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Search Results: 1 - 10 of 4741 matches for " Jacques Bou Abdo "
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Security V/S Qos for LTE Authentication and Key Agreement Protocol
Jacques Bou Abdo,Jacques Demerjian,Hakima Chaouchi
International Journal of Network Security & Its Applications , 2012,
Abstract: Protocol and technology convergence, the core of near future communication, will soon be forming theinteroperating heterogeneous networks. Attaining a strict secure authentication without risking the QoSperformance and call success rates is a major concern when it comes to wireless heterogeneousnetworks. In order to achieve this, a generic, fast and secure, Authentication and Key Agreement protocolis to be used; a version of which is to be implemented between each two technologies. In this research,different existing EPS-EPS AKA protocols will be compared with our proposed protocol EC-AKA(Ensure Confidentiality Authentication and Key Agreement) based on security, cost effectiveness,signaling overhead, delay and performance. It is proven that EC-AKA is the exclusive protocol satisfyingthe New Generation Network’s KPIs and it will be promoted as the target generic AKA protocol inheterogeneous networks.
25 years’ experience in the management of pilonidal sinus disease  [PDF]
Doureid Oueidat, Alain Rizkallah, Mahmoud Dirani, Tarek Bou Assi, Ali Shams, Abdo Jurjus
Open Journal of Gastroenterology (OJGas) , 2014, DOI: 10.4236/ojgas.2014.41001
Abstract:

Pilonidal sinus disease is a common medical condition that accounts for almost 15% of anal suppurations with high morbidity. Its management is subject to many variations. In this study, a 25-year experience from 1984 to 2009 of treating pilonidal sinus disease is being reported. A total of 252 patients were included in the study. They were treated by phenol injection, excision and primary closure, or excision and packing. Data showed that excision with packing had the highest cure rate (85%), followed by excision and primary closure (65%), and then phenol (55%). As for the healing duration, the shortest was for excision and primary closure, followed by the phenol injection. However, excision and packing had the least recurrence rate (12%), compared to phenol and excision with primary closure 26.5% and 23%, respectively. The authors recommended excision and packing. However, hospital stay, missed days of work, recurrence rates, and the surgeon’s familiarity with the techniques were important factors in the choice of treatment modality.

A collisionless scenario for Uranus tilting
Gwena?l Boué,Jacques Laskar
Physics , 2009, DOI: 10.1088/2041-8205/712/1/L44
Abstract: The origin of the high inclination of Uranus' spin-axis (Uranus' obliquity) is one of the great unanswered questions about the Solar system. Giant planets are believed to form with nearly zero obliquity, and it has been shown that the present behaviour of Uranus' spin is essentially stable. Several attempts were made in order to solve this problem. Here we report numerical simulations showing that Uranus' axis can be tilted during the planetary migration, without the need of a giant impact, provided that the planet had an additional satellite and a temporary large inclination. This might have happened during the giant planet instability phase described in the Nice model. In our scenario, the satellite is ejected after the tilt by a close encounter at the end of the migration. This model can both explain Uranus' large obliquity and bring new constraints on the planet orbital evolution.
Speed limit on Neptune migration imposed by Saturn tilting
Gwena?l Boué,Jacques Laskar,Petr Kuchynka
Physics , 2009, DOI: 10.1088/0004-637X/702/1/L19
Abstract: In this Letter, we give new constraints on planet migration. They were obtained under the assumption that Saturn's current obliquity is due to a capture in resonance with Neptune's ascending node. If planet migration is too fast, then Saturn crosses the resonance without being captured and it keeps a small obliquity. This scenario thus gives a lower limit on the migration time scale tau. We found that this boundary depends strongly on Neptune's initial inclination. For two different migration types, we found that tau should be at least greater than 7 Myr. This limit increases rapidly as Neptune's initial inclination decreases from 10 to 1 degree. We also give an algorithm to know if Saturn can be tilted for any migration law.
Pumping the eccentricity of exoplanets by tidal effect
Alexandre C. M. Correia,Gwena?l Boué,Jacques Laskar
Physics , 2011, DOI: 10.1088/2041-8205/744/2/L23
Abstract: Planets close to their host stars are believed to undergo significant tidal interactions, leading to a progressive damping of the orbital eccentricity. Here we show that, when the orbit of the planet is excited by an outer companion, tidal effects combined with gravitational interactions may give rise to a secular increasing drift on the eccentricity. As long as this secular drift counterbalances the damping effect, the eccentricity can increase to high values. This mechanism may explain why some of the moderate close-in exoplanets are observed with substantial eccentricity values.
Tidal dissipation in multi-planet systems and constraints to orbit-fitting
Jacques Laskar,Gwena?l Boué,Alexandre C. M. Correia
Physics , 2011, DOI: 10.1051/0004-6361/201116643
Abstract: We present here in full details the linear secular theory with tidal damping that was used to constraint the fit of the HD10180 planetary system in (Lovis et al. 2011). The theory is very general and can provide some intuitive understanding of the final state of a planetary system when one or more planets are close to their central star. We globally recover the results of (Mardling 2007), but we show that in the HD209458 planetary system, the consideration of the tides raised by the central star on the planet lead to believe that the eccentricity of HD209458b is most probably much smaller than 0.01.
