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-Bessel functions in two variables
Hacen Dib
International Journal of Mathematics and Mathematical Sciences , 2003, DOI: 10.1155/s0161171203112057
Abstract: The Bessel-Muirhead hypergeometric system (or 0F1-system) intwo variables (and three variables) is solved using symmetricseries, with an explicit formula for coefficients, in order toexpress the K-Bessel function as a linear combination of theJ-solutions. Limits of this method and suggestions forgeneralizations to a higher rank are discussed.
-Bessel functions associated to a 3-rank Jordan algebra
Hacen Dib
International Journal of Mathematics and Mathematical Sciences , 2005, DOI: 10.1155/ijmms.2005.2863
Abstract: Using the Bessel-Muirhead system, we can express the K-Bessel function defined on a Jordan algebra as a linear combination of the J-solutions. We determine explicitly the coefficients when the rank of this Jordan algebra is three after a reduction to the rank two. The main tools are some algebraic identities developed for this occasion.
Impact of Human Machine Interface Changes on Human Performance and Safety
DIB Abderrahmane
Journal of Engineering and Applied Sciences , 2012,
Abstract: To survive, industry must continue to change technology and diversify human-man machine designs to meet the ever changing needs and requirements of the modern market in terms of performance, reliability, safety and contort. As far as the human operator is concerned with this technological evolutions, he is asked to perform more or less a similar task but with a modified HM interface. Like driving a new car, the driving task remains the same but with different tools of communication with the machine and new aiding systems introduced by the new HM interface. These changes on the interface may affect the operator mental representation and may cause operating errors and accidents. Generally, it is very difficult to assess simply by common sense the impact of changes of interface on human performance of complex systems especially in critical or in emergency situations. This study presents an approach to assess the impact of a Driving Aiding System (DAS) on the performance of human driver and safety. The system DAS is a type of lane keeping which acts by firstly alerting the driver by vibrations on the steering wheel when the trajectory of the vehicle approaches the white lines and secondly, by generating a torque on the steering wheel in a way that keep the position of the vehicle between the while lines. The research is sponsored by PROMOTEUS to develop aiding systems to improve road transport safety.
Optimizing prophylactic treatment of migraine: Subtypes and patient matching
Michel Dib
Therapeutics and Clinical Risk Management , 2008,
Abstract: Michel DibFédération du système nerveux central, H pital de la Salpêtrière, Assistance Publique- H pitaux de Paris, FranceAbstract: Advances in our understanding of the pathophysiology of migraine have resulted in important breakthroughs in treatment. For example, understanding of the role of serotonin in the cerebrovascular circulation has led to the development of triptans for the acute relief of migraine headaches, and the identification of cortical spreading depression as an early central event associated wih migraine has brought renewed interest in antiepileptic drugs for migraine prophylaxis. However, migraine still remains inadequately treated. Indeed, it is apparent that migraine is not a single disease but rather a syndrome that can manifest itself in a variety of pathological conditions. The consequences of this may be that treatment needs to be matched to particular patients. Clinical research needs to be devoted to identifying which sort of patients benefit best from which treatments, particularly in the field of prophylaxis. We propose four patterns of precipitating factors (adrenergic, serotoninergic, menstrual, and muscular) which may be used to structure migraine prophylaxis. Finally, little is known about long-term outcome in treated migraine. It is possible that appropriate early prophylaxis may modify the long-term course of the disease and avoid late complications.Keywords: migraine, diagnosis, treatment, prophylaxis, subtypes
Estimated average glucose: A new term in diabetes control
Dib Jean
Annals of Saudi Medicine , 2010,
Feedback Regulated Star Formation: Implications for the Kennicutt-Schmidt Law
Sami Dib
Physics , 2011, DOI: 10.1088/2041-8205/737/1/L20
Abstract: We derive a metallicity dependent relation between the surface density of the star formation rate (Sigma_{SFR}) and the gas surface density (Sigma_{g}) in a feedback regulated model of star formation in galactic disks. In this model, star formation occurs in gravitationally bound protocluster clumps embedded in larger giant molecular clouds with the protocluster clump mass function following a power law function with a slope of -2. Metallicity dependent feedback is generated by the winds of OB stars (M > 5 Msol) that form in the clumps. The quenching of star formation in clumps of decreasing metallicity occurs at later epochs due to weaker wind luminosities, thus resulting in higher final star formation efficiencies (SFE_{exp}). By combining SFE_{exp} with the timescales on which gas expulsion occurs, we derive the metallicity dependent star formation rate per unit time in this model as a function of Sigma_{g}. This is combined with the molecular gas fraction in order to derive the global dependence of Sigma_{SFR} on Sigma_{g}. The model reproduces very well the observed star formation laws extending from low gas surface densities up to the starburst regime. Furthermore, our results show a dependence of $\Sigma_{SFR}$ on metallicity over the entire range of gas surface densities in contrast to other models, and can also explain part of the scatter in the observations. We provide a tabulated form of the star formation laws that can be easily incorporated into numerical simulations or semi-analytical models of galaxy formation and evolution.
