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71.
Catalytic (DHQD)2PHAL as modified by added benzoic acid, is an off-the-shelf catalyst-additive combination for effecting catalytic asymmetric bromolactonization reactions. This combination delivers bromolactones with asymmetric induction at a comparable level to bespoke catalysts previously optimized for particular substrate classes. 相似文献
72.
A study of 400 Hz sound focusing and ducting effects in a packet of curved nonlinear internal waves in shallow water is presented. Sound propagation roughly along the crests of the waves is simulated with a three-dimensional parabolic equation computational code, and the results are compared to measured propagation along fixed 3 and 6 km source/receiver paths. The measurements were made on the shelf of the South China Sea northeast of Tung-Sha Island. Construction of the time-varying three-dimensional sound-speed fields used in the modeling simulations was guided by environmental data collected concurrently with the acoustic data. Computed three-dimensional propagation results compare well with field observations. The simulations allow identification of time-dependent sound forward scattering and ducting processes within the curved internal gravity waves. Strong acoustic intensity enhancement was observed during passage of high-amplitude nonlinear waves over the source/receiver paths, and is replicated in the model. The waves were typical of the region (35 m vertical displacement). Two types of ducting are found in the model, which occur asynchronously. One type is three-dimensional modal trapping in deep ducts within the wave crests (shallow thermocline zones). The second type is surface ducting within the wave troughs (deep thermocline zones). 相似文献
73.
McAlexander Harley R. Giles Stephen A. Crouch Rebecca A. Peel Hannah R. Jones Stacy Bednar Anthony J. Shukla Manoj K. 《Structural chemistry》2020,31(3):975-982
Structural Chemistry - Alternatives to legacy munitions and explosives, materials that feature increased stability against external stimuli without compromising their energetic yields are currently... 相似文献
74.
Stacy J. Keding Natalie A. Dales Sejin Lim Danielle Beaulieu Daniel H. Rich 《合成通讯》2013,43(23):4463-4470
(3R)-amino-(2S)-hydroxy heptanoic acid (AHHpA) was synthesized via asymmetric aminohydroxylation and coupled with di-and tripeptides to form three compounds that inhibit MetAP-1 with IC50 values in the low micromolar range. 相似文献
75.
Iris H Hall E Stacy Hall L K Chi M C Miller Iii Ken F Bastow A Sood B F Spielvogel 《应用有机金属化学》1992,6(2):229-239
Studies on the mode of action of two boroncontaining anti-neoplastic agents, ethylamine-carboxyborane and triphenylphosphine-carboxyborane, are reported. The major site of inhibition was in the pyrimidine de nove synthetic pathway at orotidine monophosphate decarboxylase activity. Additional sites which may facilitate the inhibition of cell growth were IMP dehydrogenase, thymidine kinase, TMP kinase and TDP kinase, m-RNA, r-RNA and t-RNA polymerase activities as well as topoisomerase II activity. The reduction in enzyme activities led to sufficient reduction of d(NTP) levels to suppress DNA synthesis and cell growth. DNA strand scission was evident in the presence of drug. Multiple modes of action are common with amine-carboxyboranes. Acute toxicity studies in mice showed that both agents were safe in their therapeutic range based on organ weights, histological tissue sections, clinical chemistry values and hematopoietic parameters. 相似文献
76.
77.
Jordana Bandaru Jeffrey W. Beeman Eugene E. Haller Stacy Samperi Nancy M. Haegel 《Infrared Physics & Technology》2002,43(6):353-360
Extended long wavelength response to 200 μm (50 cm−1) has been observed in Ge:Sb blocked impurity band (BIB) detectors with ND1×1016 cm−3. The cut-off wavelength increases from 150 μm (65 cm−1) to 200 μm (50 cm−1) with increasing bias. The responsivity at long wavelengths was lower than expected. This can be explained by considering the observed Sb diffusion profile in a transition region between the blocking layer and active layer. BIB modeling is presented which indicates that this Sb concentration profile increases the electric field in the transition region and reduces the field in the blocking layer. The depletion region consists partially of the transition region between the active and blocking layer, which could contribute to the reduced long wavelength response. The field spike at the interface is the likely cause of breakdown at a lower bias than expected. 相似文献
78.
L. C. Bourne Marvin L. Cohen William N. Creager Michael F. Crommie Angelica M. Stacy A. Zettl 《Physics letters. A》1987,120(9):494-496
Resistive and magnetic measurements on Y---Ba---Cu---O samples indicate transitions to the superconducting state beginning near 100 K with transition widths typically around 15 K. 相似文献
79.
Ethan A. Wappes Stacy C. Fosu Trevor C. Chopko Prof. Dr. David A. Nagib 《Angewandte Chemie (International ed. in English)》2016,55(34):9974-9978
The Cδ?H amination of unactivated, secondary C?H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3?)‐mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2) as I3?, this approach precludes undesired I2‐mediated decomposition which can otherwise limit synthetic utility to only weak C(sp3)?H bonds. The mechanism of this triiodide‐mediated cyclization of unbiased, secondary C(sp3)?H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates. 相似文献
80.
The one-pot synthesis of alumina-supported metal oxides via self-assembly of a metal precursor and aluminum isopropoxide in the presence of triblock copolymer (as a structure directing agent) is described in detail for nickel oxide. The resulting mesoporous mixed metal oxides possess p6 mm hexagonal symmetry, well-developed mesoporosity, relatively high BET surface area, large pore widths, and crystalline pore walls. In comparison to pure alumina, nickel aluminum oxide samples exhibited larger mesopores and improved thermal stability. Also, long-range ordering of the aforementioned samples was observed for nickel molar percentages as high as 20%. The generality of the recipe used for the synthesis of mesoporous nickel aluminum oxide was demonstrated by preparation of other alumina-supported metal oxides such as MgO, CaO, TiO 2, and Cr 2O 3. This method represents an important step toward the facile and reproducible synthesis of ordered mesoporous alumina-supported materials for various applications where large and accessible pores with high loading of catalytically active metal oxides are needed. 相似文献