Calcium modified lead titanate/poly-ether-ether-ketone composite for acoustic emission sensors

Composites made of calcium modified lead titanate ceramic powder and poly (ether-ether-ketone) high performance polymer matrix were prepared in the film form using a hot press. The acoustic and electromechanical properties of the composites have been determined using the ultrasonic immersion technique and piezoelectric spectroscopy, respectively. The composite film with 60 - 40 vol.% PTCa/PEEK was tested as acoustic emission detector. Preliminary results shown that the piezo composite can be used as sensor to evaluate the behavior of materials.

Evaluation of Decomposition Kinetics of Poly (Ether-Ether-Ketone) by Thermogravimetric Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Tricomas foliares em tomateiro com teores contrastantes do aleloquímico 2-tridecanona

Duas espécies de tomateiro, Lycopersicon esculentum Mill. (Linhagem TOM 556- padrão com baixo teor da metil cetona 2-tridecanona (2-TD) e Lycopersicon hirsutum Dunal var. glabratum Mill. (Linhagem PI 134417- padrão com elevado teor de 2-TD), foram analisadas em conjunto para identificação e quantificação de tricomas foliares. A parte experimental constou da identificação dos tricomas, baseado na presença ou ausência da cabeça secretora na extremidade apical dos tricomas, arranjo e número de células da cabeça, comprimento dos tricomas, e da quantificação do número de tricomas glandulares e não glandulares nos folíolos. O delineamento utilizado para o número de tricomas foi inteiramente casualizado e as médias comparadas pelo teste de Tukey, a 5%. A identificação e quantificação para as espécies foram: a) TOM 556: Tricomas não glandulares do tipo II + III + V (2590 cm-2 de área foliolar); glandular do tipo VI (16 cm-2); glandular do tipo VII (138 cm-2); b) PI 134417: não glandulares do tipo II + III + V (140 cm-2 de área foliolar); glandular do tipo I + IV (843 cm-2); glandular do tipo VI (83 cm-2); glandular do tipo VII (11 cm-2). As maiores concentrações da 2-TD nos folíolos, estão associadas às maiores densidades de tricomas glandulares presentes em ambas espécies.

Dielectric spectroscopy and thermally stimulated discharge current in PEEK film

A permissividade complexa de filmes de poli(eter-eter-cetona) (PEEK) foram investigados num grande intervalo de frequência. Não foram observados picos de relaxação no intervalo de frequência de 1,0 Hz a 10(5) Hz, mas no intervalo de baixa frequência (10-4 Hz) há uma evidência de pico, o qual também pode ser observado com medidas de corrente de despolarização termo-estimulada (TSDC). Este pico está relacionado com a transição vítrea do polímero. A energia de ativação relacionada a esta relaxação dipolar foi obtida e ovalor é Ea = 0,44 eV, que é similar à energia de ativação de muitos polímeros sintéticos. As cargas espaciais se mostraram importantes no mecanismo de condução como evidenciado nas medidas da corrente de despolarização.

Avaliações térmica e reológica da matriz termoplástica PEKK utilizada em compósitos aeronáuticos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Pyroelectric composite film for X-ray intensity detection

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Photopyroelectric response of PTCa/PEEK composite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Controle do fornecimento e da utilização de substratos energéticos no encéfalo

Correspondendo a apenas 2% do peso corpóreo, o cérebro apresenta taxa metabólica superior à maioria dos demais órgãos e sistemas. A maior parte do consumo energético encefálico ocorre no transporte iônico para manutenção do potencial de membrana celular. Praticamente desprovido de estoques, os substratos energéticos para o encéfalo são fornecidos necessariamente pela circulação sanguínea.O suprimento desses substratos sofre também a ação seletiva da barreira hemato-encefálica (BHE). O principal substrato, que é a glicose, tem uma demanda de 150 g/dia (0,7 mM/g/min). A metabolização intracelular parece ser controlada pela fosfofrutoquinase. A manose e os produtos intermediários do metabolismo (frutose 1,6 bifosfato, piruvato, lactato e acetato) podem substituir, em parte, a glicose, quando os níveis sangüíneos desta encontram-se elevados. Quando oxidado, o lactato chega a responder por 21% do consumo cerebral de Ov em situações de isquemia e inflamação infecciosa, o tecido cerebral passa de consumidor a produtor de lactato. Os corpos cetônicos também podem reduzir as necessidades cerebrais de glicose desde que oferecidos em quantidades suficientes ao encéfalo. Entretanto, devem ser considerados como um substrato complementar e nunca alternativo da glicose, pois comprometem a produção cerebral de succinil CoA e GTP. Quanto aos demais substratos, embora apresentem condições metabólicas, não existem demonstrações consistentes de que o cérebro produza energia a partir dos ácidos graxos sistêmicos, mesmo em situações de hipoglicemia. de maneira análoga, etanol e glicerol são considerados apenas a nível de experimentação. A utilização dos aminoácidos é dependente da sua captação, limitada tanto pela baixa concentração sangüínea, como pela seletividade da BHE. A maior captação ocorre para os de cadeia ramificada e destes, a valina. A menor captação é a de aminoácidos sintetizados no cérebro (aspartato,gluconato e alanina). Todos podem ser oxidados a CO, e H(2)0. Entretanto, mesmo com o consumo de glicose reduzido a 50%, a contribuição energética dos aminoácidos não ultrapassa 10%. Para manter o suprimento adequado de glicose e oxigênio, o fluxo sangüíneo cerebral é da ordem de 800 ml/min (15% do débito cardíaco). O consumo de O, pelo cérebro é equivalente a 20% do total consumido pelo corpo. Esses mecanismos, descritos como controladores da utilização de substratos energéticos pelo cérebro, sofrem a influência da idade apenas no período perinatal, com a oxidação do lactato na fase pré-latente e dos corpos cetônicos, no início da amamentação.

