Multivariate nonlinear models for vectors of proportions: a generalized least squares approach

A general model is presented for analyzing samples of vectors of proportions whose expectations are smooth functions of a finite set of covariates. The expectations may be nonlinear. The distributions of the observed vectors of proportions are not necessarily multinomial but the models specify the form of the first two moments. These models can be viewed as generalizations of logit models which allow variation among samples proportions which are greater than the variation associated with independent multinomial samples;Regularity conditions are established for the strong consistency and asymptotic normality of a minimum distance estimator of the model parameters. An associated One-Step-Gauss-Newton estimator is also investigated. Several specific versions of the general model are given more detailed consideration;Finite sample properties of the estimation procedures are investigated with a Monte Carlo study. Nominal levels for chi-square tests of the expectation model parameters, the properties of the estimated extra parameters and the biases of the estimators are examined. Data generated under two different sampling schemes, the logistic multinomial and the logistic multinomial with extra variation, are used in the Monte Carlo study. Example applications are given

An Extension of Generalized Linear Models to Finite Mixture Outcome Distributions

Finite mixture distributions arise in sampling a heterogeneous population. Data drawn from such a population will exhibit extra variability relative to any single subpopulation. Statistical models based on finite mixtures can assist in the analysis of categorical and count outcomes when standard generalized linear models (GLMs) cannot adequately account for variability observed in the data. We propose an extension of GLM where the response is assumed to follow a finite mixture distribution, while the regression of interest is linked to the mixture's mean. This approach may be preferred over a finite mixture of regressions when the population mean is the quantity of interest; here, only a single regression function must be specified and interpreted in the analysis. A technical challenge is that the mean of a finite mixture is a composite parameter which does not appear explicitly in the density. The proposed model is completely likelihood-based and maintains the link to the regression through a certain random effects structure. We consider typical GLM cases where means are either real-valued, constrained to be positive, or constrained to be on the unit interval. The resulting model is applied to two example datasets through a Bayesian analysis: one with success/failure outcomes and one with count outcomes. Supporting the extra variation is seen to improve residual plots and to appropriately widen prediction intervals

Percepciones sobre lo público y desigualdades entre la juventud de Lima Metropolitana y el Callao

El documento se basa en la encuesta a la juventud del Instituto de Estudios Peruanos (IEP), aplicada por GfK, me centro en las percepciones de los jóvenes de Lima Metropolitana y Callao sobre lo que ampliamente podemos denominar “lo público”. El autor entiende por percepciones sobre lo público a todas aquellas opiniones sobre aspectos que tocan el papel de los jóvenes en la sociedad, fuera de las esferas de la familia y el trabajo: su asociacionismo voluntario, sus juicios sobre la política, su grado de tolerancia frente a la diferencia, sus autodefiniciones identitarias y las experiencias de exclusión por las que han pasado, entre otros temas. La encuesta que alimenta estas reflexiones confirma detalles interesantes sobre las desigualdades horizontales y territoriales que sufren los jóvenes de la gran Lima, que afectan particularmente su capacidad para sustentar iniciativas de asociacionismo voluntario en el tránsito hacia la adultez, de dar opiniones informadas sobre política y de valorar elementos de las tradicionales políticas liberales y republicanas. Asimismo, a la par que soportan estas desigualdades, los jóvenes (en especial aquellos entrampados en la falta de recursos económicos y salarios bajos) continúan excluyendo a otros grupos sociales y eluden los debates sobre su identidad, algo que —de momento— los distancia de sus coetáneos en los países desarrollados, la llamada generación millennial

A Numerical Assessment of an Effective Envelope-Tracking Semiconductor Optical Amplifier Design for Coherent-Optical OFDM Transmission

