Liquid-liquid extraction by mixed micellar systems: A new approach for clavulanic acid recovery from fermented broth

This work is the first attempt to apply aqueous two-phase mixed micellar systems (ATPMS) of the nonionic surfactant Triton X-114 and the anionic one AOT to extract clavulanic acid (CA) from broth fermented by Streptomyces clavuligerus. Cloud points were determined in McIlvane buffer pH 6.5 with or without NaCl, and diagram phases/coexistence curves were constructed. CA partition was investigated following a 2(4)-full factorial design in which AOT (0.022, 0.033 and 0.044% w/w), Triton X-114 (1.0, 3.0 and 5.0% w/w) and NaCl (0, 2.85 and 5.70% w/w) concentrations and temperature (24,26 and 28 degrees C) were selected as independent variables, and CA partition coefficient (K(CA)) and yield in the top phase (eta(CA)) as responses. CA partitioned always to the top, micelle-poor phase. The regression analysis pointed out that NaCl concentration and interaction between temperature and Triton X-114 concentration had statistically significant effects on K(CA), while eta(CA) was mainly influenced by temperature, Triton X-114 concentration and their interaction. Different ATPMS compositions were then needed to maximize these responses, specifically 0.022% (w/w) AOT, 5% (w/w) Triton X-114 for K(CA) (2.08), and 0.044% (w/w) AOT, 1% (w/w) Triton X-114 for eta(CA) (98.7%), both at 24 degrees C without NaCl. Since at 0.022% (w/w) AOT, 1% (w/w) Triton X-114 and 28 degrees C without NaCl the system was able to ensure satisfactory intermediate results (K(CA) = 1.48; eta(CA) = 86.3%), these conditions were selected as the best ones. These preliminary results are of concern for possible industrial application, because CA partition to the dilute phase can simplify the subsequent purification protocol. (C) 2011 Elsevier B.V. All rights reserved.

Effect of inulin on growth and acidification performance of different probiotic bacteria in co-cultures and mixed culture with Streptococcus thermophilus

Inulin was used as a prebiotic to improve the quality and consistency of skim milk fermented by Lactobacillus acidophilus (La), Lactobacillus rhamnosus (Lr), Lactobacillus bulgaricus (Lb) and Bifidobacterium lactis (BI) with Streptococcus thermophilus (St), either in binary co-cultures or in cocktail containing all microorganisms. We compared, either in the presence of 40 mg inulin g(-1) or not, the results of the maximum acidification rate (V(max)) and the times to reach it (t(max)), to reach pH 5.0 (t(PH5.0)) and to complete the fermentation (t(f)). Post-acidification, lactic acid formation and cell counts were also compared after either 1 day (D1) or 7 days of storage at 4 degrees C (N). In co-culture, inulin addition to the milk increased V(max), decreased t(max) and t(f), favored post-acidification and exerted a bifidogenic effect. S. thermophilus proved to stimulate the metabolism of the other lactic bacteria and enhanced the product features. After D7, a significant prebiotic effect of inulin was observed in all co-cultures. Either after D1 or D7, the enumerations of Lr and BI in mixed culture markedly decreased compared to their respective co-cultures because of greater competition for the same substrates. (C) 2008 Elsevier Ltd. All rights reserved.

New Mixed Li/Mg and Li/Mg/Zn Amides for the Chemoselective Metallation of Arenes and Heteroarenes

New mixed Li/Mg and Li/Mg/Zn amides have been synthesized starting from readily prepared secondary amines. They allow a highly chemoselective directed magnesiation or zincation of various polyfunctional aromatics and heteroaromatics. The kinetic basicity, solubility and stability of these new bases have been compared with those of the corresponding 2,2,6,6-tetramethylpiperamide-derived bases. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Determining forest structural attributes using an inverted geometric-optical model in mixed eucalypt forests, Southeast Queensland, Australia

