Anelli, P, Asakawa, M, Ashton, PR, Bissell, RA, Clavier, G, Górski, R, Kaifer, AE, Langford, SJ, Mattersteig, G, Menzer, S, Philp, D, Slawin, AMZ, Spencer, N, Stoddart, JF, Tolley, MS & Williams, DJ 1997, 'Toward Controllable Molecular Shuttles', Chemistry – A European Journal, vol. 3, no. 7, pp. 1113-1135.
View/Download from: Publisher's site
View description>>
AbstractA number of nanometer‐scale molecular assemblies, based on rotaxane‐type structures, have been synthesized by means of a template‐directed strategy from simple building blocks that, on account of the molecular recognition arising from the noncovalent interactions between them, are able to self‐assemble into potential molecular abacuses. In all the cases investigated, the π‐electron‐deficient tetracationic cyclophane cyclobis(paraquat‐p‐phenylene) is constrained mechanically around a dumbbell‐shaped component consisting of a linear polyether chain intercepted by at least two, if not three, π‐electron‐rich units and terminated at each end by blocking groups or stoppers. The development of an approach toward constructing these molecular abacuses, in which the tetracationic cyclophane is able to shuttle back and forth with respect to the dumbbell‐shaped component, begins with the self‐assembly of a [2]rotaxane consisting of two hydroquinone rings symmetrically positioned within a polyether chain terminated by triisopropylsilyl ether blocking groups. In this first so‐called molecular shuttle, the tetracationic cyclophane oscillates in a degenerate fashion between the two π‐electron‐rich hydroquinone rings. Replacement of one of the hydroquinone rings—or the insertion of another π‐electron‐rich ring system between the two hydroquinine rings—introduces the possibility of translational isomerism, a phenomenon that arises because of the different relative positions and populations of the tetracationic cyclophane with respect to the π‐donor sites on the dumbbell‐shaped component. In two subsequent [2]rotaxanes, one of the hydroquinone rings in the dumbbell‐shaped component is replaced, first by a p‐xylyl and then by an indole unit. Finally, a tetrathiafulvalene (TTF) unit is positioned between two hydroquinone rings in the dumbbell‐shaped component. Spectroscopic and el...
Cook, AS, Williams, DBG, White, AJP, Williams, DJ, Lange, SJ, Barrett, AGM & Hoffman, BM 1997, 'Enantiomerically Pure “Winged” Spirane Porphyrazinoctaols', Angewandte Chemie International Edition in English, vol. 36, no. 7, pp. 760-761.
View/Download from: Publisher's site
Cortie, MB & Jackson, EMLEM 1997, 'Simulation of the precipitation of sigma phase in duplex stainless steels', METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, vol. 28, no. 12, pp. 2477-2484.
View/Download from: Publisher's site
View description>>
The precipitation of sigma phase within the ferrite component of a duplex stainless steel has been simulated using a two-dimensional computer model which takes into account the partitioning of alloy elements between ferrite and austenite. The model is ba
Craig, DC, Ghiggino, KP, Jolliffe, KA, Langford, SJ & Paddon-Row, MN 1997, 'Synthesis, Structure, and Photophysical Studies of a Pair of Novel Rigid Bichromophoric Systems Bearing a Methyl Viologen Acceptor Unit', The Journal of Organic Chemistry, vol. 62, no. 8, pp. 2381-2386.
View/Download from: Publisher's site
Credi, A, Balzani, V, Langford, SJ & Stoddart, JF 1997, 'Logic Operations at the Molecular Level. An XOR Gate Based on a Molecular Machine', Journal of the American Chemical Society, vol. 119, no. 11, pp. 2679-2681.
View/Download from: Publisher's site
Dean, RT, Fu, SL, Stocker, R & Davies, MJ 1997, 'Biochemistry and pathology of radical-mediated protein oxidation', BIOCHEMICAL JOURNAL, vol. 324, no. 1, pp. 1-18.
