Single-crystalline Si-CdSe biaxial p-n heterostructure nanowires (NWs) have been grown via chemical vapor deposition method and characterized. The Si and CdSe subnanowires have diameters of about 30 and 60 nm, respectively, and grow along the [(2) over bar1 (1) over bar] and [0001] directions, respectively. Room-temperature photoluminescence (PL), Raman-scattering, and electrical transport measurements were made on single Si-CdSe biaxial heterostructure NWs. Strong CdSe band-edge emission peaked around 710 nm together with a broad emission centered at 600 nm is observed in the PL spectra. Intense sharp longitudinal optical phonon modes from both CdSe and Si are observed in Raman-scattering spectra. The resistivities, carrier concentrations, and carrier mobilities of single CdSe NW and Si subnanowire are estimated. A good rectification characteristic is observed in the I-V curve of Si-CdSe biaxial NW, which confirms that the Si-CdSe biaxial NW is a p-n heterostructure.
In China, traffic policemen have to stand for several hours a day at the road intersections with high vehicle flows. To assess their exposure to airborne carcinogenic polycyclic aromatic hydrocarbons (PAHs) during their working time, a preliminary study was conducted to measure the personal exposure level to PAHs. And a probabilistic incremental lifetime cancer risk (ILCR) model together with the benzo[a]pyrene (BaP) toxic equivalents (BaPeq) method was used to conduct health risk assessment. Personal exposure monitors (PEM) were carried by traffic policemen to collect PM10 samples during their daily work in Tianjin, China. Meanwhile, PM100 samples were collected at the roadsides and on campus of Nankai University as comparison. PAHs species were quantitatively analyzed by GC/MS. Experimental results showed that the concentrations of total PAHs, BaP and BaPeq were much higher at the road intersections (867.5, 26.2, 82.4 ng m−3), where the traffic policemen stand during their work time, than those at the roadsides (46.6, 1.5, 5.7 ng m−3), and on campus (19.5, 0.7, 2.4 ng m−3). According to the risk assessment results, the occupational risk falls within the range from 10−6 to 10−3. On the basis of sensitivity analysis results, further research should be directed to give better characterization of the yearly concentration distribution of PAHs and the cancer slope factor (CSF) of BaP in order to improve the accuracy of the health risk assessment.
4He (i.e., α particle) and 6He emissions from possible molecular states in beryllium and carbon isotopes have been investigated using a mean-field-type cluster potential. Calculations can reasonably describe the α-decay widths of studied states in beryllium and carbon isotopes, and also 20Ne, compared with experiments. For the nucleus 10Be, we discussed α-decay widths with different shapes or different decay modes, in order to understand the very different decay widths of two excited states. The widths of 6He decays from 12Be and α decays from 13,14C are predicted, which could be useful for future experiments.