Ruthenium(II) tris(bipyridyl) ion as a luminescent probe for oxygen uptake on the catalyzed oxidation of HSO(3)(-)

The present work describes an alternative technique for monitoring the rate of oxygen consumption during the oxidation of HSO(3)(-) catalyzed by manganese and iron ions. The method is based on the spectrofluorimetric monitoring of the quenching effect of molecular oxygen on the emission of the photoexcited [Ru(bipy)(3)](2+) ion, added to the reaction mixtures. The effects of Fe(III), at very low concentrations, and of Mn(II) on the oxidation of HSO(3)(-) by dissolved oxygen, have been investigated. The metal ions in the trivalent oxidation state react with HSO(3)(-) to initiate a radical chain reaction in which HSO(3)(-) is oxidized to sulfate and the metal ion is reduced to the divalent state. The synergistic effect of Mn(II) and Fe(III) was clearly evaluated. Possible parallel reactions with the oxygen indicator, [Ru(bipy)(3)](2+), are considered.     

Local shape-preserving interpolation by space curves

In this paper we present an automatic algorithm for the constructionof local shape-preserving interpolating splines in ³. Thesesplines satisfy the convexity and torsion criteria relativeto the polygonal line connecting interpolation points. The resultingcurve has continuous curvature and continuous torsion and isobtained via piecewise polynomials of degree 6. Received 25 November 1998. Accepted 25 April 2000.     

Asymmetric kinks: stabilization by entropic forces

Asymmetric kinks bridging two adjacent potential valleys of equal depth but different curvature are unstable against phonon modes. When coupled to a heat bath, a kink-bearing string tends to cross over into the shallower valley; kinks are thus predicted to drift in the appropriate direction with velocity proportional to the temperature, in close agreement with numerical simulation. When contrasted by a mechanical bias, these entropic forces give rise to a rich phenomenology that includes configurational phase transitions, double-kink dissociation, and noise-directed signal transmission.     

Structure of Entropy Solutions for Multi-Dimensional Scalar Conservation Laws

An entropy solution u of a multi-dimensional scalar conservation law is not necessarily in BV, even if the conservation law is genuinely nonlinear. We show that u nevertheless has the structure of a BV function in the sense that the shock location is codimension-one rectifiable. This result highlights the regularizing effect of genuine nonlinearity in a qualitative way; it is based on the locally finite rate of entropy dissipation. The proof relies on the geometric classification of blow-ups in the framework of the kinetic formulation.     

Unbounded C*-Seminorms and Biweights on Partial *-Algebras

Unbounded C*-seminorms generated by families of biweights on a partial *-algebra are considered and the admissibility of biweights is characterized in terms of unbounded C*-seminorms they generate. Furthermore, it is shown that, under suitable assumptions, when the family of biweights consists of all those ones which are relatively bounded with respect to a given C*-seminorm q, it can be obtained an expression for q analogous to that one which holds true for the norm of a C*-algebra.     

Defects induced by electron irradiation in hollandite ceramics, specific radioactive cesium-host wasteforms: a 57Fe Mössbauer study

Several single phase hollandite ceramics having Ba²⁺ _x Cs⁺ _y (C = Al,Fe)³⁺ _2x+y Ti⁴⁺ _8?2x?y O₁₆ composition have been synthesized and irradiated under external electron beams simulating the β-irradiation of radioactive cesium. These samples have been characterized by ⁵⁷Fe transmission Mössbauer spectroscopy. Mössbauer results show that the irradiation modifies the local arrangements of Ba cations around Fe³⁺ ions by atomic displacement of Ba ions.     

Niosomes from alpha,omega-trioxyethylene-bis(sodium 2-dodecyloxy-propylenesulfonate): preparation and characterization

The synthesis and characterisation of new surfactants with peculiar physical-chemical properties are amongst the most promising and expanding issues in pharmacological colloid science. The most used vesicular carriers are liposomes prepared from a wide variety of natural and synthetic phospholipids, but several ionic and non-ionic amphiphiles have been used to form multilamellar and/or unilamellar vesicles. In the present study the synthesis of alpha,omega-trioxyethylene-bis(sodium 2-dodecyloxy-propylenesulfonate), an anionic Gemini surfactant, and its ability to form niosomes are elucidated. The compound forms vesicles with and without added cholesterol. The vesicular systems were characterized by size, shape and drug entrapment efficiency. The compounds to be incorporated are beta-carotene and ferulic acid, as antioxidants, acetyl salicylic acid, as FANS, and the antineoplastic 5-flurouracil, widely used in dermatological disorders. The results of this study show that alpha,omega-trioxyethylene-bis(sodium 2-dodecyloxy-propylenesulfonate) can be used for the preparation of niosomes entrapping lypophilic, amphiphilic or hydrophilic substances. These niosomes may be promising candidates as percutaneous carriers for the aforementioned drugs.