Organic Ion Exchangers. Synthesis and Their Behaviour in the Retention of Some Metal Ions

Summary: Three pyridine strong base anion exchangers as beads were obtained by quaternization reactions of a 4-vinylpyridine : 8% divinylbenzene copolymer of gel type. These resins possess methyl / ethyl / butyl radicals as substituents on N⁺ atoms and have exchange capacities of 4.80 mEq/g and 2.10 mEq/mL. For pyridine strong base anion exchangers, the behaviours in the retention processes of Cr(VI) as oxyanions and Ga(III) as [GaCl₄]⁻ complex anion were evaluated with the bath method. All the resins exhibited retention properties, but the retained amounts of the metal cations are different as a function of the alkyl length as substituent on N⁺ atoms and the complex anion nature. Thus, Cr(VI) oxyanions are best retained by the resin with  CH₃ as substituent on N⁺ atoms while [GaCl₄]⁻ complex anion by the resin with  C₄H₉ as substituent on N⁺ atoms. By aminolysis reaction of an ethylacrylate : acrylonitrile : divinylbenzene copolymer as beads of macroporous type with NH₂OH · HCl in the presence of C₂H₅OH a new chelating ion exchanger was performed which contains both amidoxime and hydroxamic acid functional groups. This ion exchanger has the retention property for different metal cations but its retention capacities values are strongly dependent of the nature of metal cation and the counterion as well as pH of the solution. Thus, in the static conditions Zn(II) cation with NOequation/tex2gif-stack-1.gif anion as counterion is retained with the best result at pH = 5. As an example, for the aqueous metal cation solution of 10⁻² M concentration for Zn(NO₃)₂ the resin possess at equilibrium a retention capacity of 6.70 mmol Zn/g dry resin and for Cu(II) from Cu(NO₃)₂ solution of same concentration, the retention capacity is 0.22 mmol Cu/g dry resin and Fe(III) from Fe(NO₃)₃ solution is not retained.     

On adaptive step-size selections in gradient methods

In recent years several proposals for the step-size selection have largely improved the gradient methods, in the case of both constrained and unconstrained nonlinear optimization. We introduce a new step-size rule with some crucial properties. We design step-size selection strategies where the new rule and a standard Barzilai-Borwein (BB) rule can be adaptively alternated to get meaningful convergence rate improvements in comparison with other BB-like gradient schemes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of thermal treatment under high pressure on the quality of a meat sauce

Abstract

It is known that pressure alone is not able to make shelf-stable any food stored in room conditions. Acid products are normally spoiled by enzymes, and low acid products are spoiled even by spore-forming micro-organisms. To overcome the problem the role of heat in the process has been re-evaluated and the possibility of destroying at the same time spores and enzymes has been found. This work compares the effect of sterilisation by High Pressure Processing (HPP) with one of the conventional retort processing techniques. Two batches of meat sauce were kept in room conditions over a year and their quality was evaluated periodically during the shelf life simulation. The physico-chemical characteristics of the retorted ones showed a progressive appearance of the typical thermal damage. The High Pressure Sterilised samples on the contrary showed limited damage, related to the unavoidable pre-heating. Their quality markers were constant over the shelf life evaluated period.     

Conjugate Addition versus Cycloaddition/Condensation of Nitro Compounds in Water: Selectivity,Acid–Base Catalysis,and Induction Period

Nitroacetates and nitroacetamides react in water as in chloroform with electron‐deficient dipolarophiles to give condensation or conjugate addition products under base catalysis. In general, high selectivity towards condensation is observed in water, with shorter induction periods than in chloroform. In water, condensations slowly occur even without base; kinetic profiles evidence the catalytic effect of the base, which should be related to the conversion into the tautomer nitronic acid. Condensations in water provide convenient access to isoxazole derivatives bearing various functional groups including ammonium, carboxy, and carboxyamide.     

Materials and technological aspects of gilded buckles from a North Eastern Medieval Italian context

This study concerns the archaeometric characterization of two artefacts from the medieval site of San Rocco (Castelfranco Veneto, Italy). Both of them belong to a larger set of metallic objects, some being part of tomb ornaments belonging to two very well distinct periods of frequentation of the site. Both items are buckles and they have been selected as representative of two very well-known and established typologies. The older one, at the end of the sixth—beginning of the seventh century AD, is made of silver, although relicts of gold have been found. A number of relevant counterparts of this item have been found in different sites of the Longobard Italy. The main body of the second artefact (second half of the fourteenth century AD) consists of a bent strip of a copper rich alloy, coated on one side with a nearly continuous, decorated, gold layer. This is a so-called lyre-buckle, with a widespread diffusion not only in Italian, but also North European contexts. From the results of the analyses carried out using low-vacuum scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffractometry, information on manufacturing, gilding technology and materials have been obtained that will be an useful benchmark for the archaeometric characterization of similar items from selected collections. In this way, the already established typological affinity of these two classes of items will be extended to technological and materials aspects, also.     

Extreme‐ultraviolet compact spectrometer for the characterization of the harmonics content in the free‐electron‐laser radiation at FLASH

The design and the commissioning results of a portable and compact spectrometer for the high harmonics content characterization of the extreme‐ultraviolet radiation of FLASH (free‐electron laser in DESY, Hamburg, Germany) are presented. The instrument is a grazing‐incidence flat‐field spectrometer equipped with two variable‐line‐spaced gratings; it covers the 2–40 nm wavelength region with a spectral resolution in the 0.1–0.2% range. Both spectral and intensity fluctuations of the fundamental emission and the harmonics are monitored.     

A Shape Optimization Problem on Planar Sets with Prescribed Topology

We consider shape optimization problems involving functionals depending on perimeter, torsional rigidity and Lebesgue measure. The scaling free cost functionals are of the form \(P(\Omega )T^q(\Omega )|\Omega |^{-2q-1/2}\), and the class of admissible domains consists of two-dimensional open sets \(\Omega \) satisfying the topological constraints of having a prescribed number k of bounded connected components of the complementary set. A relaxed procedure is needed to have a well-posed problem, and we show that when \(q<1/2\) an optimal relaxed domain exists. When \(q>1/2\), the problem is ill-posed, and for \(q=1/2\), the explicit value of the infimum is provided in the cases \(k=0\) and \(k=1\).