Effects of Core Size and Shell Thickness on Luminescence Dynamics of Wurtzite CdSe/CdS Core/Shell Nanocrystals

Colloidal CdSe nanocrystals (NCs), whose size is 2.8, 3.8, and 4.9 nm, respectively, were successively overcoated with CdS monolayers (MLs). The X-ray diffraction patterns indicated that the stress in the wurtzite CdSe core was increased with the epitaxial growth of CdS shell, and the CdSe lattice contraction, which was sensitive to core size, did not release with the CdS shell toward 5 MLs. The effects of the CdSe core size and the CdS shell thickness on the temperature-dependent photoluminescence (PL) lifetime were investigated. The PL lifetime undulation with temperature is indicative of the spatial distribution of trap states, and the strong interplay between intrinsic excitons and surface traps can be activated even in the case of the NCs with 5 ML CdS shell

Characteristics of 1226 Alcohol-Positive Drivers Involved in Nonfatal Traffic Crashes in Shanghai, China

<div><p><b>Objective:</b> The purpose of our study was to better characterize and evaluate drunk driving for governmental reference in order to further reduce alcohol-impaired driving.</p><p><b>Method:</b> This article reports the characteristics of 1226 alcohol-positive drivers with blood alcohol concentrations (BACs) at or over the legal limit of 0.20 mg/mL involved in nonfatal traffic accidents in Shanghai, China, from 2008 to 2011. The mean BAC, age, and gender of these drivers are discussed as well as the vehicle types and times of day when the crashes occurred.</p><p><b>Results:</b> The mean BAC was 1.41 mg/mL and the mean age was 38 years old, and the vast majority of drivers were male (96.9%). The mean BAC of male drivers (1.42 mg/mL) was higher than that of female drivers (1.20 mg/mL). The mean age of male drivers (38) was also higher than that of female drivers (33). Distributions of vehicle types involved were studied. Cars had the highest percentage of occurrences (56.4%), followed by motorcycles (32.8%), electric bicycles (6.8%), trucks (1.5%), and bicycles (0.8%). It was found that these alcohol-related traffic crashes most often occurred between 7:00 p.m. and 10:59 p.m., representing 48.1 percent (<i>n</i> = 590) of the 1226 cases. Single-vehicle crashes were overrepresented (70.3%) in all cases. The mean BAC in multivehicle crashes (1.69 mg/mL) was higher than that in single-vehicle crashes (1.30 mg/mL).</p><p><b>Conclusions:</b> The results indicated a notable need for more governmental attention that would prevent accidents caused by driving under the influence of alcohol.</p></div