First-Principles Theoretical Studies of Bulk, Defect and Interface properties of Oxide Semiconductors

Oxide semiconductors have been shown to exhibit rich physics related to their bulk, defect and interface properties. First-principles calculations have and will continue to play a major role in developing an understanding of the microscopic origins of these phenomena. In this thesis, first-principles studies are presented for several oxide semiconductors, with a view to understand how their microscopic properties ultimately determine device functionality. In Chapter 3, a detailed study of bulk SrZrO3 and Sr(Ti,Zr)O3 alloys is performed. For Sr(Ti,Zr)O3 alloys with 50% Ti concentration, we find that arranging the Ti and Zr atoms into a 1×1 SrZrO3/SrTiO3 superlattice along the [001] direction leads to breaking of the conduction band t2g orbital degeneracy, which could suppress scattering due to electron-phonon interactions. In Chapter 4, we present an investigation into the properties of native defects and hydrogen in SrZrO3. It is found that oxygen and strontium vacancies are the dominant defects in the absence of impurity doping, and will form deep donor and deep acceptor states, respectively. Hydrogen is found to be amphoteric in this material at different lattice sites; additionally, this impurity forms a stable complex with oxygen vacancies. In Chapter 5, the tendency for ABO3 perovskite oxides with 3dn B-cations to exhibit ferroelectricity and multiferroicity is investigated. Using the LaBO3 series as a model, we find that initially, as electrons are added to the B-cation d orbital, the tendency for the system to exhibit a ferroelectric distortion disappears - however, for high spin d5 - d7 and d8 cations a strong ferroelectric instability is recovered, and this effect is explained within the pseudo Jahn-Teller theory for ferroelectricity. This finding provides a new route for the design of strongly coupled magnetoelectric materials. In Chapters 6 and 7 the fundamental properties of the technologically important oxide heterostructure systems ZnO/MgZnO and SrTiO3/LaAlO3 are characterized. For the latter, we identify a previously unreported mechanism for interface induced magnetism based on surface aluminium vacancies, which will aid in interpreting experimental results for this system and other polar/non-polar oxide heterostructures

Direct Awards in Germany – Design And Effects

Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne

Can the Cancer-related Fatigue Case-definition Criteria Be Applied to Chronic Medical Illness? A Comparison between Breast Cancer and Systemic Sclerosis

OBJECTIVE: Fatigue is a crucial determinant of quality of life across rheumatic diseases, but the lack of agreed-upon standards for identifying clinically significant fatigue hinders research and clinical management. Case definition criteria for cancer-related fatigue were proposed for inclusion in the International Classification of Diseases. The objective was to evaluate whether the cancer-related fatigue case definition performed equivalently in women with breast cancer and systemic sclerosis (SSc) and could be used to identify patients with chronic illness-related fatigue. METHODS: The cancer-related fatigue interview (case definition criteria met if ≥ 5 of 9 fatigue-related symptoms present with functional impairment) was completed by 291 women with SSc and 278 women successfully treated for breast cancer. Differential item functioning was assessed with the multiple indicator multiple cause model. RESULTS: Items 3 (concentration) and 10 (short-term memory) were endorsed significantly less often by women with SSc compared with cancer, controlling for responses on other items. Omitting these 2 items from the case definition and requiring 4 out of the 7 remaining symptoms resulted in a similar overall prevalence of cancer-related fatigue in the cancer sample compared with the original criteria (37.4% vs 37.8%, respectively), with 97.5% of patients diagnosed identically with both definitions. Prevalence of chronic illness-related fatigue was 36.1% in SSc using 4 of 7 symptoms. CONCLUSION: The cancer-related fatigue criteria can be used equivalently to identify patients with chronic illness-related fatigue when 2 cognitive fatigue symptoms are omitted. Harmonized definitions and measurement of clinically significant fatigue will advance research and clinical management of fatigue in rheumatic diseases and other conditions

Using Optimal Test Assembly Methods for Shortening Patientâ Reported Outcome Measures: Development and Validation of the Cochin Hand Function Scaleâ 6: A Scleroderma Patientâ Centered Intervention Network Cohort Study

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134498/1/acr22893_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134498/2/acr22893.pd

Factor structure and convergent validity of the Derriford Appearance Scale-24 using standard scoring versus treating not applicable' responses as missing data: A Scleroderma Patient-centered Intervention Network (SPIN) cohort study

