278 research outputs found
Scaling and front dynamics in Ising quantum chains
We study the relaxation dynamics of a quantum Ising chain initially prepared
in a product of canonical states corresponding each to an equilibrium state of
part of the chain at a given temperature. We focus our attention on the
transverse magnetization for which a general expression is given. Explicite
results are given for the completely factorized initial state, corresponding to
a situation where all the spins are thermalized independently, and for the
two-temperatures initial state, where part of the chain called the system is
thermalized at a temperature and the remaining part is at a temperature
.Comment: 7 pages, submitted to EPJ
Network Evolution Induced by the Dynamical Rules of Two Populations
We study the dynamical properties of a finite dynamical network composed of
two interacting populations, namely; extrovert () and introvert (). In
our model, each group is characterized by its size ( and ) and
preferred degree ( and ). The network dynamics
is governed by the competing microscopic rules of each population that consist
of the creation and destruction of links. Starting from an unconnected network,
we give a detailed analysis of the mean field approach which is compared to
Monte Carlo simulation data. The time evolution of the restricted degrees
\moyenne{k_{bb}} and \moyenne{k_{ab}} presents three time regimes and a non
monotonic behavior well captured by our theory. Surprisingly, when the
population size are equal , the ratio of the restricted degree
\theta_0=\moyenne{k_{ab}}/\moyenne{k_{bb}} appears to be an integer in the
asymptotic limits of the three time regimes. For early times (defined by
) the total number of links presents a linear evolution, where
the two populations are indistinguishable and where .
Interestingly, in the intermediate time regime (defined for
and for which ), the system reaches a
transient stationary state, where the number of contacts among introverts
remains constant while the number of connections is increasing linearly in the
extrovert population. Finally, due to the competing dynamics, the network
presents a frustrated stationary state characterized by a ratio .Comment: 21 pages, 6 figure
Fourier's law on a one-dimensional optical random lattice
We study the transport properties of a one-dimensional hard-core bosonic
lattice gas coupled to two particle reservoirs at different chemical potentials
which generate a current flow through the system. In particular, the influence
of random fluctuations of the underlying lattice on the stationary-state
properties is investigated. We show analytically that the steady-state density
presents a linear profile. The local steady-state current obeys the Fourier law
where is a typical timescale of the lattice
fluctuations and the density gradient imposed by the reservoirs.Comment: 9 pages, 2 figure
Relaxation in the XX quantum chain
We present the results obtained on the magnetisation relaxation properties of
an XX quantum chain in a transverse magnetic field. We first consider an
initial thermal kink-like state where half of the chain is initially
thermalized at a very high temperature while the remaining half, called
the system, is put at a lower temperature . From this initial state, we
derive analytically the Green function associated to the dynamical behaviour of
the transverse magnetisation. Depending on the strength of the magnetic field
and on the temperature of the system, different regimes are obtained for the
magnetic relaxation. In particular, with an initial droplet-like state, that is
a cold subsystem of finite size in contact at both ends with an infinite
temperature environnement, we derive analytically the behaviour of the
time-dependent system magnetisation
Out-of-equilibrium bosons on a one-dimensional optical random lattice
We study the transport properties of a one-dimensional hard-core boson
lattice gas coupled to two particle reservoirs at different chemical potentials
generating a current flow through the system. In particular, the influence of
random fluctuations of the underlying lattice on the stationary state
properties is investigated. We show analytically that the steady-state density
presents a linear profile. The local steady-state current obeys the Fourier law
where is a typical timescale of the
lattice fluctuations and the density gradient imposed %on the
system by the reservoirs
Regulation by small RNAs via coupled degradation: mean-field and variational approaches
Regulatory genes called small RNAs (sRNAs) are known to play critical roles
in cellular responses to changing environments. For several sRNAs, regulation
is effected by coupled stoichiometric degradation with messenger RNAs (mRNAs).
The nonlinearity inherent in this regulatory scheme indicates that exact
analytical solutions for the corresponding stochastic models are intractable.
Here, we present a variational approach to analyze a well-studied stochastic
model for regulation by sRNAs via coupled degradation. The proposed approach is
efficient and provides accurate estimates of mean mRNA levels as well as higher
order terms. Results from the variational ansatz are in excellent agreement
with data from stochastic simulations for a wide range of parameters, including
regions of parameter space where mean-field approaches break down. The proposed
approach can be applied to quantitatively model stochastic gene expression in
complex regulatory networks.Comment: 4 pages, 3 figure
Analytical results for a stochastic model of gene expression with arbitrary partitioning of proteins
In biophysics, the search for analytical solutions of stochastic models of
cellular processes is often a challenging task. In recent work on models of
gene expression, it was shown that a mapping based on partitioning of Poisson
arrivals (PPA-mapping) can lead to exact solutions for previously unsolved
problems. While the approach can be used in general when the model involves
Poisson processes corresponding to creation or degradation, current
applications of the method and new results derived using it have been limited
to date. In this paper, we present the exact solution of a variation of the
two-stage model of gene expression (with time dependent transition rates)
describing the arbitrary partitioning of proteins. The methodology proposed
makes full use of the the PPA-mapping by transforming the original problem into
a new process describing the evolution of three biological switches. Based on a
succession of transformations, the method leads to a hierarchy of reduced
models. We give an integral expression of the time dependent generating
function as well as explicit results for the mean, variance, and correlation
function. Finally, we discuss how results for time dependent parameters can be
extended to the three-stage model and used to make inferences about models with
parameter fluctuations induced by hidden stochastic variables.Comment: 15 pages, 6 figure
Dynamical phase transition of a 1D transport process including death
Motivated by biological aspects related to fungus growth, we consider the
competition of growth and corrosion. We study a modification of the totally
asymmetric exclusion process, including the probabilities of injection
and death of the last particle . The system presents a phase transition
at , where the average position of the last particle
grows as . For , a non equilibrium stationary state
exists while for the asymptotic state presents a low density
and max current phases. We discuss the scaling of the density and current
profiles for parallel and sequential updates.Comment: 4 pages, 5 figure
PARENT'S ROLE PREVENTING EARLY MARRIAGE
Background: Early marriage has many negative impacts; therefore, parents needed an effort to prevent early marriage. Purpose: To describe the role of parents in preventing early marriage. Method: quantitative descriptive, Accidental sampling technique, with a sample size of 95. The study was conducted in May 2019. The research instrument was a questionnaire on the Role of Parents in Preventing Early Marriage, modified from Novianti (2017), contained 30 questions, with a validity score of 0.3785 and alpha cronbach 0.707. Data analysis using frequency distribution. This research had been registered to the ethics committee with the ethics number of 535/UN6.KEP/EC/2019. Result: 56 people (59%) parents done their role excellent in preventing early marriage. Of the five roles of parents, the role of parents was an educator 64 (67%), role models and friends 46 (48%), counselor 40 (53%), and 60 (63%) as a communicator. Conclusion: the role of parents in preventing early marriage was categorized as either the role of educator, communicator and counselor, while the role of parents as friends and role models was said to be wrong. Suggestion: education about early marriage to the community and adolescents to reduce or minimize early marriage incidence Keywords: Prevention, Early Marriage, Role of Parents
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