998 resultados para cobalt carbide species


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Six species of trees located in the dry sclerophyll forests of southeast Queensland were studied to ascertain which was most suitable to be retained as hollow-bearing trees for nesting and denning by arboreal marsupials. Generally for all tree species, the number of entrances to hollows was positively correlated with the diameter at breast height (DBH) and the growth stage, and entrance diameters also increased in trees with a larger DBH. However, there were differences between the species; Corymbia citriodora had few hollows until the individuals were very large while Eucalyptus crebra had low numbers of hollows throughout its entire size range. It was concluded that a mixture of tree species provided a range of hollow sizes and positions that would be suitable for nesting and denning by arboreal marsupials in those forests. There were large differences between tree species in the relationship between tree size and estimated age. Five of the tree species took between 186 and 230 years to begin to produce hollows while E. crebra took up to 324 years. This suggests that tree species other than E. crebra may be the most preferred for retention in areas where hollow-bearing tree densities are lower than the prescribed level. Other data also suggests there are likely to be enough trees in larger size classes that would begin to form hollows within the next 50 years to compensate for an expected loss of hollow-bearing stags during that same period. In terms of forest operation, the retention of six hollow-bearing trees/ha would represent an estimated loss of 7.3-15% wood production. (C) 2003 Elsevier Science B.V. All rights reserved.

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This investigation aimed to elucidate the relative roles of putative brevetoxins, reactive oxygen species and free fatty acids as the toxic principle of the raphidophyte Chattonella marina, using damselfish as the bioassay. Our investigations on Australian C. marina demonstrated an absence or only very low concentrations of brevetoxin-like compounds by radio-receptor binding assay and liquid chromatography-mass spectroscopy techniques. Chattonella is unique in its ability to produce levels of reactive oxygen species 100 times higher than most other algal species. However, high levels of superoxide on their own were found not to cause fish mortalities. Lipid analysis revealed this raphidophyte to contain high concentrations of the polyunsaturated fatty acid eicosapentaenoic acid (EPA; 18-23% of fatty acids), which has demonstrated toxic properties to marine organisms. Using damselfish as a model organism, we demonstrated that the free fatty acid (FFA) form of EPA produced a mortality and fish behavioural response similar to fish exposed to C. marina cells. This effect was not apparent when fish were exposed to other lipid fractions including a triglyceride containing fish oil, docosahexaenoate-enriched ethyl ester, or pure brevetoxin standards. The presence of superoxide together with low concentrations of EPA accelerated fish mortality rate threefold. We conclude that the enhancement of ichthyotoxicity of EPA in the presence of superoxide can account for the high C. marina fish killing potential. (C) 2003 Elsevier B.V All rights reserved.

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Chiral resolution of the cobalt cage complexes [Co(diNOsar)](3+) and [Co(diAMsarH(2))](5+) have been achieved by selective crystallization with the anion bis-mu-(R),(R)-tartratodiantimonate(III) ([Sb-2(R,R-tart)(2)](2-)) and also by column chromatography with Na-2[Sb-2(R, R-tart)(2)] as eluent. The X-ray crystal structures of Lambda-[ Co(diNOsar)][Sb-2(R, R-tart)(2)] Cl . 7H(2)O and Delta-[Co(diAMsarH(2))][Sb-2(R, R-tart)(2)](2)Cl . 14H(2)O are reported, which reveal an unexpected reversal of chiral discrimination when the cage substituent is changed from nitro (Lambda-enantiomer) to ammonio (Delta-enantiomer) and shows that the ammonio- substituted cage is capable of forming a three-point hydrogen-bonding interaction with each complex anion, whereas the nitro analogue can only form two hydrogen bonds with each [Sb-2(R, R-tart)(2)](2-) anion. During cation exchange chromatography of the racemic cobalt cage complexes with Na-2[Sb-2(R, R-tart)(2)] as eluent, Lambda-[Co(diNOsar)](3+) elutes first, which implies a tighter ion pairing interaction than for the Delta-enantiomer. On the other hand, Delta-[Co(diAMsarH(2))](5+) elutes first during chromatography under identical conditions, which is also consistent with a preferred outer-sphere complex formed between Delta-[Co(diAMsarH(2))](5+) and [Sb-2(R, R-tart)(2)](2-) relative to Lambda-[Co(diAMsarH(2))](5+) and [Sb-2(R,R-tart)(2)](2-).

