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  • 1990-1994  (105)
  • 1940-1944  (1)
  • 1935-1939  (3)
  • 1925-1929  (3)
  • 1915-1919  (1)
  • 11
    Electronic Resource
    Electronic Resource
    Dissection Following Balloon Angioplasty of Aortic Coarctation: Review of the Literature (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of interventional cardiology 5 (1992), S. 0 
    Details
    ISSN: 1540-8183
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Balloon angioplasty of the coarctation of the aorta can result in intimal or medial or even adventitial dissections as demonstrated by in vitro studies and animal experiments. As a typical sign of stretching of the aortic wall, patients complain of pain during the angioplasty procedure. In the literature, aortic wall rupture and ventricular fibrillation during the procedure are reported. Additional sudden deaths can occur within 40 hours after the procedure. Mortality ranges from 0.1% to 2.5%. By transesophageal echocardiography, monitoring of balloon angioplasty, control of the positioning of the balloon, and control of the results and detection of complications are possible. Intimal as well as medial dissections can be detected with observed healing for intimal but also medial dissections. In order to avoid the patient's discomfort, intraaortic ultrasound will be used in the future, when major methodological improvements are done. Computed tomography demonstrates medial dissections but is not able to visualize intimal dissections. Using computed tomography and magnetic resonance after angioplasty of the coarctation of the aorta, irregularities are described in up to 17% of the patients. For angiography, a low detection rate of medial dissections has to be expected, when not biplane angiographies of the whole thoracic aorta are performend. Medial dissections can be seen, but intimal dissections are missed. In conclusion, a review of the literature demonstrates a high incidence of intimal and medial dissections after angioplasty of the coarctation of the aorta with spontaneous healing in most patients. As is the way with coronary angioplasty, aortic wall ruptures are rare, but stand-by surgery is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8183.1992.tb00414.x
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  • 12
    Electronic Resource
    Electronic Resource
    Infrared electroabsorption modulation at normal incidence in asymmetrically stepped AlSb/InAs/GaSb/AlSb quantum wells (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 92-96 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A normal-incidence modulation mechanism is proposed which uses the Stark effect to induce Γ-L transitions in asymmetrically stepped AlSb/InAs/GaSb/AlSb quantum wells (QWs). A significant feature of this structure is the unusual band alignments which localize two deep wells for the Γ and L bands in adjacent layers, i.e., the Γ-valley minimum is in the InAs while the L-valley minimum is in the GaSb. In contrast to a square QW, where the Stark shifts for both Γ and L subbands are in the same direction, the two step wells for Γ and L valleys in the proposed structure are oppositely biased in the presence of an electric field. Therefore, the first Γ and L subbands move toward each other, making the Γ-L crossover occur more efficiently. Near this point, most of the Γ electrons transfer to the L valleys, where they are allowed to make intersubband transitions under normally incident radiation. As a result, the device switches from being transparent to normal-incidence light to strongly absorbing it. The calculations indicate that excellent on/off ratios can be achieved in this structure operating at T≤150 K with electric fields on the order of ∼100 kV/cm for any infrared wavelength within the range of 3–20 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357065
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    Paper (German National Licenses)
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  • 13
    Electronic Resource
    Electronic Resource
    Interface roughness limited electron mobility in HgTe-CdTe superlattices (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2523-2525 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that interface roughness is the dominant low-temperature scattering mechanism for electrons in HgTe-CdTe superlattices with thin wells. Not only do the experimental mobilities follow the expected d6W dependence, but the observed temperature dependence is accurately reproduced by theory when the treatment of interface roughness scattering is generalized for narrow-gap superlattices. The fits to data yield roughness correlation lengths in the range 60–200 A(ring).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104840
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    Paper (German National Licenses)
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  • 14
    Electronic Resource
    Electronic Resource
    Subpicosecond reflection switching of 10 μm radiation using semiconductor surfaces (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1940-1942 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electromagnetic wave equations for P-polarized 10 μm radiation in a semiconductor with a free-carrier density decreasing exponentially from the surface are solved numerically. The infrared (IR) reflectivity for Brewster angle incidence is then calculated as a function of free-carrier surface density n0. This reflectivity shows a minimum of zero just below and a sharp peak at the value where n0 reaches its critical value. The features are explained with the help of a simple model. The results suggest the feasibility of a subpicosecond IR reflection switch for the case when the surface is irradiated by a 100 fs visible laser pulse. Solutions to the diffusion equation show that ensuing reflectivity decreases to zero in times shorter than 0.5 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105240
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  • 15
    Electronic Resource
    Electronic Resource
    Nonlinear optical properties of molecular beam epitaxy grown Bi1−xSbx (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 336-338 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss the first investigation of Bi1−xSbx as an infrared nonlinear optical material. Nondegenerate four-wave mixing experiments at CO2 laser wavelengths yield a large nonlinearity (χ(3)≈3×10−4 esu) which does not saturate at power densities up to 0.5 MW/cm2. Both the ambient and substrate interfaces of the film are highly reflective and the étalon they form is found to have a large effect on the transmission and reflectivity spectra of the as-grown films. This suggests the possibility that constructive interference of the film's internal optical fields could be used to considerably enhance the nonlinear signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103683
