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  • 1
    Title: Approximation theory : in memory of Arum Kumar Varma; 212
    Contributer: Govil, Narendra K. , Mohapatra, R. N. , Nashed, Z. , Sharma, A. , Szabados, J.
    Publisher: New York u.a. :Dekker,
    Year of publication: 1998
    Pages: 517 S.
    Series Statement: Pure and applied mathematics 212
    Type of Medium: Book
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin carbon films have been deposited on polycrystalline tungsten foil as well as field ion microscope (FIM) tips by laser-ion deposition in a high-vacuum environment with an ion extraction voltage of −2 kV. Structural characterization of these films has been carried out by using low-angle x-ray diffraction (XRD) and FIM. The low-angle XRD reveals the formation of an interfacial α-W2C phase. The FIM image indicates the formation of the α-W2C phase on the tungsten tip. X-ray photoelectron spectroscopy has been utilized to reveal that the bonding character in the film is sp3. Further, x-ray-excited Auger electron spectroscopy has also supported the diamondlike nature of the films. The results are discussed, and a sequence of layers deposited on tungsten is suggested in view of the structural match.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1484-1494 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we examine the dynamic response of a magnetoplasma to an external time-dependent current source in the context of electronmagnetohydrodynamics (EMHD). A combined analytic and numerical technique is developed to address this problem. The set of cold electron plasma and Maxwell's equations are first solved analytically in the (k,ω) space. Inverse Laplace and three-dimensional complex Fast Fourier Transform techniques are used subsequently to numerically transform the radiation fields and plasma currents from the (k,ω) space to the (r,t) space. The results show that the electron plasma responds to a time-varying current source imposed across the magnetic field by exciting whistler/helicon waves and forming an expanding local current loop, driven by field-aligned plasma currents. The current loop consists of two antiparallel field-aligned current channels concentrated at the ends of the imposed current and a cross-field Hall current region connecting these channels. The characteristics of the current closure region are determined by the background plasma density, the magnetic field, and the time scale of the current source. The results are applied to the ionospheric generation of extremely low-frequency (ELF) and very low-frequency (VLF) radiation using amplitude modulated high-frequency heating. It is found that contrary to previous suggestions the dominant radiating moment of the ELF/VLF ionospheric source is an equivalent horizontal magnetic dipole. © 1996 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 63 (1992), S. 5784-5793 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Inherent in particle and photon-counting systems is a deadtime period that affects the measured counting distribution. The effects of deadtime on counting distributions in single-channel detectors have been extensively studied. These results, however, are not generally applicable to two-dimensional detectors which measure both spatial and temporal photon event coordinates. Deadtime is attributed to the finite recovery characteristics (which include adjacency effects) in the microchannel plate intensifier part of the system and this process is modeled by introducing concepts of a temporal deadtime extending over a rigid or variable spatial dead area. Novel theoretical analyses are presented to predict the effect of paralyzable and nonparalyzable deadtime on the reduced mean count rate in a 2D imaging array. In the limits where the system resembles a one-dimensional detector, the analytic expressions agree exactly with previously published results. The accuracy of the analyses is examined by comparison with computer simulations. The paralyzable analysis is shown to be accurate at all count rates. The accuracy of the nonparalyzable analysis is excellent over count rates relevant in practical situations, but is in general count rate dependent. An inversion procedure is proposed which is applicable to both the paralyzable and nonparalyzable cases. This procedure allows an "ideal'' incident image to be estimated by correcting for deadtime losses in the "measured'' image. Computer results are presented which demonstrate the effectiveness of this inversion method and thus illustrate an important practical application of the work.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4954-4959 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper a novel mechanism is identified for the generation of gamma ray flashes observed on the Compton Gamma Ray Observatory satellite. During typical cloud to ground lightning flashes, the electromagnetic pulse can create a self-focused whistler wave channel or duct to guide 10–102/cm−3 of ∼1 MeV electrons (formed by static stratified electric field in clouds at 20 km), to a height of about 30 km where these electrons can create the gamma ray flash by bremsstrahlung. This scenario combines the various observational features of lightning-generated electromagnetic pulses and low altitude energetic electrons to provide a viable nonlinear transport mechanism of energetic electrons to the desired altitude of 30 km for conversion into gamma ray flashes. © 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 88 (2000), S. 6861-6867 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A comparative study of ablation plasma plumes