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The crystal structures of a pair of cis and trans isomers of the macrocyclic chloropentaamine title complex, as their tetrachlorozincate(II) salts, [CoCl(C11H27N5)][ZnCl4], are reported. The two distinct isomeric forms lead to significant variations in the Co-N bond lengths and, furthermore, hydrogen bonding between the complex ions is influenced by the folded (cis) or planar (trans) conformations of the coordinated ligand.

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The major trans (1) and minor cis (2) isomers of 1,4,8,11-tetraazacyclotetradecane-6,13-dicarboxylate have been characterized as the complexes [Co(1)](ClO4) and [Co(H-2)(OH2)]Cl(ClO4).H2O. The former crystallized in the C-2/c space group and the latter in the P2(1)/c space group, with cell parameters a 16.258(7), b 9.050(3), c 15.413(6) Angstrom, beta133.29(3)degrees, and a 9.694(4), b 16.135(1), c 12.973(5) Angstrom, beta 93.00(2)degrees, respectively. Their characterization completes identification of the respective trans and cis isomers for the series of C-pendant macrocycles also including 1,4,8,11-tetraazacyclotetradecane-6-amine-13-carboxylate ((3), (4)) and 1,4,8,11-tetraazacyclotetradecane-6,13-diamine ((5), (6)). The complexes show limited distortion from octahedral geometry with the strain in the presence of the coordinated C-pendant carboxylate significantly reduced compared with that for the C-pendant amine in analogues, a consequence mainly of six-membered as opposed to five-membered chelate rings involving the pendant donor. A comparison of the physical properties for the trans isomers of the octahedral complexes of (1), (3), and (5), which reflect progressively increasing strain, is presented.

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Reportamos atividades de pesca comerciais no complexo insular mais afastado da costa brasileira: Ilha da Trindade e Arquipélago Martin Vaz. As atividades foram estudadas através de embarques e entrevistas com os mestres e pescadores das embarcações durante uma expedição cientifica realizada entre fevereiro e abril de 2007. Quatro modalidades de atividades de pesca são realizadas na região, capturando ao menos sete espécies que possuem algum risco de extinção. O estabelecimento de normas específicas de restrição para atividades que pescam sobre os recifes das ilhas é uma alternativa para a conservação das espécies ameaçadas. O monitoramento das embarcações pode ocorrer via satélite através do programa nacional de rastreamento de embarcações pesqueiras (PREPS).

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Trabalho apresentado no I Simpósio Mineiro de Ciências dos Materiais, Ouro Preto, Novembro de 2001.

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Espécies do gênero Neotropical Alongatepyris Azevedo são raramente coletadas. O gênero é reconhecido dentre os Sclerodermini por possuir o corpo extremamente achatado e a célula submediana da asa anterior pequena e completamente fechada. É descrita e ilustrada uma segunda espécie, Alongatepyris ingens sp. nov. da Colômbia. Esta espécie é caracterizada por não possuir a nervura radial da asa anterior. É apresentada uma diagnose de A. platunissimus Azevedo, 1992. É apresentada uma chave para as espécies do gênero.

