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Search Results: 1 - 10 of 192012 matches for " Nader D. Nader "
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Failed Weaning from Mechanical Ventilation and Cardiac Dysfunction
Jahan Porhomayon,Peter Papadakos,Nader D. Nader
Critical Care Research and Practice , 2012, DOI: 10.1155/2012/173527
Abstract: Failure to transition patient from controlled mechanical ventilation to spontaneous breathing trials (SBTs) in a timely fashion is associated with significant morbidity and mortality in the intensive care unit. In addition, weaning failures are common in patients with limited cardiac reserves. Recent advances in cardiac echocardiography and laboratory measurement of serum biomarkers to assess hemodynamic response to SBT may provide additional information to guide clinicians to predict weaning outcome. 1. Introduction Weaning critically ill patients from mechanical ventilation (MV) is a gradual and challenging process. Discontinuation of MV should be considered when patient is able to follow commands and maintain appropriate minute ventilation. In addition, protective airway reflexes should be intacts and patient clinical status must have improved. Clinical bedside assessment tools are crucial during the weaning trial (WT) so that ventilator requirements are met as the disease course is corrected. In April 2005, an international consensus conference sponsored by five major scientific societies was held in Budapest, Hungary to provide recommendations regarding the management of weaning process. The main recommendations were as follows: weaning should be considered as early as possible, patients should be divided to three categories (simple, difficult, prolonged weaning), a spontaneous breathing trial (SBT) is the major diagnostic test to determine whether patients can be successfully extubated, the initial trial should last 30 minutes and consist of either tracheal tube (T-Piece) breathing or low levels of pressure support, pressure support or assist-control ventilation modes should be favored in patients failing an initial trial/trials, and noninvasive ventilation techniques should be considered in selected patients to shorten the duration of intubation but should not be routinely used as a tool for extubation failure [1]. In general, mechanical weaning parameters are poor at predicting weaning success because they do not take into account cardiac reserves [2]. Therefore it is necessary for clinicians to understand the cardiovascular response to weaning trials and utilize the available tools to guide the wean team. 2. Physiology of Spontaneous Breathing Trials MV weaning trial can be compared to a cardiac stress test where spontaneous ventilation is a form of an exercise [2], and therefore hemodynamic compromise can occur during weaning process in critically ill patients. The immediate transition from positive pressure mechanical ventilation to
Applications of minimally invasive cardiac output monitors
Jahan Porhomayon, Gino Zadeii, Samuel Congello, Nader D Nader
International Journal of Emergency Medicine , 2012, DOI: 10.1186/1865-1380-5-18
Abstract: The ultimate goal of any hemodynamic monitoring system is to provide the clinicians with additional information on the underlying pathological condition and to guide fluid or vasopressor therapy. Cardiac output measurement and its response to therapeutic interventions are frequently used in critically ill patients. As the use of CO monitoring devices increases today, it is necessary to understand the application of such devices in different clinical settings. For many years pulmonary artery catheter (PAC) thermodilution cardiac output assessment was the monitor of choice for the management of critically ill patients. Thermodilution is a modification of the original indicator dilution techniques in which the injectate has a defined volume and temperature from which the thermodilution curve is generated [1]. As with the other indicator dilution techniques, CO is calculated from the area under the indicator thermodilution curve using the modified Stewart-Hamilton equation [2]. PAC was first used in dogs, and subsequently in humans 50 years later [2]. PAC provides valuable measurements, including right atrial pressure, right ventricular pressures, pulmonary artery pressures, pulmonary artery occlusive pressure, mixed venous saturation (SvO2), and CO. The derived hemodynamic variables are systemic and pulmonary vascular resistances. The major obstacle for the use of PAC has been the lack of demonstrating patient benefit and its level of invasiveness. Several prospective trials have demonstrated the lack of benefit from PACs. The PAC-man trial indicated that the routine placement of PACs had no effect on morbidity or mortality, and the ESCAPE trial found no difference in mortality or length of hospital stay when PAC parameters were compared with clinical assessment in the management of severe congestive heart failure patients [3-6]. Furthermore, for using PAC now, many physicians have lost the training, confidence, and familiarity with its use. PAC should probably be used
A Case of Prolonged Delayed Postdural Puncture Headache in a Patient with Multiple Sclerosis Exacerbated by Air Travel
Jahan Porhomayon,Gino Zadeii,Alireza Yarahamadi,Nader D. Nader
Case Reports in Anesthesiology , 2013, DOI: 10.1155/2013/253218
Abstract:
A Case of Prolonged Delayed Postdural Puncture Headache in a Patient with Multiple Sclerosis Exacerbated by Air Travel
