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  • 2000-2004
  • 1995-1999  (28)
  • 1940-1944
  • 1997  (28)
  • 1
    Electronic Resource
    Electronic Resource
    Intersubband all-optical limiter based on thermally induced intervalley transfer (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7662-7665 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose an all-optical limiter based on the thermally induced intervalley transfer of electrons from Γ-valley states with forbidden normal-incidence intersubband interactions to L-valley states which absorb strongly. Detailed modeling of the device performance in the short-pulse regime (≤100 ns) yields that the output intensity for a limiter with only 10% insertion loss at low excitation levels will remain clamped over a dynamic range of 25–40.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365344
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative mobility spectrum analysis of multicarrier conduction in semiconductors (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 709-713 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate an optimized quantitative mobility spectrum analysis (QMSA) technique for determining free electron and hole densities and mobilities from magnetic-field-dependent Hall and resistivity data. The procedure is applied to an In1−xGaxAs–In1−xAlxAs single quantum well, GaAs–AlAs asymmetric double quantum wells, and Hg1−xCdxTe epitaxial thin films containing multiple carrier species. The results illustrate the reliability, versatility, and sensitivity of the analysis, which is fully computer automated following input of the magnetic-field-dependent data. QMSA is found to be a suitable standard tool for the routine electrical characterization of semiconductor material and device transport properties. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364211
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  • 3
    Electronic Resource
    Electronic Resource
    Boundary roughness scattering in single and coupled quantum wires in a magnetic field (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 3881-3887 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate magnetic-field-dependent velocity relaxation due to boundary-roughness scattering in quantum wires, using a two-dimensional (2D) finite-difference wave-packet propagation technique. We find that for low disorder correlation lengths and far away from density-of-states singularities associated with subband minima and saddle points, the Born approximation adequately reproduces the qualitative features of the more general 2D results. However, naive application of the Born approximation in regions where disorder-induced broadening or higher-order scattering become important can lead to substantial errors. In particular, the mobility enhancement associated with the opening of a quasigap in coupled quantum wire structures can be overestimated by as much as several orders of magnitude. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365691
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  • 4
    Electronic Resource
    Electronic Resource
    High-temperature type-II superlattice diode laser at λ=2.9 μm (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3607-3609 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A 2.9 μm diode laser with InAs/GaSb/Ga0.75In0.25Sb/GaSb superlattice active region displays a maximum operating temperature of 260 K. At 200 K, the threshold current density is 1.1 kA/cm2 and the quantum efficiency is 〉15%. The peak output power per facet exceeds 800 mW at 100 K and 200 mW at 200 K for a 0.05% duty cycle. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120455
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  • 5
    Electronic Resource
    Electronic Resource
    Midinfrared vertical-cavity surface-emitting laser (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3483-3485 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a type-II antimonide midinfrared vertical-cavity surface-emitting laser. The emission wavelength of 2.9 μm is nearly independent of temperature (dλ/dT(approximate)0.07 nm/K) and the multimode linewidth is quite narrow (3.5 nm). The pulsed threshold power at 86 K is as low as 22 mW for a 30 μm spot. Lasing is observed up to T=280 K, and the peak output power from a 600 μm spot exceeds 2 W up to 260 K. The differential power conversion efficiency is 〉1% at 220 K. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120366
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  • 6
    Electronic Resource
    Electronic Resource
    Radioiodine-labelled alpha-methyl-tyrosine in malignant melanoma:cell culture studies and results in patients (1997)
    Oxford, UK : Blackwell Publishing Ltd
    British journal of dermatology 137 (1997), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Tyrosine is a precursor of melanin synthesis and might thus present a valuable marker for melanoma. The aim of this study was to evaluate the uptake of alpha-methyl-tyrosine(AMT) in melanoma cell cultures and to assess its usefulness as a radiopharmaceutical for staging melanoma patients with whole-body scintigraphy. Melanoma (M19-cell lines) and fibroblast (negative control) cell cultures were incubated with125I-AMT and the radioactive uptake in the cell lines was measured in a gamma-counter over 24h. For in vivo studies, planar whole-body scintigraphy and single photon emission computed tomography (SPECT) of the tumour region was performed following injection of 250–350 MBq123I-AMT in six patients with known melanoma metastases. Findings were compared with results of whole-body positron emission tomography using 18F-fluorodeoxyglucose (FDG-PET) as a standard of reference. Fibroblasts showed an unchanged uptake of (mean±SD)0.56±0.09% 15min and 0.066±0.09% 24h, respectively, after incubation of 125I-AMT, whereas there was an increased uptake in melanoma cell cultures over time from 0.9±0.05% to 7.5±1.6%. In staging melanoma patients, the sensitivity of whole-body AMT-scintigraphy compared with FDG-PET was 37%(10 of 27 metastases). AMT is transported and metabolized to a high extent in melanoma cells and 123I-AMT is accumulated in melanoma metastases. Owing to its low sensitivity, however, the clinical use of whole-body AMT scintigraphy cannot be recommended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2133.1997.1774184.x
