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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 267-273 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution photoabsorption cross section data for the CO 4PG (1,0) band have been obtained under several different temperature conditions. It was found that the absorption strength of the d 3Δ1–X 1Σ+ (5,0) band underlying the 4PG (1,0) band varies with temperature. The ratio of the absorption band strength of the d–X (5,0) band to that of the 4PG (1,0) band has been determined for temperatures at 150 K, 295 K, and 370 K. Adopting the integrated oscillator strength of the 4PG (1,0) from the recent literature we have determined band absorption cross sections for the two bands as a function of temperature. The ratios of the band absorption strengths of the A–X (1,0) and d–X (5,0) bands at different temperatures are compared with those calculated from the mixing coefficients determined by analysis of level shifts in high resolution spectra and lifetime measurements. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 795 (1996), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0584
    Keywords: Acute leukemia ; Dura ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Retrospectively, the dura in 18 adult patients with acute leukemia were evaluated by gadolinium-enhanced T1-weighted magnetic resonance imaging (MRI). Abnormal dural enhancements were detected in three of four patients with positive cerebrospinal fluid (CSF) cytology, in one of five with suspicious central nervous system (CNS) disease, and in two of nine asymptomatic patients. Computed tomography failed to demonstrate any dural abnormality in these six patients. The abnormal dural enhancement was found in either (a) the brain and the spine, (b) the thoracolumbar spine, or (c) the area adjacent to the parenchymal lesions. Three of the patients were in hematological remission stage; disappearance of the abnormal dural enhancement was observed 1–2 months after radiotherapy and high-dose systemic chemotherapy. The results suggest that MRI is a sensitive and noninvasive imaging modality and superior to CT in detecting dural disease in leukemic patients.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0584
    Keywords: Key words Acute leukemia ; Dura ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Retrospectively, the dura in 18 adult patients with acute leukemia were evaluated by gadolinium-enhanced T1-weighted magnetic resonance imaging (MRI). Abnormal dural enhancements were detected in three of four patients with positive cerebrospinal fluid (CSF) cytology, in one of five with suspicious central nervous system (CNS) disease, and in two of nine asymptomatic patients. Computed tomography failed to demonstrate any dural abnormality in these six patients. The abnormal dural enhancement was found in either (a) the brain and the spine, (b) the thoracolumbar spine, or (c) the area adjacent to the parenchymal lesions. Three of the patients were in hematological remission stage; disappearance of the abnormal dural enhancement was observed 1–2 months after radiotherapy and high-dose systemic chemotherapy. The results suggest that MRI is a sensitive and noninvasive imaging modality and superior to CT in detecting dural disease in leukemic patients.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1433-2965
    Keywords: Bone mineral density (BMD) ; Dual X-ray absorptiometry (DXA) ; Fracture risk ; Postmenopause ; Quantitative computed tomography (QCT)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We compared quantitative computed tomography (QCT) and dual X-ray absorptiometry (DXA) with respect to their ability to discriminate subjects with and without prevalent vertebral fractures. In 240 post-menopausal women (mean age 63.7±6.9 years) lateral spine radiographs (T4-L4) were reviewed for the presence of vertebral fracture. Using a semiquantitative technique to grade the severity of vertebral deformities, we classified fractures as mild, moderate or severe (grade 1 to 3, respectively). Postero-anterior DXA (PA-DXA) and lateral DXA (L-DXA) measurements (L2–4) as well as QCT measurements of the lumbar spine (T12-L3 or L1–14) were obtained in all women. Seventy-two women were diagnosed with at least one fracture, and of these 40 were graded as mild. Comparing normal women with fractured women, we found the area under the receiver operating characteristics (ROC) curves to be greatest for QCT (0.81), followed by L-DXA (0.72) and PA-DXA (0.65). The differences among all three techniques were significant. Comparing the normal women with women having only mild fractures, the areas under the ROC curves were 0.79, 0.73 and 0.63 for QCT, L-DXA and PA-DXA, respectively. Significant differences existed between QCT and PA-DXA as well as between L-DXA and PA-DXA. Logistic regression analysis also revealed the highest age-adjusted odds ratios for QCT (3.67; 2.25–5.97) while L-DXA and PA-DXA showed substantially lower odds ratios (2.00; 1.39–2.87, and 1.54; 1.11–2.15, respectively). We conclude that low bone density as measured by QCT, PA-DXA or L-DXA is significantly associated with the prevalence of vertebral fractures. Of the methods studied, QCT of trabecular bone offered the best discriminatory capability. L-DXA proved to be superior to PA-DXA in its diagnostic sensitivity, particularly in women with mild fracture. Mild vertebral fractures are associated with decreased spinal bone density and may be regarded as osteoporotic deformities.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1433-2965
