The partial distribution functions and effective pair potentials of some H-bonded liquids from diffraction data

The partial structures and distribution functions are directly linked to structural model of molecular liquids. The comparative study of partial distribution function of different hydrogen-bonded liquids gives the information that hydrogen-bonding is stronger in alcohols than in water and ammonia. The effective pair potential is directly related to the pair correlation function. The comparative study of such potentials for different hydrogen-bonded liquids gives some characteristic features.     

Partial pair correlation functions of La1−x(AlGaAu)x metallic glasses from x-ray diffraction data

X-ray diffraction studies of La_1?xAl_x, La_1?x(Al_0.5Ga_0.5x, La_1?xGa_x and La_1?xAu_x metallic glasses have been performed for x = 0.20, 0.24 and 0.28. Similarities in the radial distribution functions for these materials as well as other data suggest that these alloys are isostructural. Experimental data from different alloys have therefore been used to separate the three different pair distribution functions, which are then compared to dense random packing models and data for other metallic glasses.     

New pair potentials from an improved born-green integral equation: Application to liquid metals

With an improvement of the superposition approximation in the Born-Green integral equation recently proposed an attempt is made to extract new effective pair potentials from structure factors of simple liquids. The improvement is obtained by taking the first three terms of a hard-core density expansion of the triplet correlation function. The method of calculation is based on the solution of the integral equation in k-space. It is shown that the resulting potential of the improved Born-Green equation from a hard-core structure factor actually is hard-core like contrary to the Born-Green result. From measured structure factors of some simple liquid metals (Na-100°C, Al-670°C and Ni-1600°C) pair potentials are determined. With this application a significant improvement over the Born-Green theory can be achieved. In comparison to the old discrepancy between the Born-Green equation and theoretical models the results agree very well with theoretical calculations in the repulsive range of the potential.     

The Laplace transform of the MSA pair distribution functions between macroions in an ion-dipole fluid

The Laplace transform is obtained for the pair distribution function between a pair of ions, an ion and a macroion, and a pair of macroions in an ion-dipole fluid. This fluid is a simplified model of an electrolyte with a discrete model of solvent (hard spheres with embedded point dipoles). From these results, an expression for the solvation force between macroions is obtained. This result consists of the classical DLVO result plus a series of corrections.     

Determination of an energy distribution from stopping potential data

The energy spectrum of electrons just inside an irradiated surface is obtained in terms of the derivatives of the current—voltage curve for electrons emitted from the surface. For the familiar case of a unidirectional beam, the energy distribution is just the negative of the first derivative. For an (assumed) isotropic distribution inside the surface, a classical surface potential, and a spherically symmetric retarding field, the energy distribution is similar to the unidirectional case except that the first derivative must be multiplied by an energy-dependent factor. If the retarding field is uniform and perpendicular to the surface, the calculation of the energy distribution inside involves both the first and second derivatives.     

Zweidimensionale Datenreduktion von Wellenflächen und Punktbildern: Two-dimensional data reduction of wavefronts and point-spread functions

Die analytische Untersuchung realer optischer Systeme erfordert die Datenreduktion ihrer gemessenen Wellenflächen oder Punktbilder. Es wird eine nicht iterative Anpassung vorgestellt, die ohne vorherige Glättung alle Bildpunkte berücksichtigt und keine a priori Informationen voraussetzt. Beispiele werden präsentiert.Analysis of real optical systems require data reduction of their measured wavefronts or point-spread functions. A non-iterative fitting procedure is presented, which takes all pixels into account without prior smoothing. The fitting procedure needs no a priori information. Examples are shown.     

Generalized distribution functions and an alternative approach to generalized Planck radiation law

In this study, recently introduced generalized distribution functions are summarized and by using one of these distribution functions, namely generalized Planck distribution, an alternative approach to the generalized Planck law for the blackbody radiation has been tackled. The expression obtained is compared with the expression given by C. Tsallis et al. [Phys. Rev. E 52 (1995) 1447], and it is found that this approximate scheme provides bounds to the exact result, depending on the values of q-index.     

Complementary control by additives of the kinetics of amorphous CaCO3 mineralization at an organic interface: in-situ synchrotron x-ray observations

The kinetics of biomimetic mineralization at a fatty acid monolayer interface have been measured in situ by synchrotron x-ray reflectivity. The formation of biologically relevant amorphous calcium carbonate films is affected by soluble macromolecules, supersaturation rate of change, and Mg cations. We find that these solution conditions influence mineral film formation in a complementary fashion. Poly(sodium acrylate) extends the lifetime of metastable amorphous calcium carbonate, solution saturation controls the mineral film growth rate, and Mg cations create a longer induction time. This is the first quantification of potentially competitive biomineralization mechanisms that addresses nucleation and growth of the amorphous mineral phases, which are important in biomineralization.     

