For telluride compounds, the presence of electrically active contaminants in the grown crystals is one of the critical factors that can severely limit the ensuing device performance. In order to minimize contamination from both precursor material handling and environmental sources during the compounding operation, a fully integrated traveling heater method (THM) CdTe synthesis process was developed. Based on glow discharge mass spectroscopy (GDMS) analysis, the average total impurity content, excluding carbon, nitrogen, and oxygen, is in the order of 100 PPB atomic, with zinc being the major contaminant and accounting for more than 40 pct of this value.
The specific health hazards associated with exposure to asbestos are defined in terms of definitions of the asbestiform minerals—definitions that distinguish between acicular fragments and true fibers and that relate to the respirability of airborne particulates. The respiratory hazards include asbestosis, mesothelioma, and cancer. Estimates of cancer incidence—ranging from those of Joseph Califano, U.S. Secretary of Health, Education, and Welfare, to those of Doll and Peto—are evaluated critically. Bronchogenic cancer incidence is reviewed and discussed. The role of synergism with cigarette smoking in disease is discussed. The incidence of mesothelioma in relation to human epidemiology, the numerous other substances that cause mesothelioma in animals, the inactivity of anthophyllite asbestos, an epidemic in Turkey, and experience in the mines of Quebec Province, Canada, are examined. Cancers of the gastrointestinal tract associated with the ingestion of asbestos from drinking water or from lung clearance mechanisms are examined critically. The dearth of reliable human epidemiology and extensive animal studies are considered. Dose-response relationships associated with asbestosis are presented, and the threshold exposure limit determined for chrysotile miners is mentioned. One cohort of some 250 men occupationally exposed to moderately controlled airborne chrysotile concentrations for 25 years is evaluated. Dose-response relationships associated with cancer are discussed. The single-fiber hypothesis is criticized. Background incidence of asbestosis in persons without occupational exposure is discussed, and intrinsic lung defense mechanisms are touched upon. Hazardous exposure conditions for asbestos are defined. The epidemiology of the asbestos miners of Quebec Province is summarized, and recent experience is considered. The British criterion of acceptable risk, based on a 1% probability of developing the earliest clinical signs of asbestos-related disease, is discussed in light of society's willingness to accept reasonable risks and in light of the impracticality of zero risk. The effects of short intense exposure and their overwhelming effects on lung clearance mechanisms are discussed. The geographic distribution of asbestos-bearing geological formations is mentioned and hazards associated therewith are touched on. The hazardous entities, that is, those airborne particulates associated with asbestosis, are defined in terms of their dimensions in relation to respirability, deposition in the lungs, lung clearance mechanisms, tissue cell dimensions, and cytotoxicity. The origin of the 3:1 aspect ratio for fiber definition is delved into. Some animal studies on the effects of fiber dimensions are mentioned. The dimensions of the hazardous entities involved in cancer are presented. The dimensions of asbestos found as living tissue burden in humans are compared with the size distribution of airborne atmospheric particulates. Based upon all the foregoing considerations, definitions are developed of airborne fibrous particulates to be considered for monitoring purposes. The various definitions of asbestiform particles are mentioned. The respective limitations of electronic and optical microscopy are discussed. Definitions leading to efficient, reproducible hazard assessment are proposed. Finally, acceptable, realistic occupational exposures to asbestos are proposed, and demands for zero exposure are set against the perspective of the total quality of life.
Objective To compare the mortality rates of patients with claudication and de novo femoropopliteal lesions treated with and without paclitaxel coated devices (PCD). Background A recent meta-analysis, mostly including patients with claudication and de novo femoropopliteal lesions but also with recurrent stenoses and critical limb ischemia, has shown a significant excess mortality in patients treated with PCD. Methods Comparison of two historical cohorts of patients presenting with claudication and de novo femoropopliteal lesions treated with and without PCD between 2008 and 2018. Results After review of 5219 arteriograms in patients presenting with peripheral artery disease, 700 consecutive patients were included consisting in 72.6% of male (n = 508). Mean age was 68.1 ± 8.5 years. 45.7% of the patients (n = 320) had a treatment including a PCD. Mean femoropopliteal lesion length was 123 ± 91 mm including 44.6% of occlusions. Patients of the control group were censored at crossover to paclitaxel when applicable. Mortality rates at 1, 2 and 5 years were 4.6%, 7.5%, 19.4% and 1.6%, 6.2%, 16.6% in the non-PCD and PCD groups respectively. The relative risks of death when using PCD were 0.35 (p = 0.03), 0.83 (p = NS) and 0.86 (p = NS) at 1, 2 and 5 years respectively. Conclusion There was no excess mortality in patients with claudication and de novo femoropopliteal lesions treated with paclitaxel coated devices at 1, 2 and 5 years of follow-up in this cohort. The current study suggests that additional prospective randomized studies properly powered to study mortality are necessary.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.