Band alignment and scattering considerations for enhancing the thermoelectric power factor of complex materials: The case of Co-based half-Heuslers

Half-Heuslers, an emerging thermoelectric material group, has complex bandstructures with multiple bands that can be aligned through band engineering approaches, giving us an opportunity to improve their power factor. In this work, going beyond the constant relaxation time approximation, we perform an investigation of the benefits of band alignment in improving the thermoelectric power factor under different density of states dependent scattering scenarios. As a test case we consider the Co-based p-type half-Heuslers TiCoSb, NbCoSn and ZrCoSb. First, using simplified effective mass models combined with Boltzmann transport, we investigate the conditions of band alignment that are beneficial to the thermoelectric power factor under three different carrier scattering scenarios: i) the usual constant relaxation time approximation, ii) intra-band scattering restricted to the current valley with the scattering rates proportional to the density of states as dictated by Fermi's Golden Rule, and iii) both intra- and inter-band scattering across all available valleys, with the rates determined by the total density of states at the relevant energies. We demonstrate that the band-alignment outcome differs significantly depending on the scattering details. Next, using the density functional theory calculated bandstructures of the half-Heuslers we study their power factor behavior under strain induced band alignment. We show that strain can improve the power factor of half-Heuslers, but the outcome heavily depends on the curvatures of the bands involved, the specifics of the carrier scattering mechanisms, and the initial band separation. Importantly, we also demonstrate that band alignment is not always beneficial to the power factor.Comment: 18 pages, 15 figure

Epidemiological, clinical and laboratory characteristics of 19 serologically confirmed rickettsial disease in Singapore.

AIM: To identify epidemiological, clinical and laboratory features of serologically-proven typhus in the local setting. METHOD & RESULTS: Retrospective study looking at rickettsial serologies done over a six-month period and collection of the epidemological, clinical, laboratory and treatment response data from the case notes of the patients with an ordered rickettsial serology. Twenty of the 35 cases had a positive serology. Of these 20 patients, 18 were already clinically diagnosed as having murine typhus. All except one were males and all were migrant workers. Majority of the patients were construction workers staying in containers where rats abound. The most consistent clinical features were high fever (100%) for a median period of seven days, headache (94%) and cough (47%). The white cell count was usually normal (74%) but thrombocytopenia was common (68%). Transaminitis was also common (90%) with the AST component higher than the ALT in half of the cases. Response to doxycycline therapy was rapid and most (88%) were afebrile by 72 hours. CONCLUSION: Typhus (notably murine type) can be confidently diagnosed from consistent clinical features supported by epidemiological and laboratory clues. Early recognition with the prompt treatment response will result in shorter hospital stay with decreased cost. Serological testing may only prove useful in difficult situations when the clinical diagnosis is less clear

Transference numbers of symmetrical aqueous electrolytes

Imperial Users onl

Glycollate metabolism in detached wheat leaves

Imperial Users onl

Islam and We

Panel: Islam and W

Urea-Hydroxyapatite Nanohybrids for Slow Release of Nitrogen.

While slow release of chemicals has been widely applied for drug delivery, little work has been done on using this general nanotechnology-based principle for delivering nutrients to crops. In developing countries, the cost of fertilizers can be significant and is often the limiting factor for food supply. Thus, it is important to develop technologies that minimize the cost of fertilizers through efficient and targeted delivery. Urea is a rich source of nitrogen and therefore a commonly used fertilizer. We focus our work on the synthesis of environmentally benign nanoparticles carrying urea as the crop nutrient that can be released in a programmed manner for use as a nanofertilizer. In this study, the high solubility of urea molecules has been reduced by incorporating it into a matrix of hydroxyapatite nanoparticles. Hydroxyapatite nanoparticles have been selected due to their excellent biocompatibility while acting as a rich phosphorus source. In addition, the high surface area offered by nanoparticles allows binding of a large amount of urea molecules. The method reported here is simple and scalable, allowing the synthesis of a urea-modified hydroxyapatite nanohybrid as fertilizer having a ratio of urea to hydroxyapatite of 6:1 by weight. Specifically, a nanohybrid suspension was synthesized by $\textit{in situ}$ coating of hydroxyapatite with urea at the nanoscale. In addition to the stabilization imparted due to the high surface area to volume ratio of the nanoparticles, supplementary stabilization leading to high loading of urea was provided by flash drying the suspension to obtain a solid nanohybrid. This nanohybrid with a nitrogen weight of 40% provides a platform for its slow release. Its potential application in agriculture to maintain yield and reduce the amount of urea used is demonstrated.Authors thank Hayleys Agro Ltd., Sri Lanka for initiating this research programme at SLINTEC and Nagarjuna Fertilizer and Chemical Ltd (NFCL), India for providing further support. Authors acknowledge Mr Sunanda Gunesekara of SLINTEC for assistance with scaling up the production process to enable the field trials. ARK acknowledges the financial support received from ICTPELETTRA Users Program, Trieste, Italy to conduct photoemission experiments at Materials Science beam line (MSB) and ELETTRA SRS on HA and urea coated HA samples. ARK further acknowledges Dr. R.G. Acres of MSB beam line for his extensive support to conduct photoemission experiments. We acknowledge the Department of Agriculture and Rice Research and Development Institute of Sri Lanka, in particular Dr Priyantha Weerasinghe, Mr D Sirisena and Dr Amitha Benthota for the assistance in carrying out pot and farmers filed trials. NFCL and Central Salt & Marine Chemicals Research Institute, Gujarat, India for TEM and BET analysis

