988 resultados para Presence-only


Relevância:

30.00% 30.00%

Publicador:

Resumo:

We estimate the effect of state judiciary presence on rent extraction in Brazilian local governments.We measure rents as irregularities related to waste or corruption uncovered by auditors.Our unique dataset at the level of individual inspections allows us to separately examine extensiveand intensive margins of rent extraction. The identification strategy is based on an institutionalrule of state judiciary branches according to which prosecutors and judges tend to be assigned tothe most populous among contiguous counties forming a judiciary district. Our research designexploits this rule by comparing counties that are largest in their district to counties with identicalpopulation size from other districts in the same state, where they are not the most populous. IVestimates suggest that state judiciary presence reduces the share of inspections with irregularitiesrelated to waste or corruption by about 10 percent or 0.3 standard deviations. In contrast, we findno effect on the intensive margin of rent extraction. Finally, our estimates suggest that judicialpresence reduces rent extraction only for first-term mayors.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This paper discusses the role of deterministic components in the DGP and in the auxiliaryregression model which underlies the implementation of the Fractional Dickey-Fuller (FDF) test for I(1) against I(d) processes with d [0, 1). This is an important test in many economic applications because I(d) processess with d < 1 are mean-reverting although, when 0.5 = d < 1, like I(1) processes, they are nonstationary. We show how simple is the implementation of the FDF in these situations, and argue that it has better properties than LM tests. A simple testing strategy entailing only asymptotically normally distributedtests is also proposed. Finally, an empirical application is provided where the FDF test allowing for deterministic components is used to test for long-memory in the per capita GDP of several OECD countries, an issue that has important consequences to discriminate between growth theories, and on which there is some controversy.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

CgPdr1p is a Candida glabrata Zn(2)-Cys(6) transcription factor involved in the regulation of the ABC-transporter genes CgCDR1, CgCDR2, and CgSNQ2, which are mediators of azole resistance. Single-point mutations in CgPDR1 are known to increase the expression of at least CgCDR1 and CgCDR2 and thus to contribute to azole resistance of clinical isolates. In this study, we investigated the incidence of CgPDR1 mutations in a large collection of clinical isolates and tested their relevance, not only to azole resistance in vitro and in vivo, but also to virulence. The comparison of CgPDR1 alleles from azole-susceptible and azole-resistant matched isolates enabled the identification of 57 amino acid substitutions, each positioned in distinct CgPDR1 alleles. These substitutions, which could be grouped into three different "hot spots," were gain of function (GOF) mutations since they conferred hyperactivity to CgPdr1p revealed by constitutive high expression of ABC-transporter genes. Interestingly, the major transporters involved in azole resistance (CgCDR1, CgCDR2, and CgSNQ2) were not always coordinately expressed in presence of specific CgPDR1 GOF mutations, thus suggesting that these are rather trans-acting elements (GOF in CgPDR1) than cis-acting elements (promoters) that lead to azole resistance by upregulating specific combinations of ABC-transporter genes. Moreover, C. glabrata isolates complemented with CgPDR1 hyperactive alleles were not only more virulent in mice than those with wild type alleles, but they also gained fitness in the same animal model. The presence of CgPDR1 hyperactive alleles also contributed to fluconazole treatment failure in the mouse model. In conclusion, this study shows for the first time that CgPDR1 mutations are not only responsible for in vitro/in vivo azole resistance but that they can also confer a selective advantage under host conditions.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We study the dynamics of reaction-diffusion fronts under the influence of multiplicative noise. An approximate theoretical scheme is introduced to compute the velocity of the front and its diffusive wandering due to the presence of noise. The theoretical approach is based on a multiple scale analysis rather than on a small noise expansion and is confirmed with numerical simulations for a wide range of the noise intensity. We report on the possibility of noise sustained solutions with a continuum of possible velocities, in situations where only a single velocity is allowed without noise.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We investigate the phase behavior of a single-component system in three dimensions with spherically-symmetric, pairwise-additive, soft-core interactions with an attractive well at a long distance, a repulsive soft-core shoulder at an intermediate distance, and a hard-core repulsion at a short distance, similar to potentials used to describe liquid systems such as colloids, protein solutions, or liquid metals. We showed [Nature (London) 409, 692 (2001)] that, even with no evidence of the density anomaly, the phase diagram has two first-order fluid-fluid phase transitions, one ending in a gas¿low-density-liquid (LDL) critical point, and the other in a gas¿high-density-liquid (HDL) critical point, with a LDL-HDL phase transition at low temperatures. Here we use integral equation calculations to explore the three-parameter space of the soft-core potential and perform molecular dynamics simulations in the interesting region of parameters. For the equilibrium phase diagram, we analyze the structure of the crystal phase and find that, within the considered range of densities, the structure is independent of the density. Then, we analyze in detail the fluid metastable phases and, by explicit thermodynamic calculation in the supercooled phase, we show the absence of the density anomaly. We suggest that this absence is related to the presence of only one stable crystal structure.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We propose new methods for evaluating predictive densities. The methods includeKolmogorov-Smirnov and Cram?r-von Mises-type tests for the correct specification ofpredictive densities robust to dynamic mis-specification. The novelty is that the testscan detect mis-specification in the predictive densities even if it appears only overa fraction of the sample, due to the presence of instabilities. Our results indicatethat our tests are well sized and have good power in detecting mis-specification inpredictive densities, even when it is time-varying. An application to density forecastsof the Survey of Professional Forecasters demonstrates the usefulness of the proposedmethodologies.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Recent studies have shown that in humans the germinal center reactions produce three types of V(D)J mutated B cells in similar proportions, i.e. Ig-switched, IgD-IgM+ (IgM-only) and IgD+IgM+ cells, and that together they form the CD27+ compartment of recirculating B cells. We investigated the Ig isotype switch capacity of these cells. Peripheral blood B subsets were sorted and IgG subclass secretion in presence or absence of IL-4 was compared in B cell assays which lead to Ig secretion in all (coculture with EL-4 thymoma cells) or only in CD27+ (CD40L stimulation) B cells. Already switched IgG+ B cells showed no significant sequential switch and IgM-only cells also had a low switch capacity, but IgD+CD27+ switched as much as IgD+CD27- B cells to all IgG subclasses. Thus, in switched B cells some alterations compromising further switch options occur frequently; IgM-only cells may result from aborted switch. However, IgD+CD27+ human B cells, extensively V(D)J mutated and "naive" regarding switch, build up a repertoire of B cells combining (1) novel cross-reactive specificities, (2) increased differentiation capacity (including after T-independent stimulation by Staphylococcus aureus Cowan I) and (3) the capacity to produce appropriate isotypes when they respond to novel pathogens.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

