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21.
Barish B Chadha M Chan S Cowen DF Eigen G Miller JS O'Grady C Urheim J Weinstein AJ Acosta D Athanas M Masek G Paar HP Gronberg J Kutschke R Menary S Morrison RJ Nakanishi S Nelson HN Nelson TK Qiao C Richman JD Ryd A Tajima H Sperka D Witherell MS Procario M Balest R Cho K Daoudi M Ford WT Johnson DR Lingel K Lohner M Rankin P Smith JG Alexander JP Bebek C Berkelman K Bloom K Browder TE Cassel DG Cho HA Coffman DM Crowcroft DS Drell PS Ehrlich R Gaidarev P Galik RS Garcia-Sciveres M Geiser B 《Physical review D: Particles and fields》1995,51(3):1014-1033
22.
Battle M Ernst J Kwon Y Roberts S Thorndike EH Wang CH Dominick J Lambrecht M Sanghera S Shelkov V Skwarnicki T Stroynowski R Volobouev I Wei G Zadorozhny P Artuso M Goldberg M He D Horwitz N Kennett R Mountain R Moneti GC Muheim F Mukhin Y Playfer S Rozen Y Stone S Thulasidas M Vasseur G Zhu G Bartelt J Csorna SE Egyed Z Jain V Kinoshita K Edwards KW Ogg M Britton DI Hyatt ER MacFarlane DB Patel PM Akerib DS Barish B Chadha M Chan S Cowen DF Eigen G Miller JS O'Grady C Urheim J Weinstein AJ 《Physical review letters》1994,73(8):1079-1083
23.
24.
Photolysis of complexes of the type M(2)(CO)(6)(RC(5)H(4))(2) (where M = W, Mo, Cr and R = H (Cp) or CH(3) (Cp')) leads to the production of short lived 17-electron radicals. Direct electrochemical characterization of these intermediates has been achieved using a technique known as photomodulated voltammetry (PMV). The results from PMV analysis are in excellent agreement with literature estimates for CpMo(CO)(3)(*) and CpCr(CO)(3)(*). However, CpW(CO)(3)(*) is found to be shifted oxidatively 115 mV relative to previous literature estimates. The change in the value for the tungsten complex changes previous estimates to the bond dissociation energy for tungsten metal hydrides by 3.0 +/- 0.9 kcal/mol. Lifetime information on the radicals is also reported based on the phase shift of the electrochemical signal observed by PMV under limiting current conditions. 相似文献
25.
The pentacyclic marine alkaloids (-)-papuamine (1) and (-)-haliclonadiamine (2) have been prepared by total synthesis. The synthesis began with (-)-8, which was converted into diester 20 by way of bis-mesylate 17, dinitrile 18, and diacid 19. Dieckmann cyclization of 20 provided keto ester 21, which was transformed into acetal 22. After hydrolysis of the acetal, ketone 25 was subjected to reductive amination with 1,3-propanediamine and sodium triacetoxyborohydride to obtain diamines 26 and 27 as a 71:29 mixture of diastereomers, favoring the symmetrical isomer having the papuamine relative configuration. After transformation of the diamines to their t-Boc derivatives, the benzyl ethers were cleaved and the resulting diol was oxidized to dialdehyde 30. Application of the Seyferth procedure for conversion of aldehydes to alkynes gave a mixture of diynes 31 and 32. After removal of the t-Boc protecting groups from 31, diamino diyne 15 was treated with tributylstannane and azoisobutyronitrile to obtain the bis-vinylstannane 34. Treatment of this compound with Pd(II) and Cu(I) in the presence of air produced (-)-papuamine (1). (-)-Haliclonadiamine (2) was obtained from the unsymmetrical isomer, 32. The NMR spectra of the synthetic alkaloids were identical to those of authentic samples of the natural alkaloids. 相似文献
26.
