Contact values of the radial distribution functions of additive hard-sphere mixtures in d dimensions: A new proposal

The contact values $g_{ij}(\sigma_{ij})$ of the radial distribution functions of a $d$-dimensional mixture of (additive) hard spheres are considered. A `universality' assumption is put forward, according to which $g_{ij}(\sigma_{ij})=G(\eta, z_{ij})$, where $G$ is a common function for all the mixtures of the same dimensionality, regardless of the number of components, $\eta$ is the packing fraction of the mixture, and $z_{ij}$ is a dimensionless parameter that depends on the size distribution and the diameters of spheres $i$ and $j$. For $d=3$, this universality assumption holds for the contact values of the Percus--Yevick approximation, the Scaled Particle Theory, and, consequently, the Boublik--Grundke--Henderson--Lee--Levesque approximation. Known exact consistency conditions are used to express $G(\eta,0)$, $G(\eta,1)$, and $G(\eta,2)$ in terms of the radial distribution at contact of the one-component system. Two specific proposals consistent with the above conditions (a quadratic form and a rational form) are made for the $z$-dependence of $G(\eta,z)$. For one-dimensional systems, the proposals for the contact values reduce to the exact result. Good agreement between the predictions of the proposals and available numerical results is found for $d=2$, 3, 4, and 5.Comment: 10 pages, 11 figures; Figure 1 changed; Figure 5 is new; New references added; accepted for publication in J. Chem. Phy

Universal geometrical scaling of the elliptic flow

The presence of scaling variables in experimental observables provide very valuable indications of the dynamics underlying a given physical process. In the last years, the search for geometric scaling, that is the presence of a scaling variable which encodes all geometrical information of the collision as well as other external quantities as the total energy, has been very active. This is motivated, in part, for being one of the genuine predictions of the Color Glass Condensate formalism for saturation of partonic densities. Here we extend these previous findings to the case of experimental data on elliptic flow. We find an excellent scaling for all centralities and energies, from RHIC to LHC, with a simple generalization of the scaling previously found for other observables and systems. Interestingly the case of the photons, difficult to reconcile in most formalisms, nicely fit the scaling curve. We discuss the possible interpretations of this finding in terms of initial or final state effects.Comment: 6 pages, 4 figures, accepted for publication in Phys Rev

Multicomponent fluids of hard hyperspheres in odd dimensions

Mixtures of hard hyperspheres in odd space dimensionalities are studied with an analytical approximation method. This technique is based on the so-called Rational Function Approximation and provides a procedure for evaluating equations of state, structure factors, radial distribution functions, and direct correlations functions of additive mixtures of hard hyperspheres with any number of components and in arbitrary odd-dimension space. The method gives the exact solution of the Ornstein--Zernike equation coupled with the Percus--Yevick closure, thus extending to arbitrary odd dimension the solution for hard-sphere mixtures [J. L. Lebowitz, Phys.\ Rev.\ \textbf{133}, 895 (1964)]. Explicit evaluations for binary mixtures in five dimensions are performed. The results are compared with computer simulations and a good agreement is found.Comment: 16 pages, 8 figures; v2: slight change of notatio

Fourth virial coefficients of asymmetric nonadditive hard-disc mixtures

The fourth virial coefficient of asymmetric nonadditive binary mixtures of hard disks is computed with a standard Monte Carlo method. Wide ranges of size ratio ($0.05\leq q\leq 0.95$) and nonadditivity ($-0.5\leq \Delta\leq 0.5$) are covered. A comparison is made between the numerical results and those that follow from some theoretical developments. The possible use of these data in the derivation of new equations of state for these mixtures is illustrated by considering a rescaled virial expansion truncated to fourth order. The numerical results obtained using this equation of state are compared with Monte Carlo simulation data in the case of a size ratio $q=0.7$ and two nonadditivities $\Delta=\pm 0.2$.Comment: 9 pages, 7 figures; v2: section on equation of state added; tables moved to supplementary material (http://jcp.aip.org/resource/1/jcpsa6/v136/i18/p184505_s1#artObjSF

A branch-point approximant for the equation of state of hard spheres

Using the first seven known virial coefficients and forcing it to possess two branch-point singularities, a new equation of state for the hard-sphere fluid is proposed. This equation of state predicts accurate values of the higher virial coefficients, a radius of convergence smaller than the close-packing value, and it is as accurate as the rescaled virial expansion and better than the Pad\'e [3/3] equations of state. Consequences regarding the convergence properties of the virial series and the use of similar equations of state for hard-core fluids in $d$ dimensions are also pointed out.Comment: 6 pages, 4 tables, 3 figures; v2: enlarged version, extension to other dimensionalities; v3: typos in references correcte

More on the credit channel of monetary policy transmission: an international comparison

En este trabajo presentamos algunos indicios del funcionamiento del canal del crédito como una forma posible de transmisión de las medidas de política monetaria. El tema se aborda desde una perspectiva internacional, en la que se compara la reacción ante los cambios en la política monetaria de las empresas no financieras de doce países de la OCDE. Haciendo uso del tipo de interés como un indicador del estado de la política monetaria, encontramos que dicho tipo de interés afecta a las decisiones de inversión de las empresas a través de la disponibilidad de crédito bancario, especialmente en el corto plazo. Estos resultados parecen evidenciar una distinta efectividad de la política monetaria en función de las características del sistema financiero de cada país, de modo que en los países con una mayor orientación hacia el mercado, en los cuales la financiación bancaria reviste menor importancia, las decisiones empresariales no se ven tan modificadas como en los países de mayor orientación hacia la intermediación financiera.In this paper we provide some evidence of the credit channel as a possible way of transmitting monetary policy decisions. We do it in an international framework by comparing the reaction of non-financial companies of twelve OECD countries to changes in monetary policy. Using the interest rate as an indicator of the stance of monetary policy, we find that the interest rate does affect firms’ investment and output by altering their bank finance availability, specially the short-term finance. Our results also seem to show a rather different effectiveness of the monetary policy depending on the features of the financial system of each country. In those countries with a more market-oriented financial system, corporate finance relies less heavily on banks, so they are not so influenced by shifts in monetary policy as companies of other more bank-based countrie

