Numerical Simulation of Thermoelectric Transport in Bulk and Nanostructured SiSn Alloys

The current high demand for sustainable and renewable energy sources to solve world energy crisis has enormously increased interest in looking at alternative sources of energy. All the machines used in manufacturing process, electricity generation, residential applications, transportation etc., rejects energy in the form of heat into environment. Thermoelectric materials can convert thermal-to-electrical and electrical-to-thermal energy and can be utilized in waste-heat harvesting, more efficient cooling to reduce energy usage and CO2 emissions. Significant research efforts have been devoted over the past decade to thermoelectric materials, with particular emphasis being placed on combining materials selection with nanostructuring. The overarching goal was to reduce thermal conductivity through selective phonon scattering and thus boost the thermoelectric figure-of-merit (ZT). SiGe alloys, as well as superlattices and nanocomposites made from them, showed significant improvements upon nanostructuring and ZT exceeding one at high temperatures. Other group IV alloys were not studied in the context of thermoelectrics. However, SiSn alloys are widely studied for their optoelectronic properties because they were predicted to become direct-gap materials when Sn composition increased beyond about 50%. To address this gap, we study the thermoelectric properties of SiSn alloys. Furthermore, we develop an iterative full-band solver for the electron Boltzmann transport equation and use it to compute the electron and hole mobility and Seebeck coeffcient in SiSn alloys. The electronic structure of SiSn alloys was computed in the virtual crystal approximation from non-local empirical pseudopotentials, while the application of strain allowed us to extract the electron-phonon coupling deformation potentials for each alloy composition. We benchmark our code against available mobility data for Si and SiGe alloys and find that it accurately reproduces the measured values. Full phonon dispersion was computed from the adiabatic bond charge model, which was shown to accurately reproduce measured dispersion, and used in our phonon BTE solver to compute lattice thermal conductivities. Scattering rates include anharmonic phonon-phonon, impurity, isotope, alloy, and boundary mechanisms. The lowest thermal conductivity was obtained in SiSn alloys, which have been experimentally demonstrated with up to 18% Sn composition. This carries through when combined with calculations of electronic power factor, where mobilities and Seebeck coeffcients of SiSn alloys are comparable to those of SiGe. Furthermore, ZT is optimized through doping for every composition. The ZT improves dramatically at higher temperatures, reaching ZT of 1.9, 2.36 is obtained for Sn composition of 10% and 50% in a n-doped bulk SiSn alloys at a temperature of 1480 K. However, such high Sn composition of 50% is unlikely to be synthesized due to low solid solubility of Sn in Si. Lastly, we study the impact of nanostructuring in thin films on the ZT. We also establish the limits on how much the ZT can be improved through nanostructuring by studying thin films of SiSn alloys across temperature from room temperature up to 1500 K. We conclude that in bulk SiSn alloys, even at modest Sn concentration of 10%, ZT can reach 1.9, while in 20 nm thin films of n-type SiSn alloys, it can reach the long-sought target of ZT\u3e3 and ZT of 2.16 is obtained in p-type nanostructured SiSn alloys

Effect of method of freezing, processing and packaging variables on microbiological and other quality characteristics of beef and poultry

Various aspects of freezing preservation and packaging methods were studied for feasibility of use for beef and poultry in practical applications;Investigations on the effects of combining fresh and frozen beef in different proportions showed that a 50:50 ratio of fresh to frozen beef produced higher bacterial numbers than observed when other proportions were combined and held in frozen storage. No health hazard was evident from any of the different combinations of fresh or frozen beef or from liquid nitrogen or liquid CO(,2) freezing and frozen storage. Changes in bacterial flora as a result of freezing and frozen storage were studied by classifying the isolates into phenotypic groups with the help of replica plating and computerized cluster analysis. Reference cultures were used to identify the clusters. The Moraxella-Acinetobacter group increased considerably in percentage of total isolates after freezing, with a decline during frozen storage. A concomitant increase in the Pseudomonas group of organisms occurred during frozen storage. Certain characteristics of the bacterial flora that were related to spoilage of beef such as lipolysis of beef fat and proteolysis became more pronounced after frozen storage. These changes generally followed the pattern of alterations in the proportions of Pseudomonas to other groups;Studies on the effects of packaging materials and methods on shelf life of chicken showed that a high barrier (vacuum package) material provided greatest restriction of bacterial multiplication, a low barrier (vacuum package) was next effective and a stretch wrap in a tray (air pack) was least effective. Chlorine at a level of 20 ppm as a dip did not provide increased storage life compared with vacuum packaged chicken maintained in the dry state during storage at 5(DEGREES)C. All cut-up poultry spoiled faster than any of the whole birds. Cutting operations increased the incidence of Salmonella and coagulase positive staphylococci on chicken;Investigations on the effects of cryogenic and conventional freezing methods on factors related to quality of turkey meat indicated that all freezing methods caused an increase in Myofibril Fragmentation Index, a measure considered to be associated with tenderness of meat. Conventionally frozen turkey meat had higher fluid losses than meat frozen by liquid nitrogen