    Keywords: Key words:Computed tomography – Osteoporosis – Radiograph – Scoutview – Semiquantitative technique – Vertebral fracture assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract: Semiquantitative vertebral fracture assessment was compared between lateral computed tomography (CT) scoutviews and conventional thoracolumbar spinal radiographs. Vertebral levels T4–L4 were assessed by both techniques in a group of 56 women (mean age 60 + 13 years). In order to compare inter- and intra-observer variabilities for the two techniques, the images were analyzed twice by two independent observers, and percentage agreement and kappa statistics were measured both between readings and between observers. Percentage agreement and kappa statistics were also used to quantify differences between techniques. In the CT scoutviews, noise and artifacts from overlying tissues in the thoracic spinal levels rendered 3.4% of the vertebrae unreadable for the first observer and 8.3% for the second observer. For the CT scoutviews the agreement between readings was 98.1%, 97.3% and 100% (k = 0.87, 0.83 and 1.0) on T4–L12, T4–12 and L1–4, respectively for the first observer, and 97.8%, 97.1% and 99.5% (k = 0.79, 0.73 and 0.92) for the second observer. For the lateral radiographs, the agreement between readings was 97.7%, 96.9% and 100% (k = 0.87, 0.85 and 1.0) on T4–L12, T4–12 and L1–4, respectively for the first observer, and 98.4%, 97.7% and 99.5% (k = 0.86, 0.82 and 0.95) for the second observer. The agreement between observers was 96.1%, 94.4% and 100% (k = 0.68, 0.58 and 1.0) on T4–L12, T4–12 and L1–4, respectively for the CT scout-views and 96.8%, 95.9% and 99.0% (k = 0.79, 0.76 and 0.91) for the lateral radiographs. The inter-technique was 95.8%, 94.2% and 99.5% (k = 0.73, 0.68 and 0.95) on T4–L12, T4–12 and L1–4, respectively for the first observer and 95.6%, 94.2% and 99.0% (k = 0.64, 0.55 and 0.90) for the second observer, with the scoutview technique detecting, on average, 23% fewer fractures than the lateral radiographs. Although the vertebral fracture detection in lumbar spine is quite comparable to that of conventional radiographs, given its reduced sensitivity for vertebral fracture detection in thoracic spine, the lateral CT scoutview technique should not be substituted for conventional radiographs where diagnosis of all vertebral fractures is of primary importance.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1433-2965
    Keywords: Morphometry ; Osteoporosis ; Semiquantitative assessment ; Vertebral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To compare visual semiquantitative (SQ) reading and quantitative morphometry (QM) for assessing prevalent and incident vertebral fractures, radiographs of the thoracolumbar spine were evaluated in 400 (only baseline films) and 335 (baseline and follow-up films) postmenopausal women with osteopenia as defined by aT-score of less than 2 SD below young normals. QM was performed using different cutoff thresholds, and the SQ reading was performed by three radiologists independently. A joint consensus reading of the radiographs by all participating radiologists was used as a reference standard. Our results indicate that the concordance within SQ methods is excellent, and it is higher than that between SQ and QM regardless of the cutoff criteria used. This finding was consistent for the diagnosis of prevalent as well as incident vertebral fractures. For prevalent fractures the use of the 2.5 SD cutoff criterion provided the highest concordance with the consensus reading and with the radiologists' reading, thereby providing high sensitivity (70.23%) with moderate specificity (98.76%) relative to the consensus reading when compared with the 3 SD or 4 SD cutoff criteria. For the diagnosis of incident vertebral fractures the best agreement between our consensus reading and QM was found for an absolute reduction of 6 mm and for a combination of relative and absolute reduction of 15% and 3 mm in vertebral height. The respective sensitivities and specificities for the two criteria were 51%/99.9% and 75.4%/98.9%, respectively. Even though the consensus reading may favor the reader's evaluation over QM, the assessment of prevalent and incident fractures using QM alone may not be sufficiently reliable for detection of vertebral fractures in epidemiological studies and clinical trials. It should be performed principally in conjunction with a trained radiologist or a highly experienced clinician.