Improved Quantum Hard-Sphere Ground-State Equations of State

The London ground-state energy formula as a function of number density for a system of identical boson hard spheres, corrected for the reduced mass of a pair of particles in a sphere-of-influence picture, and generalized to fermion hard-sphere systems with two and four intrinsic degrees of freedom, has a double-pole at the ultimate \textit{regular} (or periodic, e.g., face-centered-cubic) close-packing density usually associated with a crystalline branch. Improved fluid branches are contructed based upon exact, field-theoretic perturbation-theory low-density expansions for many-boson and many-fermion systems, appropriately extrapolated to intermediate densities, but whose ultimate density is irregular or \textit{random} closest close-packing as suggested in studies of a classical system of hard spheres. Results show substantially improved agreement with the best available Green-function Monte Carlo and diffusion Monte Carlo simulations for bosons, as well as with ladder, variational Fermi hypernetted chain, and so-called L-expansion data for two-component fermions.Comment: 15 pages and 7 figure

Mechanisms driving alteration of the Landau state in the vicinity of a second-order phase transition

The rearrangement of the Fermi surface of a homogeneous Fermi system upon approach to a second-order phase transition is studied at zero temperature. The analysis begins with an investigation of solutions of the equation $\epsilon(p)=\mu$, a condition that ordinarily has the Fermi momentum $p_F$ as a single root. The emergence of a bifurcation point in this equation is found to trigger a qualitative alteration of the Landau state, well before the collapse of the collective degree of freedom that is responsible for the second-order transition. The competition between mechanisms that drive rearrangement of the Landau quasiparticle distribution is explored, taking into account the feedback of the rearrangement on the spectrum of critical fluctuations. It is demonstrated that the transformation of the Landau state to a new ground state may be viewed as a first-order phase transition.Comment: 16 pages, 10 figure

Actin- and myosin-dependent vesicle loading of presynaptic docking sites prior to exocytosis.

Variance analysis of postsynaptic current amplitudes suggests the presence of distinct docking sites (also called release sites) where vesicles pause before exocytosis. Docked vesicles participate in the readily releasable pool (RRP), but the relation between docking site number and RRP size remains unclear. It is also unclear whether all vesicles of the RRP are equally release competent, and what cellular mechanisms underlie RRP renewal. We address here these questions at single glutamatergic synapses, counting released vesicles using deconvolution. We find a remarkably low variance of cumulative vesicle counts during action potential trains. This, combined with Monte Carlo simulations, indicates that vesicles transit through two successive states before exocytosis, so that the RRP is up to 2-fold higher than the docking site number. The transition to the second state has a very rapid rate constant, and is specifically inhibited by latrunculin B and blebbistatin, suggesting the involvement of actin and myosin

Ground state instability in systems of strongly interacting fermions

We analyze stability of a fermion system with model repulsive pair interaction potential. The possibility for different types of restructuring of the Fermi ground state (at sufficiently great coupling constant) is related to the analytic properties of such potential. In particular, for the screened Coulomb law it is shown that the restructuring cannot be of the Fermi condensation type, known earlier for some exactly solvable models, and instead it belongs to the class of topological transitions (TT). For this model, a phase diagram has been built in the variables "screening parameter - coupling constant" which displays two kinds of TT: a 5/2-kind similar to the known Lifshitz transitions in metals, and a 2-kind characteristic for a uniform strongly interacting system.Comment: The article has 11 pages, in Latex 2e (from Lyx), 3 eps figures or a ps fil

Origen de las arterias testiculares en caninos

Ante las discrepancias existentes entre distintos autores de difundidos textos de anatomía animal, el propósito del trabajo fue investigar eventuales diferencias en el origen de las arterias testiculares del perro. Se emplearon 15 cadáveres de caninos de diferente raza, edad y talla. Tras ser inyectados con pasta de repleción (látex coloreado), se les practicaron las disecciones correspondientes. Los resultados obtenidos indicaron que en el 80% de los casos la arteria testicular derecha se originaba de la aorta abdominal, cranealmente con respecto a la arteria testicular izquierda. En el 20% restante se comprobó que ambas lo hacían a la misma altura. Además de enriquecer los conocimientos anatómicos acerca del patrón de irrigación testicular, el hallazgo es aplicable en las técnicas quirúrgicas que involucren la topografía regional estudiada

Is asthma control more than just an absence of symptoms? An expert consensus statement

