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1.
Laurence E. Strong Christopher L. Brummel Robert Ryther John R. Radford Alan D. Pethybridge 《Journal of solution chemistry》1988,17(12):1145-1167
Precision molar conductances of benzoic, o-toluic, 2,6-dimethylbenzoic, 2,3,6-trimethylbenzoic, and, o-fluorobenzoic acids have been determined in aqueous solution as a function of temperature and of concentration up to near saturation (<0.035 M). At the higher concentrations molar conductances are found to be less than anticipated for the simple dissociation of a 1-1 electrolyte. Although the deviations are only 1% or less they have been interpreted to show that these acids are dimerized in solution. The interpretation includes an assumption that the dimer ionizes to produce a triple ion. Increasing numbers of methyl groups lead to increasing dimerization. For those acids with two ortho groups the dimerization increases with increasing temperature while the other three show decreasing dimerization with increasing temperature. Temperature functions have been determined for the dimerization constants and from these functions standard changes in enthalpy, entropy, and heat capacity have been determined. Comparisons are made with dimerization studies in non-aqueous solvents. From these as well as the behavior of benzene in water it is concluded that a major factor driving the dimerization is hydrophobic interaction. To provide a limiting conductance of the triple ion needed in the dimerization calculations a conductance study was also made for o-Phenylbenzoic acid on the assumption that its anion provides an approximate model of the triple ion. 相似文献
2.
Abramowicz H Belusevic R Blondel A Blümer H Böckmann P Brummel HD Buchholz P Burkhardt H Debu P Duda J Dydak F Falkenburg B Fiedler M Geiges R Geweniger C Grant AL Guyot C Hagelberg R Hepp V Hughes EW Kampschulte B Keilwerth H Kleinknecht K Knobloch J Krasny M Królikowski J Kurz N Lipniacka A Merlo J Müller E Para A Perez P Perrier F Pollman D Ranjard F Renk B Schuller J Taureg H Tittel K Turlay R Vallage B Wachsmuth H Wotschack J 《Physical review letters》1986,57(3):298-301
3.
Cumulant functions are introduced to describe the statistical state of a radiation field. These functions are simply related
to the optical coherence functions but have some interesting features. It is shown that if the cumulant functions of all orders
greater than some numberN
0 vanish then they also vanish for all orders greater than 2. Thermal field is the only field having this property. This property
holds whether the field is described by a classical stochastic process or by a quantum density operator. Further the particular
operator ordering used in defining these cumulant functions for the quantized field affects only the second order cumulant
function. To describe the statistical state of a vector field such as partially polarized or unpolarized radiation, one would
need to introduce cumulant tensors. 相似文献
4.
MA Freitas CL Hendrickson AG Marshall 《Rapid communications in mass spectrometry : RCM》1999,13(15):1639-1642
We present a novel approach for the determination of activation energy for the unimolecular dissociation of a large (>50 atoms) ion, based on measurement of the unimolecular dissociation rate constant as a function of continuous-wave CO(2) laser intensity. Following a short ( approximately 1 s) induction period, CO(2) laser irradiation produces an essentially blackbody internal energy distribution, whose 'temperature' varies inversely with laser intensity. The only currently available method for measuring such activation energies is blackbody infrared radiative dissociation (BIRD). Compared with BIRD, FRAGMENT: (a) eliminates the need to heat the surrounding ion trap and vacuum chamber to each of several temperatures (each requiring hours for temperature equilibration); (b) offers a three-fold wider range of effective blackbody temperature; and (c) extends the range of applications to include initially cold ions (e.g., gas-phase H/D exchange). Our FRAGMENT-determined activation energy for dissociation of protonated bradykinin, 1.2 +/- 0.1 eV, agrees within experimental error to the value, 1.3 +/- 0.1 eV, previously reported by Williams et al. from BIRD experiments. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
5.
6.
P. Berge H. Burkhardt F. Dydak R. Hagelberg M. W. Krasny H. J. Meyer P. Palazzi F. Ranjard J. Rothberg J. Steinberger H. Taureg H. Wahl R. W. Williams J. Wotschack H. Blümer H. D. Brummel P. Buchholz J. Duda F. Eisele B. Kampschulte K. Kleinknecht J. Knobloch E. Müller B. Pszola B. Renk T. Alvarez R. Belusevic B. Falkenburg R. Geiges C. Geweniger V. Hepp H. Keilwerth K. Tittel P. Debu C. Guyot J. P. Merlo A. Para P. Perez F. Perrier B. Peyaud J. P. Schuller R. Turlay B. Vallage H. Abramowicz J. Królikowski A. Lipniacka 《Zeitschrift fur Physik C Particles and Fields》1991,49(2):187-223
A high-statistics measurement of the differential cross-sections for neutrino-iron scattering in the wide-band neutrino beam at the CERN SPS is presented. Nucleon structure functions are extracted and theirQ 2 evolution is compared with the predictions of quantum chromodynamics. 相似文献
7.
