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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 34 (1993), S. 5451-5467 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The spectral properties are established and the stability of the eigenvalues under the singular perturbation representing the relativistic corrections are proven for a family of ordinary differential operators describing a relativistic deformation of the quantum harmonic oscillator.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Computer Physics Communications 72 (1992), S. 249-264 
    ISSN: 0010-4655
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Computer Science , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 56 (1995), S. 410-414 
    ISSN: 1432-0827
    Keywords: Cortical bone ; Trabecular bone ; Radiogrammetry ; Photodensitometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Distal radius photodensitometric and second metacarpal radiogrammetric measurements were obtained from computerized analyses of standard hand X-Ray films of 296 Caucasian subjects (189 women and 107 men). This sample included 134 subjects ≥65 years old (75 women and 59 men). Distal radius bone density and metacarpal index showed a significant linear decrease with age in both sexes. Rates of bone loss, calculated from the regression curves, were-0.7% per year in women and-0.5% per year in men by distal radial photodensitometry, and-0.49% per year in women and-0.33% per year in men by metacarpal radiogrammetry. In the elderly subgroup, women ≥65 years of age showed an even faster bone loss, with an annual decrease of-1.4% by distal radial photodensitometry. Conversely, men ≥65 years of age had no significant bone loss, not even by metacarpal radiogrammetry. In conclusion, these data suggest that appendicular cortical bone loss ocurs at a higher rate in elderly females than in the elderly males, both at the distal radial and at the metacarpal site.
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  • 4
    ISSN: 1432-0827
    Keywords: Key words: Aging — Cortical bone — Photodensitometry — Radiogrammetry.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. In order to evaluate in vivo the entity of endosteal and periosteal changes with age in the two sexes, and their relative contribution to age-related cortical bone loss, we undertook a cross-sectional study on a population of normal Caucasian subjects. The group included 189 women and 107 men who were studied by photodensitometry and radiogrammetry of the second metacarpal bone, derived from the same standard hand X-ray. Of the subjects, 134 were 65 years of age or older (75 women and 59 men). Metacarpal bone mineral density (BMD) correlated with age in both sexes, with an annual bone loss rate of 0.5% in women and 0.15% in men. In the over 65 group, correlation was significant only in women, who underwent an acceleration in the rate of bone loss (1% per year). Marrow cavity width (M), cortical index at the second metacarpal shaft (MI) and external width (W) all correlated with age in both sexes, although generally better in the female than in the male sex. M almost doubled from the fourth to the ninth decade in women and increased 50% in men. In the same age interval, MI showed an annual decrease of 0.49% in females and 0.33% in males. In the over 65 group, cortical thinning rate was significant in women (0.39% per annum) but not in men (0.14% per annum), whereas correlation of W was not significant in either sex. Finally, MI correlated with BMD in the whole study population and in the over 65, with a female prevalence in correlation strength maintained throughout life. The following conclusions can be derived for metacarpal aging: (1) an acceleration in cortical bone loss occurs in females after age 65; (2) age-related growth in periosteal diameter, although significant in the whole population, is negligible in the elderly of both sexes; (3) age-related cortical bone loss is generally more dependent on cortical thinning in women than in men.
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  • 5
    ISSN: 1432-0827
    Keywords: Key words: Dual energy X-ray absorptiometry — Proximal femur — Reproducibility — Aging — Coefficient of variation.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Densitometric measurements are prone to imprecision in elderly subjects and the present study was primarily designed to dissect out the effects of age and bone mineral density on proximal femur dual energy x-ray absorptiometry (DXA) reproducibility. The study comprised 17 elderly women (mean age 74.6 years, range 65–84 years), 13 early postmenopausal women with osteopenia (mean age 56.2 years, range 50-63 years), and 17 elderly men (mean age 73.8 years, range 65-86 years). Each subject was given triplicate proximal femur scans by a QDR 2000 Densitometer (Hologic Inc., Waltham, MA) with repositioning between scans. Because of subject selection in the early postmenopausal women there were no significant differences in bone mineral density (BMD) at any site among the three groups. Despite this, reproducibility errors expressed as either coefficient of variation (CV) % or mean standard deviation (SD) were greater in the elderly subjects, regardless of gender, when compared with the younger female subjects. The variability in measurement errors with age were least marked for the total hip and trochanteric sites. Within the elderly subjects, BMD appeared to exert little influence on measurement errors. We conclude that short-term proximal femur reproducibility is dependent on age-related factors other than BMD. There is no influence of gender on the measurement errors. It is likely that local factors (e.g., hip osteoarthritis) or general frailty may influence repositioning but this needs further exploration. In the meantime, the total hip and trochanteric sites should be used as they provide the most reproducible measurements in the elderly.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Theory of computing systems 33 (2000), S. 257-293 
    ISSN: 1433-0490
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. Many families of grammars have been studied to extend the power of context-free grammars, while retaining the attractive properties of context-free languages. Some of these formalisms have been proved equivalent to tree adjoining grammars ( tag ), introduced by computational linguists to model natural languages. Another family of grammars, multidepth grammars, introduced for describing the syntax of programming languages, generates a hierarchy of languages, called k -pushdown languages (k-pdl ), for k ≥ 1 . Multidepth grammars are simpler than some other formalisms and have a very natural accepting device, called multipushdown automaton. Here we study the relationship of k-pdl with tal , the class of languages generated by tag . We prove that 2-pdl ⊂ tal ⊂ 3-pdl . Moreover, tal can be characterized exactly as the smallest full super-AFL that includes 2-pdl .
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Semigroup forum 15 (1977), S. 281-282 
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 47 (1990), S. 547-558 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We show that a massive use of statistical event correlations, learned by means of Monte Carlo event generators, makes it feasible to employ a pure jet signature in top quark searches. A relevant ingredient for that is also the less diffuse angular distribution of energy deposition and of particles in top events, which are dominated by quark jets. On the other, hand, we show that the utilization of mass cuts on jet combinations to identify top non-leptonic decays meets severe limitations already at the parton level, largely because of QCD radiation.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 53 (1992), S. 139-148 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Neural network and conventional statistical techniques are compared in the problem of discriminating $$p\bar p \to t\bar t$$ events, with top quarks decaying into anything, from the associated hadronic background at the energy of the Fermilab collider. The NN we develop for this sake is an improved version of Kohonen's learning vector quantization scheme. Performance of the NN as a $$t\bar t$$ event classifier is found to be less satisfactory than that achievable by statistical methods. We conclude that the probable reasons for the are: i) the NN approach presents advantages only when dealing with event distributions in the feature space which substantially differ from Gaussians; ii) NN's require much larger training sets of events than statistical discrimination in order to give comparable results.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Mathematik 109 (1990), S. 205-219 
    ISSN: 1436-5081
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper a characterization of the regular ω-semigroups whose congruence lattice is semimodular is given. The characterization obtained for such semigroups generalizes the one given by Scheiblich for bisimple ω-semigroups. Notice that we use the definition of semimodularity which other authors call double covering property.
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