Search results for "ddc:5"

Second-harmonic generation in Langmuir–Blodgett monolayers of stilbazium salt and phenylhydrazone dyes

1988

The second-order nonlinear optical susceptibilities χ(2) of several phenylhydrazone and stilbazium salt dyes in Langmuir–Blodgett monolayers have been determined from second-harmonic-generation measurements. Three of the substances demonstrated χ(2) values greater than 10−6 electrostatic units, although two of the three did not absorb light significantly at the second-harmonic wavelength.

Amphiphilic dyes for nonlinear optics: Dependence of second harmonic generation on functional group substitution

2008

Characterization of thin superconducting YBaCuO-films by Raman-spectroscopy

1988

We have investigated thin sputtered films of the high Tc material YBa2Cu3O7 by means of Raman spectroscopy at different stages of the preparation process. We find that the films are amorphous after sputtering. The Raman spectra indicate that random polycrystalline layers, as well as crystalline layers with preferred orientation, are obtained by an additional thermal treatment.

Small-pore driven high capacitance in a hierarchical carbon via carbonization of Ni-MOF-74 at low temperatures

2016

A hierarchical porous carbon prepared via direct carbonization of Ni-MOF-74 loaded with furfuryl alcohol at 450 °C displays high specific capacitance in comparison with other MOF-derived carbons as a result of the formation of micropores smaller than 1 nm.

Depletion induced isotropic-isotropic phase separation in suspensions of rod-like colloids

2007

When non-adsorbing polymers are added to an isotropic suspension of rod-like colloids, the colloids effectively attract each other via depletion forces. We performed Monte Carlo simulations to study the phase diagram of such rod-polymer mixture. The colloidal rods were modeled as hard spherocylinders; the polymers were described as spheres of the same diameter as the rods. The polymers may overlap with no energy cost, while the overlap of polymers and rods is forbidden. Large amounts of depletant cause phase separation of the mixture. We estimated the phase boundaries of isotropic-isotropic coexistence both in the bulk and in confinement. To determine the phase boundaries we applied the gra…

Effect of mixing and spatial dimension on the glass transition

2009

We study the influence of composition changes on the glass transition of binary hard disc and hard sphere mixtures in the framework of mode coupling theory. We derive a general expression for the slope of a glass transition line. Applied to the binary mixture in the low concentration limits, this new method allows a fast prediction of some properties of the glass transition lines. The glass transition diagram we find for binary hard discs strongly resembles the random close packing diagram. Compared to 3D from previous studies, the extension of the glass regime due to mixing is much more pronounced in 2D where plasticization only sets in at larger size disparities. For small size disparitie…

Structure and dynamics in amorphous tellurium and Te-n clusters: A density functional study

2012

Density functional/molecular dynamics simulations have been performed on amorphous tellurium (a melt-quenched sample of 343 atoms at 300 K) and on Te clusters with up to 16 atoms. The former extend our calculations on liquid Te at 560, 625, 722, and 970 K [Phys. Rev. B 81, 094202 (2010)]. We discuss trends in structures (including those of other group-16 elements), electronic densities of states, and vibration frequencies. Chain structures are common in S and Se, but the chains in amorphous Te are short, and branching sites with threefold-coordinated atoms are common. The energy difference between two- and threefold local coordination depends sensitively on the exchange-correlation function…

The spectrum of weakly coupled map lattices

1998

We consider weakly coupled analytic expanding circle maps on the lattice Zd (for d 2 l), with small coupling strength c and coupling between two sites decaying exponentially with the distance. We study the spectrum of the associated (Perron-Frobenius) transfer operators. We give a FrCchet space on which the operator associated to the full system has a simple eigenvalue at 1 (corresponding to the SRB measure p* previously obtained by Bricmont-Kupiainen (BKl)) and the rest of the spectrum, except maybe for continuous spectrum, is inside a disc of radius smaller than one. For d = 1 we also construct Banach spaces of densities with respect to pr on which perturbation theory, applied to the diff…

Birth of the Biscane

2017

This paper describes the unprecedented storm Stephanie, which exhibited tropical characteristics over the Bay of Biscay on 15 September 2016. Remote sensing observations reveal a cloud-free area surrounded by a circular precipitation pattern and an axisymmetric wind field, while buoy observations show an abrupt drop in wind speed during the passage of the storm centre. Model analysis further corroborates an ongoing tropical transition from a frontal cold-core to a symmetric warm-core system. By analogy with ‘Medicanes’ (Mediterranean hurricanes), we name this storm a ‘Biscane’ (Biscay hurricane). Weather systems of this kind may become more frequent in a warmer climate.

Specific release of membrane-bound annexin II and cortical cytoskeletal elements by sequestration of membrane cholesterol

1997

Annexin II is an abundant protein which is present in the cytosol and on the cytoplasmic face of plasma membrane and early endosomes. It is generally believed that this association occurs via Ca(2+)-dependent binding to lipids, a mechanism typical for the annexin protein family. Although previous studies have shown that annexin II is involved in early endosome dynamics and organization, the precise biological role of the protein is unknown. In this study, we found that approximately 50% of the total cellular annexin was associated with membranes in a Ca(2+)-independent manner. This binding was extremely tight, since it resisted high salt and, to some extent, high pH treatments. We found, h…