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  • 16
    Electronic Resource
    Electronic Resource
    Higher order electron cyclotron resonances in n-type HgTe-CdTe superlattices (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1781-1783 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Temperature-dependent magneto-optical measurements on an n-type HgTe-CdTe superlattice have been compared to the results of a comprehensive new theory, which fully incorporates the complexities of the unusual superlattice band structure. The theory predicts that higher order cyclotron resonance processes should yield a separate transmission minimum which is distinct from that of the lowest order cyclotron transition, and the data provide an unambiguous confirmation of this prediction. Since the energy gap is near zero, interband transitions are also observed in the same spectral range as the cyclotron resonance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104040
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  • 17
    Electronic Resource
    Electronic Resource
    Computer-controlled system designed to measure photodegradation of photochromic compounds (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 1803-1808 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this paper, we describe a new, entirely computer-controlled apparatus designed for degradation studies of photochromic compounds. Photodegradation can be performed in three different ways using, in addition to the usual flash mode, the cyclic and continuous modes which more closely simulate daylight exposure conditions. In each mode, the "fatigue resistance'' parameter is computed. Moreover, the spectrokinetic parameters of photomerocyanine species can be obtained from the kinetic mode. Due particularly to the fully computer-controlled experimental setup, the between-day reproducibility of the initial absorbance and fatigue resistance determinations are better than 4% and 6%, respectively. Owing to the modular design of the menu-driven software, written in C language, the apparatus is very flexible and easy to use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144014
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  • 18
    Electronic Resource
    Electronic Resource
    High-speed circuits for TE discharge lasers and high-voltage applications (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 839-853 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Pulsed transverse electric (TE) glow discharges used to produce population inversions in gas lasers at 1–20 atm require high-speed, high-voltage, high-current capacitor banks. In this article we first review and compare the circuits in common use to produce the required fast, self-sustained glow discharges in CO2, excimer, and N2 lasers. The parameters and circuit types given will be useful to future designers of pulsed gas lasers to design and to optimize any proposed circuit in order to yield any desired operating conditions and parameters. The n-stage circuit types presented are capacitor-transfer (C-C), L-C inversion, Marx bank, and fourfold L-C inversion, with their double-sided counterparts, and also their transmission-line counterparts, such as the Blumlein circuit. A one-parameter differential equation is developed which describes the general series C-L-R circuit. Electrical pulses measured on various lasers are compared with the differential equation solutions for various bank impedances and load resistances. We then present the design and measurements of a new automatically preionized, double-sided, L-C inversion circuit for an 800-mJ, TE CO2 laser, and compare it to previous systems. Methods to lengthen the discharge pulse, and some novel active mode locking techniques are discussed. We compare the L-C inversion circuit, the fourfold L-C inversion circuit, the conventional Marx bank, and the "double Marx bank'' for lasers and other applications, such as pulsed particle accelerators. Finally, we discuss capacitor bank interconnections, electro-optic probe systems, and various triggering methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144131
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  • 19
    Electronic Resource
    Electronic Resource
    Sb/GaSb heterostructures and multilayers (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1098-1100 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have successfully synthesized heterojunctions and elementary multilayered structures of the semimetal-semiconductor system Sb/GaSb using molecular beam and migration enhanced epitaxies. The study is motivated in part by the potential for producing an indirect narrow-gap semiconductor, in which a confinement-induced positive energy gap in the Sb layers will lead to highly attractive properties for nonlinear optical switches operating in the infrared. One may also be able to exploit the long mean free path in Sb (up to 2 μm) in studying quantum transport phenomena. X-ray diffraction confirms the ordered growth of GaSb/Sb/GaSb multilayers, and field-dependent magnetotransport measurements yield electron and hole mobilities ≥3×104 cm2/V s in Sb thin films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109792
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  • 20
    Electronic Resource
    Electronic Resource
    Nanometer scale fabrication in mercury cadmium telluride using methane/hydrogen electron cyclotron resonance microwave plasmas (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2362-2364 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fabrication of nanometer scale features in the narrow gap, compound semiconductor mercury cadmium telluride has been demonstrated through the application of e-beam lithography and reactive ion etching with an electron cyclotron resonance (ECR) microwave generated methane/hydrogen plasma. The effects of methane concentration, substrate bias, total pressure, and substrate position with respect to the ECR condition on etch rate, anisotropy, and overall etch performance have been examined. The optimized process resulting from these studies has produced the first mercury-based nanostructures consisting of 30–60 nm features with sidewall angles of 88°.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109390
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