Coking-Resistant Sub-Nano Dehydrogenation Catalysts: PtnSnx/SiO2 (n=4, 7)

We present a combined experimental/theoretical study of Pt$_n$/SiO$_2$ and Pt$_n$Sn$_x$/SiO$_2$ (n = 4, 7) model catalysts for the endothermic dehydrogenation of hydrocarbons, using the ethylene intermediate as a model reactant. Supported pure Ptn clusters are found to be highly active toward dehydrogenation of C2D4, quickly deactivating due to a combination of carbon deposition and sintering, resulting in loss of accessible Pt sites. Addition of Sn to Ptn clusters results in the complete suppression of C2D4 dehydrogenation and carbon deposition, and also stabilizes the clusters against thermal sintering. Theory shows that both systems have thermal access to a multitude of cluster structures and adsorbate configurations that form a statistical ensemble. While Pt4/SiO2 clusters bind ethylene in both di-sigma and pi-bonded configurations, Pt$_4$Sn$_3$/SiO$_2$ binds C2H4 only in the pi-mode, with di-sigma bonding suppressed by a combination of electronic and geometric features of the PtSn clusters. Dehydrogenation reaction profiles on the accessible cluster isomers were calculated using the climbing image nudged elastic band (CI-NEB) method

Evaluation of Causes of Death in East of Iran during 2004-2010

Background: Analysis of the leading causes of death in a community and comparing it with other communities is crucial for planning public health policy. The aim of this study was to determine mortality statistics in South Khorasan Province of Iran by using causes of death data which are classified based on the 10th revision of the International Classification of Diseases (ICD10).Methods: In this cross-sectional study, data related to 20281 deaths for the period of 2004 to 2010 which were under the coverage of Birjand University of Medical Sciences were used. These data were collected by the office of statistical system of mortality (Death Registry) and the causes of deaths were classified based on ICD10. The obtained data was analyzed statistically with Pearson's Chi-square (χ2) test, t test and ANOVA in order to find out the pattern of mortality trend in South Khorasan Province.Results: Cardiovascular diseases (CVD) were the leading cause of death (29.8%) with the mean age of 72.6±15.5 in all registered deaths. Moreover, ischemic heart disease (44.87%) and cerebrovascular disease (25.67%) were the most common causes in CVD group, respectively. The second leading cause was unintentional injuries (12.9%) which are mostly due to road traffic accidents. The mean age in this group was 36.8±24. Cancers ranked the 3rd place during the period of study with the mean age of 64.86±18.26. The most frequent cancers are related to stomach (15.3%) followed by liver and biliary system (11.4%), lungs and bronchus (9.5%).Conclusion: Three leading causes of death were cardiovascular diseases, unintentional injuries and cancers which may be prevented by changing life style, diet and reducing risk factors like smoking, obesity and stress

Sn-modification of Pt7/alumina model catalysts: Suppression of carbon deposition and enhanced thermal stability.

An atomic layer deposition process is used to modify size-selected Pt7/alumina model catalysts by Sn addition, both before and after Pt7 cluster deposition. Surface science methods are used to probe the effects of Sn-modification on the electronic properties, reactivity, and morphology of the clusters. Sn addition, either before or after cluster deposition, is found to strongly affect the binding properties of a model alkene, ethylene, changing the number and type of binding sites, and suppressing decomposition leading to carbon deposition and poisoning of the catalyst. Density functional theory on a model system, Pt4Sn3/alumina, shows that the Sn and Pt atoms are mixed, forming alloy clusters with substantial electron transfer from Sn to Pt. The presence of Sn also makes all the thermally accessible structures closed shell, such that ethylene binds only by π-bonding to a single Pt atom. The Sn-modified catalysts are quite stable in repeated ethylene temperature programmed reaction experiments, suggesting that the presence of Sn also reduces the tendency of the sub-nano-clusters to undergo thermal sintering

Laser interactions with bundle fiber structures

Laser damages of materials are in research focus during the last decade. These terms can be understood as useful in the treatment of materials or in theoretical modeling of interactions of laser beams with the material. Also, they can be destructive when it comes to high power density where the nonlinear effects are present, too. In addition to the theory, many detailed experimental work is required for new optical components applications. The experiments with Nd 3+ : YAG laser (1.064 µm) with defined working regime and power densities and specifically developed optical fiber bundles are the subject of this paper. The fibers are developed in laboratory conditions for specific purposes. Also, commercial optical fiber bundle for dental use are presented and discussed as comparison with the same laser types

Influence of nuclear radiation and laser beams on optical fibers and components

The influence of nuclear radiation and particles has been the object of investigation for a long time. For new materials and systems the research should be continued. Human activities in various environments, including space, call for more detailed research. The role of fibers in contemporary communications, medicine, and industry increases. Fibers, their connections and fused optics components have one type of tasks - the transmission of information and power. The other type of tasks is reserved for fiber lasers: quantum generators and amplifiers. The third type of tasks is for fiber sensors, including high energy nuclear physics. In this paper we present some chosen topics in the mentioned areas as well as our experiments with nuclear radiation and laser beams to fiber and bulk materials of various nature (glass, polymer, metallic, etc.)