436 research outputs found
The One Loop Effective Super-Potential and Non-Holomorphicity
We calculate the Kahlerian and the lowest order non-Kahlerian contributions
to the one loop effective superpotential using super-Feynman graphs in the
massless Wess-Zumino Model, the massive Wess-Zumino Model and N=1, U(1) gauge
theory. We also calculate the Kahlerian term in Yang-Mills Theory for a general
gauge group. Using this latter result we find the one loop Kahlerian
contribution for N=2 Yang-Mills Theory in terms of N=1 superfields and we show
that it can only come from non-holomorphic contributions to the N=2 effective
potential.Comment: LaTeX, 10 pages, 7 figures, uses bezier.sty and ifthen.sty. First
amendment. The results are extended to include the Kahlerian term for a
general renormalisable N=1 supersymmetric theory, containing Wess-Zumino and
Yang-Mills multiplets with a cubic superpotential. One reference has been
changed and one has been added. Second amendment. One acknowledgment has been
altered in the `note added in proof
Superstring Theory on AdS_2 x S^2 as a Coset Supermanifold
We quantize the superstring on the AdS_2 x S^2 background with Ramond-Ramond
flux using a PSU(1,1|2)/U(1) x U(1) sigma model with a WZ term. One-loop
conformal invariance of the model is guaranteed by a general mechanism which
holds for coset spaces G/H where G is Ricci-flat and H is the invariant locus
of a Z_4 automorphism of G. This mechanism gives conformal theories for the
PSU(1,1|2) x PSU(2|2)/SU(2) x SU(2) and PSU(2,2|4)/SO(4,1) x SO(5) coset
spaces, suggesting our results might be useful for quantizing the superstring
on AdS_3 x S^3 and AdS_5 x S^5 backgrounds.Comment: 34 pages, 4 figures, harvmac big mode ; typos corrected, clarified
the choice of the real form
Phonons from neutron powder diffraction
The spherically averaged structure function \soq obtained from pulsed
neutron powder diffraction contains both elastic and inelastic scattering via
an integral over energy. The Fourier transformation of \soq to real space, as
is done in the pair density function (PDF) analysis, regularizes the data, i.e.
it accentuates the diffuse scattering. We present a technique which enables the
extraction of off-center phonon information from powder diffraction experiments
by comparing the experimental PDF with theoretical calculations based on
standard interatomic potentials and the crystal symmetry. This procedure
(dynamics from powder diffraction(DPD)) has been successfully implemented for
two systems, a simple metal, fcc Ni, and an ionic crystal, CaF. Although
computationally intensive, this data analysis allows for a phonon based
modeling of the PDF, and additionally provides off-center phonon information
from powder neutron diffraction
Reply to "Comment on 'Dynamic Peierls-Nabarro equations for elastically isotropic crystals' "
The Comment by Markenscoff that criticizes a recent dynamic extension of the
Peierls-Nabarro equation [Y.-P. Pellegrini, Phys. Rev. B 81, 024101 (2010)] is
refuted by means of simple examples that illustrate the interest of using an
approach based on generalized functions to compute dynamic stress fields.Comment: 4 pages, 1 figur
Lower cardiorespiratory fitness contributes to increased insulin resistance and fasting glycaemia in middle-aged South Asian compared with European men living in the UK
AIMS/HYPOTHESIS: This study aimed to determine the extent to which increased insulin resistance and fasting glycaemia in South Asian men, compared with white European men, living in the UK, was due to lower cardiorespiratory fitness (maximal oxygen uptake [[Formula: see text]]) and physical activity. METHODS: One hundred South Asian and 100 age- and BMI-matched European men without diagnosed diabetes, aged 40–70 years, had fasted blood taken for measurement of glucose concentration, HOMA-estimated insulin resistance (HOMA(IR)), plus other risk factors, and underwent assessment of physical activity (using accelerometry), [Formula: see text], body size and composition, and demographic and other lifestyle factors. For 13 South Asian and one European man, HbA(1c) levels were >6.5% (>48 mmol/mol), indicating potential undiagnosed diabetes; these men were excluded from the analyses. Linear regression models were used to determine the extent to which body size and composition, fitness and physical activity variables explained differences in HOMA(IR) and fasting glucose between South Asian and European men. RESULTS: HOMA(IR) and fasting glucose were 67% (p < 0.001) and 3% (p < 0.018) higher, respectively, in South Asians than Europeans. Lower [Formula: see text], lower physical activity and greater total adiposity in South Asians individually explained 68% (95% CI 45%, 91%), 29% (11%, 46%) and 52% (30%, 80%), respectively, and together explained 83% (50%, 119%) (all p < 0.001) of the ethnic difference in HOMA(IR). Lower [Formula: see text] and greater total adiposity, respectively, explained 61% (9%, 111%) and 39% (9%, 76%) (combined effect 63% [8%, 115%]; all p < 0.05) of the ethnic difference in fasting glucose. CONCLUSIONS/INTERPRETATION: Lower cardiorespiratory fitness is a key factor associated with the excess insulin resistance and fasting glycaemia in middle-aged South Asian, compared with European, men living in the UK. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s00125-013-2969-y) contains peer-reviewed but unedited supplementary material, which is available to authorised users
ICF-based Functional Components and Contextual Factors as Correlates of Perceived Quality of Life for Youth With Chronic Conditions
Purpose: To explore International Classification of Functioning, Disability and Health (ICF)-based functional components and contextual factors associated with perceived quality of life (QOL) for youth with chronic conditions from the perspective of youth and parents.
