Symmetric and Asymmetric Multilevel Inverter Topologies With Reduced Device Count

In this work, two new topologies of single-phase hybrid multilevel inverters for symmetrical and asymmetrical configurations are presented for use in drives and control of electrical machines and the connection of renewable energy sources. The proposed topology uses 2 dc sources, 12 switches, 1 flying capacitor, and 3 diodes to generate boosted 13-levels and 17-levels for symmetric and asymmetric configuration, respectively. Self-voltage balancing of its capacitor voltage regardless of load type, load dynamics, or modulation index is a key advantage of the suggested design. The higher performance of proposed topologies in terms of the total number of switches, TSV, THD, switch stress, and dc sources are demonstrated by comparing those with recently published topologies. In addition, a widely employed nearest level control modulation approach is used to provide output voltage levels with low THD. Finally, experiments were undertaken to validate the performance of the suggested topology. 2013 IEEE.This work was supported in part by Qatar University Research Grant from Qatar University, Doha, Qatar, under Grant QUCP-CENG-2020-2 and Grant QUCP-CENG-2022-571; and in part by the Qatar National Library, Doha.Scopu

Enhanced moisture adsorption of activated carbon through surface modification

Activated carbons are widely used as adsorbents in industries for various applications. The mechanism of moisture interaction with the industrial adsorbents is complex and yet to be clearly elucidated. The adsorption mechanism heavily depends on several parameters that include the pore size and distribution, surface chemistry, and treatment conditions. Various surface functional groups on the carbonaceous materials play a significant role in water adsorption, mainly the oxygen-containing functional groups (OFGs). A commercial mesoporous steam-activated carbon was subjected to surface modification on treatment with strong oxidizing agents and subjected to the adsorption of moisture. The isotherms were generated covering a temperature range of 30–50 °C. The adsorption capacity was observed to significantly improve post-treatment with oxidizing agents, while the effect was observed to be profound at lower partial pressures. A sharp increase in the moisture uptake indicates that the oxidized carbons have a higher affinity to moisture even at low concentrations and this could have a significant influence on the targeted molecules, since the moisture as a contaminant is expected to be present at low partial pressures. On the other hand, such a trend is highly favorable if carbon is to serve as a sorbent for the removal of moisture, as several-fold improvements in adsorption capacity were noticed as compared to virgin AC. Additionally, the adsorption capacity was also found to be significantly higher as compared to popular moisture adsorbents, such as silica gel and zeolites, especially at low partial pressures

Expert Opinion on the Management of Non-Alcoholic Fatty Liver Disease (NAFLD) in the Middle East with a Focus on the Use of Silymarin

Non-alcoholic fatty disease (NAFLD) is amongst the leading causes of chronic liver disease worldwide. The prevalence of NAFLD in the Middle East is 32%, similar to that observed worldwide. The clinicians in this region face several challenges in diagnosing and treating patients with NAFLD. Additionally, there are no national or regional guidelines to address the concerns faced with current treatment options. Silymarin, derived from milk thistle, provides a rational and clinically proven approach to hepatoprotection. This article focuses on addressing regional diagnostic challenges and provides clear guidance and potential solutions for the use of Silymarin in the treatment of NAFLD in the Middle East. Both clinical and preclinical studies have highlighted the efficiency of Silymarin in managing NAFLD by reducing liver disease progression and improving patient symptoms and quality of life, alongside being safe and well tolerated. An expert panel of professionals from the Middle East convened to establish a set of regional-specific diagnostics. A consensus was established to aid general physicians to address the diagnostic challenges in the region. In conclusion, Silymarin can be considered beneficial in treating NAFLD and should be initiated as early as possible and continued as long as necessary

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population