Auction theory, sequential local service privatization, and the effects of geographical scale economies on effective competition

A sequential weakly efficient two-auction game with entry costs, interdependence between objects, two potential bidders and IPV assumption is presented here in order to give some theoretical predictions on the effects of geographical scale economies on local service privatization performance. It is shown that the first object seller takes profit of this interdependence. The interdependence externality rises effective competition for the first object, expressed as the probability of having more than one final bidder. Besides, if there is more than one final bidder in the first auction, seller extracts the entire bidder¿s expected future surplus differential between having won the first auction and having lost. Consequences for second object seller are less clear, reflecting the contradictory nature of the two main effects of object interdependence. On the one hand, first auction winner becomes ¿stronger¿, so that expected payments rise in a competitive environment. On the other hand, first auction loser becomes relatively ¿weaker¿, hence (probably) reducing effective competition for the second object. Additionally, some contributions to static auction theory with entry cost and asymmetric bidders are presented in the appendix

Absence of epidemic threshold in scale free networks with degree correlations

Random scale-free networks have the peculiar property of being prone to the spreading of infections. Here we provide for the susceptible-infected-susceptible model an exact result showing that a scale-free degree distribution with diverging second moment is a sufficient condition to have null epidemic threshold in unstructured networks with either assortative or disassortative mixing. Degree correlations result therefore irrelevant for the epidemic spreading picture in these scale-free networks. The present result is related to the divergence of the average nearest neighbors degree, enforced by the degree detailed balance condition.

Generation of uncorrelated random scale-free networks

Uncorrelated random scale-free networks are useful null models to check the accuracy and the analytical solutions of dynamical processes defined on complex networks. We propose and analyze a model capable of generating random uncorrelated scale-free networks with no multiple and self-connections. The model is based on the classical configuration model, with an additional restriction on the maximum possible degree of the vertices. We check numerically that the proposed model indeed generates scale-free networks with no two- and three-vertex correlations, as measured by the average degree of the nearest neighbors and the clustering coefficient of the vertices of degree k, respectively.

Damage spreading transition in glasses: A probe for the ruggedness of the configurational landscape

We consider damage spreading transitions in the framework of mode-coupling theory. This theory describes relaxation processes in glasses in the mean-field approximation which are known to be characterized by the presence of an exponentially large number of metastable states. For systems evolving under identical but arbitrarily correlated noises, we demonstrate that there exists a critical temperature T0 which separates two different dynamical regimes depending on whether damage spreads or not in the asymptotic long-time limit. This transition exists for generic noise correlations such that the zero damage solution is stable at high temperatures, being minimal for maximal noise correlations. Although this dynamical transition depends on the type of noise correlations, we show that the asymptotic damage has the good properties of a dynamical order parameter, such as (i) independence of the initial damage; (ii) independence of the class of initial condition; and (iii) stability of the transition in the presence of asymmetric interactions which violate detailed balance. For maximally correlated noises we suggest that damage spreading occurs due to the presence of a divergent number of saddle points (as well as metastable states) in the thermodynamic limit consequence of the ruggedness of the free-energy landscape which characterizes the glassy state. These results are then compared to extensive numerical simulations of a mean-field glass model (the Bernasconi model) with Monte Carlo heat-bath dynamics. The freedom of choosing arbitrary noise correlations for Langevin dynamics makes damage spreading an interesting tool to probe the ruggedness of the configurational landscape.

Large scale purification of presynaptic plasma membranes from Torpedo marmorata electric organ

The presynaptic plasma membrane (PSPM) of cholinergic nerve terminals was purified from Torpedo electric organ using a large-scale procedure. Up to 500 g of frozen electric organ were fractioned in a single run, leading to the isolation of greater than 100 mg of PSPM proteins. The purity of the fraction is similar to that of the synaptosomal plasma membrane obtained after subfractionation of Torpedo synaptosomes as judged by its membrane-bound acetylcholinesterase activity, the number of Glycera convoluta neurotoxin binding sites, and the binding of two monoclonal antibodies directed against PSPM. The specificity of these antibodies for the PSPM is demonstrated by immunofluorescence microscopy.

Network-based scoring system for genome-scale metabolic reconstructions

Background: Network reconstructions at the cell level are a major development in Systems Biology. However, we are far from fully exploiting its potentialities. Often, the incremental complexity of the pursued systems overrides experimental capabilities, or increasingly sophisticated protocols are underutilized to merely refine confidence levels of already established interactions. For metabolic networks, the currently employed confidence scoring system rates reactions discretely according to nested categories of experimental evidence or model-based likelihood. Results: Here, we propose a complementary network-based scoring system that exploits the statistical regularities of a metabolic network as a bipartite graph. As an illustration, we apply it to the metabolism of Escherichia coli. The model is adjusted to the observations to derive connection probabilities between individual metabolite-reaction pairs and, after validation, to assess the reliability of each reaction in probabilistic terms. This network-based scoring system uncovers very specific reactions that could be functionally or evolutionary important, identifies prominent experimental targets, and enables further confirmation of modeling results. Conclusions: We foresee a wide range of potential applications at different sub-cellular or supra-cellular levels of biological interactions given the natural bipartivity of many biological networks.

