It is demonstrated that irradiation of the anticancer drug flutamide (FM) in the presence of unilamellar phospholipid bilayer vesicles, chosen as a model for cell membranes, leads to an efficient photobinding process. This pathway is triggered by an unexpected hydrogen‐abstraction reaction of the excited drug by the lipid chain and provides additional evidence that the overall photochemical scenario observed in the vesicles is unusually triggered by conformational change of the drug's molecular structure upon incarceration in the ‘close‐packed' bilayer. The present investigation, beyond contributing to the general picture concerning fundamental aspects of the light‐induced processes in self‐organized assemblies, may also provide important insights for a more satisfactory understanding of the recently reported adverse photoallergic and phototoxic phenomena displayed by this anticancer drug. 相似文献
This work presents a new method to calculate the Lyapunov spectrum of dynamical systems based on the time evolution of initially
small disturbed copies (“clones”) of the motion equations. In this approach, it is not necessary to construct the tangent
space associated with the time evolution of linearized versions of motion equations, being the Lyapunov exponents directly
estimated in terms of the rate of convergence or divergence of these disturbed clones with respect to the fiducial trajectory,
there being periodic correction via the Gram–Schmidt Reorthonormalization procedure. The proposed method offers the possibility
of partial estimation of the Lyapunov spectrum and can also be applied to nonsmooth dynamics, since the linearization procedure
is no longer required. The idea is tested for representative continuous- and discrete-time dynamical systems and validated
by means of comparison with the classical method to perform this calculation. To illustrate its applicability in the nonsmooth
context, the largest Lyapunov exponent of the FitzHugh–Nagumo neuronal model under discontinuous periodic excitation is calculated
taking the amplitude of stimulation as control parameter. This analysis reveals some complex behaviours for this simple neuronal
model, which motivates relevant discussions about the possible role of chaos in the cognitive process. 相似文献
We demonstrate broadband second harmonic generation of low-energy pulses produced by injecting two single-frequency lasers into a highly nonlinear fiber. Full nonlinear conversion of the corresponding spectra, consisting of broadband (∼200 nm) optical frequency combs at ∼1580 nm, were obtained by using conventional birefringence phase-matching in two BIBO crystals (2-mm and 100-μm long) with a normal incidence configuration. The crystals were not tilted and the pulses were not compressed. This broadband conversion results from the large phase-matching bandwidth of the nonlinear BIBO crystals at ∼1550 nm, but also seems to be a consequence of a fundamental comb with small spectral phase variation. 相似文献
Ethylene (E) and norbornene (N) were copolymerized in the presence of PhSiH3 as chain‐transfer agent with [Ti(η5:η1‐C5Me4SiMe2NBut)(η1‐Me)2] precatalyst combined with [Ph3C][B(C6F5)4]. The silane was introduced at chain‐ends of E‐co‐N copolymers with concomitant reinitiation of the growing polymer chain. The concentrations of the silane and polymer molecular weight are inversely correlated. The characteristic signals of SiH2Ph chain‐ends were observed by 1H NMR. The Si heteroatom is predominantly adjacent to ethylene units in E‐co‐N copolymers with high N content.
Russian Physics Journal - The study of quantum states near the dissociation threshold is necessary both to understand the formation of molecules and to explore accurately chemical reactions.... 相似文献
Quantum Radiophysics Division. Translated from preprint No. 23, 1991 of the Lebedev Physics Institute, Russian Academy of Sciences, Moscow, Russia. 相似文献
The performance of tunable all-optical wavelength converters based on four-wave mixing in optical fibers is experimentally tested in a field-trial network. Two converters were built with two different fibers. The first one was made with a small variation in the zero-dispersion wavelength (ZDW) dispersion shifted fiber and the second one with a highly nonlinear fiber that presents great ZDW variations. In order to compare the tuning ranges obtained in both cases we present an experimental spectral analysis. Numerical simulations that consider the influence of both the dispersion slope and the long-scale ZDW variations of the fiber complement the experiments. The tuning bandwidth was larger in the highly nonlinear fiber case. For a set of different optical signal-to-noise ratios, the measurements of the Q-factor of the signal and those of the converted wave are our main results. These results show that the penalty imposed by the converters is different for each converted wavelength. The maximum penalty obtained for the Q-factor was ∼6 dB, but it was ?3 dB for most cases. In all experiments we used a technique based on a dynamic polarization controller in order to avoid power fluctuations in the converted wave caused by polarization induced variations in the signal. 相似文献
Layer‐by‐layer (LBL) films consisting of layers of the azo dye Sunset Yellow alternated with chitosan display spontaneous birefringence, which is attributed to the film anisotropy imparted by the LBL method. This is unusual for azobenzene‐containing materials as they normally form films with randomly oriented molecules, presenting birefringence only due to photoinduced isomerization cycles. Spontaneous birefringence does not appear in cast films, but occurs for LBL films obtained under various experimental conditions.
Chemical structures of (a) Sunset Yellow and (b) chitosan. 相似文献