982 research outputs found
On the Asserted Clash between the Freud and the Bianchi Identities
Through a constructive method it is shown that the claim advanced in recent
times about a clash that should occur between the Freud and the Bianchi
identities in Einstein's general theory of relativity is based on a faulty
argument.Comment: 4 pages, plain Te
Q-stars and charged q-stars
We present the formalism of q-stars with local or global U(1) symmetry. The
equations we formulate are solved numerically and provide the main features of
the soliton star. We study its behavior when the symmetry is local in contrast
to the global case. A general result is that the soliton remains stable and
does not decay into free particles and the electrostatic repulsion preserves it
from gravitational collapse. We also investigate the case of a q-star with
non-minimal energy-momentum tensor and find that the soliton is stable even in
some cases of collapse when the coupling to gravity is absent.Comment: Latex, 19pg, 12 figures. Accepted in Phys. Rev.
Currents and Superpotentials in classical gauge invariant theories I. Local results with applications to Perfect Fluids and General Relativity
E. Noether's general analysis of conservation laws has to be completed in a
Lagrangian theory with local gauge invariance. Bulk charges are replaced by
fluxes of superpotentials. Gauge invariant bulk charges may subsist when
distinguished one-dimensional subgroups are present. As a first illustration we
propose a new {\it Affine action} that reduces to General Relativity upon gauge
fixing the dilatation (Weyl 1918 like) part of the connection and elimination
of auxiliary fields. It allows a comparison of most gravity superpotentials and
we discuss their selection by the choice of boundary conditions. A second and
independent application is a geometrical reinterpretation of the convection of
vorticity in barotropic nonviscous fluids. We identify the one-dimensional
subgroups responsible for the bulk charges and thus propose an impulsive
forcing for creating or destroying selectively helicity. This is an example of
a new and general Forcing Rule.Comment: 64 pages, LaTeX. Version 2 has two more references and one misprint
corrected. Accepted in Classical and Quantum Gravit
A Dual-Beam Irradiation Facility for a Novel Hybrid Cancer Therapy
In this paper we present the main ideas and discuss both the feasibility and
the conceptual design of a novel hybrid technique and equipment for an
experimental cancer therapy based on the simultaneous and/or sequential
application of two beams, namely a beam of neutrons and a CW (continuous wave)
or intermittent sub-terahertz wave beam produced by a gyrotron for treatment of
cancerous tumors. The main simulation tools for the development of the computer
aided design (CAD) of the prospective experimental facility for clinical trials
and study of such new medical technology are briefly reviewed. Some tasks for a
further continuation of this feasibility analysis are formulated as well.Comment: 18 pages, 3 tables, 8 figures, 50 reference
Throat related symptoms and voice: development of an instrument for self assessment of throat-problems
<p>Abstract</p> <p>Background</p> <p>Symptoms from throat (sensation of globus; frequent throat clearing; irritated throat) are common in patients referred to voice clinics and to ENT specialists. The relation to symptoms of voice discomfort is unclear and in some cases patients do not have voice problems at all. Instruments for patients' self-reporting of symptoms, and assessment of handicap, such as the Voice Handicap Index (VHI), are in common use in voice clinics. Symptoms from throat are however only marginally covered. Purpose: To develop and evaluate an instrument that could make the patients' estimation of symptoms from the throat possible. Further to facilitate the consideration of the relation between throat- and voice problems with the Throat subscale together with a Swedish translation of the Voice Handicap Index. Finally to try the VHI with the Throat subscale: the VHI-T, for test-retest reliability and validity.</p> <p>Methods</p> <p>A subscale with 10 throat related items was developed for appliance with the VHI. The VHI was translated to Swedish and retranslated to English. The questionnaire was tried in two phases on a total of 23+144 patients and 12+58 voice healthy controls. The reliability was calculated with Cronbach's alpha, ICC and Pearson's correlation coefficient. The validity was estimated by independent T-test.</p> <p>Results</p> <p>The difference in VHI-T scores between the patients and the voice-healthy controls was significant (<it>p </it>= < 0,01) and there was a good correlation of the test- retest occasions. The reliability testing of the entire questionnaire showed an alpha value of <it>r </it>= 0,90 and that for the Throat subscale separately a value of <it>r </it>= 0,87 which shows a high degree of reliability.</p> <p>Conclusions</p> <p>For the estimation of self-perceived throat and voice problems the scale on throat related problems together with the present Swedish translation of the Voice Handicap Index, (VHI) the VHI-Throat, proves to be a valid and reliable instrument. The throat subscale seems to help revealing a category of symptoms that are common in our patients. These are symptoms that have not earlier been possible to cover with the questionnaires designed for use in the voice clinic.</p
Indications for and Utilization of ACE Inhibitors in Older Individuals with Diabetes
