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121.
We study the adiabatic time evolution of quantum resonances over time scales which are small compared to the lifetime of the
resonances. We consider three typical examples of resonances: The first one is that of shape resonances corresponding, for
example, to the state of a quantum-mechanical particle in a potential well whose shape changes over time scales small compared
to the escape time of the particle from the well. Our approach to studying the adiabatic evolution of shape resonances is
based on a precise form of the time-energy uncertainty relation and the usual adiabatic theorem in quantum mechanics. The
second example concerns resonances that appear as isolated complex eigenvalues of spectrally deformed Hamiltonians, such as
those encountered in the N-body Stark effect. Our approach to study such resonances is based on the Balslev-Combes theory
of dilatation-analytic Hamiltonians and an adiabatic theorem for nonnormal generators of time evolution. Our third example
concerns resonances arising from eigenvalues embedded in the continuous spectrum when a perturbation is turned on, such as
those encountered when a small system is coupled to an infinitely extended, dispersive medium. Our approach to this class
of examples is based on an extension of adiabatic theorems without a spectral gap condition. We finally comment on resonance
crossings, which can be studied using the last approach. 相似文献
122.
Aurelien Drezet 《Pramana》2007,68(3):389-396
In a paper by Home and Agarwal [1], it is claimed that quantum nonlocality can be revealed in a simple interferometry experiment
using only single particles. A critical analysis of the concept of hidden variable used by the authors of [1] shows that the
reasoning is not correct.
相似文献
123.
124.
We use different determinantal Hartree-Fock (HF) wave functions to calculate true variational upper bounds for the ground
state energy of N spin-half fermions in volume V
0, with mass m, electric charge zero, and magnetic moment μ, interacting through magnetic dipole-dipole interaction. We find that at high
densities when the average interparticle distance r
0 becomes small compared to the magnetic length r
m ≡ 2mμ2/ħ2, a ferromagnetic state with spheroidal occupation function n
↑(), involving quadrupolar deformation, gives a lower upper bound compared to the variational energy for the uniform paramagnetic
state or for the state with dipolar deformation. This system is unstable towards infinite density collapse, but we show explicitly
that a suitable short-range repulsive (hard core) interaction of strength U
0 and range a can stop this collapse. The existence of a stable equilibrium high density ferromagnetic state with spheroidal occupation
function is possible as long as the ratio of coupling constants Γcm ≡ (U
0
a
3/μ2) is not very small compared to 1.
相似文献
125.
In this study, nanoparticle emission of TiO2 nanopowder coated on different substrates including wood, polymer, and tile, was evaluated in a simulation box and measured
with a Scanning Mobility Particle Sizer (SMPS) for the first time. The coating process for the substrate followed the instructions
given by the supply company. In the simulation box, UV light, a fan, and a rubber knife were used to simulate the sun light,
wind, and human contacting conditions. Among the three selected substrates, tile coated with TiO2 nanopowder was found to have the highest particle emission (22 #/cm3 at 55 nm) due to nanopowder separation during the simulation process. The UV light was shown to increase the release of particle
below 200 nm from TiO2 nanopowder coating materials. The results show that, under the conditions of UV lamps, a fan and scraping motion, particle
number concentration or average emission rate decreases significantly after 60 and 90 min for TiO2/polymer and TiO2/wood, respectively. However, the emission rate continued to increase after 2 h of testing for TiO2/tile. It is suggested that nanoparticle emission evaluation is necessary for products with nanopowder coating. 相似文献
126.
Václav Štengl Snejana Bakardjieva Natalie Murafa Eva Večerníková Jan Šubrt Vladimír Balek 《Journal of nanoparticle research》2007,9(3):455-470
A new method for preparation of titania nanowires with diameter around 10 nm and length up to 2–3 μm is described. The precursor
was prepared from sodium titanate by adding ethylene glycole (EG) and heating at temperature of 198°C for 6 h under reflux.
The sodium titanate glycolate formed by this way aggregated into 1D nanostructures and was subsequently transformed into titania
glycolate during a chemical treatment with 98% sulfuric acid. Titania nanowires with variable amount of anatase and rutile
were prepared by heating to temperatures in the range 350–1000°C. The precursor as well as titania based samples were characterized
by X-ray diffraction, Infrared spectroscopy, Scanning electron microscopy, High resolution transmission microscopy, Thermogravimetry,
Differential thermal analysis, Evolved gas analysis and Emanation thermal analysis. The nitrogen adsorption/desorption was
used for surface area and porosity determination. The photoactivity of the prepared titania samples was assessed by the photocatalytic
decomposition of 4-chlorophenol in an aqueous slurry under UV irradiation of 365 nm wavelength. 相似文献
127.
