36,473 research outputs found
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-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
Catalytic P-H activation by Ti and Zr catalysts
No full textCatalytic dehydrocoupling of phosphines was investigated using the anionic zirconocene trihydride salts [Cp*Zr-2(mu-H)(3)Li](3) (1a) or [Cp*Zr-2(mu-H)(3)K(thf)(4)] (1b), and the metallocycles [CpTi(NPtBu3)(CH2)(4)] (6) and [Cp*M(NPtBu3)(CH2)(4)] (M = Ti 20, Zr 21) as catalyst precursors. Dehydrocoupling of primary phosphines RPH2 (R = Ph, C6H2Me3, Cy, C10H7) gave both dehydrocoupled dimers RP(H)P(H)R or cyclic oligophosphines (RP)(n) (n = 4, 5) while reaction of tBu(3)C(6)H(2)PH(2) gave the phosphaindoline tBu(2)(Me2CCH2)C6H2PH (9). Stoichiometric reactions of these catalyst precursors with primary phosphines afforded [Cp*Zr-2((PR)(2))H][K(thf)(4)] (R = Ph 2, Cy 3, C6H2Me3 4), [Cp*Zr-2((PPh)(3))H] [K(thf)(4)] (5), [CpTi(NPtBu3)(PPh)(3)] (7) and [CpTi(NPtBu3)(mu-PHPh)](2) (8), while reaction of 6 with (C(6)H(2)tBu3)PH2 in the presence of PMe3 afforded [CpTi(NPtBu3)(PMe3)(p(C(6)H(2)tBu(3))] (10). The secondary phosphines Ph2PH and (PhHPCH2)(2)CH2 also undergo dehydrocoupling affording (Ph2P)(2) and (PhPCH2)(2)CH2. The bisphosphines (CH2PH2)(2) and C6H4(PH2)(2) are dehydrocoupled to give (PCH2CH2PH)(2) (12) and (C6H4P(PH))(2) (13) while prolonged reaction of 13 gave (C6H4P2)(8) (14). The analogous bisphosphine Me2C6H4(PH)(2) (17) was prepared and dehydrocoupling catalysis afforded (Me2C6H2P(PH))(2) (18) and subsequently [(Me2C6H2P2)(2)(mu-Me2C6H2P2)](2) (19). Stoichiometric reactions with these bisphosphines gave [Cp*Zr-2(H)(PH)(2)C6H4] [Li(thf)(4)] (22), [Cp*Ti(NPtBu3)(PH)(2)C6H4](2) (23) and [Cp*Ti(NPtBu3)(PH)(2)C6H4] (24). Mechanistic implications are discussed.PT: J; CR: ALBRAND JP, 1976, J CHEM SOC CHEM COMM, P876 ANSELME JP, 1969, TETRAHEDRON, V25, P855 BASULI F, 2003, J AM CHEM SOC, V125, P10170 BAUDLER M, 1976, Z NATURFORSCH B, V31, P558 BAUDLER M, 1978, CHEM BER, V111, P1210 BAUDLER M, 1978, CHEM BER, V111, P1217 BAUDLER M, 1983, CHEM BER, V116, P2711 BAUDLER M, 1984, Z NATURFORSCH B, V39, P438 BAZAN GC, 1991, J AM CHEM SOC, V113, P6899 BOHM VPW, 2001, ANGEW CHEM, V113, P4832 CHAUVIN Y, 1971, MAKROMOL CHEM, V141, P161 COREY JY, 2004, ADV ORGANOMET CHEM, V51, P1 COURET C, 1986, ORGANOMETALLICS, V5, P113 COWLEY AH, 1984, TETRAHEDRON LETT, V25, P2125 COWLEY AH, 1990, INORG SYNTH, V27, P235 CROMER DT, 1974, INT TABLES CRYSTALLO, V4, P71 ETKIN N, 1997, J AM CHEM SOC, V119, P11420 ETKIN N, 1997, J AM CHEM SOC, V119, P2954 ETKIN N, 1997, ORGANOMETALLICS, V16, P3504 FEHLNER TP, 1992, INORGANOMETALLLICS FERMIN MC, 1995, J AM CHEM SOC, V117, P12645 FERMIN MC, 1995, ORGANOMETALLICS, V14, P4247 FU GC, 1993, J AM CHEM SOC, V115, P9856 GAUVIN F, 1998, ADV ORGANOMET CHEM, V42, P363 GRAHAM TW, 2004, ORGANOMETALLICS, V23, P3309 GRUBBS RH, 1972, J AM CHEM SOC, V94, P2538 GRUBBS RH, 2003, HDB METATHESIS HEY E, 1988, CHEM BER, V121, P561 HEY E, 1989, J ORGANOMET CHEM, V378, P375 HO JW, 1991, ORGANOMETALLICS, V10, P3001 HO JW, 1994, INORG CHEM, V33, P865 HOFFMAN PR, 1975, INORG CHEM, V14, P1997 HOSKIN AJ, 2001, ANGEW CHEM, V113, P1917 HOU ZM, 1993, ORGANOMETALLICS, V12, P3158 INAGAKI Y, 1980, B CHEM SOC JPN, V53, P205 ISSLEIB K, 1972, ANGEW CHEM, V84, P582 ISSLEIB K, 1987, J ORGANOMET CHEM, V330, P17 