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  • 7
    Electronic Resource
    Electronic Resource
    A realistic approach to the sensitivity of PCR-DGGE and its application as a sensitive tool for the detection of clonality in cutaneous T-cell proliferations (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Experimental dermatology 6 (1997), S. 0 
    Details
    ISSN: 1600-0625
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract The practical value of the detection of clonality within the T-cell receptor gamma locus by polymerase chain reaction for the diagnosis of cutaneous T-cell lymphomas is well known. However, studies dealing with this subject so far, with special emphasis on the sensitivity of the technique in comparison to, for example, Southern blotting have used mixtures of DNA in various concentrations instead of using mixtures of the cells involved, which would reflect the in vivo situation in a more realistic scope. The purpose of this study was therefore to determine the sensitivity and the limitations of the PCR assay by dilution experiments, using mixtures of cells. Furthermore we studied its applicability to cutaneous T-cell proliferative disorders. Two clonal T-cell lines (MyLa and Jurkat) served as positive control. Dilutions of MyLa cells, cultured normal human keratinocytes and peripheral blood mononuclear cells from lymphoma negative volunteers were used to assess the sensitivity of the PCR-DGGE assay. Skin samples from 4 patients with cutaneous T-cell lymphoma, 1 lesional lymph node, 2 blood samples from a patient with Sézary syndrome and 4 lymphoma-negative tissue samples were analysed. Two samples were uncertain for diagnosis of lymphoma. The PCR-DGGE assay consisted of a 2-round nested PCR with consensus primers within the TCR-gamma locus followed by electrophoretic separation of the product along a denaturing urea/formamide gradient gel. PCR-DGGE sensitivity was, to our knowledge, for the first time investigated for mixtures of lymphocytes (clonal and polyclonal) and keratinocytes. Clonal T-cells were detected in a concentration between 1–0.1% in keratinocytes, whereas the sensitivity was generally lower upon dilution in peripheral blood mononuclear cells or in a mixture of keratinocytes and peripheral blood mononuclear cells. Nevertheless, T-cell clonality was detected in 2 blood samples of a patient with Sézary syndrome, which were negative by Southern blot analysis. The crucial point of this work was the new approach to establish the sensitivity of the PCR-DGGE, in a way which more closely mimics the condition of clinical specimens. Instead of mixing and amplifying DNA extracted from clonal T-cell lines and polyclonal bone marrow cells, we amplified DNA from clonal and polyclonal cells which had been mixed in various ratios before DNA extraction. Polymerase chain reaction in conjunction with denaturing gradient gel electrophoresis is a sensitive and versatile molecular tool for the assessment of clonality of suspect cutaneous lesions. The determination of sensitivity using DNA extracted from premixed cells more closely corresponds to the actual test situation when testing skin samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0625.1997.tb00158.x
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  • 8
    Electronic Resource
    Electronic Resource
    Wann werden empfohlene Mammabiopsien durchgeführt, und was erfährt der mammo- graphierende Arzt darüber? Erfahrungen mit 317 Mammabiopsien aus einem flächendeckenden Qualitätssicherungsvorhaben zur Früherkennungsmammographie (1997)
    Springer
    Der Pathologe 18 (1997), S. 60-66 
    Details
    ISSN: 1432-1963
    Keywords: Schlüsselwörter Histopathologie der Mamma ; Dokumentation ; Qualitätssicherung ; Mammographie ; Key words Pathology ; Breast-cancer ; Quality assurance ; Reporting ; Mammography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In a regional quality assurance project for screening mammography (German Mammography Study), 27 335 women were screened in 40 participating, office-based mammography units from 1990–1992. Screening led to 317 biopsies with a positive predictive value of 0.33. All biopsy documentation available to the mammography physicians was analysed with a view towards biopsy interval and completeness of information fed back to the Mx physicians. Biopsy recommendations were acted upon in 29 % of cases within 2 weeks. With the exception of the dignity Mx physicians were incompletely informed about biopsy results. The surgical procedure was known in the doctors' offices in 62 % of the cases. Specimen radiographies were not done regularly. A pathology report was available overall in 42 of 106 malignant cases, respectively. With the exception of the histological diagnosis itself, no variable mentioned in the reports was documented completely. Only one third of the physicians received such reports routinely. Fail-safe information are requested by Mx physicians and can help them to better target biopsy recommendations. A (regional) quality assurance center should be made responsible to analyse the flow of information in mammography screening, to fill in gaps and to speed up professional cooperation.
