Bias-dependence of luminescent coupling efficiency in multijunction solar cells.

In this work, we demonstrate an improved method to simulate the characteristics of multijunction solar cell by introducing a bias-dependent luminescent coupling efficiency. The standard two-diode equivalent-circuit model with constant luminescent coupling efficiency has limited accuracy because it does not include the recombination current from photogenerated carriers. Therefore, we propose an alternative analytical method with bias-dependent luminescent coupling efficiency to model multijunction cell behavior. We show that there is a noticeable difference in the J-V characteristics and cell performance generated by simulations with a constant vs. bias-dependent coupling efficiency. The results indicate that introducing a bias-dependent coupling efficiency produces more accurate modeling of multijunction cell behavior under real operating conditions.

Demographic Characteristics and Status of Vaccinated Individuals with a History of COVID-19 Infection Pre- or Post-Vaccination: A Descriptive Study of a Nationally Representative Sample in Saudi Arabia.

BACKGROUND: Saudi Arabia expedited the approval of some COVID-19 vaccines and launched mass vaccination campaigns. The aim of this study was to describe the demographics of vaccinated COVID-19 cases and compare the mortality rates of COVID-19 cases who were infected post-vaccination in Saudi Arabia. METHODS: This was a retrospective cohort study. We retrieved data for COVID-19 cases who were infected pre- or post-vaccination and had received at least one injection of the Oxford-AstraZeneca or Pfizer-BioNTech vaccine from 4 December 2020 to 15 October 2021. RESULTS: The number of patients who were infected and had received at least one dose of a COVID-19 vaccine was 281,744. Approximately 45% of subjects were infected post-vaccination, and 75% of subjects had received the Pfizer-BioNTech vaccine. Only 0.342% of the patients who were infected post-vaccination died, and 447 patients were admitted to ICUs. Most of the patients who were infected with COVID-19 post-vaccination and were admitted to ICUs (69.84%) had received only one dose of the vaccine (p < 0.0001). The mean time to infection for patients who had received one and two doses of the Oxford-AstraZeneca vaccine were 27 and 8 days longer than their counterparts who had received one and two doses of Pfizer-BioNTech vaccine, respectively. No difference in the odds of mortality between the Pfizer-BioNTech and Oxford-AstraZeneca vaccines was found (OR = 1.121, 95% CI = [0.907-1.386], p-value = 0.291). Patients who had received two doses of the vaccine had significantly lower odds of mortality compared to those who had received one dose (p < 0.0001). CONCLUSIONS: Vaccines are vital in combating the COVID-19 pandemic. The results of this study show no difference between the Pfizer-BioNTech and Oxford-AstraZeneca vaccines in the rate of mortality. However, the number of vaccine doses was significantly associated with a lower risk of mortality. Future studies should examine the effectiveness of different COVID-19 vaccines using real-world data and more robust designs.

Frequency of Epidermal Growth Factor Receptor and T790M Mutations Among Patients With Non-Small Cell Lung Carcinoma: A Hospital-Based Study in the King Khalid University Hospital (KKUH) Since 2009-2017.

Objectives To estimate the proportion of positive epidermal growth factor receptor (EGFR) mutations among patients diagnosed with non-small cell lung carcinoma (NSCLC) and T790M at the King Khalid University Hospital (KKUH). Methods A retrospective cohort study that included all patients that were diagnosed with NSCLC from 2009 to 2017 at KKUH. Data obtained from both electronic and paper medical records and the following information were studied: age, gender, smoking, region, subtype of NSCLC, EGFR mutation test result, treatment, T790M mutation test (if required), comorbidities, metastasis. Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS, version 21.0; SPSS Inc., Chicago, IL, USA). Results Among 71 patients with NSCLC 18 cases were identified for EGFR positive mutation and only one case for T790M. Deletion mutation in exon 19 represented 50% of total cases. Moreover, it showed that it is more frequent in males and non-smokers with 61.1% (11) and 66.7% (12), respectively. Majority of the cases were above the age of 60 years by 61.1% (11). The mutations reported highest in those living in Najd with a 44.4% (8) and all the mutated cases were adenocarcinoma. There was no statistical significance in the association between EGFR mutation and disease variables. Conclusion Ultimately, we found that the frequency of EGFR and T790M mutations among NSCLC patients at KKUH from 2009 to 2017 was 25.4% and 1.4%, respectively. Moreover, this result was conspicuous among non-smokers.

The prevalence of Factor V Leiden (Arg506Gln) mutation in King Khalid University Hospital patients, 2017-2019.

