315 research outputs found
Lucha contra la pobreza en América Latina: ¿Selectividad y universalismo?
La ineficacia de las estrategias del bienestar en América Latina basadas exclusivamente
en la extensión de los derechos contributivos ha auspiciado nuevas discusiones sobre la
selectividad y el universalismo en la provisión de políticas sociales. La puesta en vigor
de programas de lucha contra la pobreza mediante comprobación de recursos de los
beneficiarios (programas de transferencias de rentas condicionadas) es objeto de
examen y valoración en la ponencia. Se discute si tal selectividad favorece un
universalismo básico, y si los programas de comprobación de recursos pueden ser
transformados eventualmente en políticas de prestaciones universales
Поиск фрагмента изображения с использованием нейронной сети Кохонена
This paper considers the ability to sample on a series of images using Kohonen neural network, analyzing the distribution of basic colors. Objective is to improve the quality and speed of search for fragments of the image by creating software that performs clustering colors images
Разработка рекомендаций по предупреждению осложнений при бурении скважин в различных геолого-технических условиях
Объектом исследования являются методы предупреждения осложнений при бурении скважин в различных горно-геологических условиях. Цель работы разработка рекомендаций по предупреждению осложнений. В процессе работы был проведен анализ и систематизация накопленного в данной области опыта, разработок и исследований. В результате работы была разработана классификация технических, технологических и организационных мер предупреждения осложнений при бурении.The object of the study is the methods of preventing complications when drilling wells in various mining and geological conditions. The purpose of the work is to develop recommendations for the prevention of complications. In the course of the work, the analysis and systematization of the accumulated experience, developments and research in this area was carried out. As a result of the work, a classification of technical, technological and organizational measures to prevent complications during drilling was developed
Inequality restricted and pre-test estimation in a mis-specified econometric model
This thesis is concerned with the finite sample properties of some estimators of the unknown parameters in a linear model which is (possibly) mis-specified through the exclusion of relevant regressors. We assume that in addition to sample information, prior information regarding the unknown parameters is available in the form of a linear inequality constraint imposed on the regression coefficients. The combination of this type of prior information and sample information in specifying the corresponding statistical model leads to what has been identified in the literature as the inequality restricted estimator. If the statistical significance of the inequality constraint is tested prior to the estimation process, then the estimator thereby generated is called the inequality pre-test estimator.
The properties of these estimators of the coefficient vector in a properly specified model have been examined rather thoroughly in the literature. In this thesis, we extend the results reported in the literature to the case where the underlying regression model is underfitted. We also investigate the sampling performance of the corresponding estimators for the model's disturbance variance, as well as the choice of an optimal size for the pre-test. The general background and motivation for this study are given in Chapter 1.
Much of the earlier research on inequality restricted and pre-test estimation are built on results from studies that assume that the prior information is in the form of linear equality restrictions. We survey the relevant literature in this area in Chapter 2. Chapter 3 reviews the literature on inequality restricted and pre-test estimation. We focus on this problem in the context of the standard linear model with a single linear inequality constraint on the coefficient vector, as this is directly related to the theme of this thesis.
In Chapter 4, we derive and evaluate the risk, under quadratic loss, of the inequality restricted and pre-test estimators for the regression prediction vector in an underfitted model. This analysis takes the established literature further by allowing for mis-specification in the regressor matrix. We consider the risk of the prediction vector, rather than the coefficient vector itself, so that our results are data independent. The risk functions of the corresponding estimators for the regression disturbance variance in the properly specified and underfitted models are derived in Chapters 6 and 7 respectively.
As in the case where the prior information exists as linear equality restrictions, our results show that when the model is underfitted, the use of valid prior information does not necessarily guarantee a reduction in risk. This result holds for the estimation of both the prediction vector and the scale parameter. When one is estimating the regression disturbance variance, with an appropriate choice of test size, the inequality pre-test estimator can uniformly dominate the estimator that uses sample information only. We also find that the risk functions of the estimators of the error variance are affected more by mis-specification than are the corresponding predictive risks.
In the case where no strictly dominating estimator exists, the question of the choice of an optimal critical value of the pre-test remains. Chapters 5 and 8 explore this issue when one is estimating the prediction vector and scale parameter respectively. We find that most of our results concur qualitatively with those reported in the literature when the prior information exists as exact equality restrictions.