    Notes: Zusammenfassung Im Rahmen eines Projekts zur flächendeckenden Erprobung von Qualitätssicherungsmaßnahmen für die Früherkennungsmammographie (Deutsche Mammographie-Studie) wurden 1990–1992 27 335 Screeningmammographien von 40 Praxen in 2 Regionen durchgeführt. Bei 317 Patientinnen wurden Biopsien durchgeführt (positiver Prädiktionswert: 33 %). Die gesamte Dokumentation, die den mammographierenden Ärzten vorlag, wurde mit der Frage analysiert, wie frühzeitig empfohlene Biopsien durchgeführt wurden und welche Informationen wie vollständig an die mammographierenden Ärzte zurückliefen. Eine mammographisch indizierte operative Intervention wurde in 29 % der Fälle innerhalb von 2 Wochen durchgeführt. Das Biopsieergebnis erreichte die veranlassenden Ärzte nur unvollständig. Lediglich die Dignität der Befunde ließ sich in allen Fällen feststellen. Das Operationsverfahren war in 62 % der Fälle in der mammographierenden Praxis bekannt. Präparatradiographien wurden nicht regelmäßig durchgeführt. Ein Pathologiebericht lag bei nur 42 der 106 malignen Fälle vor. Mit Ausnahme der histologischen Diagnose war keines der darin enthaltenen Merkmale durchgängig vollständig dokumentiert. Nur ein Drittel der mammographierenden Ärzte erhält routinemäßig Kopien der Pathologieberichte. Gesicherte Querinformation wird von den mammographierenden Ärzten gewünscht und kann ihnen helfen, Biopsieindikationen gezielter zu stellen. Die Verantwortung, den Informationsfluß im mammographischen Screening transparent zu machen, Lücken zu schließen und die Zusammenarbeit der Leistungserbringer zu beschleunigen, sollte einem (regionalen) Qualitätssicherungs-Zentrum übertragen werden.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002920050197
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  • 9
    Electronic Resource
    Electronic Resource
    Erfolge und Komplikationen der rTPA-Behandlung am vorderen Augenabschnitt (1997)
    Springer
    Der Ophthalmologe 94 (1997), S. 50-52 
    Details
    ISSN: 1433-0423
    Keywords: Key words rTPA ; Fibrin ; Eye ; Anterior segment ; Complications ; Schlüsselwörter rTPA ; Fibrin ; Auge ; Vorderabschnitt ; Komplikationen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Seit einigen Jahren wird Gewebeplasminogenaktivator (rTPA) intraokular zur Behandlung persistierender Fibrinmembranen eingesetzt, ohne daß bisher nennenswerte Komplikationen beschrieben wurden. Wir berichten über unsere eigenen Erfahrungen beim Einsatz von rTPA im vorderen Augenabschnitt bei 25 Patienten. Über eine Parazentese wurden komplikationslos jeweils 25 µg rTPA (Actilyse, Dr. Karl Thomae GmbH) in die Vorderkammer gespritzt. Ein Rückgang des Fibrins war – wenn auch bei einigen Augen nur allmählich – in 21 Fällen zu verzeichnen. Als postoperative Komplikationen traten 2mal eine (beherrschbare) Nachblutung und 2mal eine irreversible oberflächliche Hornhauttrübung auf. Die Behandlung einer Fibrinmembran des vorderen Augenabschnitts mit rTPA stellt in vielen Fällen eine sinnvolle Ergänzung der lokalen Steroidgabe dar. Beunruhigend ist für uns jedoch das Auftreten von irreversiblen Hornhautkomplikationen, deren Pathogenese wir uns derzeit noch nicht erklären können. Aufgrund des eindeutigen zeitlichen Zusammenhangs müssen wir jedoch von einer kausalen bzw. toxischen Wirkung des rTPA selbst oder einer der Lösungskomponenten ausgehen.
