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91.
92.
K.E. Gottschalk R.G. Hiskey L.G. Pedersen K.A. Koehler 《Journal of Molecular Structure》1982,87(2):155-159
Ab initio calculations at the STO—3G level have been performed on the binding of CA(II) ion to malonate and formate with and without d orbitals in the basis set for the CA(II) ion. The malonate and formate binding results with CA(II) are similar. The addition of d orbitals to CA(II) has little effect on the conformational minimum. The results are qualitatively similar to those from our previous calculations on the Mg2+—malonate interaction: a single carboxyl interaction with the metal ion appears to be preferred over a conformation in which two carboxyl groups bind to Ca(II). Moreover, the single carboxyl group interaction with CA(II) appears to be favored over the binding of CA(II) to a single oxygen of a carboxyl group. 相似文献
93.
Niels Olaf Østerberg Torben Smith Sørensen Jørgen Birger Jensen 《Journal of Electroanalytical Chemistry》1981,119(1):93-108
The emf of electrochemical cells containing various sorts of salt bridges between various concentrations has been measured. The net diffusion potential over a salt bridge has been treated theoretically. An expression to calculate the net diffusion potential has been derived and tested on values estimated from the emf measurements. A merit factor has been calculated for a saturated KCl bridge separating two HCl solutions and compared with the merit factor estimated from emf measurements on the cell:Pt|Ag|AgCl, HCl(c1)|KCl(sat)|HCl(c2), AgCl|Ag|Pt The practical performance of two commonly used reference electrodes with salt bridges has been tested on emf measurements on KBr solutions. 相似文献
94.
Intravenous administration of Gd-DTPA prior to DWI does not affect the apparent diffusion constant 总被引:2,自引:0,他引:2
Chen G Jespersen SN Pedersen M Pang Q Horsman MR Stødkilde-Jørgensen H 《Magnetic resonance imaging》2005,23(5):685-689
MRI measurements of water diffusion and blood perfusion are increasingly used for the evaluation of organ functionality and tissue viability (e.g., in tumors). While diffusion-weighted imaging is performed without contrast agents, measurement of blood perfusion is normally performed based on the administration of paramagnetic substances such as gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Simultaneous measurements of these two parameters are often preferred. However, it may be argued that Gd-DTPA causes constriction of small blood vessels or alters hemodynamic parameters such as blood viscosity, thereby corrupting subsequent measurements of the apparent diffusion constant (ADC). The objective of the current study was to investigate the possible changes in the ADC in tumors following intravenous administration of 0.2 and 0.4 mmol/kg of Gd-DTPA in mice. The study was conducted with C3H mouse mammary carcinomas inoculated in the right foot of the animal subjects. The results were compared with findings in a sham group, demonstrating that Gd-DTPA had no significant impact on the ADC as measured in a 7-T animal system. 相似文献
95.
Dispersion limits performance in many optical systems. In surface plasmon resonance (SPR) biosensors, the sensing area is an optical element in which the dispersion depends on the effective refractive index of the biochemical compounds to be measured. We report a method of compensating for wavelength dispersion in SPR biosensors employing two integrated diffractive optical coupling elements in a polymer substrate. The dispersion compensation is achieved over the whole dynamic measurement range and provides a biosensor more robust to wavelength fluctuations than prism-coupler SPR systems. The concept can readily be employed in other types of sensor measuring refractive-index changes. 相似文献
96.
Two types of operation for metal-clad waveguide sensors, peak-type and dip-type operation, are described. The newly discovered peak-type operation [Sens. Actuators B 94, 304 (2003)] can be achieved by use of a few-nanometers-thick cladding of a metal with a large imaginary permittivity, whereas conventional dip-type operation is obtained with a metal cladding with small imaginary permittivity some tens of nanometers thick. Both types of operation are described, and the main differences are illustrated. 相似文献
97.
Kreckel H Motsch M Mikosch J Glosík J Plasil R Altevogt S Andrianarijaona V Buhr H Hoffmann J Lammich L Lestinsky M Nevo I Novotny S Orlov DA Pedersen HB Sprenger F Terekhov AS Toker J Wester R Gerlich D Schwalm D Wolf A Zajfman D 《Physical review letters》2005,95(26):263201
The energy-resolved rate coefficient for the dissociative recombination (DR) of H(3)(+) with slow electrons has been measured by the storage-ring method using an ion beam produced from a radiofrequency multipole ion trap, employing buffer-gas cooling at 13 K. The electron energy spread of the merged-beams measurement is reduced to 500 microeV by using a cryogenic GaAs photocathode. This and a previous cold- measurement jointly confirm the capability of ion storage rings, with suitable ion sources, to store and investigate H(3)(+) in the two lowest, (J,G) = (1,1) and (1,0) rotational states prevailing also in cold interstellar matter. The use of para-H(2) in the ion source, expected to enhance para-H(3)(+) in the stored ion beam, is found to increase the DR rate coefficient at meV electron energies. 相似文献
98.
Suppose given a Galois étale cover YX of proper non-singular curves over an algebraically closed field k of prime characteristic p. Let H be its Galois group, and G any finite extension of H by a p-group P. We give necessary and sufficient conditions on G to be the Galois group of an étale cover of X dominating YX.in final form: 16 September 2003 相似文献
99.
Wessel N Konvicka J Weidermann F Nestmann S Neugebauer R Schwarz U Wessel A Kurths J 《Chaos (Woodbury, N.Y.)》2004,14(1):23-29
In the last decade, there has been an increasing interest in compensating thermally induced errors to improve the manufacturing accuracy of modular tool systems. These modular tool systems are interfaces between spindle and workpiece and consist of several complicatedly formed parts. Their thermal behavior is dominated by nonlinearities, delay and hysteresis effects even in tools with simpler geometry and it is difficult to describe it theoretically. Due to the dominant nonlinear nature of this behavior the so far used linear regression between the temperatures and the displacements is insufficient. Therefore, in this study we test the hypothesis whether we can reliably predict such thermal displacements via nonlinear temperature-displacement regression functions. These functions are estimated first from learning measurements using the alternating conditional expectation (ACE) algorithm and then tested on independent data sets. First, we analyze data that were generated by a finite element spindle model. We find that our approach is a powerful tool to describe the relation between temperatures and displacements for simulated data. Next, we analyze the temperature-displacement relationship in a silent real experimental setup, where the tool system is thermally forced. Again, the ACE algorithm is powerful to estimate the deformation with high precision. The corresponding errors obtained by using the nonlinear regression approach are 10-fold lower in comparison to multiple linear regression analysis. Finally, we investigate the thermal behavior of a modular tool system in a working milling machine and again get promising results. The thermally induced errors can be estimated with 1-2 microm accuracy using this nonlinear regression analysis. Therefore, this approach seems to be very useful for the development of new modular tool systems. 相似文献
100.
[reaction: see text] The organometallic intermediate obtained from halogen-metal exchanges of 4-iodo-6-phenylthieno[2,3-d]pyrimidine under Barbier-type conditions was reacted with aldehydes to form the corresponding alcohols in moderate yields. The reaction involving an organolithium intermediate proceeded only at low temperature, whereas the reaction involving a magnesium ate intermediate also proceeded at room temperature. A crystal structure confirms that the expected constitutional alcohol isomer is formed, where no migration has taken place. The conditions were also suitable for 9-benzyl-6-iodopurine. 相似文献