An Electrical Contacts Study for Tetrahedrite-Based Thermoelectric Generators

High electrical and thermal contact resistances can ruin a thermoelectric device's performance, and thus, the use of effective diffusion barriers and optimization of joining methods are crucial to implement them. In this work, the use of carbon as a Cu₁₁Mn₁Sb₄S₁₃ tetrahedrite diffusion barrier, and the effectiveness of different fixation techniques for the preparation of tetrahedrite/copper electrical contacts were investigated. Contacts were prepared using as jointing materials Ni and Ag conductive paints and resins, and a Zn-5wt% Al solder. Manual, cold- and hot-pressing fixation techniques were explored. The contact resistance was measured using a custom-made system based on the three points pulsed-current method. The legs interfaces (Cu/graphite/tetrahedrite) were investigated by optical and scanning electron microscopies, complemented with energy-dispersive X-ray spectroscopy, and X-ray diffraction. No interfacial phases were formed between the graphite and the tetrahedrite or Cu, pointing to graphite as a good diffusion barrier. Ag water-based paint was the best jointing material, but the use of hot pressing without jointing materials proves to be the most reliable technique, presenting the lowest contact resistance values. Computer simulations using the COMSOL software were performed to complement this study, indicating that high contact resistances strongly reduce the power output of thermoelectric devices.

Immuno-modulatory effects of nanoplastics and humic acids in the European seabass (Dicentrarchus labrax)

Pernicious effects of plastic particles, emergent contaminants worldwide, have been described in different species. In teleost species, alterations of immune function after exposure to nanoplastics (NPs) have been reported, but the interaction with cortisol - hypothalamic-pituitary-adrenal (HPI) axis has not yet been explored. Furthermore, the role of dissolved organic matter on the effects of NPs is poorly known. Thus, the aims of this research were to assess if polystyrene NPs (PSNPs) acted as a stressor on juvenile European seabass (Dicentrarchus labrax), interfering with the immune response, as well as to elucidate if humic acids (HA) modulated the potential effects of PSNPs. A short-term exposure to PSNPs and HA elicited an immuno-modulatory response, with an activation of steroidogenic stress-related pathways. An upregulation of anti-inflammatory cytokine (il10, tgfb) and stress-related (mc2r, gr1) transcripts were observed after exposure to HA and PSNPs both individually and in co-exposure. No notable alteration of inflammatory markers was consistently found, which may reflect a protective anti-inflammatory effect of HA in the presence of PSNPs. Nevertheless, there seems to be a more complex interaction between both components. Overall, data show that understanding the interaction of NPs with dissolved organic substances is key to deciphering their environmental risks.

Uranium Carbide Fibers with Nano-Grains as Starting Materials for ISOL Targets

This paper presents an experimental study about the preparation, by electrospinning, of uranium carbide fibers with nanometric grain size. Viscous solutions of cellulose acetate and uranyl salts (acetate, acetylacetonate, and formate) on acetic acid and 2,4-pentanedione, adjusted to three different polymer concentrations, 10, 12.5, and 15 weight %, were used for electrospinning. Good quality precursor fibers were obtained from solutions with a 15% cellulose acetate concentration, the best ones being produced from the uranyl acetate solution. As-spun precursor fibers were then decomposed by slow heating until 823 K under argon, resulting in a mixture of nano-grained UO₂ and C fibers. A last carboreduction was then carried out under vacuum at 2073 K for 2 h. The final material displayed UC_2−y as the major phase, with grain sizes in the 4 nm–10 nm range. UO_2+x was still present in moderate concentrations (~30 vol.%). This is due to uncomplete carboreduction that can be explained by the fiber morphology, limiting the effective contact between C and UO₂ grains.

