A model of collateral, investment and adverse selection

This paper characterizes the relationship between entrepreneurial wealth and aggregate investmentunder adverse selection. Its main finding is that such a relationship need not bemonotonic. In particular, three results emerge from the analysis: (i) pooling equilibria, in whichinvestment is independent of entrepreneurial wealth, are more likely to arise when entrepreneurialwealth is relatively low; (ii) separating equilibria, in which investment is increasing inentrepreneurial wealth, are most likely to arise when entrepreneurial wealth is relatively highand; (iii) for a given interest rate, an increase in entrepreneurial wealth may generate a discontinuousfall in investment.

Model selection and error estimation

We study model selection strategies based on penalized empirical loss minimization. We point out a tight relationship between error estimation and data-based complexity penalization: any good error estimate may be converted into a data-based penalty function and the performance of the estimate is governed by the quality of the error estimate. We consider several penalty functions, involving error estimates on independent test data, empirical {\sc vc} dimension, empirical {\sc vc} entropy, andmargin-based quantities. We also consider the maximal difference between the error on the first half of the training data and the second half, and the expected maximal discrepancy, a closely related capacity estimate that can be calculated by Monte Carlo integration. Maximal discrepancy penalty functions are appealing for pattern classification problems, since their computation is equivalent to empirical risk minimization over the training data with some labels flipped.

Distribución e indices de avistamientos de mamiferos marinos y su relación con la abundancia del Krill Euphasia Superba. Perú Antar IX

Un total de 41 avistamientos de mamíferos marinos se registraron en el Estrecho de Bransfield y alrededores de la Isla Elefante entre los 60,5° y 63° S y los 53,5 y 60° W, cubriendo 853,02 mn durante el Crucero de Evaluación de la Biomasa del Krill en la IX Expedición Peruana a la Antártida, desarrollada entre el 12 y 24 de enero de 1998. Dentro del orden Cetacea se registraron 33 ballenas jorobadas Megaptera novaeangliae, 2 ballenas minke Balaenoptera bonaerenses, 9 orcas Orcinus orca, 2 balaenoptéridos y un cetáceo mayor no identificado. Entre los registros del orden Pinnipedia figuran 21 lobos finos antárticos Arctocephalus gazella, 2 focas cangrejas Lobodon carcinophagus y una foca leopardo Hidrurga leptonix. La presencia de estos mamíferos marinos en las áreas con valores altos en la biomasa de krill, hace presumir que estarían cumpliendo actividades tróficas, constituyéndose en posibles indicadores de la existencia de concentraciones de este crustáceo en la región antártica.

Meropenem prevents levofloxacin-induced resistance in penicillin-resistant pneumococci and acts synergistically with levofloxacin in experimental meningitis.

The aim of the present study was to investigate the potential synergy between meropenem and levofloxacin in vitro and in experimental meningitis and to determine the effect of meropenem on levofloxacin-induced resistance in vitro. Meropenem increased the efficacy of levofloxacin against the penicillin-resistant pneumococcal strain KR4 in time-killing assays in vitro and acted synergistically against a second penicillin-resistant strain WB4. In the checkerboard, only an additive effect (FIC indices: 1.0) was observed for both strains. In cycling experiments in vitro, levofloxacin alone led to a 64-fold increase in the MIC for both strains after 12 cycles. Addition of meropenem in sub-MIC concentrations (0.25 x MIC) completely inhibited the selection of levofloxacin-resistant mutants in WB4 after 12 cycles. In KR4, the addition of meropenem led to just a twofold increase in the MIC for levofloxacin after 12 cycles. Mutations detected in the genes encoding for topoisomerase IV (parC) and gyrase (gyrA) confirmed the levofloxacin-induced resistance in both strains. Addition of meropenem was able to completely suppress levofloxacin-induced mutations in WB4 and led to only one mutation in parE in KR4. In experimental meningitis, meropenem, given in two doses (2 x 125 mg/kg), produced a good bactericidal activity (-0.45 Deltalog10 cfu/ml.h) comparable to one dose (1 x 10 mg/kg) of levofloxacin (-0.44 Deltalog10 cfu/ml.h) against the penicillin-resistant strain WB4. Meropenem combined with levofloxacin acted synergistically (-0.93 Deltalog10 cfu/ml.h), sterilizing the CSF of all rabbits.

