Masking of manganese in relation to stepwise complexometric determination of calcium, magnesium and manganese

A critical study has been made of the masking of manganese with potassium cyanide in alkaline medium for complexometric titration of calcium and magnesium. It has been found that there is incomplete oxidation to manganese(III) unless the solution is aged for a sufficient period or air is bubbled through the solution at 35 ± 5° for 10 min. The manganese(III) complex can be reduced with ascorbic acid for titration with EDTA. Procedures are given for stepwise titration of magnesium, manganese and calcium in silicate materials. Mixed indicators are used, to improve the end-points.     

Synthetic studies towards complex diterpenoids—VI : New synthetic routes to tetracyclic bridged-bicyclo[3.2.1]octane intermediates by intramolecular alkylation reactions through α-diazomethyl ketones of hydroaromatic γ,δ-unsaturated acids

Two new synthetic routes to a number of tetracyclic intermediates, for the total synthesis of some diterpenoids incorporating the bicyclo[3.2.1]octane moiety, are described. The syntheses of the bicyclo[3,2,1]octane derivatives begin with preparation of the hydroaromatic γ,δ-unsaturated acids 6, 15 and 17, and proceed via the α-diazomethyl ketones to the corresponding pentacyclic ketones 20, 24 and 26 by an intramolecular carbenoid insertion reaction, followed by a regiospecific acid-catalysed cleavage of the aromatic conjugated cyclopropane bond to the respective unsaturated ketones 27, 29 and 30. The second route to these unsaturated ketones involves a single step boron trifluoride etherate catalysed intramolecular alkylation in the corresponding α-diazomethyl ketones. The tetracyclic ketones 31, 34 and 35 were obtained in quantitative yields by a regiostereospecific hydrogenolytic cleavage of the aromatic conjugated cyclopropane bond in the respective pentacyclic precursors with PdC in ethanol. Under the same conditions, reduction of the styrenoid bond in the ketones 29 and 30 proceeds stereospecifically leading to 34 and 35 respectively, whereas the unsaturated ketone 27 gave a mixture of epimeric ketones 31 and 32 in a ratio of 69:31.     

Axisymmetric shrink fit problems of the elastic cylinder of finite length

The general case of the axisymmetric shrink fit problems of a solid elastic cylinder whose ends are free from tractions is formulated in terms of the Fredholm integral equation of the second kind. This is accomplished by the use of Papkovich-Fadle eigenfunction and the calculus of residues. Indentation by three types of sleeve is considered; (i) Edge Sleeve, (ii) Symmetrical central Sleeve and, (iii) Two identical edge sleeves. For each case, numerical results of effective resistance and contact pressure are reported for various values of the Poisson's ratio, radius of the cylinder and the sleeve width.

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Zusammenfassung Der allgemeingültige Fall achsensymmetrischer Schrumpf-Anpassungs probleme eines elastischen Festzylinders dessen Enden zugkraftfrei sind wird in der Form der zweiten Integral-gleichung von Fredholm ausgedrückt. Dies wird durch die Anwendung der Papkovich-Fadle Eigenfunktion und der Residuenrechung erreicht. Drei Arten von Manteleinkerbungen werden untersucht: (i) einseitige Endeinkerbung, (ii) symmetrische Zentraleinkerbung, (iii) zweiseitige Endeinkerbung. Für jeden Testfall werden die Zahlenergbnisse des effektiven Winderstandes und des Berührungsdruckes für verschieden Werter der Poisson Ratio, des Zylinderradius und der Mantelkerbweite berichtet.

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The present results were obtained in the course of research supported by NSF Grand GK-25604.     

Hydrodynamic theory of plasma oscillations in quasi-two-dimensional systems

We show that a hydrodynamic theory can be applied to calculate the dispersion relation of plasma oscillations in a quasi-two-dimensional system. It also leads to the conclusion that additional “multipole” modes may exist in the system.     

Exact solution of damped nonlinear Schrödinger equation for a parabolic density profile

An exact single envelope soliton solution of the damped nonlinear Schrödinger equation in a medium with a parabolic density profile has been obtained. It is found that the condition of reflection of the soliton from the density hump is determined by its initial velocity and the scale lengths of the inhomogeneity.     

Measurement of mercaptans in gasoline

In an r-FIA single-line manifold, 10-l portions of 5,5-dithiobis (2-nitrobenzoic acid) and 2% (v/v) ethylenediamine in 80 20 inethanol: acetone are injected from pressurized containers via high-speed on/off valves into a flowing gasoline stream. The reaction product, 2-nitro-5-mercaptobenzoate, is detected optically at 412 nm after a reaction time of 15s. The system is intended for the measurement of mercaptans in the 0–2 mM (0–64 ppm S) concentration range. The response for C1–C10n-mercaptans ranges from 0.766–0.159 mAU/mM, the response to C1–C5n-mercaptans is 630 mAU/mM (±18.5% RSD). The response ratio of C1 and C5 mercaptans is 1 0.653. The system permits extreme conservation of reagents; only 10 l of each reagent is consumed per determination.     

Borel complexity of the space of probability measures

Using a technique developed by Louveau and Saint Raymond, we find the complexity of the space of probability measures in the Borel hierarchy: if is any non-Polish Borel subspace of a Polish space, then , the space of probability Borel measures on with the weak topology, is always true , where is the least ordinal such that is .

     

Fusion suppression and sub-barrier breakup of weakly bound nuclei

The mechanism for the large suppression of complete fusion in the 9Be+208Pb reaction has been investigated through measurement of sub-barrier breakup of 9Be. Excluding breakup through the 8Be ground state, whose lifetime is too long, a prompt breakup component remains, having sufficient probability to explain the observed suppression of complete fusion. This appears to be associated with interactions at the nuclear surface. The fusion suppression is predicted to be almost proportional to the charge of the target nucleus, making it most significant in reactions with heavy nuclei.     

Experimental persistence probability for fluctuating steps

The persistence behavior for fluctuating steps on the Si(111)-(sqrt[3]xsqrt[3])R30 degrees -Al surface was determined by analyzing time-dependent STM images for temperatures between 770 and 970 K. Using the standard persistence definition, the measured persistence probability displays power-law decay with an exponent of theta=0.77+/-0.03. This is consistent with the value of theta=3/4 predicted for attachment-detachment limited step kinetics. If the persistence analysis is carried out in terms of return to a fixed-reference position, the measured probability decays exponentially. Numerical studies of the Langevin equation used to model step motion corroborate the experimental observations.