Knowledge, attitudes, and practices around drinking and driving in Cambodia: 2010-2012.

OBJECTIVE: Road traffic injuries are a leading cause of disability and death in Cambodia. Economic development has long been associated with rapid increases in road traffic injuries and fatalities. Drink driving is of particular concern in Cambodia. In 2014, the percentage of fatal crashes involving alcohol rose to 17.5% (n = 381), representing a 34.9% (n = 253) increase from 2012. This study aims to illustrate current knowledge, attitudes and practices (KAP) around drinking and driving in three Cambodian provinces. METHODS: A roadside survey of randomly selected road users (aged 18 years and older) was conducted in Phnom Penh, Kandal, and Kampong Speu, Cambodia, between November 2010 and May 2012. Data were collected for five-day periods every 6 months. A survey was administered to assess prevailing knowledge, attitudes, and practices surrounding drink driving. RESULTS: A total of 1187 road users responded to the KAP survey, the majority (49.6%, n = 585) of whom were from Phnom Penh. Males accounted for 96.2% (n = 1142) of respondents; the majority (63.8%, n = 757) were aged 34 years and younger. Despite the belief that drinking and driving would increase the risk of a crash, a significant proportion of respondents (37.1%, n = 438) reported driving within 2 h of drinking alcohol at least once in the 30 days preceding the survey. This proportion was particularly high among males aged 25-34 years at 49.2% (n = 208). Of those who reported drinking and driving, 76.5% (n = 335) indicated they 'felt conscious enough' to drive at the time and 34.0% (n = 149) reported having 'no other available transportation options'. CONCLUSIONS: This study shows that, in general, drinking and driving remains a problem in Cambodia. A multi-pronged, coordinated approach is needed to effectively address this issue. Such an approach ought to include social marketing and public education campaigns, enhanced enforcement, and programs that either limit the number of drinks to drivers or those that provide alternatives to drinking and driving.

On describing the optoelectronic characteristics of poly(benzodithiophene-co-quinoxaline)-fullerene complexes: the influence of optimally tuned density functionals.

Here, we investigate the effects of both tuning the range-separation parameter of long-range corrected (LRC) density functionals and including dispersion corrections on describing the local optoelectronic properties of polymer-fullerene interfaces that are critical to the performance of polymer solar cells (PSCs). Focusing on recently studied (Chen, et al., Chem. Mater., 2012, 24, 4766-4772) PSC active layers derived from poly(benzodithiophene-co-quinoxaline) and substituted fullerene PC71BM, we compare the performance of global hybrid functionals (B3LYP and B3LYP-D) alongside two LRC functionals (ωB97X and ωB97X-D) and their optimally tuned (OT) analogs (OT-ωB97X and OT-ωB97X-D). Our results confirm that OT-LRC functionals generally improve the description of the optical properties of the individual materials with respect to experiment. For electron-donor (eD)-electron-acceptor (eA) complexes used to describe the local optoelectronic properties of the material interface, PC71BM is found to preferentially settle near the quinoxaline acceptor units on the copolymer backbone, regardless of the functional, though dispersion corrections have a strong influence on the intermolecular distances and, in turn, the nature of the excited states. All functionals yield very similar descriptions of the transition maxima for the complexes, i.e. predominant local excitations on the copolymer. Importantly, tuning the range-separation parameter of the LRC functional is shown to have a profound effect, as the OT functionals allow for the description of the charge transfer states of the eD-eA complexes, while the non-tuned LRC functionals predict only local intramolecular excitations. These results hold considerable importance for deriving the appropriate physical understanding of the interfacial structure-property-function relationships of PSCs.

Unification of trap-limited electron transport in semiconducting polymers.

Electron transport in semiconducting polymers is usually inferior to hole transport, which is ascribed to charge trapping on isolated defect sites situated within the energy bandgap. However, a general understanding of the origin of these omnipresent charge traps, as well as their energetic position, distribution and concentration, is lacking. Here we investigate electron transport in a wide range of semiconducting polymers by current-voltage measurements of single-carrier devices. We observe for this materials class that electron transport is limited by traps that exhibit a gaussian energy distribution in the bandgap. Remarkably, the electron-trap distribution is identical for all polymers considered: the number of traps amounts to 3 × 10(23) traps per m(3) centred at an energy of ~3.6 eV below the vacuum level, with a typical distribution width of ~0.1 eV. This indicates that the electron traps have a common origin that, we suggest, is most likely related to hydrated oxygen complexes. A consequence of this finding is that the trap-limited electron current can be predicted for any polymer.

Electronic properties of silole-based organic semiconductors.

We report on a detailed quantum-chemical study of the geometric structure and electronic properties of 2,5-bis(6(')-(2('),2(")-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole (PyPySPyPy) and 2,5-di- (3-biphenyl)-1,1-dimethyl-3,4-diphenylsilole (PPSPP). These molecular systems are attractive candidates for application as electron-transport materials in organic light-emitting devices. Density Functional Theory (DFT), time-dependent DFT, and correlated semiempirical (ZINDO/CIS) calculations are carried out in order to evaluate parameters determining electron-transport and optical characteristics. Experimental data show that PyPySPyPy possesses an electron-transport mobility that is significantly greater than PPSPP, while PPSPP has a significantly larger photoluminescence quantum yield; however, the theoretical results indicate that the two systems undergo similar geometric transformations upon reduction and have comparable molecular orbital structures and energies. This suggests that intermolecular interactions (solid-state packing, electronic coupling) play significant roles in the contrasting performance of these two molecular systems.