930 resultados para Mixed Elliptic Problems with Singular Interfaces
Resumo:
Recent sexual health promotion strategies have veered between a negative emphasis on the deleterious consequences of sexually transmitted infections, and a more positive, eroticized approach to safer sex. The differences in approach are starkly reflected in the images chosen to illustrate them. We note that there are problems with both approaches. The main purpose of this review is to demonstrate how this dichotomy was transcended by the sixteenth century Florentine Mannerist painter, Agnolo Bronzino, in his allegory on syphilis
Resumo:
Hypothetical contingent valuation surveys used to elicit values for environmental and other public goods often employ variants of the referendum mechanism due to the cognitive simplicity and familiarity of respondents with this voting format. One variant, the double referendum mechanism, requires respondents to state twice how they would vote for a given policy proposal given their cost of the good. Data from these surveys often exhibit anomalies inconsistent with standard economic models of consumer preferences. There are a number of published explanations for these anomalies, mostly focusing on problems with the second vote. This article investigates which aspects of the hypothetical task affect the degree of nondemand revelation and takes an individual-based approach to identifying people most likely to non-demand reveal. A clear profile emerges from our model of a person who faces a negative surplus i.e. a net loss in the second vote and invokes non self-interested, non financial motivations during the decision process.
Resumo:
It is convenient and effective to solve nonlinear problems with a model that has a linear-in-the-parameters (LITP) structure. However, the nonlinear parameters (e.g. the width of Gaussian function) of each model term needs to be pre-determined either from expert experience or through exhaustive search. An alternative approach is to optimize them by a gradient-based technique (e.g. Newton’s method). Unfortunately, all of these methods still need a lot of computations. Recently, the extreme learning machine (ELM) has shown its advantages in terms of fast learning from data, but the sparsity of the constructed model cannot be guaranteed. This paper proposes a novel algorithm for automatic construction of a nonlinear system model based on the extreme learning machine. This is achieved by effectively integrating the ELM and leave-one-out (LOO) cross validation with our two-stage stepwise construction procedure [1]. The main objective is to improve the compactness and generalization capability of the model constructed by the ELM method. Numerical analysis shows that the proposed algorithm only involves about half of the computation of orthogonal least squares (OLS) based method. Simulation examples are included to confirm the efficacy and superiority of the proposed technique.
Resumo:
The standard approach to the core phenomenology of thought insertion characterizes it in terms of a normal sense of thought ownership coupled with an abnormal sense of thought agency. Recently, Fernández (2010) has argued that there are crucial problems with this approach and has proposed instead that what goes wrong fundamentally in such a phenomenology is a sense of thought commitment, characterized in terms of thought endorsement. In this paper, we argue that even though Fernández raises new issues that enrich the topic, his proposal cannot rival the version of the standard approach we shall defend.
Resumo:
Invasive infection caused by Neisseria meningitidis is a worldwide public health problem. Previous reports have indicated that carriage of common ‘defective’ structural polymorphisms of the host mannose-binding lectin gene (MBL2) greatly increases an individual’s risk of developing the disease. We report the largest case–control study so far to investigate the effect of these polymorphisms in meningococcal disease (296 PCR-positive cases and 5196 population controls, all of European ancestry) and demonstrate that no change in risk is associated with the polymorphisms overall or in any age-defined subgroup. This finding contrasts with two smaller studies that reported an increase in risk. A systematic review of all studies of MBL2 polymorphisms in people of European ancestry published since 1999, including 24 693 individuals, revealed a population frequency of the combined ‘defective’MBL2 allele of 0.230 (95% confidence limits: 0.226–0.234). The past reported associations of increased risk of meningococcal disease were because of low ‘defective’ allele frequencies in their study control populations (0.13 and 0.04) that indicate systematic problems with the studies. The data from our study and all other available evidence indicate that MBL2 structural polymorphisms do not predispose children or adults to invasive meningococcal disease.
