CALIBRATION OF SIMS MEASUREMENTS BY ION IMPLANTATION

The paper reviews some joint results of the above institutions in quantitative SIMS (Secondary Ion Mass Spectrometry) analysis of implanted dopants. Quantification of the SIMS was achieved by implanting marker ions as standards prior to analysis. Feasibility of this technique was first demonstrated by Giber et al. (1982). Further considerations will be presented

On-Farm Information: A Valuable Tool for the Sustainable Management of Mountain Pastures in Protected Natural Areas

Mountain pastures have traditionally been maintained by livestock. The analysis of data concerning farms\u27 characteristics, productive-reproductive management and land use of commercial farms can constitute a real approach to study these systems and the changes that are occurring. This information is necessary to develop new utilisation guidelines, making compatible livestock production and conservation of natural resources. This paper describes a methodological framework to study the issues described above through some examples taken out from a wider research project (Mandaluniz et al., 2003)

Effects of Livestock Grazing on the Shrub Vegetation Biomass in the ‘Sierra de Guara’ Natural Park (Spain)

The \u27Sierra de Guara\u27 Natural Park (80.7 Kha) is a Mediterranean mountain area in Huesca, south of the Spanish Pyrenees. Shrub and forest pastures dominate the Park. They are grazed mainly by sheep, but also by suckler cattle and goats. Average stocking rate is 0.15 LU/ha. As in other European mountain areas, agricultural activities have declined during the last few decades. This has caused a process of secondary vegetation succession towards shrub invasion, with consequent landscape changes. This study aimed to quantify the effect of grazing on shrub vegetation biomass

Magneto infra-red absorption in high electronic density GaAs quantum wells

Magneto infra-red absorption measurements have been performed in a highly doped GaAs quantum well which has been lifted off and bonded to a silicon substrate, in order to study the resonant polaron interaction. It is found that the pinning of the cyclotron energy occurs at an energy close to that of the transverse optical phonon of GaAs. This unexpected result is explained by a model taking into account the full dielectric constant of the quantum well.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let

Nonanalytic corrections to the specific heat of a three-dimensional Fermi liquid

We revisit the issue of the leading nonanalytic corrections to the temperature dependence of the specific heat coefficient, $\gamma (T)=C(T)/T,$ for a system of interacting fermions in three dimensions. We show that the leading temperature dependence of the specific heat coefficient $\gamma (T)-\gamma (0) \propto T^3 \ln T$ comes from two physically distinct processes. The first process involves a thermal excitation of a single particle-hole pair, whose components interact via a nonanalytic dynamic vertex. The second process involves an excitation of three particle-hole pairs which interact via the analytic static fixed-point vertex. We show that the single-pair contribution is expressed via the backscattering amplitude of quasiparticles at the Fermi surface. The three-pair contribution does not have a simple expression in terms of scattering in particular directions. We clarify the relation between these results and previous literature on both 3D and 2D systems, and discuss the relation between the nonanalyticities in $\gamma$ and those in spin susceptibilities

The entropy of the QCD plasma

Self-consistent approximations in terms of fully dressed propagators provide a simple expression for the entropy of an ultrarelativistic plasma, which isolates the contribution of the elementary excitations as a leading contribution. Further approximations, whose validity is checked on a soluble model involving a scalar field, allow us to calculate the entropy of the QCD plasma. We obtain an accurate description of lattice data for purely gluonic QCD, down to temperatures of about twice the transition temperature.Comment: 12 pages, 3 figures, REVTEX (minor modifications

Limits of the dynamical approach to non-linear response of mesoscopic systems

We have considered the nonlinear response of mesoscopic systems of non-interacting electrons to the time-dependent external field. In this consideration the inelastic processes have been neglected and the electron thermalization occurs due to the electron exchange with the reservoirs. We have demonstrated that the diagrammatic technique based on the method of analytical continuation or on the Keldysh formalism is capable to describe the heating automatically. The corresponding diagrams contain a novel element, {\it the loose diffuson}. We have shown the equivalence of such a diagrammatic technique to the solution to the kinetic equation for the electron energy distribution function. We have identified two classes of problems with different behavior under ac pumping. In one class of problems (persistent current fluctuations, Kubo conductance) the observable depends on the electron energy distribution renormalized by heating. In another class of problems (Landauer conductance) the observable is insensitive to heating and depends on the temperature of electron reservoirs. As examples of such problems we have considered in detail the persistent current fluctuations under ac pumping and two types of conductance measurements (Landauer conductance and Kubo conductance) that behave differently under ac pumping.Comment: 21 pages, RevTex, 10 eps.figures; final version to appear in Phys.Rev.

A thermodynamically self-consistent theory for the Blume-Capel model

We use a self-consistent Ornstein-Zernike approximation to study the Blume-Capel ferromagnet on three-dimensional lattices. The correlation functions and the thermodynamics are obtained from the solution of two coupled partial differential equations. The theory provides a comprehensive and accurate description of the phase diagram in all regions, including the wing boundaries in non-zero magnetic field. In particular, the coordinates of the tricritical point are in very good agreement with the best estimates from simulation or series expansion. Numerical and analytical analysis strongly suggest that the theory predicts a universal Ising-like critical behavior along the $\lambda$-line and the wing critical lines, and a tricritical behavior governed by mean-field exponents.Comment: 11 figures. to appear in Physical Review