994 resultados para Integration, Functional


Relevância:

20.00% 20.00%

Publicador:

Resumo:

We study the link between corruption and economic integration. We show that if an economic union establishes a common regulation for public procurement, the country more prone to corruption benefits more from integration. However, if the propensities to corruption are too distinct, the less corrupt country will not be willing to join the union. This difference in corruption propensities can be offset by a difference in efficiency. We also show that corruption is lower if integration occurs. A panel data analysis for the European Union confirms that more corrupt countries are more favorable towards integration but less acceptable as potential new members.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Abstract Accurate characterization of the spatial distribution of hydrological properties in heterogeneous aquifers at a range of scales is a key prerequisite for reliable modeling of subsurface contaminant transport, and is essential for designing effective and cost-efficient groundwater management and remediation strategies. To this end, high-resolution geophysical methods have shown significant potential to bridge a critical gap in subsurface resolution and coverage between traditional hydrological measurement techniques such as borehole log/core analyses and tracer or pumping tests. An important and still largely unresolved issue, however, is how to best quantitatively integrate geophysical data into a characterization study in order to estimate the spatial distribution of one or more pertinent hydrological parameters, thus improving hydrological predictions. Recognizing the importance of this issue, the aim of the research presented in this thesis was to first develop a strategy for the assimilation of several types of hydrogeophysical data having varying degrees of resolution, subsurface coverage, and sensitivity to the hydrologic parameter of interest. In this regard a novel simulated annealing (SA)-based conditional simulation approach was developed and then tested in its ability to generate realizations of porosity given crosshole ground-penetrating radar (GPR) and neutron porosity log data. This was done successfully for both synthetic and field data sets. A subsequent issue that needed to be addressed involved assessing the potential benefits and implications of the resulting porosity realizations in terms of groundwater flow and contaminant transport. This was investigated synthetically assuming first that the relationship between porosity and hydraulic conductivity was well-defined. Then, the relationship was itself investigated in the context of a calibration procedure using hypothetical tracer test data. Essentially, the relationship best predicting the observed tracer test measurements was determined given the geophysically derived porosity structure. Both of these investigations showed that the SA-based approach, in general, allows much more reliable hydrological predictions than other more elementary techniques considered. Further, the developed calibration procedure was seen to be very effective, even at the scale of tomographic resolution, for predictions of transport. This also held true at locations within the aquifer where only geophysical data were available. This is significant because the acquisition of hydrological tracer test measurements is clearly more complicated and expensive than the acquisition of geophysical measurements. Although the above methodologies were tested using porosity logs and GPR data, the findings are expected to remain valid for a large number of pertinent combinations of geophysical and borehole log data of comparable resolution and sensitivity to the hydrological target parameter. Moreover, the obtained results allow us to have confidence for future developments in integration methodologies for geophysical and hydrological data to improve the 3-D estimation of hydrological properties.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