JACOBSEN EN, 1988, J AM CHEM SOC, V110, P1968 KATSUKI T, 1980, J AM CHEM SOC, V102, P5974 KAUFFMANN T, 1984, TETRAHEDRON LETT, V25, P1963 KAUFFMANN T, 1985, CHEM BER, V118, P1022 KITAMURA M, 1988, J AM CHEM SOC, V110, P629 KNOWLES WS, 1983, ACCOUNTS CHEM RES, V16, P106 KOEPF H, 1981, CHEM BER, V114, P2731 KOHLER EP, 1935, J AM CHEM SOC, V57, P367 KYBA EP, 1983, ORGANOMETALLICS, V2, P1877 MILLER AR, 1976, J AM CHEM SOC, V98, P1860 MILLER SJ, 1996, J AM CHEM SOC, V118, P9606 MIYASHITA A, 1980, J AM CHEM SOC, V102, P7932 MURDZEK JS, 1987, ORGANOMETALLICS, V6, P1373 NGUYEN ST, 1992, J AM CHEM SOC, V114, P3974 NGUYEN ST, 1993, J AM CHEM SOC, V115, P9858 NOVAK BM, 1988, J AM CHEM SOC, V110, P960 OHKUMA T, 1995, J AM CHEM SOC, V117, P2675 OHTA T, 1988, INORG CHEM, V27, P566 OSHIKAWA T, 1985, CHEM IND-LONDON, P126 ROCKLAGE SM, 1981, J AM CHEM SOC, V103, P1440 SCHOLL M, 1999, TETRAHEDRON LETT, V40, P2247 SCHROCK RR, 1974, J AM CHEM SOC, V96, P6796 SCHROCK RR, 1980, J MOL CATAL, V8, P73 SCHROCK RR, 1988, J MOL CATAL, V46, P243 SCHROCK RR, 1990, J AM CHEM SOC, V112, P3875 SCHWAB P, 1995, ANGEW CHEM INT EDIT, V34, P2039 SCHWAB P, 1995, ANGEW CHEM, V107, P2179 SCHWAB P, 1996, J AM CHEM SOC, V118, P100 SENDERIKHIN AI, 1988, ZH OBSHCH KHIM+, V58, P1662 SENDERIKHIN AI, 1989, ZH OBSHCH KHIM+, V59, P2141 SEYFERTH D, 1969, J ORG CHEM, V34, P1483 SHELDRICK GM, 2000, SHELXTL SHU RH, 1998, J AM CHEM SOC, V120, P12988 SMIT CN, 1983, TETRAHEDRON LETT, V24, P2031 SOUFFLET JP, 1973, CR ACAD SCI C CHIM, V276, P169 STEPHAN DW, 2000, ANGEW CHEM, V112, P322 STEPHAN DW, 2005, ORGANOMETALLICS, V24, P2548 STRADIOTTO M, 2001, HELV CHIM ACTA, V84, P2958 TILLEY TD, 1990, COMMENTS INORG CHEM, V10, P37 TILLEY TD, 1993, ACCOUNTS CHEM RES, V26, P22 TVERDOMED SN, 2003, RUSS J GEN CHEM+, V73, P319 VANDENWINKEL Y, 1991, J ORGANOMET CHEM, V405, P183 WATERMAN R, 2006, ANGEW CHEM INT EDIT, V45, P2926 WATERMAN R, 2006, ANGEW CHEM, V118, P2992 WEAST RC, 1974, HDB CHEM PHYS, P2436 WOOD CD, 1979, J AM CHEM SOC, V101, P3210 WU Z, 1995, J AM CHEM SOC, V117, P5503 XIN SX, 1997, J AM CHEM SOC, V119, P5307; NR: 85; TC: 0; J9: CHEM-EUR J; PG: 12; GA: 113PJSource type: Electronic(1
Measuring industry-science links through inventor-author relations: A profiling method
No full textIn this pilot study we examine the performance of text-based profiling in recovering a set of validated inventor-author links. In a first step we match patents and publications solely based on their similarity in content. Next, we compare inventor and author names on the highest ranked matches for the occurrence of name matches. Finally, we compare these candidate matches with the names listed in a validated set of inventor-author names. Our text-based profile methodology performs significantly better than a random matching of patents and publications, suggesting that text-based profiling is a valuable complementary tool to the name searches used in previous studies.innovation; industry-science links; text-based profiling;
Letter from John H. Page to Carl Hayden
No full textLetter from John H. Page to Carl T. Hayden regarding his company's rights to build a railway if they choose to
Insertion of phenylchlorocarbenes in the C-H bonds of alkanes: measurement of the rate constants by laser flash photolysis