In this paper we study the semileptonic decays of the Bc meson in the light-cone sum rule (LCSR) approach. The result for each channel depends on the corresponding distribution amplitude
(DA) of the final meson. For the case of Bc decaying into a pseudoscalar meson, to twist-3 accuracy only the leading twist distribution amplitude is involved if we start
from a chiral current. If we choose a suitable chiral current in the vector meson case, the main twist-3 contributions are
also eliminated and we can consider the leading twist contribution only. The leading twist distribution amplitudes of the
charmonium and other heavy mesons are given by a model approach in a reasonable way. Employing this charmonium distribution
amplitude we find a cross section that is consistent with Belle and BaBar data. Based on this model, we calculate the form factors for various Bc decay modes in the corresponding regions. Extrapolating the form factors to the whole kinetic regions, we get the decay widths
and branching ratios for various Bc decay modes including their τ modes when they are kinematically accessible.
PACS 13.20.He; 13.20.Fc; 11.55.Hx 相似文献
128.
Matteo Biggio Fabio Cavaliere Marco Storace Maura Sassetti 《Annalen der Physik》2014,526(11-12):541-554
This paper is focused on the transient dynamics of an adiabatic nano‐electromechanical system (NEMS), consisting of a nano‐mechanical oscillator coupled to a quantum dot. By numerically solving the nonlinear stochastic differential equation governing the oscillator, the time evolution of the oscillator position, of the dot occupation number and of the current are studied. Different parameter settings are studied where the system exhibits bi‐stable, tri‐stable or mono‐stable behavior on a finite‐time horizon. It is shown that, after a typically long transient, the system under investigation exhibits no hysteretic behavior and that a unique steady state is reached, independently of the initial conditions. The transient dynamics is marked out by one or two well separated characteristic times, depending on the considered case (i.e., mono‐ or multi‐stable). These times are evaluated for a dot on‐resonance or off‐resonance. It turns out that the characteristic time scales are long in comparison to the period of the uncoupled oscillator, particularly at low bias, suggesting that the predicted transient dynamics may be observed in state‐of‐the‐art experimental setups.
129.
F Mazzotti H Benabdelkamel L Di Donna CM Athanassopoulos A Napoli G Sindona 《Journal of mass spectrometry : JMS》2012,47(7):932-939
5-Dimethylamino-1-sulfonyl naphthalene (DNS, commonly referred as dansyl) is a functionality, bearing well-established properties in directing the fragmentation, by mass spectrometry (MS), of the corresponding ionized sulfonylated derivatives. This property is shared also by its labeled analogs. The use of d(0)/d(6) DNS derivatives is now exploited in the application of the well-established isotope dilution mass spectrometric approach in the assay of complex mixtures. A new method for the quantitation of amino acids (AAs) in beverages is therefore presented, which relies on liquid chromatographic separation of their N-dansylated derivatives followed by comparative electrospray tandem MS/MS of the d(0)/d(6) isobaric mixtures. Labeled and unlabeled DNS derivatives of the selected AAs are readily available by microwave-assisted synthetic protocols. The novelty of the method is represented by the use of heavy and light DNS-isotopologue providing suitable reporter groups. Multiple-reaction monitoring has been applied in the assay of AAs in wine, pineapple juice and bergamot juice with good-to-excellent results as proved by both relative standard deviation, lower than 15%, and by the accuracy values in the range 90-110%. 相似文献
130.
Public funding agencies largely support academic research as an effort to stimulate future product commercialization and foster broader societal benefits. Yet, translating research nurtured in academic settings into such outcomes is complex and demands functional interactions between government, academic, and industry, i.e., “triple helix,” organizations within an innovation ecosystem. This article argues that in the spirit of responsible innovation, research funding should build bridges that extend beyond the triple helix stakeholders to connect to peripheral organizations. To support that argument, evidence from agent network analysis gathered from two case studies reveals strong and weak connections, as well as gaps within innovation ecosystems in Switzerland and metropolitan Phoenix, USA. This article offers insights on how innovation ecosystems are aligned or misaligned with responsible innovation. 相似文献