Analysis, Design and Implementation of a Resonant Solid State Transformer

This thesis discusses the design of a full-bridge resonant LLC Solid State Transformer. The proposed topology uses a high-frequency transformer which helps minimizing its cost and size, and enables operating at varying load conditions. By using a resonant circuit, soft switching is achieved. Commutation techniques are discussed, namely ZVS and ZCS. Both concepts are applied on different legs of the H-bridge. Pulse frequency modulation (PFM) and Phase Shifting Modulation (PSM) are utilized to control this resonant converter. One of the requirements of this work is to achieve a tightly regulated DC bus voltage. This was shown to be achieved using the proposed controller. An experimental setup was assembled and the controller was tested, the results match the simulation and calculation results. The SST setup was tested for two different power levels. The outputs confirm the validity of the controller in feeding the load and regulating the voltage within the desired switching frequency interval, while maintaining soft switching. A thermal analysis was conducted to calculate losses, and a conversion efficiency of 97.18% was achieved. Using a high frequency transformer, a reduction in size and cost is achieved as compared to conventional low frequency transformers that usually are large in size and require more material to be assembled (copper and iron). Design requirements and limitations, the proposed control scheme, modeling and implementation, and test results are provided in this thesis

Food Consumption Frequency, Perceived Stress, and Depressive Symptoms Among Female University Students in Dubai, United Arab Emirates

This study assessed whether perceived stress and depressive symptoms were associated with the frequency of consumption of specific food groups among female university students. A cross-sectional study was conducted among female university students using a simple random sampling method. The response rate was 97%, with a total number of 385 participants. The associations between stress levels and most/least-consumed food groups, and between depressive symptoms levels and most/least-consumed food groups were assessed. The questionnaire included a 12-item self-administered food frequency questionnaire, Cohen\u27s Perceived Stress Scale, and the Beck Depression Inventory-II. The study was approved by the University Ethical Committee prior to the data collection. One-way Analysis of Variance (ANOVA) and an independent-sample t-test were performed to test the equality of population means across the categories of each independent variable depending on the number of categories of the independent variable. Overall, this group of female university students fell under the mild mood disturbance category (depressive symptoms) (BDI-II) and had moderate perceived stress (PSS). Perceived stress was associated with more frequent consumption of salad/raw vegetables and cooked vegetables and less frequent consumption of cake/cookies and meat/sausage products (p \u3c 0.05). Additionally, depressive symptoms were associated with less frequent consumption of fresh fruits and increased consumption of fast food/canned food and soft drinks (p \u3c 0.05). The data showed that stress and depression were associated with different dietary preferences, which is consistent with the distinctions between stress and depression in human behavior. Specifically, the results revealed associations between soft drinks consumption and higher depressive symptoms and between frequent consumption of salad/raw vegetables and cooked vegetables and higher perceived stress among this group of female university students

Fragment-Based Design of Mycobacterium tuberculosis InhA Inhibitors.

Tuberculosis (TB) remains a leading cause of mortality among infectious diseases worldwide. InhA has been the focus of numerous drug discovery efforts as this is the target of the first line pro-drug isoniazid. However, with resistance to this drug becoming more common, the aim has been to find new clinical candidates that directly inhibit this enzyme and that do not require activation by the catalase peroxidase KatG, thus circumventing the majority of the resistance mechanisms. In this work, the screening and validation of a fragment library are described, and the development of the fragment hits using a fragment growing strategy was employed, which led to the development of InhA inhibitors with affinities of up to 250 nM

Fragment-Based Approach to Targeting Inosine-5'-monophosphate Dehydrogenase (IMPDH) from Mycobacterium tuberculosis.

Tuberculosis (TB) remains a major cause of mortality worldwide, and improved treatments are needed to combat emergence of drug resistance. Inosine 5'-monophosphate dehydrogenase (IMPDH), a crucial enzyme required for de novo synthesis of guanine nucleotides, is an attractive TB drug target. Herein, we describe the identification of potent IMPDH inhibitors using fragment-based screening and structure-based design techniques. Screening of a fragment library for Mycobacterium thermoresistible ( Mth) IMPDH ΔCBS inhibitors identified a low affinity phenylimidazole derivative. X-ray crystallography of the Mth IMPDH ΔCBS-IMP-inhibitor complex revealed that two molecules of the fragment were bound in the NAD binding pocket of IMPDH. Linking the two molecules of the fragment afforded compounds with more than 1000-fold improvement in IMPDH affinity over the initial fragment hit

Eating habits and lifestyle during covid-19 lockdown in the united arab emirates: A cross-sectional study

