排序方式: 共有33条查询结果,搜索用时 15 毫秒
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Cathy McCullagh Jeanette M. C. Robertson Detlef W. Bahnemann Peter K. J. Robertson 《Research on Chemical Intermediates》2007,33(3-5):359-375
The use of semiconductor photocatalysis for treatment of water and air has been the topic of intense research activity over the past 20 years. This powerful process has also been extended to the disinfection of environments contaminated with pathogenic micro-organisms. This review summarizes recent developments concerned with the photocatalytic treatment of water contaminated with pathogenic micro-organisms presenting a potential hazard to animals and human beings. 相似文献
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Pan Z Hariharan M Arkin JD Jalilov AS McCullagh M Schatz GC Lewis FD 《Journal of the American Chemical Society》2011,133(51):20793-20798
Quantum yields for thymine photodimerization (Φ(TT)) have been determined for a series of short DNA single-strand and base-paired hairpin structures possessing a single thymine-thymine step with flanking purines. Values of Φ(TT) are strongly dependent upon the oxidation potential of the flanking purine, decreasing in the order: inosine > adenine > guanine > deazaguanine. The dependence of Φ(TT) on the ionization potential of the flanking purine is more pronounced when the purine of lower oxidation potential is located at the 5'- versus 3'-position in either a single strand or a hairpin. Molecular dynamics simulations for hairpin structures indicate that the TT step is π-stacked with both the 5' and 3' purine, but that there is little π-stacking with either purine in single-strand structures. The observation of moderately intense long-wavelength UV absorption features for hairpins having 5'-Z or G flanking purines suggests that excitation of ground state donor-acceptor complexes may account for more extensive quenching of dimerization by 5'- versus 3'-purines. The "purine effect" on Φ(TT) is attributed to a combination of ground state conformation, ground state electron donor-acceptor interactions, and excited state exciplex formation. 相似文献
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David Daniel Angela McCullagh James Moffat 《The Journal of the Operational Research Society》1984,35(3):225-233
Defence policy-making has to be set against an uncertain—indeed unpredictable—future. Given this uncertainty surrounding future conflict, air forces play an important part because of their inherent flexibility to undertake a variety of roles. This paper describes the assistance given to the Air Staff in deciding what mix of air-delivered weapons should be stockpiled to provide the RAF with this flexibility, subject to budgetary and other constraints. It is a simple application of linear programming with an unusual objective function. A number of alternative approaches are reviewed, and the rather pragmatic way in which various decisions regarding the conduct of the study were made is discussed. 相似文献
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Maanasa Raghavan James S. O. McCullagh Niels Lynnerup Robert E. M. Hedges 《Rapid communications in mass spectrometry : RCM》2010,24(5):541-548
We report a novel method for the chromatographic separation and measurement of stable carbon isotope ratios (δ13C) of individual amino acids in hair proteins and bone collagen using the LC‐IsoLink system, which interfaces liquid chromatography (LC) with isotope ratio mass spectrometry (IRMS). This paper provides baseline separation of 15 and 13 of the 18 amino acids in bone collagen and hair proteins, respectively. We also describe an approach to analysing small hair samples for compound‐specific analysis of segmental hair sections. The LC/IRMS method is applied in a historical context by the δ13C analysis of hair proteins and bone collagen recovered from six individuals from Uummannaq in Greenland. The analysis of hair and bone amino acids from the same individual, compared for the first time in this study, is of importance in palaeodietary reconstruction. If hair proteins can be used as a proxy for bone collagen at the amino acid level, this validates compound‐specific isotope studies using hair as a model for palaeodietary reconstruction. Our results suggest that a small offset observed in the bulk δ13C values of the hair and bone samples may be attributed to two factors: (i) amino acid compositional differences between hair and bone proteins, and (ii) differential turnover rates of the tissues and the amino acid pools contributing to their synthesis. This application proposes that hair may be a useful complementary or alternative source of compound‐specific paleodietary information. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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GD Fletcher 《Molecular physics》2013,111(23-24):2971-2976
