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41.
42.
J. N. Spencer Eric S. Holmboe Daniel W. Firth Mindy R. Kirshenbaum 《Journal of solution chemistry》1981,10(10):745-756
Enthalpies of solution have been used to calculate transfer enthalpies for phenol, pyridine, and DMSO between the solvent cyclohexane and the solvents CCl4, benzene, and CHCl3. By use of model compounds, enthalpies due to interactions with phenol, pyridine, and DMSO have been determined. These enthalpies are used to calculate the effect of solvation relative to cyclohexane on hydrogen bonded complexes in CCl4 and benzene solvents. Correlations with enthalpies due to interactions and frequency shifts for the hydroxyl stretch in these solvents have also been made. 相似文献
43.
44.
Alastair J. S. McIntosh Stephen J. Barrington Hilary Bird Daniel Hurst Phillippa Spencer Suzanne H. Pelfrey Matthew J. Baker 《Analytical and bioanalytical chemistry》2012,404(8):2307-2315
The ability to distinguish bacteria from mixed samples is of great interest, especially in the medical and defence arenas. This paper reports a step towards the aim of differentiating pathogenic endospores in situ, to aid any required response for hazard management using infrared spectroscopy combined with multivariate analysis. We describe a proof-of-principle study aimed at discriminating biological warfare simulants from common environmental bacteria. We also report an evaluation of multiple pre-processing techniques and subsequent differences in cross-validation of two pattern recognition models (Support Vector Machines and Principal Component–Linear Discriminant Analysis) for a six-class classification (bacterial classification). These classifications were possible with an average sensitivity of 88.0 and 86.9?%, and an average specificity of 97.6 and 97.5?% for the SVM and the PC-LDA models, respectively. Most spectroscopic models are built upon spectra from bacteria that have been specifically prepared for analysis by a particular method; this paper will comment upon the differences in the bacterial spectrum that occur between specific preparations when the bacteria have spent 30?days in the simulated weather conditions of a hot dry climate. Figure
3D-PC-LDA score plot (left), for the six class bacterial identification, with the loading plot (right) for each of the three discriminant functions used 相似文献
45.
The effect of adsorbed S at different coverages on the adhesion of Fe(110) surfaces in match and mismatch is examined using density functional theory (DFT). S is adsorbed in atop, bridge, and 4-fold hollow sites on one side of the interface in c(2 x 2) and p(1 x 1) arrangements, corresponding to coverages of 1/2 and 1 monolayer, respectively. The calculated adhesion energy values at different interfacial separations are fitted to the universal binding energy relation, and the effect of the S coverages on the adhesive strength is analyzed. The effect of relaxation of the interfaces at equilibrium is also investigated, and the resulting interfacial structures and related magnetic and charge density properties are compared. 相似文献
46.
Terry Spencer 《Accreditation and quality assurance》2005,10(6):308-314
This presentation deals with issues of comparability and traceability in food analysis in Australia from several perspectives. This includes the current national (Australian) and increasingly international (Codex) performance-based approach to food analysis. The Australian food regulatory process will be described, particularly those aspects that impact on the analysis of food in a regulatory sense. This section will also describe two areas where specific methods have been mandated in legislation and discuss two case studies where the analytical method has impacted on the elaboration of standards. Other areas to be covered include regulation/requirements relating to supply/availability of reference materials, the use of proficiency testing as a means of ensuring comparability, and, finally, some thoughts on what role BIPM/CCQM may play in the analysis of food.Electronic Supplementary Material Supplementary material is available for this article at
相似文献
Terry SpencerEmail: Phone: +612-6213-6102Fax: +612-6213-6815 |
47.
