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1.
Leslie M. Werbel Dennis J. Mcnamara Norman L. Colbry Judith L. Johnson Margaret J. Degnan Barbara Whitney 《Journal of heterocyclic chemistry》1979,16(5):881-894
The synthesis of a series of N,N-dialkyl-6-(substituted phenyl)-1,2,4,5-tetrazin-3-amines (IV) by two routes is described. The first route (Scheme I) involved the oxidative cyclization of formazans (II) to 3-bromo-6-(substituted phenyl)-1,2,4,5-tetrazines (III), followed by treatment with amines. The second (Scheme II) utilized the treatment of 3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VII) with amines to provide the desired products. The intermediate 3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VII) were obtained by thiobenzoylation of hydrazinecarbohydrazonothioic acid methyl ester with [[(substituted phenyl)thioxomethyl]thio]-acetic acids (V) to afford the 1,2-dihydro-3-(methylthio)-6-(substituted phenyl)-1,2,4,5-tetrazines (VI). Oxidation with bromine in acetic acid provided the desired intermediates. The target 6-(substituted phenyl)-1,2,4,5-tetrazin-3-amines (IV) displayed modest antimalarial activity. 相似文献
2.
Dimethylphenylsilyllithium undergoes a highly diastereoselective conjugate addition to chiral naphthyloxazoline 11. Electrophilic trapping of the resulting aza-enolate affords the tandem addition product (12) in high yields as a single diastereomer. The silicon, thus incorporated, may be protodesilylated and undergoes a Tamao oxidation to afford the corresponding alcohol. By chemical modification of the oxazoline, both the gamma-lactone (28) and the delta-lactone (37) were prepared. Reduction of each lactone followed by oxidation of the ensuing diol gave the keto aldehyde. Double reductive amination of the 1,4-dicarbonyl (from the gamma-lactone) allowed the synthesis of two novel hexahydrobenz[e]indoles, 20 and 35. Double reductive amination of the 1,5-dicarbonyl (from the delta-lactone) gave access to two novel octahydrobenzo[f]quinolines, 41 and 43. An unprecedented rearrangement of nitro alcohol 26 into lactone 28 is described and a reasonable mechanism for its formation postulated. 相似文献
3.
Peterkin R.E. Jr. Degnan J.H. Hussey T.W. Roderick N.F. Turchi P.J. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(5):522-528
Experiments to form and accelerate compact toroid (CT) plasmas have been performed on the 0.4-MJ Shiva Star fast capacitor bank at Phillips Laboratory. Theoretical investigations of employing a CT as a very fast opening switch are reported. A particular axisymmetric, geometrically complex switch design is studied with the help of 2-1/2-dimensional magnetohydrodynamic computer simulations. This design, called a magnetically-confined-plasma opening switch (McPOS), accumulates magnetic energy in an inductive store. Because of its intrinsic stability, the switch can conduct current for ten or more microseconds and can open in less than 100 ns-substantially less than the risetime of the capacitively produced electric current. A long conduction time compact torus plasma opening switch 相似文献
4.
Degnan AJ Young VE Tang TY Gill AB Graves MJ Gillard JH Patterson AJ 《Magnetic resonance imaging》2012,30(7):1017-1021
Purpose
Previous studies reporting relaxation times within atherosclerotic plaque have typically used dedicated small-bore high-field systems and small sample sizes. This study reports quantitative T1, T2 and T2? relaxation times within plaque tissue at 1.5 T using spatially co-matched histology to determine tissue constituents.Methods
Ten carotid endarterectomy specimens were removed from patients with advanced atherosclerosis. Imaging was performed on a 1.5-T whole-body scanner using a custom built 10-mm diameter receive-only solenoid coil. A protocol was defined to allow subsequent computation of T1, T2 and T2? relaxation times using multi-flip angle spoiled gradient echo, multi-echo fast spin echo and multi-echo gradient echo sequences, respectively. The specimens were subsequently processed for histology and individually sectioned into 2-mm blocks to allow subsequent co-registration. Each imaging sequence was imported into in-house software and displayed alongside the digitized histology sections. Regions of interest were defined to demarcate fibrous cap, connective tissue and lipid/necrotic core at matched slice-locations. Relaxation times were calculated using Levenberg-Marquardt's least squares curve fitting algorithm. A linear-mixed effect model was applied to account for multiple measurements from the same patient and establish if there was a statistically significant difference between the plaque tissue constituents.Results
T2 and T2? relaxation times were statistically different between all plaque tissues (P=.026 and P=.002 respectively) [T2: lipid/necrotic core was lower 47±13.7 ms than connective tissue (67±22.5 ms) and fibrous cap (60±13.2 ms); T2?: fibrous cap was higher (48±15.5ms) than connective tissue (19±10.6 ms) and lipid/necrotic core (24±8.2 ms)]. T1 relaxation times were not significantly different (P=.287) [T1: Fibrous cap: 933±271.9 ms; connective tissue (1002±272.9 ms) and lipid/necrotic core (1044±304.0 ms)]. We were unable to demarcate hemorrhage and calcium following histology processing.Conclusions
This study demonstrates that there is a significant difference between qT2 and qT2? in plaque tissues types. Derivation of quantitative relaxation times shows promise for determining plaque tissue constituents. 相似文献5.