T cells play a primordial role in antiviral immunity. Virus-specific T-cell responses can be characterized by a number of independent variables. These include the magnitude of the response; the functional quality of the response, i.e. the types of cytokines secreted after stimulation and the proliferative or lytic potential; the tissue distribution of the T cells; the breadth of the response; and the avidity of the response. All of these together constitute the T-cell response to antigen (Ag) and comprise potential variables that may correlate with antiviral protective immunity. Substantial advances have recently been obtained in the characterization of virus-specific T-cell responses. These studies have shown that the quality (in term of functional profile) rather than the quantity of Ag-specific T cells was associated with protection. Recently, the term polyfunctional has been used to define T-cell responses that, in addition to typical effector functions such as secretion of IFN-g, TNF-a and MIP-1b and cytotoxic activity, comprise distinct T-cell populations, also able to secrete IL-2 and retaining Ag-specific proliferation capacity. The term \only effector" defines T-cell responses/ populations able to secrete cytokines such as IFN-g, TNF-a and MIP-1b and endowed with cytotoxic activity but lacking IL-2 and proliferation capacity. Several models of virus infections (HIV-1, cytomegalovirus [CMV], Epstein Barr virus [EBV], influenza [Flu] and Herpes Simplex virus) exclusively differentiated on the basis of Ag exposure and persistence, were investigated: 1) antigen clearance, 2) protracted Ag exposure and persistence and low Ag levels, 3) Ag persistence and high Ag levels, and 4) acute Ag exposure/re-exposure. These analyses have demonstrated that polyfunctional and not \only effector" T-cell responses were associated with protective antiviral immunity. However, the factors and mechanisms governing the generation of functionally distinct T-cell populations remain to be elucidated. Recently, several studies have shown a major influence of HLA genotype in the evolution of HIV and the progression of HIV-associated disease. In particular, certain HLA-B alleles were most closely associated with non-progressive disease and low viral load or disease and had a dominant involvement on the clinical course of HIV-associated diseases. In this study, we have investigated the relationship between HLA restriction and the functional profile of Tcell responses in order to determine whether HLA-B influenced the generation of polyfunctional CD8 T-cell responses. To be able to address this issue, we studied CD8 T-cell responses against HIV-1, CMV, EBV and Flu in 128 subjects. These analyses enabled us to demonstrate that HLA-Arestricted epitopes were mostly associated with \only effector" T-cell responses while, in contrast, polyfunctional CD8 T-cell responses were predominantly driven by virus epitopes restricted by HLA-B alleles. We then characterized eventual differences in the responsiveness of CD8 T-cell populations restricted by different HLA-A and HLA-B alleles. For this purpose, we investigated the T-cell receptor (TCR) avidity for the cognate epitope of polyfunctional and \only effector" CD8 T-cell populations. Our results indicated that overall virus-specific CD8 T-cell populations recognizing virus epitopes restricted by HLA-B alleles were equipped with lower avidity TCR for the cognate epitopes when compared to those recognizing epitopes restricted by HLA-A alleles. In conclusion, these results provide the rationale for the observed protective role of HLA-B genotypes in HIV-1- infection and new insights into the relationship between TCR avidity and functional profile of virus-specific CD8 Tcells.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

