vortices by triggering the rotating Bose-Einstein
condensates in a toroidal trap with trap parameters such as laser beam waist
and Gaussian potential depth. By numerically solving the time-dependent
Gross-Pitaevskii equation in two dimensions, we observe a change in vortex
structure and a considerable increase in the number of vortices when the waist
of the irradiated laser beam is in consonance with the area of the condensate
as we vary the Gaussian potential depth. By computing the root mean square
radius of the condensate, we confirm the variation in the number of vortices
generated as a function of the ratio between the root-mean-square radius of the
condensate and the laser beam waist. In particular, the number of hidden
vortices reaches the maximum value when the above ratio is close to the value
0.7. We find the variation in the number of vortices is rapid for deeper
Gaussian potentials, and we conclude that the larger beam waist and deeper
Gaussian potentials generate more vortices. Further, we calculate the number of
vortices using the Feynman rule with Thomas Fermi approximation and compare
them with the numerical results. We also observe that the critical rotation
frequency decreases with an increase in depth of Gaussian potential.Comment: 14 pages, 11 figure
Scaling and synchronization in a ring of diffusively coupled nonlinear oscillators
Chaos synchronization in a ring of diffusively coupled nonlinear oscillators
driven by an external identical oscillator is studied. Based on numerical
simulations we show that by introducing additional couplings at -th
oscillators in the ring, where is an integer and is the maximum
number of synchronized oscillators in the ring with a single coupling, the
maximum number of oscillators that can be synchronized can be increased
considerably beyond the limit restricted by size instability. We also
demonstrate that there exists an exponential relation between the number of
oscillators that can support stable synchronization in the ring with the
external drive and the critical coupling strength with a scaling
exponent . The critical coupling strength is calculated by numerically
estimating the synchronization error and is also confirmed from the conditional
Lyapunov exponents (CLEs) of the coupled systems. We find that the same scaling
relation exists for couplings between the drive and the ring. Further, we
have examined the robustness of the synchronous states against Gaussian white
noise and found that the synchronization error exhibits a power-law decay as a
function of the noise intensity indicating the existence of both noise-enhanced
and noise-induced synchronizations depending on the value of the coupling
strength . In addition, we have found that shows an
exponential decay as a function of the number of additional couplings. These
results are demonstrated using the paradigmatic models of R\"ossler and Lorenz
oscillators.Comment: Accepted for Publication in Physical Review
Local dimension and finite time prediction in spatiotemporal chaotic systems
We show how a recently introduced statistics [Patil et al, Phys. Rev. Lett.
81 5878 (2001)] provides a direct relationship between dimension and
predictability in spatiotemporal chaotic systems. Regions of low dimension are
identified as having high predictability and vice-versa. This conclusion is
reached by using methods from dynamical systems theory and Bayesian modelling.
We emphasize in this work the consequences for short time forecasting and
examine the relevance for factor analysis. Although we concentrate on coupled
map lattices and coupled nonlinear oscillators for convenience, any other
spatially distributed system could be used instead, such as turbulent fluid
flows.Comment: 5 pagers, 7 EPS figure
Optimization and Analysis of Wireless Networks Lifetime using Soft Computing for Industrial Applications
Recently, wireless networks are applied in various engineering and industrial applications. One of the critical problems in wireless network system optimization in intelligent applications is obtaining an adequate energy fairness level. This issue can be resolved by applying effective cluster-based routing optimization with multi-hop routing. Hence a new network structure is developed that is derived from energy consumption architecture by applying soft computing strategies such as evolutionary operators in determining the exact clusters for optimizing energy consumption. The new effective evolutionary operators are tested in the optimization of a lifetime. The proposed method is simulated for different values of the routing factor, α, for different types of networks. The energy levels range from 0.4 to 0.8, achieving good results for nearly 2500 rounds. The proposed strategy optimizes the clusters, and its head is selected reliably. The optimization of cluster head choice has been done based on the base station distance, the energy of the node, and the node's energy efficiency. The reliability of the long-distance nodes is increased during the data transmission by modifying the size of the area of the candidate set of nodes in contrast the near-distance node's energy consumption is reduced. For the energy levels that range from 0.4 to 0.8, the higher network throughput is obtained at the same time network lifetime is optimized compared to other well-known approaches. The proposed model is expected for different industrial wireless network applications to optimize the systems during the long-run simulation and to achieve high reliability and sustainability
Free expansion of fermionic dark solitons in a boson-fermion mixture
We use a time-dependent dynamical mean-field-hydrodynamic model to study the
formation of fermionic dark solitons in a trapped degenerate fermi gas mixed
with a Bose-Einstein condensate in a harmonic as well as a periodic
optical-lattice potential. The dark soliton with a "notch" in the probability
density with a zero at the minimum is simulated numerically as a nonlinear
continuation of the first vibrational excitation of the linear
mean-field-hydrodynamic equations, as suggested recently for pure bosons. We
