Systems of particles interacting with long range interactions present generically ”quasi-stationary states” (QSS), which are
approximately time-independent out of equilibrium states. In this proceedings, we explore the generalization of the formation
of such QSS and their relaxation from the much studied case of gravity to a generic pair interaction with the asymptotic form
of the potential v(r) ∼ 1/rγ with γ > 0 in d dimensions. We compute analytic estimations of the relaxation time calculating the rate of two body collisionality in a virialized
system approximated as homogeneous. We show that for γ < (d − 1/2), the collision integral is dominated by the size of the system, while for γ > (d − 1/2), it is dominated by small impact parameters. In addition, the lifetime of QSS increases with the number of particles
if γ < d − 1 (i.e. the force is not integrable) and decreases if γ > d − 1. Using numerical simulations we confirm our analytic results. A corollary of our work gives a ”dynamical” classification
of interactions: the dynamical properties of the system depend on whether the pair force is integrable or not. 相似文献
This work reports the results of the vibrational corrections and frequency dependence to the first hyperpolarizabilities of the alkali- and alkaline-earth-doped boron nitride nanotubes. The electronic contributions were computed by means of the density functional theory with the M06-2X functional, and the vibrational corrections were calculated using the perturbation theoretical method and the field-induced coordinates methodology. The results for the electronic contribution show that such materials exhibit large first hyperpolarizabilities and electride characteristic. We also show that the distribution of the excess electron, which originates from the doping atoms, plays an important role in the large electronic hyperpolarizabilities (βel). Moreover, our findings strongly indicate that the effect of vibrations on the hyperpolarizabilities can be quite important and can even be much larger than the electronic counterpart. 相似文献
The review presents a parameter switching algorithm and his applications which allows numerical approximation of any attractor
of a class of continuous-time dynamical systems depending linearly on a real parameter. The considered classes of systems
are modeled by a general initial value problem which embeds dynamical systems continuous and discontinuous with respect to
the state variable, of integer, and fractional order. The numerous results, presented in several papers, are systematized
here on four representative known examples representing the four classes. The analytical proof of the algorithm convergence
for the systems belonging to the continuous class is presented briefly, while for the other categories of systems, the convergence
is numerically verified via computational tools. The utilized numerical tools necessary to apply the algorithm are contained
in Appendices A, B, C, D and E. 相似文献
BaMoO4:Eu (BEMO) powders were synthesized by the polymeric precursor method (PPM), heat treated at 800 °C for 2 h in a heating rate
of 5 °C/min and characterized by powder X-ray diffraction patterns (XRD), Fourier Transform Infra-Red (FTIR) and Raman spectroscopy,
besides room temperature Photoluminescence (PL) measurements. The emission spectra of BEMO samples under excitation of 394 nm
present the characteristic Eu3+ transitions. The relative intensities of the Eu3+ emissions increase as the concentration of this ion increases from 0.01 to 0.075 mol, but the luminescence is drastically
quenched for the Ba0.855Eu0.145MoO4 sample. The one exponential decay curves of the Eu3+ 5D0→7F2 transition, λexc = 394 nm and λem = 614 nm, provided the decay times of around 0.54 ms for all samples. It was observed a broadening of the Bragg reflections
and Raman bands when the Eu+3 concentration increases as a consequence of a more disordered material. The presence of MoO3 and Eu2Mo2O7 as additional phases in the BEMO samples where observed when the Eu3+ concentration was 14.5 mol%. 相似文献
It has been possible to perform the simultaneous determination of choline and glucose using the intrinsic fluorescence of
the corresponding enzyme as an analytical signal. This can be done in two ways. First, for low glucose and choline concentrations
(about 0.55 mM and 0.75 μM respectively) two differentiated signals, without mutual interference, are obtained for both analytes
in the same measurement. Second, when glucose and choline concentrations are higher, a new model has been designed which permits
the concentrations to be accurately determined in samples containing from 0.55 mM to 3.75 mM glucose and from 0.75 μM to 11.0 μM
choline; the method has been applied to simultaneous glucose and choline determinations in serum samples with good results.
This method gives a better performance than multivariate calibration based on Partial Least Squares Regression. The methodology
here shown could be also used for the simultaneous determination of other pairs of analytes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
A new strategy, epoxide-assisted precipitation route presented in this work, allows the shape control synthesis of Co3O4 nanoparticles. The shape of the nanoparticles is determined by the nature of the precursor cobalt salts (Co(NO3)2 · 6H2O, CoCl2 · 6H2O) used for the preparation of the particles. The different reaction dynamics of the two salts in ethanolic and aqueous solutions
with propylene oxide result in precursor particles with different structures, which lead to the formation of oxide nanoparticles
with different shapes during the heat treatment. Spherical particles of about 20 nm are obtained from the ethanolic solution
of Co(NO3)2 · 6H2O; cubic-shaped particles of about 30 nm can be prepared from the ethanolic solution of CoCl2 · 6H2O; whereas platelet-like particles of more than 100 nm are synthesized from the aqueous solution of the mixture of Co(NO3)2 · 6H2O and CoCl2 · 6H2O. 相似文献
Plasma membrane Ca2+-ATPases (PMCAs) are high affinity Ca2+ transporters actively involved in intracellular Ca2+ homeostasis. Considering the critical role of Ca2+ signalling in neuronal development and plasticity, we have analyzed PMCA-mediated Ca2+-ATPase activity and PMCA-isoform content in membranes from mouse cortex, hippocampus and cerebellum during postnatal development. 相似文献
Heparin detective : Silica nanoparticles functionalised with ion‐channel scaffolds were prepared and used for the chromofluorogenic sensing of heparin in aqueous environments (see figure). The surface of the nanoparticles was functionalised with polyamines (binding sites) and thiols. The reaction of a dye (squaraine) with the surface thiol groups was selectively inhibited by the coordination of heparin with the partly protonated polyamines.
A simple, reproducible, and efficient liquid chromatographic method was developed with UV detection. Water (0.05% TFA):acetonitrile
(0.05% TFA) was used as the mobile phase in a gradient system for the determination of procyanidin B2 (PB2) and epicatechin
(EC) in the bark of Guazuma ulmifolia Lam. The analysis was performed using a Phenomenex Gemini RP C18 column (5 μm) as stationary phase, at 30 °C, with a flow rate of 0.8 mL min−1, at a wavelength of 210 nm for detection and determination. The main validation parameters of the method were also determined.
Calibration curves were found to be linear, with ranges of 20.00–150.00 (PB2) and 10.00–110.00 μg mL−1 (EC). The correlation coefficients of linear regression analysis were between 0.9981 and 0.9988, and the detection limits
were between 2.89 and 2.54 μg mL−1. The contents of PB2 and EC were successfully determined, with satisfactory reproducibility and recovery. Recoveries of the
PB2 and EC were 103.00 and 104.01%, respectively. The method was successfully applied to the determination of procyanidins
in the bark of G. ulmifolia. 相似文献