The mechanical contact behaviour and tribology of polymer gears

Interest in using polymer gears has been growing dramatically in the last decade. Increasing understanding of their working behaviour has improved appreciation of their advantages compared to their limitations when selecting appropriate applications. However, restricted knowledge still leaves many unfulfilled areas that might benefit from their valuable advantages and control of their limitations, for example, in replacing. their metallic counterparts in more applications. Given their very different materials properties, it is important to develop bespoke design and rating methods for polymer gears, with properly validated rules, that are not mere modifications to metallic gearing rating methods. A major aim of this thesis is to provide a new deeper understanding for use when designing and rating some technologically important types of polymer gears for wider applications. Having identified an important research gap in polymer gearing theory and practice, this thesis covers mostly experimental studies involving continuously monitored wear and wear rate and microscopic evaluation of underlying tribologies. It examines the behaviour of polymer gears made of acetal, nylon (moulded and machine-cut) and polycarbonate, all common gearing materials, during and after running under different physically realistic conditions. Some modifications to test rigs uniquely designed to operate at a continually constant load enable study of surface thermal behaviour under dry and lubricated conditions and with simulations of moderate gear misalignments. In dry-running cases, gear load capacity and wear behaviour of different polymers and variations in underlying tribology all presented important relations between the gear tooth wear rate, the applied load and the tooth surface temperature. Quite similar patterns were seen under oil lubricated conditions. Typically, though, there was a nearly three-fold improvement in gear load capacity, the wear rate and gear tooth surface temperature were decreased, and SEM showed some changes in surface tribology. Finally, deliberately introduced angular misalignments between gear pairs indicated a reasonable tolerance of small but practical levels, with different tribological behaviours between the left and right sides of the tooth surfaces. A severe increase in wear rate and tooth failure arose from misalignments above 0.8ο yaw angle and 0.4ο pitch angle. After a unifying discussion, conclusions are drawn and further work is proposed for extended studies over different parameter ranges

Public satisfaction with COVID-19 vaccination program in Saudi Arabia

The challenges posed by the ongoing COVID-19 pandemic have required the introduction of new care delivery models and procedures. For the foreseeable future, vaccine administration will be a key part of the patient experience journey. It is important therefore to understand and evaluate experiences of individuals taking the vaccination, an area which requires considerable attention. To address this, the COVID-19 Vaccination Satisfaction survey was developed and administered at several healthcare facilities across Saudi Arabia. Between January 2021 and end of December 2021, a total of 1,699,177 completed surveys were collected. The survey results suggest high satisfaction among participants taking the vaccine; however, satisfaction with information and communication about the vaccine was relatively low. Results from this survey are updated daily and provide unique insights into the key strengths of the vaccination process, as well as aspects within the process that require improvement. Experience Framework This article is associated with the Policy & Measurement lens of The Beryl Institute Experience Framework. (https://www.theberylinstitute.org/ExperienceFramework). Access other PXJ articles related to this lens. Access other resources related to this lens

Analysis of rotating-symmetric frame and MHD for peristaltic multiphase flow: An exact solution

The rotational mechanism forms the basis of various cosmic and geophysical transports. In medical science, rotational blood flows have been related to healthy cardiac function. This study consists of a mathematical model representing magnetohydrodynamic effects on the two-phase pumping flow of a Ree–Eyring–Powell stress model in a rotating frame. The model is controlled by switching the system into a wave frame of reference for better analysis of the wave phenomenon. Moreover, a lubrication theory is applied to the resulting set of relations in order to get a more comprehensive form of the reduced mathematical model. In the end, an exact solution is found to discuss the substantial contents of the study. The data on velocity and stream function are presented diagrammatically to examine the theoretical behavior of various quantities under the variation of considerable physical factors. It is concluded from the graphs that axial and secondary velocities are decreasing against rotation, magnetic field, and fluid’s factor, but the same rise in the case of wall stiffness and particle concentration. In both industrial and biomedical applications, this type of flow measurement gives tomographic information on the multiphase flow process, which entails acquiring signal changes at the edges of objects like fluid pipes or blood vessels to determine how the objects are distributed within. This work is extendable by considering nanoparticles of various types to enhance the thermal conductivity of the flow