© 2018 Article author(s) (or their employer(s) unless otherwise stated in the text of the article). All rights reserved. Objective Valid measures of appearance concern are needed in systemic sclerosis (SSc), a rare, disfiguring autoimmune disease. The Derriford Appearance Scale-24 (DAS-24) assesses appearance-related distress related to visible differences. There is uncertainty regarding its factor structure, possibly due to its scoring method. Design Cross-sectional survey. Setting Participants with SSc were recruited from 27 centres in Canada, the USA and the UK. Participants who self-identified as having visible differences were recruited from community and clinical settings in the UK. Participants Two samples were analysed (n=950 participants with SSc; n=1265 participants with visible differences). Primary and secondary outcome measures The DAS-24 factor structure was evaluated using two scoring methods. Convergent validity was evaluated with measures of social interaction anxiety, depression, fear of negative evaluation, social discomfort and dissatisfaction with appearance. Results When items marked by respondents as not applicable' were scored as 0, per standard DAS-24 scoring, a one-factor model fit poorly; when treated as missing data, the one-factor model fit well. Convergent validity analyses revealed strong correlations that were similar across scoring methods. Conclusions Treating not applicable' responses as missing improved the measurement model, but did not substantively influence practical inferences that can be drawn from DAS-24 scores. Indications of item redundancy and poorly performing items suggest that the DAS-24 could be improved and potentially shortened

Patterns of patient-reported symptoms and association with sociodemographic and systemic sclerosis disease characteristics: a scleroderma Patient-centered Intervention Network (SPIN) Cohort cross-sectional study

Background Systemic sclerosis is a heterogenous disease in which little is known about patterns of patient-reported symptom clusters. We aimed to identify classes of individuals with similar anxiety, depression, fatigue, sleep disturbance, and pain symptoms and to evaluate associated sociodemographic and disease-related characteristics. Methods This multi-centre cross-sectional study used baseline data from Scleroderma Patient-centered Intervention Network Cohort participants enrolled from 2014 to 2020. Eligible participants completed the PROMIS-29 v2.0 measure. Latent profile analysis was used to identify homogeneous classes of participants based on patterns of anxiety, depression, fatigue, sleep disturbance, and pain scores. Sociodemographic and disease-related characteristics were compared across classes. Findings Among 2212 participants, we identified five classes, including four classes with “Low” (565 participants, 26%), “Normal” (651 participants, 29%), “High” (569 participants, 26%), or “Very High” (193 participants, 9%) symptom levels across all symptoms. Participants in a fifth class, “High Fatigue/Sleep/Pain and Low Anxiety/Depression” (234 participants, 11%) had similar levels of fatigue, sleep disturbance, and pain as in the “High” class but low anxiety and depression symptoms. There were significant and substantive trends in sociodemographic characteristics (age, education, race or ethnicity, marital or partner status) and increasing disease severity (diffuse disease, tendon friction rubs, joint contractures, gastrointestinal symptoms) across severity-based classes. Disease severity and sociodemographic characteristics of “High Fatigue/Sleep/Pain and Low Anxiety/Depression” class participants were similar to the “High” severity class. Interpretation Most people with systemic sclerosis can be classified by levels of patient-reported symptoms, which are consistent across symptoms and highly associated with sociodemographic and disease-related variables, except for one group which reports low mental health symptoms despite high levels of other symptoms and substantial disease burden. Studies are needed to better understand resilience in systemic sclerosis and to identify and facilitate implementation of cognitive and behavioural strategies to improve coping and overall quality of life

Evaluation of biases present in the cohort multiple randomised controlled trial design: a simulation study

Background The cohort multiple randomised controlled trial (cmRCT) design provides an opportunity to incorporate the benefits of randomisation within clinical practice; thus reducing costs, integrating electronic healthcare records, and improving external validity. This study aims to address a key concern of the cmRCT design: refusal to treatment is only present in the intervention arm, and this may lead to bias and reduce statistical power. Methods We used simulation studies to assess the effect of this refusal, both random and related to event risk, on bias of the effect estimator and statistical power. A series of simulations were undertaken that represent a cmRCT trial with time-to-event endpoint. Intention-to-treat (ITT), per protocol (PP), and instrumental variable (IV) analysis methods, two stage predictor substitution and two stage residual inclusion, were compared for various refusal scenarios. Results We found the IV methods provide a less biased estimator for the causal effect when refusal is present in the intervention arm, with the two stage residual inclusion method performing best with regards to minimum bias and sufficient power. We demonstrate that sample sizes should be adapted based on expected and actual refusal rates in order to be sufficiently powered for IV analysis. Conclusion We recommend running both an IV and ITT analyses in an individually randomised cmRCT as it is expected that the effect size of interest, or the effect we would observe in clinical practice, would lie somewhere between that estimated with ITT and IV analyses. The optimum (in terms of bias and power) instrumental variable method was the two stage residual inclusion method. We recommend using adaptive power calculations, updating them as refusal rates are collected in the trial recruitment phase in order to be sufficiently powered for IV analysis

