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81.
Cobalt (0–130 μg) is determined spectrophotometrically at 625 nm after its adsorptive extraction as tetramethylene-bis(triphenylphosphonium) tetrathiocyanatocobalt(II) on microcrystalline benzophenone at pH 6.5 after dissolution of the solid phase in acetylacetone. The system is applied to the determination of cobalt (0.2–10%) in high-speed tool steels without prior separation of iron. 相似文献
82.
R D Chambers L L Feth E M Burns 《The Journal of the Acoustical Society of America》1986,80(6):1673-1680
The relation between the auditory brain stem potential called the frequency-following response (FFR) and the low pitch of complex tones was investigated. Eleven complex stimuli were synthesized such that frequency content varied but waveform envelope periodicity was constant. This was accomplished by repeatedly shifting the components of a harmonic complex tone upward in frequency by delta f of 20 Hz, producing a series of six-component inharmonic complex tones with constant intercomponent spacing of 200 Hz. Pitch-shift functions were derived from pitch matches for these stimuli to a comparison pure tone for each of four normal hearing adults with extensive musical training. The FFRs were recorded for the complex stimuli that were judged most divergent in pitch by each subject and for pure-tone signals that were judged equal in pitch to these complex stimuli. Spectral analyses suggested that the spectral content of the FFRs elicited by the complex stimuli did not vary consistently with component frequency or the first effect of pitch shift. Furthermore, complex and pure-tone signals judged equal in pitch did not elicit FFRs of similar spectral content. 相似文献
83.
Shea D. Burns 《Semigroup Forum》2001,63(2):191-201
No abstract.
September 13, 1999 相似文献
84.
J. H. Coste D. G. Garratt R. H. Burns C. W. Monier-Williams 《Analytical and bioanalytical chemistry》1936,107(5-6):222-222
85.
Thomas D. Scholz Steven R. Fleagle Trudy L. Burns David J. Skorton 《Magnetic resonance imaging》1989,7(6):643-648
The use of nuclear magnetic resonance (NMR) relaxation time measurements for characterization of abnormal cardiac tissue depends upon knowledge of variations of relaxation times of normal myocardium and determinants of these variations. We calculated in vitro NMR T1 and T2 relaxation times of canine myocardium from the four cardiac chambers, and determined hydroxyproline concentration (as a measure of collagen) and percent water content of the samples. We found both water content and T1 relaxation time of the right ventricle to be significantly greater than the left atrium (p < 0.05). T2 relaxation time of the left ventricle was found to be shorter than each of the other three chambers (p < 0.05). There were significant correlations between the spin-lattice relaxation time and both percent water content (r = 0.58) and hydroxyproline concentration (r = 0.45). A significant correlation was also found between T2 relaxation time and hydroxyproline concentration (r = 0.49). When T1 and T2 were adjusted for water and hydroxyproline content, there was no longer any evidence for significant interchamber differences for either T1 or T2. These data suggest that differences in NMR relaxation times exist among the four chambers of the normal canine heart. Furthermore, a major determinant of myocardial spin-lattice relaxation time is tissue water content while both collagen content and percent water content significantly contribute to variability in cardiac chamber T2 relaxation times. 相似文献
86.
D. T. Burns M. Harriott F. Glockling 《Fresenius' Journal of Analytical Chemistry》1987,327(7):701-703
Summary Methods have been developed for the determination, by carbon-furnace atomisation atomic absorption spectrophotometry, of inorganic and of total butyltin in seawater. Concentration/separations are based on the solvent extraction of organotin species directly into toluene and of inorganic tin as its tin(IV) 8-hydroxyquinoline chelate into chloroform. Detection limits are 0.7–0.8 ng.
Extraktion, Bestimmung und Speziation von Tributylzinn in Seewasser相似文献
87.
