3,622 research outputs found
Moyal star product approach to the Bohr-Sommerfeld approximation
The Bohr-Sommerfeld approximation to the eigenvalues of a one-dimensional
quantum Hamiltonian is derived through order (i.e., including the
first correction term beyond the usual result) by means of the Moyal star
product. The Hamiltonian need only have a Weyl transform (or symbol) that is a
power series in , starting with , with a generic fixed point in
phase space. The Hamiltonian is not restricted to the kinetic-plus-potential
form. The method involves transforming the Hamiltonian to a normal form, in
which it becomes a function of the harmonic oscillator Hamiltonian.
Diagrammatic and other techniques with potential applications to other normal
form problems are presented for manipulating higher order terms in the Moyal
series.Comment: 27 pages, no figure
Discovering a junction tree behind a Markov network by a greedy algorithm
In an earlier paper we introduced a special kind of k-width junction tree,
called k-th order t-cherry junction tree in order to approximate a joint
probability distribution. The approximation is the best if the Kullback-Leibler
divergence between the true joint probability distribution and the
approximating one is minimal. Finding the best approximating k-width junction
tree is NP-complete if k>2. In our earlier paper we also proved that the best
approximating k-width junction tree can be embedded into a k-th order t-cherry
junction tree. We introduce a greedy algorithm resulting very good
approximations in reasonable computing time.
In this paper we prove that if the Markov network underlying fullfills some
requirements then our greedy algorithm is able to find the true probability
distribution or its best approximation in the family of the k-th order t-cherry
tree probability distributions. Our algorithm uses just the k-th order marginal
probability distributions as input.
We compare the results of the greedy algorithm proposed in this paper with
the greedy algorithm proposed by Malvestuto in 1991.Comment: The paper was presented at VOCAL 2010 in Veszprem, Hungar
Identification of the factors associated with outcomes in a condition management programme
<p>Background: A requirement of the Government’s Pathways to Work (PtW) agenda was to introduce a Condition Management Programme (CMP). The aim of the present study was to identify the differences between those who engaged and made progress in this telephone-based biopsychosocial intervention, in terms of their health, and those who did not and to determine the client and practitioner characteristics and programme elements associated with success in a programme aimed at improving health.</p>
<p>Methods: Data were obtained from the CMP electronic spreadsheets and clients paper-based case records. CMP
standard practice was that questionnaires were administered during the pre- and post-assessment phases over the
telephone. Each client’s record contains their socio-demographic data, their primary health condition, as well as the pre- and post-intervention scores of the health assessment tool administered. Univariate and multivariate statistical analysis was used to investigate the relationships between the database variables. Clients were included in the study if their records were available for analysis from July 2006 to December 2007.</p>
<p> Results: On average there were 112 referrals per month, totalling 2016 referrals during the evaluation period. The
majority (62.8%) of clients had a mental-health condition. Successful completion of the programme was 28.5% (575
“completers”; 144 “discharges”). Several factors, such as age, health condition, mode of contact, and practitioner
characteristics, were significant determinants of participation and completion of the programme. The results
showed that completion of the CMP was associated with a better mental-health status, by reducing the number of
clients that were either anxious, depressed or both, before undertaking the programme, from 74% to 32.5%.</p>
<p>Conclusions: Our findings showed that an individual's characteristics are associated with success in the
programme, defined as completing the intervention and demonstrating an improved health status. This study
provides some evidence that the systematic evaluation of such programmes and interventions could identify ways
in which they could be improved.</p>
GOLPH2 expression may serve as diagnostic marker in seminomas
ABSTRACT: BACKGROUND: GOLPH2 (Golgi phosphoprotein 2) is a novel Golgi membrane protein. Despite its unknown physiologic function, however, it has been proposed as a biomarker for hepatocellular and prostate carcinoma due to its upregulation in those cancer entities. Whether the overexpression of GOLPH2 is tumour specific or a generic parameter of malignancy and whether this finding is true for additional carcinomas has not been determined. In this study, we aimed to evaluate the expression pattern of GOLPH2 in testicular seminomas, the most common histologic subtype of testicular neoplasm. METHODS: GOLPH2 protein expression was assessed by immunohistochemistry in 69 testicular seminomas and compared to the expression rates in matching normal testicular tissue and intratubular germ cell neoplasia of unclassified type (IGCNU). In addition, a subset of Leydig cell tumours was analyzed accordingly. RESULTS: GOLPH2 was consistently overexpressed (89.9%) in seminomas. Matching non-neoplastic tissue showed weak or negative staining. The observed differences between non-neoplastic and neoplastic tissue were statistically highly significant (p < 0.001). There were no significant associations with tumour status. Interestingly, GOLPH2 was also highly expressed in the intertubular Leydig cells as well as in Leydig cell tumours. CONCLUSIONS: GOLPH2 protein is highly expressed in seminomas and in Leydig cell tumours. This study fosters the association of GOLPH2 with malignant neoplastic processes. The staining pattern is easily assessable and consistent which is a favourable property especially in clinical settings. GOLPH2 could be a novel immunohistochemical marker for the assessment of testicular neoplasms, especially against the background that in analogy to hepatocellular carcinomas complementary GOLPH2 serum levels might be helpful in detecting metastases or recurrent tumour. Therefore serum studies and analyses of GOLPH2 expression in non-seminomatous germ cell tumours are strongly warranted
HIGGS PHENOMENOLOGY OF THE SUPERSYMMETRIC MODEL WITH A GAUGE SINGLET
We discuss the Higgs sector of the supersymmetric standard model extended by
