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971.
Summary A sequence for the fractionation of the amylasic components from a malted barley extract is proposed using two salt-promoted, adsorption processes: thiophilic interaction chromatography (TIC) and hydrophobic interaction chromatography (HIC).Two fractions containing -amylase activity were recovered during the thiophilic chromatography; the first was resolved in to -amylase I and -amylase I by HIC on a phenyl-sepharose column; an enrichment factor of 32 was achieved for -amylase I. The other amylasic component eluted from the thiophilic gel was characterized as -amylase II. Although the adsorption of malt amylases on phenylsepharose and the thiophilic adsorbent is salt promoted, the interactions involved in each case are clearly distinguished by the different behaviour and disparate salt effects. 相似文献
972.
van der Sanden GC Wormer PE van der Avoird A Schmuttenmaer CA Saykally RJ 《Chemical physics letters》1994,226(1-2):22-26
We have calculated state-to-state total cross sections for rotational excitation and inversion of NH3 by collisions with Ar using the close coupling method. The Ar-NH3 interaction potential has been obtained from a fit to the spectrum of this van der Waals molecule. The calculated cross sections agree to within about 30% with the measured values; the estimated error in the latter is 10% to 20%. 相似文献
973.
Let (M, J, g) be a compact Kähler manifold of constant scalar curvature. Then the Kähler class [] has an open neighborhood inH
1,1 (M, ) consisting of classes which are represented by Kähler forms of extremal Kähler metrics; a class in this neighborhood is represented by the Kähler form of a metric of constant scalar curvature iff the Futaki invariant of the class vanishes. If, moreover, the derivative of the Futaki invariant at [] is nondegenerate, every small deformation of the complex manifold (M, J) also carries Kähler metrics of constant scalar curvature. We then apply these results to prove new existence theorems for extremal Kähler metrics on certain compact complex surfaces.The first author is supported in part by NSF grant DMS 92-04093. 相似文献
974.
L. C. M. Kallenberg 《Mathematical Methods of Operations Research》1994,40(2):127-143
This paper deals with some applications of Markov decision models for which the linear programming method is efficient. These models are replacement models (with the optimal stopping problem as special case), separable models (including the inventory model as special case) and the multi-armed bandit model. In the companion paper Survey of linear programming for standard and nonstandard Markovian control problems. Part I: Theory, general linear programming methods are discussed. These linear programming formulations are the starting point for the efficient methods that will be derived for the special models. 相似文献
975.
For natural numbers n, k, r and s there exists a complete tree ? of height and arity $r^{\left( {\mathop {K + 1}\limits_s } \right)} (n - 1) + 1$ such that for an arbitrary r-colouring of the s-chains of T a level-preserving monochromatically embedded copy of a complete tree of height k and arity n can be found in T. Moreover, a best possible upper bound for K is given. 相似文献
976.
Thin PtSi films can be grown by evaporating Pt on Si(100) at RT and subsequent annealing of the system at 600–700 K. Contaminants like oxygen are known to have a strong influence on this reaction. In the present study we concentrate on the effect of oxygen partial pressure during the annealing on the silicide growth process. Under proper vacuum conditions annealing at 500 K leads to a homogeneous Pt2Si film which reacts around 600 K completely to PtSi. A substantial oxygen partial pressure ( 0.1 mbar) in contrast results in an incomplete reaction in the same temperature range: unreacted platinum remains at the surface separated from the silicide by an oxygen enriched layer.Presented at the Seminar on Secondary Electrons in Electron Spectroscopy, Microscopy, and Microanalysis, Chlum (The Czech Republic), 21–24 September, 1993.This work was supported by Deutsche Forschungsgemeinschaft (DFG) through Sonderforschungsbereich 292.We thank Dr. W. Platz (Deutsche Aerospace AG, Ottobrunn) for providing us with Pt evaporated Si-wafers and Th. Hierl (Lehrstuhl für Angewandte Physik, University of Erlangen-Nürnberg), who performed the RBS measurements for AES calibration. 相似文献
977.
978.
P. Dalmas De Reotier A. Yaouanc P. C. M. Gubbens B. Chevalier 《Hyperfine Interactions》1994,85(1):227-232
We have studied bySR spectroscopy the intermetallicsUTr
2Si2 where Tr=Co, Rh or Pt. Whereas for the Co compound we only get information on the muon localisation site, from the other two materials we obtain information on their electronic properties. We compare the characteristics of theirSR response. 相似文献
979.
Zero and longitudinal field SR has been used to probe the magnetic state of amorphous Bi2Sr2CaCu2Ox prepared by rapid quenching from the melt. The results suggest quasi-static spin correlations between extremely dilute Cu2+ ions.Work performed while at the J J Thomson Physical Laboratory, University of Reading. 相似文献
980.
A. Yaouanc P. Dalmas De Reotier P. C. M. Gubbens A. A. Moolenaar A. A. Menovsky C. E. Snel 《Hyperfine Interactions》1994,85(1):351-356
We report zero field and longitudinal fieldSR measurements on single crystals of the ferromagnet PrRu2Si2 (T
c15K). BetweenT=T
c and 250K we observe a quasi-static spin dynamics of the Pr3+ ion sub-lattice. BelowT
c, depending on the orientation of the initial muon beam polarisation relative to thec axis of the compound, we find either an oscillating signal or an exponential depolarisation function. These latter data allow us to get information related to the muon in PrRu2Si2. 相似文献