Adaptive model selection using empirical complexities

Given $n$ independent replicates of a jointly distributed pair $(X,Y)\in {\cal R}^d \times {\cal R}$, we wish to select from a fixed sequence of model classes ${\cal F}_1, {\cal F}_2, \ldots$ a deterministic prediction rule $f: {\cal R}^d \to {\cal R}$ whose risk is small. We investigate the possibility of empirically assessingthe {\em complexity} of each model class, that is, the actual difficulty of the estimation problem within each class. The estimated complexities are in turn used to define an adaptive model selection procedure, which is based on complexity penalized empirical risk.The available data are divided into two parts. The first is used to form an empirical cover of each model class, and the second is used to select a candidate rule from each cover based on empirical risk. The covering radii are determined empirically to optimize a tight upper bound on the estimation error. An estimate is chosen from the list of candidates in order to minimize the sum of class complexity and empirical risk. A distinguishing feature of the approach is that the complexity of each model class is assessed empirically, based on the size of its empirical cover.Finite sample performance bounds are established for the estimates, and these bounds are applied to several non-parametric estimation problems. The estimates are shown to achieve a favorable tradeoff between approximation and estimation error, and to perform as well as if the distribution-dependent complexities of the model classes were known beforehand. In addition, it is shown that the estimate can be consistent,and even possess near optimal rates of convergence, when each model class has an infinite VC or pseudo dimension.For regression estimation with squared loss we modify our estimate to achieve a faster rate of convergence.

R&D cooperation and spillovers: Some empirical evidence

This paper provides some first empirical evidence on the relationshipbetween R&D spillovers and R&D cooperation. The results suggest disentangling different aspects of know-how flows. Firms which rate incoming spillovers more importantly and who can limit outgoing spillovers by a more effective protection of know-how, are more likely to cooperate in R&D. Our analysis also finds that cooperating firms have higher incoming spillovers and higher protection of know-how, indicating that cooperation may serve as a vehicle to manage information flows. Our results thus suggest that on the one hand the information sharing and coordination aspects of incoming spillovers are crucial in understanding cooperation, while on the other hand, protection against outgoing spillovers is important for firms to engage in stable cooperative agreements by reducing free-rider problems. Distinguishing different types of cooperative partners reveals that while managing outgoing spillovers is less critical in alliances with non-commercial research partners than between vertically related partners, the incoming spillovers seem to be more critical in understanding the former type of R&D cooperation.

Market institutions and judicial rulemaking

Assuming that the degree of discretion granted to judges was the main distinguishing feature between common and civil law until the 19th century, we argue that constraining judicial discretion was instrumental in protecting freedom of contract and developing the market order in civil law. We test this hypothesis by analyzing the history of Western law. In England, a unique institutional balance between the Crown and the Parliament guaranteed private property and prompted the gradual evolution towards a legal framework that facilitated market relationships, a process that was supported by the English judiciary. On the Continent, however, legal constraints on the market were suppressed in a top-down fashion by the founders of the liberal state, often against the will of the incumbent judiciary. Constraining judicial discretion there was essential for enforcing freedom of contract and establishing the legal order of the market economy. In line with this evidence, our selection hypothesis casts doubts on the normative interpretation of empirical results that proclaim the superiority of one legal system over another, disregarding the local conditions and institutional interdependencies on which each legal system was grounded.

Confusió i borsa

En aquest article es conceptualitza la confusió en termes d'incertesa, considerant posteriorment com intervé en el procés de formació de creences i en la presa de decisions d'inversió i distingint tres tipus d'estratègies inversores, la diversificació, la concentració en empreses confiant en el pla empresarial i en la capacitat de gestió i, finalment, el seguidisme, referent a l'estratègia basada en confiar en tercers (rumors, notícies, experts, gurus ...). D'acord amb aquesta anàlisi, s'estableix la influència de la informació i la confusió en formació de les bombolles financeres i s'il·lustra amb l'exemple de la bombolla immobiliària i el crac borsari de 2008 a Espanya.

