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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.04.012 Byline: C.A. Hibbitts (a), J. Szanyi (b) Keywords: Spectroscopy; Satellites; composition; Jupiter; satellites; Saturn; satellites Abstract: CO.sub.2 is known to adsorb onto clay and other minerals when a significant atmospheric pressure is present. We have found that CO.sub.2 can also adsorb onto some clays when the CO.sub.2 partial pressure is effectively zero under ultra-high vacuum (UHV) if cooled to the surface temperatures of the icy satellites of Jupiter and Saturn. The strength of adsorption and the spectral characteristics of the adsorbed CO.sub.2 infrared (IR) [nu].sub.3 absorption band near 4.25 [mu]m depend on the composition and temperature of the adsorbent. CO.sub.2 remains adsorbed onto the clay mineral montmorillonite for 10 s of min when exposed to a vacuum of [approximately equal to]1x10.sup.-8 Torr at [approximately equal to]125 K. CO.sub.2 does not adsorb onto serpentine, goethite, or palagonite under these conditions. A small amount may adsorb onto kaolinite. When heated above 150 K under vacuum, the CO.sub.2 desorbs from the montmorillonite within a few minutes. The [nu].sub.3 absorption band of CO.sub.2 adsorbed onto montmorillonite at 125 K is similar to that of the CO.sub.2 detected on the saturnian and Galilean satellites and is markedly different from CO.sub.2 adsorbed onto montmorillonite at room temperature. We infer the adsorption process is physisorption and postulate that this mechanism may explain the presence and spectral characteristics of the CO.sub.2 detected in the surfaces of these outer satellites. Author Affiliation: (a) Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd., Laurel, MD 20723, USA (b) Pacific Northwest National Laboratories, EMSL, Richland, WA 99352, USA Article History: Received 31 December 2005; Revised 14 March 2007

The structural and morphological features of Ba{[NO.sub.3]}[.sub.2] as well as the formation of BaO from Ba{[NO.sub.3]}[.sub.2] during the thermal release of [NO.sub.x] was investigated by choosing a model system of Ba{[NO.sub.3]}[.sub.2] supported on [alpha]-[Al.sub.2][O.sub.3]. At high temperature annealing, the single crystal Ba{[NO.sub.3]}[.sub.2] particles decompose to form multiple BaO particles, clustered together to maintain morphology of the parent Ba{[NO.sub.3]}[.sub.2].

The ever increasing demand to develop highly fuel efficient engines coincides with the need to minimize air pollution originating from the exhaust gases of internal combustion engines. Dramatically improved fuel efficiency can be achieved at air-to-fuel ratios much higher than stoichiometric. In the presence of oxygen in large excess, however, traditional three-way catalysts are unable to reduce NOx. Among the number of lean-NOx reduction technologies, selective catalytic reduction (SCR) of NOx by NH3 over Cu- and Fe-ion exchanged zeolite catalysts has been extensively studied over the past 30+ years. Despite the significant advances in developing a viable practical zeolite-based catalyst for lean NOx reduction, the insufficient hydrothermal stabilities of the zeolite structures considered cast doubts about their real-world applicability. During the past decade renewed interest in zeolite-based lean NOx reduction was spurred by the discovery of the very high activity of Cu–SSZ-13 (and the isostructural Cu–SAPO-34) in the NH3-SCR of NOx. These new, small-pore zeolite-based catalysts not only exhibited very high NOx conversion and N2 selectivity, but also exhibited exceptionally high hydrothermal stability at high temperatures. In this review we summarize the key discoveries of the past ∼5 years that led to the introduction of these catalysts into practical applications. This review first briefly discusses the structure and preparation of the CHA structure-based zeolite catalysts, and then summarizes the key learnings of the rather extensive (but not complete) characterisation work. Then we summarize the key findings of reaction kinetic studies, and provide some mechanistic details emerging from these investigations. At the end of the review we highlight some of the issues that still need to be addressed in automotive exhaust control catalysis. [ABSTRACT FROM AUTHOR]

