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  • 1
    Digitale Medien
    Digitale Medien
    The adsorption of hydrogen on a ruthenium (101¯0) surface (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 3729-3743 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Video-LEED, HREELS, TDS, and Δcursive-phi measurements were used to investigate the adsorptive, structural, and vibrational properties of the Ru(101¯0)/H system between 100 and 500 K. At all temperatures investigated hydrogen adsorbs dissociatively with very high initial sticking probability (s0(approximate)1.0) with apparent precursor mechanism. The saturation coverage at 100 K is extraordinarily high (aitch-thetamax =2(approximately-equal-to)1.728×1015 H atoms cm−2), up to this coverage four H binding states α, β1, β2, and β3 can be distinguished having desorption energies between 56 KJ/mol (α) and 80 KJ/mol (β3). The H binding states are intimately correlated with the four observable ordered H phases: At aitch-theta=1 a c(8×2) or "1×2'' structure with weak split spots appears which transforms at higher coverages into a clear 1×2 phase with likewise weak spots and with maximum intensity at aitch-theta=1.2. It follows a c(2×2)-3H phase (I maximum at aitch-theta=1.5) with rather more intense ‘extra' spots which fade away with increasing coverage until at aitch-theta=2.0 a (1×1)-2H pattern is reached. The (positive) H-induced work function change Δcursive-phi runs through two maxima and saturates at ∼250 mV. The vibrational loss spectra which were measured in two perpendicular azimuths exhibit a variety of bands which can be correlated with the ordered H phases and point to H species bound in two different kinds of threefold coordinated sites. Our data suggest several structural similarities with the neighboring system in the periodic table, Rh(110)/H, but also interesting differences.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.456856
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  • 2
    Digitale Medien
    Digitale Medien
    Localization, the clue to fast magnetic reconnection (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4729-4731 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effect of localization of the resistivity is studied in the coalescence of two magnetic flux bundles. The reconnection process is consistent with the Petschek configuration, and the reconnection rate E depends only weakly on the value η0 of the resistivity at the X-point, E∝1/|log η0|. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1412600
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  • 3
    Digitale Medien
    Digitale Medien
    Electron magnetohydrodynamic turbulence (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 751-758 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Electron magnetohydrodynamic (EMHD) turbulence is studied in two- and three-dimensional (2D and 3D) systems. Results in 2D are particularly noteworthy. Energy dissipation rates are found to be independent of the diffusion coefficients. The energy spectrum follows a k−5/3 law for kde〉1 and k−7/3 for kde〈1, which is consistent with a local spectral energy transfer independent of the linear wave properties, contrary to magnetohydrodynamic (MHD) turbulence, where the Alfvén effect dominates the transfer dynamics. In 3D spectral properties are similar to those in 2D. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.873312
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  • 4
    Digitale Medien
    Digitale Medien
    Instability of a magnetized plasma jet (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2485-2488 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The stability characteristics of a plasma jet V(x)=sech2 x embedded in a parallel magnetic field B(x)=B0 tanh x are investigated. The Kelvin–Helmholtz kink mode, which dominates at small B0, is stabilized at B0=0.46, while the pinch mode remains unstable up to B0=0.96. Contrary to a nonmagnetized jet, for finite B0 the kink mode saturates quasilinearly by broadening the jet, such that B0/Vmax becomes larger than the marginal value 0.46. Including finite resistivity the nonlinear behavior is eventually governed by the tearing mode for all values of B0≠0, consisting of a single plasmoid moving along the jet. Hence the shear flow cannot stabilize the tearing mode, so that the apparent tearing stability of resistive current sheets observed in numerical simulations of magnetic reconnection is only due to finite-length effects. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872931
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  • 5
    Digitale Medien
    Digitale Medien
    Two-fluid theory of collisionless magnetic reconnection (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1002-1009 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Theoretical studies of collisionless reconnection in the framework of two-fluid theory are presented. In the high-β case (β(approximately-greater-than)1) reconnection is controlled by the whistler mode, leading to decoupling of ions from electrons on scales 〈c/ωpi. Though reconnection requires electron inertia, the reconnection rate is independent thereof, controlled only by ion inertia. Reconnection is hence much faster than in the absence of the Hall term. In the opposite limit of small β the strong axial field suppresses the whistler mode. Hence ions have to follow the electrons in the narrow reconnection layer δ∼c/ωpe, forming a macroscopic current sheet which strongly reduces the reconnection rate. Theoretical scaling laws are confirmed by numerical simulations. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872211
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  • 6
    Digitale Medien
    Digitale Medien
    On two-dimensional magnetohydrodynamic turbulence (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 3282-3292 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Numerical studies of decaying two-dimensional (2D) magnetohydrodynamic (MHD) turbulence are presented. Results concern mainly the decay laws of integral quantities and the scaling properties of spectra and structure functions. The self-similarity of the decay is characterized by the invariance of the ratios of resistive and viscous dissipation rates, kinetic and magnetic energies, and mean parallel and perpendicular velocities. The energy decay rate is primarily determined by the conservation of the mean-square magnetic potential, but the process is somewhat retarded at intermediate times by current density condensation in the magnetic eddies. In contrast to the 3D case, the energy spectrum agrees with the Iroshnikov–Kraichnan (IK) law Ek∼k−3/2, but is modified by a strong anomalous bottleneck effect. Structure functions of the Elsässer fields satisfy the property of extended self-similarity, which provides accurate values of the relative scaling exponents. Also the structure functions themselves show clear scaling properties, particularly at the highest Reynolds numbers studied. The scaling exponent ζ2 is consistent with the IK spectrum, but ζ3 and ζ4 remain distinctly below unity, which is surprising in view of an exact relation suggesting ζ3=1. Finally, the role of the tearing mode in 2D MHD turbulence is revisited. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1377611