    Notes: Recombinant tissue plasminogen activator (rTPA) is commonly used in patients with myocardial infarction. Recently, it has also been applied intraocularly to dissolve post-operative fibrin with no serious complications being reported so far. In this study we describe our own experience with rTPA in 25 patients with persisting fibrinous membranes in the anterior segment. rTPA (Actilyse, Dr. Karl Thomae GmbH) was given in a single dose of 25 µg and injected into the anterior chamber via a paracentesis. We did not encounter any complications during the injection of rTPA. In 21 eyes fibrin could be reduced significantly, albeit sometimes only slowly. In 13 patients, the membrane had dissolved almost completely by the following day. In contrast, no success was observed after glaucoma surgery (2 eyes) and in chronic iritis (1 eye), or when fibrin mixed with blood was treated (1 eye). There were two (controllable) post-operative hemorrhages (rTPA after vitrectomy, and for fibrin/blood after cataract surgery). In addition, we noted 2 cases of irreversible superficial corneal clouding (rTPA after cataract surgery). We conclude that injection of rTPA can be a useful addition to steroid treatment in selective cases of persisting fibrin in the anterior segment. Long-standing membranes, however, are unlikely to be dissolved. Care should also be taken and rTPA be avoided when there is evidence of recent bleeding. Most worrying to us were the corneal complications that we cannot explain to date. With regard to the definite time correlation we feel that rTPA or one of the solution components might be the cause of this unusual feature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003470050084
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  • 10
    Electronic Resource
    Electronic Resource
    Transduction of antibiotic resistance markers among Actinobacillus actinomycetemcomitans strains by temperate bacteriophages Aaφ23 (1997)
    Springer
    Cellular and molecular life sciences 53 (1997), S. 904-910 
    Details
    ISSN: 1420-9071
    Keywords: Key words.Actinobacillus actinomycetemcomitans; temperate bacteriophage; transduction; antibiotic resistance; periodontitis.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Actinobacillus actinomycetemcomitans (Aa) strain ST1 carries the tetracycline (Tc) resistance transposon Tn916 and the Aaφ ST1 prophage, which is closely related to temperate bacteriophage Aaφ23. High titre phage preparations were obtained from this strain by mitomycin C induction and were used to transduce the TcR determinant to the TcS recipient strains ZIB1001 and ZIB1015 (MIC 2 μg Tc/ml). TcR transductants (MIC ≥ 32 μg Tc/ml) were detected at frequencies of 3 × 10−6 to 5 × 10−8 per pfu. All TcR transductants examined contained the entire Tn916 inserted at several different locations within the Aa genome. They appear to have resulted from generalized transduction. In addition both bacteriophages, Aaφ23 and AaφST1, were capable of transducing the chloramphenicol (Cm) resistance marker of plasmid pKT210 (transduction frequencies of 2 × 10−5 to 3 × 10−7 per pfu) to the recipient strain ZIB1001 (MIC 8 μg Cm/ml). Eleven CmR ZIB1001 transductants (MIC ≥ 100 μg Cm/ml) studied carried a plasmid indistinguishable from pKT210 by restriction analyses. In view of the high prevalence of this phage family, and the increasing use of tetracycline in periodontitis therapy, these findings may have clinical importance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000180050109
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