Nanometer-scale oxidation of Si(100) surfaces by tapping mode atomic force microscopy

The nanometer¿scale oxidation of Si(100) surfaces in air is performed with an atomic force microscope working in tapping mode. Applying a positive voltage to the sample with respect to the tip, two kinds of modifications are induced on the sample: grown silicon oxide mounds less than 5 nm high and mounds higher than 10 nm (which are assumed to be gold depositions). The threshold voltage necessary to produce the modification is studied as a function of the average tip¿to¿sample distance.

La vegetació de la serra de Moixeró i el massís de la Tosa d'Alp (Pirineus orientals).

This work offers an approach to the vegetation of the Pyrenean area mentioned above according to three successive and related levels -vascularflora, plant communities and plant landscape. The study area stretches over 147.5 square km (projected surface), nearly 70% belonging to Cadí-Moixeró Natural Park. Altitudes rise from 720 m a.s.l. (Southern part) and 1100 m a.s.l. (Northern part) to 2536 m a.s.l. at the top ofla Tosa d'Alp. Limestone, the most common substrate, constitutes the highest mountain ranges in the area and also the roughest relief. Slate, carbonated slate, marl, sandstone and different kinds of conglomerate are also present. The bioclimate of lower parts is axeromeric sub-mediterranean type in the Gaussen scale, with a marked continental factor in the Northern sector (Cerdanya district). High parts have high mountain climates -cold axeric, subalpine and alpine types.

Construction of a scale to evaluate the diurnal impact of insomnia

The objective of this study was to develop and validate a scale to assess the diurnal impact of insomnia. The Insomnia Diurnal Impact Scale (IDIS) comprises six items designed to evaluate the daytime effects of insomnia. The sychometric properties of the original scale were analysed in a sample of 172 students, while its ability to differentiate insomniacs and non-insomniacs (according to the International Classification of Diseases (ICD)-10 criteria) was examined in a sample of 79 psychiatric patients and 82 individuals from the community. The psychometric properties of the English version were then analysed in a sample of 44 Englishspeaking participants. The results showed the internal consistency coefficient to be very good (0.86), with testretest reliability at 1 month being 0.79. A single factor explained almost 60% of the variance. Correlation of the IDIS with other scales varied between moderate and high values. Sensitivity was 78% and specificity 57% in the community sample, while the corresponding figures for the psychiatric population were 83% and 63%. Cronbach's ¿ coefficient for the English version reached a value of 0.93. These results indicate that the IDIS shows adequate reliability and validity with both general and psychiatric populations, and also that it can discriminate between the presence and absence of insomnia. The English version presents good preliminary results regarding item-corrected total correlation and internal consistency. In conclusion, the IDIS appears to be a useful tool in the primary care and mental health contexts for assessing insomnia-related diurnal dysfunction.

Bioinformatics: making large-scale science happen

Bionformatics is a rapidly evolving research field dedicated toanalyzing and managing biological data with computational resources. This paperaims to overview some of the processes and applications currently implementedat CCiT-UB¿s Bioinformatics Unit, focusing mainly on the areas of Genomics,Transcriptomics and Proteomics

Inclusion of soil erosion impacts in life cycle assessment on a global scale: application to energy crops in Spain

Purpose: Despite the fundamental role of ecosystem goods and services in sustaining human activities, there is no harmonized and internationally agreed method for including them in life cycle assessment (LCA). The main goal of this study was to develop a globally applicable and spatially resolved method for assessing land-use impacts on the erosion regulation ecosystem service.Methods: Soil erosion depends much on location. Thus, unlike conventional LCA, the endpoint method was regionalized at the grid-cell level (5 arc-minutes, approximately 10×10 km2) to reflect the spatial conditions of the site. Spatially explicit characterization factors were not further aggregated at broader spatial scales. Results and discussion: Life cycle inventory data of topsoil and topsoil organic carbon (SOC) losses were interpreted at the endpoint level in terms of the ultimate damage to soil resources and ecosystem quality. Human health damages were excluded from the assessment. The method was tested on a case study of five three-year agricultural rotations, two of them with energy crops, grown in several locations in Spain. A large variation in soil and SOC losses was recorded in the inventory step, depending on climatic and edaphic conditions. The importance of using a spatially explicit model and characterization factors is shown in the case study.Conclusions and outlook: The regionalized assessment takes into account the differences in soil erosion-related environmental impacts caused by the great variability of soils. Taking this regionalized framework as the starting point, further research should focus on testing the applicability of the method trough the complete life cycle of a product and on determining an appropriate spatial scale at which to aggregate characterization factors, in order to deal with data gaps on location of processes, especially in the background system. Additional research should also focus on improving reliability of the method by quantifying and, insofar as it is possible, reducing uncertainty.