Multivariate Copula Models at Work: Outperforming the desert island copula?

Since the pioneering work of Embrechts and co-authors in 1999, copula models enjoy steadily increasing popularity in finance. Whereas copulas are well-studied in the bivariate case, the higher-dimensional case still offers several open issues and it is by far not clear how to construct copulas which sufficiently capture the characteristics of financial returns. For this reason, elliptical copulas (i.e. Gaussian and Student-t copula) still dominate both empirical and practical applications. On the other hand, several attractive construction schemes appeared in the recent literature prom sing flexible but still manageable dependence models. The aim of this work is to empirically investigate whether these models are really capable to outperform its benchmark, i.e. the Student-t copula (which is termed by Paul Embrechts as "desert island copula" on account of its excellent fit to financial returns) and, in addition, to compare the fit of these different copula classes among themselves. --KS-copula,Hierarchical Archimedian,Product copulas,Pair-copula decomposition

Schultypus, Schulstress und Gesundheitsstörungen bei 17jährigen Zürcher Mittelschülerinnen und-schülern

Zusammenfassung: Eine Stichprobe von 661 siebzehnjährigen Schülerlnnen der 4. und 5. Klassenstufe verschiedener Mittelschulen des Kantons Zürich wurde mittels Fragebogen zu psychosozialen Merkmalen, Konsumverhalten, Schulsituation und ihrer physischen und psychischen Gesundheit befragt. Ziel der Studie war es zu klären, ob sich Schülerlnnen verschiedener Schultypen hinsichtlich ihrer psychosozialen und Morbiditätsmerkmale unterscheiden. Aus der Stichprobe wurden zwei Untergruppen gebildet: Schülerlnnen der traditionellen Gymnasialtypen B (alt-neusprachlich) und C (mathematisch-naturwissenschaftlich) einerseits und Schülerlnnen der modernen Gymnassialtypen D (neusprachlich) und L (neusprachlich-musisch) andererseits. Bezüglich soziodemographischer und familialer Merkmale sowie ihren sozialen Kontakten zeigten sich für beide Geschlechter keine Unterschiede zwischen den Typengruppen. Beim Konsumverhalten äusserten mehr Mädchen der modernen Gymnasialtypen, regelmässig Alkohol zu trinken. Ein deutlicher Typenunterschied zeigte sich in der Einschätzung des Essverhaltens, der Körperwahrenhmung, sowie physischer und psychischer Beschwerden. Schülerinnen der modernen Gymnasialtypen gaben in allen Bereichen mehr Störungen und Symptome an. Ungeachtet des Schultyps fanden sich bei den Probandinnen Zusammenhänge zwischen objektiv erreichten Schulleistungen bzw. subjektiv erlebtem Schulstress und physischer und psychischer Morbidität. Die Ergebnisse der Studie weisen darauf hin, dass vor allem für Schulklassen der modernen Gymnasialtypen gezielte Konzepte zur Prävention und Gesundheitsförderung entwickelt werden sollte

Floating solar panel park

Treball desenvolupat dins el marc del programa 'European Project Semester'.This Final Report is the culmination of a four month long design study on floating solar panel park feasibility in Vaasa, Finland. The Floating Ideas Team was tasked with coming up with a design that would not only work, but also make a profit. The team focused a lot of time on initial research, an iterative design process, and experiments to gather information that could not be found during the research phase. In this report, one can expect to find the major findings from research in many different areas such as location, panel design, flotation design, cooling techniques, and efficiency adding techniques. The first takeaway is that implementing floating solar parks in Finland would require adding efficiency techniques such as mirrors or concentrators. Second, how the panels are placed means a lot in a location so far north. Placing the panels far away from each other and horizontally will reduce the negative impact of shadows. And third, the rotation of the structure is important in increasing efficiency. Multiple axis tracking is not necessary, but tracking in the vertical axis can add a 50% increase in power generated. This research then lead into the defining of four initial designs which were eventually paired down into one. The largest factors leading to the change in design were the combination of rotation and anchoring methods, the flotation structure, and the structure required hold the panel modules together. In the end, the final design is a modular circular design with panels and mirrors to help add efficiency, approximately 37%. From there, an economic and environmental feasibility study was done and for both, this design was deemed feasible for Finland. With the design, detailed in this report, it would be possible to implement this and make a profit off of it, leading the team to believe that this should be implemented in places looking for alternatives for renewable energy production