This paper proposes a managerial control tool that integrates risk in efficiency scores. Building on existing efficiency specifications, our proposal reflects the real banking technology and accurately models the relationship between desirable and undesirable outputs. Specifically, the undesirable output is defined as non-performing loans to capture credit risk, and is linked only to the relevant dimension of the output set. We empirically illustrate how our efficiency measure functions for managerial control purposes. The application considers a unique dataset of Costa Rican banks during 1998-2012. Efficiency scores? implications are mostly discussed at bank-level, and their interpretations are enhanced by using accounting ratios. We also show the usefulness of our tool for corporate governance by examining performance changes around executive turnover. Results confirm that appointing CEOs from outside the bank significantly improves performance, thus suggesting the potential benefits of new organisational practices.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Mitä on läsnäolo? Tämä työ määrittelee läsnäolon tietyn henkilön, laitteen tai palvelun halukkuudeksi kommunikoida. Nykyään on olemassa lukuisia läsnäolotietoa levittäviä sovelluksia, joista jokainen käyttää erilaista protokollaa tehtävän suorittamiseen. Vasta viime aikoina sovellusten kehittäjät ovat huomanneet tarpeen yhdelle sovellukselle, joka kykenee tukemaan lukuisia läsnäoloprotokollia. Session Initiation Protocol (SIP) voi levittää läsnäolotietoa muiden ominaisuuksiensa lisäksi. Kun muita protokollia käytetään vain reaaliaikaiseen viestintään ja läsnäolotiedon lähetykseen, SIP pystyy moniin muihinkin asioihin. Se on alunperin suunniteltu aloittamaan, muuttamaan ja lopettamaan osapuolien välisiä multimediaistuntoja. Arkkitehtuurin toteutus käyttää kahta Symbian –käyttöjärjestelmän perusominaisuutta: asiakas-palvelin rakennetta ja kontaktitietokantaa. Asiakaspalvelin rakenne erottaa asiakkaan protokollasta tarjoten perustan laajennettavalle usean protokollan arkkitehtuurille ja kontaktitietokanta toimii läsnäolotietojen varastona. Työn tuloksena on Symbianin käyttöjärjestelmässä toimiva läsnäoloasiakas.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Improving educational quality is an important public policy goal. However, its success requires identifying factors associated with student achievement. At the core of these proposals lies the principle that increased public school quality can make school system more efficient, resulting in correspondingly stronger performance by students. Nevertheless, the public educational system is not devoid of competition which arises, among other factors, through the efficiency of management and the geographical location of schools. Moreover, families in Spain appear to choose a school on the grounds of location. In this environment, the objective of this paper is to analyze whether geographical space has an impact on the relationship between the level of technical quality of public schools (measured by the efficiency score) and the school demand index. To do this, an empirical application is performed on a sample of 1,695 public schools in the region of Catalonia (Spain). This application shows the effects of spatial autocorrelation on the estimation of the parameters and how these problems are addressed through spatial econometrics models. The results confirm that space has a moderating effect on the relationship between efficiency and school demand, although only in urban municipalities.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The model of Questions Answering (Q&A) for eLearning is based on collaborative learning through questions that are posed by students and their answers to that questions which are given by peers, in contrast with the classical model in which students ask questions to the teacher only. In this proposal we extend the Q&A model including the social presence concept and a quantitative measure of it is proposed; besides it is considered the evolution of the resulting Q&A social network after the inclusion of the social presence and taking into account the feedback on questions posed by students and answered by peers. The social network behaviorwas simulated using a Multi-Agent System to compare the proposed social presence model with the classical and the Q&A models

