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ERAMET, through its subsidiary COMILOG, have rights to a rich niobium and rare earth deposit in Gabon. The Mabounie deposit, is located 50 km from the town of Lambarene, in a fairly remote location. ERAMET has been developing a process to recover value metals for several years, and approached Hatch Ltd. to design a sizeable Demonstration Plant to help them further optimize the process, and prove the flowsheet is technically viable. The process employs concentration techniques to recover an upgraded Nb/REE feed material for processing in the subsequent leach step. Rare earths and niobium are selectively leached, and subsequently precipitated. Following precipitation, rare earths undergo bulk separation and are purified to produce LRE and mixed MRE/HRE products, which will be further processed by Third Parties. This paper provides a high-level overview of the process, summarizes the motivation for a Demonstration Plant in the vicinity of the deposit, and discusses technical challenges faced during the flowsheet definition and design phase. Key challenges are focused on and summaries of the methodologies used to address each challenge, as well as the solutions to overcome the challenges, are discussed. The paper provides motivation for further process simplification and concludes with a project update.

The cold-adapted cellulase CelG has been purified from the culture supernatant of the Antarctic bacterium Pseudoalteromonas haloplanktis and the gene coding for this enzyme has been cloned, sequenced and expressed in Escherichia coli . This cellulase is composed of three structurally and functionally distinct regions: an N-terminal catalytic domain belonging to glycosidase family 5 and a C-terminal cellulose-binding domain belonging to carbohydrate-binding module family 5. The linker of 107 residues connecting both domains is one of the longest found in cellulases, and optimizes substrate accessibility to the catalytic domain by drastically increasing the surface of cellulose available to a bound enzyme molecule. The psychrophilic enzyme is closely related to the cellulase Cel5 from Erwinia chrysanthemi . Both k cat and k cat / K m values at 4 °C for the psychrophilic cellulase are similar to the values for Cel5 at 30–35 °C, suggesting temperature adaptation of the kinetic parameters. The thermodynamic parameters of activation of CelG suggest a heat-labile, relatively disordered active site with low substrate affinity, in agreement with the experimental data. The structure of CelG has been constructed by homology modelling with a molecule of cellotetraose docked into the active site. No structural alteration related to cold-activity can be found in the catalytic cleft, whereas several structural factors in the overall structure can explain the weak thermal stability, suggesting that the loss of stability provides the required active-site mobility at low temperatures.

By using modifiers in platinum catalysts it is possible to modulate the hydrogenation selectivity in α , β -unsaturated aldehydes carbonyl bond with regard to olefinic bond hydrogenation. The challenge is to find an emergent catalytic material able to produce 100% unsaturated alcohol. In this field, 1% Pt/ZnO catalysts were tested in hydrogenation of crotonaldehyde, in gas phase, at atmospheric pressure. The catalysts were prepared by impregnation of ZnO from two different precursors, H 2 PtCl 6 and Pt(NH 3 ) 4 (NO 3 ) 2 , followed by calcination at 673 K and tested after reduction at different temperatures, 473–773 K. The ex-nitrate and ex-chloride catalysts showed quite different catalytic behaviors. The ex-chloride was much more active and selective; in certain conditions 90% crotyl alcohol selectivity was reached. Different techniques (TPR, XRD, TEM, XPS, FTIR) were used to characterize both types of catalysts and to correlate the structure and the reactivity. The Lewis acidity of ZnO after the reduction treatment and the formation of PtZn alloy were found to be the key factors leading to high crotyl alcohol yield. It was proposed that modification of the electronic properties of platinum both by alloying to zinc and by Lewis acidity of the support reinforced by chlorine changes the adsorption mode of crotonaldehyde by favoring the binding of the terminal oxygen of the molecule to the electronically modified platinum atom.

