Showing papers by "State University of Santa Cruz published in 2001"

Cyclohexane oxidation continues to be a challenge

Abstract: Many efforts have been made to develop new catalysts to oxidize cyclohexane under mild conditions. Herein, we review the most interesting systems for this process with different oxidants such as hydrogen peroxide, tert -butyl hydroperoxide and molecular oxygen. Using H 2 O 2 , Na-GeX has been shown to be a most stable and active catalyst. Mesoporous TS-1 and Ti-MCM-41 are also stable, but the use of other metals such as Cr, V, Fe and Mo leads to leaching of the metal. Homogeneous systems based on binuclear manganese(IV) complexes have also been shown to be interesting. When t -BuOOH is used, the active systems are those phthalocyanines based on Ru, Co and Cu and polyoxometalates of dinuclear ruthenium and palladium. Microporous metallosilicates containing different transition metals showed leaching of the metal during the reactions. Molecular oxygen can be used directly as an oxidant and decreases the leaching of active species in comparison to hydrogen peroxide and tert -butyl hydroperoxide. Metal aluminophosphates (metal: Mn, Fe, Co, Cu, Cr V) are active and relatively stable under such conditions. Mn-AlPO-36 yields directly adipic acid, but large amounts of carboxylic acids should be avoided, as they cause metal leaching from the catalysts. Rare earth exchanged zeolite Y also shows good selectivity and activity. In the last part of the review, novel alternative strategies for the production of cyclohexanol and cyclohexanone and the direct synthesis of adipic acid are discussed.

Phylogenetic Relationships Among Species of the fraterculus Group (Anastrepha: Diptera: Tephritidae) Inferred from DNA Sequences of Mitochondrial Cytochrome Oxidase I

Abstract: A fragment of 808 base pairs within the mtDNA gene cytochrome oxidase I (COI) was analyzed for 15 species of Anastrepha: 12 within the fraterculus group, one unplaced species and two outgroups. Phylogenetic relationships among the included taxa were inferred using neighbor-joining and maximum parsimony methods. The average Jukes-Cantor genetic distance among the species was 0.033±0.006 and the level of sequence divergence ranged from 0.0 to 0.083. Our results of COI indicate the placement of A. acris Stone, an unplaced species, in the fraterculus group. The membership of A. barbiellinii Lima in the fraterculus group and the monophyly of the aforementioned group are also discussed. Moreover, the presence of multiple gene pools in the nominal species A. fraterculus (Wiedemann) and the nonmonophyly of A. fraterculus are corroborated by data obtained in our study. The species A. amita Zucchi, A. turpiniae Stone and A. zenildae Zucchi were genetically studied for the first time.

Three-dimensional Magnetohydrodynamic Simulations of Radiatively Cooling, Pulsed Jets

Abstract: We here investigate, by means of fully three-dimensional smoothed particle magnetohydrodynamic numerical simulations, the effects of different initial magnetic field configurations on the evolution of overdense, radiatively cooling, pulsed jets using the following different initial magnetic field topologies: (1) longitudinal, (2) helical geometry permeating both the jet and the ambient medium, and (3) purely toroidal geometry permeating the jet only. We explore the effects of different pulsational periods, as well as different values of the magnetic field strength (? 0.1-? or B 260-0 ?G). The presence of a helical or toroidal field tends to affect the global characteristics of the fluid more than a longitudinal field. However, the relative differences that have been previously detected in two-dimensional simulations involving distinct magnetic field configurations are diminished in the three-dimensional flows. While the presence of toroidal magnetic components can modify the morphology close to the jet head, inhibiting its fragmentation in the early evolution of the jet, as previously reported in the literature, the impact of the pulse-induced internal knots causes the appearance of a clumpy, complex morphology at the jet head (as required by the observations of Herbig-Haro [HH] jets) even in the MHD jet models with helical or toroidal configurations. The detailed structure and emission properties of the internal working surfaces can also be significantly altered by the presence of magnetic fields. The increase of the magnetic field strength (decrease of ?) improves the jet collimation and amplifies the density (by factors up to 1.4 and 4) and the H? intensity (by factors up to 4 and 5) behind the knots of jets with a helical field and ? 1-0.1 relative to a nonmagnetic jet. As a consequence, the corresponding I[S II]/IH? ratio (which is frequently used to determine the excitation level of HH objects) can be decreased in the MHD models with toroidal components relative to nonmagnetic calculations by about the same amounts, although the intensity estimates above are very approximate. We also find that the helical mode of the Kelvin-Helmholtz instability can be triggered in MHD models with helical magnetic fields, causing some wiggling of the jet axis. No evidence for the formation of the nose cones that are commonly detected in two-dimensional jet simulations with initial toroidal magnetic fields is found in the three-dimensional flows or even in the ? 0.1 case. The implications of our results for HH jets are briefly discussed.