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 32 (1996), S. 103-107 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung  Die Methode der diskreten Ordinaten wird unter Verwendung zusammengesetzter Quadraturen auf die Untersuchung des Strahlungsaustausches in vielschichtigen Medien mit Fresnel-Grenzflächen erweitert. Da die hier verwendeten diskreten Ordinaten von den kritischen Winkeln an den Grenzflächen abhängen – wobei das Integral entlang einer Richtung durch die kritischen Winkel in mehrere Subintervalle aufgespalten wird – können die diskreten Ordinaten für jede Schicht verschieden sein. Aus diesem Grunde läßt sich die Strahlungsintensität auf einer diskreten Ordinate einer der Schichten im allgemeinen nicht unmittelbar aus der Intensität auf den Ordinaten der anderen bestimmen. Um diese Schwierigkeit zu umgehen, wird die natürliche kubische Spline-Interpolation zur Approximitation der Winkelverteilung der Intensität auf den Innenflächen verwendet. Beim Vergleich der so gewonnenen Resultate mit bekannten Ergebnissen für spezielle Fälle erweist sich die Brauchbarkeit des entwickelten Berechnungsschemas. Die Einflüsse der Refraktionsindizes und der Streuungsalbedos auf das hemisphärische Reflexions- und Transmissionsvermögen eines dreischichtigen Mediums mit Fresnel-Grenzflächen wird diskutiert.
    Notes: Abstract  The discrete-ordinate method using composite quadrature is further extended to the analysis of radiative transfer in a multi-layer medium with Fresnel interfaces. Since the discrete ordinates used in the present method depend on the critical angles at the interfaces and the integral over direction is split into several subintervals by the critical angles, the discrete ordinates for each of the layers may be different. Thus, in general the radiation intensity on a discrete ordinate of one of the layers can not be obtained directly from the intensity on the discrete ordinate of the others. To circumvent the difficulty, the natural cubic spline interpolation is used to approximate the angular distribution of intensity at internal interfaces. The comparisons of the present results and the existing results for some special cases show that the present scheme works well. The effects of refractive indices and scattering albedos on the hemispherical reflectivity and transmissivity of a three-layer medium with Fresnel interfaces are discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 32 (1997), S. 271-275 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung  In der Arbeit wird ein Weg aufgezeigt, wie die Störstrahlungseffekte bei Anwendung der Methode der diskreten Ordinaten auf die Berechnung des Energietausches zwischen Oberflächenstrahlern vermieden werden können. Dies läßt sich durch Aufspaltung der Strahlungsintensität in die abgeschwächte einfallende und die vom Medium emittierte Komponente erreichen. Als Beispiel für die Anwendung dieses Verfahrens dient der Wärmeaustausch durch Strahlung in einem zweidimensionalen zylindrischen Behältnis, das mit einem nahezu transparenten Medium befüllt ist. Die mit der modifizierten Methode erhaltenen Ergebnisse stimmen ausgezeichnet mit jenen nach dem klassischen Brutto-Verfahren überein.
    Notes: Abstract  A study of the application of the discrete-ordinate method (DOM) with remedy for the ray effects to the solution of surface radiation exchange is presented in this paper. The remedy for the ray effects is achieved by dividing the radiative intensity into the attenuated incident and the medium emitting components. To demonstrate the application of the technique, this work considers radiative heat transfer in a two-dimensional cylindrical enclosure filled with a nearly transparent medium. The results obtained by the present DOM are in excellent agreement with those by the radiosity/irradiation method.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 33 (1998), S. 327-331 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This work considers transient conductive and radiative heat transfer in a two-dimensional, cylindrical, scattering medium heated or cooled by internal heat source or boundary surface. A finite difference scheme is employed for handling the energy storage and the heat diffusion by conduction, while a discrete-ordinate method is used to analyze the radiative heat transfer. The effects of various parameters, including the conduction-radiation parameter, the scattering albedo and the emissivity of the boundary surfaces, are investigated.
    Type of Medium: Electronic Resource
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