Surface properties of unsupported MoS 2 have been studied by means of IR spectroscopy of a wide range of adsorbed molecules. After contact with air, surface of MoS 2 is partially oxidised and contains adsorbed water, MoO groups, sulphate and thiosulphate-like anions. These species are removable by treatment in vacuum or in H 2 S–H 2 mixture. On MoS 2 , only molecular adsorption was established for SO 2 , CO 2 , COS and CH 3 SH showing weak basicity of surface sulphur ions. Unsupported MoS 2 presents also very weak acidic properties, as revealed by pyridine, 2,6-dimethylpyridine and ethylene adsorption. However, ammonia could be protonated or coordinately bound to MoS 2 surface. CO and NO interact with the coordinately unsaturated Mo sites of the sulphide, providing evidence for an important back donation effect. Comparison with surface properties of supported MoS 2 points to the lower acidic and higher metallic character of Mo sites of the unsupported sulphide.

Le traitement d'une zeolithe NH 4 EMT par une solution de (NH 4 ) 2 SiF 6 fournit un solide comportant une phase SiO 2 amorphe intimement melangee aux parties intactes de la zeolithe. Sur ce support acide EMT-Si, on a greffe un sulfure de NiMo afin de preparer un catalyseur bifonctionnel qui a ete teste dans les reactions d'hydrogenation du benzene et d'hydrocraquage du n-heptane. Ce catalyseur NiMo/EMT-Si s'avere plus actif en hydrogenation que son analogue NiMo/HY, en raison d'une meilleure dispersion du sulfure de NiMo. Sur le solide EMT modifie, le sulfure se repartit a peu pres egalement entre les mesopores internes et les fissures crees dans les grains de zeolithe lors de l'insertion du sulfure de NiMo. Au contraire sur le support Y, une partie du sulfure est externe aux grains de zeolithe et inactive en catalyse. Le catalyseur NiMo/EMT-Si est aussi trouve plus actif que le NiMo/HY en hydrocraquage du n-heptane, et un peu plus selectif en isomeres.

Ozone (O3) adsorption on CeO2 pretreated under different conditions and characterized by low-temperature CO adsorption was studied by Fourier transform infrared (FTIR) spectroscopy at 77−300 K. Preliminary exposure to CO2, pyridine, acetonitrile, or methanol at 293 K or to CO at 77 K, as well as adsorption of 18O substituted O3 were used to clarify the nature of adsorption sites and the structure of the surface species. In addition to physisorption and weak H-bonding with the most acidic OH groups of the ceria surface, O3 forms coordinate complexes with two kinds of Lewis acid sites. These complexes have the bands of the ν1 and ν3 modes of O3 at 1096 and 1018−1015 cm-1, or 1104 and 1012−1008 cm-1, respectively. The coordinated O3 molecule is no longer symmetric but is bound to a surface Ce4+ ion via one of its terminal oxygen atoms. Basic surface sites of the samples pretreated at 773 K account for O3 decomposition, which occurs almost explosively at 77 K but could be inhibited if O3 adsorption is perform...

The lipase from the Antarctic psychrophilic bacterium Psychrobacter immobilis B10 shows a very limited thermal stability when compared to the lipase from a mesophilic strain of Pseudomonas aeruginosa . The thermal dependence of its activity is shifted by at least 30 °C towards low temperatures and its activation energy is reduced by a factor of 2. The three-dimensional model of the P. immobilis lipase reveals several features typical of cold-adapted enzymes: a very low proportion of arginine residues as compared to lysines, a low content in proline residues, a small hydrophobic core, a very small number of salt bridges and of aromatic-aromatic interactions. All these properties should confer on the enzyme a more flexible structure, in accord with its low activation energy and its low thermal stability.

