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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3662-3664 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Front-illuminated PtSi–n–Si Schottky barrier photodiodes have been developed for the ultraviolet and vacuum ultraviolet spectral range. Their spectral responsivity was determined in the 120–500 nm spectral range by use of a cryogenic electrical substitution radiometer operated with spectrally dispersed synchrotron radiation. For wavelengths below 250 nm, the spectral responsivity is about 0.03 A/W, comparable to that of GaAsP Schottky photodiodes. Unlike the GaAsP diodes, the new PtSi–n–Si diodes have a spatially uniform response which is virtually stable after prolonged exposure to short wavelength radiation. Even after a radiant exposure of 150 mJ cm−2 at wavelength 120 nm, the relative reduction in spectral responsivity remains below 0.2%. Due to these features, this type of photodiode is a promising candidate for use as secondary detector standard in the ultraviolet and vacuum ultraviolet spectral ranges. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Small cantilevers allow for faster imaging and faster force spectroscopy of single biopolymers than previously possible because they have higher resonant frequencies and lower coefficients of viscous damping. We have used a new prototype atomic force microscope with small cantilevers to produce stable tapping-mode images (1 μm×1 μm) in liquid of DNA adsorbed onto mica in as little as 1.7 s per image. We have also used these cantilevers to observe the forced unfolding of individual titin molecules on a time scale an order of magnitude faster than previously reported. These experiments demonstrate that a new generation of atomic force microscopes using small cantilevers will enable us to study biological processes with greater time resolution. Furthermore, these instruments allow us to narrow the gap in time between results from force spectroscopy experiments and molecular dynamics calculations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 2181-2184 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 386-397 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have studied the ultraviolet laser-induced desorption of NO molecules from an epitaxial film of NiO(100) on Ni(100) for pulse durations of 550 fs and at a photon energy of 3.95 eV. For applied laser intensities up to 450 MW/cm2, the highest intensities employed in this work, a linear dependence of the desorption yield on the laser intensity is observed. A desorption cross section of (1.9±0.3)⋅10−17 cm2 is then derived. The molecules are detected with rovibrational state selectivity by (1+1)-REMPI via the A 2Σ+(v′=0,1,2,3)←X 2Π(v″=0,1,2,3) γ-band transitions. The rotational population distributions are nonthermal, with rotational temperatures of about 290 K at low and of about 770 K at high rotational energies. The relative populations in the 2Π1/2 and 2Π3/2 fine-structure states and of the Λ-doublet states are examined for the given set of (v″,J″) quantum numbers. The vibrational states v″〉0 are significantly populated approaching vibrational temperatures of 3800 K. Velocity distributions of the desorbed molecules are measured for individual rovibrational states. Bimodal distributions with a distinct rotational-translational coupling are observed. Further, molecules desorbing in the excited fine-structure state 2Π3/2 show a higher velocity than those desorbing in 2Π1/2. The results are compared with earlier ones obtained for the same system with nanosecond desorption pulses at hν=6.4 eV. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The filamentous bacterium Streptomyces coelicolor undergoes a complex process of morphological differentiation involving the formation of a dense lawn of aerial hyphae that grow away from the colony surface into the air to form an aerial mycelium. Bald mutants of S. coelicolor, which are blocked in aerial mycelium formation, regain the capacity to erect aerial structures when exposed to a small hydrophobic protein called SapB, whose synthesis is temporally and spatially correlated with morphological differentiation. We now report that SapB is a surfactant that is capable of reducing the surface tension of water from 72 mJ m−2 to 30 mJ m−2 at a concentration of 50 μg ml−1. We also report that SapB, like the surface-active peptide streptofactin produced by the species S. tendae, was capable of restoring the capacity of bald mutants of S. tendae to erect aerial structures. Strikingly, a member (SC3) of the hydrophobin family of fungal proteins involved in the erection of aerial hyphae in the filamentous fungus Schizophyllum commune was also capable of restoring the capacity of S. coelicolor and S. tendae bald mutants to erect aerial structures. SC3 is unrelated in structure to SapB and streptofactin but, like the streptomycetes proteins, the fungal protein is a surface active agent. Scanning electron microscopy revealed that aerial structures produced in response to both the bacterial or the fungal proteins were undifferentiated vegetative hyphae that had grown away from the colony surface but had not commenced the process of spore formation. We conclude that the production of SapB and streptofactin at the start of morphological differentiation contributes to the erection of aerial hyphae by decreasing the surface tension at the colony surface but that subsequent morphogenesis requires additional developmentally regulated events under the control of bald genes.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1572-879X
    Keywords: Methanol synthesis ; zinc-chromium mixed oxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The catalytic behaviour of Zn/Cr mixed oxides with different compositions was investigated as a function of the bulk and surface properties. It was observed that non-stoichiometric spinel-type phases were stable also in the reaction conditions, in which zinc-surface enrichment did not occur. The maximum productivity in methanol was observed for monophasic non-stoichiometric spinel-type samples with a Zn/Cr ratio near to one, whereas the samples richest in zinc, for which a side phase, ZnO also was detected, showed a strong decrease in activity. The catalytic data support the hypothesis that non-stoichiometric spinel is the active phase for the synthesis of methanol on coprecipitated Zn-Cr catalysts.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 16 (1988), S. 1-12 
