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51.
Charles Bullock 《Fresenius' Journal of Analytical Chemistry》1872,11(1):192-193
Ohne Zusammenfassung 相似文献
52.
J. H. Kastle J. H. Bullock Etard und Moissan 《Fresenius' Journal of Analytical Chemistry》1898,37(5):324
Ohne Zusammenfassung 相似文献
53.
The fibre optic Doppler anemometer (FODA) has been used to develop an accurate quantitative method of routinely assessing bull fertility. This method is of importance to the artificial insemination industry because the present qualitative estimation, performed by viewing semen using a microscope, can only set broad limits of quality.Laser light from the FODA was directed into diluted semen samples and the back scattered light was measured. A digital correlator was used to calculate the signal correlation of the back scattered light. The resultant data curves were interpreted in terms of the collective motility and swimming speed of the spermatozoa using a microcomputer. These two parameters are accepted as being indicative of fertility. The accuracy of this method is demonstrated by examination of results obtained in an experiment where enzymes, thought to alter fertility, were added to semen. The effect of the enzymes on the swimming speed and motility was clearly demonstrated. 相似文献
54.
Dr. Allan Jay P. Cardenas Bojana Ginovska Dr. Neeraj Kumar Dr. Jianbo Hou Dr. Simone Raugei Dr. Monte L. Helm Dr. Aaron M. Appel Dr. R. Morris Bullock Dr. Molly O'Hagan 《Angewandte Chemie (International ed. in English)》2016,55(43):13509-13513
The fastest synthetic molecular catalysts for H2 production and oxidation emulate components of the active site of hydrogenases. The critical role of controlled structural dynamics is recognized for many enzymes, including hydrogenases, but is largely neglected in designing synthetic catalysts. Our results demonstrate the impact of controlling structural dynamics on H2 production rates for [Ni(PPh2NC6H4R2)2]2+ catalysts (R=n‐hexyl, n‐decyl, n‐tetradecyl, n‐octadecyl, phenyl, or cyclohexyl). The turnover frequencies correlate inversely with the rates of chair–boat ring inversion of the ligand, since this dynamic process governs protonation at either catalytically productive or non‐productive sites. These results demonstrate that the dynamic processes involved in proton delivery can be controlled through modification of the outer coordination sphere, in a manner similar to the role of the protein architecture in many enzymes. As a design parameter, controlling structural dynamics can increase H2 production rates by three orders of magnitude with a minimal increase in overpotential. 相似文献
55.
56.
Dr. Ba L. Tran Dr. Benjamin D. Neisen Dr. Amy L. Speelman Dr. Thilina Gunasekara Dr. Eric S. Wiedner Dr. R. Morris Bullock 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(22):8723-8731
We report mechanistic studies on the insertion reactions of [(NHC)Cu(μ-H)]2 complexes with carbonyl substrates by UV-vis and 1H NMR spectroscopic kinetic studies, H/D isotopic labelling, and X-ray crystallography. The results of these comprehensive studies show that the insertion of Cu-H with an aldehyde, ketone, activated ester/amide, and unactivated amide consist of two different rate limiting steps: the formation of Cu-H monomer from Cu-H dimer for more electrophilic substrates, and hydride transfer from a transient Cu-H monomer for less electrophilic substrates. We also report spectroscopic and crystallographic characterization of rare Cu-hemiacetalate and Cu-hemiaminalate moieties from the insertion of an ester or amide into the Cu−H bond. 相似文献
57.
Mock MT Chen S Rousseau R O'Hagan MJ Dougherty WG Kassel WS DuBois DL Bullock RM 《Chemical communications (Cambridge, England)》2011,47(44):12212-12214
Cis and trans-Cr-N(2) complexes supported by the diphosphine ligand P(Ph)(2)N(Bn)(2) have been prepared. Positioned pendant amines in the second coordination sphere influence the thermodynamically preferred geometric isomer. Electronic structure calculations indicate negligible Cr-N(2) back-bonding; rather, electronic polarization of N(2) ligand is thought to stabilize Cr-N(2) binding. 相似文献
58.
Amy L. Speelman Ba L. Tran Jeremy D. Erickson Monica Vasiliu David A. Dixon R. Morris Bullock 《Chemical science》2021,12(34):11495
Most ligand designs for reactions catalyzed by (NHC)Cu–H (NHC = N-heterocyclic carbene ligand) have focused on introducing steric bulk near the Cu center. Here, we evaluate the effect of remote ligand modification in a series of [(NHC)CuH]2 in which the para substituent (R) on the N-aryl groups of the NHC is Me, Et, tBu, OMe or Cl. Although the R group is distant (6 bonds away) from the reactive Cu center, the complexes have different spectroscopic signatures. Kinetics studies of the insertion of ketone, aldimine, alkyne, and unactivated α-olefin substrates reveal that Cu–H complexes with bulky or electron-rich R groups undergo faster substrate insertion. The predominant cause of this phenomenon is destabilization of the [(NHC)CuH]2 dimer relative to the (NHC)Cu–H monomer, resulting in faster formation of Cu–H monomer. These findings indicate that remote functionalization of NHCs is a compelling strategy for accelerating the rate of substrate insertion with Cu–H species.Remote modification of an N-heterocyclic carbene ligand with bulky or electron-rich groups in [(NHC)Cu(μ-H)]2 increases the rate of substrate insertion, which kinetics studies suggest arises from changes in the Cu–H monomer–dimer equilibrium. 相似文献
59.
Dr. Shaoguang Zhang Dr. Haixia Li Dr. Aaron M. Appel Prof. Michael B. Hall Dr. R. Morris Bullock 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(28):9493-9497
Unusual cleavage of P?C and C?H bonds of the P2N2 ligand, in heteroleptic [Ni(P2N2)(diphosphine)]2+ complexes under mild conditions, results in the formation of an iminium formyl nickelate featuring a C,P,P‐tridentate coordination mode. The structures of both the heteroleptic [Ni(P2N2)(diphosphine)]2+ complexes and the resulting iminium formyl nickelate have been characterized by NMR spectroscopy and single‐crystal X‐ray diffraction analysis. Density functional theory (DFT) calculations were employed to investigate the mechanism of the P?C/C?H bond cleavage, which involves C?H bond cleavage, hydride rotation, Ni?C/P?H bond formation, and P?C bond cleavage. 相似文献
60.
P. C. Bosetti H. Gr?ssler D. Lanske R. Schulte K. Schultze G. T. Jones R. W. L. Jones B. W. Kennedy S. W. O'Neale C. Geich-Gimbel B. Nellen B. Wünsch H. Klein D. R. O. Morrison H. Wachsmuth E. Simopoulou A. Vayaki K. W. J. Barnham F. Hamisi D. B. Miller M. M. Mobayyen S. Wainstein M. Aderholz D. Hantke E. Hoffmann U. F. Katz J. Kern N. Schmitz W. Wittek C. Albajar J. R. Batley G. Myatt D. H. Perkins D. Radojicic P. Renton S. Saitta T. Bolognese J. Velasco D. Vignaud F. W. Bullock S. Burke WA WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1990,46(3):377-385
The transverse momentum distributions of hadrons produced in neutrino-nucleon charged current interactions and their dependence onW are analysed in detail. It is found that the components of the transverse momentum in the event plane and normal to it increase withW at about the same rate throughout the availableW range. A comparison withe + e ? data is made. Studies of the energy flow and angular distributions in the events classified as planar do not show clear evidence for high energy, wide angle gluon radiation, in contrast to the conclusion of a previous analysis of similar neutrino data. 相似文献