Sous helium, le benzaldehyde se transforme selectivement en alcool benzylique par une reaction de type Cannizzaro. Les activites observees en debut de reaction dependent uniquement du nombre d'hydroxyles basiques forts initiaux et conduisent au classement suivant : a(MgO) » a(ZrO 2 ) > a(ZnO) O En presence de H 2 , la transformation de l'aldehyde benzylique en alcool benzylique est une reaction catalytique, elle peut etre decrite par deux schemas reactionnels en competition. Le premier necessite une dissociation reversible du dihydrogene et semble lie a la reductibilite de l'oxyde, le second prevoit la liberation de certains sites benzoates et la regeneration d'hydroxyles basiques forts. Le classement suivant les activites decroissantes presente precedemment est completement inverse: a(ZnO) » a(ZrO 2 ) > a(MgO) = 0.

Mastertool MT8 is a new dry phototool for the production of printed circuit boards, which represents a completely new technology. MT8 is not sensitive to daylight, is free of silver and inherently environmentally safe as the material does not contain any toxic ingradients, no processing chemicals are required and no waste arises. For imaging, the non‐transparent thin bismuth layer of MT8, embedded between polymers, is agglomerated into beads through IR laser radiation, making this area optically transparent. Light and electron microscopy as well as X‐ray diffractometry are used to characterise the composition of the material and the details of the recording processes. Based on finite element modelling, it was possible to interpret theoretically the experimentally determined dependence of the sensitivity on the recording speed. Understanding these material properties enables plotter optimisation for MT8.

Two zeolites were coked using cyclohexene at 620 K; one had a low Si/Alf ratio (HY), the other was ultrastabilized (HYS). It was found that oxygen regeneration occurred at 770 K or above, whereas ozone was effective at 450 K or less,e.g. under conditions such that the HY sample was still thermally stable.

Among its penicillin-binding proteins (PBPs), Enterococcus faecium possesses a low-affinity PBP5, PBP5fm, which is the main target involved in beta-lactam resistance. A 7.7-kb EcoRI chromosomal fragment of E. faecium D63r containing the pbp5fm gene was cloned and sequenced. Two open reading frames (ORFs) were found. A 2,037-bp ORF encoded the deduced 73.8-kDa PBP5fm, the amino acid sequences of which were, respectively, 99.8, 78.5, and 62% homologous to those of the low-affinity plasmid-encoded PBP3r of Enterococcus hirae S185r and the chromosome-encoded PBP5 of E. hirae R40 and Enterococcus faecalis 56R. A second 597-bp ORF, designated psrfm, was found 2.3 kb upstream of pbp5fm. It appeared to be 285 bp shorter than and 74% homologous with the regulatory gene psr of E. hirae ATCC 9790. Different clinical isolates of E. faecium, for which a wide range of benzylpenicillin MICs were observed, showed that the increases in MICs were related to two mechanisms. For some strains of intermediate resistance (MICs of 16 to 64 micrograms/ml), the increased level of resistance could be explained by the presence of larger quantities of PBP5fm which had an affinity for benzylpenicillin (second-order rate constant of protein acylation [k+2/K] values of 17 to 25 M(-1) s(-1)) that remained unchanged. For the two most highly resistant strains, EFM-1 (MIC, 90 micrograms/ml) and H80721 (MIC, 512 micrograms/ml), the resistance was related to different amino acid substitutions yielding very-low-affinity PBP5fm variants (k+2/K < or = 1.5 M(-1) s(-1)) which were synthesized in small quantities. More specifically, it appeared, with a three-dimensional model of the C-terminal domain of PBP5fm, that the substitutions of Met-485, located in the third position after the conserved SDN triad, by Thr in EFM-1 and by Ala in H80721 were the most likely cause of the decreasing affinity of PBP5fm observed in these strains.

