Evaluation of Single-Cell Cavities Made of Forged Ingot Niobium at Jefferson Lab

Currently, fine grain niobium (Nb) (grain size ∼ 50 µm) and large grain Nb (grain size of a few cm) are being used for the fabrication of superconducting radio frequency (SRF) cavities. Medium grain forged ingot with grain size of a few hundred µm may be beneficial for cost-effectiveness as well as providing better performance for future SRF-based accelerators. Forged ingot Nb with medium grain size is a novel production method to obtain Nb discs used for the fabrication of superconducting radio frequency cavities. We have fabricated two 1.5 GHz single cell cavities made from forged Nb ingot with a residual resistivity ratio of ∼ 100. The cavities were chemically and mechanically polished and heat-treated in the temperature range of 650-1000 C before the rf test. One of the cavities reached an accelerating gradient of ∼34 MV/m with a quality factor Q \u3e 1e10, while the second cavity was limited at 14 MV/m, likely due to a weld defect at the equator

Magnetic Flux Expulsion in Superconducting Radio-Frequency Niobium Cavities Made From Cold Worked Niobium

Trapped residual magnetic field during the cooldown of superconducting radio frequency (SRF) cavities is one of the primary source of RF residual losses leading to lower quality factor. Historically, SRF cavities have been fabricated from high purity fine grain niobium with grain size ~50 - 100 μm as well as large grain with grain size of the order of few centimeters. Non-uniform recrystallization of fine-grain Nb cavities after the post fabrication heat treatment leads to higher flux trapping during cooldown, hence the lower quality factor. We fabricated two 1.3 GHz single cell cavities from cold-worked niobium from different vendors and processed along with cavities made from SRF grade Nb. The flux expulsion and flux trapping sensitivity were measured after successive heat treatments in the range 800 – 1000°C. The flux expulsion from cold-worked fine-grain Nb cavities improves after 800°C/3 hours heat treatments and it becomes similar to that of standard fine-grain Nb cavities when the heat treatment temperature is higher than 900°C

Preliminary Results of Magnetic and Temperature Map System for 3 GHz Superconducting Radio Frequency Cavities

Superconducting radio frequency (SRF) cavities are fundamental building blocks of modern particle accelerators. When we cool these cavities at cryogenic temperature ~2 – 4 K, we can get optimum performance by minimizing RF losses on the inner cavity surface. However, temperature-independent residual losses in SRF cavities cannot be prevented entirely. One of the leading sources of residual losses in SRF cavities is trapped magnetic flux. The flux trapping mechanism depends on different surface preparations and cool-down conditions. We have designed, developed, and commissioned a combined magnetic (B) and temperature (T) mapping system using anisotropic magneto-resistance (AMR) sensors and carbon resistors to study the flux trap mechanism in 3 GHz single-cell niobium cavities. In this contribution, we present the preliminary results of the newly commissioned B & T mapping system

Metabolic syndrome and biochemical changes among non-alcoholic fatty liver disease patients attending a tertiary care hospital of Nepal

Abstract Background Non-alcoholic fatty liver disease (NAFLD) is mutually and bidirectionally linked with metabolic syndrome (MetS) of which it is both the cause and the consequences. Worldwide, 6.3 to 33% of the general populations are estimated to suffer from the disease with even higher prevalence in the group sharing metabolic co-morbidities. Hence, this study aims to recognize various risk factors including metabolic components and blood parameters to predict the possible incidence of the disease. Methods Total of 429 (219 NAFLD and 210 control) subjects were conveniently selected for study during the period of 9 months. Diagnosis of non-alcoholic fatty liver disease was done by liver imaging and based on liver enzymes. Assessment of metabolic syndrome was done by International Diabetic Federation (IDF) and National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria. All biochemical and hematological parameters and liver enzymes were estimated by using standard guideline. Mean comparison of quantitative data in different groups were performed using analysis of variance (one-way ANOVA). Risk estimation of NAFLD associated with each character was verified by Chi-square test. Results There was significant high levels of body mass index (BMI), waist circumference (WC) and lipid profiles in NAFLD patients in comparison to control population (p < 0.001). Further, according to the NCEP ATP III criteria, 13.6% of NAFLD were present with MetS where risk estimate was significant (OR = 2.15). Whereas, other criteria (IDF) for MetS showed higher frequency (30.1%) with higher risk (OR = 29.75) for the presence of MetS in NAFLD patients. The change in triglycerides (TG) and HDL-C (high density lipoprotein cholesterol) was also statistically significant in different grades of NAFLD. High risk for NAFLD was associated with existing co-morbid conditions like cardiovascular risk patients (3.18 times) followed by obese patients (1.72 times) and Diabetes Mellitus patients (1.68 times) at a significant level. Conclusion The result of this study suggests that there is an increased prevalence of all the components of MetS and significant changes in biochemical markers in cases of NAFLD. Timely diagnosis would help in delaying its complications and co-morbidities

Shigellosis Caused by CTX-M Type ESBL Producing Shigella flexneri in Two Siblings of Rural Nepal: First Case Report from the Country

Shigellosis is an acute infectious disease characterized as severe bloody diarrhea (dysentery) and is accountable for a significant burden of morbidity and mortality especially in children under the age of 5 years. Antimicrobial therapy is required in the cases of severe dysentery associated with Shigella. However, emergence of multidrug resistant (MDR) strains of Shigella spp. over the last two decades has restricted the use of common therapeutic antimicrobials. In MDR strains, the third-generation cephalosporins have been used for the treatment, but, unfortunately, emerging reports of enzyme mediated β-lactam resistance among Shigella isolates from various parts of the world have greatly compromised the therapy of pediatric dysentery. In Nepal, drug resistant strains of Shigella spp. have been reported, but MDR and extended spectrum β-lactamase (ESBL) producing strains were previously unknown. Here, we report two Shigella flexneri isolates harboring ESBL genotype-CTX-M associated with acute dysentery in two siblings which were presented and treated in a tertiary care teaching hospital of Kathmandu, Nepal