Jahan Porhomayon,Gino Zadeii,Alireza Yarahamadi,Nader D. Nader
Case Reports in Anesthesiology , 2013, DOI: 10.1155/2013/253218
Abstract: The developments of new spinal needles and needle tip designs have reduced the incidence of postdural puncture headache (PDPH). Although it is clear that reducing the loss of CSF leak from dural puncture reduces the headache, there are areas regarding the pathogenesis, treatment, and prevention of PDPH that remain controversial. Air travel by itself may impose physiological alteration in central nervous system that may be detrimental to patients with PDPH. This case report highlights a case of a young female patient who suffered from a severe incapacitating PDPH headache during high-altitude flight with a commercial jet. 1. Introduction The first case report of postdural puncture headache (PDPH) was described in about 100 years ago by Bier and his assistant [1]. It was later postulated that PDPH is triggered by leakage of cerebrospinal fluid through the dural rent, but the cause of the pain is probably due to intracranial arterial and venous dilatation [2]. PDPH remains one of the major complications of spinal tap performed for diagnostic purposes. Other adverse events after lumbar puncture include dysesthesia, backache, nerve palsies, infectious processes, and bleeding disorders [3]. The patterns of development of PDPH depend on a number of procedure and nonprocedure-related risk factors. Knowledge of procedure-related factors supports interventions designed to reduce the incidence of PDPH. Despite the best preventive efforts, PDPH may still occur and be associated with significant morbidity [4, 5]. The potential risks for developing PDPH include female gender [6], young adults, repeated attempt with multiple dural punctures, and the size/type and orientation of the needle [7]. Gender is believed to be an independent risk factor for the development of PDPH as demonstrated by the recent meta-analysis by Wu et al. [6]. Clinical presentation of the PDPH or “spinal headache” is usually described as a severe, dull pain, usually frontal occipital, which is irritated in the upright position and decreased in the supine position. It may or may not be accompanied by nausea, vomiting, and visual/auditory disturbances. The onset of PDPH is between 2 to 72 hours, and latency period of up to 15 days has generally been described in the literature [8, 9]. 2. Case Report This is unique case of a young 23 years old middle Eastern female who developed an acute unilateral eye pain and generalized headache with visual disturbances associated with fatigue and weakness in lower extremities for two days. She presented to a local community hospital and was examined by a
Fabrication of Dual-Axis Solar Tracking Controller Project  [PDF]
Nader Barsoum
Intelligent Control and Automation (ICA) , 2011, DOI: 10.4236/ica.2011.22007
Abstract: The recent decades have seen the increase in demand for reliable and clean form of electricity derived from renewable energy sources. One such example is solar power. The challenge remains to maximize the capture of the rays from the sun for conversion into electricity. This paper presents fabrication and installation of a solar panel mount with a dual-axis solar tracking controller. This is done so that rays from the sun fall perpendicularly unto the solar panels to maximize the capture of the rays by pointing the solar panels towards the sun and following its path across the sky. Thus electricity and efficiency increased.
Acoustic Modeling of a 3-Layered Panel Incorporating Electro-Rheological/ Magneto-Rheological (EMR) Fluids  [PDF]
Nader Mohammadi
Open Journal of Acoustics (OJA) , 2014, DOI: 10.4236/oja.2014.41001
Abstract: Applications of Electro-Rheological (ER) or Magneto-Rheological (MR) fluids as typical smart materials have been widely investigated over the past decades (since their introduction in 40s). The special applications of these materials as a means of noise suppression are not yet investigated. Constrained Layer Damping (CLD) sheets can be realized by incorporating EMR (ER/MR) materials. In this way, a multilayered damping sheet is obtained with adaptive (tunable) stiffness and damping characteristics. These properties are easily changed in proportion to the electric (magnetic) field applied upon the EMR layer. This notion has been introduced for semi-active vibration control problems. Herein, such panels incorporating EMR material are proposed for adaptive acoustic treatments. Modeling (simulation) of a 3-layered panel with the middle layer being EMR with adjustable
Experimental Evaluation of Transmission Loss of a Glass Cylinder Tube Containing a Fluid  [PDF]
Nader Mohammadi
Open Journal of Acoustics (OJA) , 2014, DOI: 10.4236/oja.2014.41002
Abstract: Transmission Loss (TL) of a glass cylinder tube containing a fluid is studied experimentally. This test specimen represents a typical double layer panel including a fluid. The tests are carried out by using a modified four-microphone standing-wave (impedance) tube for specimens with different lengths, 15 and 30 mm. Each cylinder tube is tested filled with one of the fluids at a time. The fluids are air, water, motor oil and a nanoparticle fluid (in absence of magnetic field). The effects of the cylinder length (thickness), impedance tube terminations, and the containing fluid are discussed. The increasing of the thickness led to an increase of the TL values and a decrease in resonance frequencies. Also, the addition of liquid middle layer led to considerable increase of the TL.
