Kinetics and mechanism of formic acid decomposition on Ru(001)

The steady-state rate of decomposition of formic acid on Ru(001) has been measured as a function of surface temperature, parametric in the pressure of formic acid. The products of the decomposition reaction are C0_2, H_2, CO, and H_2)0, i.e., both dehydrogenation and dehydration occur on Ru (001). A similar product distribution has been observed on Ni(110), Ni(100), Ru(100), Fe(100), and Ni(111) surfaces; whereas only dehydrogenation to C0_2 and H_2 occurs on the Cu(100), Cu(110), and Pt(111) surfaces. Only reversible adsorption and desorption of formic acid is observed on the less reactive Ag(110) surface at low temperatures, whereas the more reactive Mo(100) surface is oxidized by formic acid at low temperatures with the products of this reaction being H_2, CO, and H_(2)O (Ref. 10). We report here the confirmation of earlier observations of the occurrence of both dehydrogenation and dehydration of formic acid on Ru(001), and more importantly, we provide a detailed mechanistic description of the steady-state decomposition reaction on this surface in terms of elementary steps

Cosmic ray feedback in the FIRE simulations: constraining cosmic ray propagation with GeV gamma ray emission

We present the implementation and the first results of cosmic ray (CR) feedback in the Feedback In Realistic Environments (FIRE) simulations. We investigate CR feedback in non-cosmological simulations of dwarf, sub-$L\star$ starburst, and $L\star$ galaxies with different propagation models, including advection, isotropic and anisotropic diffusion, and streaming along field lines with different transport coefficients. We simulate CR diffusion and streaming simultaneously in galaxies with high resolution, using a two moment method. We forward-model and compare to observations of $\gamma$-ray emission from nearby and starburst galaxies. We reproduce the $\gamma$-ray observations of dwarf and $L\star$ galaxies with constant isotropic diffusion coefficient $\kappa \sim 3\times 10^{29}\,{\rm cm^{2}\,s^{-1}}$. Advection-only and streaming-only models produce order-of-magnitude too large $\gamma$-ray luminosities in dwarf and $L\star$ galaxies. We show that in models that match the $\gamma$-ray observations, most CRs escape low-gas-density galaxies (e.g.\ dwarfs) before significant collisional losses, while starburst galaxies are CR proton calorimeters. While adiabatic losses can be significant, they occur only after CRs escape galaxies, so they are only of secondary importance for $\gamma$-ray emissivities. Models where CRs are ``trapped'' in the star-forming disk have lower star formation efficiency, but these models are ruled out by $\gamma$-ray observations. For models with constant $\kappa$ that match the $\gamma$-ray observations, CRs form extended halos with scale heights of several kpc to several tens of kpc.Comment: 31 pages, 26 figures, accepted for publication in MNRA

Urinary 1-hydroxypyrene and malondialdehyde in male workers in Chinese restaurants

OBJECTIVES: To assess internal dose and oxidative stress in male restaurant workers exposed to polycyclic aromatic hydrocarbons (PAHs) from cooking oil fumes (COFs) in Chinese restaurants. METHODS: The study participants included 288 male restaurant workers (171 kitchen and 117 service staff) in Chinese restaurants in Taiwan. Airborne particulate PAHs were measured over 12 h on each of two consecutive work days and then identified using high performance liquid chromatography. Urinary 1- hydroxypyrene (1-OHP) measurements were used to indicate COF exposure, and urinary malondialdehyde (MDA) was adopted as an oxidative stress marker. Multiple regression models were used to assess the relationship between MDA and 1-OHP levels after adjusting for key personal covariates. RESULTS: Summed particulate PAH levels in kitchens (median 23.9 ng/m(3)) were significantly higher than those in dining areas (median 4.9 ng/m(3)). For non-smoking kitchen staff, mean MDA and 1-OHP levels were 344.2 (SD 243.7) and 6.0 (SD 8.0) mumol/mol creatinine, respectively. These levels were significantly higher than those for non-smoking service staff, which were 244.2 (SD 164.4) and 2.4 (SD 4.3) mumol/mol creatinine, respectively. Urinary 1-OHP levels were significantly associated with work in kitchens ( p<0.05). Furthermore, urinary MDA levels were significantly associated with urinary 1-OHP levels (p<0.001) and working hours per day (p<0.05). CONCLUSIONS: These findings indicate that urinary 1-OHP and MDA levels reflect occupational exposure to PAHs from COFs and oxidative stress in workers in Chinese restaurants

CMB Constraint on Radion Evolution in the Brane World Scenario

In many versions of brane model, the modulus field of extra dimensions, the radion, could have cosmological evolution, which induces variation of the Higgs vacuum expectation value, , resulting in cosmological variation of the electron mass $m_e$. The formation of Cosmic Microwave Background (CMB) anisotropies is thus affected, causing changes both in the peaks positions and amplitudes in the CMB power spectra. Using the three-year Wilkinson Microwave Anisotropies Probe (WMAP) CMB data, with the Hubble parameter $H_0$ fixed to be the Hubble Space Telescope (HST) result 72 km s$^{-1}$ Mpc$^{-1}$, we obtain a constraint on $\rho$, the ratio of the value of at CMB recombination to its present value, to be [0.97, 1.02].Comment: 7 pages, 6 figures, minor changes of format to conform with PRD forma

Neural processes of proactive and reactive controls modulated by motor-skill experiences

This study investigated the experience of open and closed motor skills on modulating proactive and reactive control processes in task switching. Fifty-four participants who were open-skilled