132,208 research outputs found
Adamantylidene revisited: flash photolysis of adamantanediazirine
No full textIrradiation of 2-adamantane-2,3'-[3H]-diazirine (1) in isooctane at room temperature gives two primary photoproducts, 2-diazoadamantane and 2-adamantylidene (Ad:), with quantum yields of about 0.5 each. The fluorescence quantum yield of 1 is small, phi(f) approximate to 10(-4). The reactivity of Ad: was studied by nanosecond laser flash photolysis; it is best described as that of a carbene equilibrating between the singlet ground state and a low-lying triplet state. Ad: reacts with the precursor diazirine 1, pyridine, acetonitrile, tetramethylethylene, amines, water, and acetic acid with rate constants approaching the diffusion-controlled limit, as well as with molecular oxygen (k(O2) = 2.3 x 10(9) M-1 s(-t)). Reaction of Ad: with 1 (k(X) = 3.6 x 10(9) M-1 s(-1)) gives an ylide, lambda(max) = 290 nm, which forms adamantanone azine as a stable product by a reaction having activation parameters E-a = 15.5 kcal mol(-1) and A = 2 x 10(12) s(-t). At low concentrations of 1 in thoroughly dry, degassed solvents, the lifetime of Ad: reaches ca. 225 ns in isooctane, 500 ns in perfluorodecalin, and 700 ns in benzene. Diazoadamantane forms azine by a second-order reaction with a half-life of several hours at 10(-4) concentration. (C) 1998 Elsevier Science S.A. All rights reserved.PT: J; CR: BALLY T, 1994, ANGEW CHEM INT EDIT, V33, P1964 BATTINO R, 1983, J PHYS CHEM REF DATA, V12, P163 BERLMAN IB, 1971, HDB FLUORESCENCE SPE BETHELL D, 1966, J CHEM SOC B, P778 BETHELL D, 1969, J CHEM SOC B, P749 BONNEAU R, 1989, J AM CHEM SOC, V111, P5973 BONNEAU R, 1991, J AM CHEM SOC, V113, P9872 BONNEAU R, 1994, J AM CHEM SOC, V116, P3145 BONNEAU R, 1996, J AM CHEM SOC, V118, P7229 BONNEAU R, 1997, PURE APPL CHEM, V69, P979 BRINKER UH, 1993, ANGEW CHEM INT EDIT, V32, P1344 BUTERBAUGH JS, 1997, J AM CHEM SOC, V119, P3580 DIX EJ, 1993, J AM CHEM SOC, V115, P10424 GAUGLITZ G, 1984, Z PHYS CHEM NEUE FOL, V139, P237 GAUGLITZ G, 1985, J PHOTOCHEM, V30, P121 GE CS, 1994, J CHEM SOC CHEM COMM, P1479 GRILLER D, 1984, J AM CHEM SOC, V106, P2227 HELLER HG, 1981, J CHEM SOC P2, V2, P341 HO GJ, 1989, J AM CHEM SOC, V111, P6875 ISAEV SD, 1973, ZH ORG KHIM+, V9, P724 KUPFER R, 1994, J AM CHEM SOC, V116, P7393 LAVILLA JA, 1989, J AM CHEM SOC, V111, P6877 LIU MTH, 1977, TETRAHEDRON LETT, P3139 LIU MTH, 1989, J AM CHEM SOC, V111, P6873 LIU MTH, 1990, J CHEM SOC CHEM COMM, P1482 LIU MTH, 1994, J PHOTOCH PHOTOBIO A, V84, P133 MODARELLI DA, 1992, J AM CHEM SOC, V114, P7034 MORGAN S, 1991, J AM CHEM SOC, V113, P2782 MOSS RA, 1981, TETRAHEDRON LETT, V22, P3749 MOSS RA, 1990, J AM CHEM SOC, V112, P1638 MOSS RA, 1990, J AM CHEM SOC, V112, P5642 MOSS RA, 1997, CHEM COMMUN 0321, P617 OVERBERGER CG, 1964, J ORG CHEM, V29, P1188 PADWA A, 1991, CHEM REV, V91, P263 PARKER CA, 1968, PHOTOLUMINESCENCE SO PERSY G, 1987, EPA NEWSLETTER, V29, P45 SCAIANO JC, 1989, J ORG CHEM, V54, P1612 SHUSTOV GV, IN RPESS TOSCANO JP, 1994, J AM CHEM SOC, V116, P8146 UHLMANN E, 1996, J PHOTOCH PHOTOBIO A, V98, P45 WERSTIUK NH, 1984, CAN J CHEM, V62, P2391 YATES P, 1962, TETRAHEDRON, V18, P881; NR: 42; TC: 11; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 11; GA: 108KVSource type: Electronic(1
1, 2-H shift in benzylchlorocarbene: isotope effect and influence of the solvent
