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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 4214-4222 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new simplified model is proposed to mimic some properties of the glass transition. The physical system undergoing glass transition is modeled as Brownian particle diffusing in one- or two-dimensional space with obstacles. In one dimension obstacles are points which cannot be crossed by Brownian particles, in two dimensions obstacles are randomly distributed sections of straight lines which are impenetrable for the diffusing particle. The obstacles have a finite lifetime τ. After time τ the obstacle disappears and reappears in some new random position. In another modification of the model the obstacle barrier can be opened for short time and then closed again. Both cases are studied for one-dimensional diffusion, while in two dimensions only the first modification of the model is considered. The main feature of the model is that the mean lifetime of obstacles τ is connected with the diffusion coefficient of the Brownian particle through the coupling equation Dτ=K, with K being the coupling constant. This idea is borrowed from the theory of reptations in polymer liquids. Both analytical calculations and results of computer simulations are presented. The model is shown to reflect some of the features of glass transition. It was found that a slight change in the model, i.e., opening and closing of a barrier in the same position versus transfer of a barrier to a new position, leads to a drastic change in the diffusion kinetics of the system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 566-568 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A dual-gate-controlled single-electron transistor with coupled dot geometry has been fabricated on a silicon-on-insulator structure. Coupled dots are defined by tunable gates which are designed to separately control the tunneling potential barriers to compensate for disorder due to size fluctuation in quantum dots. The Coulomb-blockade phenomena observed in linear and nonlinear transport regimes were found to be enhanced by the multidot coupling. The Coulomb staircase (nonlinear effect) appears more clearly with the increasing number of coupled dots, indicating definite suppression of the inevitable cotunneling process. In the linear regime, the frequency of Coulomb oscillation was able to be tuned by changing the interdot coupling strength. These results indicate that enhancement of the Coulomb blockade and tunability can be achieved through replacing the traditional single dot by gate-controlled multidots in future single-electron devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1905-1907 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Band-gap lowering due only to the cation ordering effect is investigated in InAlAs layers grown on InP by using photoluminescence measurement. Double-crystal x-ray diffraction and Rutherford backscattering measurements confirm that both of the InAlAs epilayers studied, grown at 700 and 750 °C, are lattice matched with InP substrates. Through transmission electron diffraction measurements, it is observed that a CuPt-type ordering structure is formed in the InAlAs layers grown at 700 °C but not in the layers at 750 °C. Photoluminescence measurements at 1.7 K reveal that the band-gap energy of the ordered InAlAs is smaller by 60 meV than that of the unordered InAlAs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Artificial intelligence review 10 (1996), S. 345-368 
    ISSN: 1573-7462
    Keywords: knowledge representation ; hybrid structural and spatial representations ; situated communication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In an experimental setting of mechanical-object assembly, the CODY (“Concept Dynamics”) project is concerned with the development of knowledge representations and inference methods that are able to dynamically conceptualize the situation in the task environment. A central aim is to enable an artificial agent to understand and process natural-language instructions of a human partner. Instructions may build on the current perception of the assembly environment on the one hand, and on the other on the knowledge-based understanding of grouped structures in the developing construct. To this end, a dynamic conceptualization must integrate information not only describing the types of the objects involved, but also their changing functional roles when becoming part of structured assemblies. We have developed an operational knowledge representation formalism, COAR (“Concepts for Objects, Assemblies, and Roles”), by which processes of dynamic conceptualization in sequences of assembly steps can be formally reconstructed. Inferences concern the assertion or retraction of aggregate representations in a dynamic knowledge base, as well as the computation of role changes for individual objects associated herewith. The structural representations integrate situated spatial features and relations, such as position, size, distance, or orthogonality, which are inferred on need from a geometry description of the task environment. The capacity of our approach has been evaluated in a 3D computergraphics simulation environment. 