The spread of the COVID-19 virus has brought forward a global pandemic that has halted many businesses and placed restrictions on daily activities. Vaccination of residents is crucial for a small country like Qatar to contain the spread of the virus. This study will aim to investigate and report the general outlook of Qatari residents toward the vaccine, the points of hesitancies, and how the contact tracing application (Ehteraz) can play a role in promoting vaccination. A questionnaire survey was given, and respondents answered a series of background questions and questions related to vaccine hesitancy and the effectiveness of the Ehteraz application. A broad search strategy was used to identify the main contributors to willingness and hesitancy with the COVID-19 vaccination. Regression models and test-train machine learning techniques were used for analysis. The results showed that dominance analysis was effective in highlighting the main barriers and promoters in taking the vaccine and that respondent's characteristics can be used to predict vaccination attitude.

Total hip replacement (THR) is a common orthopedic surgery technique that helps thousands of individuals to live normal lives each year. A hip replacement replaces the shattered cartilage and bone with an implant. Most hip implants fail after 10–15 years. The material selection for the total hip implant systems is a major research field since it affects the mechanical and clinical performance of it. Stress shielding due to excessive contact stress, implant dislocation due to a large deformation, aseptic implant loosening due to the particle propagation of wear debris, decreased bone remodeling density due to the stress shielding, and adverse tissue responses due to material wear debris all contribute to the failure of hip implants. Recent research shows that pre-clinical computational finite element analysis (FEA) can be used to estimate four mechanical performance parameters of hip implants which are connected with distinct biomaterials: von Mises stress and deformation, micromotion, wear estimates, and implant fatigue. In vitro, in vivo, and clinical stages are utilized to determine the hip implant biocompatibility and the unfavorable local tissue reactions to different biomaterials during the implementation phase. This research summarizes and analyses the performance of the different biomaterials that are employed in total hip implant systems in the pre-clinical stage using FEA, as well as their performances in in vitro, in vivo, and in clinical studies, which will help researchers in gaining a better understanding of the prospects and challenges in this field.

With an expectation of an increased number of revision surgeries and patients receiving orthopedic implants in the coming years, the focus of joint replacement research needs to be on improving the mechanical properties of implants. Head-stem trunnion fixation provides superior load support and implant stability. Fretting wear is formed at the trunnion because of the dynamic load activities of patients, and this eventually causes the total hip implant system to fail. To optimize the design, multiple experiments with various trunnion geometries have been performed by researchers to examine the wear rate and associated mechanical performance characteristics of the existing head-stem trunnion. The objective of this work is to quantify and evaluate the performance parameters of smooth and novel spiral head-stem trunnion types under dynamic loading situations. This study proposes a finite element method for estimating head-stem trunnion performance characteristics, namely contact pressure and sliding distance, for both trunnion types under walking and jogging dynamic loading conditions. The wear rate for both trunnion types was computed using the Archard wear model for a standard number of gait cycles. The experimental results indicated that the spiral trunnion with a uniform contact pressure distribution achieved more fixation than the smooth trunnion. However, the average contact pressure distribution was nearly the same for both trunnion types. The maximum and average sliding distances were both shorter for the spiral trunnion; hence, the summed sliding distance was approximately 10% shorter for spiral trunnions than that of the smooth trunnion over a complete gait cycle. Owing to a lower sliding ability, hip implants with spiral trunnions achieved more stability than those with smooth trunnions. The anticipated wear rate for spiral trunnions was 0.039 mm3, which was approximately 10% lower than the smooth trunnion wear rate of 0.048 mm3 per million loading cycles. The spiral trunnion achieved superior fixation stability with a shorter sliding distance and a lower wear rate than the smooth trunnion; therefore, the spiral trunnion can be recommended for future hip implant systems.

The main purpose of this study is to analyze and evaluate the psychology of Muslim investors in stock investments during COVID-19 pandemic. This research uses data collected through online questionnaires conducted in May 2020, and employ Path Analysis to make sense of the data. This study finds that the psychology of Muslim investors investing in stock markets during the COVID-19 pandemic is irrational and intuitive. Muslim investors react quickly without resorting to any fundamental/technical analysis. Muslim investors are willing to take risks and cut losses in this situation. In addition, the psychology of Muslim investors with respect to religiosity is at the second level of Homo Islamicus' self-interest, namely Al-Nafs Al-Lawamah.

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