No full textLaser flash photolysis of 3-chloro-3-benzyldiazirine and 3-chloro-3-(phenyldideuteriomethyl)diazirine in isooctane over the 60 to -80-degrees-C temperature range gives rise to curved Arrhenius plots for both 1,2-H and 1,2-D migration in benzylchlorcarbene. The k(H)/k(D) values increase smoothly from 0.87 to 2.62 when the temperature increases from -60 to +30-degrees-C. The k(H)/k(D) value is approximately 4 for most of the temperatures studied if a solvent correction is applied. Quantum mechanical tunnelling or the influence of the solvent may be a possible explanation for these observations.PT: J; CR: BONNEAU R, 1989, J AM CHEM SOC, V111, P5973 BONNEAU R, 1992, J PHOTOCH PHOTOBIO A, V68, P97 DIX EJ, 1993, J AM CHEM SOC, V115, P10424 EVANSECK JD, 1990, J PHYS CHEM-US, V94, P5518 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 JACKSON JE, 1994, ADV CARBENE CHEM JONES M, 1980, REACTIVE INTERMEDIAT, V2 KIRMSE W, 1971, CARBENE CHEM LIU MTH, 1984, TETRAHEDRON, V40, P887 LIU MTH, 1990, J AM CHEM SOC, V112, P3915 LIU MTH, 1992, J PHOTOCH PHOTOBIO A, V63, P115 LIU MTH, 1992, J PHYS ORG CHEM, V15, P285 LIU MTH, 1994, RES CHEM INTERMEDIAT, V20, P195 MODARELLI DA, 1992, J AM CHEM SOC, V114, P7034 MOSS RA, 1992, TETRAHEDRON LETT, V33, P4287 MOSS RA, 1994, ADV CARBENE CHEM MUROV SL, 1973, HDB PHOTOCHEMISTRY NICKON A, 1993, ACCOUNTS CHEM RES, V26, P84 SALIS GA, 1968, J PHYS CHEM-US, V72, P752 SANDER W, 1994, UNPUB SCHAEFER HF, 1979, ACCOUNTS CHEM RES, V12, P288 SCHOLLER WW, 1989, HOUBEN WEYL METHODEN, P41 SHIMANOUCHI T, 1972, TABLES MOL VIBRATION, V1 SUGIYAMA MH, 1992, J AM CHEM SOC, V114, P966 WIERLACHER S, 1993, J AM CHEM SOC, V115, P8943; NR: 25; TC: 20; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 5; GA: PV021Source type: Electronic(1
Stellenregister zu Bonneau, Le régime administratif de l'eau du Nil
No full textMit dem hier vorgelegten Stellenregister wird die Nutzbarkeit eines der Standardwerke zum ägyptischen Bewässerungswesen (D. Bonneau: Le Régime administratif de l'eau du Nil dans l'Égypte Grecque, Romaine et Byzantine) verbessert
Laser flash photolysis studies of nitrogen ylides generated by the reaction of arylchlorocarbenes with substituted vinylpyridines and 1-azabuta-1,3-dienes
No full textLaser Flash Photolysis of arylchlorodiazirines in isooctane/CH2Cl2 in the presence of substituted vinylpyridines yields substituted vinylpyridinium ylide (lambda = 540 nm). As the ylide decays a concomitant growth causes an absorption at 330 nm, attributed to the formation of substituted indolizine. The reaction experiences the intramolecular 1,5-cyclization of the ylide intermediate. The kinetic parameters for the ylide formation and the 1,5-cyclization have been obtained. The activation energy for the latter process is reduced by 3-4 kcal mol(-1) when the vinylpyridine has a phenyl ring as a substituent in beta-position of the ethylenic group. Laser Flash Photolysis of phenylchlorodiazirine in isooctane in the presence of 1-azabuta-1,3-diene yields azomethine ylide (lambda = 550 nm) as an intermediate. The kinetic parameters for the ylide formations and further intramolecular 1,5-cyclization to pyrrole have been determined. The results resemble those obtained for the 1,5-cyclization of vinylpyridinium ylide. (C) 1999 Elsevier Science S.A. All rights reserved.PT: J; CR: BONNEAU R, 1989, J CHEM SOC P1, P1547 BONNEAU R, 1994, J CHEM SOC CHEM COMM, P509 BRAGG DR, 1962, J CHEM SOC, P2627 DANKS TN, 1994, TETRAHEDRON LETT, V35, P9443 DOYLE MP, 1998, CHEM REV, V98, P911 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 JACKSON JE, 1988, J AM CHEM SOC, V110, P510 KHLEBNIKOV AF, 1993, RUSS CHEM B, V42, P653 KOSTIKOV RR, 1977, ZH ORG KHIM, V13, P1857 KOSTIKOV RR, 1993, J PHYS ORG CHEM, V6, P83 LIU MTH, 1994, INT J CHEM KINET, V26, P1179 MAIBORODA DA, 1997, J ORG CHEM, V62, P7100 PADWA A, 1991, CHEM REV, V91, P263 PADWA A, 1996, CHEM REV, V96, P223 RAMAIAH D, 1992, J ORG CHEM, V57, P6032 SAITO I, 1976, TETRAHEDRON LETT, P2459 SEYFERTH D, 1973, J AM CHEM SOC, V95, P8464 SEYFERTH D, 1974, J ORG CHEM, V39, P2336 SHAW BD, 1933, J CHEM SOC, P77 TROST BM, 1980, J ORG CHEM, V45, P2741 VEDEJS E, 1988, J AM CHEM SOC, V110, P3238; NR: 21; TC: 6; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 6; GA: 238DZSource type: Electronic(1
