Simulation of Liquid Flow Permeability for Dendritic Structures during Solidification Process

status: Published onlin

Quantification of the effects of an alpha-2 adrenergic agonist on reflex properties in spinal cord injury using a system identification technique

<p>Abstract</p> <p>Background</p> <p>Despite numerous investigations, the impact of tizanidine, an anti-spastic medication, on changes in reflex and muscle mechanical properties in spasticity remains unclear. This study was designed to help us understand the mechanisms of action of tizanidine on spasticity in spinal cord injured subjects with incomplete injury, by quantifying the effects of a single dose of tizanidine on ankle muscle intrinsic and reflex components.</p> <p>Methods</p> <p>A series of perturbations was applied to the spastic ankle joint of twenty-one spinal cord injured subjects, and the resulting torques were recorded. A parallel-cascade system identification method was used to separate intrinsic and reflex torques, and to identify the contribution of these components to dynamic ankle stiffness at different ankle positions, while subjects remained relaxed.</p> <p>Results</p> <p>Following administration of a single oral dose of Tizanidine, stretch evoked joint torque at the ankle decreased significantly (p < 0.001) The peak-torque was reduced between 15% and 60% among the spinal cord injured subjects, and the average reduction was 25%. Using systems identification techniques, we found that this reduced torque could be attributed largely to a reduced reflex response, without measurable change in the muscle contribution. Reflex stiffness decreased significantly across a range of joint angles (p < 0.001) after using tizanidine. In contrast, there were no significant changes in intrinsic muscle stiffness after the administration of tizanidine.</p> <p>Conclusions</p> <p>Our findings demonstrate that tizanidine acts to reduce reflex mechanical responses substantially, without inducing comparable changes in intrinsic muscle properties in individuals with spinal cord injury. Thus, the pre-post difference in joint mechanical properties can be attributed to reflex changes alone. From a practical standpoint, use of a single "test" dose of Tizanidine may help clinicians decide whether the drug can helpful in controlling symptoms in particular subjects.</p

Simulation of water quality parameters from the treatment of wastewater using stabilization ponds (Case study: Tehran wastewater stabilization pond)

Today, discharging the wastewaters into the river is the main factor of water pollution and associated with environmental impacts. There are several methods for wastewater treatment. The natural ways like wastewater stabilization pond (WSP) is apply in a lot of countries especially in under developed countries because no needed to high technology. The WSP\u2019s are suitable for wastewater treatment in small societies and some special industries like slaughterhouse, dairy products and meat products and etc. The advantages of this way are high efficiency in treatment of pathogens, toxic and organic materials. These ponds treat the wastewater naturally by alga and bacterial reactions. Ecological condition and wastewater properties affect the efficiency of WSP. Furthermore the efficiency of WSPs depends to several factors like the temperature, light, alga and bacterial reactions and Etc and must be analyzed before construction. In this regard the quality parameters in Tehran WSP simulated with CE-QUAL-W2. The model has been calibrated and evaluated on the basis of collected data from Tehran WSP and the ability of the model analyzed to optimum the efficiency. Furthermore the concentration trend of parameters analyzes during the day in different hours to determine the effects of solar radiation and the others parameters on them. The results shows BOD concentration increase at noon and decrease at night that shows it depends to solar radiation. Alga also is a function of solar radiation and the concentration increase in noon and decrease in afternoon. The trend of phosphate and nitrate is the same and since these two parameters are used for growth process of algae so in noon decrease and in night increased. Because at night the growth process of algae is limited and no need for phosphate and nitrate exist so the concentration increased. The results of modeling with CE-QUAL-W2 show good agreement between the experiments and the simulation data and CE-QUAL-W2 is a suitable model for analyzing the quality parameters in WSP and can be used for design of new stabilization ponds or for improving the effluent quality of existing ponds

Liver: An alarm for the heart?

Background/Aims: Fatty liver (FL) and coronary artery disease (CAD) have several risk factors in common, which are usually considered to account for their frequent coexistence. The independent association between FL and angiographic CAD was assessed in this case-control study by considering the contribution of their shared risk factors. Methods: Three hundred and seventeen adult patients who underwent elective coronary angiography (CAG) were recruited immediately after CAG and classified into either of the two groups A (normal or mildly abnormal CAG; n = 85) or B (clinically relevant CAD; n = 232). A liver sonography was performed on the same day as CAG. Results: The groups were significantly different in terms of gender, fasting blood glucose, low-density lipoproteins, diabetes (DM), hypertension and FL. In binary logistic regression, FL was the strongest independent predictor of CAD P < 0.001, odds ratio (OR) = 8.48%, 95% confidence interval (CI) = 4.39-16.40, followed by DM (P = 0.002, OR = 2.94) and male gender (P = 0.014, OR = 2.31). This pattern of associations did not change after clinically significant variables (waist-to-hip ratio, body mass index, triglycerides and high-density lipoproteins) were added to analysis. Conclusion: Fatty liver seems to be a strong independent alarm for the presence of significant CAD. © 2007 Blackwell Munksgaard

