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971.
E. Mathieu Y. Foucher P. Dellamonica J. P. Daures 《Methodology and Computing in Applied Probability》2007,9(3):389-397
In AIDS control, physicians have a growing need to use pragmatically useful and interpretable tools in their daily medical
taking care of patients. Semi-Markov process seems to be well adapted to model the evolution of HIV-1 infected patients. In
this study, we introduce and define a non homogeneous semi-Markov (NHSM) model in continuous time. Then the problem of finding
the equations that describe the biological evolution of patient is studied and the interval transition probabilities are computed.
A parametric approach is used and the maximum likelihood estimators of the process are given. A Monte Carlo algorithm is presented
for realizing non homogeneous semi-Markov trajectories. As results, interval transition probabilities are computed for distinct
times and follow-up has an impact on the evolution of patients.
相似文献
972.
T. Hansel J. Müller C. Falldorf C. von Kopylow W. Jüptner R. Grunwald G. Steinmeyer U. Griebner 《Applied physics. B, Lasers and optics》2007,89(4):513-516
Digital holographic shape measurements using femtosecond laser pulses are reported. For contouring of very fast moving objects,
the simultaneous generation of at least two spectrally separated ultrashort pulses is required. To deliver this particular
spectral signature at high pulse energies, a chirped-pulse Ti:sapphire laser amplifier was modified to emit two spectrally
separated pulses with energies above 1 μJ each. The wavelength separation of these pulses was adjustable within the 50 nm
gain bandwidth, cutting out two distinct wavelength peaks by a variable double-slit assembly in a prism sequence. A Michelson-type
interferometer was employed to perform the two-wavelength contouring. The phases of the holograms and the phase differences
are calculated numerically, which allow us to deduce the contour lines of the topology of the object. The suitability of the
light source for digital holography is demonstrated with contouring of stationary objects and the potential for high-speed
applications is indicated.
PACS 42.40.-i; 42.60.By 相似文献
973.
E. Granot S. Sternklar D. Schermann Y. Ben-Aderet M.H. Itzhaq 《Applied physics. B, Lasers and optics》2006,82(3):359-362
We use the spectral ballistic imaging technique to measure the impulse response of a Fabry–Pérot etalon with less than 0.2 ps
temporal resolution. The results show excellent agreement with the theoretical predictions and negligible noise. Comparison
to the Kramers–Kronig method along with its limitations is also presented.
PACS 42.65.Re; 07.60.Ly; 42.30.Kq 相似文献
974.
C. Guillermier 《Applied Surface Science》2006,252(19):6644-6647
The yield of CN from glycine rises from one CN per projectile impact to two when the sample is covered with a nominally 1 nm thick layer of silver. These yields were obtained for bombardment with Au4004+ projectile with 136 keV impact energy. A multitude of CN-based clusters, e.g. AgxOy(CN)z are produced concurrently. As a result, a total of three CN-based secondary ions are generated per projectile impact. The exceptionally high yield for CN is of interest for biological SIMS. 相似文献
975.
There are many advantages in being able to perform positron annihilation lifetime spectroscopy (PALS) using a variable energy positron beam, the most obvious being the easy identification of different defect types at different depths. The difficulty in conducting variable energy (VE) PALS studies lies in the fact that a “start” signal is required to signal the entry of the positron into the target. Two methods have been used to overcome this problem, namely the bunching technique, which employs radio frequency (RF) cavities and choppers, and secondly the use of secondary electrons emitted from the target. The latter technique is in terms of experimental complexity much simpler, but has in the past suffered from poor time resolution (typically ∼500 ps). In this work, we present a series of computer simulations of a design based on the secondary electron emission from thin C-foils in transmission mode which shows that significant improvements in time resolution can be made with resolutions ∼200 ps being in principle possible. 相似文献
976.
