Importance Sampling for multi-constraints rare event probability

Improving Importance Sampling estimators for rare event probabilities requires sharp approx- imations of the optimal density leading to a nearly zero-variance estimator. This paper presents a new way to handle the estimation of the probability of a rare event defined as a finite intersection of subset. We provide a sharp approximation of the density of long runs of a random walk condi- tioned by multiples constraints, each of them defined by an average of a function of its summands as their number tends to infinity.Comment: Conference pape

Physiological maturity of pigeonpea at three sowing periods.

Conduziu-se, durante o ano agrícola 1985/86, na área experimental do Departamento de Fitotecnia da Faculdade de Ciências Agrárias e Veterinárias (FCAVJ), UNESP, Campos de Jaboticabal, um experimento com o objetivo de se estudar a maturação fisiológica de sementes de guandu (Cajanus cajan (L.) Millsp.), em três épocas de semeadura. A semeadura foi realizada nos meses de dezembro/85, janeiro e fevereiro/86, para a primeira, segunda e terceira épocas, respectivamente. Posteriormente, realizaram-se coletas semanais de vagens, obtidas em inflorescências previamente marcadas por ocasião do florescimento de 50% das plantas da parcela. Foram avaliados os seguintes parâmetros: peso seco e teor de umidade das sementes, percentagem de germinação e índice de velocidade de emergência (vigor) das sementes. Verificou- se coincidência entre os pontos de máximo peso seco, máxima percentagem de germinação e vigor, e menor teor de umidade, embora tenha-se constatado efeito das condições climáticas, em função das épocas de semeadura. A máxima germinação e vigor ocorreu aos 58 dias após o florescimento, para três épocas. O máximo peso seco também ocorreu aos 58 dias, exceto para a semeadura de dezembro, que ocorreu aos 65 dias. Os menores teores de umidade foram verificados aos 58, 64 e 72 dias após o florescimento para a primeira, segunda e terceira épocas, respectivamente.The experiment was conducted during the crop season 1985/86 at the experimental area of the Departamento de Fitotecnia da Faculdade de Ciências Agrárias e Veterinárias of the Universidade do Estado de São Paulo (UNESP), Campos of Jaboticabal, SP, Brazil, to study the physiological maturation of pigeonpea (Cajanus cajan (L.) Millsp.) at three sowing periods. Seeding was done at the months of December 1985, January and February 1986 for the first, second and third periods, respectively. Pods were collected weekly, from previously chosen inflorescences, at the flowering season, from over 50% of the plants each plot. The following parameters were analysed: seed dry weight and moisture content, germination percentage, and seed speed of emergence (vigor). A coincidence between the point of maximum dry weight, germination percentage and vigor and lower moisture content was observed, although the climatic conditions had effects due to the different sowing periods. Maximum germination and vigor occurred, in an overall analysis at the 58th day after flowering for the three sowing periods. Also the greatest dry weight occurred at the 58th day, except for the period of December that had that value at the 65th day after flowering. The lowest moisture content of the seeds was detected at 58, 64 and 72 days after flowering for the first, second and third sowing periods, respectively

Novel Multifunctional Materials Based on Oxide Thin Films and Artificial Heteroepitaxial Multilayers

Transition metal oxides show fascinating physical properties such as high temperature superconductivity, ferro- and antiferromagnetism, ferroelectricity or even multiferroicity. The enormous progress in oxide thin film technology allows us to integrate these materials with semiconducting, normal conducting, dielectric or non-linear optical oxides in complex oxide heterostructures, providing the basis for novel multi-functional materials and various device applications. Here, we report on the combination of ferromagnetic, semiconducting, metallic, and dielectric materials properties in thin films and artificial heterostructures using laser molecular beam epitaxy. We discuss the fabrication and characterization of oxide-based ferromagnetic tunnel junctions, transition metal-doped semiconductors, intrinsic multiferroics, and artificial ferroelectric/ferromagetic heterostructures - the latter allow for the detailed study of strain effects, forming the basis of spin-mechanics. For characterization we use X-ray diffraction, SQUID magnetometry, magnetotransport measurements, and advanced methods of transmission electron microscopy with the goal to correlate macroscopic physical properties with the microstructure of the thin films and heterostructures.Comment: 21 pages, 21 figures (2 figures added, typos corrected

Evidence of strong small-scale population structure in the Antarctic freshwater copepod Boeckella poppei in lakes on Signy Island, South Orkney Islands

Environmental conditions were particularly severe during the Last Glacial Maximum, altering the distribution of the Southern Hemisphere biota, particularly at higher latitudes. The copepod Boeckella poppei is the only macroscopic continental invertebrate species known to be distributed today across the three main biogeographic regions in Antarctica as well as in southern South America. Signy Island (South Orkney Islands) is a unique location for the study of Antarctic freshwater ecosystems due to its location and geographic isolation; it contains 17 lakes in several low altitude catchments. We conducted phylogeographic and demographic analyses using the cox1 gene on 84 individuals of B. poppei from seven lakes across Signy Island. We recorded low levels of genetic diversity and a strong genetic differentiation signal between the eastern and western valleys within the island. Phylogeographic structure and demographic inference analyses suggested at least one asymmetrical dispersal event from west to east. Demographic inference detected a strong signal of population growth during the deglaciation process, which may have followed either (1) a strong genetic bottleneck due to a reduction in population size during the last glacial period, or (2) a founder effect associated with postglacial recolonization of Signy Island from elsewhere. The genetic architecture of this island's populations of B. poppei shows that historical events, rather than continuous dispersal events, likely played a major role in the species' current distribution. Finally, our study considers possible mechanisms for dispersal and colonization success of the most dominant species in the Antarctic freshwater community

The large deviation approach to statistical mechanics

The theory of large deviations is concerned with the exponential decay of probabilities of large fluctuations in random systems. These probabilities are important in many fields of study, including statistics, finance, and engineering, as they often yield valuable information about the large fluctuations of a random system around its most probable state or trajectory. In the context of equilibrium statistical mechanics, the theory of large deviations provides exponential-order estimates of probabilities that refine and generalize Einstein's theory of fluctuations. This review explores this and other connections between large deviation theory and statistical mechanics, in an effort to show that the mathematical language of statistical mechanics is the language of large deviation theory. The first part of the review presents the basics of large deviation theory, and works out many of its classical applications related to sums of random variables and Markov processes. The second part goes through many problems and results of statistical mechanics, and shows how these can be formulated and derived within the context of large deviation theory. The problems and results treated cover a wide range of physical systems, including equilibrium many-particle systems, noise-perturbed dynamics, nonequilibrium systems, as well as multifractals, disordered systems, and chaotic systems. This review also covers many fundamental aspects of statistical mechanics, such as the derivation of variational principles characterizing equilibrium and nonequilibrium states, the breaking of the Legendre transform for nonconcave entropies, and the characterization of nonequilibrium fluctuations through fluctuation relations.Comment: v1: 89 pages, 18 figures, pdflatex. v2: 95 pages, 20 figures, text, figures and appendices added, many references cut, close to published versio

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

A conceptual framework for analysing and planning synthetic approaches to diverse lead-like scaffolds.

Historically, chemists' exploration of chemical space has been exceptionally uneven and unsystematic. This feature article outlines a comprehensive conceptual framework that may be used to capture, analyse and plan synthetic approaches that may address this historically uneven exploration. Illustrative examples of synthetic approaches that target, or have potential to target, broad tracts of lead-like chemical space are presented within the context of this conceptual framework. Particular emphasis is placed on synthetic approaches that enable the combinatorial variation of molecular scaffold, particularly within the boundaries of lead-like chemical space