596 research outputs found
Spin Correlations in Pair Creation by Two-Photons and Entanglement in QED
Spin correlations of pair productions of two colliding photons
are investigated and explicit expressions for their corresponding probabilities
are derived and found to be \textit{energy} (speed) dependent, for initially
\textit{linearly} and \textit{circularly polarized} photons, different from
those obtained by simply combining the spins of the relevant particles, for
initially \textit{polarized} photons. These expressions also depend on the
angles of spin of (and/or of ), for initially {\it linearly
polarized} photons, but not for {\it circularly polarized} photons, as a
function of the energy. It is remarkable that these explicit results obtained
from quantum field theory show a clear violation of Bell's inequality of Local
Hidden Variables theories at all {\it energies} beyond that of the threshold
one for particle production, in support of quantum field theory in the
relativistic regime. We hope that our explicit expression will lead to
experiments, of the type described in the bulk of this paper, which can monitor
energy (and speed) in polarization correlation experiments.Comment: 12 pages, 4 figure
Action Principle and Algebraic Approach to Gauge Transformations in Gauge Theories
The action principle is used to derive, by an entirely algebraic approach,
gauge transformations of the full vacuum-to-vacuum transition amplitude
(generating functional) from the Coulomb gauge to arbitrary covariant gauges
and in turn to the celebrated Fock-Schwinger (FS) gauge for the abelian (QED)
gauge theory without recourse to path integrals or to commutation rules and
without making use of delta functionals. The interest in the FS gauge, in
particular, is that it leads to Faddeev-Popov ghosts-free non-abelian gauge
theories. This method is expected to be applicable to non-abelian gauge
theories including supersymmetric ones.Comment: LaTeX, 12 pages, Corrected typo
Glycogen synthase kinase 3, circadian rhythms, and bipolar disorder: a molecular link in the therapeutic action of lithium
BACKGROUND: Bipolar disorder (BPD) is a widespread condition characterized by recurring states of mania and depression. Lithium, a direct inhibitor of glycogen synthase kinase 3 (GSK3) activity, and a mainstay in BPD therapeutics, has been proposed to target GSK3 as a mechanism of mood stabilization. In addition to mood imbalances, patients with BPD often suffer from circadian disturbances. GSK3, an essential kinase with widespread roles in development, cell survival, and metabolism has been demonstrated to be an essential component of the Drosophila circadian clock. We sought to investigate the role of GSK3 in the mammalian clock mechanism, as a possible mediator of lithium's therapeutic effects. METHODS: GSK3 activity was decreased in mouse embryonic fibroblasts (MEFs) genetically and pharmacologically, and changes in the cyclical expression of core clock genes – mPer2 in particular – were examined. RESULTS: We demonstrate that genetic depletion of GSK3 in synchronized oscillating MEFs results in a significant delay in the periodicity of the endogenous clock mechanism, particularly in the cycling period of mPer2. Furthermore, we demonstrate that pharmacological inhibition of GSK3 activity by kenpaullone, a known antagonist of GSK3 activity, as well as by lithium, a direct inhibitor of GSK3 and the most common treatment for BPD, induces a phase delay in mPer2 transcription that resembles the effect observed with GSK3 knockdown. CONCLUSION: These results confirm GSK3 as a plausible target of lithium action in BPD therapeutics, and suggest the circadian clock mechanism as a significant modulator of lithium's clinical benefits
A large de novo 9p21.3 deletion in a girl affected by astrocytoma and multiple melanoma.
