Temperature and Disorder Chaos in Low Dimensional Directed Paths

The responses of a $1+\epsilon$ dimensional directed path to temperature and to potential variations are calculated exactly, and are governed by the same scaling form. The short scale decorrelation (strong correlation regime) leads to the overlap length predicted by heuristic approaches; its temperature dependence and large absolute value agree with scaling and numerical observations. Beyond the overlap length (weak correlation regime), the correlation decays algebraically. A clear physical mechanism explains the behavior in each case: the initial decorrelation is due to `fragile droplets,' which contribute to the entropy fluctuations as $\sqrt{T}$, while the residual correlation results from accidental intersections of otherwise uncorrelated configurations.Comment: four pages, revtex4; minor modifications in the text and typos correcte

An Introduction to Breakdown Phenomena in Disordered Systems

The rupture of a medium under stress typifies breakdown phenomena. More generally, the latter encompass the dynamics of systems of many interacting elements governed by the interplay of a driving force with a pinning disorder, resulting in a macroscopic transition. A simple mean-field formalism incorporating these features is presented and applied to systems representative of fracture phenomena, social dilemmas, and magnets out of equilibrium. The similarities and differences in the corresponding mathematical structures are emphasized. The solutions are best obtained from a graphical method, from which very general conclusions may be drawn. In particular, the various classes of disorder distribution are treated without reference to a particular analytical or numerical form, and are found to lead to qualitatively different transitions. Finally, the notion of effective (or phenomenological) theory is introduced and illustrated for non-equilibrium disordered magnets.Comment: Pedagogical article published as part of a special issue on thermodynamics and statistical physics; 20 page

Utilização de crotalária no controle de nematóides da raiz do feijoeiro.

Este trabalho teve como objetivo avaliar o efeito da palhada de C. spectabilis no controle de nematóides da raiz do feijoeiro.bitstream/CNPAF/22189/1/comt_74.pd

Formation and Stability of Synaptic Receptor Domains

Neurotransmitter receptor molecules, concentrated in postsynaptic domains along with scaffold and a number of other molecules, are key regulators of signal transmission across synapses. Employing experiment and theory, we develop a quantitative description of synaptic receptor domains in terms of a reaction-diffusion model. We show that interactions between only receptor and scaffold molecules, together with the rapid diffusion of receptors on the cell membrane, are sufficient for the formation and stable characteristic size of synaptic receptor domains. Our work reconciles long-term stability of synaptic receptor domains with rapid turnover and diffusion of individual receptors.Comment: 5 pages, 3 figures, Supplementary Materia

Dynamical Adaptation in Photoreceptors

Adaptation is at the heart of sensation and nowhere is it more salient than in early visual processing. Light adaptation in photoreceptors is doubly dynamical: it depends upon the temporal structure of the input and it affects the temporal structure of the response. We introduce a non-linear dynamical adaptation model of photoreceptors. It is simple enough that it can be solved exactly and simulated with ease; analytical and numerical approaches combined provide both intuition on the behavior of dynamical adaptation and quantitative results to be compared with data. Yet the model is rich enough to capture intricate phenomenology. First, we show that it reproduces the known phenomenology of light response and short-term adaptation. Second, we present new recordings and demonstrate that the model reproduces cone response with great precision. Third, we derive a number of predictions on the response of photoreceptors to sophisticated stimuli such as periodic inputs, various forms of flickering inputs, and natural inputs. In particular, we demonstrate that photoreceptors undergo rapid adaptation of response gain and time scale, over ∼ 300 ms—i. e., over the time scale of the response itself—and we confirm this prediction with data. For natural inputs, this fast adaptation can modulate the response gain more than tenfold and is hence physiologically relevant

Self-assembly and plasticity of synaptic domains through a reaction-diffusion mechanism