Monte Carlo Procedure to Evaluate the E-mobility Impact on the Electric Distribution Grid

The goal of this work is to evaluate the impact of the e-mobility charging processes on the electric grid, in a real-life study case. An effective approach is proposed to study the increase in the energy consumption on the grid with respect to both grid operation and efficiency. The work is developed considering three different recharging technologies, slow (based on domestic users), fast (based on public charging stations), and very fast (based on enhanced public charging stations). Furthermore, three different technologies distributions are evaluated (e.g. different scenarios on charging station deployment are simulated). The results show that fast charging technologies could better fit with e.cars exploitment, but they could cause also a significant stress increase over the grid. The paper is devoted to quantify such effects

Upper limb impairments associated with spasticity in neurological disorders

<p>Abstract</p> <p>Background</p> <p>While upper-extremity movement in individuals with neurological disorders such as stroke and spinal cord injury (SCI) has been studied for many years, the effects of spasticity on arm movement have been poorly quantified. The present study is designed to characterize the nature of impaired arm movements associated with spasticity in these two clinical populations. By comparing impaired voluntary movements between these two groups, we will gain a greater understanding of the effects of the type of spasticity on these movements and, potentially a better understanding of the underlying impairment mechanisms.</p> <p>Methods</p> <p>We characterized the kinematics and kinetics of rapid arm movement in SCI and neurologically intact subjects and in both the paretic and non-paretic limbs in stroke subjects. The kinematics of rapid elbow extension over the entire range of motion were quantified by measuring movement trajectory and its derivatives; i.e. movement velocity and acceleration. The kinetics were quantified by measuring maximum isometric voluntary contractions of elbow flexors and extensors. The movement smoothness was estimated using two different computational techniques.</p> <p>Results</p> <p>Most kinematic and kinetic and movement smoothness parameters changed significantly in paretic as compared to normal arms in stroke subjects (p < 0.003). Surprisingly, there were no significant differences in these parameters between SCI and stroke subjects, except for the movement smoothness (p ≤ 0.02). Extension was significantly less smooth in the paretic compared to the non-paretic arm in the stroke group (p < 0.003), whereas it was within the normal range in the SCI group. There was also no significant difference in these parameters between the non-paretic arm in stroke subjects and the normal arm in healthy subjects.</p> <p>Conclusion</p> <p>The findings suggest that although the cause and location of injury are different in spastic stroke and SCI subjects, the impairments in arm voluntary movement were similar in the two spastic groups. Our results also suggest that the non-paretic arm in stroke subjects was not distinguishable from the normal, and might therefore be used as an appropriate control for studying movement of the paretic arm.</p

Muscle and reflex changes with varying joint angle in hemiparetic stroke

<p>Abstract</p> <p>Background</p> <p>Despite intensive investigation, the origins of the neuromuscular abnormalities associated with spasticity are not well understood. In particular, the mechanical properties induced by stretch reflex activity have been especially difficult to study because of a lack of accurate tools separating reflex torque from torque generated by musculo-tendinous structures. The present study addresses this deficit by characterizing the contribution of neural and muscular components to the abnormally high stiffness of the spastic joint.</p> <p>Methods</p> <p>Using system identification techniques, we characterized the neuromuscular abnormalities associated with spasticity of ankle muscles in chronic hemiparetic stroke survivors. In particular, we systematically tracked changes in muscle mechanical properties and in stretch reflex activity during changes in ankle joint angle. Modulation of mechanical properties was assessed by applying perturbations at different initial angles, over the entire range of motion (ROM). Experiments were performed on both paretic and non-paretic sides of stroke survivors, and in healthy controls.</p> <p>Results</p> <p>Both reflex and intrinsic muscle stiffnesses were significantly greater in the spastic/paretic ankle than on the non-paretic side, and these changes were strongly position dependent. The major reflex contributions were observed over the central portion of the angular range, while the intrinsic contributions were most pronounced with the ankle in the dorsiflexed position.</p> <p>Conclusion</p> <p>In spastic ankle muscles, the abnormalities in intrinsic and reflex components of joint torque varied systematically with changing position over the full angular range of motion, indicating that clinical perceptions of increased tone may have quite different origins depending upon the angle where the tests are initiated.</p> <p>Furthermore, reflex stiffness was considerably larger in the non-paretic limb of stroke patients than in healthy control subjects, suggesting that the non-paretic limb may not be a suitable control for studying neuromuscular properties of the ankle joint.</p> <p>Our findings will help elucidate the origins of the neuromuscular abnormalities associated with stroke-induced spasticity.</p