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External Variables (external + variable)
Selected AbstractsCross Section and Panel Data Estimators for Nonseparable Models with Endogenous RegressorsECONOMETRICA, Issue 4 2005Joseph G. Altonji We propose two new methods for estimating models with nonseparable errors and endogenous regressors. The first method estimates a local average response. One estimates the response of the conditional mean of the dependent variable to a change in the explanatory variable while conditioning on an external variable and then undoes the conditioning. The second method estimates the nonseparable function and the joint distribution of the observable and unobservable explanatory variables. An external variable is used to impose an equality restriction, at two points of support, on the conditional distribution of the unobservable random term given the regressor and the external variable. Our methods apply to cross sections, but our lead examples involve panel data cases in which the choice of the external variable is guided by the assumption that the distribution of the unobservable variables is exchangeable in the values of the endogenous variable for members of a group. [source] Mixture-based adaptive probabilistic controlINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 2 2003Miroslav Kárný Abstract Quasi-Bayes algorithm, combined with stabilized forgetting, provides a tool for efficient recursive estimation of dynamic probabilistic mixture models. They can be interpreted either as models of closed-loop with switching modes and controllers or as a universal approximation of a wide class of non-linear control loops. Fully probabilistic control design extended to mixture models makes basis of a powerful class of adaptive controllers based on the receding-horizon certainty equivalence strategy. Paper summarizes the basic elements mentioned above, classifies possible types of control problems and provides solution of the key one referred to as ,simultaneous' design. Results are illustrated on mixtures with components formed by normal auto-regression models with external variable (ARX). Copyright © 2003 John Wiley & Sons, Ltd. [source] A neurological examination score for the assessment of spinocerebellar ataxia 3 (SCA3)EUROPEAN JOURNAL OF NEUROLOGY, Issue 4 2008C. Kieling Spinocerebellar ataxias (SCAs) are characterized by a heterogeneous set of clinical manifestations. Our aims were to assess the neurological features of SCA3, and to describe and test the feasibility, reliability, and validity of a comprehensive Neurological Examination Score for Spinocerebellar Ataxia (NESSCA). The NESSCA was administered to molecularly diagnosed SCA3 patients at an outpatient neurogenetics clinic. The scale, based on the standardized neurological examination, consisted of 18 items that yielded a total score ranging from 0 to 40. The score's interrater reliability and internal consistency were investigated, and a principal components analysis and a correlation with external measures were performed. Ninety-nine individuals were evaluated. Interrater reliability ranged from 0.8 to 1 across individual items (P < 0.001); internal consistency, indicated by Cronbach's alpha, was 0.77. NESSCA scores were significantly correlated with measures of disease severity: disease stage (rho = 0.76, P < 0.001), duration (rho = 0.56, P < 0.001), and length of CAG repeat (rho = 0.30, P < 0.05). NESSCA was a reliable measure for the assessment of distinct neurological deficits in SCA3 patients. Global scores correlated with all external variables tested, showing NESSCA to be a comprehensive measure of disease severity that is both clinically useful and scientifically valid. [source] The contribution of domestic and external factors to emerging market currency crises: an early warning systems approach,INTERNATIONAL JOURNAL OF FINANCE & ECONOMICS, Issue 3 2007Steven B. Kamin Abstract In this paper, a modified ,early warning system' (EWS) approach is developed to identify the roles of domestic and external factors in emerging market crises. Several probit models of currency crises were estimated for 26 emerging market countries. These models were used to identify the separate contributions to the probabilities of crisis of domestic and external variables. We found that, relative to domestic factors, adverse external shocks and large external imbalances contributed little to the average estimated probability of crisis in emerging market countries, but accounted for much more of the spikes in the probability of crisis estimated to occur during actual crisis years. We interpret these results to suggest that while, on average over time, domestic factors have tended to contribute to much of the underlying vulnerability of emerging market countries, adverse swings in external factors may have been important in pushing economies ,over the edge' and into currency crisis. In consequence, the costs of giving up exchange rate flexibility through adoption of strongly fixed exchange rate regimes,e.g. currency boards or dollarization,may be quite high for some countries. Published in 2007 by John Wiley & Sons, Ltd. [source] Vorgehensmodell zur Abbildung und Analyse des Lebenszykluserfolges von Werkstoffen , Konzeption und beispielhafte Veranschaulichung.MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 6 2010Modeling approach for the life cycle profit of materials, case study, conceptual design Life Cycle Costs; Life Cycle Profit; Modeling Approach; Cost Management Abstract Eine langfristig erfolgreiche Entwicklung, Herstellung und Verwendung von (neuen) Werkstoffen setzt voraus, dass die daran beteiligten, auf wirtschaftlichen Erfolg angewiesenen Unternehmen mit diesen Werkstoffen einen positiven monetären Lebenszykluserfolg erzielen. Die Ermittlung eines solchen Lebenszykluserfolgs ist allerdings eine komplexe Aufgabenstellung, wird dieser doch durch eine Vielzahl verschiedenartiger unternehmensexterner und -interner Größen beeinflusst. Gerade bei derartigen komplexen Problemstellungen bietet es sich an, Vorgehensmodelle für eine systematische und strukturierte Problemanalyse und -zerlegung sowie die darauf basierende Bildung und Auswertung von monetären Lebenszyklusmodellen zu nutzen. Im vorliegenden Beitrag soll daher ein Vorgehensmodell zur Ermittlung und Analyse des Lebenszykluserfolgs von Werkstoffen zunächst konzipiert und anschließend anhand eines Fallbeispiels veranschaulicht werden. Long-term successful development, production and use of (new) materials presuppose that involved companies achieve a positive monetary life cycle benefit with these materials. However, the appraisal of this life cycle profit is a demanding task, since the profit is influenced by a huge number of different internal and external variables. Especially in case of such complex problems procedure models can support the systematic and structured analysis and decomposition of the problems as well as the creation and evaluation of monetary life cycle models basing on that. Therefore, this paper offers a suitable modeling approach for the life cycle profit of materials, which is illustrated by a case study. [source] Environmental influence and cohort effects in a sexual ornament in the house sparrow, Passer domesticusOIKOS, Issue 2 2006Henrik Jensen Presence of phenotypic variation is necessary for selection to occur, yet processes affecting variation in sexually selected characters in natural populations are poorly understood. Here we examine whether variation in a sexual ornament (badge size) of male house sparrows (Passer domesticus) is dependent on individual variation in the conditions during early ontogenetic stages, and whether this variation and the population-wide effects of external variables such as weather or population size jointly will generate consistent differences among cohorts later in life. Variation in badge size was independent of adult body size, whereas heavier fledglings and fledglings in good body condition developed smaller visible badges as adults. Furthermore, strong cohort-effects were present, caused by a combined effect of density-dependence and weather during the early development in the moulting period and autumn after hatching. Thus, badge size is an environmentally-dependent trait in house sparrows, and likely to be under the influence of both natural and sexual selection. [source] A novel view on stem cell development: analysing the shape of cellular genealogiesCELL PROLIFERATION, Issue 2 2009I. Glauche Objectives: The analysis of individual cell fates within a population of stem and progenitor cells is still a major experimental challenge in stem cell biology. However, new monitoring techniques, such as high-resolution time-lapse video microscopy, facilitate tracking and quantitative analysis of single cells and their progeny. Information on cellular development, divisional history and differentiation are naturally comprised into a pedigree-like structure, denoted as cellular genealogy. To extract reliable information concerning effecting variables and control mechanisms underlying cell fate decisions, it is necessary to analyse a large number of cellular genealogies. Materials and Methods: Here, we propose a set of statistical measures that are specifically tailored for the analysis of cellular genealogies. These measures address the degree and symmetry of cellular expansion, as well as occurrence and correlation of characteristic events such as cell death. Furthermore, we discuss two different methods for reconstruction of lineage fate decisions and show their impact on the interpretation of asymmetric developments. In order to illustrate these techniques, and to circumvent the present shortage of available experimental data, we obtain cellular genealogies from a single-cell-based mathematical model of haematopoietic stem cell organization. Results and Conclusions: Based on statistical analysis of cellular genealogies, we conclude that effects of external variables, such as growth conditions, are imprinted in their topology. Moreover, we demonstrate that it is essential to analyse timing of cell fate-specific changes and of occurrence of cell death events in the divisional context in order to understand the mechanisms of lineage commitment. [source] | |||||||||||||