Signal transmission across chemical synapses relies crucially on neurotransmitter receptor molecules, concentrated in postsynaptic membrane domains along with scaffold and other postsynaptic molecules. The strength of the transmitted signal depends on the number of receptor molecules in postsynaptic domains, and activity-induced variation in the receptor number is one of the mechanisms of postsynaptic plasticity. Recent experiments have demonstrated that the reaction and diffusion properties of receptors and scaffolds at the membrane, alone, yield spontaneous formation of receptor-scaffold domains of the stable characteristic size observed in neurons. On the basis of these experiments we develop a model describing synaptic receptor domains in terms of the underlying reaction-diffusion processes. Our model predicts that the spontaneous formation of receptor-scaffold domains of the stable characteristic size observed in experiments depends on a few key reactions between receptors and scaffolds. Furthermore, our model suggests novel mechanisms for the alignment of pre- and postsynaptic domains and for short-term postsynaptic plasticity in receptor number. We predict that synaptic receptor domains localize in membrane regions with an increased receptor diffusion coefficient or a decreased scaffold diffusion coefficient. Similarly, we find that activity-dependent increases or decreases in receptor or scaffold diffusion yield a transient increase in the number of receptor molecules concentrated in postsynaptic domains. Thus, the proposed reaction-diffusion model puts forth a coherent set of biophysical mechanisms for the formation, stability, and plasticity of molecular domains on the postsynaptic membrane.National Science Foundation (U.S.) (Award DMR-1206323

PENGARUH KUALITAS PELAYANAN TERHADAP KEPUASAN KONSUMEN DI PT. RAMAYANA MOTOR SUKOHARJO

This final project writing aims to find out the satisfaction level the consumers feel on the service given by PT Ramayana Motor Sukoharjo through the dimensions of service quality including Tangible, Reliability, Responsiveness, Assurance and empathy. The problem statement developed in this research is to find out the consumer satisfaction level on the performance given by PT. Ramayana Motor Sukoharjo. Technique of collecting data employed was observation, interview, and questionnaire method. The sampling technique used was simple random sampling with 100 respondents. In this research, technique of discussing used was descriptive analysis one, namely, the one to make a systematic, factual and accurate description about an object studied, while the consumer satisfaction was measured using importance performance analysis. From the research on 100 respondents about the service quality given by PT. Ramayana Motor Sukoharjo, it can be found that the results of consumer assessment on the performance given by the company include: viewed from the importance performance analysis, the highest consumer satisfaction level is in service procedure attribute or factor that will be done quickly, it can be seen from the percentage goodness of fit level of 113.28%, while the smallest attribute is that the employees have knowledge to answer the consumers’ question of 71.15%. The conclusion that can be drawn is that the result of Cartesian diagram of factors becomes the primary priority of PT. Ramayana Motor Sukoharjo and should be done because this factor is considered as important by the company and consumers, including: non strategic and not affordable dealer location, unattractive and untidy physical facility appearance. The recommendation given is that from the location side, the dealer should post the banner in front of its building so that the consumers can find the dealer location easily. From physical facility side, the product arrangement should be adjusted with the types of each product. Keywords: Tangible, Reliability, Responsiveness, Assurance and empathy

Obtenção de germoplasma de feijão livre de patógenos transmissíveis pela semente.

E descrito p programa de obtenção de germoplasma de feijão livre de patógenos transmitidos pela semente, em execução no Centro Nacional de Pesquisa de Arroz e Feijão (CNPAF), da Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA). São identificados os pontos que poderão tornar-se em breve, em gargalos na multiplicação da semente sadia, até a sua chegada ao agricultor: a. determinação das necessidades relativas de sementes das cultivares, por região; b. capacitação de técnicos da produção de sementes, na avaliação da condição sanitária do campo. c. adequação e/ou instalação de laboratórios para análise da sanidade de sementes; d. aperfeiçoamento das técnicas para estudo de sanidade de sementes.Palestra apresentada no I Simpósio Brasileiro de Pesquisa em Sementes, Brasília, DF, 23 a 27 de outubro de 1978