a gauge singlet for the range of parameters, which is compatible with universal
soft supersymmetry breaking terms at the GUT scale. We present results for the
masses, couplings and decay properties of the lightest Higgs bosons, in
particular with regard to Higgs boson searches at LEP. The prospects differ
significantly from the ones within the MSSM.Comment: 12 pages (Plain Tex), 7 fig
Cost-effectiveness of introducing a rotavirus vaccine in developing countries: The case of Mexico
<p>Abstract</p> <p>Background</p> <p>In developing countries rotavirus is the leading cause of severe diarrhoea and diarrhoeal deaths in children under 5. Vaccination could greatly alleviate that burden, but in Mexico as in most low- and middle-income countries the decision to add rotavirus vaccine to the national immunisation program will depend heavily on its cost-effectiveness and affordability. The objective of this study was to assess the cost-effectiveness of including the pentavalent rotavirus vaccine in Mexico's national immunisation program.</p> <p>Methods</p> <p>A cost-effectiveness model was developed from the perspective of the health system, modelling the vaccination of a hypothetical birth cohort of 2 million children monitored from birth through 60 months of age. It compares the cost and disease burden of rotavirus in an unvaccinated cohort of children with one vaccinated as recommended at 2, 4, and 6 months.</p> <p>Results</p> <p>Including the pentavalent vaccine in the national immunisation program could prevent 71,464 medical visits (59%), 5,040 hospital admissions (66%), and 612 deaths from rotavirus gastroenteritis (70%). At US13.70 per 3-dose regimen, vaccination would cost US4,383 per discounted life-year saved, at a total net cost of US15 per dose, the cost per life-year saved is estimated to be lower than one GNP per capita and hence highly cost effective by the WHO Commission on Macroeconomics and Health criteria. The cost-effectiveness estimates are highly dependent upon the mortality in the absence of the vaccine, which suggests that the vaccine is likely to be significantly more cost-effective among poorer populations and among those with less access to prompt medical care – such that poverty reduction programs would be expected to reduce the future cost-effectiveness of the vaccine.</p
Mitral valve prolapse associated with celiac artery stenosis: a new ultrasonographic syndrome?
BACKGROUND: Celiac artery stenosis (CAS) may be caused by atherosclerotic degeneration or compression exerted by the arched ligament of the diaphragm. Mitral valve prolapse (MVP) is the most common valvular disorder. There are no reports on an association between CAS and MVP. METHODS: 1560 (41%) out of 3780 consecutive patients undergoing echocardiographic assessment of MVP, had Doppler sonography of the celiac tract to detect CAS. RESULTS: CAS was found in 57 (3.7%) subjects (23 males and 34 females) none of whom complained of symptoms related to visceral ischemia. MVP was observed in 47 (82.4%) subjects with and 118 (7.9%) without CAS (p < 0.001). The agreement between MVP and CAS was 39% (95% CI 32–49%). PSV (Peak Systolic Velocity) was the only predictor of CAS in MPV patients (OR 0.24, 95% CI 0.08–0.69) as selected in a multivariate logistic model. CONCLUSION: CAS and MVP seem to be significantly associated in patients undergoing consecutive ultrasonographic screening
Self-Organization of Anastral Spindles by Synergy of Dynamic Instability, Autocatalytic Microtubule Production, and a Spatial Signaling Gradient
Assembly of the mitotic spindle is a classic example of macromolecular self-organization. During spindle assembly, microtubules (MTs) accumulate around chromatin. In centrosomal spindles, centrosomes at the spindle poles are the dominating source of MT production. However, many systems assemble anastral spindles, i.e., spindles without centrosomes at the poles. How anastral spindles produce and maintain a high concentration of MTs in the absence of centrosome-catalyzed MT production is unknown. With a combined biochemistry-computer simulation approach, we show that the concerted activity of three components can efficiently concentrate microtubules (MTs) at chromatin: (1) an external stimulus in form of a RanGTP gradient centered on chromatin, (2) a feed-back loop where MTs induce production of new MTs, and (3) continuous re-organization of MT structures by dynamic instability. The mechanism proposed here can generate and maintain a dissipative MT super-structure within a RanGTP gradient
Animal abuse and intimate partner violence: researching the link and its significance in Ireland - a veterinary perspective
Research on domestic violence has established a substantial association between intimate partner abuse and the abuse of children within the home. It is only recently however, that researchers have demonstrated the correlation between non-accidental injury in animals, and abuse of women by their intimate male partners. A growing body of evidence suggests that animal abuse can be an early indicator for other forms of violent behaviour. This research includes the responses of a sample of 23 women using refuge services in the Republic of Ireland. It investigates the connection between domestic violence and animal abuse, and ascertains if there is sufficient support service for animals and people relevant to domestic abuse. In the survey population, 57% of women reported witnessing one or more forms of abuse, or threats of abuse, of their pets. Five of which were reported to have resulted in the death of the pet. Eighty seven per cent of women felt a facility to accommodate pets would have made their decision to leave the family home easier. Four women disclosed that lack of such a service and concern for the welfare of their companion animals caused them to remain in their abusive relationships for longer than they felt appropriate. Nine families placed pets in the care of family or friends, one woman is unaware of the fate of her pet, while the pets of six families remained with the abusive male after his partner entered a refuge. The majority of women felt unable to talk to anyone about their fears for their pets' welfare. Many felt that there is no service which can provide temporary accommodation for womens' pets while they are in refuge. The results obtained support those found elsewhere in larger studies in the USA and UK, and demonstrate an association of animal abuse in households where there is reported domestic violence
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