Effects of temperature on the relaxation to equilibrium and stationary nonequilibrium states of some Langevin systems

We investigate the effects of temperature on the properties of the time relaxation to equilibrium and nonequilibrium steady states of correlation functions of some Langevin harmonic systems. We consider commonly used dissipative and conservative Langevin dynamics, and show that the time relaxation rate depends on the temperature in the case of thermal reservoirs at different temperatures connected to the system, but it does not happen in the case of relaxation to equilibrium, i.e., if all the heat bath are at the same temperature. Our formalism maps the initial stochastic problem on a noncanonical quantum field theory, and the calculations of the relaxation rates are based on a perturbative analysis. We argue to show the reliability of the perturbative computation.     

Ferroelectric switching behavior of pulsed laser deposited Ba0.8Sr0.2TiO3 thin films

The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited Ba_0.8Sr_0.2TiO₃ thin films has been studied. The structural and morphological analysis revealed that the films had a well crystallized perovskite phase and grain size of about 30–40 nm. A well saturated P–E hysteresis loop was observed with a remnant polarization (P_r) ≈ 4.8 μC/cm² and a coercive field ≈ 100 kV/cm at a frequency of 1 kHz. The P_r has been found to be decreased only 4.3% after passing 8.0 × 10⁸ cycles. The analysis of switching response with nucleation limited switching model reveals that characteristic switching time (t₀) variance is due to the random distribution of the local electric fields. The peak value of polarization current and t₀ exhibits exponential dependence on reciprocal of pulse amplitude.     

Holographic dark energy and the universe expansion acceleration

By incorporating the holographic principle in a time-depending Λ-term cosmology, new physical bounds on the arbitrary parameters of the model can be obtained. Considering then the dark energy as a purely geometric entity, for which no equation of state has to be introduced, it is shown that the resulting range of allowed values for the parameters may explain both the coincidence problem and the universe accelerated expansion, without resorting to any kind of additional structures.     

Production of heavy neutron-rich nuclei “south" of lead

The production of heavy neutron-rich nuclei is investigated using cold-fragmentation reactions. More than 25 new heavy neutron-rich nuclei were produced in the fragmentation of ²⁰⁸Pb projectiles at 1 A GeV impinging a beryllium target. The precise measurement of their production cross sections enables to benchmark the predictive power of different model calculations and make reliable predictions of the production rates expected in future radioactive beam facilities.     

Experimental indications for the response of the spectators to the participant blast

Precise momentum distributions of identified projectile fragments, formed in the reactions 238U+Pb and 238U+Ti at 1A GeV, are measured with a high-resolution magnetic spectrometer. With increasing mass loss, the velocities first decrease as expected from previously established systematics, then level off, and finally increase again. Light fragments are on the average even faster than the projectiles. This finding is interpreted as the response of the spectators to the participant blast. The reacceleration of projectile spectators is sensitive to the nuclear mean field and provides a new tool for investigating the equation of state of nuclear matter.     

Determination of elastic constants of Na0.5Bi0.5TiO3 from ab initio calculations

Elastic constants and bulk modulus for the tetragonal, rhombohedral, and cubic phase of Na_0.5Bi_0.5TiO₃ crystal were calculated from the first principles. From the calculated elastic constants, other structural properties such as bulk modulus, shear modulus, Young's modulus, and Poisson's ratio can be derived using respective relationships from Voight–Reuss–Hill approximation; bulk modulus was calculated as an example in this article. It was shown that elastic constants show different behavior for compression and elongation. The different values of elastic constants have been calculated for the direction parallel to the bismuth layer (crystallographic a(b)-axis) and the perpendicular direction (crystallographic c-axis). It seems to be caused by bismuth layer structure oxides of Na_0.5Bi_0.5TiO₃ crystal.     

Sample Preparation for the Determination of Metals in Food Samples Using Spectroanalytical Methods—A Review

Abstract

The present article gives an overview of recent publications and modern techniques of sample preparation for food analysis employing atomic and inorganic mass spectrometric techniques, such as flame atomic absorption spectrometry, chemical vapor generation atomic absorption and atomic fluorescence spectrometry, graphite furnace atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, and inductively coupled plasma mass spectrometry. Among the most frequently applied sample preparation techniques for food analysis are dry ashing, usually with the addition of an ashing aid, and acid digestion, preferably with the assistance of microwave energy. Slurry preparation, particularly with the assistance of ultrasound, is increasingly used to reduce acid consumption and sample preparation time. Direct analysis of solid samples is gaining importance in the field of food analysis as it offers the highest sensitivity, avoids the use of acids and other aggressive reagents, makes possible the analysis of micro‐samples, and can be applied for fast screening analysis, e.g., of fresh meat.     

Kalorimetrische Messungen an Mischungen von Nichtelektrolyten, 1. Mitt.: Molwärme des Systems 1,2-Dibromäthan-Benzol

Zusammenfassung Es wird der Aufbau eines Kalorimeters zur Bestimmung der spezif. Wärme von Flüssigkeiten beschrieben. Die Messungen werden nach einem kontinuierlichen adiabatischen Aufheizverfahren durchgeführt. Der Fehler in der Molwärme beträgt ca. ±0,4%. Die Methode erlaubt auch innerhalb relativ kleiner Temperaturbereiche eine Aussage über die Temperaturabhängigkeit der Wärmekapazität.Die Molwärme des Systems 1,2-Dibromäthan-Benzol wird zwischen 24 und 29°C über den ganzen Konzentrationsbereich vermessen. Die Mischungen zeigen negative C _p-Werte mit unsymmetrischem Konzentrationsverlauf. Für höhere Temperaturen ist eine Zunahme der Symmetrie zu erwarten.

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A calorimeter has been described which serves to determine the heat capacities of liquids. In the measurements the calorimeter and the surroundings are heated continuously, so that adiabatic conditions prevail. The experimental error in the molar heat capacities is ca. ±0,4%. The method also permits the estimation of the temperature dependence of the heat capacities, even within relatively small temperature intervals.The molar heat capacity of the system 1,2-dibromoethane-benzene has been measured between 24° and 29°C for all concentrations. The C _p-values of the mixtures are negative and show an asymmetrical dependence on the concentration. For higher temperatures it is expected that the concentration dependence will become more nearly symmetrical.

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