Effect of ultraviolet radiation on polyethylene naphthalate films irradiated with high-energy heavy ions

The effect of UV radiation in the spectral range of 280–400 nm on polyethylene naphthalate (PEN) films has been studied. Changes in the optical absorption spectra of PEN after exposure to accelerated ions and UV radiation have been revealed. Changes in the surface properties have been explored, and the depth of the degraded polymer layer after long-term UV irradiation in air has been measured. Depending on the treatment time, the depth has made 0.1–0.9 μm. The photoablation rate and the quantum yield of monomer unit removal due to UV irradiation of the PEN films have been estimated at ~0.7 × 10^?4 molecule/photon. The possibility of the formation of asymmetric pores in PEN films using controlled photooxidative degradation has been shown.     

Investigations into the response of an optical gas sensor based on polymeric LB films

The response of an NO₂ sensing system based on LB films of a polysiloxane with azobenzene chromophoric side-chains has been investigated. Changes in absorbance on exposure to 100 ppm NO₂ have been recorded using UV-visible absorption spectroscopy from which changes in extinction coefficient (Δ k ≈ 0.033 at 500 nm) have been determined. Shallow angle X-ray reflectivity (SAXR) studies indicate a change in layer thickness from 2.10nm in air to 2.31 nm in 10000 ppm NO₂ together with loss of Bragg detail. Changes in real refractive index (Δn ≈ 0.107 over most of the visible region) for films in air and 100 ppm NO₂ have been deduced from reflectance spectra.     

Bulk condensation in a dusty vapor–gas flow with regard to dust particle size distribution

Bulk condensation in a dusty vapor–gas flow has been numerically simulated taking into account dust particle size distribution. Two types of distribution (monodisperse and lognormal) have been used. Changes in the bulk condensation process that are relevant to the dustiness of the flow have been revealed by comparing the results obtained for dust-free and dusty flows at the monodisperse dust distribution. Variations in the relative contributions of the homogeneous and heterogeneous mechanisms with variations in the flow dustiness have been considered. The effect of the root-mean-square deviation in the dust particle sizes on the bulk condensation in the dusty flow has been illustrated by comparing the data obtained for the monodisperse and lognormal distributions.     

The stability of the certified reference ores MP-1 KC-1 and SU-1 towards air oxidation

The stability of three certified reference sulphide ores, MP-1, KC-1 and SU-1, towards air oxidation has been measured at 50 degrees and 40, 62 and 82% relative humidity, and at 62% relative humidity and 34 degrees and 67 degrees . Both the relative humidity and temperature affect the rate of oxidation but their relative importance depends on the mineralogical composition of the ore. Changes in the water-extractable metals and elemental sulphur content on oxidation have been determined. It is concluded that these ores may be stored safely in sealed bottles under normal laboratory conditions.     

The effects of physical aging in polycarbonate

The effects of physical aging below the glass transition temperature on selected properties of polycarbonate have been studied. Changes in tensile yield strength, post yield stress drop, and fracture toughness as a result of annealing at 120°C for 240 h have been measured and are related to changes in free volume as measured by positron annihilation lifetime spectroscopy. The free volume concentration remains constant during the aging heat treatment at 120°C but decreases after cooling due to aging. The relationship between free volume changes and physical property changes is discussed in terms of molecular conformations and fracture mode. The effect of aging on fracture morphology is presented to aid interpretations of fracture mode.     

Alteration of contact properties and chemical structure of polyethersulfone film surface by direct-current discharge treatment

Changes in the contact properties of the surface of polyethersulfone films modified at the cathode and the anode by dc discharge with varying the treatment time and discharge current have been studied. It has been shown that the treatment imparts hydrophilicity to the films, which persists for a long time. The chemical composition and structure of the surface of the modified films has been examined using X-ray photoelectron spectroscopy.     

Modification of tetrafluoroethylene-perfluoropropylvinyl ether copolymer films in direct-current discharge

Changes induced in the surface properties of films of a tetrafluoroethylene copolymer with perfluoropropylvinyl ether by direct-current discharge have been investigated, depending on the discharge parameters. It has been shown that the treatment of the films at the anode is more effective than at the cathode. A change in the contact properties of the modified films during their storage in air under ambient conditions and upon heating to 150°C has been examined. The chemical composition of the surface of the films after modification, storage, and heating has been studied by X-ray photoelectron spectroscopy and Fouriertransform IR spectroscopy. It has been found that dc discharge treatment significantly improves the adhesion properties of the films and barely affects their light transmission.     