Effects of nanoplastics on Mytilus galloprovincialis after individual and combined exposure with carbamazepine

Plastic pollution is a worldwide problem, highlighted by the fact that plastic materials degrade into nano-size particles (<100 nm), potentially becoming more bioavailable as well as a source of entry of other contaminants into organisms. The present study aimed to assess the effects of polystyrene nanoplastics (PS), individually or combined with carbamazepine (Cbz), on the Mediterranean mussel, Mytilus galloprovincialis. For this purpose, mussels were exposed for 96 h to a concentration range of PS (from 0.05 up to 50 mg L^-1), to Cbz (6.3 μg L^-1) alone and to the mixture of PS + Cbz (0.05 mg L^-1+ 6.3 μg L^-1). Molecular and biochemical biomarkers were assessed in the digestive glands, gills and haemolymph. The abundance of mRNA in the digestive glands and gills revealed significant alterations in the expression of genes associated with biotransformation, DNA repair, cell stress-response and innate immunity. Combined exposure of PS + Cbz induced significant downregulation in gene expression (e.g., hsp70) when compared to individual exposure. Total oxidant status increased in digestive glands after exposure to 0.5 mg L^-1 PS. Moreover, increased total antioxidant capacity and esterase activity were observed for PS 50 mg L^-1, in digestive glands and gills, respectively. The PS induced effects on neurotransmission, measured as inhibition of cholinesterase activity in haemolymph. Genotoxicity was found in haemocytes after exposure to PS, Cbz and their mixture. Moreover, lipid peroxidation was observed for 0.05 mg L^-1 PS exposure, showing that nanoplastics can induce oxidative damage. The present study demonstrated that PS, even at low concentrations, led to alterations on the assessed mussels' endpoints.

Effect of Ni, Bi and Se on the tetrahedrite formation

Tetrahedrite formation is influenced positively by selenium and negatively by bismuth and nickel. However, selenium decreases the skinnerite formation temperature.

Extracellular calcium triggers unique transcriptional programs and modulates staurosporine-induced cell death in Neurospora crassa

Alterations in the intracellular levels of calcium are a common response to cell death stimuli in animals and fungi and, particularly, in the Neurospora crassa response to staurosporine. We highlight the importance of the extracellular availability of Ca²⁺ for this response. Limitation of the ion in the culture medium further sensitizes cells to the drug and results in increased accumulation of reactive oxygen species (ROS). Conversely, an approximately 30-fold excess of external Ca²⁺ leads to increased drug tolerance and lower ROS generation. In line with this, distinct staurosporine-induced cytosolic Ca²⁺ signaling profiles were observed in the absence or presence of excessive external Ca²⁺. High-throughput RNA sequencing revealed that different concentrations of extracellular Ca²⁺ define distinct transcriptional programs. Our transcriptional profiling also pointed to two putative novel Ca²⁺-binding proteins, encoded by the NCU08524 and NCU06607 genes, and provides a reference dataset for future investigations on the role of Ca²⁺ in fungal biology.

HOLZ rings in EBSD patterns of the UFeB₄ compound: association with a random distribution of planar defects

The UFeB₄ phase present in different alloys of the B-Fe-U system was studied by powder X-ray diffraction (PXRD) and scanning electron microscopy complemented with energy-dispersive spectroscopy and electron backscattered diffraction (EBSD). The PXRD data showed that the ternary compound crystallized adopting essentially the YCrB₄-type structure. However, microstructural observations revealed that under high undercooling conditions the UFeB₄ phase exhibits a random distribution of defects parallel to, which are consistently associated with intense higher-order Laue zone rings in EBSD patterns. Indexation of the EBSD patterns showed that the defective structure is compatible with an intergrowth of YCrB₄- and ThMoB₄-type layers according to the (010)(YCrB₄)//(110)(ThMoB₄) and [001]YCrB₄//[001](ThMoB₄) orientation relation previously reported for an analogous compound. Magnetic studies indicated that the annealed UFeB₄ compound has a paramagnetic behavior in the 2-300 K temperature range.