    ISSN: 1572-9338
    Keywords: Planning systems ; expert systems ; knowledge representation ; inspection plans ; construction plans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract Traditional O.R. systems are compared with problem solving in Artificial Intelligence via Expert Systems. The discussion centers on explicit knowledge representation. The general aspects are illustrated by two planning systems: · LESP 2: A learning system for inspection plan generation · IDA: A system for finding functions and solutions in construction
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Annals of operations research 16 (1988), S. IX 
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Studia logica 47 (1988), S. 181-191 
    ISSN: 1572-8730
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Philosophy
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1433-0431
    Keywords: Key words Cervical spine • Traumatic atlantoaxial instability • Transarticular screw Fixation C1/C2 • Minimally invasive technique ; Schlüsselwörter Halswirbelsäule • Atlantoaxiale Instabilität • Transartikuläre Verschraubung C1/C2 • Minimal-invasive Technik
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Spondylodese C1/C2 mit dorsaler transartikulärer Verschraubung stellt bei traumatischen atlantoaxialen Instabilitäten das Verfahren der Wahl dar. Beim offenem Vorgehen müssen die empfindlichen Weichteile des Nackens bis zum 7. Halswirbel freigelegt werden, um die Bohrmaschine weit genug absenken und die Schrauben steil genug einbringen zu können. Zur Verringerung des Weichteiltraumas wurden deshalb von verschiedenen Autoren eine perkutane Technik angegeben. Wir analysierten die von uns mit beiden Verfahren behandelten Patienten der Jahre 1995–1998, um zu prüfen, ob die perkutane Technik Vorteile bietet. 30 Patienten mit traumatischer sagittaler atlantoaxialer Instabilität wurden von dorsal transartikulär verschraubt. 19mal verwendeten wir die perkutane Technik mit Hilfe des Spezialinstrumentariums von McGuire und Harkey. Anhand der postoperativen Röntgenaufnahmen wurde in der Sagittalebene der Winkel zwischen Axisgrundplatte und Schrauben gemessen; 6–24 Monate nach dem Unfall wurden 26 Patienten nachuntersucht, 4 waren zum Zeitpunkt der Nachuntersuchung verstorben. Der Schraubenwinkel war bei der perkutanen Technik größer als beim offenen Vorgehen. Die Mittelwerte (M) beider Gruppen unterschieden sich um 10 ° (perkutan: M = 73,9 °, offen: M = 63,9 °, t-Test: p = 0,001). Die Operationszeit bei perkutaner Technik war im Schnitt 35 min kürzer (93 zu 128 min, t-Test: p = 0,05). Jeweils 2 Patienten beider Gruppen verstarben aufgrund von Begleitverletzungen oder maligner Erkrankungen. Bei der Nachuntersuchung von 26 Patienten waren alle Spondylodesen radiologisch durchbaut. Die Schraubenlage hatte sich nur in einem Fall mit offener Technik geringfügig geändert. Die Beweglichkeit der HWS war in beiden Gruppen gleich stark eingeschränkt. Die subjektive Beurteilung bezüglich Schmerzfreiheit und Funktion mit Hilfe einer Visualanalogskala und eines speziellen Erfassungsbogens ergab Vorteile zugunsten der Gruppe mit perkutaner Technik (z. B.: Schmerzfreiheit: 43 (perkutan) zu 39 (offen) Punkte, t-Test: p = 0,05). Vor der Verletzung hatten die Patienten beider Gruppen vergleichbare Scores aufgewiesen. Die weichteilschonende, perkutane Technik der transartikulären Verschraubung C1/C2 unter Verwendung eines Spezialinstrumentariums erlaubt eine bessere und einfachere Schraubenplazierung. Dies führt auch zu einer kürzeren Operationszeit und – vermutlich durch geringere Schädigung der Nackenmuskulatur – zu besseren subjektiven Ergebnissen. Die Methode besitzt besonders große Vorteile bei solchen Patienten, die nur eine temporäre Stabilisierung des C1/C2-Komplexes ohne Fusion benötigen.
    Notes: Summary For posttraumatic atlantoaxial instabilities posterior transarticular screw fixation according to Magerl represents the treatment of choice. In order to be able to insert the screws steep enough the soft tissues of the neck have to be dissected down to C7. Several authors therefore described a percutaneous technique. We analysed 30 patients with a sagittal atlantoaxial instability treated with one of both methods between the years 1995 and 1998 to detect amny differences of either technique. In 19 cases we used a modified percutaneous technique with special instruments as has been published by McGuire and Harkey. On lateral plain films the angle between the screws and the lower endplate of C2 was measured. 6 to 24 months after the accident 26 patients could be seen clinically and controlled radiologically, 4 patients had died in the meanwhile. The angle of the screws were significantly different with 10 degrees (percutaneous group 73,9 degrees, open group 63,9 degrees, p = 0,001). Time needed for the operativ procedure averaged 35 minutes shorter with the canulated technique (93 to 128 minutes, p = 0.05). All posterior fusions had healed radiologically. Active motion of the c-spine was restricted in both groups equally. We checked subjective criteria concerning pain and function with a visual analog scale and a special score. With these instruments advantages for the percutaneous procedure could be found (freedom of pain 43 points (percutaneous) versus 39 points (open), p = 0.05). We conclude that the soft tissue preserving percutaneous technique of screw application for C1/C2 posterior fusion allows for a better and easier placement of screws. It also leads to a shorter operating time and better subjective results. The method offers particularly advantages in cases where only a temporary satbilization of the C1/C2 complex without a regular fusion is needed.
    Type of Medium: Electronic Resource
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