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  • 7
    Digitale Medien
    Digitale Medien
    Randomized placebo-controlled trial of a flavonoid-rich plant extract-based cream in the treatment of rosacea (2005)
    Oxford, UK : Blackwell Science Ltd
    Journal of the European Academy of Dermatology and Venereology 19 (2005), S. 0 
    Details
    ISSN: 1468-3083
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Background  Biological research suggests that vascular changes may play a major role in rosacea pathogenesis. Chrysanthellum indicum is a plant-based extract containing a unique combination of phenylpropenoic acids, flavonoids and saponosids, and has a well-documented effect on vascular wall permeability and increase of the mechanical resistance of capillaries.Objective  To determine the efficacy and safety of a cream containing 1%C. indicum extract with vitamin P properties in the treatment of rosacea.Methods  This study included 246 patients diagnosed clinically as having moderate rosacea. Patients were randomly allocated to C. indicum extract-based cream (n = 125) and placebo (n = 121) groups. Patients were advised to apply the products on their face twice a day for a 12-week period. The patients were examined at the end of each 4-week period. Severity of erythema (graded by reference to six photographs), surface of erythema and rosacea overall severity scores were recorded at each visit on days 0, 28, 56 and 84. Investigators carried out a final efficacy assessment at the end of week 12. Volunteers’ final overall efficacy assessment was recorded in a self-administered questionnaire. Adverse events were identified through examination, interview and collection of comments in patients’ questionnaires.Results  Treatment with the C. indicum extract-based cream resulted in significant improvement (P 〈 0.05) in severity of erythema, overall rosacea severity compared to baseline and placebo, and investigator and patient overall efficacy assessment scores (P = 0.046 and P = 0.001, respectively) compared with placebo scores. Adverse reactions were mild, and did not differ between the C. indicum extract-based cream and the placebo groups.Conclusion  Chrysanthellum indicum extract-based cream is an effective and well-tolerated topical agent for the treatment of moderate rosacea. The mode of action of the active ingredient suggests that additional efficacy might be expected from combination with other topical treatments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1468-3083.2005.01248.x
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  • 8
    Digitale Medien
    Digitale Medien
    A Reciprocating Laboratory Shaker (1938)
    s.l. : American Chemical Society
    Industrial and engineering chemistry 10 (1938), S. 281-282 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/ac50121a019
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  • 9
    Digitale Medien
    Digitale Medien
    Oral health and dental care in modern-day China (2001)
    Copenhagen : Munksgaard International Publishers
    Community dentistry and oral epidemiology 29 (2001), S. 0 
    Details
    ISSN: 1600-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract – The purpose of this paper is to present salient background information on the oral care situation and organization in China and to review epidemiological literature that has been published on adults in Chinese dental journals during the last 20 years as a context for understanding ongoing oral health research activities in China. Searches were conducted through Medline as well as Chinese language catalogues and around 30 Chinese dental journals. Most oral health surveys on adults were conducted after 1970 mainly on residents living in big cities, which are also the location of major medical universities. Surveys conducted among farmers were uncommon. Dental caries and periodontal disease were the major dental diseases studied. Only a few surveys on people’s oral health knowledge, attitudes and behavior were conducted. Papers concerning dental treatment needs and utilization of dental services among adults were scarce. Sample size was usually not a major problem in these surveys but the sampling methods and diagnostic criteria used were often poorly defined. Mean DMFT scores between 2 and 6 were reported in the 35–44-year-olds and between 9 and 16 in the elderly younger than 75 years. Calculus and gingivitis were reported to be common in adult Chinese; the proportion of subjects with shallow and deep periodontal pockets was not high. Complete edentulousness in the 60–69-year-olds was usually reported to be less than 10%. About 14% of the 35–44-year-olds and 19% of the 65–74-year-olds did not brush their teeth daily/〉.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1600-0528.2001.290501.x
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  • 10
    Digitale Medien
    Digitale Medien
    The interaction of hydrogen with a cobalt(101¯0) surface (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 5388-5401 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The adsorption of hydrogen on a cobalt(101¯0) surface was investigated in ultrahigh vacuum (UHV) between 85 and 500 K using Video-LEED, temperature-programmed thermal desorption (TPD), work function (ΔΦ) measurements, and high-resolution electron energy loss spectroscopy (HREELS). Between 90 and 200 K, hydrogen adsorbs dissociatively with high sticking coefficient (s0≥0.8) via precursor kinetics and forms, with increasing exposure, a c(2×4), a p2mg (2×1) and a (1×2) LEED structure (hydrogen coverages aitch-thetaH=0.5, 1.0, and 1.5, respectively). While the first two structures represent true ordered hydrogen phases there is strong evidence that the (1×2) phase is reconstructed, likely in a paired-row configuration. The formation of the (1×2) phase is slightly thermally activated; its decomposition produces a sharp thermal desorption maximum (α state) appearing on the low-energy side of a β-TPD signal which reflects the hydrogen desorbing from the unreconstructed surface. The activation energies for desorption from the α and β states are 62 and 80 kJ/mol, respectively. Chemisorption in the β state [(2×1) phase up to aitch-thetaH=1.0] is associated with a ΔΦ of +207 meV, while the fully developed (1×2) reconstructed phase (α state) causes a ΔΦ of approximately −122 meV resulting in an overall work function change of +85 meV at saturation. From HREELS, we determine the H adsorption site in all superstructures to be threefold with a local CS symmetry. Our results are discussed and compared with previous findings for similar metal–hydrogen interaction systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.467392
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