Todd Kapitula Stanislaus Maier-Paape 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1996,47(2):265-305
We consider the dynamics of the Ginzburg-Landau equation in a small neighborhood of a known pulse solution by studying a Poincaré map,P:
T
T
, where
T
is a section which is transverse to the pulse. Due to the fact that the Ginzburg-Landau equation possesses both a rotational symmetry and a spatial symmetry, we are able to conduct a detailed analytical study of this map in neighborhoods arbitrarily close to the pulse solution. Thus, we are able to complement the work of Holmes [8], who conducted an analytical study of the Poincaré map in a punctured neighborhood of the pulse. We find that the Poincaré map contains an invariant set itT, where is not necessarily a Cantor set of points, such thatP: is homeomorphic to a shift map on (at least) two symbols. Furthermore, we find that for eachm 1 the mapP
itm possesses a fixed point. Since is not necessarily a Cantor set, this is not immediately clear. Finally, we find that when the pulse solution is broken, for eachm1 there exist parameter values such that pulses possessingm maxima appear.On leave at the University of Utah during 1993/94. Supported by the DFG, Habilitationsstipendium Ma 1587/1-1. 相似文献
27.
Two general methods for the preparation of β-silyl-substituted divinyl ketones have been developed starting from either α, β-unsaturated aldehydes or simple ketones. Anhydrous FeCl3 induces the cyclization to cyclopentenones under mild conditions and in good yields with predictable and complete control over the position of the double bond in the five-membered ring. The observed effects of substituents on rate can be explained by a rate-determining cationic electrocyclization. Silyl substitution has been shown to retard the reaction. 相似文献
28.
The thermally stable, terminal phosphinidene complexes [CpM(CO)2(eta1-PNiPr2)]AlCl4(Cp= Cp, Cp*; M = Fe) and [Cp*M(CO)3(eta1-PNiPr2)]AlCl4 (M = Cr, Mo, W) react with Ph2C=N=N to form terminal P-coordinated eta1-phosphaazine and eta3-diazaphosphaallene ligands, respectively, whereas [CpFe(CO)2(eta1-PNiPr2)]AlCl4 reacts with Me3SiCHN2 affording a terminal phosphorus bound eta1-phosphaalkene complex. 相似文献
29.
Springfield SA Marcantonio K Ceglia S Albaneze-Walker J Dormer PG Nelson TD Murry JA 《The Journal of organic chemistry》2003,68(11):4598-4599
In this paper, we disclose an efficient one-pot procedure for the preparation of substituted 1,8-naphthyridin-4-one analogues. Previous efforts to effect this type of transformation were complicated by the formation of benzene tricarboxylate. Via the use of excess base, the impurity formation was completely inhibited. This allowed for the clean preparation of the desired intermediate and subsequent formation of naphthyridone analogues in a single flask, which could then be crystallized directly from the reaction mixture in good yield and high purity. 相似文献
30.
Seghezzo L Trupiano AP Liberal V Todd PG Figueroa ME Gutiérrez MA Da Silva Wilches AC Iribarnegaray M Guerra RG Arena A Cuevas CM Zeeman G Lettinga G 《Applied biochemistry and biotechnology》2003,109(1-3):167-180
A pilot-scale sewage treatment system consisting of two upflow anaerobic sludge bed (UASB) reactors followed by five waste stabilization ponds (WSPs) in series was studied under subtropical conditions. The first UASB reactor started up in only 1 mo (stable operation, high chemical oxygen demand [COD] removal efficiency, low volatile fatty acids concentration in the effluent, alkalinity ratio above 0.7, biogas production above 0.1 Nm3/kg of CODremoved). Removal efficiencies up to 90% were obtained in the anaerobic steps at a hydraulic retention time of 6 + 4 h (80% removal in the first step). Fecal coliform removal in the whole system was 99.9999% (99.94% in anaerobic steps and 99.98% in WSPs). COD balances over UASB reactors are provided. A minimum set of data necessary to build COD balances is proposed. Intermittent sludge washout was detected in the reactors with the COD balances. Sludge washout from single-step UASB reactors should be monitored and minimized in order to ensure constant compliance with discharge standards, especially when no posttreatment is provided. The system combined high COD and fecal coliform removal efficiency with an extremely low effluent concentration, complying with discharge standards, and making it an attractive option for sewage treatment in subtropical regions. 相似文献