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  • 2000-2004  (11)
  • 1985-1989  (34)
  • 1980-1984  (16)
  • 1915-1919  (9)
  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2807-2815 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Molecular beam and time of flight methods have been used to examine the angular distributions and velocity distributions of the CO2 product molecules formed in the catalytic oxidation of CO on a Rh(111) single crystal in the surface temperature range 700–1000 K. The angular distribution was sharply peaked about the surface normal, and cannot be described by a simple cosn θ expression. No temperature dependence was observed in the angular distribution over the range of temperatures studied here. Observed velocity distributions were clearly non-Maxwellian and had average translational energies in excess of those expected at the surface temperatures. Furthermore, the average velocity depended strongly on the desorption angle. Molecules desorbing along the surface normal had an average translational energy of ∼8 kcal/mol. The average energy decreased with increasing angle, reaching a value of ∼4 kcal/mol at an angle of 60°. All of the observed velocity distributions were narrower than Maxwellian distributions with the same average energies. Product velocity distributions did not appear to vary with surface temperature. The observed excess energies are believed to arise from the crossing of the activation barrier to reaction, with a fraction of the reaction energy being carried away from the surface by the product molecules.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1163-1169 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The catalytic oxidation of carbon monoxide on a Rh(111) surface has been investigated using modulated molecular beam techniques. Reaction proceeds via a Langmuir–Hinshelwood mechanism. Under experimental conditions which provide a high coverage of oxygen adatoms and near zero coverage of adsorbed CO, an activation energy of 24.5±0.4 kcal/mol and a preexponential factor of 2±1×10−3 cm2 s−1 were obtained. The angular distribution of the product CO2 is sharply peaked toward the surface normal, and cannot be described by a simple cosnθ expression. Present results are discussed in relation to previous work on platinum and palladium surfaces.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 17 (2001), S. 0 
    ISSN: 1475-2743
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Objective To determine the risk of recurrent cervical intraepithelial neoplasia (CIN) in women with complete or incomplete excision of cervical intraepithelial neoplasia treated by large loop excision of transformation zone (LLETZ).Design A retrospective studySetting One consultant-led colposcopy clinic at Leicester Royal InfirmaryPopulation Three hundred and ninety-four women referred consecutively to the colposcopy clinic between 1991 and 1992.Main outcome measures The histological recurrence rate of CIN, length of cytological follow up following treatment related to degree of completeness of excision at initial treatment.Results Three hundred and twenty-two women had complete cytological or histological follow up. The mean length of follow up was 73 months with a mean number of six smears. Women with incomplete excision of CIN had a significantly higher risk of recurrent CIN (relative risk 8.23) occurring in a significantly shorter time compared with women with complete excision.Conclusions This study demonstrates that large loop excision of transformation zone is successful in over 95% of cases. Cytological surveillance is satisfactory for follow up of women who have complete excision of CIN. Women with incomplete excision of CIN at initial LLETZ remain at significant risk of developing further CIN and long term colposcopic and cytological follow up is necessary.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 93 (1986), S. 0 
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3896-3898 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present a study of the anisotropic properties of two-dimensional electron gases formed in GaAs/AlGaAs heterostructures in which InAs self-assembled quantum dots have been inserted into the center of a GaAs quantum well. We observe an anisotropic mobility for the orthogonal [1¯10] and [110] directions. The mobility in the [1¯10] direction was found to be up to approximately twice that in the [110] direction. It is suggested that the interface roughness scattering due to the inserted InAs material could be a cause for the large anisotropies in mobility. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of public health dentistry 64 (2004), S. 0 
    ISSN: 1752-7325
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Objectives: This study determines tooth loss rate over a 10-year period and identifies predictors of tooth loss in two separate US adult longitudinal study populations. Methods: Subjects from the Baltimore Longitudinal Study of Aging (BLSA), consisting of 47 men and 47 women, ages ranging from 30 to 69 years, were compared to subjects from the VA Dental Longitudinal Study (VADLS) in Boston, MA, consisting of 481 men in the same age range. Baseline and follow-up examinations were performed on each cohort over a 10-year period. Using multivariate regression models, significant predictors of tooth loss were identified. Results: A mean rate of tooth loss of 1.5 teeth lost per 10 years was noted in the VADLS cohort compared to 0.6 teeth lost per 10 years in the BLSA (P〈.001). Combining subjects from both populations, significant predictors of tooth loss were baseline values of: percent of teeth with restorations, mean probing pocket depth score, age, tobacco use, alcohol consumption, number of teeth present, and male sex. However, the set of significant predictor variables differed between the two populations and sexes. In BLSA men, number of teeth present, percent of teeth with restorations, mean probing pocket depth score, and alcohol consumption, but not age, were significant, while in BLSA women, only age was a significant predictor. Conclusions: Over a 10-year period, the incidence of tooth loss, the rates of tooth loss, and the predictors of tooth loss were found to vary by population and by sex. These results illustrate the limits of generalizing tooth loss findings across different study cohorts and indicate that there may exist important differences in risk factors for tooth loss among US adult populations.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 107 (2000), S. 0 
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Medicine 39 (1988), S. 221-229 
    ISSN: 0066-4219
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Earth and Planetary Sciences 12 (1984), S. 39-59 
    ISSN: 0084-6597
    Quelle: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Thema: Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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