THE IMPACTS OF THE CONSERVATION RESERVE PROGRAM ON RURAL COMMUNITIES: THE CASE OF THREE OREGON COUNTIES

Using an economic input/output model, the community personal income impacts of participating in the Conservation Reserve Program were analyzed for three rural Oregon counties. While individual farmers may benefit from participation, there may be net adverse impact on the community if the retired land is relatively productive or if the inputs that are no longer purchased would have been purchased locally. These negative effects may be exacerbated if participating farmers quit farming and leave the local area or if the Conservation Reserve Program benefits go to absentee landowners. The Conservation Reserve Program may then represent a conflict between community and national policy objectives.Agricultural and Food Policy, Community/Rural/Urban Development,

USSR Space Life Sciences Digest, issue 3

This is the third issue of NASA's USSR Space Life Sciences Digest. Abstracts are included for 46 Soviet periodical articles in 20 areas of aerospace medicine and space biology and published in Russian during the second third of 1985. Selected articles are illustrated with figures and tables from the original. In addition, translated introductions and tables of contents for seven Russian books on six topics related to NASA's life science concerns are presented. Areas covered are adaptation, biospherics, body fluids, botany, cardiovascular and respiratory systems, endocrinology, exobiology, gravitational biology, habitability and environmental effects, health and medical treatment, immunology, life support systems, metabolism, microbiology, musculoskeletal system; neurophysiology, nutrition, perception, personnel selection, psychology, radiobiology, and space physiology. Two book reviews translated from the Russian are included and lists of additional relevant titles available in English with pertinent ordering information are given

Stochastic dynamics of resistive switching: fluctuations lead to optimal particle number

Resistive switching (RS) is one of the foremost candidates for building novel types of non-volatile random access memories. Any practical implementation of such a memory cell calls for a strong miniaturization, at which point fluctuations start playing a role that cannot be neglected. A detailed understanding of switching mechanisms and reliability is essential. For this reason, we formulate a particle model based on the stochastic motion of oxygen vacancies. It allows us to investigate fluctuations in the resistance states of a switch with two active zones. The vacancies' dynamics are governed by a master equation. Upon the application of a voltage pulse, the vacancies travel collectively through the switch. By deriving a generalized Burgers equation we can interpret this collective motion as nonlinear traveling waves, and numerically verify this result. Further, we define binary logical states by means of the underlying vacancy distributions, and establish a framework of writing and reading such memory element with voltage pulses. Considerations about the discriminability of these operations under fluctuations together with the markedness of the RS effect itself lead to the conclusion, that an intermediate vacancy number is optimal for performance

Disorder Effects in Superconductors with Anisotropic Pairing: From Cooper Pairs to Compact Bosons

In the weak coupling BCS-approximation normal impurities do not influence superconducting T_{c} in significant manner in case of isotropic s-wave pairing. However, in case of d-wave pairing these are strongly pair-breaking. This fact is in rather strong contradiction with many experiments on disordered high-T_{c} superconductors assuming the d-wave nature of pairing in these systems. With the growth of electron attraction within the Cooper pair the system smoothly crosses over from BCS-pairs to compact Boson picture of superconductivity. As pairing strength grows and pairs become compact significant deviations from universal Abrikosov-Gorkov dependence of T_{c} on disorder appear in case of d-wave pairing with superconducting state becoming more stable than in the weak coupling case. As high-T_{c} superconductors are actually in the intermediate region with Cooper pairs size of the order of few interatomic lengths, these results can explain the relative stability of d-wave pairing under rather strong disordering.Comment: 8 pages, 3 figures, RevTeX 3.0, 1 Postscript figure attached, submitted to JETP Letter

Theory of the c-Axis Penetration Depth in the Cuprates

Recent measurements of the London penetration depth tensor in the cuprates find a weak temperature dependence along the c-direction which is seemingly inconsistent with evidence for d-wave pairing deduced from in-plane measurements. We demonstrate in this paper that these disparate results are not in contradiction, but can be explained within a theory based on incoherent quasiparticle hopping between the CuO2 layers. By relating the calculated temperature dependence of the penetration depth \lambda_c(T) to the c-axis resistivity, we show how the measured ratio \lambda_c^2(0) / \lambda_c^2(T) can provide insight into the behavior of c-axis transport below Tc and the related issue of ``confinement.''Comment: 4 pages, REVTEX with psfig, 3 PostScript figures included in compressed for

Energy Gap Induced by Impurity Scattering: New Phase Transition in Anisotropic Superconductors

It is shown that layered superconductors are subjected to a phase transition at zero temperature provided the order parameter (OP) reverses its sign on the Fermi-surface but its angular average is finite. The transition is regulated by an elastic impurity scattering rate $1/\tau$. The excitation energy spectrum, being gapless at the low level of scattering, develops a gap as soon as the scattering rate exceeds some critical value of $1/\tau_\star$.Comment: Revtex, 11 page

Combined effect of nonmagnetic and magnetic scatterers on critical temperatures of superconductors with different gap anisotropy

The combined effect of nonmagnetic and magnetic defects and impurities on critical temperatures of superconductors with different gap anisotropy is studied theoretically within the weak coupling limit of the BCS model. An expression is derived which relates the critical temperature to relaxation rates of charge carriers by nonmagnetic and magnetic scatterers, as well as to the coefficient of anisotropy of the superconducting order parameter on the Fermi surface. Particular cases of d-wave, (s+d)-wave, and anisotropic s-wave superconductors are briefly discussed.Comment: 5 pages, Te

Busca de documentos distribuída com o sistema MOTHRA

Este artigo apresenta o resultado de teste com o sistema MOTHRA, um sistema multiagente que emprega a tecnologia de agentes móveis para a busca de documentos na Web. Neste ambiente, características específicas impossibilitam a aplicação direta de técnicas de full text retrieval, sendo necessárias abordagens que possibilitem contornar este problema ou partir para novas soluções. Os testes no sistema MOTHRA apresentados abordam questões de desempenho e de qualidade dos documentos retornados frente á consulta original do usuário.This article presents the test results of the MOTHRA system, a multi-agent system which employs mobile agents for the retrieval of documents over the Web. Specific features of Web documents void the use of standard full text retrieval techniques, so specific approaches are required to solve this problem. The test results presented here are about the MOTHRA system performace and document relevance over the user query.Eje: Sistemas inteligentesRed de Universidades con Carreras en Informática (RedUNCI