IOT devices based improved cryptosystem for secure image sharing

The security and integrity of medical data have become major problems for healthcare services applications due to the considerable growth of the internet of things (IoT) in the healthcare industry. For protecting diagnostic text data in medical pictures, this study offers a hybrid security architecture. The suggested model is created by combining a proposed hybrid encryption method with either 2D-Discrete Wavelet Transform 1 Level (2D-DWT-1L) or 2D-DWT-2L steganography. The Advanced Encryption Standard (AES) and Rivest, Shamir, and Adleman (RSA) algorithms are combined in the proposed hybrid encryption scheme. The Advanced Encryption Standard (AES) and Rivest, Shamir, and Adleman (RSA) algorithms are combined in the proposed hybrid encryption scheme. The suggested methodology encrypts the secret data first, then uses 2D-DWT-1L or 2D-DWT-2L to conceal the result in a cover picture. To hide varying text sizes, cover pictures in both colour and grayscale are utilized. The results of the experiments demonstrate that the suggested picture steganography approach achieves a reasonable balance of resilience and invisibility, even for messages of various sizes

Identification of amino acid residues, essential for maintaining the tetrameric structure of sheep liver cytosolic serine hydroxymethyltransferase, by targeted mutagenesis

Serine hydroxymethyltransferase (SHMT), a pyridoxal 5′-phosphate (PLP)-dependent enzyme, catalyses the transfer of the hydroxymethyl group from serine to tetrahydrofolate to yield glycine and N5,N10-methylenetetrahydrofolate. An analysis of the known SHMT sequences indicated that several amino acid residues were conserved. In this paper, we report the identification of the amino acid residues essential for maintaining the oligomeric structure of sheep liver cytosolic recombinant SHMT (scSHMT) through intra- and inter-subunit interactions and by stabilizing the binding of PLP at the active site. The mutation of Lys-71, Arg-80 and Asp-89, the residues involved in intra-subunit ionic interactions, disturbed the oligomeric structure and caused a loss of catalytic activity. Mutation of Trp-110 to Phe was without effect, while its mutation to Ala resulted in the enzyme being present in the insoluble fraction. These results suggested that Trp-110 located in a cluster of hydrophobic residues was essential for proper folding of the enzyme. Arg-98 and His-304, residues involved in the inter-subunit interactions, were essential for maintaining the tetrameric structure. Mutation of Tyr-72, Asp-227 and His-356 at the active site which interact with PLP resulted in the loss of PLP, and hence loss of tetrameric structure. Mutation of Cys-203, located away from the active site, weakened PLP binding indirectly. The results demonstrate that in addition to residues involved in inter-subunit interactions, those involved in PLP binding and intra-subunit interactions also affect the oligomeric structure of scSHMT

Impact of real-time ultrasound guidance on complications of percutaneous dilatational tracheostomy: a propensity score analysis