On homology searches by protein Blast and the characterization of the age of genes

Background: It has been shown in a variety of organisms, including mammals, that genes that appeared recently in evolution, for example orphan genes, evolve faster than older genes. Low functional constraints at the time of origin of novel genes may explain these results. However, this observation has been recently attributed to an artifact caused by the inability of Blast to detect the fastest genes in different eukaryotic genomes. Distinguishing between these two possible explanations would be of great importance for any studies dealing with the taxon distribution of proteins and the origin of novel genes. Results: Here we used simulations of protein sequences to examine the capacity of Blast to detect proteins of diverse evolutionary rates in the different species of an eukaryotic phylogenetic tree that included metazoans, fungi and plants. We simulated the evolution of protein genes with the same evolutionary rates than those observed in functional mammalian genes and with among-site rate heterogeneity. Under these conditions, we found that only a very small percentage of simulated ancestral eukaryotic proteins was affected by the Blast artifact. We show that the good detectability of Blast is due to the heterogeneity of protein evolutionary rates at different sites, since only a small conserved motif in a sequence suffices to detect its homologues. Our results indicate that Blast, at least when applied within eukaryotes, only misses homologues of extremely fast-evolving sequences, which are rare in the mammalian genome, as well as sequences evolving homogeneously or pseudogenes.Conclusion: Although great care should be exercised in the recognition of remote homologues, most functional mammalian genes can be detected in eukaryotic genomes by Blast. That is, the majority of functional mammalian genes are not as fast as for not being detected in other metazoans, fungi or plants, if they had been present in these organisms. Thus, the correlation previously found between age and rate seems not to be due to a pure Blast artifact, at least for mammals. This may have important implications to understand the mechanisms by which novel genes originate.

La gestualidad de la barba y el mentón en la Antigüedad romana

Beards and chins are two parts of the body that are associated with a large number of gestures. This paper examines a number of texts in which these gestures appear and the meaning they convey. The analysis was conducted by distinguishing between self-adaptor gestures (those that do not involve a second party), alter-directed adaptors (those that, to the contrary, involve the intervention of another person) and object-adaptors (a category that encompasses gestures involving an object).

Aprender verbos semánticamente similares: materiales didácticos electrónicos para estudiantes de ELE

El trabajo consiste en un análisis y la evaluación de materiales electrónicos existentes sobre parejas de verbos con significados parecidos, además de la ampliación de estos materiales y la creación de un blog para poner-los a disposición de los estudiantes de ELE

Cuestiones sobre el contrato de servicios diseñado en el Marco Común de Referencia

La reciente publicación del draft del Common Frame of Reference invita a reflexionar sobre la figura del contrato de servicios, tal como ha sido desarrollada por el Study Group on a European Civil Code, y respecto de la que encontramos verdaderas innovaciones en comparación con la teoría tradicional que aún mantienen nuestra doctrina y jurisprudencia. El objeto del trabajo es exponer algunas de las soluciones que propone el derecho contractual europeo, e incidir en la posibilidad y conveniencia de su aplicación en nuestro país, con vistas a la oportuna elaboración de la tan esperada regulación civil sobre el contrato de servicios.

Relaciones de complacencia y deberes para con los invitados

En la STS, 1a, 17.7.2007 (RJ 2007\4895, MP: Francisco Marín Castán), el Tribunal Supremo sostiene que los daños que sufre una amiga de los demandados en el inmueble de éstos al tropezar con un juguete abandonado en el suelo del pasillo, insuficientemente iluminado, no son indemnizables, porque dada la especial relación de confianza entre las partes, ese nivel extremo de diligencia no es exigible. El Tribunal parece aplicar al caso un patrón de diligencia quam in suis, la que despliega uno en sus propios asuntos, que permitiría limitar la responsabilidad a los casos de dolo o culpa grave. El trabajo comenta la sentencia y presenta, además, la clasificación entre invitee, licensee y trespasser que el Common Law norteamericano ha utilizado tradicionalmente para delimitar los niveles de cuidado de propietarios (o poseedores) de inmuebles y que el borrador No. 6 del Restatement (Third) of Torts, de 12.9.2007, ha simplificado, añadiendo a la regla tradicional de No Duty to Trespasser la de una negligencia simple para los Innocent Trespasser.