Linuron Biologically Effective Dose for Glyphosate-Resistant Giant Ragweed (Ambrosia trifida L.) Control in Soybean (Glycine max L.)  [PDF]
Kimberly D. Walsh, Nader Soltani, Lynette R. Brown, Peter H. Sikkema
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.518285
Abstract:

Glyphosate-resistant (GR) giant ragweed (Ambrosia trifida L.) was first identified in Canada in 2008 and has since been found throughout southwestern Ontario. Six field trials were conducted over a two-year period (2012, 2013) on Ontario farms with GR giant ragweed to evaluate the efficacy of linuron applied pre-plant (PP) in soybean (Glycine max (L.) Merr.). The dose required for 50%, 80%, and 95% GR giant ragweed control was 1238, 2959, and 6018 g·ai·ha-1 four weeks after application (WAA), respectively. The linuron dose needed for 50%, 80%, and 95% reduction in density was 1554, 3181, and 5643 g·ai·ha-1 and 1204, 2496, and 4452 g·ai·ha-1 for dry weight, respectively. Application of 7874 g·ai·ha-1 linuron was needed to obtain soybean yields that were 90% of the weed-free control; approximately 3.5 times the maximum field recommended dose. To achieve 95% and 98% yields, greater than 8640 g·ai·ha-1 linuron was required. Application of linuron plus glyphosate PP in soybean will help to control GR giant ragweed as well as reduce GR selection pressure.

On The Effect of Giant Planets on the Scattering of Parent Bodies of Iron Meteorite from the Terrestrial Planet Region into the Asteroid Belt: A Concept Study
Nader Haghighipour,Edward R. D. Scott
Physics , 2012, DOI: 10.1088/0004-637X/749/2/113
Abstract: In their model for the origin of the parent bodies of iron meteorites, Bottke et al proposed differentiated planetesimals that were formed in the region of 1-2 AU during the first 1.5 Myr, as the parent bodies, and suggested that these objects and their fragments were scattered into the asteroid belt as a result of interactions with planetary embryos. Although viable, this model does not include the effect of a giant planet that might have existed or been growing in the outer regions. We present the results of a concept study where we have examined the effect of a planetary body in the orbit of Jupiter on the early scattering of planetesimals from terrestrial region into the asteroid belt. We integrated the orbits of a large battery of planetesimals in a disk of planetary embryos, and studied their evolutions for different values of the mass of the planet. Results indicate that when the mass of the planet is smaller than 10 Earth-masses, its effects on the interactions among planetesimals and planetary embryos is negligible. However, when the planet mass is between 10 and 50 Earth-masses, simulations point to a transitional regime with ~50 Earth-mass being the value for which the perturbing effect of the planet can no longer be ignored. Simulations also show that further increase of the mass of the planet strongly reduces the efficiency of the scattering of planetesimals from the terrestrial planet region into the asteroid belt. We present the results of our simulations and discuss their possible implications for the time of giant planet formation.
Uniform regularity and vanishing viscosity limit for the free surface Navier-Stokes equations
Nader Masmoudi,Frédéric Rousset
Mathematics , 2012,
Abstract: We study the inviscid limit of the free boundary Navier-Stokes equations. We prove the existence of solutions on a uniform time interval by using a suitable functional framework based on Sobolev conormal spaces. This allows us to use a strong compactness argument to justify the inviscid limit. Our approach does not rely on the justification of asymptotic expansions. In particular, we get a new existence result for the Euler equations with free surface from the one for Navier-Stokes.
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