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101.
Joy S. Finney Peter H. Bach Mary-Clare Bushell Neil M. Gregg David G. Taylor 《Magnetic resonance imaging》1990,8(6):713-721
Renal cortical and medullary spin-lattice (T1) relaxation times were measured at various time points over a period of 56 days following the administration of a single i.p. injection of 100 mg/kg 2-bromoethanamine hydrobromide (BEA), 200 mg/kg hexachloro-1,3-butadiene (HCBD) or 100 mg/kg puromycin aminonucleoside (PAN) to male Wistar rats. Administration of a single injection of HCBD caused a dramatic, immediate rise in the cortical T1 values above control values, and these levels remained elevated until, by Day 28 postinjection the levels were back to control values. Administration of BEA also caused an elevation in cortical T1 values, but in this case these values remained above control values for the rest of the study. The administration of PAN did not produce any significant increases in cortical T1 values until 14 days postinjection. The elevated T1 values remained above control values for the rest of the study. These increases observed in cortical T1 values appeared to be mirrored by decreases in medullary T1 values. Increases in cortical T1 values were accompanied by visual changes in the NMR images and enlargement of the kidneys. The histological findings were consistent with the NMR data, confirming that morphologically the tissues did show a full recovery by Day 28 in the HCBD-treated animals. This was not the case following injection of both BEA and PAN, where necrosis was not reversible and there was no recovery of the tissues. 相似文献
102.
103.
104.
Steven R. Kass Hangzhou Guo Gregg D. Dahlke 《Journal of the American Society for Mass Spectrometry》1990,1(5):366-371
The thiomethyl anion (1) has been generated by fluorodesilylation of trimethylsilylmethanethiol in a variable-temperature flowing afterglow device. The proton affinity (1649 ± 12 kJ mol?1) and electron affinity (0.67 ± .13 eV) were determined and compared to a previously reported molecular orbital calculation. Isomerization via a 1,2-proton shift does not take place between ?40° and 100°C despite a 156 kJ mol?1 driving force. Ion-molecule reactions of 1 were examined with a number of reagents including N20, O2, CS2, COS, and CO2, Hydride ion transfer was observed in every case, along with other products, and thermodynamic information has been derived. 相似文献
105.
106.
Cellulase adsorption and an evaluation of enzyme recycle during hydrolysis of steam-exploded softwood residues 总被引:1,自引:0,他引:1
Lu Yanpin Yang Bin Gregg David Saddler John N. Mansfield Shawn D. 《Applied biochemistry and biotechnology》2002,98(1-9):641-654
The sugar yield and enzyme adsorption profile obtained during the hydrolysis of SO2-catalyzed steam-exploded Douglas-fir and posttreated steamexploded Douglas-fir substrates were determined. After hot alkali
peroxide posttreatment, the rates and yield of hydrolysis attained from the posttreated Douglas-fir were significantly higher,
even at lower enzyme loadings, than those obtained with the corresponding steam-exploded Douglas-fir. The enzymatic adsorption
profiles observed during hydrolysis of the two substrates were significantly different. Ultrafiltration was employed to recover
enzyme in solution (supernatant) and reused in subsequent hydrolysis reactions with added, fresh substrate. These recycle
findings suggested that the enzyme remained relatively active for three rounds of recycle. It is likely that enzyme recovery
and reuse during the hydrolysis of posttreated softwood substrates could lead to reductions in the need for the addition of
fresh enzyme during softwood-based bioconversion processes. 相似文献
107.
Chittari Pabba Hong-Jun Wang Susan R. Mulligan Zhen-Jia Chen Todd M. Stark Brian T. Gregg 《Tetrahedron letters》2005,46(44):7553-7557
A highly efficient one-pot two-step microwave procedure was developed for the synthesis of 1-aryl-1H-indazoles. Microwave heating of 2-halobenzaldehydes or 2-haloacetophenones with phenylhydrazines at 160 °C for 10 min quantitatively yielded the arylhydrazones, which were further cyclized to give 1-aryl-1H-indazoles via CuI/diamine-catalyzed N-arylation under microwave heating (160 °C, 10 min). Good to excellent yields were observed for 2-iodo, 2-bromo, and 2-chloro benzaldehydes or acetophenones. 相似文献
108.