Egg laying site selection by a host plant specialist leaf miner moth at two intra-plant levels in the northern Chilean Atacama Desert

Egg laying site selection by a host plant specialist leaf miner moth at two intra-plant levels in the northern Chilean Atacama Desert. The spatial distribution of the immature stages of the leaf miner Angelabella tecomae Vargas & Parra, 2005 was determined at two intra-plant levels (shoot and leaflet) on the shrub Tecoma fulva fulva (Cav.) D. Don (Bignoniaceae) in the Azapa valley, northern Chilean Atacama Desert. An aggregated spatial pattern was detected for all the immature stages along the shoot, with an age dependent relative position: eggs and first instar larvae were clumped at apex; second, third and fourth instar larvae were mostly found at intermediate positions; meanwhile the spinning larva and pupa were clumped at basis. This pattern suggests that the females select new, actively growing leaflets for egg laying. At the leaflet level, the immature stages were found more frequently at underside. Furthermore, survivorship was higher for larvae from underside mines. All these results highlight the importance of an accurate selection of egg laying site in the life history of this highly specialized leaf miner. By contrast, eventual wrong choices in the egg laying site selection may be associated with diminished larval survivorship. The importance of the continuous availability of new plant tissue in this highly human modified arid environment is discussed in relation with the observed patterns.

Revised NEO personality inventory normative data for catalan police officer selection: preliminary study

El Servei d'Avaluació, Seguiment i Selecció de l'ISPC han elaborat un estudi sobre el perfil de personalitat dels aspirants al Curs de Formació bàsica per policies, que es va presentar a l'International Society for the Study of Individual Differences Meeting celebrat al CosmoCaixa de Barcelona i que organitzen conjuntament l’Associació Iberoamericana per a la recerca de les diferències individuals i la Universitat de Barcelona. L’estudi, titulat Revised NEO Personality Inventory Normative Data for Catalan police officer selection: A preliminary study, té com a objectiu comparar els perfils de personalitat d’una mostra d’aspirants de l’ISPC amb els resultats d’una mostra d’aspirants a policia dels EUA, publicada en una revista científica de prestigi el mes de febrer passat. Els resultats mostren que els aspirants catalans destaquen per obtenir millors puntuacions en les dimensions de responsabilitat i amabilitat, cosa que indicaria que aquest tret es valora especialment durant el procés de selecció de la policia de Catalunya; en altres característiques de la personalitat les dues mostres obtenen resultats similars. Els trets característics del perfil del policia català seria el de persones estables emocionalment, poc impulsives, amb capacitat per gestionar l’estrés, orientades a les persones, agradables, sociables, responsables, disciplinades i cauteloses. Enllaç a: International Society for the Study of Individual Differences Meeting :http://www.issid.org/conferences/ISSID2013/ISSIDconference2013.html

Autoreactive T cells that bypass negative selection are not tolerant and respond to self-antigen stimulation during infection