Kinetics of intramolecular and intermolecular reactions of benzylchlorocarbene
No full textPhotolysis of 3-chloro-3-benzyldiazirine in tetramethylethylene gives E- and Z-beta-chlorostyrenes and cyclopropane. Relative rate studies show that the styrenes to cyclopropane ratio increases with increasing diazirine concentration. This permits the determination of the ratio k(D)/k(i) = 8 where k(D) is the rate constant for the reaction of carbene with diazirine and k(i) is the rate constant for the 1,2-hydrogen atom shift of carbene. Laser flash photolysis yields the first absolute rate constant for the reaction of a chlorocarbene with diazirine and a value of 7.7 for k(D)/k(i).PT: J; CR: BONNEAU R, 1989, J AM CHEM SOC, V111, P1973 JACKSON JE, 1988, J AM CHEM SOC, V110, P5595 JACKSON JE, 1989, J AM CHEM SOC, V111, P6874 LIU MTH, 1985, J CHEM SOC CHEM COMM, P982 LIU MTH, 1989, J AM CHEM SOC, V111, P6873 LIU MTH, 1990, J AM CHEM SOC, V112, P3915 MORGAN S, 1991, J AM CHEM SOC, V113, P2782 MOSS RA, 1990, J AM CHEM SOC, V112, P1638 MOSS RA, 1990, J AM CHEM SOC, V112, P5642 MOSS RA, 1990, TETRAHEDRON LETT, V31, P1225 WARNER PM, 1984, TETRAHEDRON LETT, V25, P4211; NR: 11; TC: 11; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 4; GA: HD116Source type: Electronic(1
STUDYING THE EFFECTS OF MOBILIZATION MESSAGES IN A STRATEGIC ENVIRONMENT: APPLYING THE RECEIVE-ACCEPT-SAMPLE (RAS) MODEL
No full textThe study of mobilization has presented scholars with an interesting puzzle as we attempt to identify who is responsive to mobilization messages. The framing of the debate by Kenneth M. Goldstein and Matthew Holleque (2010) pits competing theoretical arguments against one another without a satisfying conclusion. Some argue it is the least informed segments of the population who will be responsive (e.g., Rosenstone and Hansen 1993), while others posit it is those with high levels of political information and past involvement (e.g., Hillygus 2005). In this dissertation I present a third explanation that may provide a better framework for studying the debate. Applying John Zaller’s Receive-Accept-Sample (RAS) model to the study of mobilization, I find not only do individuals with moderate levels of past voting behavior respond to mobilization messages, but so do those with high and low levels. The key to the RAS model is exposure to the message. Thus understanding who is most likely to receive a mobilization message is central to this project.
I conducted field experiments during a magisterial judicial election in a major U.S. city to collect my data. The purpose of those experiments was to capture the effects of mobilization messages on an individual’s probability of voting on Election Day. My results indicate including individuals who would normally not receive mobilization messages (i.e., those who do not have a history of voting) introduce selection bias. Once I control for that bias, I find not only are individuals with moderate levels of past voting behavior responsive, but so are those with high and low levels of past turnout. Receiving a get-out-the-vote door hanger two days prior to an election increases the probability of voting by 3.76% for moderate voters, 3.82% for frequent voters, and 2.88% for infrequent voters.