Criteria of progress for information systems design theories

According to Kuhn, science and progress are strongly interrelated. In this paper, we define criteria of progress for design theories. A broad analysis of the literature on information systems design science reveals that there is no consensus on the criteria of progress for design theories. We therefore analyze different concepts of progress for natural science theories. Based on well-founded criteria stemming from the philosophy of science and referring to natural science theories, we develop a set of criteria of progress for design theories. In summary, our analysis results in six criteria of progress for design theories: A design theory is partially progressive compared to another if it is ceteris paribus (1) more useful, (2) internally more consistent, (3) externally more consistent, (4) more general, (5) simpler, or (6) more fruitful of further research. Although the measurement of these criteria is not the focus of this paper, the problem of measurement cannot be totally neglected. We therefore discuss different methods for measuring the criteria based on different concepts of truth: the correspondence theory of truth, the coherence theory of truth, and the consensus theory of truth. We finally show the applicability of the criteria with an exampl

A Model for Genome Size Evolution

International audienceWe present a model for genome size evolution that takes into account both local mutations such as small insertions and small deletions, and large chromosomal rearrangements such as duplications and large deletions. We introduce the possibility of undergoing several mutations within one generation. The model, albeit minimalist, reveals a non-trivial spontaneous dynamics of genome size: in the absence of selection, an arbitrary large part of genomes remains beneath a finite size, even for a duplication rate 2.6-fold higher than the rate of large deletions, and even if there is also a systematic bias toward small insertions compared to small deletions. Specifically, we show that the condition of existence of an asymptotic stationary distribution for genome size non-trivially depends on the rates and mean sizes of the different mutation types. We also give upper bounds for the median and other quantiles of the genome size distribution, and argue that these bounds cannot be overcome by selection. Taken together, our results show that the spontaneous dynamics of genome size naturally prevents it from growing infinitely, even in cases where intuition would suggest an infinite growth. Using quantitative numerical examples, we show that, in practice, a shrinkage bias appears very quickly in genomes undergoing mutation accumulation, even though DNA gains and losses appear to be perfectly symmetrical at first sight. We discuss this spontaneous dynamics in the light of the other evolutionary forces 123 2250 S. Fischer et al. proposed in the literature and argue that it provides them a stability-related size limit below which they can act

A tail quantile approximation formula for the student t and the symmetric generalized hyperbolic distribution

Calculating a large number of tail probabilities or tail quantiles for a given distribution families becomes very challenging, if both the cumulative and the inverse distribution function are not available in closed form. In case of the Gaussian and Student t distribution, quantile approximations are already available. This is not the case for the (symmetric) generalized hyperbolic distribution (GHD) whose popularity steadily increases and which includes both Gaussian and Student t as limiting case. Within this paper we close this gap and derive one possible tail approximation formula for the GHD as well as for the Student t distribution

Strongly Enhanced Thermal Stability of Crystalline Organic Thin Films Induced by Aluminum Oxide Capping Layers

We show that the thermal stability of thin films of the organic semiconductor diindenoperylene (DIP) can be strongly enhanced by aluminum oxide capping layers. By thermal desorption spectroscopy and in-situ X-ray diffraction we demonstrate that organic films do not only stay on the substrate, but even remain crystalline up to 460C, i.e. 270 deg. above their desorption point for uncapped films (190C). We argue that this strong enhancement of the thermal stability compared to uncapped and also metal-capped organic layers is related to the very weak diffusion of aluminum oxide and the structurally well-defined as-grown interfaces. We discuss possible mechanisms for the eventual breakdown at high temperatures.Comment: 5 pages, 4 figures, submitted to Adv. Mat., for further information see http://www.physchem.ox.ac.uk/~f

The Relationship between Personality Organization and Psychiatric Classification in Chronic Pain Patients

The assessment of PO is a crucial issue for diagnosis and treatment planning in CPPs, since it represents a measure of structural impairment that is to a considerable extent independent of axis I and II diagnoses. Moreover, the STIPO dimensional rating focuses on the most salient dysfunctions at a given time. Copyright (C) 2010 S. Karger AG, BaselBackground: The present study investigated the relationship between psychiatric classification and personality organization (PO) in a secondary/tertiary clinical sample of chronic pain patients (CPPs). Sampling and Methods: Forty-three patients were administered the Structured Clinical Interview for DSM-IV (SCID I+II) and the Structured Interview of Personality Organization (STIPO). The prevalence of axis I and axis II disorders was correlated with the STIPO level of PO. The STIPO dimensional ratings of patients without personality disorder (PD) were compared to those of patients diagnosed with one or more PDs. Results: Axis I comorbidity was high (93%), and 63% of the patients met the criteria for at least one axis II diagnosis. Twenty-five patients (58%) were diagnosed as borderline PO, with high-level impairments in the dimensions `coping/rigidity', `primitive defenses' and `identity'. Higher axis I and axis II comorbidity corresponded with greater severity of PO impairment. No difference was found between the dimensional ratings of patients without PD and those of patients with one or more PDs. Conclusions