BACKGROUND: Tropomyosin (TM), an essential actin-binding protein, is central to the control of calcium-regulated striated muscle contraction. Although TPM1alpha (also called alpha-TM) is the predominant TM isoform in human hearts, the precise TM isoform composition remains unclear. METHODS AND RESULTS: In this study, we quantified for the first time the levels of striated muscle TM isoforms in human heart, including a novel isoform called TPM1kappa. By developing a TPM1kappa-specific antibody, we found that the TPM1kappa protein is expressed and incorporated into organized myofibrils in hearts and that its level is increased in human dilated cardiomyopathy and heart failure. To investigate the role of TPM1kappa in sarcomeric function, we generated transgenic mice overexpressing cardiac-specific TPM1kappa. Incorporation of increased levels of TPM1kappa protein in myofilaments leads to dilated cardiomyopathy. Physiological alterations include decreased fractional shortening, systolic and diastolic dysfunction, and decreased myofilament calcium sensitivity with no change in maximum developed tension. Additional biophysical studies demonstrate less structural stability and weaker actin-binding affinity of TPM1kappa compared with TPM1alpha. CONCLUSIONS: This functional analysis of TPM1kappa provides a possible mechanism for the consequences of the TM isoform switch observed in dilated cardiomyopathy and heart failure patients.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Although it is commonly accepted that most macroeconomic variables are nonstationary, it is often difficult to identify the source of the non-stationarity. In particular, it is well-known that integrated and short memory models containing trending components that may display sudden changes in their parameters share some statistical properties that make their identification a hard task. The goal of this paper is to extend the classical testing framework for I(1) versus I(0)+ breaks by considering a a more general class of models under the null hypothesis: non-stationary fractionally integrated (FI) processes. A similar identification problem holds in this broader setting which is shown to be a relevant issue from both a statistical and an economic perspective. The proposed test is developed in the time domain and is very simple to compute. The asymptotic properties of the new technique are derived and it is shown by simulation that it is very well-behaved in finite samples. To illustrate the usefulness of the proposed technique, an application using inflation data is also provided.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Abstract Telomeres, the natural ends of chromosomes, need to be protected from chromosome end fusions, aberrant homologous recombination and degradation. In humans, chromosome ends are specified through arrays of tandemly repeated 5'-TTAGGG-3' hexamers, ending in a 3' overhang. A complex formed by the six proteins TRF1, TRF2, hRap1, TIN2, TPP1 and POT1 specifically assocìates with and protects telomeres. Telomeres are maintained by semiconservative DNA replication and by a specialized reverse transcriptase, telomerase, that carries an RNA subunit which templates new telomeric repeat synthesis. The telomeric single stranded (ss) DNA binding protein POT1 protects the telomeric 3' overhang and modulates telomerase-mediated telomere elongation. It is possible that POT1 also influences DNA synthesis during semiconservative DNA replication, which is initiated by the DNA polymerase alpha-primase complex. The heterotrimeric ss DNA-binding protein RPA plays essential roles during DNA replication. RPA binds to ss DNA with high affinity in order to stabilize ss DNA and facilitate nascent strand synthesis at the replication fork. Here we investigate how the two proteins RPA and POT1 contribute to telomere maintenance by regulating semi-conservative DNA replication and telomerase. Using chromatin immunoprecipitation experiments, we show that RPA associates with telomeres during S-phase. Analysis of telomere structure in cells shRNA-depleted for RPA and POT1 reveals that loss of RPA and POT1 causes exposure of single-stranded DNA at telomeres, suggestive of incomplete DNA replication. Biochemical experiments using purified recombinant POT1 and RPA show that saturating telomeric oligonucleotides with POT1 or RPA reduces the primase activity of the DNA polymerase alpha-primase complex and the overall activity of telomerase. POT1 and RPA also increase the primer extension by DNA polymerase alpha-primase complex and the processivity of telomerase under certain conditions, although POT1 increases the activities to a greater extent than RPA. We propose that POT1 is required for proper replication of the lagging strand of telomeres and that some phenotypes observed in POT1-depleted cells may stern from incomplete DNA replication rather than de-protection of the single-stranded overhang. Résumé Les télomères, les extrémités normales des chromosomes linéaires, doivent être protégés des fusions chromosomiques, d'événements de recombinaison homologue aberrants et de phénomènes de dégradation. Chez l'Homme, les extrémités des chromosomes sont constitués d'ADN double brin répétitif de séquence 5'-TTAGGG-3', d'une extension simple brin 3' sortante et d'un complexe protéique formé des six facteurs TRF1, TRF2, hRap1, TIN2, TPP1 et POT1 qui, s'associant à cette séquence, protègent l'ADN télomèrique. Les télomères sont maintenus par la télomérase, une transcriptase inverse capable d'allonger l'extension 3' sortante télomérique. POT1 lie l'ADN simple brin télomérique et module l'élongation des télomères par la télomérase. POT1 pourrait en théorie également influencer la réplication semi-conservative de l'ADN. L'ADN-polymérase Pal alpha-primase amorce et initie la synthèse d'ADN. Pendant la réplication, l'ADN simple brin est stabilisé par RPA, un complexe hétérotrimèrique qui lie l'ADN simple brin. RPA facilite la synthèse du brin naissant à la fourche de réplication. Ici nous avons étudié comment ces deux protéines qui lient l'ADN simple brin, RPA et POT1, régulent la réplication des télomères par la télomérase et la machinerie classique de réplication de l'ADN. Par immunoprécipitation de chromatine (ChIP), nous montrons que RPA est localisé aux télomères lors de la phase S du cycle cellulaire. De plus, l'analyse de la structure des télomeres indique que !a perte de RPA ou de POT1 conduit à l'apparition d'ADN simple brin télomérique, suggérant une réplication incomplète de l'ADN télomérique in vivo. Par une approche complémentaire biochimique utilisant les protéines POT1 et RPA recombinantes purifiées, nous montrons également que la liaison de POT1 ou de RPA à des oligonucléotides télomériques bloque l'activité primase du complexe polymérase alpha/primase et réduit l'activité télomérase sur ces substrats. En revanche, leur liaison augmente l'activité ADN-polymérase du complexe polymérase alpha/primase, ainsi que fa processivité de la télomérase dans certaines conditions, POT1 étant le plus efficace des deux facteurs. Nous proposons que POT1 est nécessaire à la réplication du brin retardé au niveau des télomères, ce qui suggère que certains phénotypes des cellules déplétés en POT1 puissent résulter d'une réplication incomplète de l'ADN télémétrique plutôt que d'une déprotection de l'extrémité sortante des télomères.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Functional response of Telenomus remus Nixon (Hymenoptera, Scelionidae) to Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae) eggs: effect of female age. Functional response of 24-h and 48-h-old Telenomus remus adults was studied on Spodoptera frugiperda eggs. The study was carried out in climatic chamber regulated at 25 ± 1°C, 70 ± 10% RH and 12:12h (L: D). Females of T. remus were honey fed and individualized in glass vials along with 25, 50, 75, 100, 150, 200, 250 or 300 eggs of S. frugiperda for 24 h. Complete randomized design with ten replications was adopted. The parameters evaluated to construct the functional response curve were daily average parasitism, searching rate and oviposition time. It was observed that the higher the egg density, the higher the parasitism for 24-h and 48-h-old females although there was a tendency of parasitism stabilization at 150-egg density. The results showed a type II functional response curve for both 24-h and 48-h-old female.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The origin and specificity of alphabeta TCR(+) T cells that express CD8alphaalpha have been controversial issues. Here we provide direct evidence that precursors of functional CD8alphaalpha T cells are positively selected in the thymus in the presence of agonist self-peptides. Like conventional positive selection, this agonist selection process requires functional TCR alpha-CPM, whereas it is independent of CD8beta expression. Furthermore, CD8alphaalpha expression on mature, agonist-selected T cells does not imply selection by MHC class I, and CD8alphaalpha(+) T cells can be either class I or class II restricted. Our data define a distinct agonist-dependent, positive selection process in the thymus, and they suggest a function for CD8alphaalpha distinct from the conventional TCR coreceptor function of CD8alphabeta or CD4.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