Serine beta-lactamases contribute widely to the beta-lactam resistance phenomena. Unfortunately, the intimate details of their catalytic mechanism remain elusive and subject to some controversy even though many "natural" and "artificial" mutants of these different enzymes have been isolated. This paper is essentially focused on class C beta-lactamases, which contain a Tyr (Tyr150) as the first residue of the second conserved element, in contrast to their class A counterparts, in which a Ser is found in the corresponding position. We have modified this Tyr residue by site-directed mutagenesis. On the basis of the three-dimensional structure of the Enterobacter cloacae P99 enzyme, it seemed that residues Glu272 and His314 might also be important. They were similarly substituted. The modified enzymes were isolated and their catalytic properties determined. Our results indicated that His314 was not required for catalysis and that Glu272 did not play an important role in acylation but was involved to a small extent in the deacylation process. Conversely, Tyr150 was confirmed to be central for catalysis, at least with the best substrates. On the basis of a comparison of data obtained for several class C enzyme mutants and in agreement with recent structural data, we propose that the phenolate anion of Tyr150, in conjunction with the alkyl ammonium of Lys315, acts as the general base responsible for the activation of the active-site Ser64 during the acylation step and for the subsequent activation of a water molecule in the deacylation process. The evolution of the important superfamily of penicillin-recognizing enzymes is further discussed in the light of this proposed mechanism.

FT i.r. spectroscopy has been applied in studying the reaction between methanol and hydrogen sulfide on NaX and NaY zeolites. Hydrogen-bonded methanol and methoxy and carbonate species were found on both of the zeolites after methanol adsorption. Pyrrole and pyridine preadsorption experiments have shown that methanol is chemisorbed on basic and/or cationic sites on the zeolites used. H 2 S is adsorbed on the same sites. In the reaction between methanol and hydrogen sulfide on sodium zeolites methoxy species or HS − ions are involved. Carbonate species can also react with H 2 S producing hydrogenthiocarbonates or thiocarbonates. However, this reaction does not play any role in the interaction between CH 3 OH and H 2 S under the conditions used.

The catalytic properties of six "natural" mutants of the TEM-1 beta-lactamase have been studied in detail, with special emphasis on their activity versus third-generation cephalosporins. On the basis of the recently determined high-resolution structure of the wild-type enzyme, and of the substrates' structures optimized by the AMI quantum chemistry method, we have attempted to explain the influences of the mutations on the substrate profiles of the enzymes. Some of the kinetic results have thus received a satisfactory, semi-quantitative interpretation, especially in the case of single mutations. Analysis of the double mutants proved more hazardous. Extending the comparison to some other class A beta-lactamases showed that similar properties could result from different sequences, supplying an interesting example of convergent evolution within a generally diverging family.

Adsorption of CH3SH and CH3OH on activated NaX and NaY zeolites has been studied by IR spectroscopy. Only NaX is able to provoke the dissociative adsorption of CH3SH at room temperature and that of CH3OH at 623 K. Results are discussed taking into account sodium cations in the SIII position.

Poly(vinylidene difluoride) (PVDF) films were irradiated by means of heavy ions (in the electronic stopping-power range) and electrons. Both types of ionizing radiation induce in the polymer film ionizations and excitations, but swift heavy ions induce a huge density of excitations and ionizations along the ion path. Dose-range goes from 0.3 to 40 MGy. Irradiations were performed with Kr ions in the presence of helium, hydrogen, deuterium, and oxygen. FTIR transmission measurements show differences in the nature of the created defects. Triple bonds are characteristic of the Kr ion irradiation. Double bonds, isolated and conjugated, exist for both kinds of radiation, but concentrations are higher with the Kr radiation. The presence of oxygen during irradiation produces oxidization defects

Carbon monoxide hydrogenation over ceria-promoted Rh or Rh/SiO{sub 2} catalysts was investigated by means of Fourier transform infrared spectroscopy. In the chemisorption of CO at room temperature, a new absorption band was observed near 1,725 or 1,696 cm{sup {minus}1} on a reduced 5% Rh-5% CeO{sub 2}/SiO{sub 2} or 5% Rh/CeO{sub 2} catalyst, respectively. This new absorption band was attributed to a C- and O-bonded species, located at the metal/support interface. The appearance of this species was related to the shift to lower temperatures of the peak ascribed to CO dissociation in the temperature-programmed desorption spectra after CO adsorption. A flow high-pressure IR cell allowed to study the surface species in situ during CO + H{sub 2} reaction and to follow the reactivity of these species toward pure H{sub 2}. The results suggest that the drop in methane formation may be related to a lower reactivity of surface carbon in the presence of the promoter.

