oalib

OALib Journal期刊

ISSN: 2333-9721

费用:99美元

投稿

时间不限

2019 ( 8 )

2018 ( 116 )

2017 ( 140 )

2016 ( 111 )

自定义范围…

匹配条件: “Jean-Francois;” ,找到相关结果约22408条。
列表显示的所有文章,均可免费获取
第1页/共22408条
每页显示
The Mathematical Foundations of General Relativity Revisited  [PDF]
Jean-Francois Pommaret
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.48A022
Abstract:

The purpose of this paper is to present for the first time an elementary summary of a few recent results obtained through the application of the formal theory of partial differential equations and Lie pseudogroups in order to revisit the mathematical foundations of general relativity. Other engineering examples (control theory, elasticity theory, electromagnetism) will also be considered in order to illustrate the three fundamental results that we shall provide successively. 1) VESSIOT VERSUS CARTAN: The quadratic terms appearing in the “Riemann tensor” according to the “Vessiot structure equations” must not be identified with the quadratic terms appearing in the well known “Cartan structure equations” for Lie groups. In particular, “curvature + torsion” (Cartan) must not be considered as a generalization of “curvature alone” (Vessiot). 2) JANET VERSUS SPENCER: The “Ricci tensor” only depends on the nonlinear transformations (called “elations” by Cartan in 1922) that describe the “difference” existing between the Weyl group (10 parameters of the Poincaré subgroup + 1 dilatation) and the conformal group of space-time (15 parameters). It can be defined without using the indices leading to the standard contraction or trace of the Riemann tensor. Meanwhile, we shall obtain the number of components of the Riemann and Weyl tensors without any combinatoric argument on the exchange of indices. Accordingly and contrary to the “Janet sequence”, the “Spencer sequence” for the conformal Killing system and its formal adjoint fully describe the Cosserat equations, Maxwell equations and Weyl equations but General Relativity is not coherent with this result. 3) ALGEBRA VERSUS GEOMETRY: Using the powerful methods of “Algebraic Analysis”, that is a mixture of homological agebra and differential geometry, we shall prove that, contrary to other equations of physics (Cauchy

The Mathematical Foundations of Gauge Theory Revisited  [PDF]
Jean-Francois Pommaret
Journal of Modern Physics (JMP) , 2014, DOI: 10.4236/jmp.2014.55026
Abstract:

We start recalling with critical eyes the mathematical methods used in gauge theory and prove that they are not coherent with continuum mechanics, in particular the analytical mechanics of rigid bodies (despite using the same group theoretical methods) and the well known couplings existing between elasticity and electromagnetism (piezzo electricity, photo elasticity, streaming birefringence). The purpose of this paper is to avoid such contradictions by using new mathematical methods coming from the formal theory of systems of partial differential equations and Lie pseudo groups. These results finally allow unifying the previous independent tentatives done by the brothers E. and F. Cosserat in 1909 for elasticity or H. Weyl in 1918 for electromagnetism by using respectively the group of rigid motions of space or the conformal group of space-time. Meanwhile we explain why the Poincaré duality scheme existing between geometry and physics has to do with homological algebra and algebraic analysis. We insist on the fact that these results could not have been obtained before 1975 as the corresponding tools were not known before.