Unusual 5f magnetism in the U2Fe3Ge ternary Laves phase: a single crystal study

Magnetic properties of the intermetallic compound U(2)Fe(3)Ge were studied on a single crystal. The compound crystallizes in the hexagonal Mg(2)Cu(3)Si structure, an ordered variant of the MgZn(2) Laves structure (C14). U(2)Fe(3)Ge displays ferromagnetic order below the Curie temperature T(C) = 55 K and presents an exception to the Hill rule, as the nearest inter-uranium distances do not exceed 3.2 Å. Magnetic moments lie in the basal plane of the hexagonal lattice, with the spontaneous magnetic moment M(s) = 1.0 μ(B)/f.u. at T = 2 K. No anisotropy within the basal plane is detected. In contrast to typical U-based intermetallics, U(2)Fe(3)Ge exhibits very low magnetic anisotropy, whose field does not exceed 10 T. The dominance of U in the magnetism of U(2)Fe(3)Ge is suggested by the (57)Fe Mössbauer spectroscopy study, which indicates very low or even zero Fe moments. Electronic structure calculations are in agreement with the observed easy-plane anisotropy but fail to explain the lack of an Fe contribution to the magnetism of U(2)Fe(3)Ge.

Electrical transport properties of CuS single crystals

Electrical resistivity, transverse magnetoresistance and thermoelectric power measurements were performed on CuS high quality single crystals in the range 1.2-300 K and under fields of up to 16 T. The zero field resistivity data are well described below 55 K by a quasi-2D model, consistent with a carrier confinement at lower temperatures, before the transition to the superconducting state. The transverse magnetoresistance develops mainly below 30 K and attains values as large as 470% for a 16 T field at 5 K, this behaviour being ascribed to a band effect mechanism, with a possible magnetic field induced DOS change at the Fermi level. The transverse magnetoresistance shows no signs of saturation, following a power law with field Δρ/ρ(0) ∝ H(1.4), suggesting the existence of open orbits for carriers at the Fermi surface. The thermoelectric power shows an unusual temperature dependence, probably as a result of the complex band structure of CuS.

Single-crystal study on the heavy-fermion antiferromagnet UZn₁₂

Millimetre size UZn(12) single crystals were grown by the high temperature solution growth method using zinc as the solvent. Single-crystal x-ray diffraction data confirm that this compound crystallizes in the hexagonal high temperature form of SmZn(12) (S.G. P6/mmm) and points to a U(1.01(1))Zn(11.7(1)) stoichiometry for the crystals, with ∼ 4% of the U atoms being located at the 2c site due to the partial substitution of 4h Zn pairs. UZn(12) orders antiferromagnetically at T(N) = 5.0(2) K, and the magnetization and resistivity measurements suggest that the magnetic moments are confined within the a-b plane. The Sommerfeld coefficient, derived from the paramagnetic region by the standard method, is γ(p)≈200 mJ (mol K(2))( - 1), which definitely classifies UZn(12) as a moderate heavy-fermion system. The heavy-fermion character of UZn(12) is also manifested in the overall shape of temperature-dependent electrical resistivity that is dominated by a single-ion Kondo effect at high temperatures and coherent Kondo scattering at low temperatures. The paramagnetic magnetoresistivity isotherms can be fairly well superimposed onto each other using Schlottmann's scaling for the single-ion Kondo model, as expected for a Kondo system.