Relevância:

30.00% 30.00%

Publicador:

Resumo:

One of the main complexities in the simulation of the nonlinear dynamics of rigid bodies consists in describing properly the finite rotations that they may undergo. It is well known that, to avoid singularities in the representation of the SO(3) rotation group, at least four parameters must be used. However, it is computationally expensive to use a four-parameters representation since, as only three of the parameters are independent, one needs to introduce constraint equations in the model, leading to differential-algebraic equations instead of ordinary differential ones. Three-parameter representations are numerically more efficient. Therefore, the objective of this paper is to evaluate numerically the influence of the parametrization and its singularities on the simulation of the dynamics of a rigid body. This is done through the analysis of a heavy top with a fixed point, using two three-parameter systems, Euler's angles and rotation vector. Theoretical results were used to guide the numerical simulation and to assure that all possible cases were analyzed. The two parametrizations were compared using several integrators. The results show that Euler's angles lead to faster integration compared to the rotation vector. An Euler's angles singular case, where representation approaches a theoretical singular point, was analyzed in detail. It is shown that on the contrary of what may be expected, 1) the numerical integration is very efficient, even more than for any other case, and 2) in spite of the uncertainty on the Euler's angles themselves, the body motion is well represented.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Low and high molecular weight kininogens (LK and HK), containing 409 and 626 amino acids with masses of ~65 and 120 kDa after glycosylation, respectively, are coded by a single gene mapped to the human chromosome 3 by alternative splicing of the transcribed mRNA. The NH2-termini Glu1-Thr383 region, identical in LK and HK, contains bradykinin (BK) moieties Arg363-Arg371. LK, HK and their kinin products Lys-BK and BK are involved in several biologic processes. They are evolutionarily conserved and only 7 patients, all apparently normal, have been reported to lack them. In one of these patients (Williams' trait), a codon mutation (Arg178 ® stop) has been blamed for the absence of LK and HK. However, using Western blots with 2 monoclonal anti-HK antibodies, one that recognizes the region common to LK and HK and the other that recognizes only HK, I detected ~110-kDa bands in the plasma of this LK/HK-deficient patient vs ~120-kDa bands in normal human and ape plasmas. With polyclonal anti-Lys-BK antibody, which strongly detects BK cleaved at its COOH-terminus in purified HK, I detected ~110-kDa bands in the normal and the deficient plasmas. Western blots with a monoclonal anti-prekallikrein (PK) antibody showed that surface activation of PK and distribution of PK activation products, both dependent on HK, were similar in these plasmas. These findings suggest that a mutant gene yielded a kininogen-like species possibly involving aberrant mRNA splicing - structurally different from normal HK, but apparently with the capacity to carry out seemingly vital HK functions.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

We detected anti-human small nuclear ribonucleoprotein (snRNP) autoantibodies in chagasic patients by different immunological methods using HeLa snRNPs. ELISA with Trypanosoma cruzi total lysate antigen or HeLa human U small nuclear ribonucleoproteins (UsnRNPs) followed by incubation with sera from chronic chagasic and non-chagasic cardiac patients was used to screen and compare serum reactivity. Western blot analysis using a T. cruzi total cell extract was also performed in order to select some sera for Western blot and immunoprecipitation assays with HeLa nuclear extract. ELISA showed that 73 and 95% of chronic chagasic sera reacted with HeLa UsnRNPs and T. cruzi antigens, respectively. The Western blot assay demonstrated that non-chagasic cardiac sera reacted with high molecular weight proteins present in T. cruzi total extract, probably explaining the 31% reactivity found by ELISA. However, these sera reacted weakly with HeLa UsnRNPs, in contrast to the chagasic sera, which showed autoantibodies with human Sm (from Stefanie Smith, the first patient in whom this activity was identified) proteins (B/B', D1, D2, D3, E, F, and G UsnRNP). Immunoprecipitation reactions using HeLa nuclear extracts confirmed the reactivity of chagasic sera and human UsnRNA/RNPs, while the other sera reacted weakly only with U1snRNP. These findings agree with previously reported data, thus supporting the idea of the presence of autoimmune antibodies in chagasic patients. Interestingly, non-chagasic cardiac sera also showed reactivity with T. cruzi antigen and HeLa UsnRNPs, which suggests that individuals with heart disease of unknown etiology may develop autoimmune antibodies at any time. The detection of UsnRNP autoantibodies in chagasic patients might contribute to our understanding of how they develop upon initial T. cruzi infection.