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排序方式: 共有193条查询结果,搜索用时 15 毫秒
71.
Dr. David E. Chavez Dr. Damon A. Parrish Dr. Lauren Mitchell 《Angewandte Chemie (International ed. in English)》2016,55(30):8666-8669
Several new energetic ethyl ethers of 1,2,4,5‐tetrazine have been synthesized. These molecules display good thermal stability, good oxygen balance, and high densities. Included in these studies are a 2,2,2‐trinitroethoxy 1,2,4,5‐tetrazine and two fluorodinitroethoxy 1,2,4,5‐tetrazines. One of these compounds was converted into the di‐N‐oxide derivative. The sensitivity of these materials towards destructive stimuli was determined, and overall the materials show promising energetic performance properties. 相似文献
72.
73.
Iyer G Ramaswamy S Asher D Mehta U Leahy A Chung F Cheng KS 《Journal of chromatography. A》2011,1218(26):3973-3981
A method for flow-through purification of viruses and virus like nano-particles using a combination of binding and size-exclusion chromatography was developed. This technique relies on minimizing the external surface area per unit volume available for virus binding by increasing the mean diameter of the beads used in the column. At the same time the impurity binding capacity of the column is maximized by utilizing beads with multiple functionalities of the optimum size. Purification of different types of viruses and virus-like-particles could be achieved using this technique. Flow-through purification of influenza virus using this technique yielded virus recoveries greater than 70-80% coupled with impurity removal greater than 80%. Finally an approach to optimize and facilitate process development using this technology is presented. Since the impurity binding occurs via a non-specific mechanism and virus recovery is achieved through reduced surface area, the technique is not limited to specific types of viruses and offers the potential as a universal purification tool. 相似文献
74.
Gao H Joo YH Parrish DA Vo T Shreeve JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(16):4613-4618
Synthesis, characterization, and thermolysis studies of 1-amino-1-hydrazino-2,2-dinitroethene (2) and salts thereof are reported. These compounds have been fully characterized by IR and NMR spectroscopy, elemental analysis, differential scanning calorimetry (DSC), density, and impact sensitivity measurements. Compound 2 decomposes at 124.5 °C (DSC) and the salts decompose over the range 138.6-181.6 °C, thus showing higher thermostability. The calculated detonation pressures (P) for these salts range from 27.2 to 37.8 GPa, and detonation velocities (vD) fall between 8424 to 9482 m s(-1); these properties make them competitive energetic materials. 相似文献
75.
Rodney L. Willer Robson F. Storey Christopher G. Campbell Steven W. Bunte Damon Parrish 《Journal of heterocyclic chemistry》2012,49(4):919-925
Reaction coordinate mapping was used to study the reaction of 3,4‐diamino[1,2,5]oxadiazole (3,4‐diaminofurazan) and 3,4‐diamino[1,2,5]thiadiazole with glyoxal. The thiadiazole was known to give a good yield of [1,2,5]thiadiazolo[3,4‐b]pyrazine, whereas the oxadiazole had not yielded, until now, [1,2,5]oxadiazolo[3,4‐b]pyrazine (or furazano[2,3‐b]pyrazine). The calculations suggested that the diols, 5,6‐dihydroxy‐4,5,6,7‐tetrahydro[1,2,5]oxadiazolo[3,4‐b]pyrazine and 5,6‐dihydroxy‐4,5,6,7‐tetrahydro[1,2,5]thiadiazolo[3,4‐b]pyrazine should be stable intermediates, and once formed, should provide a pathway to the target compounds via two dehydration steps, under forcing conditions. With this information in mind, the reactions of 3,4‐diamino[1,2,5]oxadiazole with glyoxal and pyruvic aldehyde were re‐examined. The reaction of 3,4‐diamino[1,2,5]oxadiazole with glyoxal and pyruvic aldehyde produced, under slightly basic conditions, a near quantitative yield of the expected initial products, 5,6‐dihydroxy‐4,5,6,7‐tetrahydro[1,2,5]oxadiazolo[3,4‐b]pyrazine and the 5‐methyl analog, respectively. The diols were easily isolated by lyophilizing the aqueous reaction mixture. The diols were pyrolized on silica gel at 160°C to give the desired [1,2,5]oxadiazolo[3,4‐b]pyrazine and the 5‐methyl analog. Both compounds were easily reduced to the corresponding 4,5,6,7‐tetrahydro‐derivative using sodium borohydride in THF/methanol. The [1,2,5]oxadiazolo[3,4‐b]pyrazine also displayed other interesting chemistry. 相似文献
76.