BACKGROUND: Association of melanoma, neural system tumors and germ line mutations at the 9p21 region in the CDKN2A, CDKN2B and CDKN2BAS genes has been reported in a small number of families worldwide and described as a discrete syndrome in melanoma families registered as a rare disease, the melanoma–astrocytoma syndrome. CASE PRESENTATION: We here studied two young patients developing melanoma after radiotherapy for astrocytoma, both reporting lack of family history for melanoma or neural system tumors at genetic counselling. Patient A is a girl treated for anaplastic astrocytoma at 10 years and for multiple melanomas on the scalp associated to dysplastic nevi two years later. Her monozygotic twin sister carried dysplastic nevi and a slow growing, untreated cerebral lesion. Direct sequencing analysis showed no alterations in melanoma susceptibility genes including CDKN2A, CDK4, MC1R and MITF or in TP53. By microsatellite analysis, multiplex ligation-dependent probe amplification, and array comparative genomic hybridization a deletion including the CDKN2A, CDKN2B and CDKN2BAS gene cluster was detected in both twin sisters, encompassing a large region at 9p21.3 and occurring de novo after the loss of one paternal allele. Patient B is a boy of 7 years when treated for astrocytoma then developing melanoma associated to congenital nevi on the head 10 years later: sequencing and multiplex ligation-dependent probe amplification revealed a normal profile of the CDKN2A/CDKN2B/CDKN2BAS region. Array comparative genomic hybridization confirmed the absence of deletions at 9p21.3 and failed to reveal known pathogenic copy number variations. CONCLUSIONS: By comparison with the other germ line deletions at the CDKN2A, CDKN2B and CDKN2BAS gene cluster reported in melanoma susceptible families, the deletion detected in the two sisters is peculiar for its de novo origin and for its extension, as it represents the largest constitutive deletion at 9p21.3 region identified so far. In addition, the two studied cases add to other evidence indicating association of melanoma with exposure to ionizing radiation and with second neoplasm after childhood cancer. Melanoma should be considered in the monitoring of pigmented lesions in young cancer patients
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Wind Resource Development Project for Armenia
Armenia has few proven reserves of natural energy and is dependent on long, unreliable transport lines for oil and gas. Preliminary studies indicate that the wind energy potential in Armenia is more than 500 megawatts (MW), assuming a reasonable fraction of 10% of the land area in the high-wind zones. Over the long term, the Armenian government intends to meet 8%--10% of its electric consumption needs by grid-connected wind turbines. The goals of this project are to enhance Armenia's energy security, mitigate the environmental damage of conventional sources of energy, reduce future carbon dioxide emissions, build an environmentally sound and sustainable model for economic development, and promote trade between the U.S. and Armenia. The project is being funded by the Cafesjian Family Foundation, a private foundation based in the United States in Naples, Florida, with the participation of Ecotrade, Inc. of Glendale, California. The National Renewable Energy Laboratory (NREL) is providing technical assistance. As part of the wind energy development project, the authors conducted a preliminary wind-energy resource assessment for some regions in Armenia. This activity provided valuable information needed to facilitate the commercialization of wind farms in Armenia and to lay the groundwork for subsequent wind resource activities. This paper presents the wind resource monitoring results (1999--2000) for the candidate site. Preliminary assessment identified areas with good-to-excellent wind resource potential
Scattering of two-level atoms by delta lasers: Exactly solvable models in atom optics
We study the scattering of two-level atoms at narrow laser fields, modeled by
a -shape intensity profile. The unique properties of these potentials
allow us to give simple analytic solutions for one or two field zones. Several
applications are studied: a single -laser may serve as a detector model
for atom detection and arrival-time measurements, either by means of
fluorescence or variations in occupation probabilities. We show that, in
principle, this ideal detector can measure the particle density, the quantum
mechanical flux, arrival time distributions or local kinetic energy densities.
Moreover, two spatially separated -lasers are used to investigate
quantized-motion effects on Ramsey interferometry.Comment: 11 pages, 5 figure
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Rapid progression of prostate cancer in men with a BRCA2 mutation.
