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排序方式: 共有241条查询结果,搜索用时 0 毫秒
31.
Michael J. Lacey Colin G. Macdonald Kevin F. Donchi Peter J. Derrick 《Journal of mass spectrometry : JMS》1981,16(8):351-357
Ion currents obtained for fragmentations in a mass spectrometer of reversed geometry have been represented as three-dimensional surfaces, which are termed ‘ion current surfaces’. In addition to ion current, useful dimensions of the ion current surfaces are a parameter ln(|ρ|) where ρ = (V0/V)(E/E0) and a parameter ln(|m*|) where m* = (V0/V)mB. Each ion reaction occurring in the source and flight path gives rise to a pattern of peaks and ridges on the surface. If the major features of the surface corresponding to each ion reaction are projected onto the zero ion current plane, they are disposed in a characteristic trapezoidal pattern. All simple and linked modes of scanning correspond to cross-sections of the surfaces, and representing the scanning modes in this light facilitates the identification of ‘cross-talk’. 相似文献
32.
The synthesis is reported of fifteen three-ring 2,5-disubstituted pyridines and two pyridine-N-oxides where the pyridine rings carry a variety of alkyl, aryl, cyclohexyl, cyclohexylethyl and fluorinated-aryl substituents. The mesomorphic transition temperatures for these compounds have been measured; all the compounds show enantiotropic phases. The different substituent effects are discussed and comparisons are made with previous work on analogous systems where the hetero-function is replaced by C-F. 相似文献
33.
M. Csanád T. Csörgő A. Ster B. Lörstad N. N. Ajitanand J. M. Alexander P. Chung W. G. Holzmann M. Issah R. A. Lacey 《The European Physical Journal A - Hadrons and Nuclei》2008,38(3):363-368
Recent PHOBOS measurements of the excitation function for the pseudo-rapidity dependence of the elliptic flow in Au + Au collisions
at RHIC have posed a significant theoretical challenge. Here we show that these differential measurements, as well as the
RHIC measurements on transverse momentum satisfy a universal scaling relation predicted by the Buda-Lund model, based on exact
solutions of perfect fluid hydrodynamics. We also show that the recently found transverse kinetic energy scaling of the elliptic
flow is a special case of this universal scaling. 相似文献
34.
Iván Ayuso-Fernández Dr. Antonio L. De Lacey Prof. Dr. Francisco J. Cañada Dr. Francisco J. Ruiz-Dueñas Prof. Dr. Angel T. Martínez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(11):2708-2712
To investigate how ligninolytic peroxidases acquired the uniquely high redox potential they show today, their ancestors were resurrected and characterized. Unfortunately, the transient Compounds I (CI) and II (CII) from peroxide activation of the enzyme resting state (RS) are unstable. Therefore, the reduction potentials (E°′) of the three redox couples (CI/RS, CI/CII and CII/RS) were estimated (for the first time in a ligninolytic peroxidase) from equilibrium concentrations analyzed by stopped-flow UV/Vis spectroscopy. Interestingly, the E°′ of rate-limiting CII reduction to RS increased 70 mV from the common peroxidase ancestor to extant lignin peroxidase (LiP), and the same boost was observed for CI/RS and CI/CII, albeit with higher E°′ values. A straightforward correlation was found between the E°′ value and the progressive displacement of the proximal histidine Hϵ1 chemical shift in the NMR spectra, due to the higher paramagnetic effect of the heme Fe3+. More interestingly, the E°′ and NMR data also correlated with the evolutionary time, revealing that ancestral peroxidases increased their reduction potential in the evolution to LiP thanks to molecular rearrangements in their heme pocket during the last 400 million years. 相似文献
35.