International audienceThe inherent nonlinear effects associated to Semiconductor Optical Amplifiers (SOAs) may translate into a transmission performance loss for non-constant envelope modulation formats. However, a variety of linearization schemes may be adopted for coping with these impairments and offering an effective system design. In this paper, an envelope tracking (ET) technique is investigated for linearizing an SOA-based Coherent Optical OFDM transmitter. An optimized design of the ET subsystem is performed under various scenarios, with the eventual joint use of Peak-to-Average Power Ratio (PAPR) reduction either via hard-clipping or nonlinear companding. A thorough carrier density analysis is performed in the amplifier, for various target gain values, so as to assess the effectiveness of the proposed scheme. Morever, we investigate the robustness of the proposed approach against some parameters variation both inside the ET path (DAC characteristics and bandwidth limited envelope generation). Extensive simulations performed with a precise SOA model show that up to 8 dB (resp. 7 dB) BER improvement can be achieved via the proposed scheme in the case of 4-QAM/OFDM (resp. 16-QAM/OFDM), compared to the conventional system with no linearization, and that even an envelope quantized with 2 bits still enables a significant performance increase

Draft genome sequence of Bradyrhizobium sp. strain Oc8 isolated from Crotalaria ochroleuca nodule

In this study, we report the draft genome sequence of Bradyrhizobium sp. strain Oc8, a rhizobium isolated from Crotalaria ochroleuca,efficient in C. ochroleuca, C. juncea, C. spectabilis, and Cajanus cajan. The whole genome of the strain Oc8 contains 46 scaffolds, 8,283,342 bp, and 63.27% of GC content. Bradyrhizobium sp. Oc8 is an effective nitrogen-fixing bacterium with potential use as an inoculant for legumes used as cover crops and green manures.ANII: FMV_ 3_2016_1_12549

Application of a long-range swept source optical coherence tomography-based scheme for dimensional characterization of multilayer transparent objects

This work presents the use of a recently developed interferometric system based on the sweptsource optical coherence tomography (SS-OCT) technique, which allows the characterization of transparentand semitransparent multilayer systems employing a tunable fiber-optic laser with a coherence length suitablefor achieving long-deep range imaging (>10 cm). The inclusion of fiber Bragg gratings in the system allows it toperform a self-calibration in each sweep of the light source. Measurements carried out on cuvettes, ampoules,small bottles, and glass containers used in the pharmaceutical industry are presented. The thicknesses of thewalls and the distance between them were determined. Transparent and semitransparent objects of a multilayertype of different thicknesses were also measured. The configuration presented allows extension of the measurementrange obtainable with the usual OCT systems, demonstrating the potentiality of the proposed scheme tocarry out quality control in industrial application.Centro de Investigaciones ÓpticasFacultad de Ingenierí

A produção científica brasileira segundo os dados do I.S.I. - III. C.I. E. N. C. I. A /Brasil um catálogo multiindexado sobre a produção científica brasileira de circulação internacional

Dados sobre a produção cientifica brasileira de circulação internacional catalogada pelo Institute for Scientific Information podem ser recuperados por um perfil de busca especial do serviço de disseminação seletiva de informação ASCA daquela instituição e enviados na forma de listagens em fita magnética. Os autores desenvolveram programas para o processamento direto por computador das informações contidas nas fitas e que geram automaticamente um catálogo multiindexado sobre nossa produção científica. Esse catálogo multiindexado, que poderá vir a ser editado anualmente na forma de livro e na forma de fita magnética, recebeu o nome de C.I.E.N.C.I.A./BRASIL (Catálogo Indexado por Endereços e Nomes de Cientistas e Instituições e por Periódico e Assunto). São discutidas as potencialidades e características desse novo instrumento de análise, acompanhamento e divulgação de nossa produção cientifica de circulação internacional. Abstract Data about the scientific publications of Brazilian authors indexed by the Institute for Scientific Information can be retrieved by a special search profile of its ASCA service of selective dissemination of information and sent in the form of magnetic tapes. Computer programs were developed by the authors to process directly the information on the tapes in order to generate a multi-indexed catalog about our scientificproduction. This index, which could be publishedon a yearly basis, has received the name of C.I.E.N.C.I.A./BRASIL ( = S.C.I.E.N.C.E./BRAZIL;Index Arranged by Addresses and Names of Scientists and Institutions as well as by Journals and Subject). The characteristics of this index and its use for the analysis, follow-up and divulgation of Brazilian science are discussed