Arg506Gln mutation is responsible for one of the procoagulant factors and most common inherited thrombophilia in the Factor V Leiden (FVL) family. The replacement of the missense mutation for Arg506Gln / R506Q is at 1691st position from Guanine to Adenine with the modification of the amino acid from arginine to glutamine. The aim of this study was to investigate the current prevalence of the G1691A mutation in the FVL gene in the capital city's King Khalid University Hospitals (KKUH). Since 2017-2019 we have recruited 482 patients in these cross-sectional studies to test the G1691A mutation in KKUH's FVL gene. DNA was extracted using 2mL of the EDTA blood and genotyping was performed with polymerase chain reaction and the data was analyzed using Sanger sequencing. In this study, 4.4% of the G1691A mutation was found to be positive (combined heterozygous-GA and homozygous-AA variants) and 95.6% of them with negative, i.e., homozygous normal-GG genotypes. Our study concludes that with the advances in genetic testing and their recent availability, early mutation detection could approve the genotype risks for many patients and this mutation is not as rare as previously believed in the Saudi region as our study has established with a 4.4 percent prevalence.

Using the Health Belief Model to Predict the Uptake of Mammographic Screening Among Saudi Women.

Background Breast cancer (BC) is known to be the second leading cause of cancer deaths after lung cancer in Saudi Arabia. Early detection using screening methods can improve disease outcomes. In Saudi Arabia, the rates of BC screening are very low although it is a country that provides free healthcare services. This discrepancy between the availability of free healthcare services and women not utilizing these services necessitates an in-depth understanding of the health-related beliefs and barriers towards BC screening among Saudi women.  Objective We aimed to use the Health Belief Model (HBM) to predict the uptake of mammographic screening among Saudi women. The secondary objective was to determine the knowledge, attitudes, and practices related to BC and mammography screening. Research methodology  This was an analytical cross-sectional study using a self-administered questionnaire, which consisted of sociodemographic data, family history of BC, general information about BC, and the Champion's Health Belief Model Scale (CHBMS). The study was conducted among Saudi women visiting the King Khalid University Hospital in Riyadh from September 2018 to February 2019. The data were analyzed using SPSS Statistics software version 26.00 (IBM, Armonk, NY). Results A total of 401 females participated in the study; the median age of the subjects was 49 years [interquartile range (IQR): 43-53 years]. Among them, 69.6% were married and 21.1% had a family history of BC. There was a statistically significant association of younger age, marital status, and a positive family history of BC with women undergoing mammographic screening (p<0.05). Of the participants, 61.6% knew about the warning signs of BC, while only 59.9% were aware of the risk factors associated with it. The binary logistic regression did not show any significant association between CHBMS and mammogram screening. We concluded that the CHBMS components cannot be used in isolation to predict the risk of not undergoing mammogram screening. However, barriers and motivation components along with the knowledge and other factors can be used to predict mammogram screening. Conclusion Among our cohort of Saudi women, 62.1% had general awareness about BC, and younger age, marital status, and positive family history of BC were significantly associated with women undergoing mammography screening. The CHBMS components cannot be used in isolation to predict the risk of not undergoing mammogram screening, while barriers and motivation components along with the knowledge and other factors can be used to predict mammogram screening.

Prevalence of biopsy-proven nonalcoholic fatty liver among patients with gallstone disease.

BACKGROUND/AIM: Gallstone disease (GD) and nonalcoholic fatty liver disease (NAFLD) are associated with metabolic syndrome. Despite the benign nature of NAFLD, 10% of patients may develop advanced fibrosis and cirrhosis. We aimed to identify the prevalence and factors associated with NAFLD among GD patients in the Saudi population. PATIENTS AND METHODS: This is a single-center, observational cohort study that included patients seen in general surgery clinics at our institution from 2011 to 2017. All liver biopsies were taken at the same time as the cholecystectomy. Demographical and clinical data were prospectively collected from the study population. RESULTS: Of the 301 GD patients in the study, 15% had a normal body mass index (BMI), 29% were overweight, and 56% were obese. There were 143 (47.8%) patients with NAFLD, of which 125 (41.8%) showed steatosis and 18 (6%) had nonalcoholic steatohepatitis. There was a significant positive correlation between NAFLD and age (r = 0.243; P < 0.0001), and BMI (r = 0.242; P < 0.0001). Obese patients with BMI 30-40 kg/m[2] were 2.403 (P = 0.039) more likely to have NAFLD compared with normal BMI patients, and this value increased to 6.145 (P = 0.002) in patients with BMI >40 kg/m[2]. Additionally, patients with T2DM were 2.839 times (P = 0.015) more likely to have NAFLD compared with those who did not. CONCLUSIONS: The prevalence of NAFLD among GD patients is high. High BMI and diabetes are independent factors associated with NAFLD in GD patients. The results suggest that there may be a need for routine liver biopsy in selected patients during cholecystectomy.