Financial incentives for smoking cessation in low-income smokers: study protocol for a randomized controlled trial
Jean-Francois ETTER
Trials , 2012, DOI: 10.1186/1745-6215-13-88
Abstract: A randomized, parallel groups, controlled trial.Participants: Eight hundred low-income smokers in Switzerland (the less affluent third of the population, based on fiscal taxation).Intervention: A smoking cessation program including: (a) financial incentives given during 6?months; and (b) Internet-based counseling. Financial rewards will be offered for biochemically verified smoking abstinence after 1, 2, and 3?weeks and 1, 3, and 6?months, for a maximum of 1,500 CHF (1,250 EUR, 1,500 USD) for those abstinent at all time-points. All participants, including controls, will receive Internet-based, individually-tailored, smoking cessation counseling and self-help booklets, but there will be no in-person or telephone counseling, and participants will not receive medications. The control group will not receive financial incentives.Objective: To increase smoking cessation rates.Outcome: Smoking abstinence after 6 and 18?months, not contradicted by biochemical tests. We will assess relapse after the end of the intervention, to test whether 6-month effects translate into sustained abstinence 12?months after the incentives are withdrawn.Randomization: Will be done using sealed envelopes drawn by participants.Blinding: Is not possible in this context.Smoking prevention policies and interventions have been least effective in the least educated, low-income groups. Combining financial incentives and Internet-based counseling is an innovative approach that, if proven acceptable and effective, could be later implemented on a large scale at a reasonable cost, decrease health disparities, and save many lives.Current Controlled Trials ISRCTN04019434.
Agarose Gel Electrophoresis - Applications in Clinical Chemistry
Jean-Francois Giot
Journal of Medical Biochemistry , 2010, DOI: 10.2478/v10011-009-0033-8
Abstract: Agarose gel electrophoresis is a well established technique routinely used in clinical laboratories for screening protein abnormalities in various biological fluids (serum, urine, CSF). It is based on the principles of zone electrophoresis. Electrophoretograms are evaluated visually for the presence of quantitatively or qualitatively abnormal protein bands. The technique is used for electrophoresis of serum, urine, CSF proteins, enzymes (ALP, LDH and CK), lipoproteins and hemoglobin. Serum protein electrophoresis (SPE) is a very commonly used analytical method in clinical chemistry. Changes in the relative concentration of fractions allow easy recognition of pathological disorders associated with nephrotic syndrome, inflammatory reaction and hepatic diseases. SPE is a screening test for detecting the M component (MC). Immunofixation (IFE) with use of specific antisera allows detection of the type of MC. SPE is also a method for the quantification of MC and monitoring of disease that is essential for clinical evaluation and follow-up of patients with plasma cell disorders.
Trafficking of T Lymphocytes after Allo-Transplantation: A New Experimental Model
L. Jean-Francois
Surgery Journal , 2012,
Abstract: Leukocytes are believed to access sites of inflammation via cell adhesion molecule (CAM) mediated adhesion, activation and transmigration through the vascular endothelium. However, little is known about the mechanisms by which immune effector cells gain access to transplanted organ. The objective of this work was to evaluate a simple experimental model to characterize the migration of T lymphocytes to vascular tissue following transplantation. Brown Norway aortic allografts were transplanted orthotopically into Lewis recipients (n = 10). T cells were isolated from na ve or allo-exposed (activated) Lewis spleens using nylon wool columns. Cr51 labeled na ve T cells and In111 labeled activated T cells (15x106 of each) were injected into animals, 9 days after transplantation with or without anti- 4/ 2_monoclonal antibody (n = 5/group). All animals were then sacrificed on day 10 and evaluated by histology and counts. All allografts had significant infiltration of the adventitia by mononuclear cells at day 10 as compared to control aorta. There was an average of 220+33 Cr51 cpm and 224 + 30. In111 cpm as compared to control aorta (p<0.0001). Anti 4/ 2 mAb treatment resulted in significant reduction in labeled T cell infiltration with a 89% reduction in Cr51 cpm and 73% reduction in In111 cpm both approaching control levels. We have demonstrated that T lymphocytes infiltrate vascular tissue early after transplantation and appears to be mediated via 4/ 2 integrin mechanism. This represents direct evidence of the role of CAM in trafficking of T cells in transplanted allografts and the characterization of a model to evaluate this trafficking.