Purpose: Definitions and measures of asthma control used in clinical trials and in clinical practice vary considerably. There is also misalignment between patients and healthcare professionals (HCPs) in terms of understanding and managing asthma control. This study aimed to progress towards a consensus definition of asthma control, and evaluate disparities between HCP and patient perspectives. Basic procedures: A two-stage Delphi questionnaire involving asthma specialists sought to identify areas of consensus on aspects of asthma control in clinical practice. Results were compared with those of a structured literature review to assess if existing guidance and measures of asthma control used in studies correlated with practice. Eighty-two panelists took part in the Delphi questionnaire. The structured literature review included 185 manuscripts and 31 abstracts. Main findings: Panelists agreed that there was no standard definition of asthma control, confirmed by a total of 19 different composite consensus/guideline definitions and/or validated measures of control being identified across the Delphi study and literature review. Panelists agreed on the positive associations of well-controlled asthma with patient outcomes, but not on the components or thresholds of a working definition of control. Principal conclusions: A universally accepted definition and measure of asthma control that is utilized and understood by patients, HCPs, and researchers is required

Phase diagram of the Heisenberg antiferromagnet with four-spin interactions

We study the quantum phase diagram of the Heisenberg planar antiferromagnet with a subset of four-spin ring exchange interactions, using the recently proposed heirarchical mean-field approach. By identifying relevant degrees of freedom, we are able to use a single variational anzatz to map the entire phase diagram of the model and uncover the nature of its various phases. It is shown that there exists a transition between a N\'eel state and a quantum paramagnetic phase, characterized by broken translational invariance. The non-magnetic phase preserves the lattice rotational symmetry, and has a correlated plaquette nature. Our results also suggest that this phase transition can be properly described within the Landau paradigm.Comment: LaTeX 2e, 7 pages, 8 figure

Conformación fascicular de los nervios tibial y peroneo común en el perro

El objetivo del trabajo fue identificar el número y situación espacial de los fascículos que conforman los nervios tibial y peroneo común en el perro, permitiendo de esta manera su clasificación acorde a modelos de agrupación fascicular. Se trabajó con 20 miembros posteriores de caninos. Los nervios tibial y peroneo común fueron disecados. A partir de cortes transversales de dichos nervios se realizaron preparados histológicos coloreados con hematoxilina y eosina, determinándose por microscopía óptica el número y la distribución de los fascículos, agrupándose las fibras en tres categorías acorde a su diámetro (hasta 4, de 4 a 8 y de 8 a 12 mm). Para el nervio tibial fueron identificados trece fascículos, el de mayor diámetro ubicado caudal y medialmente del nervio, resultando que el 40% de sus fibras correspondió a la primera categoría, 52% para la segunda y 8% para la tercera. Para el nervio peroneo común se identificaron tres fascículos, el de mayor diámetro ubicado caudalmente, no diferenciando su posición lateral o medial por tratarse de un nervio aplanado, con una distribución lineal de los fascículos; del análisis de las fibras surgió que el 50% perteneció a la primera categoría, 35% a la segunda y 15% a la tercera

Irrigación y conformación fascicular del nervio femoral en el perro

El objetivo del trabajo fue determinar el origen y distribución segmentaria de los vasos sanguíneos queconstituyen el sistema extrínseco de vascularización e identificar el número y situación delos fascículos que conforman el nervio femoral en el perro. Se trabajó con 20 miembrosposteriores de caninos, inyectados con látex coloreado, en los cuales se disecó el nervioy se identificó su irrigación. A partir de cortes transversales del tronco nervioso se realizaronpreparados histológicos coloreados con hematoxilina y eosina, determinándose pormicroscopía óptica el número y la distribución de los fascículos, agrupándose las fibras entres categorías acorde a su diámetro (hasta 4, de 4 a 8 y de 8 a 12 um). La vascularizacióndel nervio femoral en el perro resultó estar constituida por pequeños vasos que parten de laarteria iliaca circunfleja superficial y arteria femoral circunfleja lateral, ambas colaterales dela arteria femoral. En cuanto a la conformación, se identificaron 3 fascículos y del análisisde sus fibras surgió que el 40% perteneció a la primera categoría, 46% a la segunda y 14% ala tercera. Los resultados de este trabajo asumen utilidad al momento de efectuar maniobrasquirúrgicas y reparadoras en la región medial del muslo en el perro