Dr. Óscar Gutiérrez‐Sanz Dr. Paolo Natale Dr. Ileana Márquez Dr. Marta C. Marques Sonia Zacarias Dr. Marcos Pita Dr. Inês A. C. Pereira Dr. Iván López‐Montero Dr. Antonio L. De Lacey Dr. Marisela Vélez 《Angewandte Chemie (International ed. in English)》2016,55(21):6216-6220
ATP, the molecule used by living organisms to supply energy to many different metabolic processes, is synthesized mostly by the ATPase synthase using a proton or sodium gradient generated across a lipid membrane. We present evidence that a modified electrode surface integrating a NiFeSe hydrogenase and a F1F0‐ATPase in a lipid membrane can couple the electrochemical oxidation of H2 to the synthesis of ATP. This electrode‐assisted conversion of H2 gas into ATP could serve to generate this biochemical fuel locally when required in biomedical devices or enzymatic synthesis of valuable products. 相似文献
36.
Inside Back Cover: H2‐Fueled ATP Synthesis on an Electrode: Mimicking Cellular Respiration (Angew. Chem. Int. Ed. 21/2016) 下载免费PDF全文
37.
Kavallaris N. I.; Lacey A. A.; Nikolopoulos C. V.; Voong C. 《IMA Journal of Applied Mathematics》2007,72(5):597-616
A non-local parabolic equation modelling linear friction weldingis studied. The equation applies on the half line and containsa non-linearity of the form . For f(u) = eu, global existence and convergence to a steadystate are proved. Numerical calculations are also carried outfor this case and for f(u) = (– u)1/a. 相似文献
38.
Gaber El-Enany Matthew J. Lacey Phil A. Johns John R. Owen 《Electrochemistry communications》2009,11(12):2320-2323
Polyacrylonitrile (PAN) films were grown on glassy carbon, nickel foam and MnO2 substrates by cathodic electropolymerisation of acrylonitrile in acetonitrile with tetrabutylammonium perchlorate (TBAP) as the supporting electrolyte. The electronic barrier properties of the films were confirmed by impedance spectroscopy of carbon |PAN| Hg cells while the ionic resistance of the films varied from 200 kΩ cm2 in the dry state to 1.4 Ω cm2 when plasticised with 1 M LiPF6 in propylene carbonate. A galvanic cell was prepared by successive electrodepositions of MnO2 and PAN on a carbon substrate, using liquid lithium amalgam as the top contact. The cell showed a stable open circuit potential and behaved normally under the galvanostatic intermittent titration technique (GITT). 相似文献
39.
Karolina Haberska Cristina Vaz-Domínguez Antonio L. De Lacey Marius Dagys Curt T. Reimann Sergey Shleev 《Bioelectrochemistry (Amsterdam, Netherlands)》2009,76(1-2):34
In an effort to find conditions favouring bioelectrocatalytic reduction of oxygen by surface-immobilised human ceruloplasmin (Cp), direct electron transfer (DET) reactions between Cp and an extended range of surfaces were considered. Exploiting advances in surface nanotechnology, bare and carbon-nanotube-modified spectrographic graphite electrodes as well as bare, thiol- and gold-nanoparticle-modified gold electrodes were considered, and ellipsometry provided clues as to the amount and form of adsorbed Cp. DET was studied under different conditions by cyclic voltammetry and chronoamperometry. Two Faradaic processes with midpoint potentials of about 400 mV and 700 mV vs. NHE, corresponding to the redox transformation of copper sites of Cp, were clearly observed. In spite of the significant amount of Cp adsorbed on the electrode surfaces, as well as the quite fast DET reactions between the redox enzyme and electrodes, bioelectrocatalytic reduction of oxygen by immobilised Cp was never registered. The bioelectrocatalytic inertness of this complex multi-functional redox enzyme interacting with a variety of surfaces might be associated with a very complex mechanism of intramolecular electron transfer involving a kinetic trapping behaviour. 相似文献
40.
A model for the melting of polymers, assuming the polymer crystalstake the form of lamellæ, or thin sheets, of material,is discussed. The model is derived on the assumption that themelting point of a lamella depends upon its thickness, thata lamella melts the instant this temperature is exceeded, andthat lamellæ with higher melting points grow by accumulatingsurplus melt. The model is analysed for a temperature controlthat is the sum of a linear and a sinusoidal function of time,as in modulated-temperature differential scanning calorimetry,which is a new experimental technique for measuring thermalproperties of materials. Some predictions regarding the outputof such calorimetry for polymer melting are made. 相似文献