The Montreal Process indicators are intended to provide a common framework for assessing and reviewing progress toward sustainable forest management. The potential of a combined geometrical-optical/spectral mixture analysis model was assessed for mapping the Montreal Process age class and successional age indicators at a regional scale using Landsat Thematic data. The project location is an area of eucalyptus forest in Emu Creek State Forest, Southeast Queensland, Australia. A quantitative model relating the spectral reflectance of a forest to the illumination geometry, slope, and aspect of the terrain surface and the size, shape, and density, and canopy size. Inversion of this model necessitated the use of spectral mixture analysis to recover subpixel information on the fractional extent of ground scene elements (such as sunlit canopy, shaded canopy, sunlit background, and shaded background). Results obtained fron a sensitivity analysis allowed improved allocation of resources to maximize the predictive accuracy of the model. It was found that modeled estimates of crown cover projection, canopy size, and tree densities had significant agreement with field and air photo-interpreted estimates. However, the accuracy of the successional stage classification was limited. The results obtained highlight the potential for future integration of high and moderate spatial resolution-imaging sensors for monitoring forest structure and condition. (C) Elsevier Science Inc., 2000.

The Ni-II, Hg-II and Cu-II complexes of 12-membered-ring mixed-donor macrocycles

The structures of diaqua(1,7-dioxa-4-thia-10-azacyclododecane)nickel dinitrate, [Ni(C8H17NO2S)(H2O)(2)](NO3)(2), (I), bis(nitrato-O,O')(1,4,7-trioxa-10-azacyclododecane)mercury, [Hg(NO3)(2)(C8H17NO3)], (II), and aqua(nitrato-O)(1-oxa-4,7,10-triazacyclododecane)copper nitrate, [Cu(NO3)(C8H19N3O)(H2O)]NO3, (III), reveal each macrocycle binding in a tetradentate manner. The conformations of the ligands in (I) and (III) are the same and distinct from that identified for (II). These differences are in agreement with molecular-mechanics predictions of ligand conformation as a function of metal-ion size.

Determination of the stability constants of mercury(II) complexes of mixed donor macrobicyclic encapsulating ligands

The reactions of mercury(II) with the mixed donor encapsulating ligands 3,6,16-trithia-6,11,19-triazabicyclo[6.6.6]icosane (AMN(3)S(3)sar) and 1-amino-8-methyl-6,19-dithia-3,10,13,16-tetraazabicyclo[6.6.6]icosane (AMN(4)S(2)sar) have been studied. NMR ligand-ligand competition experiments with the ligands 1,4,8,11-tetraazaeyclotetradecane ([14]aneN(4)), 1-thia-4,7,10-triazacyclododecane ([12]aneN(3)S) and ethylenediaminetetraacetic acid (EDTA) with AMN(3)S(3)sar and Hg(II) indicated that [14]aneN(4) would be an appropriate competing ligand for the, determination of the Hg(II) stability constant. Calculations indicated the ratio of concentrations of AMN3S3sar, [14]aneN(4) and Hg(II) required for the determination of the stability constant ranged from 1:1:1 to 1:5:1. Refinement of the titration curves yielded log(10)K[Hg(AMN(3)S(3)sar)](2+) = 17.7. A similar competition titration resulted in the determination of the stability constant for the AMN(4)S(2)sar system as log(10)K[Hg(AMN(4)S(2)sar)](2+) = 19.5. The observed binding constants for the mixed N/S donor systems and the hexaaza analogues sar (3,6,10,13,16,19-hexaazabicyclo [6.6.6]icosane) and diamsar (1,8-diamino-3,6,10,13,16,19 -hexazabicyclo [6.6.6] icosane (log(10)K-[Hg(diamsar)](2+) = 26.4; log(10)K[Hg(sar)](2+) = 28.1) differ by approximately ten orders of magnitude. The difference is ascribed not to a cryptate effect but to a mismatch in the Hg-N and Hg-S bond lengths in the N/S systems.