The formation, structure and physical properties of M(2)Pd(14+x)B(5-y) compounds, with M = La, Ce, Pr, Nd, Sm, Eu, Gd, Lu and Th

Novel ternary compounds, M(2)Pd(14+x)B(5-y) (M =  La, Ce, Pr, Nd, Sm, Eu, Gd, Lu, Th; x∼0.9, y∼0.1), have been synthesized by arc melting. The crystal structures of Nd(2)Pd(14+x)B(5-y) and Th(2)Pd(14+x)B(5-y) were determined from x-ray single-crystal data and both are closely related to the structure type of Sc(4)Ni(29)B(10). All compounds were characterized by Rietveld analyses and found to be isotypic with the Nd(2)Pd(14+x)B(5-y) type. Measurements of the temperature dependent susceptibility and specific heat as well as the temperature and field dependent resistivity were employed to derive basic information on bulk properties of these compounds. The electrical resistivity of M(2)Pd(14+x)B(5-y), in general, is characterized by small RRR (residual resistance ratio) values originating from defects inherent to the crystal structure. Whereas the compounds based on Ce, Nd, Sm and Gd exhibit magnetic order, those based on Pr and Eu seem to be non-magnetic, at least down to 400 mK. While the non-magnetic ground state of the Pr based compound is a consequence of crystalline electric field effects in the context of the non-Kramers ion Pr, the lack of magnetic order in the case of the Eu based compound results from an intermediate valence state of the Eu ion.

Organic residues as immobilizing agents in aided phytostabilization: (II) effects on soil biochemical and ecotoxicological characteristics

Sewage sludge (SS), municipal solid waste compost, and garden waste compost (GWC) were used as immobilizing agents in aided phytostabilization of an acid metal-contaminated soil affected by mining activities. The organic residues were applied at 25, 50 and 100 Mg ha(-1) (dry weight basis) and perennial ryegrass (Lolium perenne L.) was used as a "green cover". We studied the effects of the treatments on soil phytotoxicity and enzymatic activities, and on the composition and toxicity of the soil leachate towards Vibrio fischeri and Daphnia magna. Application of SS led to the greatest values of dehydrogenase, acid phosphatase, beta-glucosidase, protease and urease activities, corresponding to the greatest overall microbial and biochemical activity in amended soils. Conversely, GWC did not increase these enzymatic activities, relative to the unamended soil, or enhance ryegrass growth. Cellulase activity increased with increasing application rates of the amendments tested, but decreased at the highest SS application rate. The organic amendments were able to suppress soil toxicity to levels that did not affect D. magna, when applied at 50 and 100 Mg ha(-1), but SS, at the same application rates, increased the soil leachate toxicity towards V. fischeri. Moreover, ryegrass showed some phytotoxic symptoms when 100 Mg ha(-1) of SS were applied. This study showed the importance of an integrated evaluation of soil quality on remediation processes. Although SS immobilized trace metals and corrected soil acidity, improving soil biochemical status, when used at high application rates it led to toxicity of soil leachate towards V. fischeri, decreased soil cellulase activity and impaired ryegrass growth.

Organic residues as immobilizing agents in aided phytostabilization: (I) effects on soil chemical characteristics

A greenhouse experiment was conducted to evaluate the effect of three different organic residues, sewage sludge (SS), municipal solid waste compost (MSWC), and garden waste compost (GWC), as immobilizing agents in aided phytostabilization of a highly acidic metal-contaminated soil, affected by mining activities, using perennial ryegrass (Lolium perenne L.). The organic residues were applied at 25, 50 and 100 Mg ha(-1) (dry weight basis), and their effects on soil chemical characteristics and on relative plant growth and metal concentrations were assessed. All the organic residues tested immobilized Cu, Pb and Zn, decreasing their mobile fractions. This was corroborated by negative correlations obtained between mobile Cu, Pb and Zn and other soil chemical characteristics, which rose as a consequence of the amendments applied (i.e., pH, electrical conductivity, organic matter, nitrogen content, available P and available K), and by the multivariate exploratory techniques performed that showed an inverse correlation between these groups of variables. The greatest increase in ryegrass relative growth (more than three times) was obtained in the presence of 50 MgMS WC ha(-1), followed by SS at the same application dosage. GWC did not contribute to an increase in shoot growth, due to its small capacity to correct soil acidity and to supply essential macronutrients (N, P, K). No extractant was able of demonstrating by a linear correlation the uptake of Cu, Pb and Zn by ryegrass. This plant was therefore not a good "indicator" of Cu, Pb and Zn availability in the soil. The results obtained in this study suggest that ryegrass can be used in aided phytostabilization for this type of mine contaminated soils and that MSWC, and to a minor extent SS, applied at 50Mg ha(-1), were effective in the in situ immobilization of metals, improving soil chemical properties and leading to a large increase in plant biomass.