Le répertoire cellulaire Τ a pour but d'être tolérant aux antigènes du soi afin d'éviter l'induction de maladies autoimmunes. C'est pourquoi les lymphocytes Τ autoréactifs sont éliminés dans le thymus lors de leur développement par le processus de sélection négative. La plupart des recherches étudient les lymphocytes Τ de haute avidité. Ces lymphocytes Τ de haute avidité sont très sensibles et réagissent fortement à un antigène du soi. En conséquence, ces cellules induisent le développement de maladies autoimmunes lorsqu'elles ciblent des organes exprimant l'antigène du soi. Plusieurs études ont montré que les lymphocytes Τ qui réagissent faiblement aux antigènes spécifiques à un tissu, nommé lymphocytes Τ de faible avidité, peuvent contourner les mécanismes de tolérance centrale et périphérique. J'ai utilisé des souris Rip-mOva qui expriment l'Ovalbumine comme antigène du soi spécifique à un tissu. Dans ces souris transgéniques Rip-mOva, les lymphocytes Τ de faible avidité survivent à la sélection négative. Une fois stimulés à la périphérie, ces lymphocytes Τ CD8+ de faible avidité ont la capacité d'infiltrer les organes qui expriment l'antigène du soi chez les souris Rip-mOva et peuvent induire une destruction tissulaire. L'objectif principal de mon projet de thèse était de comprendre les caractéristiques phénotypiques et fonctionnelles de ces lymphocytes Τ dans un état d'équilibre et dans un contexte infectieux. Pour étudier ces cellules dans un modèle murin bien défini, nous avons généré des souris exprimant un récepteur de cellule Τ transgénique appelé OT-3. Ces souris transgéniques OT-3 ont des lymphocytes Τ CD8+ de faible avidité spécifiques à l'épitope SIINFEKL de l'antigène Ovalbumine. Nous avons démontré qu'un grand nombre de lymphocytes Τ CD8+ OT-3 ne sont pas éliminés lors de la sélection négative dans le thymus après avoir rencontré l'antigène du soi. Par conséquent, les lymphocytes Τ OT-3 de faible avidité sont présents dans une fenêtre de sélection comprise entre la sélection positive et négative. Cette limite se définie comme le seuil d'affinité et est impliquée dans l'échappement de certains lymphocytes Τ OT- 3 autoréactifs. A la périphérie, ces cellules sont capables d'induire une autoimmunité après stimulation au cours d'une infection, ce qui nous permet de les définir comme étant non tolérante et non dans un état anergique à la périphérie. Nous avons également étudié le seuil d'activation des lymphocytes Τ OT-3 à faible avidité à la périphérie et avons constaté que des ligands peptidiques plus faibles que l'épitope natif SIINFEKL sont capables de les activer au cours d'une infection ainsi que de les différencier en lymphocytes Τ effecteurs et mémoires. Les données illustrent une déficience lors de la sélection négative dans le thymus de lymphocytes Τ CD8+ autoréactifs de faible avidité contre un antigène du soi spécifique à tissu et montrent que ces cellules sont entièrement compétentes lors d'une infection. - The diverse Τ cell repertoire needs to be tolerant to self-antigen to avoid the induction of autoimmunity. This is why autoreactive developing Τ cells are deleted in the thymus. The deletion of self-reactive Τ cells occurs through the process of negative selection. Most studies investigated high avidity Τ cells. These high avidity Τ cells are very sensitive and strongly react to a self-antigen. As a consequence, these cells induce the development of autoimmunity when they target organs which express the self-antigen. High avidity autoreactive CD8+ Τ cells are deleted in the thymus. However, several studies have shown Τ cells that weakly respond to tissue-restricted antigen, referred to as low avidity Τ cells, can bypass central and peripheral tolerance mechanisms. I used Rip-mOva mice that expressed Ovalbumin as a neo self-antigen in a tissue-restricted fashion. In these transgenic Rip-mOva mice low avidity CD8+ Τ cells survive negative selection. Upon stimulation in the periphery, these low avidity CD8+ Τ cells have the ability to infiltrate organs that express the self-antigen in the Rip-mOva mice and can also induce the destruction of the tissue. The major aim of my PhD project was to understand the phenotypic and functionality characteristics of these Τ cells in a steady-state condition and in a context of an infection. To study these cells in a well-defined mouse model, we generated OT-3 Τ cell receptor transgenic mice that express low avidity CD8+ Τ cells that are specific for the SIINFEKL epitope of the Ovalbumin antigen. We have been able to demonstrate that a large number of OT-3 CD8+ Τ cells survive negative selection in the thymus after encountering the self-antigen. Thus, low avidity OT-3 Τ cells are present in a window of selection comprised between positive and negative selection. This boundary defined as the affinity threshold is involved in the escape of some autoreactive low avidity OT-3 Τ cells. Once they circulate in the periphery, they are able to induce autoimmunity after stimulation during an infection, allowing us to allocate these cells as being non-tolerant and not in an anergic state in the periphery. We have also looked at the threshold of activation of low avidity OT-3 CD8+ Τ cells in the periphery and found that peptide ligands that are weaker than the native SIINFEKL epitope are able to activate OT-3 Τ cells during an infection and to differentiate them into effector and memory Τ cells. The data illustrate the impairment of negatively selecting low avidity autoreactive CD8+ Τ cells against a tissue-restricted antigen in the thymus and shows that these cells are fully competent upon an infection.

Dissociation of thymic positive and negative selection in transgenic mice expressing major histocompatibility complex class I molecules exclusively on thymic cortical epithelial cells.

Thymic positive and negative selection of developing T lymphocytes confronts us with a paradox: How can a T-cell antigen receptor (TCR)-major histocompatibility complex (MHC)/peptide interaction in the former process lead to transduction of signals allowing for cell survival and in the latter induce programmed cell death or a hyporesponsive state known as anergy? One of the hypotheses put forward states that the outcome of a TCR-MHC/peptide interaction depends on the cell type presenting the selecting ligand to the developing thymocyte. Here we describe the development and lack of self-tolerance of CD8(+) T lymphocytes in transgenic mice expressing MHC class I molecules in the thymus exclusively on cortical epithelial cells. Despite the absence of MHC class I expression on professional antigen-presenting cells, normal numbers of CD8(+) cells were observed in the periphery. Upon specific activation, transgenic CD8(+) T cells efficiently lysed syngeneic MHC class I(+) targets in vitro and in vivo, indicating that thymic cortical epithelium (in contrast to medullary epithelium and antigen-presenting cells of hematopoietic origin) is incapable of tolerance induction. Thus, compartmentalization of the antigen-presenting cells involved in thymic positive selection and tolerance induction can (at least in part) explain the positive/negative selection paradox.