The reactivity towards O3 of the different species formed from phenol adsorption on silica and ceria has been studied using IR spectroscopy by increasing the temperature from 77 K. It clearly appeared that on silica H-bonded phenol species were more reactive than phenoxy species, whereas on ceria monodentate phenoxy species were more active than bidentate species. Intermediate products of phenol oxidation were characterized by bands between 1800 and 1600 cm−1, that at 1750 cm−1 being probably due to the formation of a carboxylic acid.

The "King Baby" is like a tyrant against his/her family with his/her refusing or requiring attitudes. This well known entity is analyzed in the actual social and familial context and compared with the similar situation in the countries with nutritional deficiencies. The impact of this relational problem on nutrition is detailed as especially weaning is concerned as well as the eventual consecutive and selective anorexia. A relational solution has been proposed: the "loving black-mailing" with early detection of "mothers or situations at risks".

The Poisson-Boltzmann method was used to compute the pK(a) values of titratable residues in a set of class C beta-lactamases. In these calculations, the pK(a) of the phenolic group of residue Tyr150 is the only one to stand out with an abnormally low value of 8.3, more than one pK(a) unit lower than the measured reference value for tyrosine in solution. Other important residues of the catalytic pocket, such as the conserved Lys67, Lys315, His314, and Glu272 (hydrogen-bonded to the ammonium group of Lys315), display normal protonation states at neutral pH. pK(a) values were also computed in catalytically impaired beta-lactamase mutants. Comparisons between the relative k(cat) values and the Tyr150 pK(a) value in these mutants revealed a striking correlation. In active enzymes, this pK(a) value is always lower than the solution reference value while it is close to normal in inactive enzymes. These results thus support the hypothesis that the phenolate form of Tyr150 is responsible for the activation of the nucleophilic serine. The possible roles of Lys67 and Lys315 during catalysis are also discussed.

The interest to the studies of the mechanism of organic molecule ozonolysis is based on the importance of these processes for medical and ecological problems, such as high ozone toxic action upon organisms, holes in atmospheric ozone layer, photochemical smog formation. Very often processes with the participation of ozone occur in heterogeneous systems, at the surface of aerosol particles or at interfaces of colloidal biological media. Earlier, investigations of ozonolysis mechanism were carried out mainly in solutions, gas phase or in low temperature matrices. Studies of ozone interaction with the adsorbed molecules, beside their scientific implications, enable us to apply spectroscopy for the identification of intermediate products and to follow the chain of reactions in a wide temperature interval, inaccessible for matrices or solutions. Molecules could be brought in contact at about 60 K or lower, with further monitoring of products until their decomposition or desorption. This technique with FTIR spectra measurements has already been tested by us and has demonstrated its advantages for ozonolysis of adsorbed ethylene [1] and phenol [2]. In this work it is expanded on the biological molecules, using thymine adsorbed on silica as an example.

The screening of the open reading frames identified in the whole yeast genome has allowed us to discover 34 proteins belonging to the mitochondrial carrier family. By phylogenetic study, they can be divided into 27 subfamilies including ADP/ATP, phosphate and citrate carriers, putative oxoglutarate and GDC carriers and 22 new subfamilies. Topology predictions using the 'positive inside rule' approach have shown that the yeast carriers are similarly oriented with both extremities exposed to the cytosol. In each subfamily, a strict conservation of the charged residues in the six transmembrane alpha-helices is observed, suggesting a functional role for these residues and the existence of 27 functionally distinct carriers.