Method: Baseline data were obtained from a longitudinal study examining predictors of changes in perceived QOL for youth with chronic conditions. 439 youth aged 11–17 (and one of their parents) completed a questionnaire. Standardized tools were used to measure youth functioning, contextual factors and perceived QOL. Multivariate linear regression analyses, controlling for socio-demographic and health information, were conducted to explore correlations among youth functioning/contextual factors and youth and parent perceptions of youth QOL. Results: Significant (p0.05) negative correlates with both youth and parent perceptions of youth QOL included pain/other physical symptoms and emotional symptoms. Significant factors positively correlated with youth and parent perceptions of youth QOL included school productivity and spirituality. Other significant positive correlates of youth perspectives were family social support and school belongingness/safety. Family functioning was positively correlated, and youth social anxiety and environmental barriers were negatively correlated, with parent perceptions of youth QOL.
Conclusions: This study provides preliminary evidence of factors upon which services aimed at improving perceived QOL of youth with chronic conditions could be based
Elevated reticulocyte count – a clue to the diagnosis of haemolytic-uraemic syndrome (HUS) associated with gemcitabine therapy for metastatic duodenal papillary carcinoma: a case report
In adults, the haemolytic-uraemic syndrome (HUS) is associated with probable causative factors in the minority of all cases. Cytotoxic drugs are one of these potential causative agents. Although metastatic cancer by itself is a recognized risk-factor for the development of HUS, therapy with mitomycin-C, with cis-platinum, and with bleomycin carries a significant, albeit extremely small, risk for the development of HUS, compared with all other cytotoxic drugs. Gemcitabine is a novel cytotoxic drug with promising activity against pancreatic adenocarcinoma. We are reporting on one patient with metastatic duodenal papillary carcinoma developing HUS while on weekly gemcitabine therapy. The presenting features in this patient were non-cardiac pulmonary oedema, renal failure, thrombocytopenia and haemolytic anaemia. The diagnosis of HUS was made on the day of admission of the patient to this institution. Upon aggressive therapy, including one single haemodialysis and five plasmaphereses, the patient recovered uneventfully, with modestly elevated creatinine-values as a remnant of the acute illness. Re-exposure to gemcitabine 6 months after the episode of HUS instituted for progressive carcinoma, thus far has not caused another episode of HUS. © 1999 Cancer Research Campaig
Early onset cannabis use and progression to other drug use in a sample of Dutch twins
One possible explanation of the commonly reported associations between early onset cannabis use and elevated risks of other illicit drug use is that early onset cannabis use increases access and availability to other drugs. It was this argument that in part motivated policy changes in the Netherlands that led to the de facto legalization of cannabis there. This study examines, using a co-twin control design, whether previously observed associ- ations between early onset cannabis use and elevated lifetime rates of other illicit drug use would also be observed in a sample of 219 same sex Dutch twin pairs discordant for cannabis use before age 18. After adjustment for covariates, rates of lifetime party drug use (OR = 7.4, 95% CI = 2.3-23.4), hard drug use (OR = 16.5, 95% CI = 2.4-111.3), but not regular cannabis use (OR= 1.3, 95% CI = 0.3-5.1) were significantly elevated in individuals who reported early onset cannabis use, relative to their co-twin who had not used cannabis by age 18. The elevated odds of subsequent illicit drug use in early cannabis users relative to their non early using cotwins suggests that this association could not be explained by common familial risk factors, either genetic or environmental, for which our co-twin methodology provided rigorous control. © 2006 Springer Science+Business Media, Inc
A telephone survey of parental attitudes and behaviours regarding teenage drinking
<p>Abstract</p> <p>Background</p> <p>Irish teenagers demonstrate high rates of drunkenness and there has been a progressive fall in age of first drinking in recent decades. International research indicates that parents exert substantial influence over their teenager's drinking. We sought to determine the attitudes and behaviours of Irish parents towards drinking by their adolescent children.</p> <p>Methods</p> <p>We conducted a telephone survey of a representative sample of of 234 parents who had a teenager aged between 13 and 17 years.</p> <p>Results</p> <p>Six per cent reported that they would be unconcerned if their son or daughter was to binge drink once per month. On the issue of introducing children to alcohol in the home, 27% viewed this as a good idea while 63% disagreed with this practice. Eleven per cent of parents reported that they had given a drink to their teenager at home. Parents who drank regularly themselves, who were from higher socio-demographic groups and who lived in the east of Ireland demonstrated more permissive attitudes to teenage drinking.</p> <p>Conclusions</p> <p>We found no evidence of widespread permissive attitudes and behaviours among Irish parents. Given that parental influences have been demonstrated to exert substantial impact on teenage drinking, it may be possible to harness the concerns of Irish parents more effectively to reverse the trends of escalating alcohol related harm in Ireland.</p
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