1 A running demonstration of the virtual assembly workbench can be seen in our contribution to the IJCAI-95 Videotape Program, cf. (Cao et al., 1995). 2 Some readers may still want to refer to this “false” propeller as a propeller. This is not the point in our current work. Our point is to provide means for recognizing a propeller that is correctly built according to its definition. Should the right-hand-side assemblage in Fig. 4 be recognizable as a propeller, we could allow for an according “slack” in the routine which evaluates orthogonality. Yet another point is how reference could be established to the right-hand-side assemblage by a description like “the propeller on the right”. This topic concerns future work.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2102
    Keywords: Schlüsselwörter PACS ; Filmlos ; MR ; Key words PACS ; Filmless ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary At our hospital, an average MRI examination comprises 170 images. These examinations were evaluated exclusively on digital reporting systems with two high-resolution monitors for a period of 1 year. A retrospective analysis of this reporting method in comparison with films on a conventional viewing wall was performed with subjective and objective data. Radiologists and technicians were requested to evaluate the system on a subjective scale from 1 to 5 for seven topics (image analysis, inspection, time for reporting, handling, comparison with previous reports, quality of PC laser prints, training period). Moreover, personal interviews were conducted and protocols taken. Patient and image frequency, film costs, data transfer time and amount of system failures were evaluated as objective data. The most important results were: Two thirds of the film checking radiologists prefer the conventional viewing walls over the computer monitors. However, 70% of the residents prefer using the computer monitor for reporting. Seventy percent of the interviewed radiologists considered comparison with former examinations on film very difficult. Digitizing of former MRI examinations was not a convincing method; printing on a standard PC laser printer was considered to yield insufficient quality. The different acceptance between radiologists and residents seems to be related to different experiences. The reduction in film costs (48.6%) will improve further with complete PACS installation in the whole hospital. Data transfer rates are still poor; further improvement of network performance is necessary for convenient work. One whole MRI examination and report could be stored on CD-ROM for a cost of less than 2 euros. This could be a future means of cheap archiving and documentation suitable for viewing on any PC with DICOM III viewer. Images and reports could stay with the patient as in the past.
    Notes: Zusammenfassung Im Durchschnitt werden pro Tag 14,05 Patienten mit durchschnittlich 170 Schichtbildern pro Patient an unserer MRT-Anlage untersucht. Die Befundung dieser Bilder erfolgte über ein Jahr ausschließlich auf digitalen Befundungsstationen, bestehend aus zwei hochauflösenden Monitoren und einer Graphikworkstation. Ein Bildausdruck erfolgte zusätzlich auf einem hochauflösenden Laserpapierdrucker. Auf Grund von subjektiv und objektiv erhobenen Daten wurde ein retrospektiver Vergleich zwischen digitaler Bildschirmbefundung und Filmbefundung am Leuchtkasten durchgeführt. Material und Methode: Befragt wurde aufgrund einer subjektiven Bewertungsskala von 1 bis 5 nach 7 Kriterien. Weiters wurden in Interviews die subjektiven Erfahrungen protokolliert. Objektiv wurde überdies Anzahl und Zeit der Systemausfälle, Filmverbrauch, Untersuchungsfrequenzen, Bildmenge pro Tag sowie Zeitmessungen für Datentransfers gemessen. Ergebnisse: Zwei Drittel der Oberärzte bevorzugten die Leuchtkastenbefundung, 70% der Ärzte in Ausbildung zogen die Befundung auf Bildschirmen vor. 70% der befragten Ärzte sahen als eindeutiger Schwachpunkt des digitalen Befundungssystems den Vorbildvergleich an. Alle befragten Ärzte (n=13) bewerteten die Arbeit mit (auswärtigen) konventionellen MRT-Untersuchungen auf Film und der gleichzeitigen Bildschirmbefundung als besonders mühsam. Das Einscannen von Voruntersuchungen mit Betrachtung am Bildschirm erwies sich als nicht Praxis tauglich, die Dokumentation auf Papierbildern durch PC-Laserausdruck erwies sich als unbrauchbar. Diskussion: Der deutliche Akzeptanzunterschied zwischen Fachärzten und in Ausbildung befindlichen Ärzten ist vermutlich auf die unterschiedliche Vorerfahrung (Vorprägung) zurückzuführen. Die nur 48,6% Reduktion Filmverbrauch werden vermutlich nach einer stärkeren Verbreitung von digitalen Bilddaten verbessert werden. Die tatsächlich erzielten Bildtransferraten liegen derzeit zeitlich weit über den technisch möglichen. Die Optimierungen von Netzwerken und beteiligten Rechnern sind daher dringend erforderlich. Als alternatives Dokumentations- und Ausgabemedium könnte auch die äußerst preiswerte CD-ROM dienen. Sie sind auf jedem gängigen PC-System verwendbar. Das Prinzip, daß Befund und Bilder beim Patienten verbleiben, wäre damit leicht aufrecht zu erhalten.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical microbiology & infectious diseases 14 (1995), S. 1063-1069 
