Evaluation of flux expulsion and flux trapping sensitivity of srf cavities fabricated from cold work Nb sheet with successive heat treatment

The main source of RF losses leading to lower quality factor of superconducting radio-frequency cavities is due to the residual magnetic flux trapped during cool-down. The loss due to flux trapping is more pronounced for cavities subjected to impurities doping. The flux trapping and its sensitivity to rf losses are related to several intrinsic and extrinsic phenomena. To elucidate the effect of re-crystallization by high temperature heat treatment on the flux trapping sensitivity, we have fabricated two 1.3 GHz single cell cavities from cold-worked Nb sheets and compared with cavities made from standard fine-grain Nb. Flux expulsion ratio and flux trapping sensitivity were measured after successive high temperature heat treatments. The cavity made from cold worked Nb showed better flux expulsion after 800 C/3h heat treatments and similar behavior when heat treated with additional 900 C/3h and 1000 C/3h. In this contribution, we present the summary of flux expulsion, trapping sensitivity, and RF results.Comment: 21st International Conference on Radio-Frequency Superconductivity (SRF 2023

Single-Molecule Analysis of i-motif Within Self-Assembled DNA Duplexes and Nanocircles

The cytosine (C)-rich sequences that can fold into tetraplex structures known as i-motif are prevalent in genomic DNA. Recent studies of i-motif–forming sequences have shown increasing evidence of their roles in gene regulation. However, most of these studies have been performed in short single-stranded oligonucleotides, far from the intracellular environment. In cells, i-motif–forming sequences are flanked by DNA duplexes and packed in the genome. Therefore, exploring the conformational dynamics and kinetics of i-motif under such topologically constrained environments is highly relevant in predicting their biological roles. Using single-molecule fluorescence analysis of self-assembled DNA duplexes and nanocircles, we show that the topological environments play a key role on i-motif stability and dynamics. While the human telomere sequence (C3TAA)3C3 assumes i-motif structure at pH 5.5 regardless of topological constraint, it undergoes conformational dynamics among unfolded, partially folded and fully folded states at pH 6.5. The lifetimes of i-motif and the partially folded state at pH 6.5 were determined to be 6 ± 2 and 31 ± 11 s, respectively. Consistent with the partially folded state observed in fluorescence analysis, interrogation of current versus time traces obtained from nanopore analysis at pH 6.5 shows long-lived shallow blockades with a mean lifetime of 25 ± 6 s. Such lifetimes are sufficient for the i-motif and partially folded states to interact with proteins to modulate cellular processes

Stillbirths among Pregnant Women Admitted to the Department of Obstetrics and Gynaecology in a Tertiary Care Centre: A Descriptive Cross-sectional Study

Introduction: Stillbirth is often defined as the death of a foetus in the uterus prior to its birth or during the process of birth. Most of the stillbirths are preventable global health problem. The aim of this study was to find out the prevalence of stillbirths among pregnant women admitted to the Department of Obstetrics and Gynaecology in a tertiary care centre. Methods: A descriptive cross-sectional study was conducted in the Department of Obstetrics and Gynaecology in a tertiary care centre among pregnant women admitted between 14 April 2021 to 13 April 2022. Ethical approval was taken from the Institutional Review Committee (Reference number: 43). Convenience sampling method was used. The data were collected from the medical record section using a proforma. Point estimate and 95% Confidence Interval were calculated. Results: Among 5,118 pregnant women, stillbirths were found in 126 (2.46%) (2.04-2.88, 95% Confidence Interval). Conclusions: The prevalence of stillbirth among pregnant women was higher than in the other studies done in similar settings

Quench Detection in a Superconducting Radio Frequency Cavity with Combine Temperature and Magnetic Field Mapping

Local dissipation of RF power in superconducting radio frequency cavities create so called hot spots, primary precursors of cavity quench driven by either thermal or magnetic instability. These hot spots are detected by a temperature mapping system, and a large increase in temperature on the outer surface is detected during cavity quench events. Here, we have used combined magnetic and temperature mapping systems using anisotropic magnetoresistance (AMR) sensors and carbon resisters to locate the hot spots and areas with high trapped flux on a 3.0 GHz single-cell Nb cavity during the RF tests at 2.0 K. The quench location and hot spots were detected near the equator when the residual magnetic field in the Dewar is kept < 1 mG. The hot spots and quench locations moved when the magnetic field is trapped locally, as detected by T-mapping system. No significant dynamics of trapped flux is detected by AMR sensors, however, change in magnetic flux during cavity quench is detected by a flux gate magnetometer, close to the quench location. The result provides the direct evidence of hot spots and quench events due to localized trapped vortices.Comment: 21st International Conference on Radio-Frequency Superconductivity (SRF 2023