originated from single crystal graphite (SCG) and amorphous carbon (a-C) targets during the preparation of diamond-like carbon (DLC) films by KrF excimer pulsed laser deposition (PLD) has been carried out by means of a monochromator equipped with an intensified optical multichannel analyzer. In high vacuum, the emission lines of carbon neutral C and ions of C+, C2+, and C3+ can be observed from both the SCG and a-C plasma plumes. The emission intensity from C atoms increases with laser energy density (EL) increase for both cases. The C2 emission intensity from the SCG plasma plume changes drastically with EL, while that from the a-C plasma plume is almost constant. The C2/C emission intensity ratio for the a-C case decreases with EL increase. As for the SCG case, the C2/C ratio decreases with EL increase up to 3.0 J/cm2, and increases slightly with further EL increase. Nanohardness of the deposited films decreases with the increase of the C2/C emission intensity ratio. It is suggested that for both the SCG and a-C target cases, the C2 molecule in the ablated plasma plume may not play an important role in producing high quality DLC films. It is further proposed that the threshold of laser fluence for the formation of diamond-like character film using KrF excimer PLD is 2.1 J/cm2(0.84×108 W/cm2) for the a-C target and 3.0 J/cm2(1.2×108 W/cm2) for the SCG target. The C2 vibrational temperature of the SCG and the a-C plasma plumes show different features on both the laser energy density and nitrogen pressure dependencies. Through optical emission spectroscopy and Langmuir probe measurements in vacuum and nitrogen background, it is concluded that there are many particles with higher mass in the SCG plasma plume, especially at relatively lower laser energy density below 3.0 J/cm2. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 2868-2870 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple technique for investigating whispering gallery modes in optical fibers is described. Unlike the conventional technique of winding a fiber around a mandrel, a bent fiber is produced simply by inserting it inside a commercial glass tube. The fiber naturally assumes a semicircular shape at the bend. It is shown that the loss spectrum due to whispering gallery modes is insensitive to small variations in the glass tube diameter. The glass tube with the bent fiber inside is used to fabricate a rugged interferometric temperature sensor which can be moved around even during measurements. Application of the technique for quality control is also demonstrated by measuring the variation of fiber buffer properties along the length of fiber. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Blackwell Science Ltd/Inc.
    Wound repair and regeneration 12 (2004), S. 0 
    ISSN: 1524-475X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Delayed wound healing is a common complication of diabetes resulting in significant clinical morbidity. The diabetic wound exhibits impaired cellular infiltration and consequently inadequate granulation tissue formation. Additionally, altered patterns of apoptosis. In this study, we have evaluated the differential gene expression pattern in transgenic diabetic female mice, 5–6 weeks old, in a full thickness cutaneous punch wound model. We assessed the role of matrix metalloproteinases (MMPs) and differential gene expression pattern at 4th, 7th and 11th day post wounding. Supernatants obtained from diabetic wound tissue homogenates were subjected to zymogram analysis. The data showed that MMPs were expressed at higher level by 4th day post wounding, whereas expression of MMPs were down regulated towards the 11th day post wounding suggesting their role during early phase of wound healing.The pathway specific gene array data demonstrated differential regulation of several growth factors, transcription factors and other related genes such as fibroblast growth factors and their receptors, ID3 and restin respectively. The cytokine/extracellular matrix protein osteopontin (OPN), an important component of cellular immunity and inflammation also showed higher expression after 4 days post wounding. The expression of OPN remained at higher level after 11 days post wounding in diabetic mice, whereas the expression were down regulated to basal level in normal wounded animal suggesting that the expression of OPN was concomitant with the extent of healing. Other adhesion molecules such as integrin αV and PECAM-1 were also differentially regulated. Though a single gene may not be solely responsible for any defect or impairment in healing as it is a very tightly controlled and regulated process, however, a detailed study of these gene(s) may shed some light to the delayed healing in diabetic mice. Acknowledgements: (These studies are supported by NIH Grant G174KT.)
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Clinical and experimental dermatology 29 (2004), S. 0 
    ISSN: 1365-2230
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6274-6278 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The wet chemical treatment using SeS2 is an inexpensive and simple method of depositing selenium on GaAs surfaces. This treatment improves the electronic properties of the surface as seen from the increase in photoluminescence intensity. We present our results on surface structural investigations of GaAs(110) surface passivated by SeS2 treatment using atomic force microscopy. Our results show that SeS2 treatment can passivate the GaAs(110) surface forming ordered overlayers on it. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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