Domain wall motion in ferromagnets modelled by a quintic complex Ginzburg-Landau equation

A quintic complex Ginzburg-Landau equation is derived from a Landau-Lifshitz-Gilbert equation and is used to describe the magnetization dynamics in a one-dimensional uni-axial ferromagnet. Trough the use of suitable approximations, we derive the magnetic solitary wave excitations solutions which have pulse-like shapes. Subsequent numerical simulations reveal domain wall propagation.     

In vitro Release Study of Tretinoin from Tretinoin/Cyclodextrin Derivative Complexes

The effects of hj3m1100h24864m3/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin, hydroxypropyl hj3m1100h24864m3/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin and dimethyl hj3m1100h24864m3/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-cyclodextrin complexes on the in vitro release of tretinoin gels were investigated. The experiments were carried out in a Franz cell using a silicone membrane as a barrier for the diffusion of the vehicle. Two types of vehicle were compared: a hydroalcoholic gel in which both tretinoin and the inclusion complexes are soluble, and an aqueous gel in which only the complexes are soluble but tretinoin is dispersed. As expected, the release rate of free tretinoin in the hydroalcoholic gel is much faster than in the aqueous gel. However, with the aqueous gel, the cyclodextrin complexation enhances the diffusion rate of the active drug through the membrane, especially with the hydroxypropyl cyclodextrin inclusion compound. The release of tretinoin is related not only to the stability constant of the inclusion, but also to the binding properties of the inclusion compounds to the vehicle.     

Analysis of the π-electronic structure of infinitely large networks

Summary Applying the Coulson and Longuet-Higgins integral method to polycyclic aromatics, the analytical solutions of bond orders, hj67p/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-electronic energy and benzene character for the infinitely large cyclic polyacene and polyphenanthrene with various modes of bond alternation are obtained in the HMO scheme. Most of the results are explicitly and newly expressed in terms of three kinds of the elliptic integrals. Judging from the magnitudes of bond orders and benzene character the most probable modes of the bond alternation for these two networks are discussed with their Kekulé structures. It was shown that if bond alternation is properly taken into consideration, HMO calculation can fairly well reproduce the results obtained by more sophisticated methods.     

Supramolecular Chemistry of Cyclodextrin-Peptide Hybrids: Azobenzene-Tagged Peptides

AC17, which is composed of 17 amino acids and has an azobenzene moiety but has no cyclodextrin (CD) unit in the side chain, exhibits 54% helix content. However, AChj07636x0073n18v/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">17, which has both trans-azobenzene and hj07636x0073n18v/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-CD, shows 82% helix content. This result suggests that the helix structure is stabilized by host (CD)-guest (azobenzene) bridge in the side chain of the peptide. The helix content changed by trans-cis photoisomerization as shown by 64% helix content for AChj07636x0073n18v/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">17 in its cis form. This result suggests that cis-azobenzene unit is excluded from the hj07636x0073n18v/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-CD cavity, thus resulting in the smaller helix content. The helix contents for AChj07636x0073n18v/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">17, which has both azobenzene and hj07636x0073n18v/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD, are 94% in the cis form and 87% in the trans form, suggesting that the cis form is included in the hj07636x0073n18v/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-CD cavity. Azobenzene-tagged CD-peptide hybrids with histidine unit were also prepared and photoregulation of catalytic activity in ester hydrolysis was examined.     

Finite sampling interval effects in Kramers-Moyal analysis

Large sampling intervals can affect reconstruction of Kramers-Moyal coefficients from data. A new method, which is direct, non-stochastic and exact up to numerical accuracy, is developed to estimate these finite time effects. The method is applied numerically to biologically inspired examples. Exact finite time effects are also described analytically for two special cases. The approach developed will permit better evaluation of Langevin or Fokker-Planck based models from data with large sampling intervals. It can also be used to predict the sampling intervals for which finite time effects become significant.     

