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101.
102.
Rajinder Singh Friederike Teichert Albrecht Seidel Jonathan Roach Rebecca Cordell Mai‐Kim Cheng Heinrich Frank William P. Steward Margaret M. Manson Peter B. Farmer 《Rapid communications in mass spectrometry : RCM》2010,24(16):2329-2340
Human exposure to polycyclic aromatic hydrocarbons (PAHs) from sources such as industrial or urban air pollution, tobacco smoke and cooked food is not confined to a single compound, but instead to mixtures of different PAHs. The interaction of different PAHs may lead to additive, synergistic or antagonistic effects in terms of DNA adduct formation and carcinogenic activity resulting from changes in metabolic activation to reactive intermediates and DNA repair. The development of a targeted DNA adductomic approach using liquid chromatography/tandem mass spectrometry (LC/MS/MS) incorporating software‐based peak picking and integration for the assessment of exposure to mixtures of PAHs is described. For method development PAH‐modified DNA samples were obtained by reaction of the anti‐dihydrodiol epoxide metabolites of benzo[a]pyrene, benzo[b]fluoranthene, dibenzo[a,l]pyrene (DB[a,l]P) and dibenz[a,h]anthracene with calf thymus DNA in vitro and enzymatically hydrolysed to 2′‐deoxynucleosides. Positive LC/electrospray ionisation (ESI)‐MS/MS collision‐induced dissociation product ion spectra data showed that the majority of adducts displayed a common fragmentation for the neutral loss of 116 u (2′‐deoxyribose) resulting in a major product ion derived from the adducted base. The exception was the DB[a,l]P dihydrodiol epoxide adduct of 2′‐deoxyadenosine which resulted in major product ions derived from the PAH moiety being detected. Specific detection of mixtures of PAH‐adducted 2′‐deoxynucleosides was achieved using online column‐switching LC/MS/MS in conjunction with selected reaction monitoring (SRM) of the [M+H]+ to [M+H–116]+ transition plus product ions derived from the PAH moiety for improved sensitivity of detection and a comparison was made to detection by constant neutral loss scanning. In conclusion, different PAH DNA adducts were detected by employing SRM [M+H–116]+ transitions or constant neutral loss scanning. However, for improved sensitivity of detection optimised SRM transitions relating to the PAH moiety product ions are required for certain PAH DNA adducts for the development of targeted DNA adductomic methods. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
103.
Highcock EG Barnes M Schekochihin AA Parra FI Roach CM Cowley SC 《Physical review letters》2010,105(21):215003
The effect of flow shear on turbulent transport in tokamaks is studied numerically in the experimentally relevant limit of zero magnetic shear. It is found that the plasma is linearly stable for all nonzero flow shear values, but that subcritical turbulence can be sustained nonlinearly at a wide range of temperature gradients. Flow shear increases the nonlinear temperature gradient threshold for turbulence but also increases the sensitivity of the heat flux to changes in the temperature gradient, except over a small range near the threshold where the sensitivity is decreased. A bifurcation in the equilibrium gradients is found: for a given input of heat, it is possible, by varying the applied torque, to trigger a transition to significantly higher temperature and flow gradients. 相似文献
104.
Saralees Nadarajah 《数学物理学报(B辑英文版)》2010,30(1):330-340
Two posterior distributions for the mean of the Laplace distribution are obtained by deriving the distributions of the product XY and the ratio X/Y when X and Y are Student's t and Laplace random variables distributed independently of each other. Tabulations of the associated percentage points are given along with computer programs for generating them. 相似文献
105.
