Zirconia toughened SiC whisker reinforced alumina composites small business innovation research

The objective of this phase 1 project was to develop a ceramic composite with superior fracture toughness and high strength, based on combining two toughness inducing materials: zirconia for transformation toughening and SiC whiskers for reinforcement, in a controlled microstructure alumina matrix. The controlled matrix microstructure is obtained by controlling the nucleation frequency of the alumina gel with seeds (submicron alpha-alumina). The results demonstrate the technical feasibility of producing superior binary composites (Al2O3-ZrO2) and tertiary composites (Al2O3-ZrO2-SiC). Thirty-two composites were prepared, consolidated, and fracture toughness tested. Statistical analysis of the results showed that: (1) the SiC type is the key statistically significant factor for increased toughness; (2) sol-gel processing with a-alumina seed had a statistically significant effect on increasing toughness of the binary and tertiary composites compared to the corresponding mixed powder processing; and (3) ZrO2 content within the range investigated had a minor effect. Binary composites with an average critical fracture toughness of 6.6MPam sup 1/2, were obtained. Tertiary composites with critical fracture toughness in the range of 9.3 to 10.1 MPam sup 1/2 were obtained. Results indicate that these composites are superior to zirconia toughened alumina and SiC whisker reinforced alumina ceramic composites produced by conventional techniques with similar composition from published data

Ultrafast electron dynamics and cubic optical nonlinearity of free standing thin film of double walled carbon nanotubes

Ultrafast degenerate pump-probe experiments performed on a free standing film of double walled carbon nanotubes near the first metallic transition energy of outer tube show ultrafast ($97 fs$) photobleaching followed by a photo-induced absorption with a slow relaxation of $1.8 ps$. Femtosecond closed and open aperture z-scan experiments carried out at the same excitation energy show saturation absorption and negative cubic nonlinearity. From these measurements, real and imaginary part of the third order nonlinear susceptibility are estimated to be Re($\chi^{(3)}) \sim -2.2 \times 10 ^{-9} esu$ and Im($\chi^{(3)}) \sim 1.1 \times 10 ^{-11} esu$.Comment: 8 pages, 3 figure

Gas pressure sintering of silicon nitride

The Cooperative Research and Development Agreement (CRADA) with Materials and Electrochemical Research Corp. (MER) examined materials made with different starting {alpha}/{beta}Si{sub 3}N{sub 4} ratios and with the addition of sintering aids as coatings instead of powders. The samples were sintered by GPS using optimum densification parameters developed for high toughness materials in the ORNL program. High densities were achieved for all of the samples fabricated at ORNL and containing up to 50% {beta}-Si{sub 3}N{sub 4}. The effect of the type of {beta}-Si{sub 3}N{sub 4} seed on fluxural strength and fracture toughness indicated seeds fabricated by the reaction of either yttrium nitrate or Y{sub 2}O{sub 3} powder and Ube E-10 Si{sub 3}N{sub 4} developed materials with the highest flexural strength. However, the fracture toughness of these materials (at the 25% addition level) showed no improvement over the baseline composition having no {beta}-seed addition. The effects of the {beta}-seed content on flexural strength and fracture toughness were mixed. Higher toughnesses were observed with 50% {beta}-seed additions, while the other additive levels showed no consistent improvements

Open-Circuit Photovoltage and Charge Recombination at Semiconductor/Liquid Interfaces