Effect of top reinforcing on the fire performance of continuous reinforced concrete beams

This paper examines the behaviour of continuous reinforced concrete beams exposed to fire on three sides, in order to investigate the effect of different lengths of the top reinforcing bars over the supports. The study was performed with 2D finite element analysis using SAFIR. The effect of continuity was investigated with rectangular crosssection beams spanning over two and three bays subjected to the ISO 834 fire. Compared to a single span beam, the continuous beams resisted the fire exposure for a longer period of time. It was found that different lengths of the top reinforcing bars resulted in different failure mechanisms, but did not greatly affect the fire resistance of the beams . The influence of the full process of fire development was analysed using the ISO fire for 30, 60 and 90 minutes followed by a decay phase. Structural failure only occurred if the fully developed phase of the fire continued until very close to the failure time reached with no decay phase

Effects of Row Spacings and Varieties on Grain Yield and Economics of Maize

Maize is the second most important crop of Nepal. The yield of the crop is low due to lack of appropriate plant density for the varieties. The field experiment was carried out to study the effect of different row spacings on different maize varieties at Deupur, Lamahi municipality of the dang district in province No. 5, Nepal during the rainy season from June to September, 2018. Four levels of spacings (boardcasting and three row spacings of 45, 60 and 75 cm) and two maize varieties (Rampur Composite and Arun-2) were evaluated using randomized complete block design with three replications. The highest grain yield was found in Rampur Composite and Arun-2 while they were planted with row spacing of 60 cm with plant to plant spacing of 25 cm. The highest grain yield, cob length, cob circumference, number of rows per cob, thousand grain weight&nbsp; were reported when maize was planted in the&nbsp; row spacing 60×25cm. Among the maize varieties, Rampur Composite produced the highest grain yield, cob length, cob circumference, number of rows per cob as compared to Arun-2. This study suggested that maize production can be maximized by cultivating maize varieties with row spacing of 60 cm with plant to plant spacing of 25 cm

Should disaster management strategies in Bangladesh be just about constructing new shelters?

With a population of over 143 million people and a population density of more than 1,200 persons per km2 Bangladesh is a very densely populated country. The country’s geographic location in the waters of Bay of Bengal, often the source of tropical cyclones and storm surges, makes Bangladesh one of the most natural disasters prone nations in the world. A severe tropical cyclone hits the country, every 3 years on average. As 16 major cyclones have hit the country since 1960 with the loss of nearly 500,000 lives, multi-purpose cyclone shelters – that can provide refuge to susceptible population in the events of natural hazards and to a certain extent with the utility of community functionalities during normal times – have become a vital component of disaster management strategies. Country has already constructed more than 2,500 such shelters across 16 of the most disaster prone coastal districts. This paper uses content analysis of disaster management policies, and programs in order to comprehend and assess the distributions of shelters with a lens of integrated strategic asset management framework. Analysis of secondary data indicates that existing cyclone shelters are not equitably distributed to cater the needs of the highly vulnerable population. In the backdrop of the recommendation of The World Bank [TWB] that the country needs 5,500 new shelters (TWB, 2010), this paper contends that future construction of cyclone shelters must be need as well as evidence-based in order to ensure that highly vulnerable population benefits from cyclone shelters the most

Power Purchase Agreements for Risk and Rent Sharing in Himalayan Hydropower Developments

The Himalayan Rivers have an enormous hydropower potential that is still not exploited fully for the benefit of the region. Bhutan and Nepal together have an economically feasible potential of 60,000 MW of hydroelectric power generation capacity but are too weak financially to bear alone the risks associated with the development of their hydro resources. India is the only potential market for the electricity supplied from these sources. The power purchase agreement framework for the 336 MW Chukha Hydel Project in Bhutan could serve as a model with regards to the transfer of risks, management of risks, and sourcing of finance in exchange for the sharing of the economic rents associated with such projects. India undertook the costs and risks of constructing the hydroelectric dam and power plant in exchange for a reduced purchase price of electricity from the completed facility. This paper contains a financial and economic assessment of the Chukha Hydel Project. While India is in a position to exercise monopsonic power in this electricity market, this analysis shows that it is possible to have an agreement for sharing of the risks and returns between India and the Himalayan countries that is highly beneficial to all the stakeholders.power purchase agreement, Himalayas, hydropower, electricity, Bhutan, India, electricity exports, risk sharing, economic rents

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