Multiscale determinants of tree frog (Hyla arborea L.) calling ponds in western Switzerland

A tree frog (Hyla arborea L., 1758) metapopulation in western Switzerland was studied during spring 2001. All potential calling ponds in an area of 350 km(2) were searched for tree frog calling males. Twenty-nine out of 111 ponds sheltered between 1 and 250 callers. Most ponds were occupied by less than 12 males. Pond parameters were measured at three different levels using field analysis and a Geographical Information System (GIS). The first level was water chemistry and pond-associated measures. The second level was the surrounding land use in a 30 m buffer around the pond. The third level consisted of landscape indices on a broader scale (up to 2 km). Logistic regression was applied to identify parameters that can predict the presence of calling males in a pond. Response variable was the presence or absence of callers. Four significant parameters allowed us to explain about 40% of the total deviance of the observed occupational pattern. Urbanization around the pond had a highly negative impact on the probability of presence of calling males. Hours of direct sunlight on the pond was positively correlated with callers. Higher water conductivity was associated with a lesser probability of species presence. Finally, the further the closest two-lane road, the higher the probability of callers presence. Our results show that presence or absence of callers is influenced by factors acting at various geographical scales.

Effect of multiple oral doses of androgenic anabolic steroids on endurance performance and serum indices of physical stress in healthy male subjects.

Anabolic androgenic steroids (AAS) are doping agents that are mostly used for improvement of strength and muscle hypertrophy. In some sports, athletes reported that the intake of AAS is associated with a better recovery, a higher training load capacity and therefore an increase in physical and mental performances. The purpose of this study was to evaluate, the effect of multiple doses of AAS on different physiological parameters that could indirectly relate the physical state of athletes during a hard endurance training program. In a double blind settings, three groups (n = 9, 8 and 8) were orally administered placebo, testosterone undecanoate or 19-norandrostenedione, 12 times during 1 month. Serum biomarkers (creatine kinase, ASAT and urea), serum hormone profiles (testosterone, cortisol and LH) and urinary catecholamines (noradrenalin, adrenalin and dopamine) were evaluated during the treatment. Running performance was assessed before and after the intervention phase by means of a standardized treadmill test. None of the measured biochemical variables showed significant impact of AAS on physical stress level. Data from exercise testing on submaximal and maximal level did not reveal any performance differences between the three groups or their response to the treatment. In the present study, no effect of multiple oral doses of AAS on endurance performance or bioserum recovery markers was found.

1st radiometric dating of a paleontologically dated Bathonian level from Georgia (USSR) - Use of the cathodoluminescence for selection of suitable plagioclases

Jurassic volcanic formations interlayered with (ammonite-bearing) sediments are common in the Caucasus area; this situation is of interest for the numerical calibration of the poorly documented Jurassic portion of the time scale. However, following petrographic study on thin sections no whole-rocks can be considered reliable geochronometers due to subsequent alteration; from about 20 samples, two were selected for plagioclase dating; one (V134) is probably early Kimmeridgian in age; the other (V136) is probably located in the Lower Bathonian stage according to diagnostic ammonites. Cathodoluminescence (CTL) study has shown that sample V136 was similar to usual volcanic feldspars (blue to green colour); however, the lack of CTL of the V134 plagioclase is a character common to diagenetic feldspars; consequently, in spite of a good optical preservation, this geo-chronometer cannot give an age representative of the time of emplacement of the lava flow. We have combined CTL observation with microprobe analysis in order to document the poorly known CTL behaviour of volcanic feldspars; cations Ti4+ and Fe2+ play a major role in the CTL colour of plagioclases and are able to document the growing history of these feldspars ; phenocrysts are initially rich in Fe2+ (core of the crystals, green in colour), then richer in Ti toward the exterior; microcrysts are even richer in Ti (blue to bright blue). We have also observed that natural CTL colour was modified resulting from acid ``cleaning'' of the separated feldspars : the initial blue or green colour tends to change to yellow or violet, respectively, after acid treatment probably due to oxydation of Fe2+ toward Fe3+. X-ray and microprobe analyses both indicated that plagioclases from sample V134 was near the sodic end member (albite) suggesting a diagenetic origin in this andesitic basalt; In contrast, sample V136 contains a calcic plagioclase of common composition for a doleritic basalt. The K-Ar conventional technique was applied as a preliminary tool for radiometric analysis. The Kimmeridgian Na-plagioclase sample gave a ``rejuvenated'' (85 Ma) apparent age which confirms a late genesis for the separated plagioclase phase; this interpretation is based on CTL observation, X-ray analysis, and microprobe analysis ; these techniques are able to distinguish samples which have been submitted to diagenetic alteration from those which have not. An age consistent with the stratigraphic location has been obtained from sample V136. This age of 161 +/- 3 (2-sigma) Ma, is the first one available from a sample palaeontologically located with reasonable precision within the mid Jurassic time.

