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41.
42.
If sample pretreatment, nebulization and method of calibration are suitably adapted to each other the performance of inductively coupled plasma - mass spectrometry ICP-MS can be greatly increased. High accuracy is obtained by high precision and low bias. For a given concentration higher sensitivity means higher count rates and therefore higher precision. Systematic errors are minimized by employing a definitive method of calibration. Increased sensitivity is obtained by introducing higher amounts of sample into the measurement system via high efficiency nebulizers (ultrasonic nebulizer, hydraulic-high pressure nebulizer according to Berndt and concentric high efficiency nebulizer according to Meinhard). Because this means also higher matrix effects a combination of ion chromatographic (IC-TMS) and thermal trace-matrix-separation by aerosol desolvation (T-TMS) is introduced. Isotope dilution (ID) proves to be the calibration most suitable to achieve the highest accuracy. First applications on the analysis of refractory metals (e.g. Ti, V, Nb, Ta) and non-metals (e.g. P, S, As, Se) showed recoveries of 60-105%, an imprecision of the recoveries of 2-50%, but an overall inaccuracy of only 0.1 to 4%. 相似文献
43.
The simplified sialyl Lewisx mimic 5 containing a D ‐arabinose, a 3‐cyclohexyl‐2‐hydroxypropanoate, and a tetrahydropyran building block instead of L ‐fucose, sialic acid, and N‐acetylglucosamine, respectively was synthesized. Compound 5 was 10‐fold more potent than sLex in a static E‐selectin binding assay and showed at 50 μM 75% inhibition in a dynamic‐flow assay in which sLex did not inhibit neutrophil rolling at up to 1000 μM . Compound 7 with a lactic acid instead of sialic acid building block showed threefold improved potency compared to sLex. 相似文献
44.
Gerold Alsmeyer 《Mathematical Methods of Operations Research》1986,30(3):A111-A134
Let
1, 2, ... be a sequence of i.i.d. random variables with positive mean
and finite variance
and letr(b), b0, be real numbers tending to 0 asb . Definings
n=1+...+n andS
n=Sn(b)=sn+r(b)n, the stopping time =(b)=inf {n>/1:Sn >b} whereb=b(b) , will be considered with special regard to the excess over the boundaryR
b=s+r(b)–b. It turns out that the limiting distribution ofR
b is the same as in the caser(b)0 for allb. Proving this, Blackwell's renewal theorem and its integral version have to be established first in the above stated situation. Finally, an expansion ofE to vanishing terms asb will be provided and applied to some examples arising in economics.
Zusammenfassung Seien 1, 2, ... unabhängige identisch verteilte Zufallsgrößen mit positivem Erwartungswert und endlicher Varianz sowier(b), b0, reelle Zahlen mitr(b)0 für b. Sei ferners 1, s2, ... der zugehörige Summenprozeß,S n= Sn(b)=sn+r(b)n fürn1 und =(b)=inf {n1: Sn>b, wobeib=b(b) fürb . Es wird gezeigt, daß die asymptotische Verteilung des ExzessesR b=s +r(b) –b mit der im Fallr(·)0 übereinstimmt. Dazu werden sowohl das Blackwellsche Erneuerungstheorem als auch seine Integralversion in der vorher beschriebenen parameterabhängigen Situation geeignet formuliert und bewiesen. Als Folgerung ergibt sich dann eine asymptotische Entwicklung vonE(b) fürb bis zu Termen o(1). Anh- and einiger Beispiele aus dem ökonomischen Bereich wird schließlich noch aufgezeigt, wo Approximationen fürE(b) von Interesse sein können.相似文献
45.
46.
Günther J. Redhammer Gerold Tippelt 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(10):1091-1095
Dilithium tetragermanate is orthorhombic, space group P21ca, at 298 K, and is thus in a polar and probably a ferroelectric state. The structure contains two independent Li, four Ge and nine O atoms, all on general positions with site symmetry 1. Three tetrahedrally coordinated Ge positions form crumpled crankshaft‐like chains, forming sheets within the ac plane, and these are interconnected by the fourth, octahedrally coordinated, Ge sites along the b direction. The GeO4 tetrahedra and GeO6 octahedra form a three‐dimensional framework containing two different cavities, hosting the two 4+1‐coordinated Li sites. Cooling to 90 K does not alter the space‐group symmetry; the tetrahedral chains behave as a rigid unit and changes occur mainly within the Li coordination spheres. 相似文献
47.
Svetlin Mitov Gerold Hübner Hans‐Peter Brack Günther G. Scherer Emil Roduner 《Journal of Polymer Science.Polymer Physics》2006,44(23):3323-3336
Three different electron beam irradiated fluoropolymers (ETFE, FEP, and PVDF) as well as their grafting reactions with styrene in different diluents were investigated by means of electron spin resonance (ESR). Depending on the atmosphere during irradiation, ESR spectra of peroxy and alkyl radicals were observed. Radical decay as a function of time and temperature was investigated in the presence and absence of solvent. Grafting levels and number of monomer units per chain were calculated for both types of radicals. Irradiation atmosphere, grafting temperature, and added solvent affect the morphology of the fluoropolymers, in particular the crystalline versus amorphous fractions and their swelling. They thus influence the rate at which the initial radicals at the polymer backbone are reached during the grafting process. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3323–3336, 2006 相似文献
48.
Schwarzenbach und Diakonow 《Fresenius' Journal of Analytical Chemistry》1868,7(1):277-282
Ohne Zusammenfassung 相似文献
49.
On the Harris Recurrence of Iterated Random Lipschitz Functions and Related Convergence Rate Results 总被引:1,自引:0,他引:1
Gerold Alsmeyer 《Journal of Theoretical Probability》2003,16(1):217-247
A result by Elton(6) states that an iterated function system
of i.i.d. random Lipschitz maps F
1,F
2,... on a locally compact, complete separable metric space
converges weakly to its unique stationary distribution if the pertinent Liapunov exponent is a.s. negative and
for some
. Diaconis and Freedman(5) showed the convergence rate be geometric in the Prokhorov metric if
for some p>0, where L
1 denotes the Lipschitz constant of F
1. The same and also polynomial rates have been recently obtained in Alsmeyer and Fuh(1) by different methods. In this article, necessary and sufficient conditions are given for the positive Harris recurrence of (M
n
)
n0 on some absorbing subset
. If
and the support of has nonempty interior, we further show that the same respective moment conditions ensuring the weak convergence rate results mentioned above now lead to polynomial, respectively geometric rate results for the convergence to in total variation or f-norm
f
, f(x)=1+d(x,x
0)
for some (0,p]. The results are applied to various examples that have been discussed in the literature, including the Beta walk, multivariate ARMA models and matrix recursions. 相似文献
50.
Separation of andrographolide and neoandrographolide from the leaves of Andrographis paniculata using high-speed counter-current chromatography 总被引:4,自引:0,他引:4
The bioactive diterpenes andrographolide and neoandrographolide from the leaves of Andrographis paniculata NEES (Acanthaceae) were successfully separated by counter-current chromatography. A single 280-min separation yielded 189 mg of 99.9% andrographolide and 9.5 mg of 98.5% neoandrographolide applying water-methanol-ethyl acetate-n-hexane (2.5:2.5:4:1) solvent system. Structure confirmation was done by electrospray MS, one-dimensional NMR experiments, circular dichroism, optical rotation dispersion, and specific optical rotation [alpha]D. 相似文献