study the free expansion of these dark solitons as well as the consequent
increase in the size of their central notch and discuss the possibility of
experimental observation of the notch after free expansion.Comment: 14 pages, 6 figure
Experimental and numerical study of chemiluminescence characteristics in premixed counterflow flames of methane based fuel blends
Non-intrusive chemiluminescence measurements have been used as heat release rate and equivalence ratio indicators for gas turbine combustor active control. In the present study, measurements and modelling of OH*, CH(A)*, C 2 *, and CO 2 * chemiluminescence are used to examine chemiluminescence sensing of heat release rate and equivalence ratio in premixed counterflow methane – air flames with equivalence ratio from 0.6 to 1.3 and strain rate from 80 to 400 s -1 . Two spectrally resolved detecting optical systems were used to detect spatially-averaged (global) and spatially resolved (local) chemiluminescence characteristics in the reaction zone. A recently published reaction mechanism 1 for the chemiluminescence of the OH*, CH*, and C 2 * species is incorporated to GRI-Mech 3.0. The augmented mechanism is further validated against the experimental results of the present study and is used to predict the chemiluminescence characteristics of premixed counterflow methane – air flames. The mechanism includes OH* chemiluminescence formation paths from hydrogen reaction, which have not been evaluated before in premixed counterflow flames. The CHEMKIN based counterflow flame code, OPPDIF is employed to simulate the experiments. The calculated OH* and CH(A)* chemiluminescence agrees well with the experimental results measured by both optical methods. Both the experimental and numerical results demonstrate the ability of OH* and CH(A)* intensities to mark heat release rate in methane – air flames. Overall, CH* may be preferable for heat release rate sensing applications at elevated equivalence ratio and strain rate. For equivalence ratio sensing in methane combustion, the measured and simulated OH*/CH(A)* chemiluminescent intensity ratio is highly dependent on equivalence ratio and nearly independent of strain rate. Thus, this ratio can be used to monitor equivalence ratio. However, a non-monotonic behavior of the OH*/CH* ratio for very lean combustion (ER < 0.7) is observed, in agreement with previous studies. This behavior can be reproduced by the reaction mechanisms. The behavior of OH*/CH(A)* chemiluminescent intensity ratio for flames of methanepropane blends are also calculated with the detailed chemistry model. The addition of propane in methane modifies the behaviour of OH*/CH(A)* chemiluminescent intensity ratio dramatically. However, the numerical results suggest that the OH*/CH(A)* chemiluminescent intensity ratio is an indicator of equivalence ratio in lean methanepropane fuel blended flames
Polar Invasion and Translocation of Neisseria meningitidis and Streptococcus suis in a Novel Human Model of the Blood-Cerebrospinal Fluid Barrier
Acute bacterial meningitis is a life-threatening disease in humans. Discussed as entry sites for pathogens into the brain are the blood-brain and the blood-cerebrospinal fluid barrier (BCSFB). Although human brain microvascular endothelial cells (HBMEC) constitute a well established human in vitro model for the blood-brain barrier, until now no reliable human system presenting the BCSFB has been developed. Here, we describe for the first time a functional human BCSFB model based on human choroid plexus papilloma cells (HIBCPP), which display typical hallmarks of a BCSFB as the expression of junctional proteins and formation of tight junctions, a high electrical resistance and minimal levels of macromolecular flux when grown on transwell filters. Importantly, when challenged with the zoonotic pathogen Streptococcus suis or the human pathogenic bacterium Neisseria meningitidis the HIBCPP show polar bacterial invasion only from the physiologically relevant basolateral side. Meningococcal invasion is attenuated by the presence of a capsule and translocated N. meningitidis form microcolonies on the apical side of HIBCPP opposite of sites of entry. As a functionally relevant human model of the BCSFB the HIBCPP offer a wide range of options for analysis of disease-related mechanisms at the choroid plexus epithelium, especially involving human pathogens
Basics of Bose-Einstein Condensation
The review is devoted to the elucidation of the basic problems arising in the
theoretical investigation of systems with Bose-Einstein condensate.
Understanding these challenging problems is necessary for the correct
description of Bose-condensed systems. The principal problems considered in the
review are as follows: (i) What is the relation between Bose-Einstein
condensation and global gauge symmetry breaking? (ii) How to resolve the
Hohenberg-Martin dilemma of conserving versus gapless theories? (iii) How to
describe Bose-condensed systems in strong spatially random potentials? (iv)
Whether thermodynamically anomalous fluctuations in Bose systems are
admissible? (v) How to create nonground-state condensates? Detailed answers to
these questions are given in the review. As examples of nonequilibrium
condensates, three cases are described: coherent modes, turbulent superfluids,
and heterophase fluids.Comment: Review articl
Properties, production, and applications of camelid single-domain antibody fragments
Camelids produce functional antibodies devoid of light chains of which the single N-terminal domain is fully capable of antigen binding. These single-domain antibody fragments (VHHs or Nanobodies®) have several advantages for biotechnological applications. They are well expressed in microorganisms and have a high stability and solubility. Furthermore, they are well suited for construction of larger molecules and selection systems such as phage, yeast, or ribosome display. This minireview offers an overview of (1) their properties as compared to conventional antibodies, (2) their production in microorganisms, with a focus on yeasts, and (3) their therapeutic applications
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