Mechanistic Insight in the Ethane Dehydrogenation Reaction over Cr/Al2O3 Catalysts

A Cr/Al₂O₃ alkane dehydrogenation catalyst exhibits a maximum in ethylene yield during an ethane dehydrogenation cycle. Isotopic labelling experiments with monolabelled ¹³C-ethane and deuterium were used to elucidate whether the initial activity increase could be due to formation of an active, larger hydrocarbon intermediate on the surface. The results strongly indicate that this is not the case, and instead point to a traditional reaction cycle involving adsorption of ethane to form an ethyl species, followed by desorption of ethene and hydrogen. Transient kinetic data suggest that ethane adsorption is the rate-determining step of reaction.     

In Memory of Our Great Friend Professor Dong Haishan

In October 1987 an international symposium on propellants, explosives and pyrotechnics was arranged in Beijing at the Beijing Institute of Technology. I participated in that symposium and presented a paper entitled "Sensitivity Test Methods for approval of Explosives in Sweden".     

Changes in stress and subjective workload over time following a workload transition

Workload transitions present individuals with sudden changes in workload. These transitions may affect stress and coping behaviour. Two experiments were performed using a digit detection task that shifted between low and high workload levels to examine transition effects on performance, stress, and effort. The first experiment used a large magnitude transition and resulted in decreased estimates of task engagement and effort. Over time, the levels of subjective stress observed in the transitioned groups approached those of the non-transitioned control groups. The second experiment used a transition more moderate in magnitude. The results were similar to those from the first experiment except that the transition resulted in higher, sustained task engagement and effort. These findings indicate that over time, the perceived stress of transitioned individuals will approach those of non-transitioned individuals; however, the magnitude of the transition may influence individuals to either increase or decrease task-oriented, effortful coping.

Relevance to human factors/ergonomics theory

Previous research on the effect of workload transitions on experienced stress has produced conflicting results. Drawing upon transactional stress theory and motivational intensity theory, two experiments were conducted which resolve some of those conflicting findings. This research adds to our understanding of how workload transitions may affect individuals' experienced stress.     

Operationalising resilience for disaster medicine practitioners: capability development through training,simulation and reflection

Cognition, Technology & Work - Resilience has in recent decades been introduced as a term describing a new perspective within the domains of disaster management and safety management. Several...     

Multi-access Management in Heterogeneous Networks

Communication networks and mobile devices integrate an increasing number of access technologies. At the same time, new business roles emerge, which lead to new cooperation schemes between access providers providing different types of access connectivity. As a result, a variety of access technologies will be available for users at the same time. In this article we present an architecture and a framework capable of integrating different access systems into a multi-access system and selecting the best suited access for users. A utility-based approach is proposed for the evaluation of different access allocation choices, which is based on user and network policies, the performance of access bearers, and the availability of access resources. We present a general multi-access management framework, which integrates the different multi-access related functions: access detection, access evaluation and access selection, which can then lead to an access handover.

Self-diffusion in Zn4Sb3 from first-principles molecular dynamics

The Zn₄Sb₃ system is promising for thermoelectric applications due to its very low thermal conductivity coupled with a good power factor. Molecular dynamics calculations based on density functional theory were carried out for different stoichiometries of Zn₄Sb₃, corresponding to three situations: the composition Zn_3.6Sb₃ (actually Zn₆Sb₅ with only one Zn site occupied), a slightly higher Zn content Zn_3.8Sb₃ (with some of the Zn atoms in interstitial sites), and a slightly lower Zn content Zn_3.4Sb₃ (with some Zn vacancies). The diffusivity was calculated for different temperatures and the diffusion coefficient plotted in Arrhenius plots. The results compare well with experimental data, and point to a highly mobile Zn species with a very high diffusion coefficient prefactor.     

Effects of smoking on the urine excretion of oral 51Cr EDTA in ulcerative colitis

BACKGROUND: Smokers have a reduced risk and ex-smokers an increased risk of ulcerative colitis (UC). Stopping smoking often precedes onset and relapses. Smoking reduces the 24 hour urine excretion of oral chromium-51 labelled EDTA in healthy individuals. AIMS: To estimate the effects of smoking on the urine excretion of oral 51Cr EDTA in well characterised patients with UC. SUBJECTS: Sixteen smoking and 16 non-smoking patients with UC in remission were studied. The non-smokers had never smoked. Most were taking 5-aminosalicylic acid. No patient took steroids or immunosuppressants. The control group comprised 25 smoking healthy volunteers and 25 who had never smoked. The median cigarette consumption was equal in the patients and volunteers. METHODS: The 24 hour urine excretion of oral 51Cr EDTA was measured and the results were correlated with smoking habits, number of cigarettes, and disease extent. RESULTS: Patients with UC had significantly higher 24 hour urine recoveries than healthy controls (p = 0.04). This difference was more pronounced when patients who smoked were compared with healthy smokers (p = 0.005) No significant differences were found when comparing non-smoking patients with non-smoking controls or when comparing smoking and non-smoking patients. Urine recoveries did not correlate with number of cigarettes or disease extent. Smoking was more prevalent in patients with a more limited disease extent (p = 0.033). CONCLUSIONS: Effects of smoking on the urine excretion of 51Cr EDTA in health were abolished by the presence of UC. The protective effects of smoking in established UC are not due to a moderating effect of smoking on intestinal permeability.