The persistence of return on assets: differences between industries and differences between firms

This study offers a statistical analysis of the persistence of annual profits across a sample of firms from different European Union (EU) countries. To this end, a Bayesian dynamic model has been used which enables the annual behaviour of those profits to be broken down into a permanent structural component on the one hand and a transitory component on the other, while also distinguishing between general effects affecting the industry as a whole to which each firm belongs and specific effects affecting each firm in particular. This break down enables the relative importance of those fundamental components to be evaluated. The data analysed come from a sample of 23,293 firms in EU countries selected from the AMADEUS data-base. The period analysed ran from 1999 to 2007 and 21 sectors were analysed, chosen in such a way that there was a sufficiently large number of firms in each country*sector combination for the industry effects to be estimated accurately enough for meaningful comparisons to be made by sector and country. The analysis has been conducted by sector and by country from a Bayesian perspective, thus making the study more flexible and realistic since the estimates obtained do not depend on asymptotic results. In general terms, the study finds that, although the industry effects are significant, more important are the specific effects. That importance varies depending on the sector or the country in which the firm carries out its activity. The influence of firm effects accounts for more than 90% of total variation and display a significantly lower degree of persistence, with adjustment speeds oscillating around 51.1%. However, this pattern is not homogeneous but depends on the sector and country analysed. Industry effects have a more marginal importance, being significantly more persistent, with adjustment speeds oscillating around 10% with this degree of persistence being more homogeneous at both country and sector levels.

Características sedimentológicas y tipología de pliegues sinsedimentarios en liditas: el ejemplo de la plataforma siliciclástica paleozoica del Sarrabus (SE de la isla de Cerdeña, Italia)

This paper studies different black, banded siliceous rocks (lidites) from a Paleozoic unstable shelf (Sarrabus, Southeast Sardinia). These lidites were derived from submarine vents as a consequence of hydrothermal-sedimentary processes. The paper examines the sedimentological characteristics of lidites, studies the different types of associated synsedimentary folds and offers criteria for distinguishing lidites which take root in a vent (first type) from those which were glided through a paleoslope (second type).

Ultrastructural characters of the spermatozoon of the digenean Hypocreadium caputvadum Kacem et al., 2011 (Lepocreadioidea: Lepocreadiidae), an intestinal parasite of Balistes capriscus in Tunisia

The ultrastructural organization of the spermatozoon of the digenean Hypocreadium caputvadum (Lepocreadioidea: Lepocreadiidae) is described. Live digeneans were collected from Balistes capriscus (Teleostei: Balistidae) from the Gulf of Gabès, Tunisia (Eastern Mediterranean Sea). The mature spermatozoon of H. caputvadum shows several ultrastructural characters such as two axonemes of different lengths exhibiting the classical 9 +"1" trepaxonematan pattern, a nucleus, two mitochondria, granules of glycogen, external ornamentation of the plasma membrane and two bundles of parallel cortical microtubules. Moreover, in the anterior extremity, the second axoneme is partly surrounded by a discontinuous and submembranous layer of electron-dense material. Our study provides new data on the spermatozoon of H. caputvadum in order to improve the understanding of phylogenetic relationships in the Digenea, particularly in the superfamily Lepocreadioidea. In this context, the electron-dense material surrounding one of the axonemes in the anterior spermatozoon extremity constitutes the unique distinguishing ultrastructural character of lepocreadioideans, and it is present in spermatozoa of lepocreadiids, aephnidiogenids and gyliauchenids.