Yang X Zhang AY Wheeler DA Bond TC Gu C Li Y 《Analytical and bioanalytical chemistry》2012,402(2):687-691
This paper reports the first step toward the development of a glucose biosensor based on Raman spectroscopy and a photonic
crystal fiber (PCF) probe. Historically, it has been very challenging to detect glucose directly by Raman spectroscopy due
to its inherently small Raman scattering cross-section. In this work, we report the first quantitative glucose Raman detection
in the physiological concentration range (0–25 mM) with a low laser power (2 mW), a short integration time (30 s), and an
extremely small sampling volume (∼50 nL) using the highly sensitive liquid-filled PCF probe. As a proof of concept, we also
demonstrate the molecular specificity of this technique in the presence of a competing sugar, such as fructose. High sensitivity,
flexibility, reproducibility, low cost, small sampling volume, and in situ remote sensing capability make PCF a very powerful
platform for potential glucose detection based on Raman spectroscopy. 相似文献
77.
Damon Kent Steven Pas Suming Zhu Gui Wang Matthew S. Dargusch 《Applied Physics A: Materials Science & Processing》2012,107(4):835-841
A study was undertaken on a Ti–25Nb–3Mo–3Zr–2Sn alloy using differential scanning calorimetry (DSC) in order to improve understanding of the precipitation reactions occurring during aging heat treatments. The investigation showed that isothermal ω phase can be formed in the cast and solution treated alloy at low aging temperatures. An exothermic peak in the temperature range of 300 to 400°C was detected for precipitation of the ω phase, with approximate activation energy of 176 kJ/mol. The ω phase begins to dissolve at temperatures around 400°C and precipitation of the α phase is favoured at higher temperatures between 400°C and 600°C. An exothermic peak with activation energy of 197 kJ/mol was measured for precipitation of the α phase. Deformation resulting in the formation of the stress induced α″ phase altered the DSC heating profile for the solution treated alloy. The exothermic peak associated with precipitation of the ω phase was not detected during heating of the deformed material and increased endothermic heating associated with recovery and recrystallisation was observed. 相似文献
78.
Damon Scott 《Journal of Theoretical Probability》1990,3(1):1-7
We present a space-homogeneous, time-inhomogeneous random walk that behaves as if it were a simple random walk ind dimensions, whered is not necessarily an integer. Analogues of the Local Central Limit Theorem, Zero-One Laws, distance, angle, asymptotics on the Green's function and the hitting probability, recurrence and transience, and results about the intersection behavior of the random walk paths are obtained. 相似文献
79.
The dianion of N-benzyl-2-propynamide can be generated by the treatment of 4 with two equivalents of LDA at ?65° or ethylmagnesium bromide at ?20°. The trilithio species 6 is readily formed using 3 equivalents of LDA. Reaction of 5 with aldehydes or ketones produce hydroxypropynamides 9 in good yields. Silation of 5a with chlorotrimethylsilane produces N-benzyl-3-trimethylsilyl-2-propynamide ( 13 ) in high yield. Reduction of 9 furnishes either fully saturated amides 15 or partially reduced cis-olefins 16 or 18 . Compounds 16 , on heating, rearrange to 4-ketoamides 17 . Carboxylation of 5a with carbon dioxide produces 3-benzyl-2,4-dioxo-5-oxazidinylacetic acid ( 11 ). Warming 11 in dimethyl sulfoxide results in the loss of carbon dioxide and the formation of N-benzylpyruvamide ( 21 ). 相似文献
80.
Stephen C. Bergmeier Steven J. Katz Junfeng Huang Howard McPherson Patrick J. Donoghue Damon D. Reed 《Tetrahedron letters》2004,45(26):5011-5014
We have found that aziridines will react with a variety of π-nucleophiles in intramolecular cyclization reactions to produce nitrogen containing core structures found in a variety of bioactive molecules. These cyclizations are more general and facile than corresponding intermolecular reactions. We have examined the effects of ring size, π-nucleophile identity and substitution on this reaction. 相似文献