In vivo and in vitro studies evaluating the chemopreventive effect of metformin on the aryl hydrocarbon receptor-mediated breast carcinogenesis

Metformin (MET) is a clinically used anti-hyperglycemic agent that shows activities against chemically-induced animal models of cancer. A study from our laboratory showed that MET protectes against 7, 12-dimethylbenz[a]anthracene (DMBA)-induced carcinogenesis in vitro human non-cancerous epithelial breast cells (MCF10A) via activation of the aryl hydrocarbon receptor (AhR). However, it is unclear whether MET can prevent the initiation of breast carcinogenesis in an in vivo rat model of AhR-induced breast carcinogenesis. Therefore, the main aims of this study are to examine the effect of MET on protecting against rat breast carcinogenesis induced by DMBA and to explore whether this effect is medicated through the AhR pathway. In this study, treatment of female rats with DMBA initiated breast carcinogenesis though inhibiting apoptosis and tumor suppressor genes while inducing oxidative DNA damage and cell cycle proliferative markers. This effect was associated with activation of AhR and its downstream target genes; cytochrome P4501A1 (CYP1A1) and CYP1B1. Importantly, MET treatment protected against DMBA-induced breast carcinogenesis by restoring DMBA effects on apoptosis, tumor suppressor genes, DNA damage, and cell proliferation. Mechanistically using in vitro human breast cancer MCF-7 cells, MET inhibited breast cancer stem cells spheroids formation and development by DMBA, which was accompanied by a proportional inhibition in CYP1A1 gene expression. In conclusion, the study reports evidence that MET is an effective chemopreventive therapy for breast cancer by inhibiting the activation of CYP1A1/CYP1B1 pathway in vivo rat model

The Importance of Preventive Medicine in Family Practice: A Review of Current Guidelines and Recommendations

Prevention is seen as a critical topic in family practice. Primordial prevention, primary prevention, secondary prevention, tertiary prevention, and quaternary prevention are all part of this strategy to disease prevention. To avoid the formation and development of risk factors, primary prevention focuses on addressing the fundamental causes and social determinants of disease. Primary prevention is the practice of preventing illnesses before they arise via the use of treatments such as immunizations and health education. Secondary prevention focuses on illness identification and intervention as early as possible to avoid disease development. Tertiary prevention addresses illness outcomes by restoring health and offering rehabilitation. Finally, quaternary prevention seeks to safeguard patients against needless medical treatments and the harm caused by over-medicating. Risks frequently rise in tandem with frailty and comorbidities. In contrast, advantages frequently drop as life expectancy increases. Preventive management strategies should consider the patient's viewpoint and be mutually agreed upon. Healthcare providers must prioritize the deployment of preventive care services, even when clinical treatments are required, in order to overcome preventive care hurdles. Healthcare practitioners may play a critical role in illness prevention and contribute to family well-being by investing in preventive care and executing these measures

Influence of Adiposity-Related Genetic Markers in a Population of Saudi Arabians Where Other Variables Influencing Obesity May Be Reduced

Large scale studies in Europeans have clearly identified common polymorphism affecting BMI and obesity. We undertook a genotype study to examine the impact of variants, known to influence obesity, in a sample from the Saudi Arabian population, notable for its profound combination of low mean physical activity indices and high energy intake. Anthropometry measures and genotypes were obtained for 367 Saudis, taken from King Saud University and Biomarker Screening Project in Riyadh (Riyadh Cohort). We observed large effect sizes with obesity for rs10767664 (BDNF) (OR = 1.923, P=0.00072) and rs3751812 (FTO) (OR = 1.523, P=0.016) in our sample and, using weighted genetic risk scores, we found strong evidence of a cumulative effect using 11 SNPs taken predominantly from loci principally affecting appetite (OR = 2.57, P=0.00092). We used conditional analyses to discern which of our three highly correlated FTO SNPs were responsible for the observed signal, although we were unable to determine with confidence which best marked the causal site. Our analysis indicates that markers located in loci known to influence fat mass through increased appetite affect obesity in Saudi Arabians to an extent possibly greater than in Europeans. Larger scale studies will be necessary to obtain a precise comparison

