• Publicationsclose
• Other research productsclose
• Research close
• DE close
• EU close
• English close

Plateau bursting is typical of many electrically excitable cells, such as endocrine cells that secrete hormones and some types of neurons that secrete neurotransmitters. Although in many of these cell types the bursting patterns are regulated by the interplay between voltage-gated calcium channels and calcium-sensitive potassium channels, they can be very different. For example, in insulin-secreting pancreatic β-cells, plateau bursting is characterized by well-defined spikes during the depolarized phase whereas in pituitary cells, bursting features fast, irregular, small amplitude spikes. The latter has been termed “pseudo-plateau bursting” because the spikes are transients around a depolarized steady state rather than stable oscillations in the fast subsystem. In this study we systematically investigate the bursting patterns found in endocrine cell models. We show that this class of voltage and calcium gated conductance based models can be reduced to the polynomial model of Hindmarsh and Rose (25). This reduction preserves the main properties of the biophysical class of models that we consider and allows for detailed bifurcation analysis of the full fast-slow system. Our analysis does not require decomposition of the full system into fast and slow subsystems and reveals properties of endocrine bursting that are not captured by the standard fast-slow analysis.

Soziale Konsequenzen anhaltend hoher Inflation in Argentinien, Bolivien und Brasilien. - Augsburg : Inst. für Spanien- u. Lateinamerikastudien, 1987. - 54 S. - (Mesa redonda ; 5)

Using comprehensive data for West Germany, this paper investigates the determinants of establishment exit. We find that between 1975 and 2006 the average exit rate has risen considerably. In order to test various 'liabilities' of establishment survival identified in the literature, we analyze the impact of establishment size and put a special focus on differences between young and mature establishments. Our empirical analysis shows that the mortality risk falls with establishment size, which confirms the liability of smallness. The probability of exit is substantially higher for young establishments which are not more than five years old, thus confirming the liability of newness. There also exists a liability of aging since exit rates first decline over time, reaching a minimum at ages 15 to 18, and then rise again somewhat. The determinants of exit differ substantially between young and mature establishments, suggesting that young establishments are more vulnerable in a number of ways. Mit umfangreichen Daten für Westdeutschland untersucht diese Studie die Einflussfaktoren von Betriebsschließungen. Es zeigt sich, dass die durchschnittliche Schließungsrate der Betriebe von 1975 bis 2006 deutlich gestiegen ist. Um verschiedene in der Literatur herausgearbeitete Anfälligkeiten zu überprüfen, analysieren wir den Einfluss der Betriebsgröße sowie Unterschiede zwischen jungen und älteren Betrieben. Die empirische Analyse zeigt, dass das Sterberisiko mit der Betriebsgröße abnimmt, was die 'liability of smallness' bestätigt. Entsprechend der 'liability of newness' ist die Schließungswahrscheinlichkeit deutlich höher für jüngere Betriebe, die maximal fünf Jahre alt sind. Ferner findet sich eine 'liability of aging', da die Schließungswahrscheinlichkeit zunächst mit dem Alter abnimmt, ihr Minimum zwischen 15 und 18 Jahren erreicht und danach wieder etwas zunimmt. Die Einflussfaktoren der Betriebsschließungen unterscheiden sich deutlich zwischen jungen und älteren Betrieben, wobei junge Betriebe in verschiedener Weise gefährdeter sind.

Ordinary linear and generalized linear regression models relate the mean of a response variable to a linear combination of covariate effects and, as a consequence, focus on average properties of the response. Analyzing childhood malnutrition in developing or transition countries based on such a regression model implies that the estimated effects describe the average nutritional status. However, it is of even larger interest to analyze quantiles of the response distribution such as the 5% or 10% quantile that relate to the risk of children for extreme malnutrition. In this paper, we analyze data on childhood malnutrition collected in the 2005/2006 India Demographic and Health Survey based on a semiparametric extension of quantile regression models where nonlinear effects are included in the model equation, leading to additive quantile regression. The variable selection and model choice problems associated with estimating an additive quantile regression model are addressed by a novel boosting approach. Based on this rather general class of statistical learning procedures for empirical risk minimization, we develop, evaluate and apply a boosting algorithm for quantile regression. Our proposal allows for data-driven determination of the amount of smoothness required for the nonlinear effects and combines model selection with an automatic variable selection property. The results of our empirical evaluation suggest that boosting is an appropriate tool for estimation in linear and additive quantile regression models and helps to identify yet unknown risk factors for childhood malnutrition.