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. The coronavirus disease is still spreading in the United Arab Emirates (UAE) with subsequent lockdowns and social distancing measures being enforced by the government. The purpose of this study was to assess the effect of the lockdown on eating habits and lifestyle behaviors among residents of the UAE. A cross-sectional study among adults in the UAE was conducted using an online questionnaire between April and May 2020. A total of 1012 subjects participated in the study. During the pandemic, 31% reported weight gain and 72.2% had less than eight cups of water per day. Furthermore, the dietary habits of the participants were distanced from the Mediterranean diet principles and closer to “unhealthy” dietary patterns. Moreover, 38.5% did not engage in physical activity and 36.2% spent over five hours per day on screens for entertainment. A significantly higher percentage of participants reported physical exhaustion, emotional exhaustion, irritability, and tension “all the time” during the pandemic compared to before the pandemic (p \u3c 0.001). Sleep disturbances were prevalent among 60.8% of the participants during the pandemic. Although lockdowns are an important safety measure to protect public health, results indicate that they might cause a variety of lifestyle changes, physical inactivity, and psychological problems among adults in the UAE

Impact of the Coronavirus Pandemic (COVID-19) Lockdown on Mental Health and Well-Being in the United Arab Emirates

United Arab Emirates (UAE) has taken unprecedented precautionary measures including complete lockdowns against COVID-19 to control its spread and ensure the well-being of individuals. This study investigated the impact of COVID-19 and societal lockdown measures on the mental health of adults in the UAE. A cross-sectional study was conducted using an English and Arabic online questionnaire between May and June 2020. The psychological impact was assessed by the Impact of Event Scale-Revised (IES-R), and the social and family support impact was evaluated using questions from the Perceived Support Scale (PSS). A total of 4,426 participants (3,325 females and 1,101 males) completed the questionnaire. The mean IES-R score was 28.0 ± 14.6, reflecting a mild stressful impact with 27.3% reporting severe psychological impact. Over 36% reported increased stress from work, home and financial matters. Also, 43–63% of the participants felt horrified, apprehensive or helpless due to COVID-19. Females, younger participants, part-timers, and college or University graduates were more likely to have a high IES-R score (p \u3c 0.05). The majority of participants reported receiving increased support from family members, paying more attention to their mental health, and spending more time to rest and relax. The results of this study demonstrate the impact of the COVID-19 pandemic on mental health among the UAE residents and highlight the need to adopt culturally appropriate interventions for the general population and vulnerable groups, such as females and younger adults

Assessment of Dietary and Lifestyle Responses After COVID-19 Vaccine Availability in Selected Arab Countries

The COVID-19 pandemic has been consistently associated with unhealthy lifestyle behaviors and dietary practices. This study aimed to assess the dietary and lifestyle behaviors of adults after COVID-19 vaccine availability and their attitude toward the vaccine in selected Arab countries. A cross-sectional survey-based study was conducted between October 2021 and December 2021 using Google Forms (n = 2259). A multi-component questionnaire was used to collect socio-demographic characteristics, attitudes toward the COVID-19 vaccine, and behavioral, dietary, and lifestyle responses after easing the restriction. Participants were given a score based on the sum of positive dietary and lifestyle changes. The generalized linear models were used to identify the association between positive dietary and lifestyle changes score and sociodemographic characteristics. Weight gain during the pandemic was reported by 39.5% of the participants, 36.1% reported ever getting infected with the COVID-19 virus, and 85% received at least one dose of the vaccine. The key adverse reactions of the COVID-19 vaccine were fatigue, headache, and joint pain, and the main reason for vaccination was protection against infection. Most participants were concerned about the vaccine side effects (45.8%) and inadequate testing (50.7%). After easing of restriction, 54.3% of the participants reduced the frequency of disinfecting objects, and 58.3% joined social events. Most dietary and lifestyle behaviors remained unchanged after vaccine availability but there was an increase in the time spent behind the screen for work (50.1%) and entertainment (42.9%). The results of the multivariate regression analyses revealed that older participants (p = 0.001), those with higher education (p = 0.010), and those working from home (p = 0.040) were more likely to have higher positive dietary and lifestyle changes scores. Although most participants were concerned about vaccine safety, low vaccine hesitancy rates were observed among the study sample. The availability of the COVID-19 vaccines resulted in loosening some of the safety social measures among Arab adults but the negative impact of the pandemic on dietary and lifestyle behaviors remained unaltered

Assessment of Eating Habits and Lifestyle during Coronavirus Pandemic in the MENA region: A Cross-Sectional Study