Angiotensin-converting enzyme inhibitors (ACE) and angiotensin receptor blockers (ARB) improve cardiovascular outcomes in high-risk individuals with diabetes. Despite the marked benefit, it is unknown what percentage of patients with diabetes would benefit from and what percentage actually receive this preventive therapy. OBJECTIVES : To examine the proportion of older diabetic patients with indications for ACE or ARB (ACE/ARB). To generate national estimates of ACE/ARB use. DESIGN AND PARTICIPANTS : Survey of 742 individuals≥55 years (representing 8.02 million U.S. adults) self-reporting diabetes in the 1999 to 2002 National Health and Nutrition Examination Survey. MEASUREMENTS : Prevalence of guideline indications (albuminuria, cardiovascular disease, hypertension) and other cardiac risk factors (hyperlipidemia, smoking) with potential benefit from ACE/ARB. Prevalence of ACE/ARB use overall and by clinical indication. RESULTS : Ninety-two percent had guideline indications for ACE/ARB. Including additional cardiac risk factors, the entire (100%) U.S. noninstitutionalized older population with diabetes had indications for ACE/ARB. Overall, 43% of the population received ACE/ARB. Hypertension was associated with higher rates of ACE/ARB use, while albuminuria and cardiovascular disease were not. As the number of indications increased, rates of use increased, however, the maximum prevalence of use was only 53% in individuals with 4 or more indications for ACE/ARB. CONCLUSIONS : ACE/ARB is indicated in virtually all older individuals with diabetes; yet, national rates of use are disturbingly low and key risk factors (albuminuria and cardiovascular disease) are being missed. To improve quality of diabetes care nationally, use of ACE/ARB therapy by ALL older diabetics may be a desirable addition to diabetes performance measurement sets.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74734/1/j.1525-1497.2006.00351.x.pd
A formally verified compiler back-end
This article describes the development and formal verification (proof of
semantic preservation) of a compiler back-end from Cminor (a simple imperative
intermediate language) to PowerPC assembly code, using the Coq proof assistant
both for programming the compiler and for proving its correctness. Such a
verified compiler is useful in the context of formal methods applied to the
certification of critical software: the verification of the compiler guarantees
that the safety properties proved on the source code hold for the executable
compiled code as well
Q-ball dynamics from atomic Bose-Einstein condensates
Relativistic scalar field theories with a conserved global charge Q possess
often (meta)stable spherically symmetric soliton solutions, called Q-balls. We
elaborate on the perfect formal analogy which exists between Q-balls, and
spherically symmetric solitons in certain non-relativistic atomic Bose-Einstein
condensates, for which the dominant interatomic interaction can be tuned
attractive. In a harmonic trap, present in existing experiments, the Q-ball
solution is modified in an essential way. If the trap is significantly
prolongated in one direction, however, then genuine solitons do appear, and
actual experimental data can be obtained for some of the Q-ball properties
studied numerically in the relativistic cosmological context, such as their
formation and collisions. We also suggest conditions under which the same
cosmologically relevant analogies could be extended to the fully
three-dimensional case.Comment: 16 pages. v2: clarifications and references adde
Acceptability of Carraguard Vaginal Microbicide Gel among HIV-Infected Women in Chiang Rai, Thailand
Background: Few studies of microbicide acceptability among HIV-infected women have been done. We assessed CarraguardH vaginal gel acceptability among participants in a randomized, controlled, crossover safety trial in HIV-infected women in Thailand. Methodology/Principal Findings: Participants used each of 3 treatments (Carraguard gel, methylcellulose placebo gel, and no product) for 7 days, were randomized to one of six treatment sequences, and were blinded to the type of gel they received in the two gel-use periods. After both gel-use periods, acceptability was assessed by face-to-face interview. Responses were compared to those of women participating in two previous Carraguard safety studies at the same study site. Sixty women enrolled with a median age of 34 years; 25 % were sexually active. Self-reported adherence (98%) and overall satisfaction rating of the gels (87% liked ‘‘somewhat’ ’ or ‘‘very much’’) were high, and most (77%) considered the volume of gel ‘‘just right.’ ’ For most characteristics, crossover trial participants evaluated the gels more favorably than women in the other two trials, but there were few differences in the desired characteristics of a hypothetical microbicide. Almost half (48%) of crossover trial participants noticed a difference between Carraguard and placebo gels; 33 % preferred Carraguard while 12 % preferred placebo (p=0.01). Conclusions/Significance: Daily Carraguard vaginal gel use was highly acceptable in this population of HIV-infecte
Dynamical Boson Stars
The idea of stable, localized bundles of energy has strong appeal as a model
for particles. In the 1950s John Wheeler envisioned such bundles as smooth
configurations of electromagnetic energy that he called {\em geons}, but none
were found. Instead, particle-like solutions were found in the late 1960s with
the addition of a scalar field, and these were given the name {\em boson
stars}. Since then, boson stars find use in a wide variety of models as sources
of dark matter, as black hole mimickers, in simple models of binary systems,
and as a tool in finding black holes in higher dimensions with only a single
killing vector. We discuss important varieties of boson stars, their dynamic
properties, and some of their uses, concentrating on recent efforts.Comment: 79 pages, 25 figures, invited review for Living Reviews in
Relativity; major revision in 201
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