Thermal stability of mixed-cation alpha-sialon ceramics

A series of alpha-sialon (alpha') compositions containing mixed stabilising cations were prepared, by introducing additional CaO to a basic Sm alpha-sialon compositions. The thermal stability of these Sm-Ca-containing alpha-sialon phases was investigated using XRD, SEM and EDXS techniques. It was found that the addition of calcium into the Sm alpha-sialon systems greatly improved the stability of the alpha-sialon phases. Calcium was found to be incorporated into the alpha-sialon structure, coexistent with the samarium, and partitioning of the calcium and samarium was observed between the alpha' phase and grain boundary phases. This indicates a technique which may be used to improve the thermal stability of the alpha' phase while maintaining good refractory phases at the gialon grain boundaries. (C) 2003 Elsevier Science B.V. All rights reserved.

Mixed thin films of a cationic amphiphilic porphyrin and n-alkanes

Langmuir and Langmuir-Blodgett (LB) films of a cationic amphiphilic porphyrin mixed with n-alkanes octadecane and hexatriacontane were prepared and characterized, to examine the influence of the alkanes on film structure and stability. While the structure present in these films was controlled primarily by the porphyrin, the addition of the alkanes resulted in significant changes to both the phase behavior of the Langmuir films and the molecular arrangement of the LB films. These changes, as well as the observed chain length effects, are explained in terms of the intermolecular interactions present in the films.

Surface miscibility of EPC/DOTAP/DOPE in binary and ternary mixed monolayers

Surface pressure (pi)-molecular area (A) curves were used to characterize the packing of pseudo-ternary mixed Langmuir monolayers of egg phosphatidylcholine (EPC), 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) and L-alpha-dioleoyl phosphatidylethanolamine (DOPE). This pseudo-ternary mixture EPC/DOPE/DOTAP has been successfully employed in liposome formulations designed for DNA non-viral vectors. Pseudo-binary mixtures were also studied as a control. Miscibility behavior was inferred from pi-A curves applying the additivity rule by calculating the excess free energy of mixture (Delta G(Exc)). The interaction between the lipids was also deduced from the surface compressional modulus (C(s)(-1)). The deviation from ideality shows dependence on the lipid polar head type and monolayer composition. For lower DOPE concentrations, the forces are predominantly attractive. However, if the monolayer is DOPE rich, the DOTAP presence disturbs the PE-PE intermolecular interaction and the net interaction is then repulsive. The ternary monolayer EPC/DOPE/DOTAP presented itself in two configurations, modulated by the DOPE content, in a similar behavior to the DOPE/DOTAP monolayers. These results contribute to the understanding of the lipid interactions and packing in self-assembled systems associated with the in vitro and in vivo stability of liposomes. (C) 2010 Elsevier B.V. All rights reserved.

One-pot synthesis of mixed (Z)-1,2-bis(organylchalcogene)-1-alkenes precursors of the novel beta-organylthio vinyllithium intermediates

One-pot hydrochalcogenation of 1-phenylthioacetylenes using organylselenolate and organyltellurolate anions generated by the insertions of selenium and tellurium in n-organyl lithium produced (Z)-1,2-bis(organylchalcogene)-1-alkenes. The chemical reactivity of these mixed 1,2-bis(organylchalcogene)-1-alkenes was studied by Te/Li and Se/Li stereoretentive exchanges carried out with n-butyl lithium, furnishing the new intermediate species (Z)-beta-organylthio vinyllithium anions, which were trapped with aldehydes, to give the (Z)-3-hydroxy vinyl thioethers with total control of the regio- and stereochemistry. (c) 2010 Elsevier Ltd. All rights reserved.

The Many Voices of Waly Salomao

This paper discusses the change in the enunciative strategy in Algaravias (1996), written by the Brazilian poet Waly Salomao (1943-2003). This change is specially treated in relation to his previous production which, in my point of view, is re-writed according to the new historical and cultural context.