Blends of normal high density and ultra-high molecular weight polyethylene, γ irradiated at a low dose

The kinetics of a nonisothermal crystallization and melting ofhj57w2l045634302/xxlarge947.gif" alt="gamma" align="MIDDLE" BORDER="0"> irradiated with dose of 6 Mrad blends of an ultra-high molecular-weight polyethylene (UHMWPE) and a high-density polyethylene with normal molecular weight (NMWPE) is investigated by means of DSC. The blends have been prepared at temperature below the flow temperature of UHMWPE: The enthalpies of melting of the polyethylenes increase, while those of their blends decrease after irradiation. The enthalpies of crystallization of the pure polyethylenes are higher, while those of their blends almost do not change or are a bit higher after irradiation. The rates of a nonisothermal crystallization and melting of the polyethylenes increase, while those of the polyethylenes in the blends decrease after irradiation. Thermomechanical measurements under constant load in wide-temperature interval of irradiated polyethylenes and their blends have been made. A high-elastic plateau in viscous-liquid state is established on the thermomechanical curves of UHMWPE, and the blends with high content of UHMWPE. On the basis of results obtained assumptions have been made about the processes taking place in the blends under the action of irradiation, as well as about the character of the mutual influence between the components in the process of irradiation.     

Interpolation of Intersections Generated by a Linear Functional

Let (X ₀, X ₁) be a Banach couple such that X ₀ ∩ X ₁ is dense in X ₀ and X ₁. By (X ₀, X ₁)_θ,q , 0 < θ < 1, 1 ⩽ q < ∞, we denote the spaces of the real interpolation method. Let ψ be a nonzero linear functional defined on some linear space M ⊂ X ₀ + X ₁ and such that ψ ∈ (X ₀ ∩ X ₁)*, and let N = Ker ψ. We examine conditions under which the natural formula

A Note on Ultrametric Matrices

It is proved in this paper that special generalized ultrametric and special hj3/MediaObjects/s10587-004-6441-5_Ieq1.gif" alt=" align="middle" border="0"> matrices are, in a sense, extremal matrices in the boundary of the set of generalized ultrametric and hj3/MediaObjects/s10587-004-6441-5_Ieq2.gif" alt=" align="middle" border="0">matrices, respectively. Moreover, we present a new class of inverse M-matrices which generalizes the class of hj3/MediaObjects/s10587-004-6441-5_Ieq3.gif" alt=" align="middle" border="0">matrices.     

Gamma-ray induced color centers in Yb:YAG crystals grown by Czochralski method

20 at.% Yb:YAG single crystals have been grown by the CZ method and gamma-ray irradiation induced color centers and valence change of Fe³⁺ and Y b³⁺ ions in Yb:YAG have been studied. One significant 255 nm absorption band was observed in as-grown crystals and was attributed to Fe³⁺ ions. Two additional absorption (AA) bands located at 255 nm and 345 nm, respectively, were produced after gamma irradiation. The changes in the AA spectra after gamma irradiation and air annealing are mainly related to the charge exchange of the Fe³⁺, Fe²⁺, oxygen vacancies and F-type color centers. Analysis shows that the broad AA band is associated with Fe²⁺ ions and F-type color centers. The transition Y b³⁺→Y b²⁺ takes place as an effect of recharging of one of the Y b³⁺ ions from a pair in the process of gamma irradiation.     

Coupled oscillator models with no scale separation

We consider a class of spatially discrete wave equations that describe the motion of a system of linearly coupled oscillators perturbed by a nonlinear potential. We show that the dynamical behavior of this system cannot be understood by considering the slowest modes only: there is an “inverse cascade” in which the effects of changes in small scales are felt by the largest scales and the mean-field closure does not work. Despite this, a one and a half degree of freedom model is derived that includes the influence of the small-scale dynamics and predicts global conformational changes accurately. Thus, we provide a reduced model for a system in which there is no separation of scales. We analyze a specific coupled-oscillator system that models global conformation change in biomolecules, introduced in [I. Mezi?, On the dynamics of molecular conformation, Proc. Natl. Acad. Sci. 103 (20) (2006) 7542-7547]. In this model, the conformational states are stable to random perturbations, yet global conformation change can be quickly and robustly induced by the action of a targeted control. We study the efficiency of small-scale perturbations on conformational change and show that “zipper” traveling wave perturbations provide an efficient means for inducing such change. A visualization method for the transport barriers in the reduced model yields insight into the mechanism by which the conformation change occurs.