Advances in Rare Earths Separation and Purification

The conventional method of separation of rare earths by multistage liquid-liquid extraction is still the best processing technology for their separation and purification. One of the most promising developments in the last decade that could have an impact on the rare earths separation technology is the synthesis of mucrocyclic ligands that have a high degree of selectivity in their complexation. Trivalent lanthanides have recently been transported across liquid membranes containing macrocycic ligands. The use of facilitated liquid membranes reactors in the concentration of very dilute rare eaith streams can be very effective in terms of recovery as well as environmental considerations. The electroreduction of E³⁺ to E²⁺ and the electroodixation of Ce³⁺ to Ce⁴⁺ are potential replacements for chemical reaction valence change methods. The electrolytic method eliminates the introduction of other chemical reagents that need to be treated downstream to satisfy environmental codes. Improvements in the design and control of mixer-settlers and other liquid-liquid extraction equipment will result in higher stage efficiency.     

Role of serum viscosity and of pulp content in the vacuum belt drying of pure fruit juices

Vacuum Belt Drying of fruit juice concentrates may be a satisfactory alternative to freeze drying where cost is a limiting factor, and to spray drying where the addition of large amounts of 'carriers', e.g. maltodextrin or glucose syrups, are required to avoid collapse and sticking of the product.
The rheological and structural properties and the drying behaviour of some juice concentrates have been studied in relation to the collapse phenomenon, which is a structure transition associated with the mechanical properties of the system.
Collapse during drying has proved to be mainly related to the viscosity (consistency) of the soluble fraction of the concentrate, i.e. the 'serum', while there is no evidence of an effect of the suspended phase (pulp).
By properly adjusting the serum consistency of the juice with selected pectolytic enzymes and by appropriate mixing of the mash derivatives, apple, pear, apricot, and peach concentrates have been successfully dehydrated by vacuum belt drying, without any addition of 'carrier'-supporting materials. The consistency index of the concentrate serum may be used to assess the suitability of the juice for drying.     

Size and Strategy of Italian Industrial Enterprises (1907-1940): Empirical Evidence and Some Conjectures

Conventional wisdom concerning Italian industry does not fitwell into the general scheme of the Second Industrial Revolutionas constituted by the growth and diffusion of large-size enterprises.This wisdom held that Italian industry was dominated by a smallgroup of large enterprises as a direct consequence of the country'sbackwardness. These enterprises were weak giants, unable toattain the dynamic advantages usually reaped by such organizations.Such interpretations have been generally based on qualitativeevidence because the quantitative evidence is very scanty. Theolder studies suggest a very high concentration, while recentstudies stress the evidence of scale economies and market imperfections.Neither result is convincing for technical reasons. This papertherefore aims at a reassessment based on a newly constructeddatabase of Italian joint stock companies. This evidence doesnot support the traditional view. Rather, it indicated thatconcentration indices are fairly low and that they do not growover the period, the bulk of the firms being of medium sizeand the giant companies few. Although such a situation couldbe attributed to Italian backwardness, the paper concludes thatthis view is too simplistic. It concludes by showing how successfulItalian companies have been able to take advantage of theirsize by means of flexible strategies.     

EFFECT OF CHEMICAL INTERESTERIFICATION ON PHYSICOCHEMICAL PROPERTIES AND INDUSTRIAL APPLICATIONS OF CANOLA OIL AND FULLY HYDROGENATED COTTONSEED OIL BLENDS

Blends of canola oil (CO) and fully hydrogenated cottonseed oil (FHCSO), with 20, 25, 30, 35 and 40% FHCSO (w/w) were interesterified under the following conditions: 0.4% sodium methoxide, 500 rpm stirring, 100C, 20 min. The original and interesterified blends were examined for triacylglycerol composition, melting point, solid fat content (SFC) and consistency. Interesterification caused considerable rearrangement of triacylglycerol species, reduction of trisaturated triacylglycerol content and increase in disaturated-monounsaturated and monosaturated-diunsaturated triacylglycerols in all blends, resulting in lowering of respective melting points. The interesterified blends showed reduced SFC at all temperatures and more linear melting profiles if compared with the original blends. Consistency, expressed as yield value, significantly decreased after the reaction. Iso-solid curves indicated eutectic interactions for the original blends, which were eliminated after randomization. The 80:20, 75:25, 70:30 and 65:35 (w/w) CO: FHCSO interesterified blends showed characteristics which are appropriate for their application as soft margarines, spreads, fat for bakery/all-purpose shortenings, and icing shortenings, respectively.

