Reply to comment on "Simple one-dimensional model of heat conduction which obeys Fourier's law"

In this reply we answer the comment by A. Dhar (cond-mat/0203077) on our Letter "Simple one dimensional model of heat conduction which obeys Fourier's law" (Phys. Rev. Lett. 86, 5486 (2001), cond-mat/0104453)Comment: 1 pag., 1 fi

Velocity Correlations, Diffusion and Stochasticity in a One-Dimensional System

We consider the motion of a test particle in a one-dimensional system of equal-mass point particles. The test particle plays the role of a microscopic "piston" that separates two hard-point gases with different concentrations and arbitrary initial velocity distributions. In the homogeneous case when the gases on either side of the piston are in the same macroscopic state, we compute and analyze the stationary velocity autocorrelation function C(t). Explicit expressions are obtained for certain typical velocity distributions, serving to elucidate in particular the asymptotic behavior of C(t). It is shown that the occurrence of a non-vanishing probability mass at zero velocity is necessary for the occurrence of a long-time tail in C(t). The conditions under which this is a $t^{-3}$ tail are determined. Turning to the inhomogeneous system with different macroscopic states on either side of the piston, we determine its effective diffusion coefficient from the asymptotic behavior of the variance of its position, as well as the leading behavior of the other moments about the mean. Finally, we present an interpretation of the effective noise arising from the dynamics of the two gases, and thence that of the stochastic process to which the position of any particle in the system reduces in the thermodynamic limit.Comment: 22 files, 2 eps figures. Submitted to PR

Etched distributed Bragg reflectors as three-dimensional photonic crystals: photonic bands and density of states

The photonic band dispersion and density of states (DOS) are calculated for the three-dimensional (3D) hexagonal structure corresponding to a distributed Bragg reflector patterned with a 2D triangular lattice of circular holes. Results for the Si/SiO$_2$ and GaAs/AlGaAs systems determine the optimal parameters for which a gap in the 2D plane occurs and overlaps the 1D gap of the multilayer. The DOS is considerably reduced in correspondence with the overlap of 2D and 1D gaps. Also, the local density of states (i.e., the DOS weighted with the squared electric field at a given point) has strong variations depending on the position. Both results imply substantial changes of spontaneous emission rates and patterns for a local emitter embedded in the structure and make this system attractive for the fabrication of a 3D photonic crystal with controlled radiative properties.Comment: 8 pages, 5 figures; to appear in Phys. Rev.

The Structure of Barium in the hcp Phase Under High Pressure

Recent experimental results on two hcp phases of barium under high pressure show interesting variation of the lattice parameters. They are here interpreted in terms of electronic structure calculation by using the LMTO method and generalized pseudopotential theory (GPT) with a NFE-TBB approach. In phase II the dramatic drop in c/a is an instability analogous to that in the group II metals but with the transfer of s to d electrons playing a crucial role in Ba. Meanwhile in phase V, the instability decrease a lot due to the core repulsion at very high pressure. PACS numbers: 62.50+p, 61.66Bi, 71.15.Ap, 71.15Hx, 71.15LaComment: 29 pages, 8 figure

Low temperature spin diffusion in the one-dimensional quantum O(3)O(3) nonlinear σ\sigma-model

An effective, low temperature, classical model for spin transport in the one-dimensional, gapped, quantum $O(3)$ non-linear $\sigma$-model is developed. Its correlators are obtained by a mapping to a model solved earlier by Jepsen. We obtain universal functions for the ballistic-to-diffusive crossover and the value of the spin diffusion constant, and these are claimed to be exact at low temperatures. Implications for experiments on one-dimensional insulators with a spin gap are noted.Comment: 4 pages including 3 eps-figures, Revte

Boosting the adoption of sustainable land-use systems for climate-change mitigation and peacebuilding

Sustainable land-use systems (SLUS), such as agroforestry with cocoa, implemented with organic fertiliser, with prescribed post-harvest practices and rainwater irrigation, can potentially increase farm productivity, while reducing pressure on natural resources by decreasing deforestation and providing legitimate incomes for rural households. SLUS also contribute to peacebuilding by providing sustainable income sources and enhancing social cohesion. Despite evidence of their potential and global efforts to promote their use, SLUS adoption rates remain low. Building on traditional ex-post generic adoption studies, we identify the enabling factors for farm-level transitions to SLUS in Colombia to propose policy design that will boost SLUS adoption in areas that are conflict affected and exposed to deforestation. We surveyed a sample of 922 cocoa producers in conflict-affected areas prone to deforestation. To reveal SLUS adoption factors, we (i) classified farmers according to number of sustainable methods applied; (ii) estimated an ordered probit econometric model; and (iii) assessed existing policies to promote cocoa production systems in Colombia, comparing their alignment with the adoption factors identified. We find a mismatch between farm-level adoption factors and policies promoting SLUS in Colombia. The principal factors enabling farm-level adoption of sustainable cocoa production system depend on: (i) cocoa plantation age; (ii) technical assistance provided; (iii) farmers’ social networks; and (iv) farmer-to-farmer interaction. National policies to promote sustainable cocoa are mostly oriented towards (i) renewing and rehabilitating established farming areas (directly related to crop age); (ii) expanding cocoa agroforestry systems; and (iii) establishing zero-deforestation cocoa production agreements. Our results indicate that to achieve wide-scale SLUS adoption, policies should focus on: (i) capacity building through technical assistance and strengthening farmers’ associations; (ii) strengthening social network structure to generate cascading information and social interactions between producers, and knowledge sharing; (iii) land-use conversion instead of expansion, for example from pastures to cocoa

Катетерный тромболизис в лечении острого венозного илиофеморального тромбоза в Дании

ТРОМБОЛИТИЧЕСКАЯ ТЕРАПИЯКАТЕТЕРИЗАЦИЯТРОМБОЗ ВЕНОЗНЫЙ /ЛЕК ТЕРКОНЕЧНОСТЬ НИЖНЯ