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11.
Rhallabi A. Catherine Y. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1991,19(2):270-277
A transport and reaction model of a low-pressure, high-frequency (13.56 MHz) CH4 plasma used for diamondlike carbon (a -C :H ) deposition was developed. The model includes reactions among four molecular species (CH4, C2 H6, C2H4, and H2), five radicals and atom (CH3, CH2, CH, C2H5, and H), and four ions (CH4+ , CH3+, CH5+, and C 2H5+). It also accounts for the influence of the sticking coefficient of species at the walls. Calculated values of the dissociation degree for several flow rates are in good agreement with experimental measurements made by quadrupole mass spectroscopy. A simple surface-model based on the hydrogen coverage of surface and ion flux and energy at the substrate surface was established. This model permitted the calculation of the deposition rate on the powered electrode as a function of the power applied to this electrode. Good agreement between experimental and calculated growth rates was obtained when CH3, C2H5, and CH2 were assumed to participate in film formation, and when hydrogen removal by ion bombardment with variable energy as a function of the power was included in the model 相似文献
12.
Catherine A. Kennedy 《Solid State Communications》2005,134(4):271-276
In order to investigate the relationship between negative thermal expansion and other thermal properties, the thermal conductivity of the α-phase of ZrW2O8 has been determined from 1.9 to 390 K. In addition, the heat capacity was measured from 1.9 to 300 K. The thermal conductivity of ZrW2O8 is low, glass-like and close to its theoretical minimum value. The phonon-phonon coupling of the highly anharmonic low-frequency modes which are responsible for negative thermal expansion in ZrW2O8 appears to be highly efficient, leading to short phonon mean free paths and exceptionally low thermal conductivity. 相似文献
13.
Francois Golse Benoit Perthame Catherine Sulem 《Archive for Rational Mechanics and Analysis》1988,103(1):81-96
This article deals with a boundary-layer problem arising in the kinetic theory of gases when the mean free path of molecules tends to zero. The model considered here is the stationary, nonlinear Boltzmann equation in one dimension with a slightly perturbed reflection boundary condition. We restrict our attention to the case of hard spheres collisions, with Grad's cutoff assumption. Existence, uniqueness and asymptotic behavior are derived by means of energy estimates. 相似文献
14.
Much of the in vivo research that has been conducted on the health effects of pollutants such as SO2 and NO2 has been concerned with their effects upon lung defense systems, with particular reference to their effect on functional properties of the alveolar macrophage (AM). The lungs are constantly exposed to the external environment with its variable content of irritants and infectious agents. Agents deposited in or below the region of the respiratory bronchioles are phagocytized by the AM. The specific capacity of the AM to perform its task is subject to many factors. Gaseous air pollutants have been shown to affect the functional state of the cells(1). Phagocytosis is an energy dependent process and plasma membrane ATPase has been suggested to act as a mechanoenzyme making phagocytosis possible through the conversion of chemical energy in the form of ATPase to the mechanical energky required for attachement and ingestion (2). Since the bulk of the cellular ATPase activity is located in the plasma membrane of the AM(3) the enzyme is easily accessible to inhaled pollutants. Furthermome, the activity of ATPase and other membrane bound enzymes is well know to be dependent upon the fluidity of membrane lipids. 相似文献
15.
Robin S. McDowell Melvin I. Buchwald Michael S. Sorem Alan G. Robiette Catherine M. Deeley Welf A. Kreiner 《Journal of Molecular Spectroscopy》1985,112(2):363-376
A Fourier transform infrared spectrum of 91% 13CD4 has been recorded between 885 and 1193 cm?1 with a resolution of 0.04 cm?1. The frequencies of 600 lines were measured with an accuracy of ±0.003 cm?1. Of these, approximately 368 are assigned as allowed transitions in ν4, 95 are forbidden ν4 transitions, and 137 belong to ν2; maximum upper state J values are 20 for ν4 and 19 for ν2. The ground state tensor constants Dt, H4t, and H6t were obtained by fitting them to four rotational transitions observed by Kreiner and Opferkuch in the infrared-microwave double-resonance spectrum. An interacting-band analysis of the diad then yields 22 spectroscopic constants for these Coriolis-coupled fundamentals and fits the experimental frequencies with an rms deviation of 0.0055 cm?1 for 432 unblended lines that were assigned unit weight. A ν4P+(12) transition at 943.3812 cm?1, nearly coincident with the 10P(22) emission of the 12C16O2 laser, has been investigated by heterodyne spectroscopy and its detuning (?64 MHz) and absorption coefficient have been determined. Such coincidences may lead to the development of laser analytical techniques for 13CD4, which is a useful nonradioactive atmospheric tracer. 13CD4 transitions that are within 300 MHz of isotopic CO2 laser lines are tabulated for this purpose and for use in double-resonance experiments. 相似文献
16.