Resumo:
We present adaptive optics imaging of the core-collapse supernova (SN) 2009md, which we use together with archival Hubble Space Telescope data to identify a coincident progenitor candidate. We find the progenitor to have an absolute magnitude of V=-4.63+0.3-0.4 mag and a colour of V-I= 2.29+0.25-0.39 mag, corresponding to a progenitor luminosity of log L/L?similar to 4.54 +/- 0.19 dex. Using the stellar evolution code STARS, we find this to be consistent with a red supergiant progenitor with M= 8.5+6.5-1.5 M?. The photometric and spectroscopic evolution of SN 2009md is similar to that of the class of sub-luminous Type IIP SNe; in this paper we compare the evolution of SN 2009md primarily to that of the sub-luminous SN 2005cs. We estimate the mass of 56Ni ejected in the explosion to be (5.4 +/- 1.3) x 10-3 M? from the luminosity on the radioactive tail, which is in agreement with the low 56Ni masses estimated for other sub-luminous Type IIP SNe. From the light curve and spectra, we show the SN explosion had a lower energy and ejecta mass than the normal Type IIP SN 1999em. We discuss problems with stellar evolutionary models, and the discrepancy between low observed progenitor luminosities (log L/L?similar to 4.35 dex) and model luminosities after the second dredge-up for stars in this mass range, and consider an enhanced carbon burning rate as a possible solution. In conclusion, SN 2009md is a faint SN arising from the collapse of a progenitor close to the lower mass limit for core collapse. This is now the third discovery of a low-mass progenitor star producing a low-energy explosion and low 56Ni ejected mass, which indicates that such events arise from the lowest end of the mass range that produces a core-collapse SN (78 M?).
Resumo:
AbstractInvasive infection caused by Neisseria meningitidis is a worldwide public health problem. Previous reports have indicated that carriage of common 'defective' structural polymorphisms of the host mannose-binding lectin gene (MBL2) greatly increases an individual's risk of developing the disease. We report the largest case-control study so far to investigate the effect of these polymorphisms in meningococcal disease (296 PCR-positive cases and 5196 population controls, all of European ancestry) and demonstrate that no change in risk is associated with the polymorphisms overall or in any age-defined subgroup. This finding contrasts with two smaller studies that reported an increase in risk. A systematic review of all studies of MBL2 polymorphisms in people of European ancestry published since 1999, including 24 693 individuals, revealed a population frequency of the combined 'defective'MBL2 allele of 0.230 (95% confidence limits: 0.226-0.234). The past reported associations of increased risk of meningococcal disease were because of low 'defective' allele frequencies in their study control populations (0.13 and 0.04) that indicate systematic problems with the studies. The data from our study and all other available evidence indicate that MBL2 structural polymorphisms do not predispose children or adults to invasive meningococcal disease.
Resumo:
This paper studies single-channel speech separation, assuming unknown, arbitrary temporal dynamics for the speech signals to be separated. A data-driven approach is described, which matches each mixed speech segment against a composite training segment to separate the underlying clean speech segments. To advance the separation accuracy, the new approach seeks and separates the longest mixed speech segments with matching composite training segments. Lengthening the mixed speech segments to match reduces the uncertainty of the constituent training segments, and hence the error of separation. For convenience, we call the new approach Composition of Longest Segments, or CLOSE. The CLOSE method includes a data-driven approach to model long-range temporal dynamics of speech signals, and a statistical approach to identify the longest mixed speech segments with matching composite training segments. Experiments are conducted on the Wall Street Journal database, for separating mixtures of two simultaneous large-vocabulary speech utterances spoken by two different speakers. The results are evaluated using various objective and subjective measures, including the challenge of large-vocabulary continuous speech recognition. It is shown that the new separation approach leads to significant improvement in all these measures.
Resumo:
The qualitative aspects of the Contingent Valuation Method (CVM) are largely ignored by (environmental) economists. This paper aims to instigate a discussion on (a) the usefulness of qualitative data to the contingent valuation process in general; and (b) the use and applicability of the focus group method in particular. We consider the range and uses of focus groups within the CVM and highlight problems with their analysis that have, to date, largely been ignored. A potential solution to circumvent the problem of non-independence of group data is suggested. While there are several distinct and worthwhile uses for qualitative data, focus groups should not automatically be taken as the only or best method to produce these insights even though they are the major one considered in this article. (C) 1999 Elsevier Science B.V. All rights reserved.
