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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of medicinal chemistry 37 (1994), S. 2129-2137 
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the temperature-dependent characteristics of photoluminescence emission in modulation δ-doped AlxGa1−xAs/InyGa1−yAs/GaAs structures. Transition energies are analyzed using a self-consistent solution of the coupled k⋅P Hamiltonian–Poisson equation. At low temperatures, dominant emissions are due to the transitions from the first electron subband to the first heavy-hole subband and from the second electron subband to the first heavy-hole subband irrespective of the location of modulation doping. The second hole subband related transitions associated with the first electron subband or the second electron subband emerges with increasing temperature depending on the location of doping. The relative intensities of the transitions from the first and second electron subbands to the first heavy-hole subband transitions are analyzed as a function of the Fermi energy position. An excellent agreement is found between the measurements and calculations. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5394-5398 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism and control of ferroelectric polarization fatigue (loss of polarization with cycling) in donor- and acceptor-doped BaTiO3 ceramics and Pb(Zr1−xTix)O3 (PZT) thin films has been investigated. Experimental results clearly demonstrate that fatigue behavior is related to the defects within the materials. Donor-doped BaTiO3 ceramics showed significantly improved fatigue characteristics when compared with acceptor-doped materials. A similar but reduced effect has been observed in donor-doped PZT thin films. The electric-field-assisted migration of charged species within ferroelectric materials may be responsible for the degradation/fatigue behavior. Results support the expectation that oxygen vacancies play an important role in fatigue that occurs as a result of polarization switching.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 3673-3678 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the course of investigating synthesis routes, stability information was developed for YBa2Cu3O7−x, Y2Ba4Cu7O15−x, and YBa2Cu4O8. The results were obtained between ∼900 and 1040 °C and involve oxygen pressures between 10 and 145 atm. The observations show that the PO2-T ranges for stability of the three phases overlap and that some stable mixtures of the phases can be synthesized. The results are compared to the results of other experimental studies and to calculations based on calorimetric data.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 2671-2676 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: State-to-state cross sections for the collision-induced transitions of H+H2 (and isotopic analogs) have often been examined using quasiclassical trajectory calculations. The assignment of quasiclassical trajectory results to final rotational and vibrational states by histogram methods can lead to distributions for endoergic (upward) transitions that are rotationally or vibrationally hot when compared with quantum calculations or with experimental results. This effect is most pronounced near threshold for the transition of interest. Various histogram methods are examined to determine why they can lead to distributions that are hot. The application of detailed balance (microscopic reversibility) to cross sections calculated for the inverse of the endoergic transition results in distributions that are neither rotationally nor vibrationally hot; only those effects that can be attributed to the classical approximation of a quantum process remain.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 98 (1991), S. 0 
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective— To identify those congenital fetal anomalies, previously identified by ultrasound scanning, in which fast-scan magnetic resonance imaging (F-SMRI) would give additional information for the perinatal management of the infants.Design— Observational clinical study.Setting— Hospital Department of Obstetrics and Gynaecology/Resonance Research Centre.Subjects— Seven women carrying eight fetuses in whom congenital abnormal-ities had been identified using ultrasound scans. The duration of the pregnancies was 28 to 39 weeks gestation.Interventions— Fast-scan magnetic resonance imaging at between 28 and 39 weeks gestation.Main outcome measures— Identification of fetal abnormalities.Results and conclusions— F-SMRI was of limited value in the diagnosis of further assessment of fetuses with abnormalities of accumulation of tissue fluid. Renal anomalies were poorly identified unless associated with cystic formation of the kidney. Further study is required in the imaging of fetal central nervous system anomalies. Until echoplanar imaging is more widely available, MRI does not contribute to the diagnosis of cardiac anomalies. F-SMRI appears to be most useful in the diagnosis and management of soft tissue gastro intestinal abnormalities.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective To examine patterns of hysterectomy in the Oxford-Family Planning Association (Oxford-FPA) study in relation to age, parity, social class and calendar period (–1974, 1975–79. 1980–84, 1985–89).Design The Oxford-FPA study is a large scale prospective study of 17 032 women recruited from 1968–74 and still under observation.Setting Seventeen family planning centres throughout England and Scotland.Subjects At recruitment the 17 032 women were all white, British, married, aged 25–39 and willing to co-operate. In addition, they were using the pill or an intrauterine device or a diaphragm as their method of contraception. Main outcome measure Hysterectomy rates per 1000 woman-years of observation in various subclasses of the data.Results Up to the end of 1989, 1885 (11.1%) of the 17 032 women in the study were known to have undergone hysterectomy. Fibroids were the most common cause followed closely by menstrual disturbances in the absence of fibroids (hereafter referred to as ‘menstrual disturbances’). Social class had a modest influence on hysterectomy rates. Hysterectomy for fibroids, prolapse, endometriosis and ‘other reasons’ showed little trend with calendar period while hysterectomy for menstrual disturbances and for cancer showed a sharp increase with calendar time especially at ages 30–39. Hysterectomy generally tended to increase with age and showed a strong relation to parity; in particular, hysterectomy for fibroids fell with parity and hysterectomy for menstrual disturbances rose sharply with parity. Using lifetable methods, it was estimated that almost 20% of the women in the study would have had a hysterectomy by age 55.Conclusions The results give insights into factors affecting hysterectomy rates. Of particular interest is the modest influence of social class, the strong influence of parity and the rise in rates with calendar time at ages 30–39 for those undergoing hysterectomy for menstrual disturbances or cancer, but since the cohort is not directly representative of the population, some caution is required in extrapolating these findings. The estimated hysterectomy rate of about 20% by age 55 is in line with other similar estimates for the United Kingdom.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6289-6292 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of oxygen loss on the luminescence of YBa2Cu3O7−x has been investigated by cathodoluminescence (CL) in the scanning electron microscope (SEM) and by Raman microprobe measurements. The results herein indicate that a CL band at 530 nm is related to oxygen loss rather than to impurity phases such as Y2O3 formed in the material by electron irradiation in the SEM.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 310-312 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Undeveloped and unbaked paterns or latent images (LI) in polymethylmethacrylate (PMMA) have been observed and measured using different measurement techniques. Results from two common-path baseband optical techniques have been compared with the results of profiling LI using an atomic force probe. These results indicate that 5 A(ring) detection limits in optical path length measurements are easily achievable at near video rates using simple optical systems.
    Type of Medium: Electronic Resource
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