排序方式: 共有230条查询结果,搜索用时 15 毫秒
51.
H. Zimmermann E. Richter C. Reichle I. Westphal P. Geggier U. Rehn S. Rogaschewski W. Bleiss G.R. Fuhr 《Applied Physics A: Materials Science & Processing》2001,73(1):11-26
During locomotion, adherently growing cells release highly ordered structures consisting of filaments and patches often dendritically
organised. Such traces can be re-incorporated by the donor cell or disconnected and lost. Here, we present the results of
a three-year research programme into trace formation and structural organisation including the influence of substrate surface
properties. Some phenomena may, ultimately, have medical or technological applications. These include: (i) the deposition
and re-incorporation of cellular material as cells move forward and backward; (ii) the ability of cells to differentiate between
their own and foreign traces; (iii) the presence of receptors in the intact membrane envelope of filaments and patches; and
(iv) the cytoplasmic content of patches. Trace formation is physiologically controlled and a characteristic of many types
of actively migrating higher animal and human cells. Possible applications and perspectives are discussed and the importance
of cell-trace elements as “bionanotubes” and biological submicron compartments of cells is explained.
Received: 5 February 2001 / Accepted: 6 February 2001 / Published online: 23 May 2001 相似文献
52.
E. Vardaci G. La Rana A. Brondi R. Moro A. Principe D. Fabris G. Nebbia G. Viesti M. Cinausero E. Fioretto G. Prete F. Lucarelli E.M. Fiore L. Fiore V. Paticchio P.F. Bortignon 《The European Physical Journal A - Hadrons and Nuclei》1998,2(1):55-60
The α-particle emission from the 28Si+170Er fusion-evaporation reaction at 165 and 185 MeV has been measured and compared with published data relative to the pre-scission
emission in the same reaction. The spectra in the two channels exhibit nearly the same shape in the low energy region, whereas
in the high energy region the spectrum for the fusion-evaporation case features a larger apparent temperature. The interpretation
of the difference in shape between the two decay channels is based on statistical model calculations which account for the
effects due to the different length of the decay chain. Statistical model calculations with standard parameters describe well
the gross features of the alpha particle spectra in the fusion-evaporation channel and the proton spectra in the pre-scission
channel. On the contrary, the model predictions seem to overestimate by ≃2 MeV the emission barrier for the alpha particles
in the pre-fission channel. This effect is ascribed to the larger elongation of the nucleus during the fission process. An
average axis ratio b/a∼ 2 for the emitter is suggested.
Received 29 April 1997 / Revised version 10 September 1997 相似文献
53.
We report results of steel substrates coated with hard amorphous carbon and with diamond films. In order to enhance the adherence to the substrate, steel substrates were pretreated by means of a silicon ion beam. Raman spectroscopy was used to analyze the structure of silicon interface while the elastic recoil detection analysis method was applied to determine their composition and thickness. The a-C adherence to the substrate and hardness were also tested. The diamond films were observed by SEM. 相似文献
54.
A diffusive Hamiltonian flow triggered by a resonant drive is confined to a phase subspace determined by the resonance structure. The diffusion path is found for an arbitrary, possibly nonstationary discrete system by applying generalized Manley-Rowe relations to an extended Hamiltonian. 相似文献
55.
J. Lozano A. Brickman S. Yeninas D. Early J.H. Craig Jr. 《Applied Surface Science》2007,253(6):3066-3071
The adsorption and decomposition of triethylsilane (TES) on Si(1 0 0) were studied using temperature programmed desorption (TPD), high resolution electron energy loss spectroscopy (HREELS), electron stimulated desorption (ESD), and X-ray photoelectron spectroscopy (XPS). TPD and HREELS data indicate that carbon is thermally removed from the TES-dosed Si(1 0 0) surface via a β-hydride elimination process. At high exposures, TPD data shows the presence of physisorbed TES on the surface. These species are characterized by desorption of TES fragments at 160 K. Non-thermal decomposition of TES was studied at 100 K by irradiating the surface with 600 eV electrons. ESD of mass 27 strongly suggests that a β-hydride elimination process is a channel for non-thermal desorption of ethylene. TPD data indicated that electron irradiation of physisorbed TES species resulted in decomposition of the parent molecule and deposition of methyl groups on the surface that desorbed thermally at about 900 K. Without electron irradiation, mass 15 was not detected in the TPD spectra, indicating that the production of methyl groups in the TPD spectra was a direct result of electron irradiation. XPS data also showed that following electron irradiation of TES adsorbed on Si(1 0 0), carbon was deposited on the surface and could not be removed thermally. 相似文献
56.