No full textPhenylchlorocarbenes, produced by photolysis of the parent diazirines, have a very limited lifetime in alkane solvents. The rate of disappearance of p-methyl- and p-chlorophenylchlorocarbenes has been measured in iso-octane, cyclohexane and n-hexane as well as in benzene for comparison. The rate constants of several processes (dimerization, addition to the diazirine, reaction with the solvent, etc. ) contributing to the disappearance of the phenylchlorocarbenes have been determined. The rate of reaction with the solvent, which is much lower in benzene than in alkanes and depends strongly on the nature of the alkane, is assumed to be an insertion of the carbene in the C-H bonds of the solvent. Consequences of this reaction on the chemistry of carbenes produced by continuous irradiation (or thermolysis) of diazirines in alkanes are briefly discussed.PT: J; CR: BENSASSON R, 1971, T FARADAY SOC, V67, P1904 BONNEAU R, 1986, NOUV J CHIM, V10, P425 BONNEAU R, 1991, PURE APPL CHEM, V63, P289 DOYLE MP, 1988, TETRAHEDRON LETT, V29, P5863 GOULD IR, 1985, TETRAHEDRON, V41, P1587 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 LIU MTH, 1987, CHEM DIAZIRINES LIU MTH, 1990, J CHEM SOC CHEM COMM, P1482 LIU MTH, 1992, J AM CHEM SOC, V114, P3604 LIU MTH, 1992, J ORG CHEM, V57, P2483 LIU MTH, 1992, J PHOTOCH PHOTOBIO A, V63, P115 LUTZ H, 1973, J PHYS CHEM-US, V77, P1758 MORGAN S, 1991, J AM CHEM SOC, V113, P2782 MOSS RA, 1990, J AM CHEM SOC, V112, P5642 MOSS RA, 1990, KINETICS SPECTROSCOP; NR: 15; TC: 11; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 10; GA: JQ196Source type: Electronic(1
Origin of the stereoselectivity of the intramolecular 1,2-hydrogen shift in singlet chlorocarbenes. A theoretical study
No full textThe stereochemistry of 1,2-H migration in ethylchlorocarbene (1) and chloromethylchlorocarbene (2) has been studied by ab initio methods. Geometries of the ground and transition states of a conformational equilibrium and the 1,2 rearrangement were optimized at the DFT (B3LYP) and MP2 levels of theory using 6-31G(D) and 6-311+G(D,P) basis sets. Final energies were obtained at the MP4/6-311+G(D,P)//MP2/6-311+G(D,P) level. It has been shown that the equilibrium between cis- and trans-conformers of 1 and 2 is shifted moderately toward the trans-conformer for carbene 1 and strongly toward the cis-conformer in the case of 2. The calculated barriers of rotation about the CC bond in carbene 1 (Delta G double dagger = 2.3 kcal mol(-1)) and 2 (5.3 kcal mol(-1)) are lower than the smallest predicted barriers of the 1,2-H shift (8.0 and 8.5 kcal mol(-1), respectively). In accordance with the Curtin-Hammett principle, kinetic control of stereochemistry of the rearrangement proceeding classically is realized. The predicted preferable formation of the Z-isomer of 1-chloropropene (3) and 1,2-dichloroethylene (4) is in good agreement with the experimental data obtained under conditions of the high-temperature thermolysis of the corresponding diazirines. Electronic factors influencing the relative stability of the cis- and trans-isomers of carbenes 1 and 2 and their transition states for 1,2-H migration are discussed.PT: J; CR: ABELL PJ, 1969, J CHEM THERMODYN, V28, P333 BECKE AD, 1988, PHYS REV A, V38, P3098 BECKE AD, 1993, J CHEM PHYS, V98, P5648 BONNEAN Y, 1996, J AM CHEM SOC, V118, P3829 BONNEAU R, 1989, J AM CHEM SOC, V111, P5973 