6,474 research outputs found
Thermodynamics and Phase Structure of the Two-Flavor Nambu--Jona-Lasinio Model Beyond Large-N_c
The optimized perturbation theory (OPT) method is applied to the
version of the Nambu--Jona-Lasinio (NJL) model both at zero and at finite
temperature and/or density. At the first nontrivial order the OPT exhibits a
class of 1/N_c corrections which produce nonperturbative results that go beyond
the standard large-N_c, or mean-field approximation. The consistency of the OPT
method with the Goldstone theorem at this order is established, and appropriate
OPT values of the basic NJL (vacuum) parameters are obtained by matching the
pion mass and decay constant consistently. Deviations from standard large-N_c
relations induced by OPT at this order are derived, for example, for the
Gell--Mann-Oakes-Renner relation. Next, the results for the critical quantities
and the phase diagram of the model, as well as a number of other
thermodynamical quantities of interest, are obtained with OPT and then
contrasted with the corresponding results at large N_c.Comment: 29 pages, 20 figures, revtex. Minor corrections. In press Phys. Rev.
StdpC: a modern dynamic clamp
With the advancement of computer technology many novel uses of dynamic clamp have become possible. We have added new features to our dynamic clamp software StdpC (âSpike timing-dependent plasticity Clampâ) allowing such new applications while conserving the ease of use and installation of the popular earlier Dynclamp 2/4 package. Here, we introduce the new features of a waveform generator, freely programmable HodgkinâHuxley conductances, learning synapses, graphic data displays, and a powerful scripting mechanism and discuss examples of experiments using these features. In the first example we built and âvoltage clampedâ a conductance based model cell from a passive resistorâcapacitor (RC) circuit using the dynamic clamp software to generate the voltage-dependent currents. In the second example we coupled our new spike generator through a burst detection/burst generation mechanism in a phase-dependent way to a neuron in a central pattern generator and dissected the subtle interaction between neurons, which seems to implement an information transfer through intraburst spike patterns. In the third example, making use of the new plasticity mechanism for simulated synapses, we analyzed the effect of spike timing-dependent plasticity (STDP) on synchronization revealing considerable enhancement of the entrainment of a post-synaptic neuron by a periodic spike train. These examples illustrate that with modern dynamic clamp software like StdpC, the dynamic clamp has developed beyond the mere introduction of artificial synapses or ionic conductances into neurons to a universal research tool, which might well become a standard instrument of modern electrophysiology
Critical and Tricritical Points for the Massless 2d Gross-Neveu Model Beyond Large N
Using optimized perturbation theory, we evaluate the effective potential for
the massless two dimensional Gross-Neveu model at finite temperature and
density containing corrections beyond the leading large-N contribution. For
large-N, our results exactly reproduce the well known 1/N leading order results
for the critical temperature, chemical potential and tricritical points. For
finite N, our critical values are smaller than the ones predicted by the
large-N approximation and seem to observe Landau's theorem for phase
transitions in one space dimension. New analytical results are presented for
the tricritical points that include 1/N corrections. The easiness with which
the calculations and renormalization are carried out allied to the seemingly
convergent optimized results displayed, in this particular application, show
the robustness of this method and allows us to obtain neat analytical
expressions for the critical as well as tricritical values beyond the results
currently known.Comment: 29 pages, 14 figure
Effective Potential and Thermodynamics for a Coupled Two-Field Bose Gas Model
We study the thermodynamics of a two-species homogeneous and dilute Bose gas
that is self-interacting and quadratically coupled to each other. We make use
of field theoretical functional integral techniques and evaluate the one-loop
finite temperature effective potential for this system considering the
resummation of the leading order temperature dependent as well as infrared
contributions. The symmetry breaking pattern associated to the model is then
studied by considering different values of self and inter-species couplings. We
pay special attention to the eventual appearance of reentrant phases and/or
shifts in the observed critical temperatures as compared to the monoatomic
(one-field Bose) case.Comment: 21 pages, 4 eps figure
A new improved optimization of perturbation theory: applications to the oscillator energy levels and Bose-Einstein critical temperature
Improving perturbation theory via a variational optimization has generally
produced in higher orders an embarrassingly large set of solutions, most of
them unphysical (complex). We introduce an extension of the optimized
perturbation method which leads to a drastic reduction of the number of
acceptable solutions. The properties of this new method are studied and it is
then applied to the calculation of relevant quantities in different
models, such as the anharmonic oscillator energy levels and the critical
Bose-Einstein Condensation temperature shift recently investigated
by various authors. Our present estimates of , incorporating the
most recently available six and seven loop perturbative information, are in
excellent agreement with all the available lattice numerical simulations. This
represents a very substantial improvement over previous treatments.Comment: 9 pages, no figures. v2: minor wording changes in title/abstract, to
appear in Phys.Rev.
