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81.
82.
Focazio MJ Kolpin DW Barnes KK Furlong ET Meyer MT Zaugg SD Barber LB Thurman ME 《The Science of the total environment》2008,402(2-3):201-216
83.
Treated wastewater effluent is a potential environmental point source for antidepressant pharmaceuticals. A quantitative method was developed for the determination of trace levels of antidepressants in environmental aquatic matrixes using solid-phase extraction coupled with liquid chromatography-electrospray ionization tandem mass spectrometry. Recoveries of parent antidepressants from matrix spiking experiments for the individual antidepressants ranged from 72 to 118% at low concentrations (0.5 ng/L) and 70 to 118% at high concentrations (100 ng/L) for the solid-phase extraction method. Method detection limits for the individual antidepressant compounds ranged from 0.19 to 0.45 ng/L. The method was applied to wastewater effluent and samples collected from a wastewater-dominated stream. Venlafaxine was the predominant antidepressant observed in wastewater and river water samples. Individual antidepressant concentrations found in the wastewater effluent ranged from 3 (duloxetine) to 2190 ng/L (venlafaxine), whereas individual concentrations in the waste-dominated stream ranged from 0.72 (norfluoxetine) to 1310 ng/L (venlafaxine). 相似文献
84.
The friction coefficient is measured for systems consisting of a thin potassium chloride film deposited onto a variety of
clean, flat metal substrates, namely Pb, Sn, Au, Ag, Cu, Pd, Fe, Ta, and two types of steel, which are rubbed by a tungsten
carbide pin in an ultrahigh vacuum. The friction coefficients are plotted versus 1/H
S, the inverse of the substrate hardness, where two regimes are found. In the first regime, where deformation at the asperity
tips is suggested to be plastic, the observed variation in friction coefficient with substrate hardness is rationalized by
assuming that the shear strength S for sliding on a KCl film varies with contact pressure P as S = S
0 + aP, yielding values for a of 0.14 ± 0.02 and S
0 of ~60–70 MPa. In the second regime, it is proposed that the softer, film-covered Pb and Sn substrates are closer to being
in conformal contact with the rough tribopin. These values of S
0 and a, along with the measured surface asperity height distribution of the tribopin and the value of the friction coefficient for
a KCl monolayer on the metal, are used to rationalize the observed increase in friction coefficient with increasing film thickness. 相似文献
85.
86.
Sugar fatty acid ester surfactants: Biodegradation pathways 总被引:2,自引:0,他引:2
Irene J. A. Baker R. Ian Willing D. Neil Furlong Franz Grieser Calum J. Drummond 《Journal of surfactants and detergents》2000,3(1):13-27
In previous work, we found that the presence of a sulfonyl or alkyl group adjacent to the ester bond of sugar ester surfactants
is associated with a dramatic reduction in the rate of biodegradation relative to that of unsubstituted esters. In this study,
we investigated the pathways followed during the biodegradation of sucrose laurate, sucrose α-sulfonyl laurate, and sucrose
α-ethyl laurate to determine the reasons for their different biodegradation rates. Through the use of high-performance liquid
chromatography and proton nuclear magnetic resonance spectroscopy, the nature of the intermediates formed during the biodegradation
of these three key sugar esters was determined. It was found that sucrose laurate biodegradation occurs via initial ester hydrolysis. In contrast, sucrose α-sulfonyl laurate degrades by initial alkyl chain oxidation. This indicates
that the ester hydrolysis pathway is blocked by the sulfonyl group adjacent to the ester bond so that biodegradation is forced
to proceed via the slower alkyl chain oxidation pathway. Sucrose α-ethyl laurate was degraded at least in part by alkyl chain oxidation,
indicating that ester hydrolysis was also inhibited by the presence of an ethyl group. It is therefore concluded that previously
observed relationships between structure and biodegradability arise because of the influence that different structural elements
have on the pathways followed during biodegradation. 相似文献
87.
Boscoboinik J. Anibal Calaza Florencia C. Furlong Octavio J. Collins Sebastián E. 《Topics in Catalysis》2019,62(12-16):805-807
Topics in Catalysis - 相似文献
88.
The temperature dependence of the Tomlinson/Prandtl model for nanoscale sliding friction is analyzed by considering the properties of the initial and final states between which the tip can move, as well as the energy barrier between them, for various sliding regimes defined by the value of the corrugation factor γ. When γ < 1, the friction force tends to zero, defining a so-called superlubricious regime. The most commonly observed behavior is found for γ > 4.603, where the friction force increases monotonically with increasing sliding velocity up to a critical value equal to the value of F * (lateral force at T = 0) and monotonically decreases with temperature from F * at T = 0. However, completely different behavior is found when 1 < γ < 4.603. The temperature dependence of the lateral force in this regime is investigated using Monte Carlo simulations. The friction force still tends to F * as T approaches 0 K, but in contrast to the behavior found when γ > 4.603, the friction force increases with increasing temperature from F * , reaches a maximum value, and then decreases monotonically as the temperature rises further. Such behavior has been observed in atomic force microscopy friction measurements. 相似文献
89.
It has been suggested from molecular dynamics simulations that low-coordination-number sites are produced at a sliding metal–metal interface, but, because of their instability, they may rapidly relax to increase their coordination number. The possible presence of such low-coordination sites on the surface is tested by exploiting the observation that the desorption temperatures of 1-alkenes on copper increase with both the number of carbons atoms in the 1-alkenes and the surface roughness. Thus, 1-alkenes desorb from a Cu(111) single crystal, with relatively few low-coordination sites, at temperatures between 60 and 100 K lower than from a polycrystalline copper foil. The decrease in friction after impinging a flux of various 1-alkenes on a copper foil, while rubbing in an ultrahigh vacuum tribometer, correlates very well with the corresponding 1-alkene coverages on a copper foil, estimated using the desorption kinetics. This suggests either that rubbing does not result in the formation of lower-coordination sites or that they relax sufficiently rapidly that they do not influence the surface chemistry of 1-alkenes. Surface analyses indicate that shear at the interface causes carbon to diffuse into the subsurface region to form a tribofilm. 相似文献
90.
RA Furlong DR Goudie NP Carter JE Lyall NA Affara MA Ferguson-Smith 《Canadian Metallurgical Quarterly》1993,52(6):1191-1199
Meiotic recombination in flow-sorted single sperm was used to analyze four highly polymorphic microsatellite markers on the long arm of chromosome 9. The microsatellites comprised three tightly linked markers: 9CMP1 (D9S109), 9CMP2 (D9S127), and D9S53, which map to 9q31, and a reference marker, ASS, which is located in 9q34.1. Haplotypes of single sperm were assessed by using PCR in a single-step multiplex reaction to amplify each locus. Recombinant haplotypes were identified by their relative infrequency and were analyzed using THREELOC, a maximum-likelihood-analysis program, and an adaptation of CRI-MAP. The most likely order of these markers was cen-D9S109-D9S127-D9S53-ASS-tel with D9S109, D9S127, and D9S53 being separated by a genetic distance of approximately 3%. The order of the latter three markers did not however achieve statistical significance using the THREELOC program. 相似文献