含液晶成分的掺杂共聚物和胆甾醇基棕榈酸盐(或酯)掺合物(英文)

pacc:7855K Physicalblendscontainingmacromolecular compoundsandlowmolecularweightliquidcrys tals(LCs)haveimportantapplications.LCsare usedasreinforcementsforamorphouspolymersor indisplaydevices.TheadditionofLCstoamor phouspolymersdeterminesimprovementsin…     

Homogenization of integrals with pointwise gradient constraints via the periodic unfolding method

Abstract The pointwise gradient constrained homogenization process, for Neumann and Dirichlet type problems, is analyzed by means of the periodic unfolding method recently introduced in [21]. Classically, the proof of the homogenization formula in presence of pointwise gradient constraints relies on elaborated measure theoretic arguments. The one proposed here is elementary: it is based on weak convergence arguments in L^p spaces, coupled with suitable regularization techniques. Keywords: Homogenization, Gradient constrained problems, Periodic unfolding method Mathematics Subject Classification (2000): 49J45, 35B27, 74Q05     

Simultaneous Determination of Fenproporex, Diethylpropione and Methylphenidate in Oral Fluid by LC-MS/MS

A liquid chromatography–tandem mass spectrometry method has been developed and validated for confirmation and quantification of three amphetamine-type stimulants (ATS) in oral fluid (OF), namely fenproporex (FEN), diethylpropione (DIE) and methylphenidate (MPH), which are misused by some Brazilian drivers and have potentially dangerous consequences in road traffic. In this method, the OF was extracted by a simple and fast liquid–liquid extraction using acetonitrile. Calibration curves were linear throughout the concentration range from 2.5 to 90 ng mL^?1 in OF, using internal standard. The lower limit of quantification and the limit of detection were 2.5 and 0.5 ng mL^?1, respectively, for all ATS. Intra- and inter-assay precision and accuracy values were within regulatory limits. The analyte extraction presented poor recoveries, but was considered appropriated for analyses of ATS in OF due to the low limits of detection. Matrix effects and carry over were not detected. All analytes were stable during the whole analytical procedure. The present analytical method was considered simple and sensitive for simultaneous determination of FEN, DIE, and MPH in OF and suitable for clinical and forensic toxicology.     

A time dependent coupled system related to the tridimensional equations of a nematic liquid crystal

In this paper we prove some results about the existence, uniqueness and regularity of the solutions of a tridimensional variational approximated model for the Leslie's equations of an incompressible nematic liquid crystal (cf. [7]). This model was introduced in [1] where the bidimensional case is studied. Here we use the methods developed in [6], [4] and [8].     

The Surface Wettability and Adhesion of Poly(Ester Urethane)s and Poly(Ether Urethane)s

In this study the wetting characteristics of untreated and plasma-treated polyurethane thin films were investigated. The degree of wettability was investigated by measuring the contact angle formed between a liquid drop and the solid surface. The work of adhesion, interfacial free energy, spreading coefficient, and Girifalco–Good's interaction parameter changed significantly for plasma-treated polyurethane films. Both complete and partial wetting were analyzed from the spreading coefficient of liquid drops on the solid substrate.     

Infrared analysis of phase transitions in liquid crystal acrylate monomers bearing urethanic groups and cholesteryl as mesogen

An infrared analysis of phase transitions in three enantiotropic liquid crystalline acrylate monomers with different spacer lengths bearing urethane groups and cholesteryl as mesogen was carried out. Through heating and cooling, spectral modifications especially at the level of carbonyl, –NH– and urethane alkoxyl oxygen groups were found. These findings reveal the influence of hydrogen bonding on mesomorphic properties of the studied compounds mentioning that both liquid crystal transitions are evidenced by the spectral changes. For all the compounds studied, the values of the transition temperatures deduced from the spectral modifications are in good agreement with those obtained from DSC measurements.     

Thermally Stimulated Depolarization Currents and Optical Transmission Studies on UV Cured Polymer Dispersed Liquid Crystal Films

Polymer-dispersed-liquid-crystal films were obtained using the photopolymerization-induced-phase-separation method. The thermally stimulated depolarization current measurements indicate a space-charge-limited current. Conduction of electronic type was proven and the activation energy, specific to the conduction process, was calculated. Optical measurements have been performed simultaneously with the measurements of thermally stimulated currents and the nematic-isotropic phase transition was detected by the switch of the optical transmission. The change of the optical transmission versus applied a.c. voltage was the indication for the on-off switch behavior, useful in electro-optic applications.     

Coordination compounds of biological interest

The thermal properties of the Cr(III) complexes with the ligands glycine and glutamic acid were determined using TG, DTG and DTA techniques.The chromium(III)-glycine complex is more stable than the chromium(III)-glutamate complex. This behaviour is discussed in terms of different structures by IR and reflectance spectra as well as thermal data.