PRACTICAL APPLICATIONS

Recently, a number of studies have suggested a direct relationship between trans isomers and increased risk of vascular disease. In response, many health organizations have recommended reducing consumption of foods containing trans fatty acids. In this connection, chemical interesterification has proven the main alternative for obtaining plastic fats that have low trans isomer content or are even trans isomer free. This work proposes to evaluate the chemical interesterification of binary blends of canola oil and fully hydrogenated cottonseed oil and the specific potential application of these interesterified blends in food products.     

Isolation of Low-Molecular-Weight Taste Peptides from Vacherin Mont ďOr Cheese

Vacherin cheese samples weie extracted with water and the extracts fractionated by ultrafiltration excluding compounds with a molecular weight less than 1,000. Extract aliquots were fractionated by ligand exchange chromatography on a Sephadex derivative containing N-(2-pyridylmethyl)glycine-groups in Cu²⁺ form, permitting a specific group separation of peptides. Five peptide sub-groups were then chromato-graphed on Aminex A6 and Durrum DC 4 resin. Nine fractions from these separations were characterized by manual gas-phase isofhiocy-anate degradation and HPLC of the amino acid derivatives. Seven peptides could be identified: H-Leu-Pro-OH, H-Val-Pro-OH, H-Phe-Pro-OH, H-Lys-Pro-OH, H-Gly-Pro-Val-Arg-OH, H-Tyr-Pro-OH, and H-Arg-Pro-OH. A partial elucidation of the structure was possible for peptides containing Asp/Pro/Val/Leu, Glu/Leu, and Ala/Pro.     

Purification and Properties of Lipoxygenase in Germinating Sunflower Seeds

An outline for isolating sunflower lipoxygenase (SLO) from germinating seeds is described. With linoleic acid as substrate, SLO optimum pH was 6.2, the temperature of maximum activity was 35°C and the activation energy was 3.4 Kcal/mole. Nordihydroguaiaretic acid was the most effective inhibitor of SLO, while α-tocopherol and diethyldithiocarbamic acid were less effective. Km values for linoleic acid, linolenic acid and methyl linoleate were 6.7, 5.0, and 40.0 μM, respectively. The activity of SLO was lost rapidly at temperatures higher than 50°C. The enzyme was stable when stored at ?20°C or freeze-dried, but not at 4°C in dilute solution. Experiments in micellar solution showed that SLO catalytic power was also maintained in hydrocarbon media with a Km for linoleic acid of 9 mM and a maximum velocity of 36.6 U/mg.     

Secondary zoospores in the algal endoparasite <i>Maullinia ectocarpii</i> (Plasmodiophoromycota)

The present paper deals with the ultrastructure of zoospores produced by the plasmodiophorid Maullinia ectocarpii, living in the marine algal host Ectocarpus siliculosus. The zoospores described here are very similar to secondary zoospores of Polymyxa graminis and Phagomyxa sp. (the latter an algal endoparasite, also). Our results indicate that M. ectocarpii produces two types of plasmodia, and suggest that is a species with a complete life cycle, as it is known for all the Plasmodiophormycota that have been studied. Sporogenic and sporangial plasmodia produce, respectively, primary zoospores with parallel flagella within thick walled resting sporangia, and secondary zoospores with opposite flagella within thin walled sporangia.     

Mass Transfer Correlation Coefficients for Two-Phase Systems: A General Review for Liquid-Liquid

A general review of the mass transfer correlation coefficients available in the literature was done. The emphasis was for liquid-liquid phases and the main mathematical forms of the correlations accessible are reported. In general, there is a necessity of general models. More work has to be done in this area in order to establish more general models that permit reporting only their parameters for a given system and/or equipment.     

A CYBERNETIC APPROACH TO POPULATION DYNAMICS MODELING

Abstract

Some problems arising when modeling population dynamics by means of stochastic difference and differential equations are discussed. For a particular parametrization of logistic growth equations limit diffusion processes are constructed and interpreted in the light of the Ito-Stratonovich controversy. An indirect confirmation of the validity of May's conjecture on the persistence of a population in a randomly varying environment is also obtained. An extension of these results to a wider class of growth equations is finally provided.