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Atualmente é difícil reconhecer a identidade de muitas espécies neotropicais de Pseudisobrachium Kieffer, 1904, principalmente por que as descrições e ilustrações disponíveis não são suficientes para permitir identificações precisas. Para resolver este problema, foram examinadas 115 espécies válidas, além de seus sinônimos juniores. Foram realizados doze atos nomenclaturais, e reconhecidas 110 espécies válidas para a região Neotropical. Foram designados dois lectótipos: Pristocera crassicornis Westwood and Pristocera haemorrhoidalis Westwood. Foram propostas sete sinonímias novas para espécies: Pseudisobrachium retusum Evans syn. nov. de P. pauxillum Evans; P. cunco Perez syn. nov. de P. erythrocephalum Evans; P. navajo Evans, P. rectangulatum Evans, P. emarginatum Evans e P. foutsi Evans syn. nov. de P. flavinervis Fouts; P. acuminatum Waichert & Azevedo syn. nov. de P. latum Waichert & Azevedo. Foi proposta a seguinte sinonímia nova para gênero: Parisobrachium Kieffer syn. nov. de Dissomphalus Ashmead. Foi estabelecida a seguinte combinação nova e revalidado o nome: Dissomphalus albipes (Kieffer) comb. nov. e nom. rev. de Pseudisobrachium paraguayense Kieffer.

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Solepyris Azevedo é um gênero neotropical raramente coletado. O gênero é reconhecido dentre os gêneros de Sclerodermini por possuir a nervação das asas anteriores com apenas uma célula fechada grande. É descrita e ilustrada uma segunda espécie, Solepyris montuosus, sp. nov., do Brasil. Esta espécie é caracterizada por possuir a nervura radial da asa anterior longa. É incluída uma diagnose emendada de Solepyris unicus Azevedo. Foi fornecida uma chave para as duas espécies de Solepyris.

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Ten new species of Apenesia Westwood, 1874, from Brazil, Acre, are described and illustrated. They belong, respectively, to the following species-groups: nitida group, Apenesia lobata sp. nov., A. serrulata sp. nov. and A. subangulata sp. nov.; laevigata group, A. ocullata sp. nov. and A. rostrum sp. nov.; columbana group, A. apicilata sp. nov.; mexicana group, A. triapicalis sp. nov.; brasiliensis group, A. megaventris sp. nov., A. ventosa sp. nov. and A. triangula sp. nov. New geographical records and some morphological data on A. funebris Evans, 1963, A. nitida (Kieffer, 1910) and A. truncaticeps (Kieffer, 1910) are added.

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Bakeriella lata sp. nov. (Brazil, Rondônia), Bakeriella aurata sp. nov. (Brazil, Amazonas) and Bakeriella sulcaticeps sp. nov. (Brazil, Amazonas) are described and illustrated. New geographic records and variation data for B. cristata Evans, 1964, B. floridana Evans, 1964, B. flavicornis Kieffer, 1910, B. incompleta Azevedo, 1994, B. mira Evans, 1997, B. montivaga (Kieffer, 1910), B. olmeca Evans, 1964 and B. subcarinata Evans, 1965 are provided. The male of B. incompleta is described for the first time.

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Five new species of Dissomphalus Ashmead, 1893 are described and illustrated, all from Espírito Santo, Brazil: D. h-ramus, D. verrucosus, D. laminaris, D. cristatus and D. scopatus. New geographic records and variation data of D. scamatus Azevedo, 1999, D. concavatus Azevedo, 1999, D. rectilineus Azevedo, 1999, D. vallensis Evans, 1979, D. gilvipes Evans, 1979, D. plaumanni Evans, 1964, D. napo Evans, 1979, D. truncatus Azevedo, 2003 and D. cornutus Evans, 1964 are included.

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The objectives of this study were to identify anthophilous butterflies on psychophilous flowers of four Asteraceae species in an Atlantic Forest fragment in Viçosa, Minas Gerais State, Southeastern Brazil, and to determine whether there are species in common with other lepidopteran inventories of the Southeastern and Midwestern regions of Brazil. It is the first inventory of anthophilous butterflies of a semideciduous forest fragment in Zona da Mata, State of Minas Gerais. A total of 108 species were recorded, representing the fourth largest lepidopteran survey in this State. The results demonstrated that Asteraceae species may be important tools for monitoring anthophilous butterflies. The similarity with other inventories ranged from 1 to 92.55%. Fifteen species were reported for the first time in the State of Minas Gerais, and among them, Melanis alena and Thisbe irenea were observed in this study only.