Abstract Introduction Recent studies have demonstrated the feasibility of real-time ultrasound guidance during percutaneous dilatational tracheostomy, including in patients with risk factors such as coagulopathy, cervical spine immobilization and morbid obesity. Use of real-time ultrasound guidance has been shown to improve the technical accuracy of percutaneous dilatational tracheostomy; however, it is unclear if there is an associated reduction in complications. Our objective was to determine whether the peri-procedural use of real-time ultrasound guidance is associated with a reduction in complications of percutaneous dilatational tracheostomy using a propensity score analysis. Methods This study reviewed all percutaneous dilatational tracheostomies performed in an 8-year period in a neurocritical care unit. Percutaneous dilatational tracheostomies were typically performed by trainees under guidance of the attending intensivist. Bronchoscopic guidance was used for all procedures with addition of real-time ultrasound guidance at the discretion of the attending physician. Real-time ultrasound guidance was used to guide endotracheal tube withdrawal, guide tracheal puncture, identify guidewire entry level and confirm bilateral lung sliding. The primary outcome was a composite of previously defined complications including (among others) bleeding, infection, loss of airway, inability to complete procedure, need for revision, granuloma and early dislodgement. Propensity score analysis was used to ensure that the relationship of not using real-time ultrasound guidance with the probability of an adverse outcome was examined within groups of patients having similar covariate profiles. Covariates included were age, gender, body mass index, diagnosis, Acute Physiology and Chronic Health Evaluation II score, timing of tracheostomy, positive end-expiratory pressure and presence of risk factors including coagulopathy, cervical spine immobilization and prior tracheostomy. Results A total of 200 patients underwent percutaneous dilatational tracheostomy during the specified period, and 107 received real-time ultrasound guidance. Risk factors for percutaneous dilatational tracheostomy were present in 63 (32%). There were nine complications in the group without real-time ultrasound guidance: bleeding (n = 4), need for revision related to inability to ventilate or dislodgement (n = 3) and symptomatic granuloma (n = 2). There was one complication in the real-time ultrasound guidance group (early dislodgement). The odds of having an adverse outcome for patients receiving real-time ultrasound guidance were significantly lower (odds ratio = 0.08; 95% confidence interval, 0.009 to 0.811; P = 0.032) than for those receiving a standard technique while holding the propensity score quartile fixed. Conclusions The use of real-time ultrasound guidance during percutaneous dilatational tracheostomy was associated with a significant reduction in procedure-related complications.http://deepblue.lib.umich.edu/bitstream/2027.42/111730/1/13054_2015_Article_924.pd

Increased baseline ECG R-R dispersion predicts improvement in systolic function after atrial fibrillation ablation.

BackgroundAtrial fibrillation (AF) is associated with left ventricular (LV) systolic dysfunction which may improve after AF ablation. We hypothesised that increased ventricular irregularity, as measured by R-R dispersion on the baseline ECG, would predict improvement in the left ventricular ejection fraction (LVEF) after AF ablation.MethodsPatients with LVEF <50% at two US centres (2007-2016), having both a preablation and postablation echocardiogram or cardiac MRI, were included. LVEF improvement was defined as absolute increase in LVEF by >7.5%. Multivariable logistic regression (restricted to echocardiographic/ECG variables) was performed to evaluate predictors of LVEF improvement.ResultsFifty-two patients were included in this study. LVEF improved in 30 patients (58%) and was unchanged/worsened in 22 patients (42%). Those with versus without LVEF improvement had an increased baseline R-R dispersion (645±155 ms vs 537±154 ms, p=0.02, respectively). The average baseline heart rate in all patients was 93 beats per minute. After multivariable logistic regression, increased R-R dispersion (OR 1.59, 95% CI 1.00 to 2.55, p=0.03) predicted LVEF improvement.ConclusionsIncreased R-R dispersion on ECG was independently associated with improved systolic function after AF ablation. This broadens the existing knowledge of arrhythmia-induced cardiomyopathy, demonstrating that irregular electrical activation (as measured by increased R-R dispersion on ECG) is associated with a cardiomyopathy capable of improving after AF ablation

COMPARATIVE STUDY OF GELATINASE ACTIVITY AND PELLICLE FORMATION AMONG EXTENDED-SPECTRUM BETA-LACTAMASE AND NON-EXTENDED-SPECTRUM BETA-LACTAMASE PRODUCING ACINETOBACTER BAUMANNII FROM DIABETIC FOOT ULCER INFECTIONS