The spectroscopic, electronic, and DNA-binding characteristics of two novel ruthenium complexes based on the dialkynyl ligands 2,3-bis(phenylethynyl)-1,4,8,9-tetraaza-triphenylene (bptt, 1) and 2,3-bis(4-tert-butyl-phenylethynyl)-1,4,8,9-tetraaza-triphenylene (tbptt, 2) have been investigated. Electronic structure calculations of bptt reveal that the frontier molecular orbitals are localized on the pyrazine-dialkynyl portion of the free ligand, a property that is reflected in a red shift of the lowest energy electronic transition (1: λ(max) = 393 nm) upon substitution at the terminal phenyl groups (2: λ(max) = 398 nm). Upon coordination to ruthenium, the low-energy ligand-centered transitions of 1 and 2 are retained, and metal-to-ligand charge transfer transitions (MLCT) centered at λ(max) = 450 nm are observed for [Ru(phen)(2)bptt](2+)(3) and [Ru(phen)(2)tbptt](2+)(4). The photophysical characteristics of 3 and 4 in ethanol closely parallel those observed for [Ru(bpy)(3)](2+) and [Ru(phen)(3)](2+), indicating that the MLCT excited state is primarily localized within the [Ru(phen)(3)](2+) manifold of 3 and 4, and is only sparingly affected by the extended conjugation of the bptt framework. In an aqueous environment, 3 and 4 possess notably small luminescence quantum yields (3: ?(H(2)O) = 0.005, 4: ?(H(2)O) = 0.011) and biexponential decay kinetics (3: τ(1) = 40 ns, τ(2) = 230 ns; 4: τ(1) ~ 26 ns, τ(2) = 150 ns). Addition of CT-DNA to an aqueous solution of 3 causes a significant increase in the luminescence quantum yield (?(DNA) = 0.045), while the quantum yield of 4 is relatively unaffected (?(DNA) = 0.013). The differential behavior demonstrates that tert-butyl substitution on the terminal phenyl groups inhibits the ability of 4 to intercalate with DNA. Such changes in intrinsic luminescence demonstrate that 3 binds to DNA via intercalation (K(b) = 3.3 × 10(4) M(-1)). The origin of this light switch behavior involves two competing (3)MLCT states similar to that of the extensively studied light switch molecule [Ru(phen)(2)dppz](2+). The solvent- and temperature-dependence of the luminescence of 3 reveal that the extended ligand aromaticity lowers the energy of the (3)ππ* excited state into competition with the emitting (3)MLCT state. Interconversion between these two states plays a significant role in the observed photophysics and is responsible for the dual emission in aqueous environments. 相似文献
48.
Andrew J. Thompson Dr. Jerome Dabin Javier Iglesias‐Fernández Dr. Albert Ardèvol Dr. Zoran Dinev Assoc. Prof. Spencer J. Williams Dr. Omprakash Bande Dr. Aloysius Siriwardena Carl Moreland Dr. Ting‐Chou Hu David K. Smith Prof. Harry J. Gilbert Prof. Carme Rovira Prof. Gideon J. Davies 《Angewandte Chemie (International ed. in English)》2012,51(44):11171-11171
49.
Naloxone 3-methyl ether was selectively oxidized by treatment with cerium ammonium nitrate in aqueous acetonitrile at ambient temperature to provide the 10-(S)-hydroxy adduct. The stereochemistry of the oxidation product was proven by single crystal X-ray structure determination. The Dess-Martin periodinane further oxidized the 10-hydroxy to the 10-keto analog. Deprotection formed 10-ketonaloxone as an analytical reference standard. 相似文献
50.
Prof. Dr. Mateo Alajarin Dr. Raul‐Angel Orenes Prof. Dr. Judith A. K. Howard Dr. Elinor C. Spencer Prof. Dr. Jonathan W. Steed Dr. Aurelia Pastor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(8):2389-2397
Tris(2‐ and 3‐ureidobenzyl)amines with Cs symmetry self‐assemble in solution forming mixtures of regioisomeric capsular aggregates, one of which is chiral and the other centrosymmetric. Under certain conditions, a predominance of the centrosymmetric regioisomer is found before equilibrium, that is, a mixture close to the statistical ratio of the two species is reached. In the solid state, there is a preference for the centrosymmetric capsules. Molecular models of both regioisomeric aggregates have been built and analyzed for comparison. Guests inside capsules formed by self‐assembly of desymmetrized tris(3‐ureidobenzyl)amines feel different magnetic environments, depending on whether they are inside a chiral or an achiral regioisomeric container. Of special significance are the experiments with a more flexible triurea endowed with an ureidopropylic arm, which self‐assembles with the same efficiency as the more rigid tris(ureidobenzyl)amines. 相似文献