X-Ray Studies on Pt/Re and Other Compounds

In this thesis X-ray diffraction analysis is applied to the study of molecular structure and conformation. The contents are divided into four sections. The first section is a brief review of the theory and practical aspects of the X-ray diffraction methods used in sections two, three and four. Section two is concerned with the structure of ruthenium and platinum complexes stabilised by the diphosphine ligand Ph2PCH2PPh2 (dppm). First, earlier work on binuclear complexes, on triangular M3(dppm)3 species and on platinum cluster complexes is reviewed and the structure of the binuclear species [Ru2{mu- Cl)(mu-H)Cl2(CO)2}(mu-dppm)2] is described. Then the structures of five large heterometallic clusters derived from [Pt3{mu3-Re(CO)3}(mu-dppm)3]+ are presented. These clusters are obtained by reaction of the parent cluster with dioxygen, halide or neutral ligand. Their structures have been of critical importance to this new field of cluster chemistry. The characterisation of [Pt3(mu3-ReO3)(mu-dppm)3]+, which contains Pt(0) stabilised by phosphine and Re(VII) stabilised by oxide, is of particular significance. The section concludes with a summary of current knowledge of the chemistry of and bonding in platinum-rhenium clusters. Platinum-rhenium catalysts, for which the clusters are models, are also briefly described. Section three is concerned with the stereochemistry of newly synthesized organic compounds. The formation of oxazines by Diels-Alder addition of acylnitroso compounds is described in Chapter 3.1. The reaction typically involves the creation of chiral centres. The structural work has been directed at predicting the stereochemistry of the preferred diastereoisomer. In Chapter 3.2 the stereochemistry of Diels-Alder addition of ferrocene derivatives to 1,3-diphenylisobenzofuran is considered, with emphasis on the effect of AlCl3 catalysis on the nature of the product. In Chapter 3.3 the stereochemistry of cis and trans ArCH=CHAr molecules, and its relationship to their biological activity, is discussed. Section four describes the structure of tetramethoxycalix[4]arene silver(I) nitrate. The ability of calix[4]arenes to act as hosts has led to major developments in supramolecular chemistry. The attachment of silver(I) to the calixarene is of a novel type. The section also deals with the structures of mononuclear tungsten(II) complexes in which the metal atom could be six or seven co-ordinate

Crude and standardized prevalences of cataract and related factors in the elderly people in Northern Iran

Purpose: This study aims to estimate the crude and standardized prevalences of cataract and its related factors among old people in northern parts of Iran. Methods: This cross-sectional study was carried out among 397 people aged 60 and older in northern Iran. Required information about treated and nontreated cataract was collected using a standard checklist. The World Standard Population was applied for direct standardization. Results: The standardized prevalence (95% confidence interval) of cataract among men, women, and all people were 27.5% (21.2–33.8), 30.9% (24.5–37.4), and 29.1% (24.6–33.6), respectively. Based on multivariate logistic regression models, age over 75 years (OR = 3.03, 95% CI: 1.21–7.59), living alone (OR = 4.89, 95% CI: 1.86‒12.86), diabetes mellitus (odds ratio = 19.10, 95% confidence interval: 8.13–44.89), rheumatoid arthritis (OR = 7.76, 95% CI: 2.32–25.99), history of infectious diseases (OR = 4.02, 95% CI: 1.35‒11.98), hypertension (OR = 3.19, 95% CI: 1.59–6.42), history of ophthalmic surgery (OR = 2.83, 95% CI: 1.29–6.16), history of sedative drug use (OR = 2.71, 95% CI: 1.35–5.47), history of vitamin supplementation use (OR = 0.21, 95% CI: 0.08–0.55), and familial history of cataract (OR = 2.81, 95% confidence interval: 1.38–5.72) increased the odds of cataract. Our multiple logistic regression model explained 53% of the variation in developing cataract. Conclusion: Our study showed that the prevalence of cataract in the study population was relatively high. We also found that aging, living alone, diabetes mellitus, rheumatoid arthritis, hypertension, infectious diseases, ophthalmic surgery, sedative drugs and familial history of cataract were the risk factors of cataract and vitamin supplementations were its protective factors

Enhancing Memorable Experiences, Tourist Satisfaction, and Revisit Intention through Smart Tourism Technologies