A congener-specific method based on high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ES-MS/MS) in the negative ion mode was developed for the analysis of hexabromocyclododecane (HBCDD). On a C(18) analytical column, with a methanol/water mobile phase, the alpha-isomer was completely resolved from the beta- and gamma-isomers while the beta- and gamma-isomers were sufficiently resolved at half their peak heights. The ES spray voltage strongly influenced the intensity of the ion signal. For MS, a source temperature of 500 degrees C and a collision energy of 50 eV were found to be optimum for the [M-H](-) to Br(-) transition. Run-to-run and day-to-day (n = 3) variability was minimal, with relative standard deviations of 2.6-4.1 and 2.4-4.4%, respectively. The limit of detection was 4-6 pg on-column. When applied to tissue samples from Lake Winnipeg fish both alpha- and gamma-isomers of HBCDD were found in low-ng/g (lipid corrected) concentrations. 相似文献
109.
Dhanpat Rai Nancy J. Hess Linfeng Rao Zhicheng Zhang Andrew R. Felmy Dean A. Moore Sue B. Clark Gregg J. Lumetta 《Journal of solution chemistry》2002,31(5):343-367
The main objective of this study was to develop a thermodynamic model for predicting Cr(III) behavior in concentrated NaOH and in mixed NaOH–NaNO3 solutions for application to developing effective caustic leaching strategies for high-level nuclear waste sludges. To meet this objective, the solubility of Cr(OH)3(am) was measured in 0.003 to 10.5 m NaOH, 3.0 m NaOH with NaNO3 varying from 0.1 to 7.5 m, and 4.6 m NaNO3 with NaOH varying from 0.1 to 3.5 m at room temperature (22 ± 2°C). A combination of techniques, X-ray absorption spectroscopy (XAS) and absorptive stripping voltammetry analyses, were used to determine the oxidation state and nature of aqueous Cr. A thermodynamic model, based on the Pitzer equations, was developed from the solubility measurements to account for dramatic increases in aqueous Cr with increases in NaOH concentration. The model includes only two aqueous Cr species, Cr(OH)
4
–
and Cr2O2(OH)
4
–
(although the possible presence of a small percentage of higher oligomers at >5.0 m NaOH cannot be discounted) and their ion–interaction parameters with Na+. The logarithms of the equilibrium constants for the reactions involving Cr(OH)
4
–
[Cr(OH)3(am) + OH– Cr(OH)
4
–
] and Cr2O2(OH)
4
2–
[2Cr(OH)3(am) + 2OH– Cr2O2(OH)
4
2–
+ 2H2O] were determined to be –4.36 ± 0.24 and –5.24 ± 0.24, respectively. This model was further tested and provided close agreement between the observed Cr concentrations in equilibrium with Cr(OH)3(am) in mixed NaOH–NaNO3 solutions and with high-level tank sludges leached with and primarily containing NaOH as the major electrolyte. 相似文献
110.
Nirmala Ramanujam Michele Follen Mitchell Anita Mahadevan-Jansen Sharon L. Thomson Gregg Staerkel Anais Malpica Thomas Wright Neely Atkinson Rebecca Richards-Kortum 《Photochemistry and photobiology》1996,64(4):720-735
Abstract— A portable fluorimeter was developed and utilized to acquire fluorescence spectra from 381 cervical sites in 95 patients at 337, 380 and 460 nm excitation immediately prior to colposcopy. A multivariate statistical algorithm was used to extract clinically useful information from tissue spectra acquired in vivo. Two full-parameter algorithms were developed using tissue fluorescence emission spectra at all three excitation wavelengths (161 excitation-emission wavelength pairs) for cervical precancer (squamous intraepithelial lesion [SIL]) detection: a screening algorithm that discriminates between SIL and non-SIL with a sensitivity of 82 ± 1.4% and specificity of 68 ± 0.0%, and a diagnostic algorithm that differentiates high-grade SIL from non-high-grade SIL with a sensitivity and specificity of 79 ± 2% and 78 ± 6%, respectively. Multivariate statistical analysis was also employed to reduce the number of fluorescence excitation-emission wavelength pairs needed to redevelop algorithms that demonstrate a minimum decrease in classification accuracy. Two reduced-parameter algorithms that employ fluorescence intensities at only 15 excitation-emission wavelength pairs were developed: the screening algorithm differentiates SIL from non-SIL with a sensitivity of 84 ± 1.5% and specificity of 65 ± 2% and the diagnostic algorithm discriminates high-grade SIL from non-high-grade SIL with a sensitivity and specificity of 78 ± 0.7% and 74 ± 2%, respectively. Both the full-parameter and reduced-parameter screening algorithms discriminate between SIL and non-SIL with a similar specificity (±5%) and a substantially improved sensitivity relative to Pap smear screening. A comparison of the full-parameter and reduced-parameter diagnostic algorithms to colposcopy in expert hands indicates that all three have a very similar sensitivity and specificity for differentiating high-grade SIL from non-high-grade SIL. 相似文献