Photonic Crystal Laser Accelerator Structures

Photonic crystals have great potential for use as laser-driven accelerator structures. A photonic crystal is a dielectric structure arranged in a periodic geometry. Like a crystalline solid with its electronic band structure, the modes of a photonic crystal lie in a set of allowed photonic bands. Similarly, it is possible for a photonic crystal to exhibit one or more photonic band gaps, with frequencies in the gap unable to propagate in the crystal. Thus photonic crystals can confine an optical mode in an all-dielectric structure, eliminating the need for metals and their characteristic losses at optical frequencies. We discuss several geometries of photonic crystal accelerator structures. Photonic crystal fibers (PCFs) are optical fibers which can confine a speed-of-light optical mode in vacuum. Planar structures, both two- and three-dimensional, can also confine such a mode, and have the additional advantage that they can be manufactured using common microfabrication techniques such as those used for integrated circuits. This allows for a variety of possible materials, so that dielectrics with desirable optical and radiation-hardness properties can be chosen. We discuss examples of simulated photonic crystal structures to demonstrate the scaling laws and trade-offs involved, and touch on potential fabrication processes.Comment: 3 pages, 3 figures; Submitted to Particale Accelerator Conference (PAC 2003), May 12-16, 2003, Portland, Oregon (IEEE

Early prevention by L-Arginine attenuates coronary atherosclerosis in a model of hypercholesterolemic animals; no positive results for treatment

<p>Abstract</p> <p>Background</p> <p>Endothelial dysfunction (ED) is an independent predictor of cardiovascular events. ED is also a reversible disorder, and nitric oxide donors like L-arginine may promote this process. Despite the positive results from several studies, there are some studies that have shown that L-arginine administration did not improve endothelium-dependent dilation or the inflammatory state of patients. In this study the early and the late effects of L-arginine on coronary fatty streak formation and ED biomarkers were considered in hypercholesterolemic rabbits.</p> <p>Methods</p> <p>36 white male rabbits randomly assigned in 3 groups. Rabbits were fed 1% high-cholesterol diet (LP group, n = 15), or high-cholesterol diet with oral L-arginine (3% in drinking water) (EP group, n = 15) or standard diet (control group, n = 6) for 4 weeks (phase I). Afterward, all animals were fed normal diet for 4 weeks (phase II). In the second phase, L-arginine was discontinued for EP group and was begun for LP group. The plasma levels of lipids, von Willebrand factor (vWF), and nitrite were compared before and after 4 and 8 weeks of experiment. Coronary fatty streak formation was measure after 4 and 8 weeks of experiment.</p> <p>Results</p> <p>The plasma levels of lipids were increased significantly in both groups of LP and EP after phase I. The hypercholesterolemia induced significant increased vWF release in LP group. The L-arginine supplementation led to significant plasma nitrite increment in EP group. The vWF in LP group was higher than other groups (p < 0.05). By the end of phase II, despite of start of L-arginine supplementation for LP group and L-arginine discontinuation in EP group, there were significantly more fatty streaks lesions in LP group coronary arteries than EP group. Furthermore, L-arginine supplementation did not result in significant nitrite increment in LP group.</p> <p>Conclusion</p> <p>Early prevention by L-arginine may be helpful to prevent the ED, but our study did not suggest the treatment. It seems reasonable to consider ED-aside from control the cardiovascular risk factors in primary prevention of atherosclerosis and its clinical outcomes before development of irreversible vascular damage.</p

The comparison of stress coping styles between athletes and non-athletes and its relationship with mental health