Catherine Westfall 《Physics in Perspective (PIP)》2006,8(2):189-213
I explore the fifty-year development of M?ssbauer spectroscopy by focusing on three episodes in its development at Argonne
National Laboratory: work by nuclear physicists using radioactive sources in the early 1960s, work by solid-state physicists
using radioactive resources from the mid- 1960s through the 1970s,and work by solid-state physicists using the Advanced Photon
Source from the 1980s to 2005. These episodes show how knowledge about the properties of matter was produced in a national-laboratory
context and highlights the web of connections that allow nationallaboratory scientists working at a variety of scales to produce
both technological and scientific innovations. 相似文献
17.
Catherine Cordier-Robert Thierry Grosdidier Gang Ji Jacques Foct 《Hyperfine Interactions》2006,168(1-3):951-957
Microstructured (atomized) and nanostructured (milled) Fe60Al40 powders together with their corresponding coatings synthesized by High Velocity Oxy-fuel (HVOF) or Atmospheric Plasma Spray (APS) thermal spraying techniques have been characterized by Mössbauer Spectroscopy (MS) and X-ray Diffraction (XRD). The evolution of the microstructure and the atomic ordering degree in the powders and coatings are discussed at the light of the various processing conditions. The operational correlation between the parameters of the duplex morphology of coatings and the processing parameters is discussed. 相似文献
18.
All-electron full-potential linearized augmented plane-wave calculations of the surface energy, work function, and interlayer spacings of close-packed metal surfaces are presented, in particular, for the free-electron-like metal surfaces, Mg(0 0 0 1) and Al(1 1 1), and for the transition metal surfaces, Ti(0 0 0 1), Cu(1 1 1), Pd(1 1 1), and Pt(1 1 1). We investigate the convergence of the surface energy as a function of the number of layers in the slab, using the Cu(1 1 1) surface as an example. The results show that the surface energy, as obtained using total energies of the slab and bulk from separate calculations, converges well with respect to the number of layers in the slab. Obviously, it is necessary that bulk and surface calculations are performed with the same high accuracy. Furthermore, we discuss the performance of the local-density and generalized gradient approximations for the exchange-correlation functional in describing the various surface properties. 相似文献
19.
Aloysius Soon Joel Wallman Bernard Delley Catherine Stampfl 《Current Applied Physics》2013,13(8):1707-1712
We present a trend study of a large variety of dopants at the cation site in Cu2O (i.e. substituting Cu), focussing largely on the early 3d-, 4d-, and 5d-transition metals (TMs) in which many of them are known to be non-magnetic. We also include s-, sp- and d10-metals for comparison. We find that doping with sp-elements results in zero spin moment while dopants with a partially filled d-band show a stronger tendency to magnetize and 3d-TM dopants exhibit a larger magnetic moment than most of the 4d- and 5d-TM dopants. From this trend study, we also find a correlation between their substitution enthalpy and associated interatomic relaxations. In particular, Ti-doped Cu2O appears to be an interesting system, given its “peculiar” ability to exhibit a spin moment when doped with a non-magnetic substituent like Ti. We also find that the interaction between two doped Ti atoms in Ti2:Cu2O is predominantly antiferromagnetic, and interestingly (and unexpectedly), this interaction rapidly declines as a function of inter-dopant distance, as in the case for the magnetic late-TM dopants like Co2:Cu2O. 相似文献
20.
Davy JL Guigou-Carter C Villot M 《The Journal of the Acoustical Society of America》2012,131(6):4615-4624
The effect of the resilience of the steel studs on the sound insulation of steel stud cavity walls can be modeled as an equivalent translational compliance in simple models for predicting the sound insulation of walls. Recent numerical calculations have shown that this equivalent translational compliance varies with frequency. This paper determines the values of the equivalent translational compliance of steel studs which make a simple sound insulation theory agree best with experimental sound insulation data for 126 steel stud cavity walls with gypsum plaster board on each side of the steel studs and sound absorbing material in the wall cavity. These values are approximately constant as a function of frequency up to 400 Hz. Above 400 Hz they decrease approximately as a non-integer power of the frequency. The equivalent translational compliance also depends on the mass per unit surface area of the cladding on each side of the steel studs and on the width of the steel studs. Above 400 Hz, this compliance also depends on the stud spacing. The best fit approximation is used with a simple sound insulation prediction model to predict the sound insulation of steel stud cavity walls whose sound insulation has been determined experimentally. 相似文献