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  • 11
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1555-1563 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The photodissociation rate of phosgene (Cl2CO) adsorbed on Pt(111) has been measured as a function of photon energy at normal incidence and as a function of incident angle using p-polarized light. Compared to the gas phase, the wavelength dependence of the initial photolysis cross section on the surface is redshifted. The angular response to p-polarized light is wavelength dependent. Above 315 nm, the angular dependence correlates with calculated metal absorption. At 280 nm, the angular dependence is much too strong to be accounted for solely by substrate excitation. A combination of substrate and direct excitation is adequate. This is the first direct evidence, for monolayers on metals, that both direct and substrate excitation contribute to surface photochemistry but dominate at different wavelengths.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2681-2682 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The rates of photodissociation and photodesorption of dioxygen adsorbed on Ag (110) under ultraviolet irradiation have been measured as a function of polarization at normal incidence. No dependence of the rate was found on the angle between the O2 bond axis and the electric vector of the incident light. This result supports a mechanism for surface photochemistry in which substrate excitation is the dominant process.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5011-5020 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A Pt(111) surface saturated with molecular oxygen was irradiated by UV light from a mercury arc lamp with various cutoff filters. High-resolution electron energy-loss spectroscopy (HREELS) and temperature programmed desorption mass spectroscopy (TPD) were used to characterize the products retained on the surface. Upon UV irradiation at 95 K, chemisorbed O2 (peroxo) undergoes dissociation, desorption and rearrangement. Different wavelength dependences were observed for the three processes: dissociation was not observed at wavelengths longer than 295 nm, in agreement with gas phase photodissociation of the O–O bond in hydrogen peroxide; desorption and rearrangement became negligible at wavelengths longer than 420 nm, in agreement with the photolysis of an organometallic peroxoplatinum complex. For wavelengths between 230 and 315 nm, the average cross sections of dissociation and desorption were estimated to be 5.7×10−20 and 1.2×10−19 cm2 , respectively. The possible origins of the three processes are discussed.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 441-450 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the vibrational and electronic spectra for pyridine and benzene adsorbed on the Rh(111) crystal surface obtained by high-resolution electron energy loss spectroscopy (HREELS). Low-energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), and optical second harmonic generation (SHG) have also been used to provide complementary information. Pyridine adsorption on Rh(111) was studied over the 77–450 K temperature range. At 77 K, multilayers of pyridine are observed with a vibrational spectrum similar to that of liquid pyridine. Between 185 and 230 K, HREELS and TDS indicate that both physisorbed and chemisorbed pyridine species are present on the surface. The physisorbed species desorbs at 295 K, while the chemisorbed species is stable until it decomposes on the surface at 400 K. We propose that the chemisorbed species is an α-pyridyl complex as thermal desorption spectroscopy indicates partial dehydrogenation of this pyridine surface species. Electronic energy loss spectra for both benzene and pyridine adsorbed at 310 K show only a weak transition centered at ∼4 eV. The absence of prominent π→π* transitions, which are readily observed for multilayers of benzene adsorbed on Rh(111), implies that the π orbitals are strongly involved in the chemisorption bond of these molecules with the Rh(111) surface.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 7442-7447 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report evidence for the coexistence of direct and precursor dynamics in the dissociative chemisorption of H2 on Ni(l00). Hydrogen and deuterium uptakes on Ni(l00) were measured at various surface temperatures by following the secondary ion ratios, Ni2 H+/Ni+ and Ni2 D+/Ni+ , which are proportional to surface hydrogen and deuterium coverage on both clean and carbon-covered Ni(100). Between 100 and 200 K on clean Ni(l00), the initial sticking coefficient of hydrogen decreases, but only slightly, as the surface temperature increases. The decrease is more pronounced both in the presence of predosed carbon and for deuterium adsorption on Ni(100). This is interpreted as due to the involvement at low temperatures of a molecular precursor which mediates dissociative adsorption at low temperatures. The precursor probably involves surface defects and sites formed in the presence of carbon. In addition to the precursor channel, a direct dissociation channel also operates, and dominates for T≥200 K.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of the European Academy of Dermatology and Venereology 15 (2001), S. 0 
    ISSN: 1468-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Aim To compare the efficacy, safety and tolerability of adapalene gel 0.1% vs. tretinoin gel 0.025% in a Chinese patient population.Background Although acne vulgaris is a common problem among Asians and Asian-Americans, little has been published on the specific manifestations, sequelae, and treatment-responsiveness of this disorder in Asian skin types. Since Asian skin types tend to be more highly pigmented than those of white people of European descent, many Asians share the predisposition toward postinflammatory hyperpigmentation seen in Africans, African-Americans and other dark-skinned peoples. It is generally assumed that the efficacy and safety of topical retinoids is the same in Asians as in white people. Tretinoin has been available in China for decades; adapalene became available in 1998.Methods A total of 150 patients with grade II–III acne vulgaris seen at three dermatology clinics were randomized to 8 weeks of daily treatment with either adapalene gel 0.1% or tretinoin gel 0.025%. Counts of total lesions, inflammatory lesions and non-inflammatory lesions were made at baseline and again at treatment weeks 2, 4, 6 and 8. Global assessment ratings, based on percent lesion reduction from baseline were also made. Erythema, burning, pruritus, scaling and dryness were rated on a 0–3 severity scale.Results A total of 139 patients completed the efficacy evaluation, and 144 patients completed the safety evaluation. Both adapalene and tretinoin produce dramatic reductions in total, inflammatory and non-inflammatory lesion counts, in the range of 69–74% on average. More than 70% of patients in both groups had complete clearance or marked improvement. In general, irritation was mild, but was both more common and more severe in the tretinoin group vs. the adapalene group. No systemic side effects were seen.Conclusions Adapalene offers comparable efficacy to tretinoin, but is less irritating. It represents a good alternative for the treatment of mild to moderate acne vulgaris in Chinese patients.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 46 (1990), S. 86-94 
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A Monte Carlo simulation of an ordering phase transition in the surface region of a f.c.c.-type A3B binary alloy is reported. The main emphasis of this simulation is the evaluation of short and long-range-order correlations near the surface which are used for calculating X-ray intensities under grazing-incident-angle conditions. These calculations suggest effective ways of conducting surface diffraction experiments on order-disorder phase transitions. The simulation results are also compared with available experimental data.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 19
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 190 (1993), S. 1045-1052 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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