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81.
R. Albrecht T. C. Awes P. Beckmann F. Berger D. Bock R. Bock G. Claesson G. Clewing L. Dragon A. Eklund R. L. Ferguson A. Franz S. Garpman R. Glasow H. Å. Gustafsson H. H. Gutbrod G. Hölker J. Idh P. Jacobs K. H. Kampert B. W. Kolb P. Kristiansson H. Löhner I. Lund F. E. Obenshain A. Oskarsson I. Otterlund T. Peitzmann F. Plasil A. M. Poskanzer M. Purschke H. G. Ritter R. Santo S. Saini H. R. Schmidt S. P. Sørensen K. Steffens D. Stüken E. Stenlund M. Tincknell G. R. Young 《Zeitschrift fur Physik C Particles and Fields》1991,51(1):1-10
The production of direct photons has been investigated in reactions ofp and16O projectiles at 60 and 200A·GeV with C and Au nuclei. Photon and 0 spectra have been measured in the pseudorapidity range 1.52.1 for the transverse momentum region 0.4 GeV/cp
T
2.8 GeV/c employing the lead-glass spectrometer SAPHIR. An upper limit of 15% at the 90% confidence level for the direct photon signal relative to the neutral pion production is obtained from the comparison of measured photon spectra with Monte Carlo simulations of the hadronic background based on the reconstructed yield of 0 and mesons. Consequences for a possible phase transition to a quark-gluon plasma are discussed. 相似文献
82.
Jim Agler 《Integral Equations and Operator Theory》1982,5(1):608-631
We develop techniques which allow one to describe in simple terms the set of operators on Hilbert space of the form M* () |M, where M is multiplication by z on a Hilbert space of analytic functions satisfying certain technical assumptions, M* () is the direct sum of a countably infinite number of copies of M*, andM is invariant for M* (). One of the main ingredients in our technique is the Arveson Extension Theorem and this paper illustrates the great power and tractability of that theorem in a concrete setting.Research partially supported by NSF grant MCS 81-02518 相似文献
83.
Katharine F. Bowes George Ferguson Christopher Glidewell John N. Low Antonio Quesada 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(9):o551-o554
N,N′‐Dithiobisphthalimide crystallizes from nitrobenzene solution as a solvate, 2C16H8N2O4S2·C6H5NO2, having space group Pn. The bisphthalimide molecules are linked by C—H?O hydrogen bonds and by aromatic π–π‐stacking interactions, forming a framework enclosing continuous channels running along the [100] direction and accounting for ca 20% of the unit‐cell volume. The nitrobenzene molecules lie in these channels, ordered in a head‐to‐tail fashion and linked to the bisphthalimide framework by C—H?O and C—H?π(arene) hydrogen bonds. 相似文献
84.
Jiménez JC Chavarría B López-Macià A Royo M Giralt E Albericio F 《Organic letters》2003,5(12):2115-2118
[reaction: see text] A solid-phase method for the synthesis of tentoxin has been developed. Two key steps-dehydration and N-alkylation-are carried out while the peptide is anchored to the resin. The method, which has been validated by the preparation of a library of tentoxin analogues, should be applicable to the generation of further libraries that have the tentoxin scaffold structure, as well as other structures containing N-alkylated didehydroamino acids. 相似文献
85.
The absorption spectra of natural yellow sapphires are shown to be due to single Fe3+ and Fe3+ O2− Fe3+ pairs, with the latter dominant. Blue and green sapphires have spectra dominated by Fe3+ O2− Ti4+ and Fe2+ O2− Fe3+ pairs. 相似文献
86.
Choudhury M. Zakaria George Ferguson Alan J. Lough Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):m1-m4
In the adduct ferrocene‐1,1′‐diylbis(diphenylmethanol)–1,2‐bis(4‐pyridyl)ethene (1/1), [Fe(C18H15O)2]·C12H10N2, there is an intramolecular O—H?O hydrogen bond in the ferrocenediol component and a single O—H?N hydrogen bond linking the diol to the diamine, which is disordered over two sets of sites, so forming a finite monomeric adduct. In the adduct ferrocene‐1,1′‐diylbis(diphenylmethanol)–1,6‐diaminohexane (2/1), 2[Fe(C18H15O)2]·C6H16N2, the amine lies across a centre of inversion in space group P. There is an intramolecular O—H?O hydrogen bond in the ferrocenediol, and the molecular components are linked by O—H?N and N—H?O hydrogen bonds, one of each type, into a C(13)[R(12)] chain of rings. 相似文献
87.