Поверхностные скорости и айсберговый сток ледникового купола Академии Наук на Северной Земле

We have determined the ice-surface velocities of the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian Arctic, during the period November 2016 – November 2017, using intensity offset-tracking of Sentinel-1 synthetic-aperture radar images. We used the average of 54 pairs of weekly velocities (with both images in each pair separated by a12-day period) to estimate the mean annual ice discharge from the ice cap. We got an average ice discharge for 2016–2017 of 1,93±0,12 Gt a−1, which is equivalent to −0,35±0,02 m w.e. a−1 over the whole area of the ice cap. The difference from an estimate of ~1,4 Gt a−1 for 2003–2009 can be attributed to the initiation of ice-stream flow in Basin BC sometime between 2002 and 2016. Since the front position changes between both periods have been negligible, ice discharge is equivalent to calving flux. We compare our results for calving flux with those of previous studies and analyse the possible drivers of the changes observed along the last three decades. Since these changes do not appear to have responded to environmental changes, we conclude that the observed changes are likely driven by the intrinsic characteristics of the ice cap governing tidewater glacier dynamics.По 54 парам космических снимков Sentinel‐1, сделанных с ноября 2016 г. по ноябрь 2017 г., определены скорости движения ледникового купола Академии Наук на Северной Земле. На этой основе оценён среднегодовой расход льда в море этого купола (1,93±0,12 Гт/год), установлены основные пути стока льда, проведено сравнение с прежними оценками

Données sur le comportement alimentaire chez Aphaenogaster Senilis Mayr 1853 (Hymenoptera Formicidae)

Es descriu la dieta í la conducta de Aphaenogaster senilis en relació amb la recerca, captura, localització i transport de l'aliment. A. senilis és omnívora, però amb preferència per les restes animals. La localització de l'aliment es fa de manera individual. El transport és individual sí la presa és transportable i única. Si és múltiple í transportable, algunes obreres de l'interior del aiu poden esdevenir transportadores. Es descriu el reclutament, de grup sense líder, i el transport col·lectiu per a preses no transportables i el "tool using" per a dissolucions ensucrades. Es fan algunes consideracions sobre variabilitat individual.The diet and food behaviour of A. Senilis are described. The diet is omnivorous, but animal food is prefered. Ants always search for food individually, and carry them individually when food is transportable and unique. If it is multiple and transportable some ants in the nest can be activated and be carriers too. Group recruitment without der to food occurs when the prey is large. Sugared liquid food is exploi ted by tool using. Variability in feeding behaviour is considered

Genetic Variation and Genotype by Environment Interaction of Crown Rust Resistance in Annual Ryegrass (\u3ci\u3eLolium multiflorum\u3c/i\u3e Lam.)

The genetic variation and genotype by environment interaction of crown rust resistance of annual ryegrass (Lolium multiflorum Lam.) was evaluated at two locations in Argentina, as part of the breeding programme in progress at our Institute. Forty half sib families originated from commercial tetraploid cultivars, were grown from seeds in a greenhouse during autumn 1999. At the stage of tillering initiation forty eight plants/familiy were randomly selected and transplanted as spaced plant trial in a randomized design with three replicates, at the two locations. All plants were scored for a range of morphological and phytopatological attributes. The severity of crown rust and the winter dry matter production were assessed on each plant. Crown rust resistance at both evaluation dates, was highly heritable and not affected by environment interaction. By contrast, winter dry matter showed a large family by location interaction and a high environmental influence. The results of the present study indicated that important progress in crown rust resistance in annual ryegrass can be achieved through phenotypic recurrent selection

Valoración clínico-radiológica de la articulación femoropatelar en prótesis que conservan los ligamentos cruzados

Se realizó un estudio retrospectivo en 104 pacientes con 116 prótesis tricompartimentales de rodilla que conservan los dos ligamentos cruzados. Se analizó la situación radiológica de la rótula, su relación con el implante protésico y los efectos de estos factores sobre la movilidad de la rodilla. Se realizaron proyecciones radiográficas AP, lateral y axial a 30° y se obtuvieron las siguientes variables: espesor residual rotuliano, posición del componente metálico respecto a la rótula, ángulo de Laurin, y grado de subluxación rotuliana. Se comparó la relación existente entre las diferentes variables, y éstas con respecto a los grados de flexión. Un 52,2% de las patelas presentaban una alineación central. Se obtuvo una relación significativa entre el ángulo de inclinación y el grado de subluxación patelar, sin embargo las variables a estudio no han presentado influencia en el grado de movilidad protésica, dentro de los rangos expuestos.A retrospective study was performed in 104 patients with 116 tricompartimental non-constrained knee prostheses. The radiological possition of the patella, its relationwith the prosthetic implant and the effect of these factors in the final range of movement of the knee were analyzed. AP, lateral and 30° axial radiological views were taken and the following variables were studied: residual patellar thickness, position of the metallic component with respect to the patella, Laurin''s angle and subluxation of the patella.The relation between these findings and also respect to postoperative maximum flexion were investigated. Overall, 52% of the patella tracked centrally. A statystical significant relation between the inclination angle and the patellar subluxation degree was obtained. However, within the exposed ranges, the studied variables have not demonstrated influence in the prosthetic range of movement