Complete genome sequence of burkholderia gladioli myophage mana
Burkholderia gladioli is known to cause respiratory tract infections in cystic fibrosis patients. Here, we describe the annotation of the 38,038-bp genome sequence of Mana, a P2-like phage of B. gladioli. Understanding the genomic characteristics of phages infecting pathogens like B. gladioli can lead to advancements in phage therapy.Fil: Godoy, Brenda. Texas A&M University; Estados UnidosFil: Yao, Guichun. Texas A&M University; Estados UnidosFil: Le, Tram. Texas A&M University; Estados UnidosFil: Vizoso Pinto, MarĂa Guadalupe. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - TucumĂĄn. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de TucumĂĄn. Instituto Superior de Investigaciones BiolĂłgicas; ArgentinaFil: Gill, Jason. Texas A&M University; Estados UnidosFil: Gonzalez, Carlos. Texas A&M University; Estados UnidosFil: Liu, Mei. Texas A&M University; Estados Unido
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Repurposing Albendazole: new potential as a chemotherapeutic agent with preferential activity against HPV-negative head and neck squamous cell cancer.
Albendazole is an anti-helminthic drug that has been shown to exhibit anti-cancer properties, however its activity in head and neck squamous cell cancer (HNSCC) was unknown. Using a series of in vitro assays, we assessed the ability of albendazole to inhibit proliferation in 20 HNSCC cell lines across a range of albendazole doses (1 nM-10 ÎŒM). Cell lines that responded to treatment were further examined for cell death, inhibition of migration and cell cycle arrest. Thirteen of fourteen human papillomavirus-negative HNSCC cell lines responded to albendazole, with an average IC50 of 152 nM. In contrast, only 3 of 6 human papillomavirus-positive HNSCC cell lines responded. Albendazole treatment resulted in apoptosis, inhibition of cell migration, cell cycle arrest in the G2/M phase and altered tubulin distribution. Normal control cells were not measurably affected by any dose tested. This study indicates that albendazole acts to inhibit the proliferation of human papillomavirus-negative HNSCC cell lines and thus warrants further study as a potential chemotherapeutic agent for patients suffering from head and neck cancer
Complete genome sequence of burkholderia cenocepacia phage mica
Burkholderia cenocepacia is a multidrug-resistant Gram-negative pathogen known to colonize patients with chronic granulomatous disease and cystic fibrosis. Here, we describe Burkholderia phage Mica, which is predicted to be a lysogenic myophage based on the similarity of its structural proteins to Enterobacteria phage P2 and Burkholderia phage KL3.Fil: Garcia, James. Texas A&M University; Estados UnidosFil: Yao, Guichun. Texas A&M University; Estados UnidosFil: Vizoso Pinto, MarĂa Guadalupe. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - TucumĂĄn. Instituto Superior de Investigaciones BiolĂłgicas. Universidad Nacional de TucumĂĄn. Instituto Superior de Investigaciones BiolĂłgicas; ArgentinaFil: Clark, James. Texas A&M University; Estados UnidosFil: Le, Tram. Texas A&M University; Estados UnidosFil: Gonzalez, Carlos. Texas A&M University; Estados UnidosFil: Gill, Jason. Texas A&M University; Estados UnidosFil: Liu, Mei. Texas A&M University; Estados Unido
A new method for the solution of the Schrodinger equation
We present a new method for the solution of the Schrodinger equation
applicable to problems of non-perturbative nature. The method works by
identifying three different scales in the problem, which then are treated
independently: An asymptotic scale, which depends uniquely on the form of the
potential at large distances; an intermediate scale, still characterized by an
exponential decay of the wave function and, finally, a short distance scale, in
which the wave function is sizable. The key feature of our method is the
introduction of an arbitrary parameter in the last two scales, which is then
used to optimize a perturbative expansion in a suitable parameter. We apply the
method to the quantum anharmonic oscillator and find excellent results.Comment: 4 pages, 4 figures, RevTex
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