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Search Results: 1 - 10 of 4016 matches for " Jacques Arvieux "
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Electroproduction of pseudoscalar mesons on the deuteron
Michail P. Rekalo,Egle Tomasi-Gustafsson,Jacques Arvieux
Physics , 2000,
Abstract: A general analysis of polarization phenomena for coherent meson electroproduction on deuterons, $e+ d\to e+ d +P^0$, where $P^0$ is a pseudoscalar $\pi ^0$ or $\eta$-meson, is presented. The spin structure of the electromagnetic current for $P^0$-production at threshold is parametrized in terms of specific (inelastic) threshold electromagnetic form factors which depend on the momentum transfer squared and the effective mass of the produced hadronic system. We give expressions for the structure functions of the reaction $e+\vec{d}\to e +d+ P^0$ (where the deuteron target is polarized) in terms of these threshold form factors. The spin and isospin structures of the $\gamma ^{*}+d\to d+P^0$ amplitudes (where $\gamma ^*$ is a virtual photon) is established in the framework of the impulse approximation and relationships between meson electroproduction on deuterons and on nucleons are given. The reaction of $\pi^0$ electroproduction on deuterons is investigated in detail both at threshold and in the region of $\Delta $-isobar excitation, using the effective Lagrangian approach for the calculation of the amplitudes of the elementary process $\gamma^*+N\to N+\pi$. Special attention is devoted to the analysis of all standard contributions to the exclusive cross section for $d(e,e\pi^0)d$, which are functions of the momentum transfer square, $k^2$, of the excitation energy of the produced hadrons and of the pion production angle, in a region of relatively large momentum transfer. The sensitivity of these contributions to different parametrizations of the $\gamma^*\pi\omega$ form factor as well as to the choice of $NN-$potential is discussed.
Neutral weak currents in pion electroproduction on the nucleon
Michail P. Rekalo,Jacques Arvieux,Egle Tomasi-Gustafsson
Physics , 2000, DOI: 10.1103/PhysRevC.65.035501
Abstract: Parity violating asymmetry in inclusive scattering of longitudinally polarized electrons by unpolarized protons with $\pi^0$ or $\pi^+$ meson production, is calculated as a function of the momentum transfer squared $Q^2$ and the total energy $W$ of the $\pi N$-system. This asymmetry, which is induced by the interference of the one-photon exchange amplitude with the parity-odd part of the $Z^0$-exchange amplitude, is calculated for the $\gamma^*(Z^*)+p\to N+\pi$ processes ($\gamma^*$ is a virtual photon and $Z^*$ a virtual Z-boson) considering the $\Delta$-contribution in the $s-$channel, the standard Born contributions and vector meson ($\rho$ and $\omega$) exchanges in the $t-$channel. Taking into account the known isotopic properties of the hadron electromagnetic and neutral currents, we show that the P-odd term is the sum of two contributions. The main term is model independent and it can be calculated exactly in terms of fundamental constants. It is found to be linear in $Q^2$. The second term is a relatively small correction which is determined by the isoscalar component of the electromagnetic current. Near threshold and in the $\Delta$-region, this isoscalar part is much smaller (in absolute value) than the isovector one: its contribution to the asymmetry depend on the polarization state (longitudinal or transverse) of the virtual photon.
