2,409 research outputs found
Split Supersymmetry from Anomalous U(1)
We present a scenario wherein the anomalous U(1) D-term of string origin
triggers supersymmetry breaking and generates naturally a Split Supersymmetry
spectrum. When the gaugino and the Higgsino masses (which are of the same order
of magnitude) are set at the TeV scale, we find the scalar masses to be in the
range (10^6 - 10^8) GeV. The U(1) D-term provides a small expansion parameter
which we use to explain the mass and mixing hierarchies of quarks and leptons.
Explicit models utilizing exact results of N = 1 suersymmetric gauge theories
consistent with anomaly constraints, fermion mass hierarchy, and supersymmetry
breaking are presented.Comment: 20 pages in LaTeX, version published in NPH
Blocking of the B7-CD28 pathway increases the capacity of FasL<sup>+</sup> (CD95L<sup>+</sup>) dendritic cells to kill alloactivated T cells
On the origin of the Boson peak in globular proteins
We study the Boson Peak phenomenology experimentally observed in globular
proteins by means of elastic network models. These models are suitable for an
analytic treatment in the framework of Euclidean Random Matrix theory, whose
predictions can be numerically tested on real proteins structures. We find that
the emergence of the Boson Peak is strictly related to an intrinsic mechanical
instability of the protein, in close similarity to what is thought to happen in
glasses. The biological implications of this conclusion are also discussed by
focusing on a representative case study.Comment: Proceedings of the X International Workshop on Disordered Systems,
Molveno (2006
Anomalous U(1) symmetry and lepton flavor violation
We show that in a large class of models based on anomalous U(1) symmetry
which addresses the fermion mass hierarchy problem, leptonic flavor changing
processes are induced that are in the experimentally interesting range. The
flavor violation occurs through the renormalization group evolution of the soft
SUSY breaking parameters between the string scale and the U(1)_A breaking
scale. We derive general expressions for the evolution of these parameters in
the presence of higher dimensional operators. Several sources for the flavor
violation are identified: flavor-dependent contributions to the soft masses
from the U(1)_A gaugino, scalar mass corrections proportional to the trace of
U(1)_A charge, non-proportional A-terms from vertex corrections, and the U(1)_A
D-term. Quantitative estimates for the decays \mu -> e \gamma and \tau -> \mu
\gamma are presented in supergravity models which accommodate the relic
abundance of neutralino dark matter.Comment: References added, typos corrected, 28 pages LaTeX, includes 14 eps
figure
Bounds on SCFTs from Conformal Perturbation Theory
The operator product expansion (OPE) in 4d (super)conformal field theory is
of broad interest, for both formal and phenomenological applications. In this
paper, we use conformal perturbation theory to study the OPE of nearly-free
fields coupled to SCFTs. Under fairly general assumptions, we show that the OPE
of a chiral operator of dimension with its complex
conjugate always contains an operator of dimension less than . Our
bounds apply to Banks-Zaks fixed points and their generalizations, as we
illustrate using several examples.Comment: 36 pages; v2: typos fixed, minor change
Anthropometric measures in relation to Basal Cell Carcinoma: a longitudinal study
BACKGROUND: The relationship between anthropometric indices and risk of basal cell carcinoma (BCC) is largely unknown. We aimed to examine the association between anthropometric measures and development of BCC and to demonstrate whether adherence to World Health Organisation guidelines for body mass index, waist circumference, and waist/hip ratio was associated with risk of BCC, independent of sun exposure. METHODS: Study participants were participants in a community-based skin cancer prevention trial in Nambour, a town in southeast Queensland (latitude 26°S). In 1992, height, weight, and waist and hip circumferences were measured for all 1621 participants and weight was remeasured at the end of the trial in 1996. Prevalence proportion ratios were calculated using a log-binomial model to estimate the risk of BCC prior to or prevalent in 1992, while Poisson regression with robust error variances was used to estimate the relative risk of BCC during the follow-up period. RESULTS: At baseline, 94 participants had a current BCC, and 202 had a history of BCC. During the 5-year follow-up period, 179 participants developed one or more new BCCs. We found no significant association between any of the anthropometric measures or indices and risk of BCC after controlling for potential confounding factors including sun exposure. There was a suggestion that short-term weight gain may increase the risk of developing BCC for women only. CONCLUSION: Adherence to World Health Organisation guidelines for body mass index, waist circumference and waist/hip ratio is not significantly associated with occurrence of basal cell carcinomas of the skin
