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

Transference numbers of symmetrical aqueous electrolytes

Imperial Users onl

Glycollate metabolism in detached wheat leaves

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Islam and We

Panel: Islam and W

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

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

Trainee’s voices: An exploration of the importance of child development, the theories of childhood and play-based learning for any adult who works with young children from birth to preschool years

In January 2001, the Singapore Ministry of Education (MOE) and Ministry of Community Development, Youth and Sports (MCYS) jointly set up Pre-School Qualification Accreditation Committee (PQAS) to oversee the standards and quality of pre school teacher training for both kindergarten and Childcare sectors. The MOE and the MCYS introduced an integrated Pre-School Education (PSE) framework for teacher training and accreditation applicable to р re-school personnel. The training route for pre-school teachers came into effect in January 2001. Teacher training and the qualifications offer high leverage opportunities for enhancing standards of training and expanding career opportunities for pre-school professionals in Singapore. The various levels of training are planned to cater to the different needs of the teachers and prepare them for leadership in the sector. This will ensure that pre-school professionals are well equipped to provide our young children with an enriched learning environment, to nurture their social skills and values, and prepare them for lifelong learning (wwwl.moe.edu.sg/preschooleducation).The majority of teacher trainees involved in this research have been working as caregivers in most Child Care Centres in Singapore without relevant knowledge of the child. The study is underpinned by the contemporary argument that any adult who works with children needs to know about Child Development, Theories of Childhood and Play-based Learning Environment, which actively challenge the traditional stereotypical notions that experiences alone would be sufficient. Understanding the growing child would no doubt help to focus on appropriate tasks for the child. Central to the focus of the study is to gain an understanding of the existing knowledge of the teacher trainees (both who are working with children and otherwise) before and after the study sessions and how such an increase of knowledge could empower and enfranchise the teachers to make informed decisions in the child’s life. At the completion of the course they were able to comprehend the most important factors of the growing child that they were considerably unaware of and better manage behavioural situations with the child. The teachers' final records of Observation and Evaluation, Professional Journals of the children combined with a final powerful public presentation of the Child Study Making Learning Visible no doubt heighten the educational process as a learning discipline, a vital link that provides a powerful medium to interact with the growing child

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

Recent Advances in Green Approaches for Synthesis of Oxindole Derivatives

Oxindole derivatives are nitrogen-containing, five-membered heterocyclic molecules found in both natural and synthetic substances with diverse biological functions. Owing to their pharmaceutical and therapeutic characteristics, oxindoles have received remarkable attention, and various oxindole-containing substances can be synthesized using many different approaches. With the discovery of the importance of oxindole derivatives in medicinal chemistry, mainly in drug synthesis, the demand for finding sustainable protocols has increased, as most classical methods have their limitations and flaws. Hence, it is crucial to establish efficient and sustainable techniques that are safe, cost-effective, have low energy consumption, and cause minimal environmental impact. Nowadays, the use of green solvents in organic synthesis has received much attention because they prevent the formation of waste, are environmentally friendly, and have easy work-up procedures. Green solvents such as water, deep eutectic solvents, ionic liquids, and polyethylene glycol can substitute hazardous solvents. Microwave irradiation, visible-light irradiation, electrochemical methods, and multi-component synthesis are all described under green approaches. Most of these approaches allow the reaction to proceed rapidly while releasing minimal waste into the environment. Recent discoveries in green chemistry applications can be considered a turning point in organic synthesis. This review focuses on promising green approaches, used for the synthesis of oxindole derivatives, carried out in recent years with typical examples in two sections: green solvents and green techniques. Keywords- Oxindole derivatives, Green solvents, Green techniques, Sustainable chemistry, Solvent-free

Determinants of Non Performing Loans: Evidence from Sri Lanka

 In the recent past, the global financial crisis and the subsequent recession in many developed countries have increased households’ and firms’ defaults, causing significant losses to the banks. Case of Sri Lanka is no difference. The changes in the economic conditions are believed to have a critical role to play in determining the level of nonperforming loans. Regulators all over the world have started to pay more attention to the credit quality of the Banks and strengthened the regulatory frameworks. This paper attempts to study the macroeconomic determinants of banks’ loan quality in Sri Lanka by analyzing secondary data over the period 1998–2014. The methodology to be adopted for the study was arrived at upon careful review of the literature and following the empirical studies conducted on the determinants of the nonperforming loans. The finding of the analysis is that, out of the six determinants, GDP growth rate and the Export Growth are significant in determining the level of the NPLs in the Sri Lankan banking sector. The relationship of the GDP with the NPL is found to be positive which is not consistent with the majority of the empirical findingsKeywords: Nonperforming Loans, Macroeconomic Determinants,