A simple model of the chaotic eccentricity of Mercury
Gwena?l Boué,Jacques Laskar,Fran?ois Farago
Physics , 2012, DOI: 10.1051/0004-6361/201219991
Abstract: Mercury's eccentricity is chaotic and can increase so much that collisions with Venus or the Sun become possible (Laskar, 1989, 1990, 1994, 2008, Batygin & Laughlin, 2008, Laskar & Gastineau, 2009). This chaotic behavior results from an intricate network of secular resonances, but in this paper, we show that a simple integrable model with only one degree of freedom is actually able to reproduce the large variations in Mercury's eccentricity, with the correct amplitude and timescale. We show that this behavior occurs in the vicinity of the separatrices of the resonance g1-g5 between the precession frequencies of Mercury and Jupiter. However, the main contribution does not come from the direct interaction between these two planets. It is due to the excitation of Venus' orbit at Jupiter's precession frequency g5. We use a multipolar model that is not expanded with respect to Mercury's eccentricity, but because of the proximity of Mercury and Venus, the Hamiltonian is expanded up to order 20 and more in the ratio of semimajor axis. When the effects of Venus' inclination are added, the system becomes nonintegrable and a chaotic zone appears in the vicinity of the separatrices. In that case, Mercury's eccentricity can chaotically switch between two regimes characterized by either low-amplitude circulations or high-amplitude librations.
Evaluation of Methods for the Extraction and Purification of DNA from the Human Microbiome
Sanqing Yuan, Dora B. Cohen, Jacques Ravel, Zaid Abdo, Larry J. Forney
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0033865
Abstract: Background DNA extraction is an essential step in all cultivation-independent approaches to characterize microbial diversity, including that associated with the human body. A fundamental challenge in using these approaches has been to isolate DNA that is representative of the microbial community sampled. Methodology/Principal Findings In this study, we statistically evaluated six commonly used DNA extraction procedures using eleven human-associated bacterial species and a mock community that contained equal numbers of those eleven species. These methods were compared on the basis of DNA yield, DNA shearing, reproducibility, and most importantly representation of microbial diversity. The analysis of 16S rRNA gene sequences from a mock community showed that the observed species abundances were significantly different from the expected species abundances for all six DNA extraction methods used. Conclusions/Significance Protocols that included bead beating and/or mutanolysin produced significantly better bacterial community structure representation than methods without both of them. The reproducibility of all six methods was similar, and results from different experimenters and different times were in good agreement. Based on the evaluations done it appears that DNA extraction procedures for bacterial community analysis of human associated samples should include bead beating and/or mutanolysin to effectively lyse cells.
Anisotropic Reinforcement of Nanocomposites Tuned by Magnetic Orientation of the Filler Network
Jacques Jestin,Fabrice Cousin,Isabelle Dubois,Christine Ménager,Ralph Schweins,Julian Oberdisse,Fran?ois Boué
Physics , 2009, DOI: 10.1002/adma.200702758
Abstract: We present a new material which displays anisotropic and mechanical properties tuneable during synthesis under magnetic field. It is formulated by mixing aqueous suspensions of polymer nanolatex and magnetic nanoparticles, coated by a thin silica layer to improve their compatibility with the polymeric matrix, followed by casting. The magnetic properties of these nanoparticles enable their pre-orientation in the resulting nanocomposite when cast under magnetic field. Detailed insight on dispersion by Small Angle Neutron Scattering (SANS) shows chainlike nanoparticle aggregates aligned by the field on the nanometer scale. Applying strain to the nanocomposite parallel to the particle chains shows higher mechanical reinforcement, than when strain is transverse to field. . SANS from strained samples shows that strain parallel to the field induce an organization of the chains while strain perpendicular to the field destroys the chain field-induced ordering. Thus improved mechanical reinforcement is obtained from anisotropic interconnection of nanoparticle aggregates.
Polystyrene grafting from silica nanoparticles via Nitroxide-Mediated-Polymerization (NMP): synthesis and SANS analysis with contrast variation method
Chloé Chevigny,Didier Gigmes,Denis Bertin,Jacques Jestin,Fran?ois Boué
Physics , 2010, DOI: 10.1039/b906754j
Abstract: We present a new convenient and efficient "grafting from" method to obtain well defined polystyrene (PS) silica nanoparticles. The method, based on Nitroxide-Mediated Polymerization (NMP), consists to bind covalently the alkoxyamine, which acts as initiator controller agent, at the silica nanoparticles surface in two steps. The first step is a reaction between the aminopropylsilane and the silica particles in order to functionalize the particles surface with amino group. In a second step, the initiating-controlling alkoxyamine moiety is introduced via an over grafting reaction between the amino group and the N-hydroxysuccinimide based MAMA-SG1 activated ester. To simplify both their chemical transformation and the polymerization step, the native silica particles, initially dispersed in water, have been transferred in an organic solvent, the dimethylacetamide, which is also a good solvent for the polystyrene. The synthesis parameters have been optimized for grafting density, conversion rates, and synthesis reproducibility while keeping the colloidal stability and to avoid any aggregation of silica particles induced by the inter-particles interaction evolution during the synthesis. After synthesis, the final grafted objects have been purified and the non-grafted polymer chains formed in the solvent have been washed out by ultra filtration. Then the particles have been studied using Small angle Neutron Scattering (SANS) coupled to neutron contrast variation method. To optimize the contrast conditions, both hydrogenated and deuterated monomers have been used for the synthesis. A refined fitting analysis based on the comparison on two models, a basic core-shell and the Gaussian Pedersen model, enables us to fit nicely the experimental data for both the hydrogenated and deuterated grafted case. Differences are seen between grafting of normal or deuterated chains which can be due to monomer reactivity or to neutron contrast effect variations. The synthesis and the characterization method established in this work constitute a robust and reproducible way to design well defined grafted polymer nanoparticles. These objects will be incorporated in polymer matrices in a further step to create Nanocomposites for polymer reinforcement.
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