Resumo:
The seminal work of Lipset and Rokkan, which explores how party systems evolved organically from nineteenth-century roots, has generally been applied in states which have enjoyed a long-standing territorial identity. Their model's emphasis on stability and predictability can, however, be reconciled with circumstances where the very identity of the state itself is an issue. This article explores the capacity of the model to explain party divisions in three nested contexts: the pre-1922 United Kingdom, which encountered problems with its Celtic peripheries, and especially with Ireland; independent Ireland, where a unique party system developed, largely in response to a broader historical and geographical context; and Northern Ireland, where party politics fossilised in the 1880s, and began to unfreeze only in the 1970s. The article argues that the Lipset–Rokkan model casts valuable light on these processes, which in turn contribute to the theoretical richness of the model.
Resumo:
Objective: Establish maternal preferences for a third-trimester ultrasound scan in a healthy, low-risk pregnant population.
Design: Cross-sectional study incorporating a discrete choice experiment.
Setting: A large, urban maternity hospital in Northern Ireland.
Participants: One hundred and forty-six women in their second trimester of pregnancy.
Methods: A discrete choice experiment was designed to elicit preferences for four attributes of a third-trimester ultrasound scan: health-care professional conducting the scan, detection rate for abnormal foetal growth, provision of non-medical information, cost. Additional data collected included age, marital status, socio-economic status, obstetric history, pregnancy-specific stress levels, perceived health and whether pregnancy was planned. Analysis was undertaken using a mixed logit model with interaction effects.
Main outcome measures: Women's preferences for, and trade-offs between, the attributes of a hypothetical scan and indirect willingness-to-pay estimates.
Results: Women had significant positive preference for higher rate of detection, lower cost and provision of non-medical information, with no significant value placed on scan operator. Interaction effects revealed subgroups that valued the scan most: women experiencing their first pregnancy, women reporting higher levels of stress, an adverse obstetric history and older women.
Conclusions: Women were able to trade on aspects of care and place relative importance on clinical, non-clinical outcomes and processes of service delivery, thus highlighting the potential of using health utilities in the development of services from a clinical, economic and social perspective. Specifically, maternal preferences exhibited provide valuable information for designing a randomized trial of effectiveness and insight for clinical and policy decision makers to inform woman-centred care.
Resumo:
This study investigated the demographic and psychosocial characteristics of patients attending a residential treatment program for children with asthma. Measures of background information and standardized psychosocial variables were administered to 54 inpatients over an 18-month period. Typically, our patients presented with moderate to severe chronic asthma, mostly diagnosed before 3 years of age and often associated with atopic dermatitis. The families exhibited normal levels of emotional bonding and flexibility in response to stress. Psychosocially, most children were experiencing behavioral and school-related problems, with 6-11-year-old boys exhibiting global social competency problems as well. Girls exhibited lower self-esteem. Locus of control was within the normal range for all age groups. Half the children had not previously attended an asthma education program and two-thirds of the family members either smoked and/or had a pet. The treatment implications of these characteristics of our asthma population were considered.
Resumo:
Molecular genetic assays for the detection of the JAK2 V617F (c.1849G>T) and other pathogenetic mutations within JAK2 exon 12 and MPL exon 10 are part of the routine diagnostic workup for patients presenting with erythrocytosis, thrombocytosis or otherwise suspected to have a myeloproliferative neoplasm. A wide choice of techniques are available for the detection of these mutations, leading to potential difficulties for clinical laboratories in deciding upon the most appropriate assay, which can lead to problems with inter-laboratory standardization. Here, we discuss the most important issues for a clinical diagnostic laboratory in choosing a technique, particularly for detection of the JAK2 V617F mutation at diagnosis. The JAK2 V617F detection assay should be both specific and sensitive enough to detect a mutant allele burden as low as 13%. Indeed, the use of sensitive assays increases the detection rate of the JAK2 V617F mutation within myeloproliferative neoplasms. Given their diagnostic relevance, it is also beneficial and relatively straightforward to screen JAK2 V617F negative patients for JAK2 exon 12 mutations (in the case of erythrocytosis) or MPL exon 10 mutations (thrombocytosis or myelofibrosis) using appropriate assays. Molecular results should be considered in the context of clinical findings and other haematological or laboratory results.