The open-circuit photovoltage (Voc) of semiconductor/ liquid junction solar cells is a critical parameter in determining the energy conversion efficiency. The fundamental process controlling Voc is the recombination of photoexcited electrons and holes. 1' 2 The lower the recombination rate, the larger the Voc. The predominant energy-loss mechanism is determined by competition among the following processes: majority-carrier thermionic emission over the surface barrier, ~ majority-carrier charge transfer across the semiconductor/liquid interface, ~' 4 minority-carrier diffusion/recombination in the bulk of the semiconductor, ~' 8 space-charge recombination, 7 and surface recombination mediated by recombination centers. 8-13 The extent to which each of these processes is understood differs considerably. For example, expressions describing the minority-carrier diffusion/recombination in the bulk semiconductor contacting a redox electrolyte is obtained by direct analogy to formulas developed for solid-state p-n junction devices. ~ When bulk diffusion/recombination is the dominant recombination process, the dependence of Vo~ on the semiconductor bandgap, doping level, and minority-carrier diffusion length can be expressed in simple analytic forms? In contrast, surface recombination has generally been treated in a more complex fashion by numerical simulation. TM In cases in which Voe is limited by surface recombination, no simple analytic expression exists for relating Vo~ and the surface recombination velocity (Sr)-Several groups TM have considered theoretically the effect of surface recombination on the performance of photoelectrochemical (PEC) cells. Although each treatment has achieved some success in describing a certain aspect of the effect of surface recombination, these treatments are generally considered qualitative3 ~ For the most part, it has been difficult to extract quantitative information on surface recombination from * Electrochemical Society Active Member. Visiting professor, on leave of absence from Korea University, Seoul, Korea. experimental results because of the number of adjustable (and often arbitrary) parameters involved in numerical analyses. Up to now, only one study 11 has dealt directly with the dependence of Voc on the surface recombination current; however, because bias-independent surface recombination currents in arbitrary units were used in the numerical calculation, it is difficult to apply the model of this study for interpreting quantitatively experimental measurements. Other studies 8-I~ have focused mainly on the general shape of the photocurrent-voltage (J-V) curves, without addressing the dependence of Voo on Sr. b The absence of a theoretical framework relating Sr to Vo~ impedes the understanding of such processes at the solid/liquid interface. In this article, we derive a simple quantitative expression, based on semiconductor solid-state theory, that directly relates Sr to Voc. The applicability of the expression to account for the PEC behavior of n-St/acetone with FeCp~ j~ (ferrocenium ion/ferrocene) is then investigated. Based on J-Vdata and the dependence of Voe on both the temperature and the concentration of FeCp~, we are able to exclude other possible recombination channels and identify surface recombination as the dominant recombination process in determining Voc. The surface recombination velocity deduced from experimental results compares favorably with reported values. The application of the analytic expression to other PEC systems reported in the literature is also discussed. b The effect of surface recombination is generally discussed in terms of the photoeurrent onset potential. However, unlike the concept of the "open-circuit photovoltage," the "photoeurrent onset potential" is an empirical quantity that cannot be precisely defined. The photocurrent onset potential depends on both Voc and the fill factor. The latter two parameters are more definable quantities and are more relevant in calculating the PEC conversion efficiency

Sexual and reproductive health and human rights of women living with HIV

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138378/1/jia20834-sup-0001.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138378/2/jia20834.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138378/3/jia20834-sup-0002.pd

Randomized Clinical Trial on Ivermectin versus Thiabendazole for the Treatment of Strongyloidiasis

Strongyloidiasis is the infection caused by the worm Strongyloides stercoralis. Due to its peculiar life cycle Strongyloides may remain indefinitely in the host, if not effectively cured. Although the disease is usually mild, in case of weakening of the host's immune defenses the worm may invade virtually all organs and tissues (disseminated strongyloidiasis, almost invariably fatal). The treatment must then reach the goal of the complete elimination of the parasite. Small size clinical trials showed similar, high efficacy of the two drugs ivermectin (used as a single dose) and thiabendazole (used twice daily for two consecutive days). All trials used as the criterion for cure the absence of larvae in stool exams. The latter however may easily miss the infection, falsely suggesting that the infection has been cured. This trial, using a test detecting specific Strongyloides antibodies as an additional and more sensitive diagnostic tool, confirms previous reports: the two drugs have similar efficacy but ivermectin is better tolerated and is therefore the first choice. However the cure rate was lower than 70% for the standard, single dose. The authors then conclude that a larger, multi center trial is needed to find the optimal dose schedule of ivermectin

Chronic hepatitis c genotype-4 infection: role of insulin resistance in hepatocellular carcinoma

