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  • 1
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract It is shown that an increase in the internal losses beyond the lasing threshold in the lasers based on InGaAsSb/InAsSbP double heterostructures (wavelength range λ=3.0–3.6 µm, temperature T=77 K) causes the current-related shift of the laser mode to shorter wavelengths. This shift is as large as 80 cm−1/A and can explain the broadening of the laser line from 5 to 7 MGz as the pump current increases.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0957-4166
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 1466-1471 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The tip–sample distance in near-field scanning optical microscopy is typically controlled by the shear–force interaction between the laterally vibrating tip and sample. In this article, a mode of shear-force feedback is described in which an additional vertical modulation is introduced. Similar to the tapping mode applied in atomic force microscopy, the modulated shear–force technique deals with problem due to the snap to contact and therefore improves the mapping of soft and ductile materials, such as biological samples and soft polymers. The imaging properties of the modulated shear–force mode is demonstrated on structures of a soft polymer blend. Additionally, the modulated shear–force technique allows a simple comparison between effects in the optical far field and in the optical near field. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1769-1772 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We introduce an improved piezoelectric shear-force feedback system for tip-sample distance control in a scanning near-field optical microscope. A tapered glass fiber is glued into a metal tube and both are integrated in a mounting, sandwiched between two piezosegments. One of the piezoelements excites the fiber tip at mechanical resonance while the other one is used for detection. During surface approach the fiber resonance is damped by shear forces, which is registered by the second piezoelement and used for distance control. The main attractions of this setup are its simplicity, its compactness, and the lack of disturbing light sources. The fiber is easy accessible and tip exchange is simple. With an acceptable fiber amplitude of 5–10 nm (peak to peak) we obtained a topographical resolution of 5 pm/Hz. The geometry also allows the measurement of samples covered with a few millimeters of liquid, which is important for applications in biology and medicine. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 4178-4182 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We show that the use of fiber overtone resonance modes up to 3 MHz for shear-force distance control has two advantages for near-field microscopy. The higher dither frequency allows a shorter feedback loop time delay, which in turn allows scanning speeds of 100 μm/s on a sample with, for example, a 150 nm height variation over a 1 μm distance. Experiments on a hard semiconductor device and on a soft polymer sample demonstrate a factor of 5 improvement in scanning speed when the dither frequency is increased by a factor of 20. The second advantage is a reduction of the minimum lateral force required for height regulation, which is important for soft samples. Modeling the piezoelectric detection system as a harmonic oscillator indicates a factor of 33 increase in lateral force sensitivity when using the third overtone resonance of a typical fiber tip. This result is confirmed experimentally by immersing the tip into water. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 7100-7106 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In our experiments we show, that a contaminating water film is very important for the shear–force distance control in near-field optical microscopy. This is demonstrated at the transition between a hydrophilic glass surface and a hydrophobic Langmuir–Blodgett film of arachidic acid at different relative humidities. This contaminating water film is one, if not the important reason for the damping of an oscillating fiber during surface approach. It is further shown, that the bulk viscosity of water alone cannot be responsible for the observed damping effect. A thickness dependent viscosity of this water film is proposed. These observations can also explain, why the shear–force distance control works on nearly all surfaces at ambient conditions, but fails to work at very low temperatures. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3628-3630 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to apply scanning near-field optical microscopy to life science, it is essential to have an accurate distance feedback that also works on soft biological samples in liquids. In this letter, we report measurements of neuron cells in aqueous solution using an advanced piezoelectrical shear-force detection setup. Simultaneously obtained topographical and fluorescence images are presented, demonstrating a resolution below 100 nm in the optical image. The influence of the water level on the shear-force signal and the interaction between near-field probe and soft organic samples are discussed. Stable feedback in fluids is obtained with tip–sample interaction forces below 100 pN. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Anaesthesia 52 (1997), S. 0 
    ISSN: 1365-2044
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Children with cerebral palsy and severe mental retardation who present for operation may require lower concentrations of inhalational anaesthetics than healthy children. The minimum alveolar concentration (MAC) for halothane was measured in 36 children and adolescents, aged 4–18 years, who underwent orthopaedic surgery. The control group consisted of 12 healthy children (group 1). Children with cerebral palsy and severe mental retardation were allocated to one of two groups: those taking chronic anticonvulsant medication (group 2) (n = 12) and those who did not take any drugs (group 3) (n = 12). The mean (SEM) MAC value for halothane (expressed in volume per cent) was 0.90 (0.02) for healthy children. Children with cerebral palsy had significantly lower MAC values whether they took anticonvulsant drugs or not (0.62 (0.03) and 0.71 (0.10), respectively).
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    International Journal of Mass Spectrometry and Ion Physics 46 (1983), S. 101-102 
    ISSN: 0020-7381
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 99 (1968), S. 2244-2254 
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Abstract Non enzymatic synthesis of penicillins and of hippuric acid is demonstrated by reacting 6-aminopenicillanic acid and glycine, resp., with the appropriate S-acylthioglycolates. In the pH range of 5 to 8 the formation of penicillins is relatively fast and independent of pH. The rate of synthesis of hippuric acid in the pH range of 6 to 10 is slow compared with the rate of penicillin formation but increases as the pH approaches 10. An explanation of these results is given. Attempts to increase the rate of hippuric acid synthesis by the addition of a hippurate-splitting enzyme at different pH values always resulted in lower yields evidently caused by a much faster enzymatic hydrolysis than chemical formation of hippuric acid.
    Notes: Zusammenfassung Es wurde gefunden, daß die Synthese von Penicillinen und von Hippursäure aus den entsprechenden S-Acylthioglykolaten und den Aminoverbindungen 6-Aminopenicillansäure bzw. Glycin auch ohne Anwesenheit eines Enzyms, also auf rein chemischem Weg, erfolgt. Hierbei verläuft die Penicillinsynthese im pH-Bereich von 5 bis 8 relativ rasch und unabhängig vom pH, während die Hippursäuresynthese im pH-Bereich von 6 bis 10 zwar langsam abläuft, aber um so mehr beschleunigt wird, je mehr man sich dem pH-Wert 10 nähert. Eine Erklärung für diese Befunde wird angeführt. Versuche, durch Zugabe eines Enzyms, welches die hydrolytische Spaltung von Hippursäure veranlaßt, die Synthese von Hippursäure zu beschleunigen, zeigten, daß die aus der Reaktion von S-Benzoylthioglykolat und Glycin entstandene Hippursäure stets schneller enzymatisch gespalten als chemisch gebildet wird.
    Type of Medium: Electronic Resource
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