Search results for "force"

1987

The dielectric relaxation properties of a combined main-chain/side-chain liquid-crystalline polymer were investigated. It was found that the rotation of the side chain about the main chain (δ-process) is not as strongly restricted as in side-chain liquid-crystalline polymers. This is attributed to the facts that the side chain is attached to the flexible spacer within the chain backbone and that the concentration of the side chains is comparatively small. Two low-temperature relaxation processes were observed to occur in the glassy smectic and the crystalline state. They are attributed to intramolecular motions with in the mesogenic groups.

Dynamic Anomalies and their Relation to the Glass Transition: A Neutron Scattering Study of the Glass Forming Van der Waals Liquid Ortho-terphenyl

1991

Neutron scattering experiments on the molecular glass former ortho-terphenyl reveal a dynamic anomaly at a temperature Tc ≈ 290 K well above the calorimetric glass temperature Tg = 243 K. Close above Tc the density autocorrelation function ΦQ(t) shows a two step decay over 4–5 decades in time. The slower component obeys the time-temperature superposition principle. Its line shape can be well parametrized by a Kohlrausch law and is strongly temperature dependent as its relaxation time scales with the shear viscosity. Thus this component is identified with the structural relaxation (α-process). The faster component (β-process) is much less temperature dependent. Its line shape factorizes in a…

Nanoparticles at fluid interfaces.

2017

Nanoparticles at fluid interfaces are becoming a central topic in colloid science studies. Unlike in the case of colloids in suspensions, the description of the forces determining the physical behavior of colloids at interfaces still represents an outstanding problem in the modern theory of colloidal interactions. These forces regulate the formation of complex two-dimensional structures, which can be exploited in a number of applications of technological interest; optical devices, catalysis, molecular electronics or emulsions stabilization. From a fundamental viewpoint and typical for colloidal systems, nanoparticles and microparticles at interfaces are ideal experimental and theoretical mo…

Time resolved CARS measurements of I2 in solid Kr

2006

Dephasing is a central concept in condensed phase spectroscopy. It determines how long a system will maintain its coherence. The dephasing time of a system is determined by dynamic intermolecular interactions, and therefore measurements of dephasing time can provide information on interactions and couplings between a molecule and its environment. This chapter illustrates the application of the femtosecond coherent anti-Stokes Raman scattering (CARS) method to investigate the vibrational dephasing of I 2 in solid krypton. Dephasing of vibrational states between v = 2 and v = 16 is studied in the temperature range T = 2.6–32 K. The low vibrational states show dephasing times on the order of a…

Towards the origin of the shear force in near-field microscopy

2001

The shear force from a gold or a graphite sample acting on an approaching near-field optical probe is studied in detail. The adiabatic and dissipative contributions to the force are clearly distinguished by monitoring the amplitude as well as the phase of the tip vibration when the tip approaches the surfaces. We also take into account that not only the damping and the resonance frequency but also the mass of the system changes when the tip approaches the surface. The relative strength of the contributions to the force varies differently but characteristically with the distance of the two samples, starting at a much larger distance in the case of graphite. The adiabatic contribution is lar…

Charging process in electron conducting polymers: dimerization model

2001

Abstract Theory of the charging and discharging process in electron-conducting polymer films at an electrode surface has been presented. It is based on the concept of two coexisting subsystems at the polymer matrix, ‘usual’ sites P which can exchange with the electrode by the electronic charge in a quasi-reversible manner, and sites D where intermolecular bonds between neighboring polymer molecules can be formed. The charging and discharging of the latter subsystem may be realized along different reaction pathways, e.g. via the bond formation after the generation of two cation radicals within such site D in the course of the anodic scan while the bond dissociation may take place via a parti…

Optical properties of biocompatible polyaniline nano-composites

2006

Abstract Polyaniline (PANI) is an electro-active polymer of great interest thanks to its outstanding physical and chemical properties which make it suitable for various applications in optics, bioelectronics, biosensors, diagnostics and therapeutic devices. Unfortunately, PANI is infusible and insoluble in most common solvents and, thus, very difficult to process. In the attempt of improving processability, yet preserving its interesting properties, PANI has been synthesized in the form of particles and dispersed into a hydrogel matrix. The synthesis of PANI–hydrogel composites proceeds via γ-irradiation of PANI dispersions as obtained by ‘in situ’ polymerization of aniline in the presence …

La libre circulación de resoluciones judiciales en la UE en el caso de la sustracción internacional de menores

2020

El presente artículo aborda la regulación actual y futura del sector del reconocimiento y ejecución de resoluciones extranjeras en materia de sustracción internacional de menores en el ámbito de la Unión Europea. Materia específica que motivó la previsión de un régimen de eficacia extraterritorial de resoluciones judiciales distinguido – y privilegiado – al del régimen genérico de las resoluciones en materia de responsabilidad parental. Recientemente, el instrumento aplicable en la materia, el Reglamento 2201/2003 (Reglamento Bruselas II bis) ha sufrido un importante proceso de reforma que ha culminado con la aprobación de un nuevo Reglamento, el Reglamento 2019/1111. En este trabajo aborda…

Mediation and Private International Law: Improving Free Circulation of Mediation Agreements Across the EU

2016

This paper, commissioned by the European Parliament’s Policy Department for Citizens’ Rights and Constitutional Affairs upon request by the JURI Committee, examines the issues arising in the context of cross-border mediation. Cross-border litigation has increased steadily in recent years in Europe as a consequence of the consolidation of the European unification process. The enactment of Directive 2008/52/EC has certainly led to the presence of mediation legislation in the EU Member States. But many important differences can still be ascertained in relation to the legal framework developed, which affect key aspects of mediation. For mediation to obtain full endorsement by citizens in the fu…

Melamine induced conformational change of ethyl resorcinarene in solid state

2000

When ethyl resorcinarene (1) and melamine (2) are co-crystallised, all intramolecular hydrogen bonds keeping the resorcinarene in crown conformation are broken causing an unexpected conformational change to boat, and a highly ordered hydrogen bonded network is formed.