Men with BRCA2 mutations have been found to be at increased risk of developing prostate cancer. There is a recent report that BRCA2 carriers with prostate cancer have poorer survival than noncarrier prostate cancer patients. In this study, we compared survival of men with a BRCA2 mutation and prostate cancer with that of men with a BRCA1 mutation and prostate cancer. We obtained the age at diagnosis, age at death or current age from 182 men with prostate cancer from families with a BRCA2 mutation and from 119 men with prostate cancer from families with a BRCA1 mutation. The median survival from diagnosis was 4.0 years for men with a BRCA2 mutation vs 8.0 years for men with a BRCA1 mutation, and the difference was highly significant (P<0.01). It may be important to develop targeted chemotherapies to treat prostate cancer in men with a BRCA2 mutation
Clinical and pathologic characteristics of BRCA-positive and BRCA-negative male breast cancer patients: results from a collaborative multicenter study in Italy
Recently, the number of studies on male breast cancer (MBC) has been increasing. However, as MBC is a rare disease there are difficulties to undertake studies to identify specific MBC subgroups. At present, it is still largely unknown whether BRCA-related breast cancer (BC) in men may display specific characteristics as it is for BRCA-related BC in women. To investigate the clinical-pathologic features of MBC in association with BRCA mutations we established a collaborative Italian Multicenter Study on MBC with the aim to recruit a large series of MBCs. A total of 382 MBCs, including 50 BRCA carriers, were collected from ten Italian Investigation Centres covering the whole country. In MBC patients, BRCA2 mutations were associated with family history of breast/ovarian cancer (p < 0.0001), personal history of other cancers (p = 0.044) and contralateral BC (p = 0.001). BRCA2-associated MBCs presented with high tumor grade (p = 0.001), PR- (p = 0.026) and HER2+ (p = 0.001) status. In a multivariate logistic model BRCA2 mutations showed positive association with personal history of other cancers (OR 11.42, 95 % CI 1.79-73.08) and high tumor grade (OR 4.93, 95 % CI 1.02-23.88) and inverse association with PR+ status (OR 0.19, 95 % CI 0.04-0.92). Based on immunohistochemical (IHC) profile, four molecular subtypes of MBC were identified. Luminal A was the most common subtype (67.7 %), luminal B was observed in 26.5 % of the cases and HER2 positive and triple negative were represented by 2.1 % and 3.7 % of tumors, respectively. Intriguingly, we found that both luminal B and HER2 positive subtypes were associated with high tumor grade (p = 0.003 and 0.006, respectively) and with BRCA2 mutations (p = 0.016 and 0.001, respectively). In conclusion, our findings indicate that BRCA2-related MBCs represent a subgroup of tumors with a peculiar phenotype characterized by aggressive behavior. The identification of a BRCA2-associated phenotype might define a subset of MBC patients eligible for personalized clinical management
Common health assets protocol: a mixed-methods, realist evaluation and economic appraisal of how community-led organisations (CLOs) impact on the health and well-being of people living in deprived areas
Introduction:
This research investigates how community-led organisations’ (CLOs’) use of assets-based approaches improves health and well-being, and how that might be different in different contexts. Assets-based approaches involve ‘doing with’ rather than ‘doing to’ and bring people in communities together to achieve positive change using their own knowledge, skills and experience. Some studies have shown that such approaches can have a positive effect on health and well-being. However, research is limited, and we know little about which approaches lead to which outcomes and how different contexts might affect success.
Methods and analysis:
Using a realist approach, we will work with 15 CLOs based in disadvantaged communities in England, Scotland and Northern Ireland. A realist synthesis of review papers, and a policy analysis in different contexts, precedes qualitative interviews and workshops with stakeholders, to find out how CLOs’ programmes work and identify existing data. We will explore participants’ experiences through: a Q methodology study; participatory photography workshops; qualitative interviews and measure outcomes using a longitudinal survey, with 225 CLO participants, to assess impact for people who connect with the CLOs. An economic analysis will estimate costs and benefits to participants, for different contexts and mechanisms. A ‘Lived Experience Panel’ of people connected with our CLOs as participants or volunteers, will ensure the appropriateness of the research, interpretation and reporting of findings.
Ethics and dissemination:
This project, research tools and consent processes have been approved by the Glasgow Caledonian University School of Health and Life Sciences Ethics Committee, and affirmed by Ethics Committees at Bournemouth University, Queen’s University Belfast and the University of East London. Common Health Assets does not involve any National Health Service sites, staff or patients.
Findings will be presented through social media, project website, blogs, policy briefings, journal articles, conferences and visually in short digital stories, and photographic exhibitions
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