Pooling und Tranching im Rahmen von ABS-Transaktionen

In recent years the market for asset backed securities (ABS) has shown a rapid growth. In an ABS transaction assets are first pooled and then securities backed by this pool are issued. In many cases, several tranches of securities differing with respect to their priority of payment are designed. The rapid development of the ABS market cannot be explained under the assumption of a perfect capital market since in such case the structuring of cash flows cannot lead to any value creation. Several explanatory approaches based on the different market imperfections have since been developed. Discussing current available literature the following article presents the sophisticated approach of DeMarzo (2005). The author shows, under the assumption of an asymmetric information distribution between the market participants, that in such case bundling of assets and structuring of tranches with different priorities of payment could be value-creating.In den vergangenen Jahren verzeichnete der Markt für Asset Backed Securities (ABS) ein rasantes Wachstum. Im Rahmen einer ABS-Transaktion werden Forderungen in einem Pool gebündelt und Wertpapiere emittiert, die mit diesem Forderungspool unterlegt sind. Häufig werden mehrere Wertpapiertranchen strukturiert, die sich in der Rangfolge der Bedienung unterschieden. Unter der Annahme eines vollkommenen Kapitalmarktes, lässt sich die rasante Entwicklung des ABS-Marktes nicht erklären, da in diesem Fall kein Wert durch die Strukturierung von Zahlungsströmen geschaffen werden kann. In der Literatur wurden verschiedene ökonomische Erklärungsansätze entwickelt, die von den unterschiedlichen Marktunvollkommenheiten ausgehen. Im folgenden Beitrag wird vor dem Hintergrund eines Literaturüberblicks der fortgeschrittene Ansatz von DeMarzo (2005) vorgestellt, der unter der Annahme einer asymmetrischen Informationsverteilung zwischen den verschiedenen Marktteilnehmern untersucht, in welchen Fällen die Bündelung von Forderungen und die Strukturierung von Wertpapiertranchen unterschiedlicher Priorität für den Emittenten wertschaffend sein kann

Pooling und Tranching im Rahmen von ABS-Transaktionen

In recent years the market for asset backed securities (ABS) has shown a rapid growth. In an ABS transaction assets are first pooled and then securities backed by this pool are issued. In many cases, several tranches of securities differing with respect to their priority of payment are designed. The rapid development of the ABS market cannot be explained under the assumption of a perfect capital market since in such case the structuring of cash flows cannot lead to any value creation. Several explanatory approaches based on the different market imperfections have since been developed. Discussing current available literature the following article presents the sophisticated approach of DeMarzo (2005). The author shows, under the assumption of an asymmetric information distribution between the market participants, that in such case bundling of assets and structuring of tranches with different priorities of payment could be value-creating.In den vergangenen Jahren verzeichnete der Markt für Asset Backed Securities (ABS) ein rasantes Wachstum. Im Rahmen einer ABS-Transaktion werden Forderungen in einem Pool gebündelt und Wertpapiere emittiert, die mit diesem Forderungspool unterlegt sind. Häufig werden mehrere Wertpapiertranchen strukturiert, die sich in der Rangfolge der Bedienung unterschieden. Unter der Annahme eines vollkommenen Kapitalmarktes, lässt sich die rasante Entwicklung des ABS-Marktes nicht erklären, da in diesem Fall kein Wert durch die Strukturierung von Zahlungsströmen geschaffen werden kann. In der Literatur wurden verschiedene ökonomische Erklärungsansätze entwickelt, die von den unterschiedlichen Marktunvollkommenheiten ausgehen. Im folgenden Beitrag wird vor dem Hintergrund eines Literaturüberblicks der fortgeschrittene Ansatz von DeMarzo (2005) vorgestellt, der unter der Annahme einer asymmetrischen Informationsverteilung zwischen den verschiedenen Marktteilnehmern untersucht, in welchen Fällen die Bündelung von Forderungen und die Strukturierung von Wertpapiertranchen unterschiedlicher Priorität für den Emittenten wertschaffend sein kann.asset backed securities; collateralized debt obligation; security design; pooling; tranching; asymmetric information; adverse selection; lemons problemAsset Backed Securities; Collateralized Debt Obligation; Security Design; Pooling; Tranching; asymmetrische Informationsverteilung; adverses Selektionsproblem; Lemons-Problem

