Optimizing the ratio of the rates for charge separation (CS) over charge recombination (CR) is crucial to create long-lived charge-separated states. Mastering the factors that govern the electron transfer (ET) rates is essential when trying to achieve molecular-scale electronics, artificial photosynthesis, and also for the further development of solar cells. Much work has been put into the question of how the donor-acceptor distances and donor-bridge energy gaps affect the electronic coupling, V(DA), and thus the rates of ET. We present here a unique comparison on how these factors differently influence the rates for CS and CR in a porphyrin-based donor-bridge-acceptor model system. Our system contains three series, each of which focuses on a separate charge-transfer rate-determining factor, the donor-acceptor distance, the donor-bridge energy gap, and last, the influence of the electron acceptor on the rate for charge transfer. In these three series both CS and CR are governed by superexchange interactions which make a CR/CS comparative study ideal. We show here that the exponential distance dependence increases slightly for CR compared to that for CS as a result of the increased tunneling barrier height for this reaction, in accordance with the McConnell superexchange model. We also show that the dependence on the tunneling barrier height is different for CS and CR. This difference is highly dependent on the electron acceptor and thus cannot solely be explained by the differences in the frontier orbitals of the electron donor in these porphyrin systems.

We report the first measurement of the parity-violating asymmetry in elastic electron scattering from the proton. The asymmetry depends on the neutral weak magnetic form factor of the proton which contains new information on the contribution of strange quark-antiquark pairs to the magnetic moment of the proton. We obtain the value G Z M 0.34 6 0.09 6 0.04 6 0.05 n.m. at Q 2 0.1 ͑GeV͞c͒ 2 . [S0031-9007(97)03181-5] PACS numbers: 13.60. Fz, 11.30.Er, 13.40.Gp, 14.20.Dh The measurement of strange quark-antiquark (ss) effects in the nucleon offers a unique window to study the effects of the qq "sea" at low momentum transfers. This information is an important clue to the dynamical effects of QCD that are responsible for form factors in the nonperturbative regime, and may lead to new insight into the origins of these effects.It has been shown [1] that the neutral weak current can be used to determine the ss contributions to nucleon form factors. The magnetic moment is one important nucleon property that can be studied in this fashion. The neutral weak magnetic form factor of the proton can be measured in parity-violating electron scattering, [2], thus providing information on the ss content of the nucleon's magnetic moment. In this Letter, we report the first such measurement and obtain the first direct experimental data relevant to determination of the strange magnetic moment of the proton.To lowest order (tree-level), the neutral weak magnetic form factor of the proton G Z M can be related to nucleon electromagnetic form factors and a contribution from strange quarks: As mentioned above, the quantity G Z M for the proton can be measured via elastic parity-violating electron scattering at backward angles [2]. The difference in cross sections for right and left handed incident electrons arises from interference of the electromagnetic and neutral weak amplitudes, and so contains products of electromagnetic and neutral weak form factors. The expression for elastic scattering from the proton is given by

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Virtual reality (VR) has become a popular approach to study human behavior in fire. The present position paper analyses Strengths, Weaknesses, Opportunities, and Threats (SWOT) of VR as a research tool for human behavior in fire. Virtual environments provide a maximum of experimental control, are easy to replicate, have relatively high ecological validity, and allow safe study of occupant behavior in scenarios that otherwise would be too dangerous. Lower ecological validity compared to field studies, ergonomic aspects, and technical limitations are the main weaknesses of the method. Increasingly realistic simulations and other technological advances provide new opportunities for this relatively young method. In this position paper, we argue that VR is a promising complementary laboratory tool in the quest to understand human behavior in fire and to improve fire safety.

A review of literature related to fire evacuation in high-rise buildings was carried out with the following objectives, (1) to identify the key behavioural factors affecting the performance of people during a fire in a high-rise building, the singularities associated to this type of buildings and areas of future research; (2) to review the procedures and strategies currently adopted in high-rise buildings; (3) to review and analyse the capabilities of evacuation models by reviewing their current characteristics and applications in the context of high-rise building evacuations. The review included both findings on human behaviour in high-rise buildings and modelling techniques and tools. Different categories of building use were taken into account, namely office buildings, residential buildings and health care facilities. The individual or combined use of different egress components was analysed. Egress components include the use of stairs, elevators as well as alternative means of escape (e.g., sky-bridges, helicopters, etc.). The effectiveness of the egress components is strongly affected by the building use and the population involved. The review shows that evacuation models can be effectively employed to study relocation strategies and safety issues associated with high-rise buildings. The suitability of egress models for high-rise building evacuations is associated with their flexibility in representing different egress components and complex behavioural processes. The review highlights that there is not a definitive model to be used but that the predictive capabilities of evacuation modelling techniques would be enhanced if more than one model is employed to study different egress aspects. Future research and model developments should focus on the study of the impact of staff actions, group dynamics and people with disabilities. Given the increasing height of buildings and the gradual reduction in the physical abilities of the population, the effects of fatigue on evacuation need further studies.

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Summary This article explores how egress drills—specifically those related to fire incidents—are currently used, their impact on safety levels, and the insights gained from them. It is suggested that neither the merits of egress drills are well understood, nor the impact on egress performance well characterized. In addition, the manner in which they are conducted varies both between and within regulatory jurisdictions. By investigating their strengths and limitations, this article suggests opportunities for their enhancement possibly through the use of other egress models to support and expand upon the benefits provided. It is by no means suggested that drills are not important to evacuation safety—only that their inconsistent use and the interpretation of the results produced may mean we (as researchers, practitioners, regulators, and stakeholders) are not getting the maximum benefit out of this important tool. © 2017 Her Majesty the Queen in Right of Canada. Fire and Materials StartCopText© 2017 John Wiley & Sons, Ltd.

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