Characterisation of the Kratos Axis Ultra with spherical mirror analyser for XPS imaging

The imaging performance of an XPS instrument employing a spherical mirror electron energy analyser has been characterised by measuring the peak position, full width at half maximum (FWHM), and lineshape, at every pixel in the image, for different modes of operation. Changes in these parameters have been identified and recommendations made for quantification of, and chemical state determination from, spectrum image data sets. Copyright © 2006 John Wiley & Sons, Ltd.     

Infrared and Raman spectra of alkali halide/NO−3 systems

Detalled Raman spectra of the NO^?₃ ion substitutionally isolated in Rbl, Kl and KCl have been investigated at various temperatures between 77 and 300 K. These spectra, together with their corresponding infrared spectra, have been used to study the effective symmetry of these systems. Changes in the infrared and Raman activities of some of the modes of the NO^?₃ ions have been observed as the samples were cooled. Two different symmetries, one at room and the other at low temperature, have been identified as D₃ and C_3v respectively.     

Microwave Discharge in Liquid Hydrocarbons: Study of a Liquid Hydrocarbon after Exciting the Discharge

Changes in liquid hydrocarbons (hexane, cyclohexane, n-heptane, isooctane, decane, pentadecane, cetane, petroleum solvent, benzene, toluene, and o-xylene) have been studied after exciting a microwave discharge in their bulk. The experiments have been carried out at atmospheric pressure. For the analysis, GC/MS, IR spectroscopy, and dynamic light scattering methods have been used. It has been shown that new compounds and nanoparticles are formed in the hydrocarbons.     

Design of pi-conjugated organic materials for one-dimensional energy transport in nanochannels

Various end-substituted distyrylbenzenes have been synthesized to serve as guest molecules in inclusion compounds to promote efficient energy transport along one-dimensional channels. Their optical and photophysical properties have been characterized at both experimental and theoretical levels. All molecules display a large transition dipole moment between the ground state and lowest excited state and hence a short radiative lifetime (on the order of 1-2 ns). They also exhibit a large spectral overlap between the emission and absorption spectra, which enables efficient energy transport between molecules arranged in a head-to-tail configuration in nanochannels. Hopping rates on the order of 10(12) s(-1) are calculated at a full quantum-chemical level; this is much larger than the radiative lifetimes and opens the way for energy migration over large distances. Changes in the nature of the terminal substituents are found to modulate the optical properties weakly but to impact significantly the energy transfer rates.     

Calix-arene silver nanoparticles interactions with surfactants are charge, size and critical micellar concentration dependent

The interactions of silver nanoparticles capped by various calix[n]arenes bearing sulphonate groups at the para and/or phenolic faces with cationic, neutral and anionic surfactants have been studied. Changes in the plasmonic absorption show that only the calix[4]arene derivatives sulphonated at the para-position interact and then only with cationic surfactants. The interactions follow the CMC values of the surfactants either as simple molecules or mixed micelles.     

Novel monoligated imine–Pd–NHC complexes: extremely active pre-catalysts for Suzuki–Miyaura coupling of aryl chlorides

Novel monoligated imine–Pd–NHC pre-catalysts with extremely high activity for the coupling of aryl chlorides and aryl boronic acids have been well explored. Three diffident catalysts could be obtained through one reaction. Changes in imine ligands would lead to remarkable variation on catalytic activity. Under mild reaction conditions, high reaction yields were achieved. A wide range of biphenyls could be efficiently obtained at ultra low catalyst loadings of 0.005 mol %.     

Effect of ageing of sisal fibres on properties of sisal - Polypropylene composites

A composite laminate based on natural sisal fibre and polypropylene was prepared by compression moulding. The mechanical properties of the composite were assessed under tensile, flexural and impact loading. Changes in the stress-strain characteristics, yield stress, tensile strength, and tensile (Young's) modulus, due to ageing have been analysed. Important findings with the fresh and aged fibres and their behaviour in composites have been reported and analysed.     