Global connectivity facilitated tourism and redefined economic landscapes, highlight an interest in better understanding tourism retention factors. Today, in view of the global COVID-19 pandemic, this is made even more important as the world prepares to lift lockdown restrictions and to re-engage in cross border circulation; reiterating needs to understand tourism satisfaction and revisit intentions. This study thus sheds light on the predictors of tourists’ intention to the explorative and exploitative use of Smart Tourism Technologies (STTs) and memorable experiences in tourism destinations via an integrated model and a self-administered questionnaire—distributed among domestic tourists visiting Tehran—employing the Theory of Planned Behavior (TPB). The results indicated that tourists’ attitudes, subjective norms, and perceived behavioral control toward STTs had significant positive impacts on their explorative and exploitative intentions. Furthermore, tourists’ explorative/exploitative intention and perceived behavioral control exercised significant, positive effects on their memorable experiences. Finally, the results demonstrate that tourists’ memorable experiences significantly influence their satisfaction and intention to revisit smart destinations. This study expands existing literature by exploring a new model for enhancing memorable experiences and revisit intention using STTs, and presents findings applicable to the city of Tehran, while adopting a model which can be replicated in other geographies looking at better understanding its tourism landscape. Finally, the results in this study can be helpful for both researchers and policy makers in their quest to rejuvenate local post-pandemic economies via tourism measures

Evaluating the evolution of ECMWF precipitation products using observational data for Iran:from ERA40 to ERA5

Abstract European Center for Medium-Range Weather Forecasts Reanalysis (ERA), one of the most widely used precipitation products, has evolved from ERA-40 to ERA-20CM, ERA-20C, ERA-Interim, and ERA5. Studies evaluating the performance of individual ERA products cannot adequately assess the evolution of the products. We compared the performance of all ERA precipitation products at daily, monthly, and annual data (1980–2018) using more than 2100 Iran precipitation gauges. Results indicated that ERA-40 performed worst, followed by ERA-20CM, which showed only minor improvements over ERA-40. ERA-20C considerably outperformed its predecessors, benefiting from the assimilation of observational data. Although several previous studies have reported full superiority of ERA5 over ERA-Interim, our results revealed several shortcomings in ERA5 compared with the ERA-Interim estimates. Both ERA-Interim and ERA5 performed best overall, with ERA-Interim showing better statistical and categorical skill scores, and ERA5 performing better in estimating extreme precipitations. These results suggest that the accuracy of ERA precipitation products has improved from ERA-40 to ERA-Interim, but not consistently from ERA-Interim to ERA5. This study employed a grid-grid comparison approach by first creating a gridded reference data set through the spatial aggregation of point source observations, however, the results from a point-grid approach showed no change in the overall ranking of products (despite the slight changes in the error index values). These findings are useful for model development at a global scale and for hydrological applications in Iran

Thigh-length compression stockings and DVT after stroke

Controversy exists as to whether neoadjuvant chemotherapy improves survival in patients with invasive bladder cancer, despite randomised controlled trials of more than 3000 patients. We undertook a systematic review and meta-analysis to assess the effect of such treatment on survival in patients with this disease

Azithromycin in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Background Azithromycin has been proposed as a treatment for COVID-19 on the basis of its immunomodulatory actions. We aimed to evaluate the safety and efficacy of azithromycin in patients admitted to hospital with COVID-19. Methods In this randomised, controlled, open-label, adaptive platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), several possible treatments were compared with usual care in patients admitted to hospital with COVID-19 in the UK. The trial is underway at 176 hospitals in the UK. Eligible and consenting patients were randomly allocated to either usual standard of care alone or usual standard of care plus azithromycin 500 mg once per day by mouth or intravenously for 10 days or until discharge (or allocation to one of the other RECOVERY treatment groups). Patients were assigned via web-based simple (unstratified) randomisation with allocation concealment and were twice as likely to be randomly assigned to usual care than to any of the active treatment groups. Participants and local study staff were not masked to the allocated treatment, but all others involved in the trial were masked to the outcome data during the trial. The primary outcome was 28-day all-cause mortality, assessed in the intention-to-treat population. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936. Findings Between April 7 and Nov 27, 2020, of 16 442 patients enrolled in the RECOVERY trial, 9433 (57%) were eligible and 7763 were included in the assessment of azithromycin. The mean age of these study participants was 65·3 years (SD 15·7) and approximately a third were women (2944 [38%] of 7763). 2582 patients were randomly allocated to receive azithromycin and 5181 patients were randomly allocated to usual care alone. Overall, 561 (22%) patients allocated to azithromycin and 1162 (22%) patients allocated to usual care died within 28 days (rate ratio 0·97, 95% CI 0·87–1·07; p=0·50). No significant difference was seen in duration of hospital stay (median 10 days [IQR 5 to >28] vs 11 days [5 to >28]) or the proportion of patients discharged from hospital alive within 28 days (rate ratio 1·04, 95% CI 0·98–1·10; p=0·19). Among those not on invasive mechanical ventilation at baseline, no significant difference was seen in the proportion meeting the composite endpoint of invasive mechanical ventilation or death (risk ratio 0·95, 95% CI 0·87–1·03; p=0·24). Interpretation In patients admitted to hospital with COVID-19, azithromycin did not improve survival or other prespecified clinical outcomes. Azithromycin use in patients admitted to hospital with COVID-19 should be restricted to patients in whom there is a clear antimicrobial indication. Funding UK Research and Innovation (Medical Research Council) and National Institute of Health Research