C. Letoublon,Catherine Arvieux
Jurnalul de Chirurgie , 2005,
Abstract: The prognostic of the liver trauma is conditioned by the type of the hepatic injuries. Their anatomic and hemorhagic characteristics will influence the kind of treatment: emergency laparotomy or non-surgical treatment. The most important condition for a non-surgical treatment of the liver trauma is a stable patient. Operative option is indicated for unstable patients, when there are other visceral injuries or when the surgical unit hasn't accurate imagistics posssibilities. For optimal operative management of the liver trauma, some principles need to be followed: 1) the patient is positioned with the arms at right angles on arm boards, wich allowes better access to intravenous or intraarterial lines; 2) skin preparation is for a toarco-abdominal approach; 3) the primary incision is a midline one wich can be branched with a right transverse. After laparotomy there are two situations: liver injuries without or with active haemorrhage. For the first situation, evacuation of the hemoperitoneum, lavage and drainge are the only procedures indicated. For the second types of injuries we also describe favorable and unfavorable injuries. When the hand compression of the liver is effective and hepatic injury is anterior, the hemostasis after clampage of the hepatic pedicle (Pringle maneuver) is indicated. Perihepatic packing is indicated in case of choagulopaty. Hepatic resection it isn't recommended. The unfavorable situation is association of acidose-hypotermia and choagulopaty wich cause a "biological hemorrhage". In this cases are indicated"abbreviated laparotomy" with perihepatic packing (damage control) and planned reoperation or arterial embolisation (interventional radiology). When the clampage of the hepatic pedicle it isn't efficient, probably a hepatic vein is injured and a a perihepatic packing is also indicated. The unefficiency of the perihepatic packing, the clampage of the hepatic pedicle + inferior vena cava (under and above the liver) ± aorta it is necessary to stop the active bleeding. The closure of the laparotomy it is necessary to be made very fast, especially for the "abbreviated laparotomy". In the case of trauma of the main hepatic duct an external billiary drainage it is recommended. The reoperation it is indicated in some cases: intraabdominal hyperpression syndrome, perihepatic packing, other intraabdominal complications. Conclusion: The prognostic of the liver trauma depends by the anatomical type of the injuries. Operative management of the liver trauma is very difficult. The clampage of the hepatic pedicle (with or without vena cava
C. Letoublon,Catherine Arvieux
Jurnalul de Chirurgie , 2005,
Abstract: The most important condition for a conservative treatment of the liver trauma is a stable patient. Ultrasound and computerized tomography (CT) examinations are essential for the investigation of abdominal trauma. These explorations allow visualization of solid organ anatomy and have the ability to grade and quantify the livers' injuries (Mirvis classification). After the first exploration and the decision for initial non-operative approach, the patients will be followed in the intensive care unit (hemodynamic status, biological exploration, CT or ultrasonography). In this second survey period it is possible to appear complications (hemorrhage, peritonitis, intra-abdominal hyper-pressure syndrome etc.) and emergency laparotomy can be necessary. The overall mortality for non operative approach is about 9%, and direct mortality is under 1%. Secondary operations are necessary in 7-10% from these patients. Interventional radiology techniques and endoscopic procedures (such as endoscopic retrograde cholangio-pancreatography) allowed the reduction of the secondary surgical interventions. Hospital stay depends by the grade of the liver injury. Long term follow-up it is necessary; some cystic image can appear in the liver parenchyma at CT exam after months or years from the trauma, but without clinical significance.
C. Letoublon,Catherine Arvieux
Jurnalul de Chirurgie , 2005,
Abstract: The liver is the largest solid abdominal organ with a relatively fixed position, which makes it prone to injury. The liver is the second most commonly injured organ in abdominal trauma, but damage to the liver is the most common cause of death after abdominal injury. The most common cause of liver injury is blunt abdominal trauma, which is secondary to motor vehicle accidents in most instances. In the past, most of these injuries were treated surgically. However, surgical literature confirms that many of liver injuries have stopped bleeding by the time surgical exploration is performed, and some operations performed for blunt abdominal trauma are nontherapeutic. Imaging techniques and non-operative management, have made a great impact on the treatment of patients with liver trauma, and use of these techniques has resulted in marked reduction in the number of patients requiring surgery and nontherapeutic operations
C. Létoublon,Catherine Arvieux
Jurnalul de Chirurgie , 2005,
Dark Energy as a Property of Dark Matter  [PDF]
Jacques Leibovitz
Journal of Modern Physics (JMP) , 2011, DOI: 10.4236/jmp.2011.212181
Abstract: A novel model of dark matter (DM), elastically compressible, can contribute to the acceleration of our Universe expansion. While each galaxy compresses its own DM within its gravitation field, the DM bordering neighboring galaxies, far from their centers, is pulled apart. It is shown that, although the DM pressure tends to zero at such locations, the DM compressibility tends to infinity. This allows the DM to expand between galaxies without gravitation hindrance. The model is consistent with the coupled distributions of baryonic and dark matters, with black hole formation at the centers of large galaxies, with galactic flat rotation curves, with a Tully-Fisher relation, and with Milgrom’s MOND relation. Results are discussed.