A major challenge in community ecology is a thorough understanding of the processes that govern the assembly and composition of communities in time and space. The growing threat of climate change to the vascular plant biodiversity of fragile ecosystems such as mountains has made it equally imperative to develop comprehensive methodologies to provide insights into how communities are assembled. In this perspective, the primary objective of this PhD thesis is to contribute to the theoretical and methodological development of community ecology, by proposing new solutions to better detect the ecological and evolutionary processes that govern community assembly. As phylogenetic trees provide by far, the most advanced tools to integrate the spatial, ecological and evolutionary dynamics of plant communities, they represent the cornerstone on which this work was based. In this thesis, I proposed new solutions to: (i) reveal trends in community assembly on phylogenies, depicted by the transition of signals at the nodes of the different species and lineages responsible for community assembly, (ii) contribute to evidence the importance of evolutionarily labile traits in the distribution of mountain plant species. More precisely, I demonstrated that phylogenetic and functional compositional turnover in plant communities was driven by climate and human land use gradients mostly influenced by evolutionarily labile traits, (iii) predict and spatially project the phylogenetic structure of communities using species distribution models, to identify the potential distribution of phylogenetic diversity, as well as areas of high evolutionary potential along elevation. The altitudinal setting of the Diablerets mountains (Switzerland) provided an appropriate model for this study. The elevation gradient served as a compression of large latitudinal variations similar to a collection of islands within a single area, and allowed investigations on a large number of plant communities. Overall, this thesis highlights that stochastic and deterministic environmental filtering processes mainly influence the phylogenetic structure of plant communities in mountainous areas. Negative density-dependent processes implied through patterns of phylogenetic overdispersion were only detected at the local scale, whereas environmental filtering implied through phylogenetic clustering was observed at both the regional and local scale. Finally, the integration of indices of phylogenetic community ecology with species distribution models revealed the prospects of providing novel and insightful explanations on the potential distribution of phylogenetic biodiversity in high mountain areas. These results generally demonstrate the usefulness of phylogenies in inferring assembly processes, and are worth considering in the theoretical and methodological development of tools to better understand phylogenetic community structure.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper analyses the integration process that firms follow toimplement Supply Chain Management (SCM). This study has beeninspired in the integration model proposed by Stevens (1989). Hesuggests that companies internally integrate first and then extendintegration to other supply chain members, such as customers andsuppliers.To analyse the integration process a survey was conducted amongSpanish food manufacturers. The results show that there are companiesin three different integration stages. In stage I, companies are notintegrated. In stage II, companies have a medium-high level of internalintegration in the Logistics-Production interface, a low level ofinternal integration in the Logistics-Marketing interface, and a mediumlevel of external integration. And, in stage III, companies have highlevels of integration in both internal interfaces and in some of theirsupply chain relationships.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Seven different electron microscopy techniques habe been employed to study the RecA protein of E. coli. This review provides a summary of the conclusions that have been drawn from these studies, and attempts to relate these observations to models for the role of RecA protein in homologous recombination.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The aim of the present study was to investigate the relative importance of flooding- and confinement-related environmentalfeatures in explaining macroinvertebrate trait structure and diversity in a pool of wetlands located in a Mediterranean riverfloodplain. To test hypothesized trait-environment relationships, we employed a recently implemented statistical procedure, thefourth-corner method. We found that flooding-related variables, mainly pH and turbidity, were related to traits that confer an abilityof the organism to resist flooding (e.g., small body-shape, protection of eggs) or recuperate faster after flooding (e.g., short life-span, asexual reproduction). In contrast, confinement-related variables, mainly temperature and organic matter, enhanced traits that allow organisms to interact and compete with other organisms (e.g., large size, sexual reproduction) and to efficiently use habitat and resources (e.g., diverse locomotion and feeding strategies). These results are in agreement with predictions made under the River Habitat Templet for lotic ecosystems, and demonstrate the ability of the fourth-corner method to test hypothesis that posit traitenvironment relationships. Trait diversity was slightly higher in flooded than in confined sites, whereas trait richness was not significantly different. This suggests that although trait structure may change in response to the main environmental factors, as evidenced by the fourth-corner method, the number of life-history strategies needed to persist in the face of such constraints remains more or less constant; only their relative dominance differs