Validity, Reliability, and Differential Item Functioning of English and French Versions of the 10-Item Connor-Davidson Resilience Scale in Systemic Sclerosis: A Scleroderma Patient-Centered Intervention Network Cohort Study

Objective Some individuals with systemic sclerosis (SSc) report positive mental health, despite severe disease manifestations, which may be associated with resilience, but no resilience measure has been validated in SSc. This study was undertaken to assess the validity, reliability, and differential item functioning (DIF) between English- and French-language versions of the 10-item Connor-Davidson Resilience Scale (CD-RISC-10) in SSc. Methods Eligible participants were enrolled in the Scleroderma Patient-centered Intervention Network Cohort and completed the CD-RISC-10 between August 2022 and January 2023. We used confirmatory factor analysis (CFA) to evaluate the CD-RISC-10 factor structure and conducted DIF analysis across languages with Multiple Indicators Multiple Causes models. We tested convergent validity with another measure of resilience and measures of self-esteem and depression and anxiety symptoms. We assessed internal consistency and test–retest reliability using Cronbach\u27s alpha and intraclass correlation coefficient (ICC). Results A total of 962 participants were included in this analysis. CFA supported a single-factor structure (Tucker–Lewis index = 0.99, comparative fit index = 0.99, root mean square error of approximation = 0.08 [90% confidence interval (90% CI) 0.07, 0.09]). We found no meaningful DIF. Internal consistency was high (α = 0.93 [95% CI 0.92, 0.94]), and we found that correlations with other measures of psychological functioning were moderate to large (|r| = 0.57–0.78) and confirmed study hypotheses. The scale showed good 1–2-week test–retest reliability (ICC 0.80 [95% CI 0.75, 0.85]) in a subsample of 230 participants. Conclusion The CD-RISC-10 is a valid and reliable measure of resilience in SSc, with score comparability across English and French versions

Examination of the association of sex and race/ethnicity with appearance concerns: A Scleroderma Patient-centered Intervention Network (SPIN) cohort study

Objective: Appearance concerns are common in systemic sclerosis (SSc) and have been linked to younger age and more severe disease. No study has examined their association with sex or race/ethnicity. Methods: SSc patients were sampled from the Scleroderma Patient-centered Intervention Network Cohort. Presence of appearance concerns was assessed with a single item, and medical and sociodemographic information were collected. Results: Of 644 patients, appearance concerns were present in 72%, including 421 of 565 women (75%), 42 of 79 men (53%), 392 of 550 patients who identified as White (71%), 35 of 41 who identified as Black (85%), and 36 of 53 who identified as another race/ethnicity (68%). In multivariate analysis, women had significantly greater odds of reporting appearance concerns than men (odds ratio (OR)=2.97, 95% confidence interval (CI)=1.78-4.95,

Excavator Wheel Drive Reconstruction.

Import 05/08/2014V této práci je popsán pomocný pohon kolesa rypadla a možnost jeho rozběhu softstartérem a frekvenčním měničem. V první části je probrán asynchronní motor s kotvou nakrátko, jeho popis a princip funkce. Další části se věnují softstartéru a frekvenčnímu měniči, jejich popisu, funkcím a možnostem řízení. Dále je zde provedeno měření jejich vlivu na síť. Poslední část je věnována návrhu rekonstrukce pohonu pro napájení s frekvenčním měničem.This thesis describes the auxiliary drive wheel excavators and the possibility of starting the softstarter and frequency converter. In the first part of the document the asynchronous motor with squirrel cage is discussed, its description and function. Other parts of the document are devoted to the soft starter and frequency converter, their description, function and management options. Furthermore, there is performed measurement of their effect on the network. The last section is devoted to the design of the reconstruction drive with the frequency converter.410 - Katedra elektroenergetikyvýborn