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51.
The contactless movement of microparticles and cells to known locations within a fluid volume is of interest in the fields of microtechnology and life sciences. A device which can position such inhomogeneities suspended in a fluid at multiple locations is described and modeled. The device consists of a thin fluid layer contained in a channel etched into a silicon wafer. Waves are excited by a macro-piezoelectric plate with electrodes on the top and bottom surfaces and, as a result, waves propagate into the adjacent fluid. The result is a pressure field throughout the fluidic volume. When an inhomogeneity in a fluid is exposed to an ultrasonic field the acoustic radiation force results; this is found by integrating the pressure over the surface of the particle, retaining second order terms, and taking the time average. Thus, due to the presence of a pressure field in the fluid in which the particles are suspended, a force field is created. The particles are then collected at the locations of the force potential minima. In the device described here, the force field is used to position particles into lines. The locations of the particles are predicted by using a finite element model of the system. The experimental and modeling results, presented here, are in good agreement. 相似文献
52.
53.
In the present study a forced liquid flow through an open capillary channel is investigated experimentally and numerically under reduced gravity conditions (microgravity). An open capillary channel is a structure that establishes a liquid flow path at low Bond numbers, when the capillary pressure caused by the surface tension force dominates in comparison to the hydrostatic pressure induced by gravitational or residual accelerations. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
54.
Manfred Haake Winfried Jürgler Ralf Spreemann 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):315-316
Abstract Nucleophilic C-S bond cleavage of Sulfonediimines to Sulfinamidine-type Structures is discussed 相似文献
55.
Abstract Evidence of rearrangement of 3-acyl derivatives of ascorbic acid to 2-acyl derivatives has been found for carbon and phosphorus acyl groups. The observations are consistent with intramolecular rearrangement through a cyclic intermediate in which the acyl group is bonded to both the 2- and 3-oxygen atoms of ascorbic acid. A rate of rearrangement has been measured for the 3-diphenylphosphinate ester. Calculated results indicate an increase in negative atomic charge at O-2 in the 3-acyl esters but a decrease in the charge of O-3 in the 2-acyl esters. 相似文献
56.
Petr A. Braun Peter Gerwinski Fritz Haake Henning Schomerus 《Zeitschrift für Physik B Condensed Matter》1996,100(1):115-127
We discuss semiclassical approximations of the spectrum of the periodically kicked top, both by diagonalizing the semiclassically approximated Floquet matrix F and by employing periodic-orbit theory. In the regular case when F accounts only for a linear rotation periodic-orbit theory yields the exact spectrum. In the chaotic case the first method yields the quasienergies with an accuracy of better than 3% of the mean spacing. By working in the representation where the torsional part of the Floquet matrix is diagonal our semi-classical work is mostly an application of the asymptotics of the rotation matrix, i. e. of Wigner’s so-called d-functions. 相似文献
57.
58.
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
59.
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
60.
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