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Richard H. Perry Thomas J. Cahill III Jennifer L. Roizen Justin Du Bois Richard N. Zare 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(45):18295-18299
We have applied an ambient ionization technique, desorption electrospray ionization MS, to identify transient reactive species of an archetypal C–H amination reaction catalyzed by a dirhodium tetracarboxylate complex. Using this analytical method, we have detected previously proposed short-lived reaction intermediates, including two nitrenoid complexes that differ in oxidation state. Our findings suggest that an Rh-nitrene oxidant can react with hydrocarbon substrates through a hydrogen atom abstraction pathway and raise the intriguing possibility that two catalytic C–H amination pathways may be operative in a typical bulk solution reaction. As highlighted by these results, desorption electrospray ionization MS should have broad applicability for the mechanistic study of catalytic processes. 相似文献
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Background
Despite the inevitable growing rate of nurse turnover worldwide and its consequences, limited empirical data has been published in Indonesia. This study aims to describe the nurse turnover pattern at private hospitals, its causes and consequences as perceived by the hospitals’ managers.Methods
A survey method was used to obtain secondary and primary data from five private general hospitals in three administrative regions in East Java, Indonesia. The data of nurse turnover and demographic characteristics were collected. Mann Whitney test and relative risk analysis was performed to explore the role of nurse characteristics on nurses’ decision to leave their job. To explore the causes and consequences of nurse turnover, an online survey was conducted to twelve hospital managers. The data was then classified based on similar themes.Results
The data show that nurse turnover is between 12 and 34%. Being up to thirty years old, single, and having worked in the hospital up to three years significantly increase the risk of turnover. Personal reasons, external attractions and unsuitable working conditions are the three common nurse turnover reasons revealed by hospital managers. Hospital managers admitted that nurse turnover disturbs hospital operations, further impacting the hospital’s revenue and costs.Conclusions
The nurse turnover is higher than the acceptable level which is significantly predicted by age, marital status and job tenure. Further research is needed to develop nurse retention strategy in their early years of employment, based on the nurse’s point of view.5.
Some limited models have been suggested to determine the conductivity of polymer carbon nanotube (CNT) nanocomposites (PCNTs). However, earlier models (e.g., the Kovacs model) cannot properly consider the roles of the interphase regions or tunneling properties on the percolation threshold and subsequent conductivity of PCNTs. In this paper, the Kovacs model is further developed by assuming that the CNT, interphase, and tunneling regions are separate phases. Also, some simple equations are provided to calculate the percolation threshold as well as the volume fractions and resistances of the CNT, interphase, and tunneling regions in conductive networks. The experimental conductivity results for several samples are compared with the predictions of the developed model. In addition, the calculations of the developed model at different parameter levels are explained and justified. The conductivity calculations show good agreement with the experimental data. Moreover, the developed model reasonably explains the roles of the different parameters on the conductivity. For example, long, thin, and straight CNTs efficiently improve the conductivity because they form large networks in the nanocomposites. Additionally, a thick interphase enlarges the conductive networks, resulting in a desirable conductivity. The conductivity of PCNTs only depends on the tunneling resistance; this is the case because the poor resistance/significant conductivity of the CNT and interphase regions do not influence the conductivity. The developed equations can replace conventional approaches for predicting the conductivity of nanocomposites.Some limited models have been suggested to determine the conductivity of polymer carbon nanotube (CNT) nanocomposites (PCNTs). 相似文献
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Hamid Badrian Amin Davoudi Meysam Molazem Mohammad Hossein Zare 《Journal of Indian Prosthodontic Society》2015,15(3):263-267
Background:
Dentistry equipment are exposed to different types of pathogenic microorganisms. The aim of this study was to investigate the effect of spraying three different types of disinfectants on condensational silicones after 5 and 10 min.Materials and Methods:
Totally, 66 circular samples of condensational silicone impression materials of 1 cm diameter and 2 mm thickness were contaminated by Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans fungus. Except for control samples, all of them were disinfected with sodium hypochlorite (NaOCl) 0.525%, Deconex and Epimax by spraying method. Afterward, they kept in plastic bags with humid rolled cotton for 5 and 10 min. In order to isolate microbiotas, the samples were immersed in 2% trypsin for 1 h and diluted with normal saline in a portion of 1, 1/2, and 1/4. The trypsin suspensions were transferred to culture plates for incubation and colony-forming unit assay. The data were analyzed by Mann–Whitney test and SPSS software version 16 at a significant level of 0.05.Results:
There was a meaningful difference between disinfection effects of Epimax-Deconex for all mentioned microorganisms after 5 min (P = 0.034), and between disinfection effects of NaOCl 0.525%-Epimax for S. aureus (P = 0.043) and P. aeruginosa (P = 0.046) after 5 min. Furthermore, there was a meaningful difference between disinfection effects of Epimax-Deconex (P = 0.034) and NaOCl 0.525%-Epimax (P = 0.034) for P. aeruginosa after 10 min.Conclusion:
Condensational silicone can be effectively disinfected by spraying tested three disinfecting agents. More specifically, Deconex showed the best results compared to the other agents.Key Words: Condensational silicone, disinfection, impression materials, spray 相似文献8.
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