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1.
2.
M. B. Cooper P. A. Burns B. L. Tracy M. J. Wilks G. A. Williams 《Journal of Radioanalytical and Nuclear Chemistry》1994,177(1):161-184
Re-suspension studies on soils contaminated with plutonium during nuclear weapons tests were performed by use of a mechanical dust-raising apparatus. Airborne dust was analyzed in terms of mass and241Am activities for particle sizes less than 7 m. The AMAD was determined as 4.8 to 6 m, for re-suspended soil. Also, surface soil was characterized in the laboratory by means of sieving and microparticle classification, yielding mass and241Am activity distributions with respect to size. Data indicate the granularity of plutonium contamination at both major and minor trial sites. Depth profile analyses for undisturbed, areas demonstrate that most (74% on average) of the americium and plutonium activity is found in the top 10 mm of soil. Plutonium and americium activities were found to be enhanced in the inhalable fraction over their values, in the total soil, and the enhancement factors were similar in re-suspended dust and surface soil. Observed enhancement factors ranged from 3.7 to 32.5. 相似文献
3.
Caignan GA Deshmukh R Wilks A Zeng Y Huang HW Moënne-Loccoz P Bunce RA Eastman MA Rivera M 《Journal of the American Chemical Society》2002,124(50):14879-14892
The origin of the unusual regioselectivity of heme oxygenation, i.e. the oxidation of heme to delta-biliverdin (70%) and beta-biliverdin (30%), that is exhibited by heme oxygenase from Pseudomonas aeruginosa (pa-HO) has been studied by (1)H NMR, (13)C NMR, and resonance Raman spectroscopies. Whereas resonance Raman indicates that the heme-iron ligation in pa-HO is homologous to that observed in previously studied alpha-hydroxylating heme oxygenases, the NMR spectroscopic studies suggest that the heme in this enzyme is seated in a manner that is distinct from that observed for all other alpha-hydroxylating heme oxygenase enzymes for which a structure is known. In pa-HO, the heme is rotated in-plane approximately 110 degrees, so the delta-meso-carbon of the major orientational isomer is located within the HO-fold in the place where the alpha-hydroxylating enzymes typically place the alpha-meso-carbon. The unusual heme seating displayed by pa-HO places the heme propionates so that these groups point in the direction of the solvent-exposed heme edge and appears to originate in large part from the absence of stabilizing interactions between the polypeptide and the heme propionates, which are typically found in alpha-hydroxylating heme oxygenase enzymes. These interactions typically involve Lys-16 and Tyr-112, in Neisseriae meningitidis HO, and Lys-16 and Tyr-134, in human and rat HO-1. The corresponding residues in pa-HO are Asn-19 and Phe-117, respectively. In agreement with this hypothesis, we found that the Asn-19 Lys/Phe-117 Tyr double mutant of pa-HO exists as a mixture of molecules exhibiting two distinct heme seatings; one seating is identical to that exhibited by wild-type pa-HO, whereas the alternative seating is very similar to that typical of alpha-hydroxylating heme oxygenase enzymes and is related to the wild-type seating by approximately 110 degrees in-plane rotation of the heme. Furthermore, each of these heme seatings in the pa-HO double mutant gives rise to a subset of two heme isomeric orientations that are related to each other by 180 degrees rotation about the alpha-gamma-meso-axis. The coexistence of these molecules in solution, in the proportions suggested by the corresponding area under the peaks in the (1)H NMR spectrum, explains the unusual regioselectivity of heme oxygenation observed with the double mutant, which we found produces alpha- (55%), delta- (35%), and beta-biliverdin (10%). Alpha-biliverdin is obtained by oxidation of the heme seated similar to that of alpha-hydroxylating enzymes, whereas beta- and delta-biliverdin are formed from the oxidation of heme seated as in wild-type pa-HO. 相似文献
4.
Self-injection length in La0.7Ca0.3MnO3-YBa2Cu3O7-δ ferromagnet-superconductor multilayer thin films
We have carried out extensive studies on the self-injection problem in barrierless heterojunctions between La0.7Ca0.3MnO3 (LCMO) and YBa2Cu3O7-δ (YBCO) thin films. The heterojunctions were formed in situ by sequentially growing LCMO and YBCO films on 〈100〉 LaAlO3 (LAO) substrate using a pulsed laser deposition (PLD) system. YBCO micro-bridges with 64 μm width were patterned both on
the LAO (control) and LCMO side of the substrate. Critical current, I
c, was measured at 77 K on both the control side as well as the LCMO side for different YBCO film thickness. It was observed
that while the control side showed a J
c of ∼ 2 × 106 A/cm2, the LCMO side showed about half the value for the same thickness (1800 ?). The difference in J
c indicates that a certain thickness of YBCO has become ‘effectively’ normal due to self-injection. From the measurement of
J
c at two different thicknesses (1800 ? and 1500 ?) of YBCO films both on the LAO as well as the LCMO side, the value of self-injection
length (at 77 K) was estimated to be ∼ 900 ?. To the authors’ best knowledge, this is the first time that self-injection length
has been quantified. A control experiment carried out with LaNiO3 deposited by PLD on YBCO did not show any evidence of self-injection. 相似文献
5.
Ping Y Shepherd R Lasinski BF Tabak M Chen H Chung HK Fournier KB Hansen SB Kemp A Liedahl DA Widmann K Wilks SC Rozmus W Sherlock M 《Physical review letters》2008,100(8):085004
We report the first direct measurements of total absorption of short laser pulses on solid targets in the ultrarelativistic regime. The data show an enhanced absorption at intensities above 10(20) W/cm(2), reaching 60% for near-normal incidence and 80%-90% for 45 degrees incidence. Two-dimensional particle-in-cell simulations demonstrate that such high absorption is consistent with both interaction with preplasma and hole boring by the intense laser pulse. A large redshift in the second harmonic indicates a surface recession velocity of 0.035c. 相似文献
6.
7.
Jonathan T. Husband Yujie Xie Thomas R. Wilks Louise Male Miquel Torrent-Sucarrat Vasilios G. Stavros Rachel K. O'Reilly 《Chemical science》2021,12(31):10550
Fluorescent dyes that exhibit high solid state quantum yields and sensitivity to the mechanical properties of their local environment are useful for a wide variety of applications, but are limited in chemical diversity. We report a trityl-functionalised maleimide that displays rigidochromic behaviour, becoming highly fluorescent when immobilised in a solid matrix, while displaying negligible fluorescence in solution. Furthermore, the dye''s quantum yield is shown to be sensitive to the nature of the surrounding matrix. Computational studies reveal that this behaviour arises from the precise tuning of inter- and intramolecular noncovalent interactions. This work expands the diversity of molecules exhibiting solid state environment sensitivity, and provides important fundamental insights into their design.In this study, by systematic tuning of imide substituent a maleimides dye with sensitivity to its solid-state environment was investigated. 相似文献
8.
9.
William Arthur Reginald Wilks 《Colloid and polymer science》1912,11(1):12-17
Ohne ZusammenfassungUebersetzt von J. Matula, Wien. 相似文献
10.
The aim of this paper is to establish the heat transfer characteristics of the flow downstream of a heated jet source of momentum issuing into an aligned uniform stream. Perturbation solutions about limiting similarity states at the jet and downstream are obtained. The formulation allows also for full numerical solution. A satisfactory reconciliation between numerical and perturbation solutions is demonstrated. 相似文献