On a conjecture about Dirac's delta representation using q-exponentials

A new representation of Dirac's delta-distribution, based on the so-called q-exponentials, has been recently conjectured. We prove here that this conjecture is indeed valid

Optical Bistability in Nonlinear Optical Coupler with Negative Index Channel

We discuss a novel kind of nonlinear coupler with one channel filled with a negative index material (NIM). The opposite directionality of the phase velocity and the energy flow in the NIM channel facilitates an effective feedback mechanism that leads to optical bistability and gap soliton formation

In vitro tests of suitability of bacteriocin-producing lactic acid bacteria, as potential biopreservation cultures in vacuum-packaged cold-smoked salmon

The objectives of this study were to ascertain the in vitro potential of nine bacteriocin-producing lactic acid bacteria (LAB) strains, isolated from vacuum-packaged cold-smoked salmon (CSS), for possible use as biopreservative cultures against Listeria monocytogenes. The antilisterial activity of cultures’ supernatants was assessed at 0.5%, 3.0% and 5.0% w/v of salt, at 5ºC, 10ºC and 25ºC both in aerobic and anaerobic atmospheres, simulating the conditions pertaining in vacuum-packaged CSS. The kinetics of growth, bacteriocin biosynthesis, the minimum inhibitory concentrations (MICs) of ten antibiotics, histamine and tyramine production of LAB strains, were determined jointly with the haemolytic activity for the enterococci. Only five strains were able to secrete active bacteriocins into the culture medium, at high salt concentrations and low temperatures, both in aerobic and anaerobic atmospheres. Enterococci showed neither haemolyt ic activity nor vancomycin resistance. The production of histamine was not observed for any of the bacteriocin-producing strains

Geometrothermodynamics

We present the fundamentals of geometrothermodynamics, an approach to study the properties of thermodynamic systems in terms of differential geometric concepts. It is based, on the one hand, upon the well-known contact structure of the thermodynamic phase space and, on the other hand, on the metric structure of the space of thermodynamic equilibrium states. In order to make these two structures compatible we introduce a Legendre invariant set of metrics in the phase space, and demand that their pullback generates metrics on the space of equilibrium states. We show that Weinhold's metric, which was introduced {\it ad hoc}, is not contained within this invariant set. We propose alternative metrics which allow us to redefine the concept of thermodynamic length in an invariant manner and to study phase transitions in terms of curvature singularities.Comment: Revised version, to be published in Jour. Math. Phy

The Physical Origins of Entropy Production, Free Energy Dissipation and their Mathematical Representations

A complete mathematical theory of nonequilibrium thermodynamics of stochastic systems in terms of master equations is presented. As generalizations of isothermal entropy and free energy, two functions of states play central roles: the Gibbs entropy $S$ and the relative entropy $F$, which are related via the stationary distribution of the stochastic dynamics. $S$ satisfies the fundamental entropy balance equation $dS/dt=e_p-h_d/T$ with entropy production rate $e_p\ge 0$ and heat dissipation rate $h_d$, while $dF/dt=-f_d\le 0$. For closed systems that satisfy detailed balance: $Te_p(t)=f_d(t)$. For open system one has $Te_p(t)=f_d(t)+Q_{hk}(t)$ where the housekeeping heat $Q_{hk}\ge 0$ was first introduced in the phenomenological nonequilibrium steady state thermodynamics. Entropy production $e_p$ consists of free energy dissipation associated with spontaneous relaxation, $f_d$, and active energy pumping that sustains the open system $Q_{hk}$. The amount of excess heat involved in the relaxation $Q_{ex}=h_d-Q_{hk} = f_d-T(dS/dt)$.Comment: 4 pages, no figure

Charge Symmetry Violation Effects in Pion Scattering off the Deuteron

We discuss the theoretical and experimental situations for charge symmetry violation (CSV) effects in the elastic scattering of pi+ and pi- on deuterium (D) and 3He/3H. Accurate comparison of data for both types of targets provides evidence for the presence of CSV effects. While there are indications of a CSV effect in deuterium, it is much more pronounced in the case of 3He/3H. We provide a description of the CSV effect on the deuteron in terms of single- and double- scattering amplitudes. The Delta-mass splitting is taken into account. Theoretical predictions are compared with existing experimental data for pi-d scattering; a future article will speak to the pi-three nucleon case.Comment: 16 pages of RevTeX, 7 postscript figure

emPHasis-10: development of a health-related quality of life measure in pulmonary hypertension.

The aim of this study was to develop a measure of the impact of pulmonary hypertension (PH) on health-related quality of life (HRQoL) as there is a need for a short, validated instrument that can be used in routine clinical practice. Interviews were conducted with 30 PH patients to derive 32 statements, which were presented as a semantic differential six-point scale (0–5), with contrasting adjectives at each end. This item list was completed by patients attending PH clinics across the UK and Ireland. Rasch analysis was applied to identify items fitting a uni-dimensional model. 226 patients (mean age 55.6±14 years; 70% female) with PH (82% had pulmonary arterial hypertension) completed the study questionnaires. 10 of the 32 items demonstrated fit to the Rasch model (Chi-squared 16; p>0.05) and generated the emPHasis-10 questionnaire. Test–retest (intraclass correlation coefficient 0.95, n=33) and internal consistency (Chronbach’s α=0.9) were strong. emPHasis-10 scores correlated consistently with other relevant measures and discriminated subgroups of patients stratified by World Health Organization functional class (ANOVA F=1.73; p<0.001). The emPHasis-10 is a short questionnaire for assessing HRQoL in pulmonary arterial hypertension. It has excellent measurement properties and is sensitive to differences in relevant clinical parameters. It is freely available for clinical and academic use

Simulation of fluid-solid coexistence in finite volumes: A method to study the properties of wall-attached crystalline nuclei

The Asakura-Oosawa model for colloid-polymer mixtures is studied by Monte Carlo simulations at densities inside the two-phase coexistence region of fluid and solid. Choosing a geometry where the system is confined between two flat walls, and a wall-colloid potential that leads to incomplete wetting of the crystal at the wall, conditions can be created where a single nanoscopic wall-attached crystalline cluster coexists with fluid in the remainder of the simulation box. Following related ideas that have been useful to study heterogeneous nucleation of liquid droplets at the vapor-liquid coexistence, we estimate the contact angles from observations of the crystalline clusters in thermal equilibrium. We find fair agreement with a prediction based on Young's equation, using estimates of interface and wall tension from the study of flat surfaces. It is shown that the pressure versus density curve of the finite system exhibits a loop, but the pressure maximum signifies the "droplet evaporation-condensation" transition and thus has nothing in common with a van der Waals-like loop. Preparing systems where the packing fraction is deep inside the two-phase coexistence region, the system spontaneously forms a "slab state", with two wall-attached crystalline domains separated by (flat) interfaces from liquid in full equilibrium with the crystal in between; analysis of such states allows a precise estimation of the bulk equilibrium properties at phase coexistence