CRAIG NC, 1971, J PHYS CHEM-US, V75, P1453 CRUMP JW, 1963, J ORG CHEM, V28, P953 DIX EJ, 1993, J AM CHEM SOC, V115, P10424 DIX EJ, 1994, RES CHEM INTERMEDIAT, V20, P149 DIX EJ, 1994, THESIS U ROCHESTER N ELIEL EL, 1994, STEREOCHEMISTRY ORGA EPIOTIS ND, 1974, J AM CHEM SOC, V96, P4075 EVANSECK JD, 1990, J AM CHEM SOC, V112, P9148 EVANSECK JD, 1990, J PHYS CHEM-US, V94, P5518 FREY HM, 1970, J CHEM SOC A, P1916 FRISCH MJ, 1995, GAUSSIAN 94 REVISION JONES WM, 1980, REARRANGEMENT GROUND, P95 JORGENSEN WL, 1973, ORGANIC CHEM BOOK OR LAVILLA JA, 1989, J AM CHEM SOC, V111, P6877 LEE C, 1988, PHYS REV B, V37, P785 LIU MTH, 1974, CAN J CHEM, V52, P246 LIU MTH, 1989, J ORG CHEM, V54, P486 LIU MTH, 1990, J AM CHEM SOC, V112, P3915 LIU MTH, 1994, ACCOUNTS CHEM RES, V27, P287 MCQUARRIE DA, 1973, STATISTICAL THERMODY MOSS RA, 1994, ADV CARBENE CHEM, V1 NICKON A, 1993, ACCOUNTS CHEM RES, V26, P84 NICKON A, 1993, TETRAHEDRON LETT, V34, P1391 PITZER KS, 1954, J AM CHEM SOC, V76, P1493 PROCHAZKA M, 1980, COLLECT CZECH CHEM C, V45, P1388 ROSENBERG MG, 1996, TETRAHEDRON LETT, V37, P3235 SHIN SH, 1996, J AM CHEM SOC, V118, P7626 STORER JW, 1993, J AM CHEM SOC, V115, P10426 TOMIOKA H, 1980, J AM CHEM SOC, V102, P7818 TOMIOKA H, 1984, J CHEM SOC CHEM COMM, P476 TOMIOKA H, 1985, TETRAHEDRON LETT, P1651 TOMIOKA H, 1986, J CHEM SOC CHEM COMM, P693 VOSKO SH, 1980, CAN J PHYS, V58, P1200 WOOD RE, 1941, J AM CHEM SOC, V63, P1650 YAMAMOTO Y, 1970, TETRAHEDRON, V26, P1235 ZEFIROV NS, 1977, TETRAHEDRON, V33, P2719; NR: 41; TC: 17; J9: J PHYS CHEM A; PG: 5; GA: WQ630Source type: Electronic(1
Mesophilic-hydrothermal-thermophilic (M-H-T) digestion of green corn straw
No full textMesophilic-hydrothermal (80-160 degrees C, 30 min)-thermophilic (M-H-T) digestion and control tests of mesophilic (M), thermophilic (T), hydrothermal-mesophilic (H-M), and mesophilic-thermophilic digestion (M-T) of green corn straw were conducted for a 20-day fermentation period. The results indicate that M-H-T is an efficient method to improve methane production. A maximum methane yield of 371.74 mL/g volatile solid was obtained by the M (3 days)-H (140 degrees C)-T (17 days) process, which was 20.44%, 16.55%, 31.44%, and 14.31% higher than the yields of the M, T, 140-M, and M-T processes. The enhanced methane production was attributed to (1) the improved hemicellulose degradation and lignin disorganization; (2) prevention of the degradation of soluble sugar, easily hydrolyzed hemicellulose and cellulose into furfural and methylfurfural; and (3) lack of formation of Maillard reaction products during initial hydrothermal treatment. (C) 2015 Elsevier Ltd. All rights reserved
Time-resolved-absorption spectroscopic detection of 10,10-dimethyl-10-silaanthracen-9(10H)-one oxide
No full textPT: J; CR: ANDO W, 1981, J SYN ORG CHEM JPN, V39, P613 BARTLETT PD, 1962, J AM CHEM SOC, V84, P3408 HAYASHI H, 1980, B CHEM SOC JPN, V53, P1519 KANAMARU N, 1970, B CHEM SOC JPN, V43, P3443 MURRAY RW, 1971, J AM CHEM SOC, V93, P4963 SAWAKI Y, 1981, J AM CHEM SOC, V103, P3832 SEKIGUCHI A, 1982, TETRAHEDRON LETT, V23, P4095 STEWART R, 1963, CAN J CHEM, V41, P1065 SUGAWARA T, 1983, CHEM LETT TURRO NJ, 1980, IEEE J QUANTUM ELECT, V16, P1218; NR: 10; TC: 47; J9: CHEM LETT; PG: 2; GA: RB995Source type: Electronic(1
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