Evaluation of composts and liming materials in the phytostabilization of a mine soil using perennial ryegrass

A microcosm experiment was carried out to evaluate the effects of municipal solid waste compost (MSWC) or garden waste compost (GWC), and liming materials in the rehabilitation of a soil affected by mining activities, and to study the use of perennial ryegrass (Lolium perenne L.) for phystostabilization. The performance of the amendments was assessed by soil chemical parameters, total and bioavailable metals (Cu, Pb and Zn), soil enzymatic activities, and plant relative growth and mineral composition. In general, both composts corrected soil acidity and increased the total organic matter content of the soil, although with a better performance in the case of MSWC, especially when considering total N and available P and K levels in the amended soil. The application of both composts and liming materials led to a decrease in the mobile fractions of Cu, Pb and Zn, but mobilisable fractions of Cu and Zn increased with MSWC application. Plant biomass increased more than three times in the presence of 50 Mg MSWC ha(-1) and with the combined use of 25 or 50 Mg MSWC ha(-1) and CaO, but no significant differences were observed when GWC was applied. Plant tissue analysis showed that the treatments did not significantly reduce Cu, Pb and Zn uptake by the plant. Dehydrogenase, and the enzymes related to the N-cycle, urease and protease, had increased activities with increasing MSWC application rate. Conversely, the enzymatic activities of both enzymes related to the C-cycle, cellulase and beta-glucosidase, were only positively affected by GWC application, a compost obtained from raw materials rich in C. Principal component analyses evidenced this clear separation between the effect of MSWC on soil enzymes related to the N-cycle and of GWC on soil enzymes related to the C-cycle. This study indicates that MSWC (50 Mg ha(-1), limed or unlimed) can be used successfully in the remediation of a highly acidic metal-contaminated soil, allowing the establishment of perennial ryegrass.

Assessment of chemical, biochemical and ecotoxicological aspects in a mine soil amended with sludge of either urban or industrial origin

A greenhouse pot experiment was conducted to evaluate the effect of sewage sludge (SS), of sugar beet sludge (SBS), or of a combination of both, in the remediation of a highly acidic (pH 3.6) metal-contaminated soil, affected by mining activities. The SS was applied at 100 and 200 Mg ha(-1) (dry weight basis), and the SBS at 7 Mg ha(-1). All pots were sown with Italian ryegrass (Lolium multiflorum Lam.). After 60 d of growth, shoot biomass was quantified and analysed for Cu, Pb and Zn. The pseudo-total and bioavailable contents of Cu, Pb and Zn and the enzymatic activities of beta-glucosidase, acid phosphatase, cellulase, protease and urease were determined in the soil mixtures. Two indirect acute bioassays with leachates from the soil (luminescent inhibition of Vibrio fischeri and Daphnia magna immobilization) were also used. The SS, in particular when in combination with SBS, corrected soil acidity, while increasing the total organic matter content and the cation exchange capacity. The application of SS led to a decrease in the level of effective bioavailable metals (extracted by 0.01 M CaCl(2), pH 5.7, without buffer), but caused an increase in their potential bioavailability (extracted by a solution of 0.5M NH(4)CH(3)COO, 0.5 M CH(3)COOH and 0.01 M EDTA, pH 4.7). Plant biomass increased more than 10 times in the presence of 100 Mg SS ha(-1), and more than five times with the combined use of 100 Mg SS ha(-1) and SBS, but a considerable phytotoxic effect was observed for the application rate of 200 Mg SS ha(-1). Copper, Pb and Zn concentrations in the shoots of L. multiflorum decreased significantly when using 100 Mg SS ha(-1) or SBS. The activities of beta-glucosidase, urease and protease increased with increasing SS applications rates, but cellulase had a reduced activity when using 200 Mg ha(-1)SS. Both amendments were able to suppress soil toxicity to levels that did not affect D. magna, but increased the soil leachate toxicity towards V. fischeri, especially with the application of 200 Mg SS ha(-1). This study showed that for this type of mine soils, and when using SS of similar composition, the maximum SS application rate should be 100 Mg ha(-1), and that liming the SS amended soil with SBS did not contribute to a further improvement in soil quality.

