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Search Results: 1 - 10 of 15059 matches for " Louis-Alexandre Etezad-Heydari "
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Very Slow Search and Reach: Failure to Maximize Expected Gain in an Eye-Hand Coordination Task
Hang Zhang ,Camille Morvan,Louis-Alexandre Etezad-Heydari,Laurence T. Maloney
PLOS Computational Biology , 2012, DOI: 10.1371/journal.pcbi.1002718
Abstract: We examined an eye-hand coordination task where optimal visual search and hand movement strategies were inter-related. Observers were asked to find and touch a target among five distractors on a touch screen. Their reward for touching the target was reduced by an amount proportional to how long they took to locate and reach to it. Coordinating the eye and the hand appropriately would markedly reduce the search-reach time. Using statistical decision theory we derived the sequence of interrelated eye and hand movements that would maximize expected gain and we predicted how hand movements should change as the eye gathered further information about target location. We recorded human observers' eye movements and hand movements and compared them with the optimal strategy that would have maximized expected gain. We found that most observers failed to adopt the optimal search-reach strategy. We analyze and describe the strategies they did adopt.
Characterization of Genes Encoding for Acquired Bacitracin Resistance in Clostridium perfringens
Audrey Charlebois, Louis-Alexandre Jalbert, Josée Harel, Luke Masson, Marie Archambault
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044449
Abstract: Phenotypic bacitracin resistance has been reported in Clostridium perfringens. However, the genes responsible for the resistance have not yet been characterized. Ninety-nine C. perfringens isolates recovered from broilers and turkeys were tested for phenotypic bacitracin resistance. Bacitracin MIC90 (>256 μg/ml) was identical for both turkey and chicken isolates; whereas MIC50 was higher in turkey isolates (6 μg/ml) than in chicken isolates (3 μg/ml). Twenty-four of the 99 isolates showed high-level bacitracin resistance (MIC breakpoint >256 μg/ml) and the genes encoding for this resistance were characterized in C. perfringens c1261_A strain using primer walking. Sequence analysis and percentages of amino acid identity revealed putative genes encoding for both an ABC transporter and an overproduced undecaprenol kinase in C. perfringens c1261_A strain. These two mechanisms were shown to be both encoded by the putative bcrABD operon under the control of a regulatory gene, bcrR. Efflux pump inhibitor thioridazine was shown to increase significantly the susceptibility of strain c1261_A to bacitracin. Upstream and downstream from the bcr cluster was an IS1216-like element, which may play a role in the dissemination of this resistance determinant. Pulsed-field gel electrophoresis with prior double digestion with I-CeuI/MluI enzymes followed by hybridization analyses revealed that the bacitracin resistance genes bcrABDR were located on the chromosome. Semi-quantitative RT-PCR demonstrated that this gene cluster is expressed under bacitracin stress. Microarray analysis revealed the presence of these genes in all bacitracin resistant strains. This study reports the discovery of genes encoding for a putative ABC transporter and an overproduced undecaprenol kinase associated with high-level bacitracin resistance in C. perfringens isolates from turkeys and broiler chickens.
On Eigenvalues and Boundary Curvature of the Numerical Rang of Composition Operators on Hardy Space  [PDF]
Mohammad Taghi Heydari
Advances in Pure Mathematics (APM) , 2015, DOI: 10.4236/apm.2015.56032

For a bounded linear operator A on a Hilbert space H, let M(A) be the smallest possible constant in the inequality \"\". Here, p is a point on the smooth portion of the boundary \"\" of the numerical range of A. \"\" is the radius of curvature of \"\" at this point and \"\"?is the distance from p to the spectrum of A. In this paper,

A mesoscopic model for the rheology of soft amorphous solids, with application to mi- crochannel flows
Alexandre Nicolas,Jean-Louis Barrat
Physics , 2013,
Abstract: We study a mesoscopic model for the flow of amorphous solids. The model is based on the key features identified at the microscopic level, namely peri- ods of elastic deformation interspersed with localised rearrangements of parti- cles that induce long-range elastic deformation. These long-range deformations are derived following a continuum mechanics approach, in the presence of solid boundaries, and are included in full in the model. Indeed, they mediate spatial cooperativity in the flow, whereby a localised rearrangement may lead a distant region to yield. In particular, we simulate a channel flow and find manifestations of spatial cooperativity that are consistent with published experimental obser- vations for concentrated emulsions in microchannels. Two categories of effects are distinguished. On the one hand, the coupling of regions subject to different shear rates, for instance,leads to finite shear rate fluctuations in the seemingly un- sheared "plug" in the centre of the channel. On the other hand, there is convinc- ing experimental evidence of a specific rheology near rough walls. We discuss diverse possible physical origins for this effect, and we suggest that it may be associated with the bumps of particles into surface asperities as they slide along the wall.
Spatial cooperativity in microchannel flows of soft jammed materials: A mesoscopic approach
Alexandre Nicolas,Jean-Louis Barrat
Physics , 2013, DOI: 10.1103/PhysRevLett.110.138304
Abstract: The flow of amorphous solids results from a combination of elastic deformation and local structural rearrangements, which induce non-local elastic deformations. These elements are incorporated into a mechanically-consistent mesoscopic model of interacting elastoplastic blocks. We investigate the specific case of channel flow with numerical simulations, paying particular attention to situations of strong confinement. We find that the simple picture of plastic events embedded in an elastic matrix successfully accounts for manifestations of spatial cooperativity. Shear rate fluctuations are observed in seemingly quiescent regions, and the velocity profiles in confined flows at high applied pressure deviate from those expected in the absence of non-local effects, in agreement with experimental data. However, we suggest a different physical origin for the large deviations observed when walls have rough surfaces, associated with "bumps" of the particles against the asperities of the walls.