Catalytic activity and stability of a chromium containing silicate in liquid phase cyclohexane oxidation

Abstract: A chromium containing silicate has been prepared by an acid-catalyzed sol–gel process. The material was characterized by FTIR, UV–VIS and EPR spectroscopy as well as TPR, XRD and XRF analyses. The silicate is an efficient catalyst for the oxidation of cyclohexane with tert-butyl hydroperoxide. Leaching studies showed that catalysis is at least in part due to traces of Cr leached into the homogeneous phase. Weakly bound Cr species can be removed by soxhlet extraction, yielding a catalyst which is remarkably leaching resistant. The catalyst can be used at least four times without detectable loss of metal.

Influência da Temperatura Ambiente no Desempenho da Rã-touro, Rana catesbeiana (Shaw, 1802) na Fase de Recria

Abstract: Um experimento foi conduzido com o objetivo de avaliar o efeito da temperatura ambiente no desempenho da ra-touro na fase de recria. Foram utilizadas 405 ras com peso medio inicial de 37,5±1,5 g, em um delineamento experimental inteiramente casualizado tres tratamentos (20,2±0,7°C, 25,1±0,4°C e 30,4±0,5°C), cinco repeticoes (baias) e 27 ras por baia. O periodo experimental foi de 45 dias, sendo dez dias para adaptacao das ras as instalacoes e ao manejo alimentar. A alimentacao foi fornecida diariamente, sendo composta uma por racao comercial de truta com 45% de proteina bruta e larva de mosca, utilizada como atrativo. Avaliou-se o desempenho dos animais e concluiu-se que a temperatura afetou significativamente o consumo de racao e de larva de mosca e o ganho de peso das ras, porem os valores de conversao alimentar nao diferiram entre as ras nos tres tratamentos. O desenvolvimento da ra-touro esta diretamente relacionado com a temperatura ambiente, que influencia o consumo e a utilizacao do alimento pelos animais.

Herança da resistência à mancha-angular do feijoeiro e identificação de marcadores moleculares flanqueando o loco de resistência

Abstract: Angular leaf spot, caused by the fungus Phaeoisariopsis griseola, is one of the most important diseases affecting the common bean (Phaseolus vulgaris). Molecular markers linked to a few resistance genes have been identified, however, they are insufficient to monitor all the different sources of resistance. For this reason, in this work we aimed at studying the inheritance of resistance to P. griseola pathotypes 63.39 and 31.23 in populations derived from 'Ouro Negro' (ON) and 'US Pinto 111' (PT), and identifying molecular markers linked to the resistance loci present in these two cultivars. The genitor ON, F1 (ON x PT) and ¾ of the F2 population were resistant to pathotype 63.39. The genitor PT and ¼ of F2 plants were susceptible. When pathotype 31.23 was used, the genitor PT and ¼ of F2:3 families were resistant and all the other families were susceptible indicating that resistance of ON to pathotype 63.39 is conferred by a dominant gene while resistance of PT to pathotype 31.23 is conferred by a recessive gene. These two loci segregated independently. DNA samples extracted from F2 plants were amplified by the Random Amplified Polymorphic DNA (RAPD) technique and analyzed through the bulk segregant strategy. Two markers, OPM02460C and OPAA19600C, located at 5.3 and 10 centimorgans (cM) of the resistance locus, respectively, were identified in ON. These markers flank the resistance locus and their selection efficiency was 97.4% when used simultaneously. No markers were identified linked to the resistance locus present in PT.

Association of PCR and feeding bioassays as a large-scale method to screen tropical Bacillus thuringiensis isolates for a cry constitution with higher insecticidal effect against Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae.

Abstract: Aims: To verify whether the presence of any of the cry1C, 1D, 1E and 1F genes could be associated with high toxicity against fall armyworm. Methods and Results: A sample of 60 strains from a large collection of tropical Bacillus thuringiensis (B.t.) isolates was subjected to feeding bioassays and gene-specific PCR. Positive amplification of cry-specific fragments, so confirmed by sequencing, revealed that cry1C was ubiquitous and distributed among high and low mortality classes, cry1D was underrepresented and showed no clear association to high toxicity, and cry1F was not detected. The presence of cry1E significantly correlated to high levels of insecticidal activity, as estimated by linear regression analysis. Conclusions: The PCR amplification of cry1E-specific fragments alone appears to be sufficient to identify B.t. strains with high mortality levels against tropical armyworm. Significance and Impact of the Study: The approach presented is promising as a simple and efficient method for first-tier, marker-assisted screening of environment-specific B.t. germplasm effective in controlling a single target pest.