Background and aims: Stress and anxiety are important factors that can highly affect athletes’ performance. They can also influence the mental and physical heath of the athletes. The aim of this study was to compare the stress-coping styles in two groups of athletes and non-athletes and evaluating its relationship with their mental health. Methods: One hundred athletes were selected randomly and 100 non-athletes were voluntarily participated in this study. Both groups answered the standard Yoo coping-styles and Goldberg general health questionnaires. Relevant statistical tests were used for data analysis. Results: Athletes in comparison with non-athletes used problem-focused and emotion-focused coping styles more frequently, but, they used avoidant-coping styles less frequently (P<0.01). Also, in the former group, while the application of problem- and emotion-focused coping-styles were correlated with increase in mental health, avoidant-coping styles were correlated with decrease in mental health. In contrast, in non-athletes, using problem-focused and avoidant coping styles were correlated with increase and decrease in mental health, respectively (P<0.05). Regression analysis demonstrated that stress-coping styles could largely predict the mental health variation in athletes and non-athletes groups (P<0.05). Conclusion: Findings of this study provide more support for the importance of coping styles and its relationship with mental health in stress situations such as sport fields

LArginine supplementation influenced nitrite but not nitrate and total nitrite in rabbit model of hypercholesterolemia

ABSTRACT Background: The assessment of altered nitric oxide (NO) availability is of potentially important diagnostic and prognostic significance. The present study is aimed to investigate the effect of L-arginine (as a natural NO donor) supplementation on NO metabolite in a rabbit model of hypercholesterolemia to find a reliable marker for endothelial NO production. Methods: White male rabbits (n = 30) randomly assigned to 2 groups. Rabbits were fed 1% high-cholesterol diet (HC group, n = 15), or HC diet with oral L-arginine (3% in drinking water) (HC + L-arginine group, n = 15) for 4 weeks. The serum levels of lipids, L-arginine, total NO metabolites (NOx), nitrite and nitrate were measured before and after the study. Results: In this study, Larginine supplementation led to a significant increased plasma level of L-arginine. The serum level of nitrite was significantly higher in L-arginine treated group while serum level of nitrate and NOx was significantly lower than HC group. Conclusion: As the result of our study showed, nitrite is a useful marker of endogenous endothelial NO production and although frequently used, neither nitrate nor NOx are reliable markers of acute changes in endothelial NO synthase activity

MEMS Sensor Development for In-Situ Quantification of Toxic Metals in Sediment

69A3551847102In this project, we developed a novel, integrated on-chip sample-to-answer platform capable of detecting lead ions (Pb +2 ) directly in sediment samples. As sediment is one of the main sources of hazardous heavy metals in aquatic ecosystems, rapid and real-time detection of heavy metals in sediment is crucial in the field of environmental monitoring. Electrochemical sensors can provide rapid detection capability, but in-situ measurement of heavy metals with such sensors has been limited by complicated pretreatment steps. To overcome this drawback, an integrated system was developed consisting of a porous matrix for purification and extraction of Pb +2 onto a graphene oxide thin film that serves as an active sensing material. The integrated sensor with a 3D porous matrix was used as an in-situ platform to detect lead directly in complex sediment samples. The proposed electrochemical sensor has a detection limit of 4 ppb and a linear working range. The ability to directly detect lead in sediment samples with minimal pretreatment agents and time makes this system a promising solution for on-site monitoring of heavy metals in environmental samples. Although the current study focused on lead for platform validation, the proposed sensing platform can be further developed for the detection of a wide panel of toxic metals

The relationship of air pollution and surrogate markers of endothelial dysfunction in a population-based sample of children

<p>Abstract</p> <p>Background</p> <p>This study aimed to assess the relationship of air pollution and plasma surrogate markers of endothelial dysfunction in the pediatric age group.</p> <p>Methods</p> <p>This cross-sectional study was conducted in 2009-2010 among 125 participants aged 10-18 years. They were randomly selected from different areas of Isfahan city, the second large and air-polluted city in Iran. The association of air pollutants' levels with serum thrombomodulin (TM) and tissue factor (TF) was determined after adjustment for age, gender, anthropometric measures, dietary and physical activity habits.</p> <p>Results</p> <p>Data of 118 participants was complete and was analyzed. The mean age was 12.79 (2.35) years. The mean pollution standards index (PSI) value was at moderate level, the mean particular matter measuring up to 10 μm (PM₁₀) was more than twice the normal level. Multiple linear regression analysis showed that TF had significant relationship with all air pollutants except than carbon monoxide, and TM had significant inverse relationship with ozone. The odds ratio of elevated TF was significantly higher in the upper vs. the lowest quartiles of PM₁₀, ozone and PSI. The corresponding figures were in opposite direction for TM.</p> <p>Conclusions</p> <p>The relationship of air pollutants with endothelial dysfunction and pro-coagulant state can be an important factor in the development of atherosclerosis from early life. This finding should be confirmed in future longitudinal studies. Concerns about the harmful effects of air pollution on children's health should be considered a top priority for public health policy; it should be underscored in primordial and primary prevention of chronic diseases.</p