Correlation between Interpupillary and Inner-Outer Intercanthal Distances in Individuals Younger than 20
Mohammad Etezad-Razavi,Samira Jalalifar
Journal of Ophthalmic & Vision Research , 2008,
Abstract: PURPOSE: To determine the correlation between interpupillary distance (IPD) and inner-outer intercanthal distance (IOICD) and to find a regression equation for calculating IPD based on IOICD measurements. METHODS: The study subjects were randomly selected from individuals aged 3 months to 20 years who were referred to our ophthalmology clinic, health care centers and children attending kindergartens. Participants were divided into 4 age categories: younger than 3, 3-5, 5-12.5 and 12.5-20 years. IPD was measured by a PD meter (PD2, Oculus, Germany); other parameters including IOICD, nasal limbus to temporal limbus (NLTL), inner intercanthal distance (IICD) and outer intercanthal distance (OICD) were measured using a translucent plastic ruler. RESULTS: The study included 254 female (60.6%) and 165 male (39.4%) subjects with mean age of 87.7±73.2 (range 3-240) months. Significant correlation was observed between IOICD and IPD in the 3-5 yr and 12.5-20 yr age groups. In the younger than 3 and 5-12.5 year age groups, NLTL had the best correlation with IPD. The regression equations for calculating IPD according to IOICD were as follows. In male subjects, near IPD= 0.941×IOICD (r2= 0.98, P < 0.001) and for female subjects, near IPD= 0.948×IOICD (r2= 0.98, P < 0.001). CONCLUSION: IPD and IOICD measurements are strongly and positively correlated; IOICD measurements are simpler to obtain and may be used to calculate IPD readings which are more difficult to measure by usual methods in children.
Intraorbital Arteriovenous Malformation Treated by Transcatheter Embolization; a Case Report
Mohammad Etezad Razavi,Sirous Nekooei,Shahram Afzaly
Journal of Ophthalmic & Vision Research , 2008,
Abstract: PURPOSE: To report the clinical and radiological findings and management of a patient with intraorbital arteriovenous malformation (AVM) treated by transcatheter embolization of the feeding artery. CASE REPORT: A 15-year-old female patient was referred with a one year history of left eye proptosis without prior trauma. Orbital CT scan and MRI demonstrated a large intraconal mass lesion extending to the extraconal space in the inferior orbit; angiograms revealed an intraorbital AVM. Superselective catheterization of the feeding artery and embolization with absorbable gelatin particles (Gelfoam) and non-absorbable polyvinyl alcohol particles were performed in two separate sessions followed by surgical debulking. Signs and symptoms were diminished after 14 months. CONCLUSION: Intraorbital AVMs can be treated by embolization of the feeding artery followed by surgical removal of the AVM nidus when the lesion is accessible.
Bacteremia with Cutaneous Nodules, Due to Pseudomonas Aeruginosa  [PDF]
Ali Akbar Heydari, Maryam Mojtabavi
Advances in Infectious Diseases (AID) , 2011, DOI: 10.4236/aid.2011.12004
Abstract: Pseudomonas aeruginosa bacteremia rarely occurs in non-immunocompromised adults and can be difficult to be treated. We report a case of 35-year-old woman who presented with respiratory distress, fever and skin lesions. There was pleural effusion in chest radiograph, and CT scan of thorax showed necrotizing pneumonia and loculated empyema. Among the cultures of blood, empyema, sputum and the skin nodules aspirates, all were positive for Pseudomonas aeruginosa. The patient was treated with ciprofloxacin, amikacin and then pleural decortications. Laboratory tests failed to reveal any immunological deficits. After a period of 21 days of antibiotic therapy, the patient was discharged from hospital with a good condition.
Absolutely Stable of Takagi-Sugeno Fuzzy Control System by Using Popov’s Criterion  [PDF]
Azhdar Soleymanpour Bakefayat, Aghileh Heydari
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.310165
Abstract: In this paper, we presented a sufficient condition on the frequency domain for the absolutely stable analysis of the Takagi-Sugeno (T-S)fuzzy control system, based on the Popov’s criterion. we use some numerical examples to illustrate the efficiency of frequency domain-based condition.
Application of Nanoparticles in Quartz Crystal Microbalance Biosensors  [PDF]
Somayeh Heydari, Gholam Hossein Haghayegh
Journal of Sensor Technology (JST) , 2014, DOI: 10.4236/jst.2014.42009
Nanoparticles are playing an increasingly important role in the development of biosensors. The sensitivity and performance of biosensors are being improved by using Nanoparticles for their construction. The use of these Nanoparticles has allowed the introduction of many new signal transduction technologies in biosensors. In this report, a comprehensive review of application of nanoparticles in Quartz Crystal Microbalance biosensors is presented. The main advantages of QCM in sensing fields include high sensitivity, high stability, fast response and low cost. In addition, it provides label-free detection capability for bio-sensing applications. Firstly, basic QCM’s design and characterization are described. Next, QCM biosensors based on modification of quartz substrate structure and their applications are digested. Nanoparticles and their utilizationin analysis are then illustrated. These include Nanoparticles in bio applications that cover Nanoparticles in Quartz Crystal Microbalance biosensors.
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