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A study was done on the chemisorption and thermal decomposition of methylamine on Ru(001) surface. Results show that molecular adsorption of methylamine occurs via lone pair donation of the nitrogen atom and its desorption occurs reversibly from a saturated first layer in the temperature range of 200 to 340 K. Thermal decomposition of irreversibly adsorbed methylamine produces H2,N2 and NH3.

The initial probabilities of precursor-mediated, dissociative chemisorption of the saturated hydrocarbons 13C-labeled ethane, propane, isobutane, n-butane, and neopentane on the close-packed Ir(111) surface have been measured. The selective activation of primary (1°), secondary (2°), and tertiary (3°) C–H bonds has been quantified by examining the reactivities of the selectively deuterated isotopomers of propane, C3H8, CH3CD2CH3, and C3D8, and of isobutane, (CH3)3CH, (CH3)3CD, and (CD3)3CH. With respect to the bottom of the physically adsorbed well for each hydrocarbon, the apparent C–H bond activation energies have been found to be 10.4±0.3 kcal/mol (ethane), 11.4±0.3 kcal/mol (propane), 11.5±0.3 kcal/mol (n-butane), 11.3±0.3 kcal/mol (i-butane), and 11.3±0.3 kcal/mol (neopentane). For all the alkanes examined, the ratios of the preexponential factors of the rate coefficients of reaction and desorption are 1×10-2. The C–D bond activation energies are higher than the corresponding C–H bond activation energies by 480 cal/mol (ethane), 630 cal/mol (propane), and 660 cal/mol (i-butane). By analyzing the primary kinetic isotope effects for the selectively deuterated isotopomers of propane and isobutane, the 2° C–H bond activation energy is found to be 310±160 cal/mol less than the 1° C–H bond activation energy on this surface, and similarly, 3° C–H bond cleavage is less by 80±70 cal/mol. The quantification of the branching ratios within the C–H bond activation channel for propane and isobutane on this surface shows that the formation of 1°-alkyl intermediates is, in general, favored over the formation of either 2°- or 3°-alkyl intermediates. This result is a direct consequence of the disproportionate number of 1° C–H bonds relative to the number of 2° and 3° C–H bonds in these alkanes. These... [ABSTRACT FROM AUTHOR]

The C–H bond activation of carbon-13 labeled ethane 1,2-di-13C–C2H6 at defect sites on an Ir(111) single-crystalline surface, cut and polished to 0.70°±0.15° of the (111) direction, has been determined quantitatively. These results have been obtained from a kinetic model accounting for diffusion from sites on the less reactive terraces to step edges on the surface, combined with the appropriate trapping-mediated description of the overall rate processes operative at the defects. The activation energy for reaction at the defect sites was found to be 4500±1500 cal/mol, which is ∼6000 cal/mol less than the reaction barrier at the terrace sites. The preexponential factor of the reaction rate coefficient at the defect sites was found to lie between 5×1011 and 1012 s-1, which is five to ten times greater than the preexponential factor of the reaction rate coefficient at the close-packed (111) terrace sites that dominate the surface. The net effect is that at room temperature, the defect activity is approximately four and one-half orders of magnitude greater than that of the close-packed terrace sites. [ABSTRACT FROM AUTHOR]

Introduction and Purpose: There was a 1200% increase in the prevalence rates of musculoskeletal disorders (MSDs) in the United States from 1982 to 1994. This epidemic was recognized and addressed with extensive research and the implementation of many ergonomic safety management programs. The interventions from government agencies, safety management personnel, and health service providers resulted in a 30% decrease in MSDs for workers in all industries from 1995 through 2000. However, MSD-related injuries for knowledge (ie, "office") workers plateaued during the same period at 20 out of 26 new cases per 10.000 workers per year, accounting for nearly 80% of the MSD-related injuries of all workers in the United States. This feasibility study was undertaken to assess and characterize the prevalence of MSDs of knowledge workers and to correlate their complaints with the conditions of their ergonomic work environments. This study is the first of a series with the ultimate programmatic objective being to study the effectiveness of ergonomic intervention as an adjunct to chiropractic care for the knowledge worker. Materials and Methods: Specialized assessment instruments were developed to characterize the ergonomic work environments and presenting complaints of a representative population of knowledge workers (n = 20) at Life Chiropractic College West. Statistical correlations between the human factors, exposure risk variables, and the volunteers' self-reported complaints have been examined with SPSS statistical software, Results: Sixteen of 20 participants (80%) reported neck pain in combination with either low back or extremity pain in the wrist or forearm. The observed ergonomic risk exposures and the root causation data from the assessments reveal a probable association with the reported neck, wrist, and back symptomatology. The principal causal factors indicated to correlate with these symptoms were (1) extended functional reach distances, (2) poor postural positioning at workstations, (3) prolonged sitting, and (4) repetitive tasking. Discussion and Conclusion: There is strong evidence from both a comprehensive literature search and the results of this work that a clinically controlled study is necessary to determine the efficacy and effectiveness of ergonomics as an adjunct protocol in the chiropractic care of knowledge workers. [ABSTRACT FROM AUTHOR]