Forces of a fluid in a rotating straight pipe

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.     

Development of novel antioxidants: design,synthesis, and reactivity

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.     

13C-NMR relaxation studies of alkali metal cryptate complexes

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.     

Toluol-3,4-dithiol und verwandte 1,2-Dithiolene als Chelatbildner für Metalle

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.

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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.

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Mit 5 Abbildungen

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Herrn Prof. Dr.O. Hromatka zum 65. Geburtstag gewidmet.     

Development of flow-injection liposome immunoanalysis (FILIA) for imazethapyr

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.     

The surface-enhanced Raman spectrum of N-methylpyridinium ion on a silver electrode

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.     

Determination of fluoride by analate additions potentiometry

Summary A novel direct potentiometric technique called analate additions potentiometry has been applied to the determination of fluoride using a fluoride ion selective indicator electrode. As expected, the analytical results are comparable to those obtained by the standard additions technique. An error of less than 1 part in 1000 and a precision of about 0.5% was achieved. The technique should be most useful in the determination of small sample volumes which cannot be done by the standard additions method without prior dilution.

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Zusammenfassung Ein neues, direktes potentiometrisches Verfahren wurde für die Fluoridbestimmung angewendet, wobei eine für Fluoridionen selektive Indikatorelektrode verwendet wurde. Wie erwartet sind die Ergebnisse dieses Probenzusatzverfahrens mit denen der Standardzusatzmethode vergleichbar. Der Fehler ist kleiner als l, die Genauigkeit beträgt etwa 0,5%. Das angegebene Verfahren eignet sich vor allem zur Analyse kleiner Probevolumina, die ohne vorherige Verdünnung mit der Standardzusatzmethode nicht analysiert werden können.

     

Flow-injection liposome immunoanalysis (FILIA) for alachlor

An automated Flow-Injection Liposome ImmunoAnalysis (FILIA) system has been modified from a previous design, using a specific environmental contaminant, the herbicide alachlor, as a model analyte. Signal amplification by means of fluorescent marker-loaded, analyte-tagged liposomes provides high sensitivity. The computer controlled system is composed of commercially available components, with the exception of the column packing material, which has to be prepared for each specific analyte to be determined. The use of such components means that the system is easily modified. The relationships between antibody concentration and assay speed and sensitivity are explored, and the possibilities of using the system for determination of multiple analytes is discussed.     

Molecular mechanics (MM2) calculations and cone angles of phosphine ligands

Molecular mechanics (MM2) calculations were performed on 54 conformations of 18 phosphines (PH₃; PH_3−nR_n, where n = 1,…3, and R = Me and Et, n = 1 or 2 and R =ⁱPr, and n = 1 and R =^tBu, PMe₂Et, PMeEt₂, and PPhMe₂, and PPh₂R where R = Me, Et, ⁱPr, ^tBu and Ph). The results are compared to those previously obtained from MINDO/3 and MNDO calculations, and to experimental data. Single conformer cone angles and weighted average cone angles were calculated from MM2 optimized geometries employing Tolman's general definition, and they are compared to Tolman's values, MINDO/3 results, and T.L. Brown's E_R values. Of the cone angle definitions used, the weighted average values are suggested as the best single representation of phosphine ligand sizes. The steric parameters (cone angle and E_R values) alone, and in conjunction with electronic parameters, are correlated with experimental data.