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排序方式: 共有198条查询结果,搜索用时 109 毫秒
1.
The fluid flow through a rotating straight pipe is considered, the axis of rotation being perpendicular to the pipe axis. The flow of the fluid is taken as fully developed, i.e. the velocity field is assumed to be the same in all transverse cross sections of the pipe. The derivation presented applies to viscous and nonviscous incompressible fluids. For constant angular pipe velocity a simple and exact (Coriolis type) relationF=2Q(t) is derived between the forceF by which the fluid acts on the (unit length of the) pipe in the direction perpendicular to the two axes, the fluid mass flow rateQ(t) through the pipe, and the angular velocity. Variable angular velocities, i.e.
, introduce an additional term into the expression for the inertial forceF, which depends only on
and on known (constant) parameters; this term is known for given angular velocity(t). The flow configuration investigated here is an idealization of those appearing (over short space and time intervals) in the devices measuring mass flow rateQ(t) through the (Coriolis) forceF. Therefore the exact results derived here cast some light on the degree of precision one expects in these devices, where more complicated flow configurations are present than those looked at in this paper. 相似文献
2.
Derivatization of solid soda-lime glass spheres with aminosilanes and the stability of these groups near physiological pH in flow streams of aqueous buffered solutions are described. The presence of immobilized and adsorbed amines in the nanomolar range is confirmed by using two independent methods, one based on a radiotracer and the other on the fluorescent marker, fluorescamine. A method for covalently attaching bovine serum albumin to the beads is described. 相似文献
3.
Hussain HH Babic G Durst T Wright JS Flueraru M Chichirau A Chepelev LL 《The Journal of organic chemistry》2003,68(18):7023-7032
We are attempting to develop novel synthetic antioxidants aimed at retarding the effects of free-radical induced cell damage. In this paper we discuss the design strategy and report the synthesis of seven novel antioxidants, including six catechols and a benzylic phenol. The bond dissociation enthalpy (BDE) for the most active (weakest) OH bond in each molecule was calculated by theoretical methods, as well as the BDE for the semiquinone radical. Reaction rates with the nitrogen-centered free radical DPPH(*) were measured in ethyl acetate. The log of k(DPPH) for bimolecular reaction correlated well with the primary BDE. The correlation between rate constants and calculated BDEs shows that the BDE is a good predictor of antioxidant activity with DPPH(*), suggesting that our design criteria are useful and that these compounds should undergo further testing in cell cultures and in animal models. 相似文献
4.
H. Dupont Durst Luis Echegoyen George W. Gokel Angel Kaifer 《Tetrahedron letters》1982,23(43):4449-4452
The 13C spin-lattice relaxation times (T1's) of cryptands [2.1.1], [2.2.1] and [2.2.2] as well as those of the corresponding cryptate complexes with Li+, Na+, and K+ in CDCl3 and CH3OH:D2O (90:10) were measured and the results are interpreted in terms of molecular compression and desolvation effects. 相似文献
5.
Zusammenfassung Das Verhalten verschiedener Komplexe von Metallen mit Dithiol-enen wird behandelt. Die photometrische Bestimmung, ein empfindlicher qualitativer Nachweis in drei Ausführungsformen und das Extraktionsverhalten von Antimon sowie eineDC-Trennung Sb–Sn–Bi–Pb mit Toluol-3,4-dithiol werden beschrieben. Versuche, die Struktur der Antimondithiolate aufzuklären, führen zu 2 Formeln. Die weitere analytische Verwendbarkeit dieser Verbindungsklasse wird diskutiert.
Mit 5 Abbildungen
Herrn Prof. Dr.O. Hromatka zum 65. Geburtstag gewidmet. 相似文献
Toluene-3,4-dithiole and related 1,2-dithiolenes as chelating agents for metals
The behaviour of various metal-dithiolene complexes is studied. The photometric determination, a sensitive qualitative identification in three modes of execution, the extraction behaviour of antimony and aTLC-separation of Sb–Sn–Bi–Pb with 2-toluene-3,4-dithiol are described. Attempts to clarify the antimony-dithiol compounds have yielded two formulas. Further analytical applications of these compounds are discussed.
Mit 5 Abbildungen
Herrn Prof. Dr.O. Hromatka zum 65. Geburtstag gewidmet. 相似文献
6.
Strachan JD Adler H Alling P Ancher C Anderson H Anderson JL Ashcroft D Barnes CW Barnes G Batha S Bell MG Bell R Bitter M Blanchard W Bretz NL Budny R Bush CE Camp R Caorlin M Cauffman S Chang Z Cheng CZ Collins J Coward G Darrow DS DeLooper J Duong H Dudek L Durst R Efthimion PC Ernst D Fisher R Fonck RJ Fredrickson E Fromm N Fu GY Furth HP Gentile C Gorelenkov N Grek B Grisham LR Hammett G Hanson GR Hawryluk RJ Heidbrink W Herrmann HW Hill KW Hosea J Hsuan H Janos A Jassby DL Jobes FC 《Physical review letters》1994,72(22):3526-3529
7.
Lazarus EA Navratil GA Greenfield CM Strait EJ Austin ME Burrell KH Casper TA Baker DR DeBoo JC Doyle EJ Durst R Ferron JR Forest CB Gohil P Groebner RJ Heidbrink WW Hong R Houlberg WA Howald AW Hsieh C Hyatt AW Jackson GL Kim J Lao LL Lasnier CJ Leonard AW Lohr J La Haye RJ Maingi R Miller RL Murakami M Osborne TH Perkins LJ Petty CC Rettig CL Rhodes TL Rice BW Sabbagh SA Schissel DP Scoville JT Snider RT Staebler GM Stallard BW Stambaugh RD St John HE Stockdale RE Taylor PL Thomas DM 《Physical review letters》1996,77(13):2714-2717
8.
Imazethapyr is the herbicide developed for use in leguminous crops. In this study, flow-injection liposome immunoanalysis (FILIA) has been shown to be capable of measuring imazethapyr in a buffered solution with a detection limit of 0.1 ppb through the optimization process. Protein A coated glass beads covalently conjugated with antibody were contained in a glass column, and this column was used as an immunoreactor. Liposomes which encapsulated a fluorescent dye, sulforhodamine B (SRB) or carboxyfluorescein (CF), generated the analytical signal. By loading larger volumes of sample onto the column, it was shown that the detection limit could be lowered. Liposomes containing carboxyfluorescein gave more sensitive response and a lower detection limit than those with sulforhodamine B. Also, improved response was obtained by using a smaller flow cell in the fluorescence detector due to the reduced dilution effect. 相似文献
9.
10.
The SER spectrum is reported for N-methylpyridinium iodide, an organic cation with no unshared electron pair available for interaction with the electrode. Both Raman- and infrared-active bands are observed with small frequency shifts. No SERS is observed for N-methylpyridinium chloride until trace amounts of iodide are added to the solution. 相似文献