800 research outputs found
Supersymmetric quantum theory and (non-commutative) differential geometry
We reconsider differential geometry from the point of view of the quantum
theory of non-relativistic spinning particles, which provides examples of
supersymmetric quantum mechanics. This enables us to encode geometrical
structure in algebraic data consisting of an algebra of functions on a manifold
and a family of supersymmetry generators represented on a Hilbert space. We
show that known types of differential geometry can be classified in terms of
the supersymmetries they exhibit. Replacing commutative algebras of functions
by non-commutative *-algebras of operators, while retaining supersymmetry, we
arrive at a formulation of non-commutative geometry encompassing and extending
Connes' original approach. We explore different types of non-commutative
geometry and introduce notions of non-commutative manifolds and non-commutative
phase spaces. One of the main motivations underlying our work is to construct
mathematical tools for novel formulations of quantum gravity, in particular for
the investigation of superstring vacua.Comment: 125 pages, Plain TeX fil
Supersymmetric quantum theory and non-commutative geometry
Classical differential geometry can be encoded in spectral data, such as
Connes' spectral triples, involving supersymmetry algebras. In this paper, we
formulate non-commutative geometry in terms of supersymmetric spectral data.
This leads to generalizations of Connes' non-commutative spin geometry
encompassing non-commutative Riemannian, symplectic, complex-Hermitian and
(Hyper-)Kaehler geometry. A general framework for non-commutative geometry is
developed from the point of view of supersymmetry and illustrated in terms of
examples. In particular, the non-commutative torus and the non-commutative
3-sphere are studied in some detail.Comment: 77 pages, PlainTeX, no figures; present paper is a significantly
extended version of the second half of hep-th/9612205. Assumptions in Sect.
2.2.5 clarified; final version to appear in Commun.Math.Phy
Nonlocal Effects on the Magnetic Penetration Depth in d-wave Superconductors
We show that, under certain conditions, the low temperature behavior of the
magnetic penetration depth of a pure d-wave superconductor is
determined by nonlocal electrodynamics and, contrary to the general belief, the
deviation is proportional to T^2 and
not T. We predict that the dependence, due to
nonlocality, should be observable experimentally in nominally clean high-T_c
superconductors below a crossover temperature . Possible complications due to impurities, surface quality and
crystal axes orientation are discussed.Comment: REVTeX3.0; 4 pages, 1 EPS figure (included); Submitted to Phys. Rev.
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Patient use of the Internet for health care information in Switzerland.
The aim of this study was to examine for the first time the frequency of Internet use for medical purposes by patients in Switzerland.
In 2001 over a period of one month, 1604 patients at 8 medical practices in Switzerland completed a self-administered questionnaire on their access to the Internet and any search for medical information using this media. The attending physician supplied the patient's diagnosis and information on the severity of the disorder motivating the visit using a separate questionnaire.
46% of the patients included in the study had a personal computer, 33% had an Internet connection and 10% used the Internet to find medical information. Age was inversely associated with the probability of having an Internet access, whereas educational level and command of the English language were factors directly associated with this. Among those patients with access to the Internet, young adults (25 to 44 years) and those with knowledge of the English language searched for medical information significantly more frequently. Furthermore, patients attending urban medical practices and those with a more severe level of disease more often sought health care information on the Internet.
The proportion of patients in Switzerland who search for medical information on the Internet is similar to the rates observed in European English-speaking countries. The Internet allows patients to actively search for information concerning their own health problems but is not currently the most common source of information used by patients. Since health professionals generate, directly or indirectly, most of the medical information published on the Internet, additional research is needed to better understand patients' needs and expectations concerning medical information using this media
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Ability-Based Design: Concept, Principles and Examples
Current approaches to accessible computing share a common goal of making technology accessible to users with disabilities. Perhaps because of this goal, they may also share a tendency to centralize disability rather than ability. We present a refinement to these approaches called ability-based design that consists of focusing on ability throughout the design process in an effort to create systems that leverage the full range of human potential. Just as user-centered design shifted the focus of interactive system design from systems to users, ability-based design attempts to shift the focus of accessible design from disability to ability. Although prior approaches to accessible computing may consider users’ abilities to some extent, ability-based design makes ability its central focus. We offer seven ability-based design principles and describe the projects that inspired their formulation. We also present a research agenda for ability-based design.Engineering and Applied Science
Risk Assessment to the Health of Amazonian Indigenous For the Consumption of Fish, Meat of Hunts and Vegetables Containing Metylmercury
This study was to evaluate the exposure to methylmercury (HgMe) and the potential health risk of Tupari Indians through the consumption of their main foods. Were collection of samples of plant foods and muscle tissue from different species of fish and wild animals consumed in three villages of the Rio Branco Indigenous Land in Rondônia, in the Brazilian Amazon. The HgMe was measured in an atomic fluorescence spectrophotometer with gas chromatography. The statistical treatment of the data was performed by software R. Of the six different plant species, only sweet potato (Ipomoea batatas) had mean concentrations of HgMe above the limit of detection of the analytical technique for the three villages. There was a significant difference in the levels of HgMe between the species of wild animals and fish belonging to the same alimentary habit. Carnivores presented higher levels of HgMe than those obtained for non-predators, both for fish and for wild animals. The results of the assessment of the potential risk to indigenous health indicated a total HgMe of the weekly ingestion rate (WIR) of between 8.4 and 15.0 μg / kg of body weight for the villages evaluated, extrapolating all reference doses ( RfD) regarding for the Provisional Tolerable Weekly Intake (PTWI). The risk quotients (RQ) varied from 5.3 to 21.4, considerably exceeding the limit (RQ ≤ 1), which allows to consider the impossibility of toxic effects of HgMe. The fishes accounted for the highest percentage of WIR of HgMe for all villages, with an emphasis on predatory species. Considering the nutritional value of fish meat, it is suggested the continuity of the consumption of this meat in the villages with preference for non-carnivores
Stonefly (Plecoptera) fauna of streams in a mountainous area of Central Brazil: abiotic factors and nymph density
Development of a PbWO4 Detector for Single-Shot Positron Annihilation Lifetime Spectroscopy at the GBAR Experiment
We have developed a PbWO4 (PWO) detector with a large dynamic range to measure the intensity of a positron beam and the absolute density of the ortho-positronium (o-Ps) cloud it creates. A simulation study shows that a setup based on such detectors may be used to determine the angular distribution of the emission and reflection of o-Ps to reduce part of the uncertainties of the measurement. These will allow to improve the precision in the measurement of the cross-section for the (anti)hydrogen formation by (anti)proton-positronium charge exchange and to optimize the yield of antihydrogen ion which is an essential parameter in the GBAR experiment
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