Fu, SL & Dean, RT 1997, 'Structural characterization of the products of hydroxyl-radical damage to leucine and their detection on proteins', BIOCHEMICAL JOURNAL, vol. 324, no. 1, pp. 41-48.
Fu, SL, Davies, MJ & Dean, RT 1997, 'Protein-bound hydroxylated amino acid levels are elevated in human atherosclerotic plaque', ATHEROSCLEROSIS, vol. 134, no. 1-2, pp. 221-221.
View/Download from: Publisher's site
View description>>
It is well established that macromolecule oxidation, especially lipoprotein oxidation is a key and early event responsible for the loading of lipid into atherosclerotic foam cells and possibly many other features of atherogenesis. There have been many studies concerning protein oxidation and its contribution to the pathology. This study examined oxidized amino acid residues which may result from hydroxyl radical damage [Fu et al. 1995a. Free Rad Biol Med 19, 281-292; 1995b. Biochem. J. 311, 821-827; 1997. Biochem. J. in press] on intimal proteins isolated from normal human ateries and human atherosclerotic plaques. Normal iliac arteries (n = 6) were obtained from liver transplant donors and human plaques (n = 9) from patients undergoing carotid endarterectomy. Proteins were obtained from the intima samples after homogenization and delipidation and subquently subjected to acid-catalysed hydrolysis. Protein hydrolysates were analysed by several HPLC methods for the presence of oxidation products (characteristic of hydroxyl radical attack) of tyrosine (DOPA, dityrosine), phenylalnine (o- and m-tyrosine), valine (?-hydroxyvaline), and leucine (?-hydoxyleucine). Results are expressed as mmol oxidized amino acid/mol parent amino acid and are summarized in the table below. It shows that all of the oxidized amino acids measured are elevated in the plaque samples compared to those in the normal controls, suggesting that hydroxyl radicals may be an important factor for atherogenesis
Goldys, EM, Zuo, HY, Phillips, MR, Contessa, CM, Vaughan, MR & Tansley, TL 1997, 'Type I and type II alignment of the light hole band in In0.15Ga0.85As/GaAs and in In0.15Ga0.85As/Al0.15Ga0.85As strained quantum wells', JOURNAL OF ELECTRONIC MATERIALS, vol. 26, no. 8, pp. 922-927.
View/Download from: Publisher's site
View description>>
We present results of photoluminescence and cathodoluminescence measurements of strained undoped In0.15Ga0.85AsXGaAs and In0.15Ga0.85As/Al0.15Ga0.85As quantum well structures, designed to throw light on the current controversy over light-hole band alignment at low In content. We compare these data with theoretical calculations of the confined state energies within the eight band effective mass approximation. Our analysis shows that for In0.15Ga0 85As/GaAs, the observed two transitions are consistent with either type I or type II alignment of the light hole band for band offset ratios within the accepted range. In the case of In0.15Ga0 85As/Al0.15Ga0 85As, however, our results clearly indicate type II alignment for the light hole band. We derive the band offset ratio Q, defined here as Q = ΔEc/ΔEg where ΔEc is the conduction band offset and ΔEg is the bandgap difference between the quantum well and the barrier in the presence of strain, for the In0.15Ga0.85As/Al0.15Ga0.85As system to be Q = 0.83 and discuss it in the context of the common anion rule.
Kalceff, MAS, Phillips, MR, Moon, AR & Smallwood, A 1997, 'Cathodoluminescence microanalysis of natural hydrated amorphous SiO2; Opal', PHYSICS AND CHEMISTRY OF MINERALS, vol. 24, no. 2, pp. 131-138.
View/Download from: Publisher's site
View description>>
Natural amorphous hydrated silicon dioxide (opal) has been investigated for the first time using Cathodoluminescence microanalysis in a Scanning Electron Microscope. Defect centers have been identified and imaged with high sensitivity and high spatial re
McDonagh, AM, Humphrey, MG & Hockless, DCR 1997, 'Selective preparation of cis-or trans-dichlorobis{(R,R)-1,2-phenylenebis(methylphenylphosphine-P)}osmium(II) from dimethylsulfoxide complex precursors', Tetrahedron: Asymmetry, vol. 8, no. 21, pp. 3579-3583.
