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1.
Applied Biochemistry and Biotechnology - 相似文献
2.
Simms PJ Jeffries CT Huang Y Zhang L Arrhenius T Nadzan AM 《Journal of combinatorial chemistry》2001,3(5):427-433
A micellar electrokinetic chromatography (MEKC) method has been developed that can evaluate the purity of samples generated in combinatorial chemistry libraries. This method uses an open tube capillary (27 cm x 50 microm) along with a run buffer composed of sodium dodecyl sulfate (SDS), hydroxypropyl-beta-cyclodextrin, and sodium tetraborate coupled with UV detection. Neutral compounds and compounds that were insoluble in aqueous buffers could be analyzed under these conditions in approximately 3 min. The concentration of SDS and the concentration of hydroxypropyl-beta-cyclodextrin effected the separation. The affect on selectivity resulting from the addition of an organic modifier to the run buffer was examined. The low background absorbency of the run buffer made for easy detection of compounds that absorbed at low UV wavelengths. The quick analysis time made this suitable for analysis of combinatorial chemistry samples. 相似文献
3.
4.
A. Raith W. T. Perkins N. J. G. Pearce T. E. Jeffries 《Fresenius' Journal of Analytical Chemistry》1996,355(7-8):789-792
Laser ablation inductive coupled plasma – mass spectrometry (LA-ICP-MS) was used to analyse minor and trace elements in the hard parts of a shellfish, representing the environmental changes. A large, long-lived bivalve such as Arctica islandica can produce historical records of trace element fluctuations in seawater. Analytical traverses using LA-ICP-MS were performed from the inner to the outer wall of the shell at different locations. The development of the UV laser system now offers spatial resolution of craters of 10 m diameter, enabling several analyses between the various growthbands. The elemental changes between growthbands of the shell are discussed, showing the potential for precise determination of heavy-metal pollution over the years. 相似文献
5.
A. D. McCartt S. Gates P. Lappas J. B. Jeffries R. K. Hanson 《Applied physics. B, Lasers and optics》2012,106(3):769-774
The interaction of endospore-laden bioaerosols and shock waves is monitored with a combination of laser absorption and scattering.
Tests are performed in the Stanford aerosol shock tube for post-shock temperatures ranging from 400–1100 K. In situ laser
measurements at 266 and 665 nm provide a real-time monitor of endospore morphology. Scatter of visible light measures the
integrity of endospore structure, while absorption of UV light provides a monitor of biochemicals released by endospore rupture.
For post-shock temperatures greater than 750 K endospore morphological breakdown is observed. A simple theoretical model is
employed to quantify the optical measurements, and mechanisms leading to the observed data are discussed. 相似文献
6.
We present an all solid-state Yb:S-FAP laser system running on the three-level laser transition at 985 nm. The pump source was a high fill-factor laser diode bar, with the output reformatted using a two-mirror beamshaping system to produce a rectangular pump beam that focused to a square spot. A nearly on-axis multipassing system was used to obtain four pump passes through a 1.6 mm Yb:S-FAP laser crystal. Gain-switched three-level laser output was achieved with an efficiency of 4.3% with respect to incident pump power. Electro-optic Q-switching produced 0.12 mJ pulses for a pump pulse energy of 11 mJ. Intra-cavity second-harmonic generation yielded a maximum pulse energy at 492.5 nm of 12 μJ. 相似文献
7.
Spectrally resolved luminescence associated with the decay of bound multiexciton complexes in optically excited Ge:Ga is observed. This is the first reported observation of multiexciton complexes in p-type germanium. The observed spectra are consistent with the shell model for bound multiexciton complexes.No-phonon, TA, LA, and TO phonon assisted luminescence are observed. From these spectra, the energies of the LA, TA, and TO phonons in Ge:Ga are determined. 相似文献
8.
J. Luque J.B. Jeffries G.P. Smith D.R. Crosley 《Applied physics. B, Lasers and optics》2001,73(7):731-738
The combination of two-dimensional, planar laser-induced fluorescence (PLIF) and cavity ring-down (CRD) absorption spectroscopy
is applied to map quantitatively the spatial distributions of CH2O and CH in a methane/air flame at 25 Torr. Both species are detected in the same spectral region using the overlapping CH2O A 1
A
2
-X
1
A
1
41
0 and CH B-X(1,0 )bands. The combination of diagnostic techniques exploits the spatial resolution of LIF and the quantitative
CRD absorption measure of column density. The spatially resolved PLIF provides the distribution of absorbers and line-of-sight
CRD absorption the absolute number density needed for quantitative concentration images. The peak CH2O concentration is (3.5±1.4 )×1014 cm-3, or 1450±550 ppm at 1000 K. The lack of precise absorption cross-section data produces these large error limits. Although
a flame model predicts lower amounts, these large uncertainties limit this measurement’susefulness as a test of the flame
chemistry.
Received: 24 April 2001 / Revised version: 10 July 2001 / Published online: 10 October 2001 相似文献
9.
A mid-infrared absorption strategy with calibration-free wavelength-modulation-spectroscopy (WMS) has been developed and demonstrated
for real-time, in situ detection of nitric oxide in particulate-laden combustion-exhaust gases up to temperatures of 700 K.
An external-cavity quantum-cascade laser (ECQCL) near 5.2 μm accessed the fundamental absorption band of NO, and a wavelength-scanned,
1f-normalized WMS with second-harmonic detection (WMS-2f/1f) strategy was developed. Due to the external-cavity laser architecture, large nonlinear intensity modulation (IM) was observed
when the wavelength was modulated by injection-current modulation, and the IM indices were also found to be strongly wavelength-dependent
as the center wavelength was scanned with piezoelectric tuning of the cavity. A quantitative model of the 1f-normalized WMS-2f signal was developed and validated under laboratory conditions. A sensor was subsequently designed, built and demonstrated
for real-time, in situ measurements of NO across a 3 m path in the particulate-laden exhaust of a pulverized-coal-fired power
plant boiler. The 1f-normalized WMS-2f method proved to have better noise immunity for non-absorption transmission, than wavelength-scanned direct absorption. A
0.3 ppm-m detection limit was estimated using the R15.5 transition near 1927 cm−1 with 1 s averaging. Mid-infrared QCL-based NO absorption with 1f-normalized WMS-2f detection shows excellent promise for practical sensing in the combustion exhaust. 相似文献
10.
A. Raith W. T. Perkins N. J. G. Pearce T. E. Jeffries 《Analytical and bioanalytical chemistry》1996,355(7-8):789-792
Laser ablation inductive coupled plasma – mass spectrometry (LA-ICP-MS) was used to analyse minor and trace elements in the hard parts of a shellfish, representing the environmental changes. A large, long-lived bivalve such as Arctica islandica can produce historical records of trace element fluctuations in seawater. Analytical traverses using LA-ICP-MS were performed from the inner to the outer wall of the shell at different locations. The development of the UV laser system now offers spatial resolution of craters of 10 μm diameter, enabling several analyses between the various growthbands. The elemental changes between growthbands of the shell are discussed, showing the potential for precise determination of heavy-metal pollution over the years. 相似文献