Detección de hongos Entomophthorales patógenos a insectos fitófagos, al sur de Bahia, Brasil

Abstract: Las investigaciones caracterizan el reconocimiento morfologico y taxonomico de los generos y especies asociados con Entomophthoromicosis, asi como, estudios enzooticos y epizooticos y sus interrelaciones con las poblaciones de insectos fitofagos sobre cultivos agricolas y pastos naturales al sur del estado de Bahia. Las investigaciones de campo tambien objetivan la distribucion y la incidencia natural de los Entomophthorales. El material biologico encontrado pasa por dos procesos laboratoriales: macro-, y microscopico. Los resultados parciales son animadores y muy promisores: todo indica que nos encontramos en la presencia de dos generos cosmopolitas de importancia agricola (Batkoa y Conidiobolus). Estudios mas detallados continuan en el laboratorio de Entomologia de la Universidad Estadual de Santa Cruz - UESC, en Ilheus, Bahia.

Weighted oscillator strengths and lifetimes for the Si II spectrum

Abstract: The weighted oscillator strengths ( gf ) and the lifetimes for Si X presented in this work were carried out in a multiconfiguration Hartree–Fock relativistic (HFR) approach. In this calculation, the electrostatic parameters were optimized by a least-squares procedure, in order to improve the adjustment to experimental energy levels. This method produces gf-values that are in better agreement with intensity observations and lifetime values that are closer to the experimental ones. In this work we presented all the experimentally known electric dipole Si X spectral lines.

3d 2 Configuration in six-times-ionized argon, Ar VII

Abstract: The transition array 2p63p3d–2p63d2 has been identified in the spectrum of magnesium-like Ar vii produced by electrical discharges in the vacuum-ultraviolet region. Twenty-five new transitions have been identified as combinations of levels of this transition array. From these transitions we have determined the levels of the 3d2 configuration. It was also possible to determine the 2p63p3d1D2o level that was missed in the early research with the Ar vii spectrum. Hartree–Fock calculations with relativistic corrections were used to predict energy levels and transitions. Isoelectronic comparisons along the Mg i sequence are used to support the experimental results.

The sievert: an enigmatic unit.

Abstract: The concept of effective dose with its unit, the sievert, is frequently misunderstood. Originally conceived to simplify radiation protection management, this concept is also proposed for another and very ambitions objective: a quantitative evaluation of the risks of radio-induced diseases, whatever the dose, the dose rate, the nature of radiation.... However, using the sievert for the prediction of risks of cancer or hereditary diseases is hazardous, and errors of prediction have been observed these last decades, for example the lack of prediction of the number of thyroid cancer in the very young children after the Chernobyl accident, and the overestimation of the risks such as leukaemia, other cancer and hereditary diseases. What are one sievert and its subunits?

A televisão na sala de aula: possibilidades e limites

Abstract: Este trabalho discute as possibilidades e os limites da televisao na sala de aula. A televisao e um dos meios de comunicacao mais frequente entre as pessoas e nos dife.rentes espacos, e a escola nao pode ficar segregada desse contexto, porque os professores e alunos sao espectadores da programacao televisiva que esta carregada de conteudos e na mixagem do som, cor e movimento a realidade e a imagem fundem-se no ensinar e aprender. Os alunos preferem programas que narram historias como as novelas, filme s, desenhos, minisseries, etc., porque possuem uma narrativa, acao e sequencia nas falas . Esses generos, porem quase nao sao utilizados na sala de aula, pelas limitacoes: tempo da hora/aula, ajuste do horario do programa com o horario da aula, etc. A critica a programacao deve ser feita, mas deve-se considerar o que pode ser acrescentado ao conhecimento dos alunos.

Evaluating empirical mathematical models to estimate leaf photosynthesis of tropical rain forest tree species

Abstract: The brazilian atlantic forest originally occupied an area of about 1.000.000 km 2 , extending along the brazilian coast from the state of Rio Grande do Norte to Rio Grande do Sul, and entering the continent from 100 to more than 200 km. Despite of the high original vegetation coverage, this biome is now between the most endangered forest biomes around world, with approximately 3% of the original forested area remaining intact. The southern region of the Bahia state has its socioeconomic history closely related to the culture of cacao (Theobroma cacao). Because cacao is a typical shade species and has long been cultivated in an agroforest system known as 'cabruca', in which the brazilian atlantic forest remainders are partially preserved (Araujo et al., 1998; Dean, 1998), the southern bahian forests

Palladium(II)‐Assisted Preparation of Methoxyarylbenzoquinones.

Abstract: The reaction of 2-methoxy-1,4-benzoquinone with methoxyphenolic derivative compounds obtained from wood tar constituents, assisted by palladium (II) acetate in acetic acid, allowed the preparation of five novel methoxyaryl-substituted 1,4-benzoquinones, as well as four structural isomer mixtures.