Electromagnetic implosion of spherical liner 总被引:1,自引:0,他引:1
6.
The present article reviews the fundamental physical principles essential to an understanding of waveguide gas and liquid
lasers, and the current technological state of these devices. At the present time, waveguide laser transitions span the visible
through submillimeter regions of the wavelength spectrum. The introduction discusses the many applications of waveguide lasers
and the wide variety of laser configurations that are possible. Section 1 summarizes the properties of modes in hollow dielectric
waveguides of circular, rectangular, and planar cross section. Section 2 considers various approaches to optical feedback
including internal and external mirror Fabry-Perot type resonators, hollow waveguide distributed feedback structures, and
ring-resonant configurations. Section 3 discusses those aspects of molecular kinetic and laser theory pertinent to the design
and optimization of waveguide gas lasers such as the scaling laws for discharge-excited gas lasers, molecular models useful
in maximizing the oscillation bandwidth, the effects of gas flow rate, and the physics of optically-pumped far-infrared lasers.
Finally, a review of the waveguide gas and liquid lasers reported to date is given in Section 4. 相似文献
7.
8.
Degnan J.H. Kiuttu G.F. Turchi P.J. Graham J.D. Goforth J.H. Lopez E.A. Oona H. Tasker D.G. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(5):1437-1443
Explosive formed fuses (EFFs) use conducting elements that are deformed by explosive pressure (typically, against dielectric dies). This causes the fuse geometry to change, so that the conducting element cross section decreases. This enables a higher ratio of current conduction to current interrupt time than for normal fuses, and it enables more control of when current interruption occurs. In combination with a suitable output closing switch, EFF's can be used to obtain several hundred kilovolt voltage pulses from inductive stores to drive several ohm loads. With proper choices of inductive store, EFF geometry and material, and output closing switch features, such a voltage pulse can be approximately flat topped for microsecond duration and have a small fraction of microsecond risetime. We present theoretical analysis and circuit simulations which illustrate this, using scaled empirical EFF parameters for inductive stores in the 1 weber flux, several hundred nanohenry range. The circuit simulations were done using MicroCap-IV, with user defined elements. These simulations were done with static inductive stores and with explosive magnetic flux compression generators driving inductive stores 相似文献
9.
Degnan J.H. Taccetti J.M. Cavazos T. Clark D. Coffey S.K. Faehl R.J. Frese M.H. Fulton D. Gueits J.C. Gale D. Hussey T.W. Intrator T.P. Kirkpatrick R.C. Kiuttu G.H. Lehr F.M. Letterio J.D. Lindemuth I. McCullough W.F. Moses R. Peterkin R.E. Jr. Reinovsky R.E. Roderick N.F. Ruden E.L. Shlachter J.S. Schoenberg K.F. Siemon R.E. Sommars W. Turchi P.J. Wurden G.A. Wysocki F. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2001,29(1):93-98
The design and first successful demonstration of an imploding solid liner with height to diameter ratio, radial convergence, and uniformity suitable for compressing a field reversed configuration is discussed. Radiographs indicated a very symmetric implosion with no instability growth, with ~13x radial compression of the inner liner surface prior to impacting a central measurement unit. The implosion kinetic energy was 1.5 megajoules, 34% of the capacitor stored energy of 4.4 megajoules 相似文献
10.
Smith AB Adams CM Lodise Barbosa SA Degnan AP 《Journal of the American Chemical Society》2003,125(2):350-351
In this communication we describe the first total synthesis of (+)-13-deoxytedanolide, an architecturally complex marine macrolide possessing significant antitumor activity. The cornerstone of the synthesis comprises a highly convergent dithiane coupling used to construct the carbon skeleton, followed by a novel use of the Evans-Tishchenko reduction to oxidize the C(1) aldehyde to an ester in the presence of the oxidatively labile dithiane. 相似文献