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1.
A successful application of ultrasound Doppler velocimetry in liquid sodium flows is described. To obtain sufficient Doppler
signals, different problems had to be solved: the transmission of the ultrasonic beam through the channel wall made of stainless
steel, the acoustic coupling between the transducer and the channel wall, and the wetting of the inner surface of the wall
by the liquid metal, respectively. A sodium flow in a square duct exposed to a transverse magnetic field is investigated.
In accordance with the existing knowledge about MHD channel flows, we found that the velocity profiles modified to a M-shape
owing to the effect of an inhomogeneous magnetic field.
Received: 12 June 2001/Accepted: 27 October 2001 相似文献
2.
We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing
it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate
εF
2(x,Q)2/ε In Q
2 using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data. 相似文献
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Both, dielectric continuum solvation models as well as surface or group based methods using polarity and lipophilicity parameters have been proven to be useful tools for the analysis of solvation and partition questions. For the first time, COSMO-RS provides an integrated theory, which combines the aspects of continuum solvation and surface interactions, and which ends up with chemical potentials of molecules in almost arbitrary solvents and mixtures. Due to its sound theoretical basis, COSMO-RS does not only provide a new quantitative access to solvation and partition properties in well defined solvents, but it also opens a novel view and gives a better understanding of the general problem of solvation. Finally, this allows for a generalisation of COSMO-RS to sophisticatedphysiological partition problems involving as complex phases as blood, brain, or cell membranes. The use of COSMO-RS for drug discovery and design is demonstrated by applications to blood-brain partition coefficients, and water solubility. 相似文献
9.
Abstract— Absorption changes induced in isolated chloroplasts by excitation with repetitive flash groups have been measured at 690 nm, indicating the photochemical turnover of chlorophyll-aII (Chl-αn), and at 480 nm and 513 nm respectively, reflecting via electrochromic effect the formation of a transmembrane electric field. The data are compared with measurements of oxygen evolution. In chloroplasts with practically fully intact oxygen evolving capacity it was found: 1. The initial amplitude of the 690 nm absorption change induced by the second flash as a function of the time tv between the first and second flash of a group increases with a half life of about 35 µs. On the other hand, the average oxygen yield due to the second flash as a function of the time tv rises with a half life of about 600 µs (and a kinetics in the ms-range of minor extent), confirming the data of Vater et al. (1968). 2. Under far red background illumination, where contributions due to PS I in the µs-range can be excluded, the difference spectrum in the red of the absorption changes induced by the first flash corresponds with that of the absorption changes induced by the second flash fired 200 µ after the first flash. 3. The pattern of the absorption changes at 690 nm induced by repetitive double flash groups at tv= 200 µs does not markedly change in normal chloroplasts by the presence of DBMIB?. Similar 690 nm absorption changes occur in trypsin treated chloroplasts, independent of the presence of DCMU. 4. The fast regeneration in the µs-range of Chl-an is also observed in the third flash of a triple flash group at a time tv= 200 µs between the flashes of the group. 5. The initial amplitudes of the absorption changes with a decay kinetics slower than 100 µs induced by the second flash at 480 nm and 513 nm, respectively, as a function of the time t, between the first and second flash of a group, are characterized by a recovery half-time of about 600 µs, confirming earlier measurements at 520 nm (Witt and Zickler, 1974). On the basis of these results it is inferred that there does exist a photoreaction of Chl-αn., with an electron acceptor, referred to as Xa, other than the ‘primary’ plastoquinone acceptor X320, if X320 persists in its reduced state. Under conditions of X320 being in the reduced state, this photochemical reaction was shown to be highly dissipative with respect to charging up the watersplitting enzyme system Y. Furthermore, this Chl-an-photoreaction with Xa does not lead to a vectorial transmembrane charge separation, which is stable for more than a few microseconds. Different models for the functional and structural organization of PS II are discussed. 相似文献
10.
The COSMO-RS method, originally developed for the prediction of liquid-liquid and liquid-vapor equilibrium constants based on quantum chemical calculations, has been extended to solid compounds by addition of a heuristic expression for the Gibbs free energy of fusion. By this addition, COSMO-RS is now capable of a priori prediction of aqueous solubilities of a wide range of typical neutral drug and pesticide compounds. Only three parameters in the heuristic expression have been fitted on a data set of 150 drug-like compounds. On these data an rms deviation of 0.66 log-units was achieved. Later, the model was tested on a set of 107 pesticides, which have been critically selected based on two experimental data sources and by a crosscheck with an independent HQSAR model. On this data set an rms of 0.61 log-units was achieved, without any adjustments to the structurally extremely diverse pesticides. This result verifies the ability of this extended COSMO-RS to predict aqueous solubilities of drugs and pesticides of almost arbitrary structural classes. The new method is COSMO-RSol. 相似文献