Electrocapillarity behavior of Au111 in SO4(2-) and F-

We present the first set of results measuring the change in interfacial free energy and surface stress for Au(111) electrodes in an electrolyte containing a nonspecifically adsorbing anion and compare this behavior to that in an electrolyte containing an anion known to undergo specific adsorption. Generally, we find that the surface stress is more sensitive to changes in electrode potential and adsorption then the interfacial free energy. The results obtained in fluoride electrolytes are compared to the predictions of a thermodynamic analysis.     

Dehydrogenation of tetralin on cobalt and nickel modified type X zeolites

The dehydrogenation of tetralin on cobalt and nickel modified NaX zeolites has been studied in a flow system at atmospheric pressure and 390–430 °C. A method for comparing the activity of the zeolite catalysts is proposed.

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NaX , 390–430 °C. .

     

The mechanism of silver granular electrodeposits formation

Granules as a possible form of metal electrodeposit can be formed during deposition of metals, such deposition processes being characterized by large exchange current density values. Because of this, zero nucleation zones around growing grains are formed, permitting granular metal growth. In some cases of prolonged deposition, macro-crystalline deposits can be formed as well as granular ones, e.g. in the case of silver deposition at overpotentials lower than the critical value for dendrite growth initiation. The mechanism of granular deposit growth as a final form of metal electrocrystallization is proposed. Silver boulders were deposited on␣platinum and silver substrates. At low deposition potentials, various crystallographic forms, some of them ideal or derived from cube-octahedron-type morphology, were obtained as a result of independent grain growth inside zones of zero nucleation. In addition to cube-octahedra, twinned and multiply twinned silver particles were also observed. The nucleation density was found (1) to increase with increasing deposition overpotential, (2)␣to decrease with increasing silver concentration, and (3) to be greater on Ag than on Pt for the same deposition overpotential and dendrite precursors. Increasing overpotential leads to increase of density of twinned grains. The grain growth at greater overpotentials from more concentrated solution is less ideal, producing a granular deposit on prolonged deposition. Received: 21 April 1997 / Accepted: 18 September 1997     

The Ozonolysis of Longifolene: A Tool for the Preparation of Useful Chiral Compounds. Configuration Determination of New Stereogenic Centers by NMR Spectroscopy and X‐Ray Crystallography

The ozonolysis of (+)‐longifolene ( 1 ) in different solvents (Et₂O, CH₂Cl₂, CHCl₃, acetone) at ?80° provided quantitatively longifolene epoxide ( 3 ) as a single diastereoisomer in which the O‐atom is endo‐positioned (Scheme 2). Upon warming to room temperature, the epoxide remained stable only in acetone and was isolated as a low‐melting crystalline compound. In CH₂Cl₂, Et₂O, or CHCl₃ solution, epoxide 3 rapidly rearranged to the isomeric enols 4 and 5 , which underwent further rearrangement to give the exo‐aldehyde 6 . On standing for several weeks in CH₂Cl₂ solution, or in CHCl₃ and Et₂O as well, at room temperature, aldehyde 6 slowly rearranged into its epimer 7 . The aldehydes 6 and 7 were isolated on the preparative scale for further synthetic use. The addition of methylmagnesium iodide to 6 and 7 provided the corresponding alcohols 13 / 14 and 15 / 16 , respectively, which were isolated as pure diastereoisomers (Scheme 4). The configurations of the new chiral centers in 13 – 16 were determined by NMR methods and X‐ray crystallography.     

Influence of Electro-Acoustic Effects on the Electro-Optic Response of Charged Colloids

Low-frequencyanomalous electro-optic behavior of colloidal systems (sign reversal and deviations from Kerr low) is considered in the light of electrically induced acoustic modes. The latter were recently detected and investigated in samples of isotropic spherical particles. Their linear dependence on field intensity explains the low-field “permanent dipole” behavior of charged colloids. The coupling of anisotropy and density fluctuations results in the complicated frequency curves of the electro-optic responses of anisometric particles.     

Use of FITC as a Fluorescent Probe for Intracellular pH Measurement

Fluorescein Isothiocyanate (FITC) is widely used in biology and medicine as a fluorescent marker for labeling various proteins. Particularly fluorescence marking of antibodies could not be imagined without FITC. However, at the same time FITC displays pH-indicative properties. This paper evaluates the limits of the use of FITC as a pH indicator in biological material, namely, for intracellular and intraorganellar pH measurement.     

Integration of Polyharmonic Functions

The results in this paper are motivated by two analogies. First, -harmonic functions in are extensions of the univariate algebraic polynomials of odd degree . Second, Gauss' and Pizzetti's mean value formulae are natural multivariate analogues of the rectangular and Taylor's quadrature formulae, respectively. This point of view suggests that some theorems concerning quadrature rules could be generalized to results about integration of polyharmonic functions. This is done for the Tchakaloff-Obrechkoff quadrature formula and for the Gaussian quadrature with two nodes.

     

A refinement of the Gauss-Lucas theorem

The classical Gauss-Lucas Theorem states that all the critical points (zeros of the derivative) of a nonconstant polynomial lie in the convex hull of the zeros of . It is proved that, actually, a subdomain of contains the critical points of .

     

Characterization of double oxide system Cu-Cr-O supported on <Emphasis Type="Italic">γ</Emphasis>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

Series of alumina supported chromium-copper catalysts were prepared by co-impregnation method. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and UV-visible diffuse reflectance spectroscopy. Dispersion and porosity was also obtained. The experimental and catalytic test results have drawn a conclusion that an interaction between copper and chromium ions takes place. This interaction is responsible for the enhanced catalytic activity of studied catalysts in reaction of total oxidation of industrial formaldehyde production exhaust gas, which contains CO, dimethyl ether and methanol as main components. The article is published in the original.