View/Download from: Publisher's site
View description>>
NA
Phillips, MR, Moon, AR, Stevens Kalceff, MA & Remond, G 1997, 'Design, Construction and Applications of a Low Temperature (5 K) Combined Scanning Cathodoluminescence and WDS X-ray Spectroscopy and Imaging System', Microscopy and Microanalysis, vol. 3, no. S2, pp. 1069-1070.
View/Download from: Publisher's site
View description>>
Recently there has been a renaissance in scanning cathodoluminescence (CL) microscopy and microanalysis primarily brought about by the analytical demands of the semiconductor industry in addition to significant advances in photonics technology (high efficiency PMTs, CCDs and CL collectors). The strength of the CL analysis technique lies in its ability to provide high spatial (lateral and depth) resolution concentration and distribution information about: (i) the chemical state (identity, oxidation state and co-ordination) of trace level impurities and (ii) point / extended structural defects (vacancies and dislocations) in both semiconductors and insulators.For many materials, interpretation of CL spectra and images measured at low temperature (5 K) is quite straightforward. However CL generation via recombination of electron / hole pairs is a competitive process. Consequently in some specimens the measured CL intensity is not directly proportional to the concentration of the particular luminescent center but relates to the concentration of other radiative or non-radiative centers. In these cases it is difficult to decide whether contrast in the CL image is due to variation in the concentration of the radiative center or the competitive center.
Stevens Kalceff, MA, Phillips, MR & Moon, AR 1997, 'Cathodoluminescence Investigation of Electron Irradiation Damage in Insulators.', Microscopy and Microanalysis, vol. 3, no. S2, pp. 749-750.
View/Download from: Publisher's site
View description>>
Cathodoluminescence (CL) is the luminescent emission from a material which has been irradiated with electrons. Cathodoluminescence microanalysis (spectroscopy and microscopy) in an electron microscope complements the average defect structure information available from complementary techniques (e.g. Photoluminescence, Electron Spin Resonance spectroscopy). CL microanalysis enables both pre-existing and irradiation induced local variations in the bulk and surface defect structure to be characterized with high spatial (lateral and depth) resolution and sensitivity. This is possible as electron beam parameters such as the beam energy, may be varied to finely control the penetration depth of the incident electrons and hence the local volume of specimen probed.Irradiation with charged and neutral energetic radiation produces defects in radiation sensitive materials. The energetic electron beam in an electron microscope may also induce defects in the specimen. Cazaux has characterized the electric field produced by electron irradiation of a insulator with a conductive surface coating
Stevens Kalceff, MA, Phillips, MR & Moon, AR 1997, 'Cathodoluminescence Microcharacterization of the Irradiation Sensitive Defect Structure of Amorphous Silicon Dioxide', Microscopy and Microanalysis, vol. 3, no. S2, pp. 751-752.
View/Download from: Publisher's site
View description>>
Cathodoluminescence (CL) Microscopy (imaging) and Spectroscopy in a Scanning Electron Microscope enables high spatial resolution, high sensitivity detection of defect centers in materials. Cathodoluminescence microanalysis has been used to investigate the irradiation sensitive defect structure of Types I, II, III and IV amorphous silicon dioxide SiO2 (quartz and silica glasses). The CL experiments were performed in a JEOL JSM 35C SEM equipped with Oxford Instruments liquid N and liquid He cryogenic stages, and an Oxford Instruments MonoCL cathodoluminescence imaging and spectral analysis system. The observed CL emissions, were excited with a stationary electron beam at normal incidence and corrected for total instrument response. The corrected CL spectra were fitted with a multiparameter Gaussian function using a non linear least squares curve fitting algorithm and were identified with particular defect structures. The CL emission from high quality pure amorphous silica and quartz glasses is dominated by intrinsic processes (associated with the host lattice). See Table 1.