Recruiting medical groups for research: relationships, reputation, requirements, rewards, reciprocity, resolution, and respect
BACKGROUND: In order to conduct good implementation science research, it will be necessary to recruit and obtain good cooperation and comprehensive information from complete medical practice organizations. The goal of this paper is to report an effective example of such a recruitment effort for a study of the organizational aspects of depression care quality. METHODS: There were 41 medical groups in the Minnesota region that were eligible for participation in the study because they had sufficient numbers of patients with depression. We documented the steps required to both recruit their participation in this study and obtain their completion of two questionnaire surveys and two telephone interviews. RESULTS: All 41 medical groups agreed to participate and consented to our use of confidential data about their care quality. In addition, all 82 medical directors and quality improvement coordinators completed the necessary questionnaires and interviews. The key factors explaining this success can be summarized as the seven R's: Relationships, Reputation, Requirements, Rewards, Reciprocity, Resolution, and Respect. CONCLUSION: While all studies will not have all of these factors in such good alignment, attention to them may be important to other efforts to add to our knowledge of implementation science
Inverse Modeling for MEG/EEG data
We provide an overview of the state-of-the-art for mathematical methods that
are used to reconstruct brain activity from neurophysiological data. After a
brief introduction on the mathematics of the forward problem, we discuss
standard and recently proposed regularization methods, as well as Monte Carlo
techniques for Bayesian inference. We classify the inverse methods based on the
underlying source model, and discuss advantages and disadvantages. Finally we
describe an application to the pre-surgical evaluation of epileptic patients.Comment: 15 pages, 1 figur
(De)Constructing a Natural and Flavorful Supersymmetric Standard Model
Using the framework of deconstruction, we construct simple, weakly-coupled
supersymmetric models that explain the Standard Model flavor hierarchy and
produce a flavorful soft spectrum compatible with precision limits. Electroweak
symmetry breaking is fully natural; the mu-term is dynamically generated with
no B mu-problem and the Higgs mass is easily raised above LEP limits without
reliance on large radiative corrections. These models possess the distinctive
spectrum of superpartners characteristic of "effective supersymmetry": the
third generation superpartners tend to be light, while the rest of the scalars
are heavy.Comment: 36 pages, 4 figures ; v2: references added, expanded discussion of
FCNC
Sunscreens - Which and what for?
It is well established that sun exposure is the main cause for the development of skin cancer. Chronic continuous UV radiation is believed to induce malignant melanoma, whereas intermittent high-dose UV exposure contributes to the occurrence of actinic keratosis as precursor lesions of squamous cell carcinoma as well as basal cell carcinoma. Not only photocarcinogenesis but also the mechanisms of photoaging have recently become apparent. In this respect the use of sunscreens seemed to prove to be more and more important and popular within the last decades. However, there is still inconsistency about the usefulness of sunscreens. Several studies show that inadequate use and incomplete UV spectrum efficacy may compromise protection more than previously expected. The sunscreen market is crowded by numerous products. Inorganic sunscreens such as zinc oxide and titanium oxide have a wide spectral range of activity compared to most of the organic sunscreen products. It is not uncommon for organic sunscreens to cause photocontact allergy, but their cosmetic acceptability is still superior to the one given by inorganic sunscreens. Recently, modern galenic approaches such as micronization and encapsulation allow the development of high-quality inorganic sunscreens. The potential systemic toxicity of organic sunscreens has lately primarily been discussed controversially in public, and several studies show contradictory results. Although a matter of debate, at present the sun protection factor (SPF) is the most reliable information for the consumer as a measure of sunscreen filter efficacy. In this context additional tests have been introduced for the evaluation of not only the protective effect against erythema but also protection against UV-induced immunological and mutational effects. Recently, combinations of UV filters with agents active in DNA repair have been introduced in order to improve photoprotection. This article reviews the efficacy of sunscreens in the prevention of epithelial and nonepithelial skin cancer, the effect on immunosuppression and the value of the SPF as well as new developments on the sunscreen market. Copyright (C) 2005 S. Karger AG, Basel
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