An important puzzle in corporate taxation is that effective tax rates have fallen significantly while tax revenue has simultaneously risen in most countries. Moreover, the gross profitability of firms seems to be lower in high-tax countries, even though standard models of international investment would yield the opposite conclusion. We offer an explanation for these stylized facts by setting up a simple two-country model of tax competition with heterogeneous firms. In this model a unique, asymmetric Nash equilibrium can be shown to exist, provided that countries are sufficiently different with respect to their exogenous market conditions. In equilibrium the larger country levies the higher tax rate and attracts the high-cost firms. A simultaneous expansion of both markets intensifies tax competition and causes both countries to reduce their tax rates, despite higher corporate tax bases.

This paper documents multivariate forecast disagreement among professional forecasters of the Euro area economy and discusses implications for models of heterogeneous expectation formation. Disagreement varies over time and is strongly counter-cyclical. Disagreement is positively correlated with general (economic) uncertainty. Aggregate supply shocks drive disagreement about the long-run state of the economy while aggregate demand shocks have an impact on the level of disagreement about the short-run outlook for the economy. Forecasters disagree about the structure of the economy and the degree to which individual forecasters disagree with the average forecast tends to persist over time. This suggests that models of heterogeneous expectation formation, which are currently not able to generate those last two features, need to be modified. Introducing learning mechanisms and heterogeneous signal-to-noise ratios could reconcile the benchmark model for disagreement with the observed facts.

In contrast to conventional model selection criteria, the Focused Information Criterion (FIC) allows for the purpose-specific choice of model specifications. This accommodates the idea that one kind of model might be highly appropriate for inferences on a particular focus parameter, but not for another. Using the FIC concept that is developed by BEHL, CLAESKENS and DETTE (2014) for quantile regression analysis, and the estimation of the rebound effect in individual mobility behavior as an example, this paper provides for an empirical application of the FIC in the selection of quantile regression models. Discussion Paper / SFB823;39, 2016

In the present monograph, we will deal with questions of lexical typology in the nominal domain. By the term "lexical typology in the nominal domain", we refer to crosslinguistic regularities in the interaction between (a) those areas of the lexicon whose elements are capable of being used in the construction of "referring phrases" or "terms" and (b) the grammatical patterns in which these elements are involved. In the traditional analyses of a language such as English, such phrases are called "nominal phrases". In the study of the lexical aspects of the relevant domain, however, we will not confine ourselves to the investigation of "nouns" and "pronouns" but intend to take into consideration all those parts of speech which systematically alternate with nouns, either as heads or as modifiers of nominal phrases. In particular, this holds true for adjectives both in English and in other Standard European Languages. It is well known that adjectives are often difficult to distinguish from nouns, or that elements with an overt adjectival marker are used interchangeably with nouns, especially in particular semantic fields such as those denoting MATERIALS or NATlONALlTIES. That is, throughout this work the expression "lexical typology in the nominal domain" should not be interpreted as "a typology of nouns", but, rather, as the cross-linguistic investigation of lexical areas constitutive for "referring phrases" irrespective of how the parts-of-speech system in a specific language is defined.

AbstractThis note documents Aumann's reason for omitting the “empty shells” argument for the common prior assumption from the final version of “Correlated Equilibrium as an Expression of Bayesian Rationality.” It then continues to discuss the argument and concludes that rational entities cannot learn their own identity; if they do not know it a priori, they never will.