Evaluation of tests to assess the quality of mine-contaminated soils

An acid metal-contaminated soil from the Aljustrel mining area (a pyrite mine located in SW Portugal in the Iberian Pyrite Belt) was subjected to chemical characterisation and total metal quantification (Cd, Cr, Cu, Ni, Pb and Zn). Water-soluble metals were determined and a sequential extraction procedure was used to investigate metal speciation. Two bioavailable metal fractions were determined: a mobile fraction and a mobilisable fraction. Soil ecotoxicity was studied using a battery of bioassays: plant growth test and seed germination with cress (Lepidium sativum L.), earthworm (Eisenia fetida) mortality, E. fetida avoidance behaviour, luminescent inhibition of Vibrio fischeri and Daphnia magna immobilisation. Although the total content of Cu, Zn and Pb in the soil was large (362, 245 and 1,250 mg/kg dry matter, respectively), these metals were mostly structurally bound (87% for Cu, 81% for Zn and 89% for Pb) and, therefore, scarcely bioavailable. Nonetheless, the D. magna immobilization test using soil leachate showed an EC50 (48 h) of 36.3% (v/v), and the luminescent inhibition of V. fischeri presented an EC20 (15 min) of 45.2% and an EC20 (30 min) of 10.7% (v/v), suggesting a considerable toxic effect. In the direct exposure bioassays, E. fetida avoided the mine soil at the highest concentrations (50%, 75% and 100% v/v). At the same soil concentrations, cress showed negligible growth. The results suggest the need to use a battery of toxicity tests, in conjunction with chemical methods, in order to assess the quality of mine-contaminated soils correctly.

Evaluation of chemical and ecotoxicological characteristics of biodegradable organic residues for application to agricultural land

The use of organic waste and compost as a source of organic matter and nutrients is a common practice to improve soil physico-chemical properties, meanwhile reducing the need for inorganic fertilisers. Official guidelines to assess sewage sludge and compost quality are mostly based on total metal content of these residues. Measurement of the total concentration of metals may be useful as a general index of contamination, but provides inadequate or little information about their bioavailability, mobility or toxicity when the organic residue is applied to the soil. However, ecotoxicity tests provide an integrated measure of bioavailability and detrimental effects of contaminants in the ecosystem. In the present study, three different types of biodegradable organic residues (BORs) have been considered: sewage sludge from municipal wastewater treatment (SS), compost from the organic fraction of unsorted municipal solid waste (MSWC), and garden waste compost (GWC). The BORs were subjected to chemical characterisation and total metal quantification (Cd, Cr, Cu, Ni, Pb and Zn), in order to verify their suitability for land application. Water leachability was determined through the DIN 38414-S4 method, while the modified BCR sequential extraction procedure was used for metal speciation. Ecotoxicity of the BORs was studied by direct and indirect bioassays. Direct toxicity bioassays were: plant growth tests with cress (Lepidium sativum L.) and barley (Hordeum vulgare L.), and earthworm (Eisenia fetida) mortality. On the other hand, indirect exposure bioassays, with leachate from the residues, took into account: luminescent bacteria (Vibrio fischeri), seed germination (L. sativum and H. vulgare) and Daphnia magna immobilization. As far as total metal concentration is concerned, with particular reference to Zn, SS resulted neither suitable for the use in agriculture nor compatible to be disposed of as an inert material into landfill, according to the Directive 1999/31/EC. Zinc in SS was mainly present in exchangeable form (28.5%), appearing as highly bioavailable. As a consequence, SS exhibited either high ecotoxicity effects with the indirect exposure bioassays or significant mortality with the earthworm bioassay. Total content of metals in MSWC allowed its classification as "stabilised biowaste", according to 2nd draft [DG Env.A.2. Working document of Biological treatment of biowaste - 2nd draft. Directorate-General Environment, Brussels, 12th February; 2001. accessed in:http://europa.eu.int/comm/environment/waste/facts_en.htm, at 10/09/2002] while leachate, on the basis of the concentration of these contaminants, could be classified as "inert waste". This residue showed significant ecotoxicity effects with direct exposure bioassays as well as with the luminescent bacteria bioassay. However, it resulted less toxic than SS. Finally, GWC could be classified as a Class 2 compost, with no detectable toxic effects on the organisms used in the bioassays, except for the luminescent bacteria. In this case, an EC(50) of 73.0% was observed. Considering the results, the use of a battery of toxicity test in conjunction with chemical analysis should be suggested, in order to correctly assess possible environmental risks deriving from disposal or land application of biodegradable organic residues.