Genome-Wide Analysis of the Emerging Infection with Mycobacterium avium Subspecies paratuberculosis in the Arabian Camels (Camelus dromedarius)

Mycobacterium avium subspecies paratuberculosis (M. ap) is the causative agent of paratuberculosis or Johne's disease (JD) in herbivores with potential involvement in cases of Crohn's disease in humans. JD is spread worldwide and is economically important for both beef and dairy industries. Generally, pathogenic ovine strains (M. ap-S) are mainly found in sheep while bovine strains (M. ap-C) infect other ruminants (e.g. cattle, goat, deer), as well as sheep. In an effort to characterize this emerging infection in dromedary/Arabian camels, we successfully cultured M. ap from several samples collected from infected camels suffering from chronic, intermittent diarrhea suggestive of JD. Gene-based typing of isolates indicated that all isolates belong to sheep lineage of strains of M. ap (M. ap-S), suggesting a putative transmission from infected sheep herds. Screening sheep and goat herds associated with camels identified the circulation of this type in sheep but not goats. The current genome-wide analysis recognizes these camel isolates as a sub-lineage of the sheep strain with a significant number of single nucleotide polymorphisms (SNPs) between sheep and camel isolates (∼1000 SNPs). Such polymorphism could represent geographical differences among isolates or host adaptation of M. ap during camel infection. To our knowledge, this is the first attempt to examine the genomic basis of this emerging infection in camels with implications on the evolution of this important pathogen. The sequenced genomes of M. ap isolates from camels will further assist our efforts to understand JD pathogenesis and the dynamic of disease transmission across animal species

Survival implications vs. complications: unraveling the impact of vitamin D adjunctive use in critically ill patients with COVID-19—A multicenter cohort study

BackgroundDespite insufficient evidence, vitamin D has been used as adjunctive therapy in critically ill patients with COVID-19. This study evaluates the effectiveness and safety of vitamin D as an adjunctive therapy in critically ill COVID-19 patients.MethodsA multicenter retrospective cohort study that included all adult COVID-19 patients admitted to the intensive care units (ICUs) between March 2020 and July 2021. Patients were categorized into two groups based on their vitamin D use throughout their ICU stay (control vs. vitamin D). The primary endpoint was in-hospital mortality. Secondary outcomes were the length of stay (LOS), mechanical ventilation (MV) duration, and ICU-acquired complications. Propensity score (PS) matching (1:1) was used based on the predefined criteria. Multivariable logistic, Cox proportional hazards, and negative binomial regression analyses were employed as appropriate.ResultsA total of 1,435 patients were included in the study. Vitamin D was initiated in 177 patients (12.3%), whereas 1,258 patients did not receive it. A total of 288 patients were matched (1:1) using PS. The in-hospital mortality showed no difference between patients who received vitamin D and the control group (HR 1.22, 95% CI 0.87–1.71; p = 0.26). However, MV duration and ICU LOS were longer in the vitamin D group (beta coefficient 0.24 (95% CI 0.00–0.47), p = 0.05 and beta coefficient 0.16 (95% CI −0.01 to 0.33), p = 0.07, respectively). As an exploratory outcome, patients who received vitamin D were more likely to develop major bleeding than those who did not [OR 3.48 (95% CI 1.10, 10.94), p = 0.03].ConclusionThe use of vitamin D as adjunctive therapy in COVID-19 critically ill patients was not associated with survival benefits but was linked with longer MV duration, ICU LOS, and higher odds of major bleeding