Characterizing synaptic conductance fluctuations in cortical neurons and their influence on spike generation

Cortical neurons are subject to sustained and irregular synaptic activity which causes important fluctuations of the membrane potential (Vm). We review here different methods to characterize this activity and its impact on spike generation. The simplified, fluctuating point-conductance model of synaptic activity provides the starting point of a variety of methods for the analysis of intracellular Vm recordings. In this model, the synaptic excitatory and inhibitory conductances are described by Gaussian-distributed stochastic variables, or colored conductance noise. The matching of experimentally recorded Vm distributions to an invertible theoretical expression derived from the model allows the extraction of parameters characterizing the synaptic conductance distributions. This analysis can be complemented by the matching of experimental Vm power spectral densities (PSDs) to a theoretical template, even though the unexpected scaling properties of experimental PSDs limit the precision of this latter approach. Building on this stochastic characterization of synaptic activity, we also propose methods to qualitatively and quantitatively evaluate spike-triggered averages of synaptic time-courses preceding spikes. This analysis points to an essential role for synaptic conductance variance in determining spike times. The presented methods are evaluated using controlled conductance injection in cortical neurons in vitro with the dynamic-clamp technique. We review their applications to the analysis of in vivo intracellular recordings in cat association cortex, which suggest a predominant role for inhibition in determining both sub- and supra-threshold dynamics of cortical neurons embedded in active networks.Comment: 9 figures, Journal of Neuroscience Methods (in press, 2008

Noxic effects of polystyrene microparticles on murine macrophages and epithelial cells

Abstract Microplastic (MP) contamination has been identified as an ecological problem with an increasing impact on everyday life. Yet, possible effects of MP at the cellular level are still poorly understood. Here, the interaction of murine macrophages (J774A.1, ImKC) and epithelial cells (STC-1, BNL CL.2) with well-characterized poly(styrene) MP particles (MPP) of varying sizes (0.2–6.0 µm) was studied. Macrophages are expected to actively engulf particles which could be confirmed in this study, while epithelial cells are found in tissues with direct contact with ingested or inhaled MPP. Here, the epithelial cells from both investigated cell lines did not ingest MPP in significant numbers. Concomitantly, no cytotoxic effects nor any influence on cellular proliferation were observed. Cells from the two macrophage cell lines showed high ingestion of MPP of all sizes, but cytotoxic effects were observed only for one of them (ImKC) and only at MPP concentrations above 250 µg/mL. Indications of cellular stress as well as effects on cell proliferation were observed for cell populations with high particle cell interactions

Reviewing the focus: a summary and critique of child-focused sexual abuse prevention

Due to the high incidence, and widespread detrimental health consequences, of child sexual abuse (CSA), effective prevention remains at the forefront of public and mental health research, prevention and intervention agendas. To date much of the focus of prevention has been on school-based education programs designed to teach children skills to evade adult sexual advances, and disclose past or ongoing abuse. Evaluation of sexual abuse prevention programs demonstrate their effectiveness in increasing children’s knowledge of CSA concepts and protection skills, but little is known about their effects on children’s capacity to prevent abuse. Moreover, concerns persist about the unintended side-effects for young children such as anxiety, worry and wariness of touch. This paper summarizes the recent history of CSA prevention and the critique of child-focused protection programs in order to demonstrate the need to compliment or replace these programs by focusing more on protectors in the children’s ecology, specifically parents, in order to create safer environments in which abuse is less likely to occur

Parent relationships and adolescents' depression and social anxiety: indirect associations via emotional sensitivity to rejection threat

