Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 226-228 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: New features of the nanoscale structure of amorphous (a)-Si produced by ion-implantation-induced amorphization of crystalline (c)-Si have been determined by the technique of small-angle x-ray scattering (SAXS). Si ion energies up to 17 MeV were used to generate a thick amorphous layer (8 μm) on a c-Si wafer to enable the SAXS measurements. As-implanted and thermally annealed (up to 540 °C) a-Si were studied. No nanovoids were detected within a sensitivity of 0.1 vol %, but the atomic-scale structure produced a measurable diffuse scattering signal that decreased with increasing anneal temperatures. These measurements show that the known density deficit of 1.8% in a-Si relative to c-Si cannot be due to voids and that a-Si is homogeneous on nm length scale. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The base current of AlGaAs/GaAs heterojunction bipolar transistor subjected to a long burn-in test often exhibits an abnormal characteristic with an ideality factor of about 3, rather than a normal ideality factor between 1 and 2, in the midvoltage range. We develope an analytical model to investigate the physical mechanisms underlying such a characteristic. Consistent with the finding of an experimental work reported recently, our model calculations show that the recombination current in the base has an ideality factor of about 3 in the midvoltage range and that such a current is responsible for the observed abnormal base current in heterojunction bipolar transistor after a long burn-in test. Post-burn-in data measured from two different heterojunction bipolar transistors are also included in support of the model. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3839-3850 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase and composition depth distributions of a low-energy (0.7 keV), high-flux (2.5 mA/cm2) N implanted fcc AISI 304 stainless steel held at 400 °C have been investigated by step-wise Ar+ beam sputter removal in conjunction with conversion electron Mössbauer spectroscopy and x-ray diffraction (XRD). A metastable, fcc, high-N phase (γN), with both magnetic and paramagnetic characteristics, was found to be distributed in the N implanted layer generated by the low-energy, elevated temperature, implantation conditions. The magnetic γN was found to be ferromagnetic and was distributed in the highest N concentration region of the implanted layer (the top 0.5 μm) while the paramagnetic γN becomes predominant below 0.5 μm, where the N content is only slightly lower. The ferromagnetic state is linked to large lattice expansions due to high N contents (∼30 at.%) as determined by XRD and electron microprobe. The relatively uniform XRD N distribution to a depth of ∼1 μm suggests a sensitive dependence of the magnetic γN phase stability on N concentration and degree of lattice expansion. The XRD results also show that the N contents and depths depend on the polycrystalline grain orientation relative to the ion beam direction. The N was found to diffuse deeper in the (200) oriented polycrystalline grains compared to the (111) oriented grains and the N contents were significantly higher in the (200) planes relative to the (111) planes. The effect of compressive residual stresses (∼2 GPa) is considered. The scanning electron microscopy (SEM) analysis reveals quite clearly the uniform nature of the γN layers with a reasonably well defined interface between the γN layer and the substrate, suggesting uniform N contents with uniform layer thicknesses within a given grain. However, they also show significant variations in the γN layer thickness from one grain to the next along the N implanted layer, clearly supporting the XRD findings of the variation in N diffusivity with grain orientation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-0894
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract  As a part of the Atmospheric Model Intercomparison Project (AMIP), the behaviour of 15 general circulation models has been analysed in order to diagnose and compare the ability of the different models in simulating Northern Hemisphere midlatitude atmospheric blocking. In accordance with the established AMIP procedure, the 10-year model integrations were performed using prescribed, time-evolving monthly mean observed SSTs spanning the period January 1979–December 1988. Atmospheric observational data (ECMWF analyses) over the same period have been also used to verify the models results. The models involved in this comparison represent a wide spectrum of model complexity, with different horizontal and vertical resolution, numerical techniques and physical parametrizations, and exhibit large differences in blocking behaviour. Nevertheless, a few common features can be found, such as the general tendency to underestimate both blocking frequency and the average duration of blocks. The problem of the possible relationship between model blocking and model systematic errors has also been assessed, although without resorting to ad-hoc numerical experimentation it is impossible to relate with certainty particular model deficiencies in representing blocking to precise parts of the model formulation.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-2072
    Keywords: Nefazodone ; Paroxetine ; Sleep polysomnogram ; Serotonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the effect of acute (1 day) and subacute (16 days) administration of the new antidepressant, nefazodone (400 mg daily), and the selective serotonin re-uptake inhibitor (SSRI), paroxetine (30 mg daily), on the sleep polysomnogram of 37 healthy volunteers using a random allocation, double-blind, placebo-controlled design. Compared to placebo, paroxetine lowered rapid eye movement (REM) sleep and increased REM latency. In addition, paroxetine increased awakenings and reduced Actual Sleep Time and Sleep Efficiency. In contrast, nefazodone did not alter REM sleep and had little effect on measures of sleep continuity. We conclude that in contrast to typical SSRIs, nefazodone administration has little effect on sleep architecture in healthy volunteers.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1432-2072
