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11.
Abstract Methyl-substituted psoralens (4'-(hydroxymethyl)-4,5',8-trimethylpsoralen and 4,5',8-trimethylpsoralen) are found to yield an ene product as well as the expected [2+2] cycloaddition product from photochemical reaction with simple olefins. As determined by absorbance, liquid chromatography-mass spectrometry and nuclear magnetic resonance, both products are formed at the pyrone side of the respective psoralen. The product distribution is dependent on olefin concentration as well as the nature of the olefin. In deoxygenated solutions, cyclic olefins form as much as 50% ene product, while unsubstituted straight-chain olefins form as little as 3%. In oxygenated solutions, the product distribution is strongly affected by singlet oxygen. 相似文献
12.
Shawna Grosskopf Kathy Hayes Lori Taylor William L Weber 《The Journal of the Operational Research Society》2017,68(4):377-389
We use data envelopment analysis to model the educational production function, and then explore how a shift to weighted student funding using the student weights embedded in the Texas School Finance Formula would alter the allocation of inputs and potential outputs. School outputs are measured as value-added reading and math scores on standard achievement tests. We find that if school districts allocated their resources efficiently, then they would not allocate their resources to campuses according to the funding model weights. Policies that promote greater efficiency would also enhance equity in educational outcomes. 相似文献
13.
Donald E. Kiely Kathy Semk-gray James M. Riordan 《Journal of carbohydrate chemistry》2013,32(2):191-211
Abstract N,N'-Diacetyl-tri-O-acetylxylaramide (8) and N,N'-diacetyl-tri-O-acetylribaramide (20) were directly converted to the nitrogen heterocycle 6-acetamido-2,6-diacetyloxy-aza-1,4-cyclohexadlen-3-one (9) with sodium acetate in acetic anhydride. Treatment of tri-O-acetylxylaramide (7) or tri-O-acetylribaramide (19) with the same solvent-base combination gave the highly crystalline 2,3,5,6-tetraacetyloxypyridlne (30) as the principal product. Mechanistic considerations for the formation of these nitrogen heterocycles are presented. 相似文献
14.
Lieven Van Meulebroek Julie Vanden Bussche Kathy Steppe Lynn Vanhaecke 《Analytical and bioanalytical chemistry》2014,406(11):2613-2626
In this study, a generic extraction protocol and full-scan high-resolution Orbitrap-mass spectrometry (MS) detection method were developed, enabling the metabolomic screening for carotenoids in tomato fruit tissue. To this end, the carotenoids lutein, zeaxanthin, α-carotene, β-carotene, and lycopene (representing both xanthofylls and carotenes) were considered. The extraction procedure was optimized by means of a D-optimal design and consisted of a liquid–liquid extraction with methanol/tert-butyl methyl ether (1:1, v/v). The considered compounds were detected by a single-stage ExactiveTM mass spectrometer, operating at a mass resolution of 100,000 full width at half maximum. The validation study demonstrated excellent performance in terms of linearity (R 2?>?0.99), repeatability (CV?≤?10.6 %), within-laboratory reproducibility (CV?≤?12.2 %), and mean corrected recovery (ranging from 85 to 106 %). Additionally, a comparative evaluation towards well-established detection techniques, i.e., tandem mass spectrometry (MS/MS) and ultraviolet-visible spectroscopy (UV–VIS) photodiode array, indicated superior performance of high-resolution Orbitrap-MS with regard to specificity/selectivity and sensitivity (with limits of detection ranging from 1.0 to 3.8 pg μL?1). As a result, it may be concluded that high-resolution Orbitrap-MS is a suited alternative for UV–VIS or MS/MS in analyzing carotenoids and may offer significant value in carotenoid research because of the metabolomic screening possibilities. Figure
Development and validation of a full-scan high-resolution Orbitrap-MS method for the analysis of carotenoids in tomato fruit tissue. Validation enclosed comparison with MS/MS and UV-VIS PDA 相似文献
15.
Background
Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH. 相似文献16.
Nicewonger R Fowke A Nguyen K Ditto L Caserta J Harris M Baldino CM 《Molecular diversity》2003,7(2-4):247-252
A microwave-assisted method is described for monoacylating 7-amino-5-aryl-6-cyanopyrido[2,3-d]pyrimidines using excess acid chlorides in pyridine. A diacylated intermediate is effectively deacylated to the product amide by a macroporous-Tris resin. A small library of 17 amides was prepared to validate the method. The integration of commercial microwave technology into the ArQule chemistry platform is also discussed. 相似文献
17.
One hundred twenty children in kindergarten and grades 2, 4, and 6 were individually interviewed with five Piagetian tasks to determine the grade level at which most have constructed transitive reasoning, unit iteration, and the conservation of speed. The responses were categorized as “successful,”“unsuccessful,” or “transitional.” By combining the “successful” and “transitional” categories, it was found that the children reasoned transitively by second grade (70.0%) and demonstrated unit iteration and conservation of speed by sixth grade (70.0% and 83.3%, respectively). It was concluded that the construction of the logic necessary to make sense of the measurement of time is generally not complete before sixth grade. 相似文献
18.
S. Alexander Schumaker Andrew M. Knisely John L. Hoke Keith D. Rein 《Proceedings of the Combustion Institute》2021,38(3):3623-3632
The detonation characteristics of methane–oxygen mixtures at pre-detonation pressures of 101–1,013 kPa were investigated in a detonation tube. Both pure methane–oxygen mixtures and mixtures with argon dilution were explored. Measurements made include cell sizes via soot foil, wave speed via high speed ion probes / pressure transducers, and temperature / H2O molar concentration profiles via 100 kHz absorption spectroscopy. Measured cell widths agreed with predicted cell widths based on a ZND length correlation. In addition, the power law fit of cell width with pre-detonation pressure agreed with previous data at less than 101 kPa. Measured detonation wave speeds agreed within 3% of Chapmen-Jouguet for all cases. H2O molar density and temperature were successfully captured up to 507 kPa. However, above 507 kPa pre-detonation pressure, low signal to noise ratio and poor spectral fits at the extreme conditions of the von Neumann spike resulted in unacceptable uncertainty. These results provide a unique dataset to validate kinetics models and high-fidelity computation fluid dynamics codes for methane-oxygen detonations at elevated pre-detonation pressures relevant to rotating detonation rocket engines. 相似文献
19.
Muthiah Manoharan Akin Akinc Rajendra K. Pandey June Qin Philipp Hadwiger Matthias John Kathy Mills Klaus Charisse Martin A. Maier Lubomir Nechev Emily M. Greene Pradeep S. Pallan Eriks Rozners Kallanthottathil G. Rajeev Martin Egli 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2011,123(10):2332-2336
20.
Stephen MT Hoke Gaoyang Liang A Irina Mutiu Julie Genereaux Christopher J Brandl 《BMC biochemistry》2007,8(1):16