MEASURING THE DELAY IN CHANNEL SWITCHING AND ITS OPTIMIZATION IN IPTV NETWORKS BY PRE-JOINING METHOD OF TV CHANNELS

Providing television services over IP networks is a very attractive offer. As a new source of revenue offers for network operators, IPTV offers greater flexibility to network operators and provides a wide range of applications for users. to compete in this market, IPTV operators must guarantee at least the same quality of experience in this respect one of the main concerns is to delay in channel switching which is known as zapping delay zapping time in an IPTV network may be last 2 seconds or more Many efforts to reduce the channel switching delay has been done in IPTV network, One of these methods is the predictive adjustment which is called pre-joining. In this way with any request for watching the favorite TV channel, not only the desired channel stream, but also some other channels are added and sent to the client. However, it is required to use more bandwidth on the network. In this study an improved predictability adjustment is researched, the behavior of the user channel selection with SEMI-MARKO process is analyzed and we can estimate the average time of channel change and the average used bandwidth. The optimum number of pre-joining channels in a periodic time is also checked. For the accuracy of selection a simulation is done. Studies show that the proposed method leads to less time to change the channel with the least available bandwidth

LATE TREATMENT WITH L-ARGININE INCREASES 8-ISOPROSTAGLANDIN F2Α AND OXIDIZED LDL IN HYPERCHOLESTEROLEMIC RABBITS

Abstract &nbsp;&nbsp; BACKGROUND: The role of L-arginine, the precursor of nitric oxide, on the oxidative stress and atherosclerosis has been previously studied; it has had inconsistent beneficial effects. The aim of this study was to investigate whether administration of L-arginine reduces oxidative stress and the progression of atherosclerosis in cholesterol fed rabbits. &nbsp;&nbsp; METHODS: Eighteen white male rabbits were randomized into three groups. All of them received 1% high cholesterol diet for the first four weeks and normal diet for the second four weeks of the experiment. The early treatment (ET) group received L-arginine (3% in drinking water) in the first four weeks while the late treatment (LT) group received L-arginine for the second four weeks of the experiment. Control (C) group received no L-arginine. The plasma levels of lipids, 8-isoprostaglandin F2&alpha;, CRP and oxLDL were measured before, and at 4th and 8th weeks of the experiment. Aorta fatty streak formation was measured at the end of the experiment. &nbsp;&nbsp; RESULTS: The plasma levels of lipids were increased significantly during the first 4 weeks and decreased significantly during the second 4 weeks with no significant differences between the groups. The plasma concentration of 8-isoprostaglandin F2&alpha; was significantly decreased in the ET group compared with the C group at the end of the experiment. The fatty streak formation in the ET group was significantly lower than that in the C group at the end of the experiment. The plasma concentration of CRP significantly increased after 4 weeks administration of hypercholesterolemic diet in all groups. Also, its amount was significantly smaller in ET group in comparison with other groups. The plasma concentration of oxLDL decreased significantly in the ET group compared with LT group at the end of the experiment. However, the plasma concentration of oxLDL increased in the C group and in the LT group at the end of the experiment. &nbsp;&nbsp; CONCLUSION: L-arginine therapy from the very beginning of hypercholesterolemia reduced oxidative stress and the consequential irreversible vascular damage, and may be useful for primary prevention. &nbsp; &nbsp;&nbsp; Keywords: Atherosclerosis, Oxidized Low Density Lipoproteins, Oxidative Stress, 8-Isoprostaglandin F2&alpha;, L-Arginine, Nitric Oxide.</p