    ISSN: 1435-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A total of 446 sera from 245 patients with primary or secondary infertility, all of whom were examined laparoscopically, 117 patients withChlamydia trachomatis-positive cervical swabs, and 84 control persons (50 obstetric patients and 34 female blood donors) were tested for antibodies toChlamydia trachomatis and toChlamydia pneumoniae with the microimmunofluorescence (MIF) test. MIF test antibody rates were highest in patients with complete tubal occlusion (73%) and in patients with provenChlamydia trachomatis infection (74%), whereas only 9 to 10% of the control group showedChlamydia trachomatis antibodies. Reaction to the 60 kDa antigen ofChlamydia trachomatis, a heat-shock protein (hsp) analogue, has been suggested as a possible marker for the development of chronic sequelae afterChlamydia trachomatis infection. Immunoblot analysis of 222 sera (169 infertility patients, 20 antigen-positive patients, and 33 mothers) showed a significantly higher anti-hsp antibody rate in patients with complete tubal occlusion than in infertility patients with normal fallopian tubes (76% vs. 19%, p〈0.001). The presence of antibodies not only toChlamydia trachomatis but also toChlamydia pneumoniae in the MIF test was associated with a significantly higher rate of anti-hsp antibodies and with complete tubal occlusion. This association did not appear to be due to cross-reactivity betweenChlamydia pneumoniae and Chlamydia trachomatis antibodies in the MIF test.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1439-0973
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In einer offenen, randomisierten Vergleichsstudie wurde die initiale empirische Monotherapie mit Meropenem in einer Dosierung von 3 × 1g täglich verglichen mit Imipenem/Cilastatin in der gleichen Dosierung bei 66 Fieberepisoden von 61 erwachsenen neutropenischen Patienten. 72 Stunden nach Therapiebeginn erhielten noch 25/31 Patienten aus der Meropenem-Gruppe und 24/30 Patienten aus der Behandlungsgruppe mit Imipenem/Cilastatin die usprünglich zugewiesene Initialtherapie (Hauptzielkriterium). Bei Therapieende waren in der Meropenem-Gruppe 18/31 Episoden geheilt oder gebessert gegenüber 18/30 in der Gruppe mit Imipenem/Cilastatin. Weitere 10 Infektionsepisoden, die initial mit Meropenem behandelt wurden, und sechs Infektionsepisoden aus der Vergleichsgruppe konnten erfolgreich behandelt werden, nachdem eine zusätzliche antimikrobielle Substanz verabreicht worden war (Heilung nach Therapiemodifikation). Das zufriedenstellende bakteriologische Ansprechen (Keimelimination sowie vermutete Keimelimination) mit der Initialtherapie Meropenem betrug 9/11 und 14/16 mit Imipenem/Cilastatin. Beide Antibiotika wurden gut vertragen; es wurden jedoch unter Imipenem/Cilastatin mehr Fälle von Übelkeit und/oder Erbrechen registriert (7/33 vs 2/33 unter Meropenem). Die Carbapenem-Antibiotika Meropenem und Imipenem/Cilastatin scheinen geeignet für die empirische Monotherapie bei Fieberepisoden neutropenischer Patienten zu sein. Meropenem erlaubt durch seine offensichtlich bessere Verträglichkeit im Vergleich zu Impienem/Cilastatin auch eine optimale Dosierung bei diesem Patientengut.
    Notes: Summary In a nonblind, randomised, parallel-group study, initial empirical monotherapy with meropenem 1 g intravenously every 8 h was compared to an identical dosage of imipenem/cilastatin for the treatment of 66 febrile episodes in 61 adult neutropenic patients. 25/31 episodes treated with meropenem and 24/30 imipenem/cilastatin-treated episodes were still receiving unmodified therapy at 72 h (primary endpoint); this difference was not statistically significant. By the end of the treatment courses, 18/31 meropenem-treated episodes had responded clinically (cured or improved) compared with 18/30 episodes treated with imipenem/cilastatin. Another ten episodes initially treated with meropenem and six episodes treated with imipenem/cilastatin were cured after an additional antimicrobial agent had been administered (cured with modification). Satisfactory bacteriological responses (eradication plus presumed eradication) at the end of unmodified therapy was 9/11 in the meropenem group and 14/16 in the comparator group. Both regimes were well tolerated; however, there were more reports of nausea and/or vomiting in the imipenem/cilastatin group (7/33 vs. 2/33 in the meropenem group). The carbapenems meropenem and imipenem/cilastatin appear to be suitable agents for empirical monotherapy of febrile episodes in neutropenic patients. Meropenem may be better tolerated than imipenem/cilastatin, allowing optimal dosing in this patient population.
    Type of Medium: Electronic Resource
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