Frontal sinus adenocarcinoma

CONTEXT

Paranasal sinus cancer is considered rare, with an incidence of less than 1 per 100,000 per year, with the frontal sinus being the primary site in only 0.3%. We report a case of adenocarcinoma arising in the frontal sinus.

DESIGN

Case report.

CASE REPORT

A 59-year-old woman, secretary, came in February 1998 with a 4-month history of low intensity frontal headache. She denied contact with wood dust. On examination a non-tender swelling was noted over her right forehead next to the medial aspect of the right orbit. CT scan showed a soft-tissue mass involving frontal sinus with intracranial invasion through the posterior wall. The anterior ethmoid sinus and the medial aspect of the right orbit were also involved. MRI demonstrated dural thickening in communication with the frontal mass. She underwent an en-bloc tumor resection by craniotomy including orbital clearance. Histology revealed an adenocarcinoma. After surgery she had tumor recurrence, and chemotherapy and radiotherapy were started resulting in partial improvement.

Antigen heterogeneity among Mycoplasma mycoides subsp. mycoides SC isolates: discrimination of major surface proteins

The protein and antigen profiles of 60 isolates, strains and the type strain PG1 of Mycoplasma mycoides subsp. mycoides s.c. were compared by sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblot analysis. Analysis using contagious bovine pleuropneumonia antisera and hyperimmune rabbit sera against several representative strains revealed some differences in protein profiles and variability in antigens among strains from different geographic regions. The most common antigenic bands had the molecular masses of 110, 95, 80, 69, 62, 60, 48, 44, 39 and 38 kDa. There were differences among European strains, where a larger group coming from Italy lacked the p98 antigen, thus, with one exception, distinguishing the Italian strains from Portuguese, French and Spanish strains. African, Australian and PG1 strains showed heterogenic profiles, with quantitative differences and in a few strains some antigenic bands were absent. The group constituting African, Australian and PG1 strains was characterised by the presence of 71.5/70 kDa antigens, which were not detected in European strains. Mycoplasma mycoides subsp. mycoides s.c. membrane proteins were characterised by Triton X-114 partitioning and p110, p98, p95, p62/60 and p48 were identified as immunogenic antigens. The simultaneous presence of these five antigens was common to all the sera examined and, therefore, indicates the diagnostic potential of immunoblotting. Most immunodominant antigens are surface-exposed proteins as determined by the trypsin treatment.