© The Authors 2020. The coronavirus disease (COVID-19) has rapidly spread globally, forcing countries to apply lockdowns and strict social distancing measures. The aim of this study was to assess eating habits and lifestyle behaviors among residents of the Middle East and North Africa (MENA) region during the lockdown. A cross-sectional study among adult residents of the MENA region was conducted using an online questionnaire designed on Google Forms during April 2020. A total of 2970 participants from 18 countries participated in the current study. During the pandemic, over 30% reported weight gain, 6.2% consumed five or more meals per day compared to 2.2% before the pandemic (p\u3c0.001), and 48.8% did not consume fruits on daily basis. Moreover, 39.1% did not engage in physical activity, over 35% spent more than five hours per day on screens. A significant association between the frequency of training during the pandemic and the reported change in weight was found (p \u3c 0.001). A significantly higher percentage of participants reported physical and emotional exhaustion, irritability, and tension either all the time or a large part of the time during the pandemic (p \u3c 0.001). Although a high percentage of participants reported sleeping more hours per night during the pandemic, 63% had sleep disturbances. The study highlights that the lockdown due to the COVID-19 pandemic caused a variety of lifestyle changes, physical inactivity, and psychological problems among adults in the MENA region

Synthesis and biological evaluation of new inhibitors of bacterial quorum sensing

Les bactéries sont capables de communiquer entre elles afin de coordonner l’expression de certains gènes en fonction de leur densité de population. Ce système de communication utilise de petites molécules appelées autoinducteurs (AIs) comme messagers chimiques et est connu sous le nom de Quorum Sensing (QS). Chez les bactéries pathogènes, les gènes régulés sont, en particulier, ceux codant pour la production des facteurs de virulence et la structuration des biofilms. Ainsi des inhibiteurs du QS chez ces bactéries pourraient être de nouveaux agents anti-bactériens alternatifs aux antibiotiques actuels. Chez les bactéries à Gram-négatif, les AIs sont très majoritairement des acyl-homosérine lactones (AHLs). Utilisant deux approches, la conception rationnelle et le criblage virtuel, nous avons découvert cinq nouvelles familles d’antagonistes des AHLs, ainsi qu’un certain nombre d’agonistes. Nous avons également préparé des analogues d’antagonistes naturels de la famille des bromo-furanones, afin d’établir une étude structure-activité de ce type de composés.The bacteria are able to communicate with each other for coordinating gene expression depending on their population density. This communication system use small molecules called autoinducers (AIs) as chemical messengers and is referred to as quorum sensing (QS). In pathogenic bacteria, the regulated genes are, in particular, those coding for the production of virulence factors and biofilms formation. Thus, inhibitors of bacterial QS could be used as new anti-bacterial agents providing an alternative to current antibiotics. In Gram-negative bacteria, the main AIs are acyl-homoserine lactones (AHLs). Using two approaches, rational design and virtual screening, we have discovered five new families of AHLs antagonists, and some agonists. We have also prepared analogues of natural bromo-furanones antagonists, in order to establish a structure-activity study of this type of compounds

The association of leadership styles and nurses well-being: a cross-sectional study in healthcare settings

Introduction: the nurses´ perception of their supervisors´ leadership styles has a substantial impact on their well-being. Effective leadership in health care is crucial in improving and enhancing the effectiveness of health care systems. This study aims to assess the leadership styles of nurse leaders as perceived by employees, and to explore the relationship between perceived leadership styles and the quality of life of nurses in Lebanese hospital settings. Methods: it was a cross-sectional study conducted in 2017 and involved a sample of 250 nurses chosen randomly in eight hospitals. The survey included questions on socio-demographic and health-related characteristics, Multifactor Leadership Questionnaire 5X Short Form, and the Short Form Health Survey-12 V2 (SF-12v2). Results: the managers used enough transformational leadership style, whereas they used fairly often transactional leadership. The Laissez-faire style was adopted from time to time by the managers. Male nurses perceive their managers as transformational significantly more than female nurses (2.94 vs. 2.73; p = 0.05). Transformational leadership style was statistically related to all scales scores of the SF-12v2 (p < 0.001) except the Social Functioning domain (p = 0.42). The transactional leadership style was associated with the Vitality scale scores (p < 0.001). The physical (p < 0.05) and Emotional Role (p < 0.001) and the mental health summary measure (p < 0.05) were lower in persons who perceived the leadership style of their manager as Laissez-faire. Conclusion: this study highlights the existence of a positive effect of leadership styles in the wellbeing of nurses, and confirms that nursing management has been identified as a challenge in the Lebanese hospitals