36 research outputs found

    Modeling the elastic and plastic response of single crystals and polycrystalline aggregates

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    Understanding the elastic-plastic response of polycrystalline materials is an extremely difficult task. A polycrystalline material consists of a large number of crystals having different orientations. On its own, each crystal would deform in a specific manner. However, when it is part of a polycrystalline aggregate, the crystal has to ensure compatibility with the aggregate, which causes the response of the crystal to change. Knowing the response of a crystal enables us to view the change in orientation of the crystal when subjected to external macroscopic forces. This ability is useful in predicting the evolution of texture in a material. In addition, by predicting the response of a crystal that is part of a polycrystalline aggregate, we are able to determine the free energy of each crystal. This is useful in studying phenomena like grain growth and diffusion of atoms across high energy grain boundaries. This dissertation starts out by presenting an overview of the elastic and plastic response of single crystals. An attempt is made to incorporate a hardening law which can describe the hardening of slip systems for all FCC materials. The most commonly used theories for relating the response of single crystals to that of polycrystalline aggregates are the Taylor model and the Sachs model. A new theory is presented which attempts to encompass the Taylor as well as the Sachs Model for polycrystalline materials. All of the above features are incorporated into the software program "Crystals"

    THE EFFECT OF MASS TRANSFER ON SELECTIVITY IN THE PHOTOINITIATED LIQUID PHASE CHLORINATION OF NORMAL-DODECANE.

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    Treatment of Overlap Syndromes in Autoimmune Liver Disease: A Systematic Review and Meta-Analysis

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    The treatment of overlap syndromes is guided by small observational studies whose data have never been synthesized in a rigorous, quantitative manner. We conducted a systematic review and meta-analysis to evaluate the efficacy of available treatments for these rare and morbid conditions. We searched the literature for studies comparing ≥2 therapies for autoimmune hepatitis (AIH)-primary biliary cholangitis (PBC), AIH-primary sclerosing cholangitis (PSC), PBC-PSC, AIH-PBC-PSC, autoimmune cholangitis (AIC), or autoimmune sclerosing cholangitis (ASC) with respect to various clinical outcomes, including biochemical improvement and transplant-free survival. A total of 28 studies met the inclusion criteria for AIH-PBC, AIH-PSC, AIC, and ASC. AIH-PBC patients tended to experience more biochemical improvement with ursodeoxycholic acid (UDCA) + [corticosteroids and/or antimetabolites], i.e., “combination therapy”, than with corticosteroids ± azathioprine (RR = 4.00, 95% CI 0.93–17.18). AIH-PBC patients had higher transplant-free survival with combination therapy than with UDCA, but only when studies with follow-up periods ≤90 months were excluded (RR = 6.50, 95% CI 1.47–28.83). Combination therapy may therefore be superior to both UDCA and corticosteroids ± azathioprine for the treatment of AIH-PBC, but additional studies are needed to show this definitively and to elucidate optimal treatments for other overlap syndromes

    Cholestatic Liver Disease and Pregnancy: A Systematic Review and Meta-Analysis

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    Primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) are two types of chronic cholestatic liver disease (CCLD). Little is known regarding the relationship between these conditions and pregnancy. We performed a systematic review and meta-analysis regarding the maternal and fetal outcomes amongst patients with a known diagnosis of PBC and PSC undergoing pregnancy. Our analysis shows that patients with PBC and PSC who undergo pregnancy are at an increased risk of pre-term delivery, as well as the development of new or worsening pruritus during pregnancy. Additionally, patients with PBC are at higher risk of undergoing a biochemical disease flare during the postpartum period compared to during pregnancy. However, there were no documented cases of maternal mortality or development of decompensated cirrhosis during pregnancy or the postpartum period
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