Francisco Ros Pilar Jiménez María Victoria Roux 《Monatshefte für Chemie / Chemical Monthly》2007,28(4):941-949
The cohesion potential energy of the crystal of one enantiomer of ethyl 3-cyano-3-(3,4-dimethyloxyphenyl)-2,2,4-trimethylpentanoate,
−47.7 ± 0.1 kJ mol−1 (0–90°C), was found out from the heat of sublimation (123.2 ± 5.1 kJ mol−1, 78.6°C) and the kinetic energies for the gas phase and the crystal. It was found that the entropy function of Debye’s theory of solids mathematically agreed with the vibrational entropy of the gas (variationally obtained), allowing to disclose
the vibrational energy using the Debye energy function (E
vib 835.0 kJ mol−1 (78.6°C), E
0 included). E
kin for the crystal (771.1 kJ mol−1 (78.6°C)) was obtained by Debye’s theory with the experimental heat capacity. The cohesion energy represented a moderate part of the sublimation energy.
The cohesion energy of the racemic crystal, −44.2 kJ mol−1, was obtained by the heat of formation of the crystal in the solid state (3.0 kJ mol−1, 83.3°C) and E
kin for the crystal (by Debye’s theory). The decrease in cohesion on formation of the crystal accounted for the energy of formation. The change in potential
energy on liquefaction of the racemate from the gas state was disclosed obtaining added-up E
vib + rot for the liquid in the way as to E
vib for the gas, the Debye entropy function being increasedly suited for the liquid (E
vib + rot 763.4 kJ mol−1 (115.4°C)). Positive ΔE
pot, 13.0 kJ mol−1, arised from the increase in electronic energy (Δ
l
νmean − 154.3 cm−1, by the dielectric nature of the liquid), added to the cohesion energy. 相似文献
88.
A stereospecific requirement for hallucinogenesis applies to certain molecules containing an asymmetric center. Thus, only the R-isomers of substituted phenylisopropylamines and lysergic acid diethylamide are psychotomimetic. The enantiomers of a minor hallucinogen, S(+)- and R(-)-3-(2-aminopropyl)indole (α-methyltryptamine) ( 6a and 6b ) were synthesized via a 5-step manipulation from D - and L -tryptophan ethyl ester hydrochloride, respectively. Optical purity of these two isomers was determined by pmr spectroscopy of their complexes with a europium chiral shift reagent using the indole C2 H signal. 相似文献
89.
Three standardised, capillary zone electrophoresis-electrospray ionisation mass spectrometry (CZE-ESI-MS) methods were developed for the analysis of six drug candidates and their respective process-related impurities comprising a total of 22 analytes with a range of functional groups and lipophilicities. The selected background electrolyte conditions were found to be: 60/40 v/v 10 mM ammonium formate pH 3.5/organic, 60/40 v/v 10 mM ammonium acetate pH 7.0/organic and 10 mM piperidine, pH 10.5, where the organic solvent is 50/50 v/v methanol/acetonitrile. The coaxial sheath flow consisted of either 0.1% v/v formic acid in 50/50 v/v methanol/water, or 10 mM ammonium acetate in 50/50 v/v methanol/water, depending on the mixture being analysed. Factor analysis and informational theory were used to quantify the orthogonality of the methods and predict their complementarities. The three selected CZE-ESI-MS methods allowed the identification of 21 out of 22 of all the drug candidates and their process-related impurities and provided orthogonality with four established high-performance liquid chromatography-mass spectrometry (HPLC-MS) methods. These methodologies therefore form the basis of a generic approach to impurity profiling of pharmaceutical drug candidates and can be applied with little or no analytical method development, thereby offering significant resource and time savings. 相似文献
90.
Pericàs MA Puigjaner C Riera A Vidal-Ferran A Gómez M Jiménez F Muller G Rocamora M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(18):4164-4178
New families of enantiopure bis(oxazolines) with 4,5-trans (5 a-g) or 4,5-cis (6 c) stereochemistry at the individual rings have been prepared in high yield. Their eta(3)-allyl palladium complexes (8 a-g, 9 c and 10) have been used as catalytic precursors in allylic alkylation reactions with excellent enantioselectivities (up to 96 %) for the trans oxazoline derivatives, while Pd/6 c system was inactive. NMR studies on palladium eta(3)-1,3-diphenylallyl intermediates (11 a, c and e) showed the presence of syn/syn- and syn/anti-allyl isomers in solution; this resembles the first example of eta(3)-eta(1)-eta(3) isomerism in Pd allylic complexes containing bis(oxazolines) derived from malonic acid. 相似文献