Resumo:
An evolution in theoretical models and methodological paradigms for investigating cognitive biases in the addictions is discussed. Anomalies in traditional cognitive perspectives, and problems with the self-report methods which underpin them, are highlighted. An emergent body of cognitive research, contextualized within the principles and paradigms of cognitive neuropsychology rather than social learning theory, is presented which, it is argued, addresses these anomalies and problems. Evidence is presented that biases in the processing of addiction-related stimuli, and in the network of propositions which motivate addictive behaviours, occur at automatic, implicit and pre-conscious levels of awareness. It is suggested that methods which assess such implicit cognitive biases (e.g. Stroop, memory, priming and reaction-time paradigms) yield findings which have better predictive utility for ongoing behaviour than those biases determined by self-report methods of introspection. The potential utility of these findings for understanding "loss of control" phenomena, and the desynchrony between reported beliefs and intentions and ongoing addictive behaviours, is discussed. Applications to the practice of cognitive therapy are considered.
Resumo:
Conflicting results have been reported on the detection of paramyxovirus transcripts in Paget's disease, and a possible explanation is differences in the sensitivity of RT-PCR methods for detecting virus. In a blinded study, we found no evidence to suggest that laboratories that failed to detect viral transcripts had less sensitive RT-PCR assays, and we did not detect measles or distemper transcripts in Paget's samples using the most sensitive assays evaluated.
Introduction: There is conflicting evidence on the possible role of persistent paramyxovirus infection in Paget's disease of bone (PDB). Some workers have detected measles virus (MV) or canine distemper virus (CDV) transcripts in cells and tissues from patients with PDB, but others have failed to confirm this finding. A possible explanation might be differences in the sensitivity of RT-PCR methods for detecting virus. Here we performed a blinded comparison of the sensitivity of different RT-PCR-based techniques for MV and CDV detection in different laboratories and used the most sensitive assays to screen for evidence of viral transcripts in bone and blood samples derived from patients with PDB.
Materials and Methods: Participating laboratories analyzed samples spiked with known amounts of MV and CDV transcripts and control samples that did not contain viral nucleic acids. All analyses were performed on a blinded basis.
Results: The limit of detection for CDV was 1000 viral transcripts in three laboratories (Aberdeen, Belfast, and Liverpool) and 10,000 transcripts in another laboratory (Manchester). The limit of detection for MV was 16 transcripts in one laboratory (NIBSC), 1000 transcripts in two laboratories (Aberdeen and Belfast), and 10,000 transcripts in two laboratories (Liverpool and Manchester). An assay previously used by a U.S.-based group to detect MV transcripts in PDB had a sensitivity of 1000 transcripts. One laboratory (Manchester) detected CDV transcripts in a negative control and in two samples that had been spiked with MV. None of the other laboratories had false-positive results for MV or CDV, and no evidence of viral transcripts was found on analysis of 12 PDB samples using the most sensitive RT-PCR assays for MV and CDV.
Conclusions: We found that RT-PCR assays used by different laboratories differed in their sensitivity to detect CDV and MV transcripts but found no evidence to suggest that laboratories that previously failed to detect viral transcripts had less sensitive RT-PCR assays than those that detected viral transcripts. False-positive results were observed with one laboratory, and we failed to detect paramyxovirus transcripts in PDB samples using the most sensitive assays evaluated. Our results show that failure of some laboratories to detect viral transcripts is unlikely to be caused by problems with assay sensitivity and highlight the fact that contamination can be an issue when searching for pathogens by sensitive RT-PCR-based techniques.