Feedback Regulated Star Formation: From Star Clusters to Galaxies
Sami Dib
Physics , 2011,
Abstract: This paper summarises results from semi-analytical modelling of star formation in protocluster clumps of different metallicities. In this model, gravitationally bound cores form uniformly in the clump following a prescribed core formation efficiency per unit time. After a contraction timescale which is equal to a few times their free-fall times, the cores collapse into stars and populate the IMF. Feedback from the newly formed OB stars is taken into account in the form of stellar winds. When the ratio of the effective wind energy of the winds to the gravitational energy of the system reaches unity, gas is removed from the clump and core and star formation are quenched. The power of the radiation driven winds has a strong dependence on metallicity and increases with increasing metallicity. Thus, winds from stars in the high metallicity models lead to a rapid evacuation of the gas from the protocluster clump and to a reduced star formation efficiency, SFE_{exp}, as compared to their low metallicity counterparts. By combining SFE_{exp} with the timescales on which gas expulsion occurs, we derive the metallicity dependent star formation rate per unit time in this model as a function of the gas surface density Sigma_{g}. This is combined with the molecular gas fraction in order to derive the dependence of the surface density of star formation Sigma_{SFR} on Sigma_{g}. This feedback regulated model of star formation reproduces very well the observed star formation laws extending from low gas surface densities up to the starburst regime. Furthermore, the results show a dependence of Sigma_{SFR} on metallicity over the entire range of gas surface densities, and can also explain part of the scatter in the observations.
Testing the universality of the IMF with Bayesian statistics: young clusters
Sami Dib
Physics , 2014, DOI: 10.1093/mnras/stu1521
Abstract: The universality of the stellar initial mass function (IMF) is tested using Bayesian statistics with a sample of eight young Galactic stellar clusters (IC 348, ONC, NGC 2024, NGC 6611, NGC 2264, $\rho$ Ophiuchi, Chameleon I, and Taurus). We infer the posterior probability distribution function (pPDF) of the IMF parameters when the likelihood function is described by a tapered power law function, a lognormal distribution at low masses coupled to a power law at higher masses, and a multi-component power law function. The inter-cluster comparison of the pPDFs of the IMF parameters for each likelihood function shows that these distributions do not overlap within the $1\sigma$ uncertainty level. Furthermore, the most probable values of the IMF parameters for most of the clusters deviate substantially from their values for the Galactic field stellar IMF. We also quantify the effects of taking into account the completeness correction as well as the uncertainties on the measured masses. The inclusion of the former affects the inferred pPDFs of the slope of the IMF at the low mass end while considering the latter affects the pPDFs of the slope of the IMF in the intermediate- to high mass regime. As variations are observed in all of the IMF parameters at once and for each of the considered likelihood functions, even for completeness corrected samples, we argue that the observed variations are real and significant, at least for the sample of eight clusters considered in this work. The results presented here clearly show that the IMF is not universal.
The evolution of the core mass function by gas accretion
Sami Dib
Physics , 2012,
Abstract: We show how the mass function of dense cores (CMF) which results from the gravoturbulent fragmentation of a molecular cloud evolves in time under the effect of gas accretion. Accretion onto the cores leads to the formation of larger numbers of massive cores and to a flattening of the CMF. This effect should be visible in the CMF of star forming regions that are massive enough to contain high mass cores and when comparing the CMF of cores in and off dense filaments which have different environmental gas densities.
Takotsubo Cardiomyopathy with a Dramatically Rapid Resolution  [PDF]
Muhammad Alichaudhry, Chadi Dib, Ralph Lazzara
International Journal of Clinical Medicine (IJCM) , 2011, DOI: 10.4236/ijcm.2011.22025
Abstract: Takotsubo cardiomyopathy is a relatively rare disease entity with a rapid reversible ventricular dysfunction, which usually occurs in post–menopausal women, and is frequently associated with a stressful event. Diagnosing Takotsubo cardiomyopathy can sometimes be challenging. The absence of coronary artery obstructive disease, and the dramatic presentation of the patient mimicking acute coronary syndrome, make this disease unique. We discuss here a case of Takotsubo cardiomyopathy with extremely rapid resolution in just two days, which we believe is being reported for the first time and touch briefly on the salient features, pathogenesis, diagnosis, treatment, prognosis, and clinical significance of this unique entity.
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