Pulsing 15N18O onto an annealed 1% Mn16Ox/Ce16O2 catalyst resulted in very fast oxygen isotope exchange and 15N2 formation at 295 K. In the 1st 15N18O pulse, due to the presence of large number of surface oxygen defects, extensive 15N218O and 15N2 formations were observed. In subsequent pulses oxygen isotope exchange dominated as a result of highly labile oxygen in the oxide. [ABSTRACT FROM AUTHOR]

Pulsing 15N18O onto an annealed 1% Mn16Ox/Ce16O2 catalyst resulted in very fast oxygen isotope exchange and 15N2 formation at 295 K. In the 1st 15N18O pulse, due to the presence of large number of surface oxygen defects, extensive 15N218O and 15N2 formations were observed. In subsequent pulses oxygen isotope exchange dominated as a result of highly labile oxygen in the oxide. [ABSTRACT FROM AUTHOR]

Gender is presumed to be one of the factors causing interindividual variability in the brain's electrophysiological parameters. Our aim was to characterize the role of gender in visual evoked potentials (VEPs), event-related potentials (ERPs), visual mismatch negativity (vMMN) and the spectral characteristics of the EEG. We examined 42 healthy volunteers (21 women and 21 men, aged 20-29 years). We measured VEPs in response to pattern-reversal and motion-onset stimulation, ERPs in an oddball paradigm and vMMN in response to a combination of motion directions presented in the visual periphery. P100 peak latency for 40' reversal VEPs was significantly shorter in women than in men as determined using a non-parametric Wilcoxon signed-rank test. In addition, women showed higher relative EEG spectral power in the alpha band (p=0.023) and lower power in the theta band (p=0.004). Our results in this small but homogeneous group of subjects confirm previously reported gender influences on pattern-reversal VEPs and the EEG frequency spectrum. Gender should be taken into consideration in establishing norms on these measures. We found no statistically significant differences between women and men for any of the other stimuli presented. [ABSTRACT FROM AUTHOR]

Here we investigate isotope effects on the catalytic methanol synthesis reaction and the reactivity of copper-bound formate species in CO2–H2 atmospheres on Cu/SiO2 catalysts by simultaneous IR and MS measurements, both steady-state and transient. Studies of isotopic variants (H/D, 12C/13C) reveal that bidentate formate dominates the copper surface at steady state. The steady-state formate coverages of HCOO (in 6 bar 3:1 H2:CO2) and DCOO (in D2:CO2) are similar and the steady-state formate coverages in both systems decrease by ~80% from 350 K to 550 K. Over the temperature range 413 K–553 K, the steady-state methanol synthesis rate shows a weak H/D isotope effect (1.05 ± 0.05) with somewhat higher activation energies in H2:CO2 (79 kJ/mole) than D2:CO2 (71 kJ/mole) over the range 473 K–553 K. The reverse water gas shift (RWGS) rates are higher than methanol synthesis and also shows a weak positive H/D isotope effect with higher activation energy for H2/CO2 than D2/CO2 (108 vs. and 102 kJ/mole) The reactivity of the resulting formate species in 6 bar H2, 6 bar D2 and 6 bar Ar is strongly dominated by decomposition back to CO2 and H2. H2 and D2 exposure compared to Ar do not enhance the formate decomposition rate. The decomposition profiles on the supported catalyst deviate from first order decay, indicating distributed surface reactivity. The average decomposition rates are similar to values previously reported on single crystals. The average activation energies for formate decomposition are 90 ± 17 kJ/mole for HCOO and 119 ± 11 kJ/mole for DCOO. By contrast to the catalytic reaction rates, the formate decomposition rate shows a strong H/D kinetic isotope effect (H/D ~8 at 413 K), similar to previously observed values on Cu(110). [ABSTRACT FROM AUTHOR]