A scalable multi-configuration self-consistent field (MCSCF) algorithm is described. The method for optimizing the orbital and configurational parameters is based upon the two-step Newton–Raphson approach with an augmented orbital Hessian matrix. A single copy of the two-electron integrals in the molecular orbital basis is distributed over the memory of all processors. Storage of the augmented Hessian is avoided by re-computing its elements as needed. A replicated data approach is used to parallelize the configuration interaction step. Scalability to 1024 processors is demonstrated. 相似文献
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McCullagh JS Juchelka D Hedges RE 《Rapid communications in mass spectrometry : RCM》2006,20(18):2761-2768
The scope of compound-specific stable isotope analysis has recently been increased with the development of the LC IsoLink which interfaces high-performance liquid chromatography (HPLC) and isotope ratio mass spectrometry (IRMS) to provide online LC/IRMS. This enables isotopic measurement of non-volatile compounds previously not amenable to compound-specific analysis or requiring substantial modification for gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS), which results in reduced precision. Amino acids are an example of such compounds.We present a new chromatographic method for the HPLC separation of underivatized amino acids using an acidic, aqueous mobile phase in conjunction with a mixed-mode stationary phase that can be interfaced with the LC IsoLink for compound-specific delta13C analysis. The method utilizes a reversed-phase Primesep-A column with embedded, ionizable, functional groups providing the capability for ion-exchange and hydrophobic interactions. Baseline separation of 15 amino acids and their carbon isotope values are reported with an average standard deviation of 0.18 per thousand (n = 6). In addition delta13C values of 18 amino acids are determined from modern protein and archaeological bone collagen hydrolysates, demonstrating the potential of this method for compound-specific applications in a number of fields including metabolic, ecological and palaeodietary studies. 相似文献
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Priscila M. Lalli Yuri E. Corilo Maíra Fasciotti Maria Francesca Riccio Gilberto Fernandes de Sá Romeu J. Daroda Gustavo H. M. F. Souza Michael McCullagh Michael D. Bartberger Marcos N. Eberlin Iain Campuzano 《Journal of mass spectrometry : JMS》2013,48(9):i-i
We have studied the behavior of isomers and analogues by traveling wave ion mobility mass spectrometry (TWIM‐MS) using drift‐gases with varying masses and polarizabilities. Despite the reduced length of the cell (18 cm), a pair of constitutional isomers, N‐butylaniline and para‐butylaniline, with theoretical collision cross‐section values in helium (ΩHe) differing by as little as 1.2 Å2 (1.5%) but possessing contrasting charge distribution, showed baseline peak‐to‐peak resolution (Rp‐p) for their protonated molecules, using carbon dioxide (CO2), nitrous oxide (N2O) and ethene (C2H4) as the TWIM drift‐gas. Near baseline Rp‐p was also obtained in CO2 for a group of protonated haloanilines (para‐chloroaniline, para‐bromoaniline and para‐iodoaniline) which display contrasting masses and theoretical ΩHe, which differ by as much as 15.7 Å2 (19.5%) but similar charge distributions. The deprotonated isomeric pair of trans‐oleic acid and cis‐oleic acid possessing nearly identical theoretical ΩHe and ΩN2 as well as similar charge distributions, remained unresolved. Interestingly, an inversion of drift‐times were observed for the 1,3‐dialkylimidazolium ions when comparing He, N2 and N2O. Using density functional theory as a means of examining the ions electronic structure, and He and N2‐based trajectory method algorithm, we discuss the effect of the long‐range charge induced dipole attractive and short‐range Van der Waals forces involved in the TWIM separation in drift‐gases of differing polarizabilities. We therefore propose that examining the electronic structure of the ions under investigation may potentially indicate whether the use of more polarizable drift‐gases could improve separation and the overall success of TWIM‐MS analysis. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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