H. Burkhardt F. Dydak J. G. H. DeGroot R. Hagelberg M. Krasny J. May H. J. Meyer P. Palazzi F. Ranjard J. Rothberg D. Schlatter J. Steinberger H. Taureg H. Wahl J. Wotschack H. Blümer H. Brummel P. Buchholz J. Duda F. Eisele B. Kampschulte K. Kleinknecht J. Knobloch E. Müller B. Pszola B. Renk K. Schmitz R. Belusević B. Falkenburg T. Flottmann R. Geiges C. Geweniger V. Hepp H. Keilwerth K. Tittel P. Debu C. Guyot S. Loucatos J. P. Merlo A. Para P. Perez F. Perrier B. Peyaud J. Rander J. P. Schuller R. Turlay B. Vallage H. Abramowicz J. Krolikowski J. H. He T. Z. Ruan W. M. Wu 《Zeitschrift fur Physik C Particles and Fields》1986,31(1):39-49
From exposures of the CDHS detector at the CERN SPS we have obtained 367μ + μ ? events in neutrino beams and 73μ + μ + events in an antineutrino beam. The magnitude of a prompt like-sign signal has been controversial in the past and moreover could not be explained by known production mechanisms. A critical discussion of the experimental situation is given. We have tried to reduce the systematic uncertainties of previous experiments and to get more information on the dependence of the signal with energy and the muon momentum cut-off. This experiment yields a signal of 2.8σ (2.4σ) of prompt like-sign dimuon events in the case of neutrinos (antineutrinos). The rate to charged current events is of the order of 10?4 forp μ<9GeV andE>100 GeV. The prompt signal has all the properties expected from the production and decay of charm-anticharm events. The magnitude, however, is substantially higher then the prediction of perturbative QCD but lower than some other experiments. 相似文献
8.
9.
Gao H Materne OL Howe DL Brummel CL 《Rapid communications in mass spectrometry : RCM》2007,21(22):3683-3693
Rapid information on metabolic profiling is required to evaluate the structural liabilities of drug candidates in early drug discovery. In this study, a sensitive and rapid semi-quantitative method was developed to simultaneously monitor the drug candidate and metabolites as well as collect tandem mass (MS/MS) spectra for subsequent metabolite identification. The simultaneous semi-quantitation and identification of metabolites in fresh hepatocytes is achieved using high-performance liquid chromatography (HPLC) coupled with a hybrid quadrupole linear ion trap. The survey experiment consists of monitoring multiple-reaction monitoring (MRM) transitions for the internal standard, the parent, and 48 MRM transitions designed to cover the most common phase I and II biotransformations. An information-dependent acquisition (IDA) method was employed to trigger product ion scans above the MRM signal threshold. Three biotransformations of a lead compound have been identified through enhanced product ion scans and the respective MRM transitions of those metabolites were selected for semi-quantitation. Parent disappearance and formation of the metabolites as a function of incubation time in five different species were monitored by their respective MRM responses. The method provides the necessary sensitivity to detect minor metabolites in a relevant therapeutic concentration range. Enzymatic turnover of the parent and the metabolites in different species are revealed based on the different initial concentrations of the parent. This methodology integrates the parent disappearance, metabolite identification, and the formation of the metabolites along the time course using a single rapid LC/MS/MS analysis. This method can be used as a complementary tool to the conventional method of metabolic profiling. It provides a rapid and sensitive initial profile of the metabolism of potential structural series at the lead selection stage. The method can also be incorporated into the overall metabolite profiling scheme to evaluate the drug candidates in drug discovery. 相似文献
10.
A. Blondel P. Böckmann H. Burkhardt F. Dydak A. L. Grant R. Hagelberg E. W. Hughes W. Krasny A. Para H. Taureg H. Wachsmuth J. Wotschack H. Blümer H. D. Brummel P. Buchholz J. Duda B. Kampschulte K. Kleinknecht J. Knobloch E. Müller B. Renk R. Belusević B. Falkenburg R. Geiges C. Geweniger V. Hepp H. Keilwerth K. Tittel H. Abramowicz C. Guyot J. P. Merlo P. Perez F. Perrier J. P. Schuller R. Turlay B. Vallage J. Królikowski A. Lipniacka 《Zeitschrift fur Physik C Particles and Fields》1990,45(3):361-379
The final results from the WA 1/2 neutrino experiment in the 1984 CERN 160 GeV narrow band beam are presented. The ratiosR ν and \(R_{\bar v} \) of neutral to charged current interaction rates of neutrinos and antineutrinos in iron are measured to beR ν=0.3072±0.0033 and \(R_{\bar v} \) =0.382±0.016. A value of the electroweak parameter sin2 θ w = 1 ?m W 2 /m Z 2 is extracted fromR ν. The result is sin2 θ w =0.228+0.013(m c ?1.5)±0.0003 (theor.) wherem c is the mass of the charmed quark in GeV form t =60 GeV,M H =100 GeV, ρ=1. CombiningR ν and \(R_{\bar v} \) one obtains a value for ρ=0.991+0.023(m c ?1.5)±0.020(exp.). Alternatively,R ν and \(R_{\bar v} \) yield a precise value of the ratio of intermediate vector boson massesm W /m Z =0.880?0.007(m c ?1.5)±0.002(exp.)±0.002(theor.). Comparison of these results with those from direct measurements of the vector boson masses are presented. In a model-independent analysis the left- and right-handed neutral current coupling constants,g L 2 andg R 2 , are determined. 相似文献