Chapter 9 contains some concluding remarks and a summary of the major results obtained in earlier chapters. We also outline some possible future research topics in this general area
Equipment and methods for measuring reflectance of concentrating solar reflector materials
The proper optical characterization of solar reflector materials is a challenging task. Although several commercial instruments exist to measure reflectance, they have been developed for other applications and often do not meet all the specific requirements demanded by the solar thermal industry. In particular, the characterization of solar reflectors involve the complete solar spectral wavelength range, an incidence angle range from near normal to 70° and most importantly a very narrow acceptance angle range from near specular to 20 mrad. The accurate measurement of reflectance as a function of all the previously mentioned parameters has not been commercially implemented. This paper reviews the different alternatives to measure reflector materials, describes reflectance models used to approximate the missing information and presents current research work on prototype reflectometers to fill the gap
Equipment and methods for measuring reflectance of concentrating solar reflector materials
The proper optical characterization of solar reflector materials is a challenging task. Although several commercial instruments exist to measure reflectance, they have been developed for other applications and often do not meet all the specific requirements demanded by the solar thermal industry. In particular, the characterization of solar reflectors involve the complete solar spectral wavelength range, an incidence angle range from near normal to 70° and most importantly a very narrow acceptance angle range from near specular to 20 mrad. The accurate measurement of reflectance as a function of all the previously mentioned parameters has not been commercially implemented. This paper reviews the different alternatives to measure reflector materials, describes reflectance models used to approximate the missing information and presents current research work on prototype reflectometers to fill the gap
Immune-profiling of innate and adaptive immunity following three vaccinations of the MERS vaccine candidate MVA-MERS-S
Middle East Respiratory Syndrome (MERS) is a respiratory disease caused by MERS coronavirus (MERS-CoV). In follow-up to a phase 1 trial, we performed a longitudinal analysis of immune responses following immunization with the Modified Vaccinia virus Ankara (MVA)-based vaccine MVA-MERS-S encoding MERS-CoV-spike protein. Three homologous intramuscular immunizations were administered on days 0 and 28 with a late booster vaccination at 12±4 months. Vaccination with MVA-MERS-S revealed a benign safety profile. No serious or severe adverse events were reported. Here, we analyzed innate and adaptive immune responses to the MVA-MERS-S in ten vaccinees. For this approach, blood samples were collected frequently for a period of about three years. Serum, plasma and PBMCs were analyzed at multiple time points using different techniques, which allowed an in-depth characterization of immune responses elicited by MVA-MERS-S.
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Myo/Nog cell regulation of bone morphogenetic protein signaling in the blastocyst is essential for normal morphogenesis and striated muscle lineage specification
AbstractCells that express MyoD mRNA, the G8 antigen and the bone morphogenetic protein (BMP) inhibitor noggin (Nog) are present in the epiblast before gastrulation. Ablation of “Myo/Nog” cells in the blastocyst results in an expansion of canonical BMP signaling and prevents the expression of noggin and follistatin before and after the onset of gastrulation. Once eliminated in the epiblast, they are neither replaced nor compensated for as development progresses. Older embryos lacking Myo/Nog cells exhibit severe axial malformations. Although Wnts and Sonic hedgehog are expressed in ablated embryos, skeletal muscle progenitors expressing Pax3 are missing in the somites. Pax3+ cells do emerge adjacent to Wnt3a+ cells in vitro; however, few undergo skeletal myogenesis. Ablation of Myo/Nog cells also results in ectopically placed cardiac progenitors and cardiomyocytes in the somites. Reintroduction of Myo/Nog cells into the epiblast of ablated embryos restores normal patterns of BMP signaling, morphogenesis and skeletal myogenesis, and inhibits the expression of cardiac markers in the somites. This study demonstrates that Myo/Nog cells are essential regulators of BMP signaling in the early epiblast and are indispensable for normal morphogenesis and striated muscle lineage specification
Full genome characterization of porcine circovirus type 3 isolates reveals the existence of two distinct groups of virus strains
Background: The occurrence of the novel porcine circovirus type 3 (PCV3) was reported from the Americas, Asia arid Europe. Although this virus was detected in association with various clinical syndromes in pigs, its role as possible swine pathogen remains unclear. PCV3 was detected with high prevalence in Polish farms, but to date no genome sequences were available from European PCV3 strains. Methods: We collected 1060 serum samples from piglets at the age of 20-24 weeks from 53 farms distributed all over Germany. PCV3 DNA was detected using a real-time PCR and subsequently complete PCV3 genome sequences were obtained after multiply primed rolling circle amplification and sequencing of overlapping PCR products. Phylogenetic analysis was performed by neighbor-joining method and maximum likelihood method. Results: We obtained 15 complete PCV3 genome sequences as well as nine partial sequences including the putative ORFs 1, 2 and 3 from PCV3 viremic animals in German pig farms. Phylogenetic analysis of these German as well as 30 full genome sequences received from GenBank divided the PCV3 strains into two main groups and several subclusters. Furthermore, we were able to define group specific amino acid patterns in open reading frame 1 and 2. Conclusion: PCV3 is distributed with high prevalence in German pig industry. Phylogenetic analysis revealed two clearly separated groups of PCV3 strains, which might be considered as PCV3 genotypes. Specific nucleotide and amino acid marker positions may serve for easy and fast intraspecies classification and genotyping of PCV3 strains. No correlation between PCV3 variants with their geographical origin was evident We found the same diversity of PCV3 strains in Germany as in other countries. We hypothesize that PCV3 is not a newly emerging virus in the German pig population. Future studies will have to show, if PCV3 genotype specific biological properties are evident
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