Manifestation and epidemiology of contagious bovine pleuropneumonia in Europe

The authors describe the clinical profile and epidemiology of contagious bovine pleuropneumonia in Europe. This disease, once considered to have been eradicated several years ago, has now become endemic in southern countries of Europe. The status of contagious bovine pleuropneumonia in Portugal and Italy, and the evolution of the disease during the last ten years, are analysed in detail, in addition to the measures undertaken for control and eradication. The authors also refer to hosts and possible reservoirs of the infection.

Immobilization of a recombinant cutinase by entrapment and by covalent binding. Kinetic and stability studies

Fusarium solani pisi recombinant cutinase, immobilized by entrapment in calcium alginate and by covalent binding on porous silica, was used to catalyze the hydrolysis of tricaprylin. The influence of relevant parameters on the catalytic activity such as pH, temperature, and the substrate concentration were studied. Cutinase immobilized by entrapment presented a Michaelis-Menten kinetics for tricaprylin concentrations up to 200 mM. At higher concentrations of substrate, inhibition was observed. For covalent binding immobilization, diffusional limitations were observed at low substrate concentrations and substrate inhibition occurred for concentrations higher than 150 mM. The stability of immobilized cutinase was also evaluated. The enzyme immobilized by entrapment showed a high stability, in contrast to the immobilization on porous silica.

Biochemical characterization of an L-asparaginase bioconjugate

In this work is characterized a bioconjugate of L-asparaginase, obtained by linkage of palmitic acid chains to the native enzyme in the presence of substrate as a protein protective molecule. Comparisons between isoelectric points, hydrophobicity, pH, and temperature profiles for the bioconjugate and the native enzyme were performed. A shift of pI from 5.03 to 4.58 was observed after conjugation. The modified enzyme evidences a 10-fold increase of the hydrophobicity. A small shift from 7.5 to 7 of the pH for maximal catalytic activity and a 5 degree C increase of temperature for maximal activity were observed with conjugation. Stability studies in human serum and on storage evidence similar behaviors for both bioconjugate and native enzyme. The retention of catalytic activity of the bioconjugate is dependent on the presence of micelles. The bioconjugate evidenced 65% retention of activity when catalytic activity was assayed without a surfactant and 98-100% retention of activity when catalytic activity was assayed in the presence of surfactant micelles. The kinetic characteristics of the bioconjugate and of the native enzyme, in micelles of different hydrophobicities, were compared. The Michaelis constant of native enzyme is 0.030 mM, independent of the surfactant, and the Michaelis constant of the bioconjugate varies with the surfactant, from 0.036 to 0.046 mM.

Prevalence, biotypes, plasmid profile and antimicrobial resistance of Campylobacter isolated from wild and domestic animals from northeast Portugal

The incidence of Campylobacter jejuni and Campylobacter coli in wild and producing animals has been studied to evaluate their importance as potential reservoirs of campylobacter infection. These organisms were isolated from: 59 chicken (60.2%), 65 swine (59.1%), 31 black rats (57.4%), 61 sparrows (45.5%), 21 ducks (40.5%), 32 cows (19.5%) and 27 sheep (15.3%). Biotypes, plasmid and resistance profiles were studied in order to characterize the isolates. Biotypes I and II of C. jejuni were predominant in all reservoirs except swine, where C. coli I was more frequent. Plasmid prevalence was higher in strains isolated from swine (53.8%) and rats (45.5%). The size of the plasmids ranged from 1.3 to 82 MDa. A 2.3 MDa plasmid was the most frequent, detected in all the reservoirs except ducks. Antimicrobial susceptibility testing revealed that 5.5% of the strains were resistant to ampicillin, 5.5% to tetracycline, 12.6% to erythromycin and 23.5% to streptomycin. Resistance to erythromycin (26.2%) and to streptomycin (58.4%) was particularly high in isolates from swine. Tetracycline resistance was encoded by a 33 or a 41 MDa plasmid and transferred by conjugation.