Ultrastructural characters of the spermatozoon of the digenean Hypocreadium caputvadum Kacem et al., 2011 (Lepocreadioidea: Lepocreadiidae), an intestinal parasite of Balistes capriscus in Tunisia

The ultrastructural organization of the spermatozoon of the digenean Hypocreadium caputvadum (Lepocreadioidea: Lepocreadiidae) is described. Live digeneans were collected from Balistes capriscus (Teleostei: Balistidae) from the Gulf of Gabès, Tunisia (Eastern Mediterranean Sea). The mature spermatozoon of H. caputvadum shows several ultrastructural characters such as two axonemes of different lengths exhibiting the classical 9 +"1" trepaxonematan pattern, a nucleus, two mitochondria, granules of glycogen, external ornamentation of the plasma membrane and two bundles of parallel cortical microtubules. Moreover, in the anterior extremity, the second axoneme is partly surrounded by a discontinuous and submembranous layer of electron-dense material. Our study provides new data on the spermatozoon of H. caputvadum in order to improve the understanding of phylogenetic relationships in the Digenea, particularly in the superfamily Lepocreadioidea. In this context, the electron-dense material surrounding one of the axonemes in the anterior spermatozoon extremity constitutes the unique distinguishing ultrastructural character of lepocreadioideans, and it is present in spermatozoa of lepocreadiids, aephnidiogenids and gyliauchenids.

Sociodemographic Factors and Clinical Conditions Associated to Hospitalization in Influenza A (H1N1) 2009 Virus Infected Patients in Spain, 2009-2010

The emergence and pandemic spread of a new strain of influenza A (H1N1) virus in 2009 resulted in a serious alarm in clinical and public health services all over the world. One distinguishing feature of this new influenza pandemic was the different profile of hospitalized patients compared to those from traditional seasonal influenza infections. Our goal was to analyze sociodemographic and clinical factors associated to hospitalization following infection by influenza A(H1N1) virus. We report the results of a Spanish nationwide study with laboratory confirmed infection by the new pandemic virus in a case-control design based on hospitalized patients. The main risk factors for hospitalization of influenza A (H1N1) 2009 were determined to be obesity (BMI≥40, with an odds-ratio [OR] 14.27), hematological neoplasia (OR 10.71), chronic heart disease, COPD (OR 5.16) and neurological disease, among the clinical conditions, whereas low education level and some ethnic backgrounds (Gypsies and Amerinds) were the sociodemographic variables found associated to hospitalization. The presence of any clinical condition of moderate risk almost triples the risk of hospitalization (OR 2.88) and high risk conditions raise this value markedly (OR 6.43). The risk of hospitalization increased proportionally when for two (OR 2.08) or for three or more (OR 4.86) risk factors were simultaneously present in the same patient. These findings should be considered when a new influenza virus appears in the human population.

The Rose Bengal test in human brucellosis: a neglected test for the diagnosis of a neglected disease

Brucellosis is a highly contagious zoonosis affecting livestock and human beings. The human disease lacks pathognomonic symptoms and laboratory tests are essential for its diagnosis. However, most tests are difficult to implement in the areas and countries were brucellosis is endemic. Here, we compared the simple and cheap Rose Bengal Test (RBT) with serum agglutination, Coombs, competitive ELISA, Brucellacapt, lateral flow immunochromatography for IgM and IgG detection and immunoprecipitation with Brucella proteins. We tested 208 sera from patients with brucellosis proved by bacteriological isolation, 20 contacts with no brucellosis, and 1559 sera of persons with no recent contact or brucellosis symptoms. RBT was highly sensitive in acute and long evolution brucellosis cases and this related to its ability to detect IgM, IgG and IgA, to the absence of prozones, and to the agglutinating activity of blocking IgA at the pH of the test. RBT was also highly specific in the sera of persons with no contact with Brucella. No test in this study outperformed RBT, and none was fully satisfactory in distinguishing contacts from infected patients. When modified to test serum dilutions, a diagnostic titer >4 in RBT resulted in 87.4% sensitivity (infected patients) and 100% specificity (contacts). We discuss the limitations of serological tests in the diagnosis of human brucellosis, particularly in the more chronic forms, and conclude that simplicity and affordability of RBT make it close to the ideal test for small and understaffed hospitals and laboratories.