L AMPLITUDE DU CYCLE ECONOMIQUE ET DE L ECART DE PRODUCTION AU LIBAN
Jean-Francois VERNE
Région et Développement , 2011,
Abstract: This article shows that the business cycle magnitude and the output gap strongly varied in the Lebanon between 1970 and 2008, the most important variations taking place from 1975 to 1990 corresponding to the period of the civil war. Nevertheless, a decrease in the discrepancy between these two indicators around the long-run trend can be observed since the beginning of 1990s. These reductions of the cyclic amplitude and output gap do not result from the end of the war in 1990 but rather from the general government final consumption expenditure and economic dependence rate. These two variables explain a mismatch between the observed GDP and the potential GP and consequently the occurrence of economic stability.
Simulation and identification of the fractional Brownian motion: a bibliographical and comparative study
Jean-Francois Coeurjolly
Journal of Statistical Software , 2000,
Abstract:
Gravitational Waves from the Non-Perturbative Decay of Condensates along Supersymmetric Flat Directions
Jean-Francois Dufaux
Physics , 2009, DOI: 10.1103/PhysRevLett.103.041301
Abstract: It has recently been shown that specific non-perturbative effects may lead to an explosive decay of flat direction condensates in supersymmetric theories. We confirm explicitly the efficiency of this process with lattice simulations: after few rotations of the condensates in their complex plane, most of their energy is quickly converted into inhomogeneous fluctuations. We then point out that this generates a gravitational wave background which depends on the inflaton sector and falls in the Hz-kHz frequency range today. We compute the resulting spectrum and study how it depends on the parameters. We show that these gravity waves can be observable by upcoming experiments like Advanced LIGO and depend crucially on (i) the initial VEV of flat directions when they start to oscillate, (ii) their soft SUSY-breaking mass and (iii) the reheat temperature of the universe. This signal could open a new observational window on inflation and low-energy supersymmetry.
Future Astrometry with ALMA to characterise extra-solar planet orbits
Jean-Francois Lestrade
Physics , 2003,
Abstract: The most complete catalogue of nearby stars (Gliese and Jarheiss, 1991) has been used to search for the stars whose photospheric thermal emission can be detected by the future millimeter array ALMA. We found that 446 nearby stars with spectral types ranging from A to M are detectable. A long-term astrometric observation programme (> 10 yr) of these stars with ALMA (theoretical astrometric precision = 0.1 milliarcsecond) would be sensitive to wobbles caused by the gravitational pull of possible unseen planets. Such a programme would probe minimum planetary masses as low as 0.1 Jupiter for an orbital period of 10 years. We provide histogrammes of these minimum masses and of ALMA integration times for these 446 ALMA stars.
Evidence of Overcharging in the Complexation between Oppositely Charged Polymers and Surfactants
Jean-Francois Berret
Physics , 2005, DOI: 10.1063/1.2031167
Abstract: We report on the complexation between charged-neutral block copolymers and oppositely charged surfactants studied by small-angle neutron scattering. Two block copolymers/surfactant systems are investigated, poly(acrylic acid)-b-poly(acrylamide) with dodecyltrimethylammonium bromide and poly(trimethylammonium ethylacrylate methylsulfate)-b-poly(acrylamide) with sodium dodecyl sulfate. The two systems are similar in terms of structure and molecular weight but have different electrostatic charges. The neutron scattering data have been interpreted in terms of a model that assumes the formation of mixed polymer-surfactant aggregates, also called colloidal complexes. These complexes exhibit a core-shell microstructure, where the core is a dense coacervate microphase of micelles surrounded by neutral blocks. Here, we are taking advantage of the fact that the complexation results in finite-size aggregates to shed some light on the complexation mechanisms. In order to analyze quantitatively the neutron data, we develop two different approaches to derive the number of surfactant micelles per polymer in the mixed aggregates and the distributions of aggregation numbers. With these results, we show that the formation of the colloidal complex is in agreement with the overcharging predictions. In both systems, the amount of polyelectrolytes needed to build the core-shell colloids always exceeds the number that would be necessary to compensate the charge of the micelles. For the two polymer-surfactant systems investigated, the overcharging ratios are 0.66 and 0.38.
第1页/共22408条
每页显示


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.