Improving the B App to Improve Customer Experience and Operational Efficiency: From the Perspectives of User Engagement, Functionality, and Security

The aim of this thesis was to propose actionable changes within B App, a digital banking application offered by the case company. The app has been criticized for its poor user experience, functional unreliability, and security concerns, affecting customer satisfaction and operational efficiency. This thesis aimed at providing a proposal for enhancing B App, in line with the strategic goal of the case company for delivering a seamless digital banking experience. This thesis utilized the Applied action research approach and mainly qualitative data collection methods. It started with a CSA focused on identifying the main weaknesses of the app. Data collection comprised interviews with internal stakeholders and thematic analysis of 400 user reviews. These findings were supported by the academic literature review and industry best practices to establish a conceptual framework for building the proposal. Expert feedback sessions were conducted to validate the initial proposal and ensure that it is feasible and meets the needs of the organization. The combination of theoretical and practical insights was combined in building the proposal. The conceptual framework drew on theories related to UX, reliability engineering principles, and multi-layered security strategies. Translated into a detailed proposal, this included a recommendation or plan of simplification of navigation, optimization of back-end infrastructure, and enhancement in biometric authentication systems. The thesis also provided an actionable plan in terms of phased implementation as the rollout for the improvement plan. The contribution of stakeholders helped in validating the final proposal. Once implemented, this proposal is expected to improve customer satisfaction and the company's reputation for secure and reliable digital banking services. The conclusions form the thesis underline the importance of aligning user-centric design with operational excellence for achieving sustained business impact

日本の伝統演劇がEdiriweera Sarachchandraの脚本に与えた影響

アジア新時代の南アジアにおける日本像 : インド・SAARC 諸国における日本研究の現状と必要性, ジャワハルラル・ネルー大学, 2009年11月3日-4

Impact of the scattering physics on the power factor of complex thermoelectric materials

We assess the impact of the scattering physics assumptions on the thermoelectric properties of five Co-based p-type half-Heusler alloys by considering full energy-dependent scattering times vs the commonly employed constant scattering time. For this, we employ density functional theory band structures and a full numerical scheme that uses Fermi's golden rule to extract the momentum relaxation times of each state at every energy, momentum, and band. We consider electron-phonon scattering (acoustic and optical), as well as ionized impurity scattering, and evaluate the qualitative and quantitative differences in the power factors of the materials compared to the case where the constant scattering time is employed. We show that the thermoelectric power factors extracted from the two different methods differ in terms of (i) their ranking between materials, (ii) the carrier density where the peak power factor appears, and (iii) their trends with temperature. We further show that the constant relaxation time approximation smoothens out the richness in the band structure features, thus limiting the possibilities of exploring this richness for material design and optimization. These details are more properly captured under full energy/momentum-dependent scattering time considerations. Finally, by mapping the conductivities extracted within the two schemes, we provide appropriate density-dependent constant relaxation times that could be employed as a fast first-order approximation for extracting charge transport properties in the half-Heuslers we consider

Analysis of Genes Involved in Anaerobic Growth in Porphyromonas Gingivalis and Shewanella Oneidensis MR-1

Porphyromonas gingivalis is an oral Gram-negative anaerobic bacterium implicated in periodontal disease, a polymicrobial inflammatory disease that is correlated with cardiovascular disease, diabetes and preterm birth. Therefore understanding the physiology and metabolism of P.gingivalis through genetic manipulation is important in identifying mechanisms to eliminate this pathogen. Although numerous genetic tools have been developed for the manipulation of other bacterial species, they either do not function in P.gingivalis or they have limitations. We modified a Mariner transposon pHimarEM1 system that was developed for Flavobacterium johnsoniae for mutagenesis of P. gingivalisWe introduced the P. gingivalis fimA promoter upstream of the transposase gene to improve the efficiency of the transposition in P.gingivalis. Transposon mutants of P.gingivalis were screened for growth or pigmentation defects and analyzed. Using this technique, strains with mutations in genes encoding cation efflux system Proteins, Na+-translocating NADH-quinone reductase were identified thus demonstrating the effectiveness of this new transposon. Therefore pHimarEM1-PfimA can be used to generate new mutants in P. gingivalis that lead to explore the metabolic pathways of P. gingivalis Shewanella oneidensis MR-1 is a facultative anaerobe and metal reducing bacterium that uses a large number of terminal electron acceptors for respiration. These include thiosulfate, polysulfide and sulfite. The dissimilatory sulfite reductase, Sir A is a c type cytochrome predicted to be a copper protein. It catalyses the six electron reduction of sulfite to sulfide and unlike other sulfite reductases, it appears to lack siroheme. Cu is essential for many respiratory enzymes such as cytochrome c oxidases and anaerobic nitrous oxide reductases. NosA is predicted to be a copper specific porin in the outer membrane that allows copper diffusion into the cell. In the second chapter of this thesis we hypothesized that NosA is expressed under aerobic and anaerobic conditions and is involved in biogenesis of the sulfite reductase (SirA). We also predict that additional porins may be needed for Cu entry into the cell