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The paper argues that a functional reduction of ordinary psychology to neuropsychology is possible by means of constructing fine-grained functional, mental sub-types that are coextensive with neuropsychological types. We establish this claim by means of considering as examples the cases of the disconnection syndrome and schizophrenia. We point out that the result is a conservative reduction, vindicating the scientific quality of the mental types of ordinary psychology by systematically linking them with neuroscience. That procedure of conservative reduction by means of functional sub-types is in principle repeatable down to molecular neuroscience.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

CONTEXT: Recent magnetic resonance imaging studies have attempted to relate volumetric brain measurements in early schizophrenia to clinical and functional outcome some years later. These studies have generally been negative, perhaps because gray and white matter volumes inaccurately assess the underlying dysfunction that might be predictive of outcome. OBJECTIVE: To investigate the predictive value of frontal and temporal spectroscopy measures for outcome in patients with first-episode psychoses. DESIGN: Left prefrontal cortex and left mediotemporal lobe voxels were assessed using proton magnetic resonance spectroscopy to provide the ratio of N-acetylaspartate (NAA) and choline-containing compounds to creatine and phosphocreatine (Cr) (NAA/Cr ratio). These data were used to predict outcome at 18 months after admission, as assessed by a systematic medical record audit. SETTING: Early psychosis clinic. PARTICIPANTS: Forty-six patients with first-episode psychosis. MAIN OUTCOME MEASURES: We used regression models that included age at imaging and duration of untreated psychosis to predict outcome scores on the Global Assessment of Functioning Scale, Clinical Global Impression scales, and Social and Occupational Functional Assessment Scale, as well as the number of admissions during the treatment period. We then further considered the contributions of premorbid function and baseline level of negative symptoms. RESULTS: The only spectroscopic predictor of outcome was the NAA/Cr ratio in the prefrontal cortex. Low scores on this variable were related to poorer outcome on all measures. In addition, the frontal NAA/Cr ratio explained 17% to 30% of the variance in outcome. CONCLUSIONS: Prefrontal neuronal dysfunction is an inconsistent feature of early psychosis; rather, it is an early marker of poor prognosis across the first years of illness. The extent to which this can be used to guide treatment and whether it predicts outcome some years after first presentation are questions for further research.