Blends of bisphenol-A polyarbonate (PC) and poly(ethylene terephthalate) (PET) has been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were prepared by screw extrusion and solution casting with weight fractions of PC in the blends varying from 0.90 to 0.10. From the measured glass transition temperature (Tg) and apparent weight fractions of PC and PET dissolved in each phase, it appears that PET dissolves more in the PC-rich phase than does the PC in the PET-rich phase. The composition-dependent values of the Flory–Huggins polymer–polymer–interaction parameter were determined and found to be from 0.054 to 0.037 for extruded blends at 275°C and from 0.058 to 0.040 for solution casting at 25°C. The interaction parameter decreases with increasing PET concentration. This result is consistent with the values of the Tgs, the microscopy study, and the measured extrudate swell ratios which show that compatibility increases more in the PET-rich compositions than in the PC-rich compositions. The PC–PET blends are not microscopically miscible for all the blend compositions. 相似文献
88.
The in situ hydrothermal reduction of Np(VI) to Np(IV) and Pu(VI) to Pu(IV) in the presence of 1,2-phenylenediphosphonic acid (PhP2) results in the crystallization of Np[C(6)H(4)(PO(3)H)(2)](2)·2H(2)O (NpPhP2) and Pu[C(6)H(4)(PO(3)H)(PO(3)H(2))][C(6)H(4)(PO(3)H)(PO(3))]·2H(2)O (PuPhP2), respectively. Similar reactions have been explored with Ce(IV) resulting in the isolation of the Ce(IV) phenylenediphosphonate Ce[C(6)H(4)(PO(3)H)(PO(3)H(2))][C(6)H(4)(PO(3)H)(PO(3))]·2H(2)O (CePhP2). Single crystal diffraction studies reveal that although all these three compounds all crystallize in the triclinic space group P1?, only PuPhP2 and CePhP2 are isotypic, whereas NpPhP2 adopts a distinct structure. In the cerium and plutonium compounds edge-sharing dimers of MO(8) polyhedra are bridged by the diphosphonate ligand to create one-dimensional chains. NpPhP2 also forms chains. However, the NpO(8) units are monomeric. The protonation of the ligands is also different in the two structure types. Furthermore, the NpO(8) polyhedra are best described as square antiprisms (D(4d)), whereas the CeO(8) and PuO(8) units are trigonal dodecahedra (D(2d)). Bond-valence parameters of R(o) = 1.972 and b = 0.538 have been derived for Np(4+) using a combination of the data reported in this work with that available in crystallographic databases. The UV-vis-NIR absorption spectra of NpPhP2 and PuPhP2 are also reported and used to confirm the tetravalent oxidation states. 相似文献
89.
Sarah Angus‐Dunne Prof. Dr. Robert C. Burns Donald C. Craig Geoffrey A. Lawrance 《无机化学与普通化学杂志》2010,636(5):727-734
The first example of a heteropolyoxomolybdate containing palladium(IV) was isolated and characterized by X‐ray crystallography. The palladium(IV) hexamolybdate, K0.75Na3.75[PdMo6O24H3.5]·17H2O, was isolated from an aqueous solution at pH 4.5 in the space group P\bar{1} , a 10.790(2), b 12.244(3), c 14.086(3) Å, α 113.77(1), β 90.41(1),γ 107.86(1)°, and the structure was determined using X‐ray diffraction methods, refining to a residual of 0.0301 for 5334 reflections. A formal “[PdMo6O24H3]5–” subunit exhibits the basic Anderson structure, with two [PdMo6O24H3]5– cluster anions in the structure bridged by a hydrogen atom (formally an H+) situated on a center of symmetry to give a “[Pd2Mo12O48H7]9–” dimeric anion. The palladium(IV) atom occupies a slightly distorted octahedral environment, with Pd–O distances ranging from 1.968 to 2.009 Å. 相似文献
90.
Experiments were performed to explore the use of two-photon planar laser-induced fluorescence (PLIF) of krypton gas for applications of scalar imaging in supersonic flows. Experiments were performed in an underexpanded jet of krypton, which exhibited a wide range of conditions, from subsonic to hypersonic. Excellent signal-to-noise ratios were obtained, showing the technique is suitable for single-shot imaging. The data were used to infer the distribution of gas density and temperature by correcting the fluorescence signal for quenching effects and using isentropic relations. The centerline variation of the density and temperature from the experiments agree very well with those predicted with an empirical correlation and a CFD simulation (FLUENT). Overall, the high signal levels and quantifiable measurements indicate that Kr-PLIF could be an effective scalar marker for use in supersonic and hypersonic flow applications. 相似文献