Abstract: CO2 is known to adsorb onto clay and other minerals when a significant atmospheric pressure is present. We have found that CO2 can also adsorb onto some clays when the CO2 partial pressure is effectively zero under ultra-high vacuum (UHV) if cooled to the surface temperatures of the icy satellites of Jupiter and Saturn. The strength of adsorption and the spectral characteristics of the adsorbed CO2 infrared (IR) absorption band near 4.25 μm depend on the composition and temperature of the adsorbent. CO2 remains adsorbed onto the clay mineral montmorillonite for of min when exposed to a vacuum of at . CO2 does not adsorb onto serpentine, goethite, or palagonite under these conditions. A small amount may adsorb onto kaolinite. When heated above 150 K under vacuum, the CO2 desorbs from the montmorillonite within a few minutes. The absorption band of CO2 adsorbed onto montmorillonite at 125 K is similar to that of the CO2 detected on the saturnian and Galilean satellites and is markedly different from CO2 adsorbed onto montmorillonite at room temperature. We infer the adsorption process is physisorption and postulate that this mechanism may explain the presence and spectral characteristics of the CO2 detected in the surfaces of these outer satellites. [Copyright &y& Elsevier]

A novel apparatus for gas phase heterogeneous catalysis kinetics is described. The apparatus enables fast isotopic transient kinetic analysis (ITKA) to be performed in which both the gaseous and adsorbed species inside the catalytic reactor are monitored simultaneously with rapid-scan transmission Fourier transform infrared (FTIR), and its gaseous effluent can be monitored by mass spectroscopy during rapid switching of reagent gas streams. This enables a more powerful version of the well-known steady-state isotopic transient kinetic analysis (SSITKA) technique in which the vibrational spectra of the gas phase and adsorbed species are also probed: FTIR-SSITKA. Unique reactor characteristics include tungsten construction, liquid nitrogen cooling or heating (∼200–770 K), pressures of 1.0–2.5 atm, fast reactor disassembly and reassembly, and catalyst loading in a common volume. The FTIR data acquisition rate of this apparatus (3 Hz) is tenfold faster than previously reported instruments. A 95% signal decay time of ∼3 s for gas switching was measured. Very good temperature reproducibility and uniformity (<±3 K) were observed by in situ rotational temperature analysis, which allows accurate calibration of the reactor thermocouple to the reactor gas temperature. Finally, FTIR-SSITKA capabilities are demonstrated for CO2 isotope switching over a γ-alumina sample at 75 °C, which reveal an adsorbed carbonate species with an average surface residence time of τ=148±5 s and a coverage of ∼2.5×1015 molecules cm-2. [ABSTRACT FROM AUTHOR]

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012. [ABSTRACT FROM PUBLISHER]

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010. [ABSTRACT FROM PUBLISHER]

Introduction: The aim of our study was to verify the possibility of early identification of HIV-related neural injury using visual evoked potentials (VEPs) in neurologically asymptomatic HIV seropositives. In the CART (combination antiretroviral therapy) era, the prevalence of neurocognitive impairment remains high, up to 50%, and HIV-associated neurocognitive disorder (HAND) has shifted towards a milder clinical presentation. Such a mild clinical presentation can escape detection [1]. Methods: The examination consisted of the Montreal Cognitive Assessment (MoCA) [2], and VEPs to pattern-reversal, motion-onset stimulation (radial movement), and of visual ERPs recorded during an odd-ball test (http://www.lfhk.cuni.cz/elf). Subjects: 9 homosexual men and 3 heterosexually infected women were examined in this study. All patients had ⩾350×106 CD4 cells/l blood at inclusion. The duration of the HIV infection was 0.5 – 7years, and mean age of the patients was 35 (24–50) years. Results: P100 potential was recorded with no alteration in the VEP amplitude or latency. However, in 5 patients with CD4 counts 350–750×106cells/l, there was prolonged latency of the N160 peak compared to the reference values obtained in our laboratory, which suggests a dysfunction of the motion-processing (magnocellular system or the dorsal cortical stream) [3]. P300 latencies and MoCA results were within the normal range in all HIV patients. Conclusions: Our data suggest that motion-onset VEPs may be a sensitive measure of subclinical visual pathway dysfunction in early HIV-1 infection, however, we did not reveal any cognitive decline in this pilot group. Subsequently, the patients will be investigated using VEPs and visual ERPs at six-month intervals to evaluate the long-term development of the visual pathway involvement in HIV patients. [ABSTRACT FROM AUTHOR]