Effect of sonication on the particle size of montmorillonite clays

This paper reports on the effect of sonication on SAz-1 and SWy-1 montmorillonite suspensions. Changes in the size of the particles of these materials and modifications of their properties have been investigated. The variation of the particle size has been analyzed by DLS (dynamic light scattering). In all cases the clay particles show a bimodal distribution. Sonication resulted in a decrease of the larger modal diameter, as well as a reduction of its volume percentage. Simultaneously, the proportion of the smallest particles increases. After 60 min of sonication, SAz-1 presented a very broad particle size distribution with a modal diameter of 283 nm. On the other hand, the SWy-1 sonicated for 60 min presents a bimodal distribution of particles at 140 and 454 nm. Changes in the properties of the clay suspensions due to sonication were evaluated spectroscopically from dye-clay interactions, using Methylene Blue. The acidic sites present in the interlamellar region, which are responsible for dye protonation, disappeared after sonication of the clay. The changes in the size of the scattering particles and the lack of acidic sites after sonication suggest that sonication induces delamination of the clay particles.     

Epoxy oligomer and cyclen polymerization on the air-water interface. Receptor properties of a monolayer

Two-dimensional functional polymer systems have been obtained for the first time based on an epoxy oligomer and 1,4,7,10-tetraazacyclododecane (cyclen). The effect of UV radiation on the efficiency of polymerization in the system has been studied. The morphology of polymer materials formed on the liquid surface as a result of thermo- and UV-induced polymerization has been studied. It has been shown that a polymer Langmuir monolayer based on an epoxy oligomer-cyclen mixture can be used as a sensor for copper ions, and the conditions for the system regeneration have been determined. Changes in the pH of the subphase have been established as causing structural rearrangements in the polymer monolayer, which lead to changes in the optical properties of the latter.     

Isotopologous Organotellurium Probes Reveal Dynamic Hypoxia In Vivo with Cellular Resolution

Changes in the oxygenation state of microenvironments within solid tumors are associated with the development of aggressive cancer phenotypes. Factors that influence cellular hypoxia have been characterized; however, methods for measuring the dynamics of oxygenation at a cellular level in vivo have been elusive. We report a series of tellurium‐containing isotopologous probes for cellular hypoxia compatible with mass cytometry (MC)—technology that allows for highly parametric interrogation of single cells based on atomic mass spectrometry. Sequential labeling with the isotopologous probes (SLIP) in pancreatic tumor xenograft models revealed changes in cellular oxygenation over time which correlated with the distance from vasculature, the proliferation of cell populations, and proximity to necrosis. SLIP allows for capture of spatial and temporal dynamics in vivo using enzyme activated probes.     

Relationships between temperature,magnetic moment,and continuous symmetry measures in spin crossover complexes

A study of the changes in the symmetry of the metal coordination sphere that accompany spin crossover transitions has been carried out. Changes in symmetry have been calibrated by using the continuous symmetry measures approach. Different behaviors have been found for several families of complexes, depending on the nature of their ligands. The most remarkable changes take place for trischelate complexes, for which octahedricity, trigonal prismacity, chirality, bite angle, bond distance, tempeature, pressure, magnetic moment, and density are correlated.     

Investigations on the texture and structure of crystalline and liquid-crystalline phases of a side group polyacrylate with a biphenyl mesogenic moiety

Polyacrylates and polymethacrylates with mesogenic side groups have been synthesized for a structural investigation by observations of textures and by X-ray diagrams of smectic and crystalline phases. With the preparation of well developed textures, characteristic features of the various phases were recognized and related to different structures. Changes of textures within one phase and at the phase transition were studied. Various crystalline modifications, dependent on sample treatment and transformations, were identified by different textures. X-ray diffraction experiments on analogously treated samples confirmed and completed the results of the optical investigations. The results for one polymeric compound are represented and discussed in detail.     

Proton Transfer Influence on Geometry and Electron Density in Benzoic Acid–Pyridine Complexes

The influence of the proton transfer on the geometry of donor and acceptor molecule in benzoic acid–pyridine complexes is investigated by theoretical calculations at the B3LYP/6‐311++G** level of theory. Systematic shifts of the H‐atom in the H‐bond are reflected in the geometry of the COOH group and the lengths of aromatic ring bond lengths of the proton acceptor. Changes in electron densities have been studied by atoms in molecules analysis. A systematic natural bond orbital analysis has been performed to study the proton transfer mechanism. Two donor orbitals are engaged in the proton transfer process which is accompanied by a change in orbital delocalization of H‐atom that can switch between two donor orbitals so the path of proton transfer in intermolecular H‐bond is not determined by the orbital shape. Theoretical results have been confirmed by experimental results published previously.