The effects of mobilization messages are not limited to turnout. Perhaps more important than turnout, I found that a candidate who conducts a last minute GOTV drive can increase their vote share by as much as 25%. This dissertation breaks new ground on the effects of mobilization messages and contributes to a clearer picture of those effects
Spectroscopic, kinetic, and structural properties of rotamers of the 2-vinylpyridinium ylide of phenylchlorocarbene
No full textThe analysis of the time-resolved UV-vis absorption spectra of the 2-vinylpyridinium ylide of phenylchlorocarbene, measured by laser-flash photolysis, indicates the existence of two rotamers of this species. The absorption spectrum, rise time, and decay time of each rotamer were determined by a global analysis method. The kinetic analysis of the results indicates an interconversion between the rotamers and a large difference between their rates of cyclization. The observed rotamerism involves a rotation of the vinyl pyridine with respect to the carbene, the two rotamers being differentiated by the fact that the vinyl group faces either the chlorine or the phenyl groups of the carbene. Calculations of the absorption spectra and enthalpies of formation of numerous possible structures indicate that the 100-nm difference between the wavelengths of maximum absorption is well explained by a change in the tilt angle between the phenyl and the yfide planes from 35-40degrees for the "red-absorbing" ylide to 55-60degrees for the other. However, the calculated enthalpies of formation of the various structures being nearly the same, these calculations do not allow us to assign one specific structure to one or the other of the observed species.PT: J; CR: *OXF MOL LTD, 1999, MOPAC AMI PM3 *SEM INC, 2003, AMPAC 7 2 BELIN C, 2001, J PHOTOCH PHOTOBIO A, V139, P111 BONNEAU R, 2003, J PHOTOCH PHOTOBIO A, V161, P43 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 JACKSON JE, 1988, J AM CHEM SOC, V110, P5595 LIU MTH, 1994, INT J CHEM KINET, V26, P1179 MALINOWSKI ER, 1991, FACTOR ANAL CHEM MAZZUCATO U, 1991, CHEM REV, V91, P1679 NAITO I, 2001, J PHOTOCH PHOTOBIO A, V140, P33 OKI M, 1981, CHEM LETT, P649 OKI M, 1988, B CHEM SOC JPN, V61, P4303 TAKEDA N, 1997, CHEM-EUR J, V3, P62; NR: 13; TC: 3; J9: J PHYS CHEM A; PG: 7; GA: 774AMSource type: Electronic(1
Photolysis of m-phenylene-bis(Chlorodiazirine)+2-vinylpyridine: does an indolizine chromophore inhibit the photolysis of a diazirine?
No full textThe photolysis of m-phenylene-bis(chlorodiazirine) in the presence of 2-vinylpyridine (VP) yields the m-phenylene-bis(indolizine) by a mechanism involving two consecutive photoreactions. Photolysis of a first diazirine ring generates a carbene which reacts with 2-VP to give, via a sequence of fast thermal reactions, a first product including both the indolizine and the chlorodiazirine moieties. Although in the lowest excited singlet state of the primary product, the excitation is localized on the indolizine unit, the photolysis of this product induces the decomposition of the second diazirine ring to give a second carbene which yields the final product via the same sequence of reactions: formation of a 2-vinylpyridinium ylide, cyclization and elimination of HCl. Analysis of the absorption and fluorescence spectra indicates that an upper excited singlet state, with the excitation localized on the diazirine ring, is only a few kJ/mol above S-1. It can therefore be populated by thermal activation of S-1 so that there is, seemingly, an endothermic intramolecular energy transfer from the indolizine moiety to the diazirine ring. (C) 2003 Elsevier B.V. All rights reserved.PT: J; CR: BATTINO R, 1983, J PHYS CHEM REF DATA, V12, P163 BONNEAU R, UNPUB J PHYS CHEM DESVERGNE JP, 2003, PHOTOCH PHOTOBIO SCI, V2, P289 GOULD IR, 1985, TETRAHEDRON, V41, P1987 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 LERNER DA, 1977, J PHYS CHEM-US, V81, P12 LIU MTH, 1994, INT J CHEM KINET, V26, P1179 LIU MTH, 2001, 9 KYUSH INT S PHYS O MUROV SL, 1973, HDB PHOTOCHEMISTRY, P56 TOMIOKA H, 1993, CHEM LETT, P1291 VELAPOLDI RA, 1980, 26064 NAT BUR STAND ZUEV P, 1993, J AM CHEM SOC, V115, P3788 ZUEV PS, 1994, J ORG CHEM, V59, P2267; NR: 13; TC: 1; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 8; GA: 741YRSource type: Electronic(1
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Validation data for the quantification of the Annonaceous acetogenin annonacin in Rat brain by UPLC-MS/MS
No full textAbstractAnnonaceous acetogenins (AAGs) are environmental neurotoxins from the fruit pulp of several Annonaceae species, whose consumption was linked to the occurrence of sporadic atypical Parkinsonism with dementia. The quantification of the prototypical AAG annonacin in Rat brain homogenates was performed by UPLC-MS/MS in selected reaction monitoring (SRM) mode, using a triple quadrupole mass analyzer. A natural analog of annonacin was used as an internal standard. Analyzed data set of the analytical validation of this method is presented, including stability of the samples, extraction recovery and matrix effect, supporting the results described in the article “Quantification of the environmental neurotoxin annonacin in Rat brain by UPLC-MS/MS” N. Bonneau, I. Schmitz-Afonso, D. Touboul, A. Brunelle, P. Champy (2016) [1]
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