One prominent theory has proposed that rejection and other negative parenting practices prompt children's emotional sensitivity to the threat of rejection, often referred to as rejection sensitivity (RS). This emotional sensitivity is thought to result in social and emotional maladjustment. In the present study, we tested this model of parenting, emotional sensitivity, and maladjustment with 659 early adolescents (aged 9–13 years). The findings confirmed that adolescents who reported more negative parenting practices had elevated depression and social anxiety symptoms, heightened levels of RS, and more elevated sadness and withdrawal responses to rejection threat. In a final structural equation model, RS and withdrawal were uniquely associated with depressive symptoms, and RS, sadness, and withdrawal were uniquely associated with social anxiety. Moreover, negative parenting had significant associations with symptoms both directly and indirectly via RS, sadness, and/or withdrawal, with the effects mostly direct for depressive symptoms and mostly indirect for social anxiety symptoms. Interparental conflict was also implicated in adolescents' RS, reactions to rejection threat, and symptoms, but these correlational effects were almost entirely indirect via parenting practices. An alternate model of depression and anxiety predicting sensitivity to rejection threat was tested and found to be equally viable. The findings provide a more nuanced understanding of the links between rejection and adolescent emotional adjustment

On the Relation of Entropy and Enthalpy of Fusion in Triglycerides

This contribution presents an extensive literature survey of the calorimetric properties, namely enthalpy and entropy of fusion, of alkyl‐based molecules. Building on the well‐known linear correlation of the named properties to the carbon number in n‐alkanes, saturated fatty acids (FA), and saturated monoacid triglycerides (TAGs), the calorimetric properties of TAGs are reviewed. No straightforward correlation using a single ordering parameter, i.e., carbon number, can be derived for TAGs. This is not surprising due to the complexity of this particular class of molecules differing in alkyl‐chain distribution over the glycerol backbone and chain saturation. A linear correlation of enthalpy and entropy of fusion is evident for molecule classes for which both properties correlate linearly with the carbon number, e.g., n‐alkanes. Despite the complexity of TAGs, it is possible to establish a linear correlation between enthalpy and entropy of fusion even though no underlying single ordering parameter can be identified. A linear fit reveals discrepancies between saturated and unsaturated molecules but independence of polymorphic forms and chain length differences in mixed‐acid TAGs. Moreover, the slopes of the linear fits for data on n‐alkanes, saturated FA, and saturated mono‐acid TAGs are found to be in the vicinity of the melting temperature of polyethylene

Vitamin B12 in Leber hereditary optic neuropathy mutation carriers: a prospective cohort study

Background Leber hereditary optic neuropathy (LHON) is the most common mitochondrial disorder, frequently resulting in acute or subacute severe bilateral central vision loss. Vitamin B12 deficiency is also a known cause of optic neuropathy through mitochondrial dysfunction. Here we evaluated the prevalence and clinical significance of vitamin B12 deficiency in a large cohort of LHON patients and asymptomatic mutation carriers from a tertiary referral center. Methods From the Munich LHON prospective cohort study, participants included all LHON patients and asymptomatic LHON mutation carriers, who were recruited between February 2014 and March 2020 and consented to participate. Neurological, general, and ophthalmological examinations were regularly performed, as were laboratory tests. Vitamin B12 deficiency was diagnosed if serum vitamin B12 was below 201 pg/mL, or if 201–339 pg/mL plus low serum holotranscobalamin or elevated serum methylmalonic acid or elevated total plasma homocysteine. Results We analyzed 244 subjects, including 147 symptomatic LHON patients (74% males) and 97 asymptomatic mutation carriers (31% males). Median age at study baseline was 34 years (range 5–82 years). The prevalence of vitamin B12 deficiency was higher for LHON mutation carriers than for the general population in all age categories. This was statistically significant for the LHON mutation carriers under 65 years (21% vs. 5–7%, p = 0.002). While vitamin B12 deficiency prevalence was not statistically different between LHON patients and asymptomatic mutation carriers, its clinical correlates, e.g., macrocytosis and polyneuropathy, were more frequent in the subgroup of LHON patients. Excessive alcohol consumption was a significant predictor of vitamin B12 deficiency (p < 0.05). Conclusions The high prevalence of vitamin B12 deficiency in LHON mutation carriers, both asymptomatic mutation carriers and LHON patients, highlights the need for regular vitamin B12 screening in this population, in order to ensure early treatment, aiming for better outcomes. Our study is not conclusive regarding vitamin B12 deficiency as determinant for disease conversion in LHON, and further research is warranted to disentangle the role of vitamin B12 in the pathophysiology and prognosis of LHON