TCR-alpha CDR3 loop audition regulates positive selection.

How positive selection molds the T cell repertoire has been difficult to examine. In this study, we use TCR-beta-transgenic mice in which MHC shapes TCR-alpha use. Differential AV segment use is directly related to the constraints placed on the composition of the CDR3 loops. Where these constraints are low, efficient selection of alphabeta pairs follows. This mode of selection preferentially uses favored AV-AJ rearrangements and promotes diversity. Increased constraint on the alpha CDR3 loops leads to inefficient selection associated with uncommon recombination events and limited diversity. Further, the two modes of selection favor alternate sets of AJ segments. We discuss the relevance of these findings to the imprint of self-MHC restriction and peripheral T cell activation.

EEG alpha activity reflects motor preparation rather than the mode of action selection

Alpha-band activity (8-13 Hz) is not only suppressed by sensory stimulation and movements, but also modulated by attention, working memory and mental tasks, and could be sensitive to higher motor control functions. The aim of the present study was to examine alpha oscillatory activity during the preparation of simple left or right finger movements, contrasting the external and internal mode of action selection. Three preparation conditions were examined using a precueing paradigm with S1 as the preparatory and S2 as the imperative cue: Full, laterality instructed by S1; Free, laterality freely selected and None, laterality instructed by S2. Time-frequency (TF) analysis was performed in the alpha frequency range during the S1-S2 interval, and alpha motor-related amplitude asymmetries (MRAA) were also calculated. The significant MRAA during the Full and Free conditions indicated effective external and internal motor response preparation. In the absence of specific motor preparation (None), a posterior alpha event-related desynchronization (ERD) dominated, reflecting the main engagement of attentional resources. In Full and Free motor preparation, posterior alpha ERD was accompanied by a midparietal alpha event-related synchronization (ERS), suggesting a concomitant inhibition of task-irrelevant visual activity. In both Full and Free motor preparation, analysis of alpha power according to MRAA amplitude revealed two types of functional activation patterns: (1) a motor alpha pattern, with predominantly midparietal alpha ERS and large MRAA corresponding to lateralized motor activation/visual inhibition and (2) an attentional alpha pattern, with dominating right posterior alpha ERD and small MRAA reflecting visuospatial attention. The present results suggest that alpha oscillatory patterns do not resolve the selection mode of action, but rather distinguish separate functional strategies of motor preparation.

Trends in indices of daily precipitation extremes in Catalonia (NE Spain), 1951-2003

The aim of this paper is to quantitatively characterize the climatology of daily precipitation indices in Catalonia (northeastern Iberian Peninsula) from 1951 to 2003. This work has been performed analyzing a subset of the ETCCDI (Expert Team on Climate Change Detection and Indices) precipitation indices calculated from a new interpolated dataset of daily precipitation, namely SPAIN02, regular at 0.2° horizontal resolution (around 20 km) and from two high-quality stations: the Ebro and Fabra observatories. Using a jack-knife technique, we have found that the sampling error of the SPAIN02 regional averaged is relatively low. The trend analysis has been implemented using a Circular Block Bootstrap procedure applicable to non-normal distributions and autocorrelated series. A running trend analysis has been applied to analyze the trend persistence. No general trends at a regional scale are observed, considering the annual or the seasonal regional averaged series of all the indices for all the time windows considered. Only the consecutive dry days index (CDD) at annual scale shows a locally coherent spatial trend pattern; around 30% of the Catalonia area has experienced an increase of around 2¿3 days decade¿1. The Ebro and Fabra observatories show a similar CDD trend, mainly due to the summer contribution. Besides this, a significant decrease in total precipitation (around ¿10 mm decade¿1) and in the index "highest precipitation amount in five-day period" (RX5DAY, around ¿5 mm decade¿1), have been found in summer for the Ebro observatory.