<p>Abstract</p> <p>Background</p> <p>Hepatitis C virus (HCV) is a major cause of chronic hepatitis and hepatocellular carcinoma (HCC) and different HCV genotypes show characteristic variations in their pathological properties. Insulin resistance (IR) occurs early in HCV infection and may synergize with viral hepatitis in HCC development. Egypt has the highest reported rates of HCV infection (predominantly genotype 4) in the world; this study investigated effects of HCV genotype-4 (HCV-4) on prevalence of insulin resistance in chronic hepatitis C (CHC) and HCC in Egyptian patients.</p> <p>Methods</p> <p>Fifty CHC patients, 50 HCC patients and 20 normal subjects were studied. IR was estimated using HOMA-IR index and HCV-4 load determined using real-time polymerase chain reaction. Hepatitis B virus was excluded by enzyme-linked immunosorbent assay. Standard laboratory and histopathological investigations were undertaken to characterize liver function and for grading and staging of CHC; HCC staging was undertaken using intraoperative samples.</p> <p>Results</p> <p>HCC patients showed higher IR frequency but without significant difference from CHC (52% vs 40%, p = 0.23). Multivariate logistic regression analysis showed HOMA-IR index and International Normalization Ratio independently associated with fibrosis in CHC; in HCC, HbA1c, cholesterol and bilirubin were independently associated with fibrosis. Fasting insulin and cholesterol levels were independently associated with obesity in both CHC and HCC groups. Moderate and high viral load was associated with high HOMA-IR in CHC and HCC (p < 0.001).</p> <p>Conclusions</p> <p>IR is induced by HCV-4 irrespective of severity of liver disease. IR starts early in infection and facilitates progression of hepatic fibrosis and HCC development.</p

Intestinal strongyloidiasis and hyperinfection syndrome

In spite of recent advances with experiments on animal models, strongyloidiasis, an infection caused by the nematode parasite Strongyloides stercoralis, has still been an elusive disease. Though endemic in some developing countries, strongyloidiasis still poses a threat to the developed world. Due to the peculiar but characteristic features of autoinfection, hyperinfection syndrome involving only pulmonary and gastrointestinal systems, and disseminated infection with involvement of other organs, strongyloidiasis needs special attention by the physician, especially one serving patients in areas endemic for strongyloidiasis. Strongyloidiasis can occur without any symptoms, or as a potentially fatal hyperinfection or disseminated infection. Th(2 )cell-mediated immunity, humoral immunity and mucosal immunity have been shown to have protective effects against this parasitic infection especially in animal models. Any factors that suppress these mechanisms (such as intercurrent immune suppression or glucocorticoid therapy) could potentially trigger hyperinfection or disseminated infection which could be fatal. Even with the recent advances in laboratory tests, strongyloidiasis is still difficult to diagnose. But once diagnosed, the disease can be treated effectively with antihelminthic drugs like Ivermectin. This review article summarizes a case of strongyloidiasis and various aspects of strongyloidiasis, with emphasis on epidemiology, life cycle of Strongyloides stercoralis, clinical manifestations of the disease, corticosteroids and strongyloidiasis, diagnostic aspects of the disease, various host defense pathways against strongyloidiasis, and available treatment options

Track D Social Science, Human Rights and Political Science

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138414/1/jia218442.pd

Molecular mechanisms of severe acute respiratory syndrome (SARS)

Severe acute respiratory syndrome (SARS) is a new infectious disease caused by a novel coronavirus that leads to deleterious pulmonary pathological features. Due to its high morbidity and mortality and widespread occurrence, SARS has evolved as an important respiratory disease which may be encountered everywhere in the world. The virus was identified as the causative agent of SARS due to the efforts of a WHO-led laboratory network. The potential mutability of the SARS-CoV genome may lead to new SARS outbreaks and several regions of the viral genomes open reading frames have been identified which may contribute to the severe virulence of the virus. With regard to the pathogenesis of SARS, several mechanisms involving both direct effects on target cells and indirect effects via the immune system may exist. Vaccination would offer the most attractive approach to prevent new epidemics of SARS, but the development of vaccines is difficult due to missing data on the role of immune system-virus interactions and the potential mutability of the virus. Even in a situation of no new infections, SARS remains a major health hazard, as new epidemics may arise. Therefore, further experimental and clinical research is required to control the disease