Lie Symmetrical Perturbation and Adiabatic Invariants of Generalized Hojman Type for Disturbed Nonholonomic Systems 下载免费PDF全文
For a nonholonomic mechanics system with the action of small disturbance, the Lie symmetrical perturbation and adiabatic invariants of generalized Hojman type are studied under general infinitesimal transformations of groups in which the generalized coordinates and time are variable. On the basis of the invariance of disturbed nonholonomic dynamical equations under general infinitesimal transformations, the determining equations, the constrained restriction equations and the additional restriction equations of Lie symmetries of the system are constructed, which only depend on the variables t, qs and q^.s. Based on the definition of higher-order adiabatic invariants of a mechanical system, the perturbation of Lie symmetries for a nonholonomic system with the action of small disturbance is investigated, and the Lie symmetrical adiabatic invariants, the weakly Lie symmetrical adiabatic invariants and the strongly Lie symmetrical adiabatic invariants of generalized Hojman type of disturbed nonholonomic systems are obtained. An example is given to illustrate applications of the results. 相似文献
57.
M. Schädel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):67-74
Superheavy elements have been synthesized and chemically
characterized one-atom-at-a-time up to element 108. Presently, the quest for
identification and investigation of element 112 is one of the hottest topics
in this field. The transactinide elements 104 to 108 are members of group 4
to 8 of the periodic table and element 112 belongs into group 12. For some
of these elements detailed chemical properties have been revealed which show
stunning deviations from simple extrapolations within their respective group
while others exhibit great similarities with their lighter homologues. All
presently known chemical properties of seaborgium (Sg, element 106) — the
heaviest element whose behavior was investigated in aqueous solution — and
hassium (Hs, element 108) were obtained in experiments performed at the GSI
in large international collaborations. Recently, the highly efficient and
very clean separation of Hs was applied for nuclear studies of various Hs
nuclides investigating their cross section and their nuclear decay
properties in the region of the N=162 neutron shell. To overcome certain
limitations of the presently used on-line chemical separations the new
TransActinide Separator and Chemistry
Apparatus (TASCA) — with a gas-filled recoil separator as
a front-end tool — was designed and built at the GSI in a collaborative
effort. Presently in its commissioning phase, TASCA shall be a key
instrument for a big leap into quantitatively and qualitatively new
experiments in the region of superheavy elements. 相似文献
58.
S. Verma J. J. Das A. Jhingan K. Kalita S. Barua K. S. Golda N. Madhavan P. Sugathan S. Nath T. Varughese J. Gehlot S. Mandal S. Ranjit P. K. Sahu B. John B. K. Nayak A. Saxena S. K. Datta R. Singh 《The European physical journal. Special topics》2007,150(1):75-78
Elastic scattering angular distributions have been measured for 7Be + 9Be system at Elab = 17, 19 and 21 MeV in the angular range θcm=26○–58°, and for 7Li + 9Be system at Elab= 15.75, 24 and 30 MeV.
An optical model (OM) analysis of these data have been carried out.
For the 7Li + 9Be system fusion cross sections were obtained at Elab = 15.75, 24 and 30 MeV by measuring the α-evaporation spectra from the compound nucleus at backward angles. The measured
α-evaporation spectra were reproduced by the statistical model calculations and fusion cross sections were extracted therefrom.
The ratios of the experimental fusion cross sections to the total reaction cross sections (obtained form OM analysis) were
found to be rather small. This result suggests that break-up process has a strong influence on fusion process leading to a
reduction in fusion cross section. 相似文献
59.
Stress anisotropy in circular planar magnetron sputter deposited molybdenum films and its annealing effect 总被引:2,自引:0,他引:2
Y.G. Wu E.H. Cao Z.S. Wang J.M. Wei W.X. Tang L.Y. Chen 《Applied Physics A: Materials Science & Processing》2003,76(2):147-152
As part of the program to develop a free-standing thin-film filter for soft X-ray optics application, stress anisotropy in
the molybdenum films deposited by dc circular planar magnetron sputtering were studied by X-ray diffraction (XRD) as a function
of sputtering argon gas pressure over a range of 0.8–1.5 Pa. Surface morphology of the films has been investigated by optical
microscopy and scanning tunneling microscopy (STM). It is found that, for the film deposited at 0.8 Pa pressure, the stresses
are more compressive in the tangential than in the radial direction; the highest compressive stress exists in the center area.
The film deposited at 1.5 Pa pressure has the highest stress anisotropy, and the stresses are less tensile in the tangential
than in the radial direction. Annealing in vacuum is more effective in reducing tensile stress and stress anisotropy in the
tensile stressed film than in the compressively stressed film.
Received: 14 September 2001 / Accepted: 21 January 2002 / Published online: 5 July 2002
RID="*"
ID="*"Corresponding author. Fax: +86-21/6598-6323, E-mail: ygwu@mail.tongji.edu.cn 相似文献
60.