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  • Author: Sebastian Fuchs x
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Abstract

We study the integration of a copula with respect to the probability measure generated by another copula. To this end, we consider the map [. , .] : C × C → R given by

where C denotes the collection of all d–dimensional copulas and QD denotes the probability measures associated with the copula D. Specifically, this is of interest since several measures of concordance such as Kendall’s tau, Spearman’s rho and Gini’s gamma can be expressed in terms of the map [. , .]. Quite generally, the map [. , .] can be applied to construct and investigate measures of concordance.

Abstract

We study measures of concordance for multivariate copulas and copulas that induce measures of concordance. To this end, for a copula A, we consider the maps C → R given by

where C denotes the collection of all d–dimensional copulas, M is the Fréchet–Hoeffding upper bound, Π is the product copula, [. , .] : C × C → R is the biconvex form given by [C, D] := ∫ [0,1]d C(u) dQD(u) with the probability measure QD associated with the copula D, and ψΛ C → C is a transformation of copulas. We present conditions on ψΛ and on A under which these maps are measures of concordance. The resulting class of measures of concordance is rich and includes the well–known examples Spearman’s rho and Gini’s gamma.

Abstract

By dealing with the process of othering in the context of acquisitions, this paper seeks to expand the concept of othering to Economic Geography. It argues that multinational companies should not only be viewed as victims of othering in that they suffer from obstructive policies and hostile public opinion, but rather that othering also matters within such firms. As a consequence of the links they establish between different countries, employees in such companies are constantly confronted with various socio-cultural backgrounds and frequently develop rather different expectations of how their counterparts should perform. This contribution analyses how and why managers and works councils in Germany practice distancing or othering towards owners of German firms located in China and India. It shows that othering can be critical within foreign direct investments. We approach the issue of othering by focusing on the sense of superiority of the involved parties, their positions in the company organisation and their related professional ethics, as well as the dynamics of othering that are mobilised in critical situations. The analysis is based on qualitative interviews from two different research projects.

Abstract

Higher serum neopterin concentrations and kynurenine-to-tryptophan (Kyn/Trp) ratios are associated with increased mortality in patients with coronary artery disease (CAD). Preferentially, Th1-type cytokine interferon-γ stimulates tryptophan breakdown and neopterin production by GTP cyclohydrolase I (GCH-I) in parallel in monocyte-derived macrophages and dendritic cells. In other cells, activation of GCH-I leads to the formation of 5,6,7,8-tetrahydrobiopterin (BH4), the necessary cofactor of amino acid hydroxylases such as phenylalanine 4-hydroxylase (PAH) and nitric oxide synthases. In 31 CAD patients (70.3±9.9 years; 21 males, 10 females), we determined serum concentrations of phenylalanine, tyrosine, and Kyn/Trp by HPLC, neopterin by ELISA, and nitrite by the colorimetric Griess assay. The phenylalanine-to-tyrosine ratio (Phe/Tyr) served as an estimate of PAH enzyme activity. Elevated Phe/Tyr concentrations were detected in a subgroup of CAD patients and correlated with Kyn/Trp (r=0.396, p<0.05) and neopterin (r=0.354, p<0.05) and inversely with nitrite (r=–0.371, p<0.05) concentrations. Higher Phe/Tyr in patients is associated with immune activation and indicates subnormal PAH activity that might be involved in the precipitation of neuropsychiatric symptoms in CAD patients.

Abstract

Úbeda-Flores showed that the range of multivariate Spearman’s footrule for copulas of dimension d ≥ 2 is contained in the interval [−1/d, 1], that the upper bound is attained exclusively by the upper Fréchet-Hoeffding bound, and that the lower bound is sharp in the case where d = 2. The present paper provides characterizations of the copulas attaining the lower bound of multivariate Spearman’s footrule in terms of the copula measure but also via the copula’s diagonal section.

Abstract

This study presents test measurements on a Lexsyg luminescence reader, acquired by the Giessen luminescence group. The reader is of the type Standard, hence designed for routine determination of palaeodoses using quartz or K-feldspars. The tests include measurements of the stimulation powers, preheat temperatures, OSL- and TL-curves, as well as dose recovery tests and calibration measurements using highly sensitised calibration quartz. A comparison of D e values determined using a Lexsyg reader with single grain D e-values, which have been previously obtained on a Risø reader, is also presented. The results imply that the Lexsyg reader is a highly reliable measurement device with high reproducibility, yielding instrumental uncertainties of around 0.3%.

Abstract

In vitro, large amounts of neopterin are released from human monocyte-derived macrophages and dendritic cells primarily upon stimulation with Th1-type cytokine interferon-γ (IFN-γ). IFN-γ also induces the enzyme indoleamine 2,3-dioxygenase (IDO), which degrades tryptophan (TRP) to form kynurenine (KYN). IDO-mediated TRP catabolism is very effective in suppressing the proliferation of T lymphocytes as well as of pathogens in vitro and in vivo. In this study, we investigated whether exogenously added neopterin may influence IDO activity in resting and in stimulated peripheral blood mononuclear cells (PBMC). PBMC were isolated from healthy donors, and neopterin was added in a concentration range from 0.01 to 50 μmol/L. After 30 min, PBMC were stimulated or not with 10 μg/mL of mitogen phytohemagglutinin (PHA). After 48 h, culture supernatants were collected, KYN and TRP concentrations were measured by high-performance liquid chromatography, and the ratio of KYN vs. TRP was calculated as an estimate of IDO activity. Spontaneous as well as PHA-induced TRP breakdown was suppressed by exogenously added neopterin in a dose-dependent way; the lowest active concentration of neopterin was <100 nmol/L. As neopterin concentrations in the nanomolar range are commonly observed in patients suffering from infections, sepsis, or uremia, our results suggest that neopterin formation might also serve as a feedback mechanism to slow down TRP degradation in vivo.

Zusammenfassung

Der zunehmende Ausbau regenerativer Energieumwandlungsanlagen im elektrischen Energieversorgungssystem führt zu einer Verringerung der residualen Last und damit zu einer Verdrängung konventioneller Großkraftwerke. Neben der Aufgabe, Leistung im Lastfolgebetrieb auf Basis von Fahrplänen bereitzustellen, übernehmen diese Kraftwerke bislang die kritische Aufgabe der Frequenz- und Spannungsregelung im Stromnetz. Bei einem Ersatz der Kraftwerke durch dezentrale dargebotsabhängige Erzeugungsanlagen müssen diese in der Lage sein, die Frequenz- und Spannungsregelung zu übernehmen. In diesem Beitrag wird ein Verfahren vorgestellt, mit denen sich Verbünde solcher Anlagen zur zuverlässigen Bereitstellung von Primärregelleistung heranziehen lassen.

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