A parallel study of mechanical alloying and solidification was carried out on FCC high-entropy alloys (HEAs) CoCrCuNi, CoCrCuFeNi and CoCrCuMnNi to investigate the effects of each processing methods on the resulting microstructure, crystal structure and microhardness. Elemental powders were mechanically alloyed followed by spark plasma sintering (SPS) at 800°C and 900°C to achieve densified discs, while arc melting was carried out from bulk pieces of the elemental metals followed by furnace annealing at 800°C and 900°C for 5?h. Both processing routes resulted in a primary FCC phase with secondary Cu-rich FCC segregation as interdendrites for the solidified alloys and particle boundaries for the SPS alloys, with the exception of a small amount of σ phase present in the SPS processed alloys. The solidification of the CoCrCuNi, CoCrCuFeNi and CoCrCuMnNi HEAs resulted in typical dendritic microstructure, followed by the precipitation of a small Cr-rich phase in the CoCrCuMnNi alloy after annealing. The grain size of the mechanically alloyed powder was approximately 20?nm from the Scherrers equation and the SPS processed HEAs consisted of a Cu-rich phase in the particle boundaries, forming cobblestone-like microstructure. The microhardness was examined in the as-cast, annealed and SPS states. It was found that the SPS processed samples had an increased microhardness by a factor of 2.5. 相似文献
106.
Newling B Poirier CC Zhi Y Rioux JA Coristine AJ Roach D Balcom BJ 《Physical review letters》2004,93(15):154503
We introduce a noninvasive, quantitative magnetic resonance imaging (MRI) wind-tunnel measurement in flowing gas (>10 m s(-1)) at high Reynolds numbers (Re>10(5)). The method pertains to liquids and gases, is inherently three dimensional, and extends the range of Re to which MRI is applicable by orders of magnitude. There is potential for clear time savings over traditional pointwise techniques. The mean velocity and turbulent diffusivity of gas flowing past a bluff obstruction and a wing section at realistic stall speeds were measured. The MRI data are compared with computational fluid dynamics. 相似文献
107.
M. -G. Porquet Ts. Venkova R. Lucas A. Astier A. Bauchet I. Deloncle A. Prévost F. Azaiez G. Barreau A. Bogachev N. Buforn A. Buta D. Curien T. P. Doan L. Donadille O. Dorvaux G. Duchêne J. Durell Th. Ethvignot B. P. J. Gall D. Grimwood M. Houry F. Khalfallah W. Korten S. Lalkovski Y. Le Coz M. Meyer A. Minkova I. Piqueras N. Redon A. Roach M. Rousseau N. Schulz A. G. Smith O. Stézowski Ch. Theisen B. J. Varley 《The European Physical Journal A - Hadrons and Nuclei》2005,24(1):39-49
The 121,123,125,127Sb nuclei have been produced as fission fragments in three reactions induced by heavy ions: 12C + 238U at 90 MeV bombarding energy, 18O + 208Pb at 85 MeV, and 31P + 176Yb at 152 MeV. Their level schemes have been built from gamma rays detected using the EUROBALL III and IV arrays. High-spin states of 123,125,127Sb nuclei have been identified for the first time. Moreover isomeric states lying around 2.3 MeV have been established in 123,125,127Sb from the delayed coincidences between the fission fragment detector SAPhIR and the gamma array. All the observed states can be described by coupling a d5/2 or g7/2 proton to an excited Sn core involving either vibrational states or broken neutron pairs. 相似文献
108.
We have grown single crystals of the psuedo-one-dimensional compound Sr3CuIrO6, a K4CdCl6-derived monoclinic structure with Cu-Ir chains along the [101] direction. We present the ac and dc magnetization behavior
of the single crystals in comparison with that of the polycrystalline form reported earlier. There is a distinct evidence
for at least two magnetic transitions, at 5 K (T
1) and 19 K (T
2), with different relative magnitudes in the single and polycrystals. The low temperature magnetic relaxation behavior of
both the forms is found to be widely different, exhibiting unexpected time dependence. 相似文献
109.
G. Geymonat M. Lobo-Hidalgo E. Sanchez-Palencia G. F. Roach 《Mathematical Methods in the Applied Sciences》1982,4(1):291-306
We consider two vibration problems containing a small parameter → 0: a) Vibration of an elastic, slightly compressible body, and b) acoustic vibration of a slightly viscous compressible barotropic fluid in a vessel. The asymptotics of eigenvalues for problem a) is studied by using a uniformly convergent expansion of the stiff type. After a re-scaling of the spectral parameter, the problem b) reduces to an analogous problem, and we prove that, as ε → 0, infinitely many eigenvalues converge to 0 (which is an eigenvalue of infinite multiplicity of the corresponding inviscid acoustic problem). 相似文献
110.