Mechanism and evolution of multidomain aminoacyl-tRNA synthetases revealed by their inhibition by analogues of a reaction intermediate, and by properties of truncated forms  [PDF]
Jacques Lapointe
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.610115
Abstract: Many enzymes which catalyze the conversion of large substrates are made of several structural domains belonging to the same polypeptide chain. Transfer RNA (tRNA), one of the substrates of the multidomain aminoacyl-tRNA synthetases (aaRS), is an L-shaped molecule whose size in one dimension is similar to that of its cognate aaRS. Crystallographic structures of aaRS/tRNA complexes show that these enzymes use several of their structural domains to interact with their cognate tRNA. This mini review discusses first some aspects of the evolution and of the flexibility of the pentadomain bacterial glutamyl-tRNA synthetase (GluRS) revealed by kinetic and interaction studies of complementary truncated forms, and then illustrates how stable analogues of aminoacyl-AMP intermediates have been used to probe conformational changes in the active sites of Escherichia coli GluRS and of the nondiscriminating aspartyl-tRNA synthetase (ND-AspRS) of Pseudomonas aeruginosa.
A Review on Tectonic Record of Strain Buildup and Stress Release across the Andean Forearc along the Gulf of Guayaquil-Tumbes Basin (GGTB) near Ecuador-Peru Border  [PDF]
Jacques Bourgois
International Journal of Geosciences (IJG) , 2013, DOI: 10.4236/ijg.2013.43057

Gravimetric and geologic data show that the reactivation of the Neogene Interandean depression and/or the ~75 - 65 Ma ophiolite suture into the modern dynamic of the Andes controlled the Gulf of Guayaquil Tumbes basin (GGTB) location and evolution during the past 1.8 - 1.6 Myr at least. Depending on whether the remobilization occurred along the interandean depression or the ophiolite suture, the GGTB evolved trough pure or simple shear mechanisms, respectively. Because the GGTB exhibits an along strike tectonic asymmetry associated with a pervasive seismic gap, the simple shear solution is more likely. Tectonic inversion occurred along a mid-crust detachment (the Mid-Crust detachment hereafter) matching the ophiolite suture that accommodates the North Andean Block (NAB) northward drift. The so-called Decoupling Strip located at the shelf slope break accommodated the tensional stress rotation from N-S along the shelf area i.e. NAB-drift induced to E-W along the continental margin i.e. subduction-erosion-induced. The landward dipping Woollard detachment system located at the Upper-Lower slope boundary connects the subduction channel at depth, allowing the Upper slope to evolve independently from the Lower slope wedge. The long-term recurrence interval between earthquakes, the strong interplate coupling, and the aseismic creeping deformation acting along the main low-angle detachments i.e. the Woollard and the Mid-Crust detachments may account for the pervasive seismic gap at the GGTB area. Because the subduction channel exhibits no record of significant seismic activity, no evidence exists to establish a link between the GGTB sustained subsidence and a basin-centered asperity. Because the

New Expansion Dynamics Applied to the Planar Structures of Satellite Galaxies and Space Structuration  [PDF]
Jacques Fleuret
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.716204

Recent observations of Dwarf Satellite Galaxies (DSG) show that they have a clear tendency to stay in particular planes. Explanations with standard physics remain controversial. Recently, I proposed a new explanation of the galactic flat rotation curves, introducing a new cosmic acceleration due to expansion. In this paper, I apply this new acceleration to the dynamics of DSG’s (without dark matter). I show that this new acceleration implies planar structures for the DSG trajectories. More generally, it is shown that this acceleration produces a space structuration around any massive center. It remains a candidate to explain several cosmic observations without dark matter.

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