F.A. Fernández-Lima C.R. Ponciano E. Pedrero E.F. da Silveira 《Applied Surface Science》2006,252(23):8171-8177
Experimental results of laser sputtering of cesium and rubidium iodide secondary ions are presented. A TOF mass spectrometer, operating in linear mode, continuous extraction for positive or negative ions, was used for the analysis of (CsI)nCs+, (CsI)nI−, (RbI)nRb+ and (RbI)nI− ion emission as a function of the laser irradiance. Experimental data show that the cluster ion emission yields decrease exponentially with n, for all the laser irradiances applied. Theoretical analysis of the clusters structure was performed using density functional theory at the B3LYP/LACV3P level, for the positive and negative cluster series. A quasi-equilibrium evolution of the clusters is proposed to extract a parameter characteristic of the cluster recombination process: the effective temperature. The hypothesis of the atomic species’ recombination (during the expansion of a high density highly ionized cloud) leading to cluster formation is confirmed to some extent in a second set of experiments: the UV laser ablation of a mixed and non-mixed cesium iodide and potassium bromide targets. These experiments show that the emission yields contain contributions from both the recombination process and from the sample stoichiometry, even for high laser irradiances. 相似文献
977.
This study analyzes the economics of transshipping biomass from truck to train in a North American setting. Transshipment
will only be economic when the cost per unit distance of a second transportation mode is less than the original mode. There
is an optimum number of transshipment terminals which is related to biomass yield. Transshipment incurs incremental fixed
costs, and hence there is a minimum shipping distance for rail transport above which lower costs/km offset the incremental
fixed costs. For transport by dedicated unit train with an optimum number of terminals, the minimum economic rail shipping
distance for straw is 170 km, and for boreal forest harvest residue wood chips is 145 km. The minimum economic shipping distance
for straw exceeds the biomass draw distance for economically sized centrally located power plants, and hence the prospects
for rail transport are limited to cases in which traffic congestion from truck transport would otherwise preclude project
development. Ideally, wood chip transport costs would be lowered by rail transshipment for an economically sized centrally
located power plant, but in a specific case in Alberta, Canada, the layout of existing rail lines precludes a centrally located
plant supplied by rail, whereas a more versatile road system enables it by truck. Hence for wood chips as well as straw the
economic incentive for rail transport to centrally located processing plants is limited. Rail transshipment may still be preferred
in cases in which road congestion precludes truck delivery, for example as result of community objections. 相似文献
978.
D. K. Kuznetsov I. S. Baturin V. Ya. Shur N. Menou C. Muller T. Schneller A. Sternberg 《Physics of the Solid State》2006,48(6):1174-1176
The effect of irradiation with electrons and neutrons and of exposure to synchrotron radiation on cyclic switching of polarization in thin films of lead zirconate titanate Pb(Zr,Ti)O3 (PZT) was studied. It is shown that variations in the shape of switching currents are due to the generation of a spatially nonuniform bound internal field with account for an increase in the rate of bulk screening caused by irradiation. A correlation between structural variations and the evolution of the switching current measured during and after irradiation is established. 相似文献
979.
Phase synchronization in a system of three virtual-cathode microwave oscillators (vircators) simulated by coupled van der Pol oscillators is studied. The phasing dynamics of the vircators is visualized with the phase portraits of the system in the triangular coordinates. Different phasing conditions are found. 相似文献
980.
Photoelectronic spectra of volume samples of molybdenum, tungsten, and rhenium disilicides are theoretically investigated
as functions of the excitation energy (hv = 12–1486 eV) by the method of linearized attached plane waves. The main contribution
to the spectrum at low (hv = 12–52 eV) and very high (hv = 1486 eV) excitation energies is given by the metal d-states, while
the contribution of the Si p-states is dominant at intermediate excitation energies. An analysis of the calculated results
demonstrates that the main peak of the photoelectronic spectra is displaced by 0.2 eV toward the bottom of the valence band
when going from MoSi2 to WSi2; it is displaced by 0.3 eV when going from WSi2 to ReSi1.75.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 75–80, July, 2006. 相似文献