    Keywords: Key words 5-HT1A receptor ; Gepirone ; Paroxetine ; Nefazodone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Animal experimental studies suggest that the therapeutic effect of selective serotonin re-uptake inhibitors (SSRIs) may involve neuroadaptive changes in pre- and post-synaptic serotonin1A (5-HT1A) receptors. We used the endocrine and hypothermic responses to the 5-HT1A receptor agonist, gepirone (20 mg orally), to assess 5-HT1A receptor sensitivity in 37 healthy male volunteers who were studied before and following random double-blind, allocation to treatment with paroxetine, nefazodone or placebo for 17 days. Following antidepressant drug treatment, hypothermic responses to gepirone were markedly decreased by paroxetine but only slightly diminished by nefazodone. Paroxetine also lowered the growth hormone and cortisol responses to gepirone. There was no change in either hypothermic or endocrine response following placebo treatment. Our results suggest that paroxetine treatment produces a striking attenuation of measures of both pre- and post-synaptic 5-HT1A receptor function. Nefazodone appears to decrease the sensitivity of 5-HT1A autoreceptors to some extent and this effect may contribute to its antidepressant activity.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1432-2161
    Keywords: Key words Polytomography ; Computed tomography ; Conventional tomography ; Fractures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Objective. To compare polytomography (PT) and computed tomography (CT) for visualizing fractures and arthrodeses, with and without metal hardware, to determine whether CT could adequately replace PT. Design and patients. An ex vivo bovine model containing fractures in three planes, reduced with metal hardware, was created to compare fractures using PT and CT. The radiation dose at the skin surface was calculated for both examinations. For in vivo assessment, images of 14 patients who underwent both PT and CT (15 fractures, five arthrodeses) were coded, sorted, and independently read by four musculoskeletal radiologists. They rated the degree of certainty of their assessment. Time factors for patients and personnel and financial costs were also compared. Results. In the ex vivo model the fractures were well seen on both PT and CT. The radiation dose was higher for PT than for CT. In vivo, the degree of certainty in assessment of fractures and arthrodeses was higher for PT than CT in studies in which metal hardware was present, but there was no significant difference in studies without metal hardware or in the combined (with and without hardware) studies. The patient’s and technologist’s time required to perform a PT examination was greater than that for CT. Conclusion. In the assessment of fractures and arthrodeses containing metal hardware, PT is recommended. For studies without hardware, CT is equivalent and can replace PT.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructures of two sets of hydrogenated amorphous silicon–germanium (a-Si1−xGex:H) alloys prepared by the plasma-enhanced, chemical-vapor-deposition technique with and without hydrogen dilution of the source gases (silane and germane) have been analyzed by small-angle x-ray scattering (SAXS), infrared vibrational spectroscopy, and flotation density measurements. Optoelectronic properties of codeposited films have also been characterized. Hydrogen dilution suppresses dihydride/polyhydride formation, reduces bonded H content, and reduces the SAXS-detected microstructure for x(approximately-greater-than)0. Studies of anisotropy in the SAXS intensity indicate an increased amount of oriented microstructure as Ge is added, consistent with a trend toward columnarlike growth in both undiluted and hydrogen-diluted films, but the diluted films have a significantly reduced degree of such oriented microstructure. The improvement in the microstructure of a-Si1−xGex:H films by H2 dilution correlates with concomitant improvement of optoelectronic properties. The modification of microstructure due to H2 dilution of the source gases is discussed in terms of growth mechanisms of alloy films. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The specialized technique of radio-frequency-induced collapse of Mössbauer spectra combined with conventional Mössbauer spectroscopy, x-ray diffraction (XRD), small-angle x-ray scattering (SAXS), and differential scanning calorimetry (DSC) are used to investigate in detail the magnetic and structural properties of the two magnetic materials Fe81Zr7B12 and Fe79Zr7B12Cu2. Thermal treatments to convert the as-quenched, fully amorphous state into mixtures of nanocrystalline and amorphous states and the effect of the small Cu addition were of primary interest due to the improved magnetic behavior in the mixed state. DSC shows that the Cu leads to a lowering of the onset temperature for formation of the nanocrystalline phase and also to an increase in the range of temperatures over which this phase forms. XRD and Mössbauer data show the nanoscale phase to be bcc Fe and the Mössbauer spectral parameters demonstrate it to be essentially pure Fe (i.e., with little or no Zr, B, or Cu substitutional impurities). The electron density contrast between the amorphous matrix and the bcc Fe permits the detection of the Fe grains by SAXS and significant volume fractions with sizes of only 2.8–8 nm are shown to exist. Larger sizes are also present as demonstrated by the XRD and Mössbauer data and a bimodal size distribution is suggested. The Mössbauer experiments in which the radio-frequency-induced effects (rf collapse and rf sidebands) are used, allows the nanocrystalline bcc phase to be distinguished from magnetically harder microcrystalline α-Fe. The complete rf collapse of the magnetic hyperfine structure occurs only in the amorphous and nanocrystalline phases and is suppressed by the formation of larger grains. The rf sidebands disappear when the nanocrystalline phase is formed, revealing that magnetostriction vanishes. The rf-Mössbauer studies are shown to be particularly sensitive to magnetic softness of the material in that large changes in the spectra are observed for applied field changes as small as 2 Oe. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7757-7762 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In previous work we reported that the magnetoresistance of Fe/Cr multilayers can be increased by annealing the films at moderate temperatures, which increases the spin-dependent scattering of the conduction electrons. Here we present Mössbauer data that demonstrate that the structural effect of annealing is to promote Cr interdiffusion into the bulk of the iron layers rather than short scale intermixing at the interfaces. We have also investigated the effect of increasing the asymmetric scattering by adding chromium to the iron in Fe/Cr multilayers. The additional Cr was either alloyed with the Fe in compositions ranging from 1.5% to 50% Cr in Fe, or concentrated into 1 or 2 A(ring) layers embedded at various positions in the Fe. We report enhanced room-temperature magnetoresistance of up to 11.4% in sputter-deposited Fe/Cr multilayers when the Fe layers are doped with 20% Cr. The maximum magnetoresistance observed for samples with embedded Cr layers was 10.5%. In comparison, the magnetoresistance was 7.5% in a similar, undoped sample. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...