Lennard-Jones chain mixtures: radial distribution functions from Monte Carlo simulation

Radial distribution functions are calculated for binary Lennard-Jones chain mixtures from Monte Carlo simulation. Average and end-to-end inter- and intrachain radial distribution functions are calculated, ten for a binary mixture and four for a pure component. The effects of density, concentration, temperature, chain length, Lennard-Jones size and energy parameters are investigated. It is found that intrachain radial distribution functions are largely independent of density except at very high densities, where they start to take on a structure tending towards that of a crystal lattice. In addition, the effect of using different distribution functions to calculate the associating contribution in statistical associating fluid theory (SAFT) is examined. Further, the effect of using short chain fluids rather than the monomer unit as the reference system in the calculation of the pressure and free energy of chain fluids in first-order thermodynamic perturbation theory (TPT) is examined. It is found that the choice of reference radial distribution function has a marked effect on the calculation of thermodynamic properties through the use of SAFT and TPT.     

Comments on an empirical scaling rule related to x-ray emission from superheavy quasimolecules

A scaling rule related to maximum contributing impact parameters for inner shell Coulomb ionization probabilities is studied by an adiabatic perturbation approach. Qualitative arguments are given for an extended validity of the scaling law to very heavy collision systems.     

On the fitness of an algebraic distribution curve to experimental diffusion data

Summary The “witch of Agnesi” is proposed as analytical distribution alternative to the Gaussian one in atmospheric-diffusion estimates. The Agnesi distribution can be derived from the “K theory? and leads finally to algebraic formulae without exponentials, so more easily treated either by hand or by a computer than a Gaussian. Comparing both the Agnesi and the Gaussian distribution with the data set from the EPRI diffusion experiment (plains site), both distribution show a poor fit of the experimental data, slightly better for the Agnesi distribution when literature values for σ _y and σ _z are used.

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Riassunto Viene proposta la ?versiera di Agnesi? come distribuzione alternativa alla Gaussiana in calcoli di diffusione atmosferica. La distribuzione di Agnesi può essere derivata dalla ?K theory? e porta in definitiva a formule algebriche senza esponenziali, piú facilmente trattabili sia in calcoli a mano che con il computer. Confrontando le due distribuzioni Agnesi e Gaussiana con i dati della campagna sperimentale EPRI di Kincaid esse dimostrano entrambe una scarsa adattabilità ai dati sperimentali che tuttavia è tendenzialmente migliore per la Agnesi quando la deviazione standard sperimentale è sostituita da valori di letteratura di σ _y e σ _z comunemente impiegati.

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Резюме Предлагается ?локон Анвези? как анаалитическое алвтернативное распределение распределению Гаусса при описании атмосферной диффузии. Распеделение Анвези может бытв получено из ⩉К теории? и приводит к алгебраической формуле без экспонент, что является более удобным при ручых или компвютерных вычисленииях, чем распределение Гаусса. Проводится сравнение распеделения Анвези и распределения Гаусса с системой данных из EPRI диффузионного эксперимента. Оба рапеделения плохо соответствуют эксперименталвным данным, однако рас↪ределение Анвези дает иесколвко лучшее соответствие, ктгда исполвзуются литературные значения для σ _y и σ _z .

     

Features of the moment functions of an oscillator with parametric instability due to dichotomous noise with Erlang distribution functions

We study stability of the periodic solutions of a linear undamped oscillator with frequency modulated by dichotomous noise whose statistic is determined by the Erlang distribution. It is shown that the amplitudes of harmonic oscillations of such an oscillator increase with time at different rates determined by the ratio of the oscillator eigenfrequency to the characteristic frequency of dichotomous noise. To solve the problem, we use a finite system of closed equations with respect to the moment functions, which was obtained without assumption on the quasi-Gaussianity and delta-correlatedness of the studied process.     

Contributions from higher twist effects to the quark fragmentation functions in neutrino data

Quark fragmentation functions are studied with ≈3500 charged current events induced in the bubble chamber Gargamelle by neutrinos of the SPS wide band beam, with 〈E_ν〉 ≈ 25 GeV. The Q² and W² regions covered by this experiment are Q² ≈ 0–40 GeV² and W² ≈ 1–100 GeV², the mean values being 〈Q²〉 = 6.5 GeV², 〈W²〉 = 22GeV². A correlation between the variables $\text{z =}\text{E}{}_{\mathrm{\pi }}\text{E}{}_{\mathrm{<mtext>H</mtext>}}$ and $\text{y =}\text{E}{}_{\mathrm{<mtext>H</mtext>}}\text{E}{}_{\mathrm{v}}$ is found in the data in the region Q² = 1–10 GeV², which can be explained in terms of higher twist effects. These effects reproduce the Q² evolution of the non-singlet moments of the fragmentation function without any need for logarithmic terms.     

Pb distribution in bones from the Franklin expedition: synchrotron X-ray fluorescence and laser ablation/mass spectroscopy

Synchrotron micro-X-ray Fluorescence has been used to map the metal distribution in selected bone fragments representative of remains associated with the Franklin expedition. In addition, laser ablation mass spectroscopy using a 25 μm diameter circular spot was employed to compare the Pb isotope distributions in small regions within the bone fragments. The X-ray Fluorescence mapping shows Pb to be widely distributed in the bone while the Pb isotope ratios obtained by laser ablation within small areas representative of bone with different Pb exchange rates do not show statistically significant differences. These results are inconsistent with the hypothesis that faulty solder seals in tinned meat were the principle source of Pb in the remains of the expedition personnel.