Objective: The aim of the study was to assess and compare the gelatinase activity and pellicle formation in extended-spectrum beta-lactamase (ESBL) and non-ESBL producing Acinetobacter baumannii isolates from diabetic foot ulcer infection (DFI).Methods: A total of 42 isolates of A. baumannii recovered from patients of DFI from September 2016 to February 2018. Isolates were identified by the standard microbiological method and confirmed by the BD Phoenix 100 system. The antimicrobial susceptibility test was performed by the Kirby–Bauer disk diffusion method and ESBL was detected by double disk diffusion synergy test method. Gelatinase production was determined by the Luria Bertani agar supplemented with 30 g/L gelatin, and pellicle formation was determined by the Mueller-Hinton broth which is incubated at two different temperatures.Results: A total of 42 A. baumannii isolates were multidrug resistant. Among 21 isolates, each was ESBL and non-ESBL producers. Pellicle formation at 25°C in ESBL and non-ESBL producer isolates was 47.61% (10/21) and 28.57% (06/21). Pellicle formation at 37°C in ESBL and non-ESBL producer isolates was 57.14% (12/21) and 42.85% (09/21), respectively. Gelatinase production was present in 38.09% ESBL and 28.57% in non-ESBL producers. ESBL strains were more virulent compared to non-ESBL producers among patients of DFIs.Conclusion: This study showed that pellicle formation at 37°C was highly virulent due to ESBL producers. Gelatinase production was elevated in ESBL compared to non-ESBL producer isolates. This attribute of the isolates could render ESBL positive more pathogenic. Colistin and polymyxin B are the only choices of treatment for multidrug-resistant Acinetobacter baumannii infections

A Cost-Consequence Analysis of NUPCAC: A perspective on the direct financial impact to the PCT

Executive Summary The NHS faces a major challenge to transform itself into a patient-centred organisation, while at the same time saving over £20 billion between 2011 and 2014 (Chapman & Kern 2010). Since 2000 the productivity in the hospitals has fallen down by 1.4% (Hitchcock 2011). Unnecessary hospital admissions (Campbell 2010) increases resource utilisation which needs curbing to save money. Nottingham City PCT like other healthcare organisations is facing a similar situation - budget pressures and the need to reduce hospital admissions. The PCT’s aim was to decrease the number of patients being admitted to assessment wards in Nottingham University Hospitals (NUH), the waiting times in the Emergency department(ED) and finally to cut costs. These aims were to be achieved through the introduction of Nottingham Urgent Primary Care Assessment Centre (NUPCAC). NUPCAC’s primary aim was to achieve cost efficiencies by avoiding unnecessary admission to assessment wards and the Emergency Department, since these both were proving expensive to the PCT. The objective of this dissertation is to identify the “Direct financial impact of NUPCAC for Nottingham City PCT”. This study uses retrospective data, analysing the various costs from 2007 to 2010, incurred by the PCT through NUPCAC. A thorough literature review has been made on the relevant topics, concentrating on New Public Management and Payment by Results and how these impact on the study. Cost-consequence analysis has been described in detail along with how it varies from other types of economic analysis. The costs of NUPCAC are compared with the assumed hospital/admission costs that would have otherwise been incurred by the PCT in the absence of NUPCAC. Using a cost-consequence analysis as in Kaufman and Watkins paper (1996) all the costs and savings are presented in a coarse balance sheet format identifying the various costs and savings. The study is based on previous studies using cost-consequence analysis but the major modification here is, for NUPCAC data to be compared to understand the financial impact it has been compared against assumed hospital costs. The main consequences of NUPCAC - costs and savings are presented in a balance sheet format and in the subsequent sections the non-financial consequences are also explained but only in brief. The main findings of this study demonstrate that the PCT has achieved positive financial impact with the introduction of NUPCAC service - creating a saving for the PCT, demonstrating the fact that NUPCAC is less expensive compared to hospital admissions. The trend for the future appears to be positive with the introduction of new services in NUPCAC and increased number of referrals from NUH. There have been many limitations on this study due to the retrospective nature of study and lack of accurate data. The findings could be strengthened by conducting studies to understand the perspective of NUPCAC services from patient and clinician perspective. The findings of this project will also help the PCT in setting a benchmark for future evaluations of NUPCAC