Processing of high performance composites based on peek by aqueous suspension prepregging

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ferroelectric ceramic/polymer composite for measuring X-ray intensity in the ortovoltage range

Pyroelectric sensors work as a thermal transducer converting the non-quantified thermal flux into the output measurable quantity of electrical charge, voltage or current. Ferroelectric ceramics and ferroelectric polymers have been extensively used as thermal detectors. More recently the research in the field of pyroelectricity has been concentrated on discovering materials with higher figures of merit (FOM), which means better sensing materials. Composite materials obtained with ferroelectric ceramics embedded in polymer host have received great attention because of their formability, mechanical resistance and the possibility to change their dielectric property varying the volume fraction of ceramic particles. In this work composite films made of modified lead titanate (PZ34) and poly(ether-ether-ketone) (PEEK) were characterized and used as sensing element to measure X-ray intensity in the ortovoltage range (120 - 300 kVp). The sensor response varies from 2.70 V to 0.80 V in the energy fluency range of 6.30 to 37.20 W/m(2). Furthermore the absorbed energy was analyzed as a function of the ionizing energy. The results indicate that the PZ34/PEEK composite with 60/40 vol.% can be useful to monitor X-ray radiation therapy.

Determination of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography with electrochemical detection

A new methodology was developed for analysis of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography (HPLC) coupled to electrochemical detection. The electrochemical oxidation of 5-hydroxymetkylfurfural, 2-furfuraldehyde, butyraldehyde, acetone and methyl ethyl ketone derivatized with 2,4-dinitrophenylhydrazine (DNPH) at glassy carbon electrode present a well defined wave at +0.94 V; +0.99 V; +1.29 V; +1.15 V and +1.18 V, respectively which are the basis for its determination on electrochemical defector. The carbonyl compounds derivatized were separated by a reverse-phase column under isocratic conditions with a mobile phase containing a binary mixture of methanol /LiClO4(aq) at a concentration of 1.0 x 10(-3) mol L-1 (80:20 v/v) and a flow-rate of 1.1 mL min(-1). The optimum potential for the electrochemical detection of aldehydes-DNPH and ketones-DNPH was +1.0 V vs. Ag/AgCl. The analytical curve of aldehydes-DNPH and ketones-DNPH presented linearity over the range 5.0 to 400.0 ng mL(-1), with detection limits of 1.7 to 2.0 ng mL(-1) and quantification limits from 5.0 to 6.2 ng mL(-1), using injection volume of 20 mu L. The proposed methodology was simple, low time-consuming (15 min/analysis) and presented analytical recovery higher than 95%.

Gaussian basis sets by generator coordinate Hartree-Fock method to ab initio calculations of electron affinities of enolates

The Generator Coordinate Hartree-Fock (GCHF) method is employed to generate uncontracted 15s and 18s11p gaussian basis sets for the H, C and O atoms, respectively. These basis sets are then contracted to 3s and 4s H atom and 6s5p, for C and O atoms by a standard procedure. For quality evaluation of contracted basis sets in molecular calculations, we have accomplished calculations of total and orbital energies in the Hartree-Fock-Roothaaii (HFR) approach for CH, C(2) and CO molecules. The results obtained with the uncontracted basis sets are compared with values obtained with the standard D95, 6-311G basis sets and with values reported in the literature. The 4s and 6s5p basis sets are enriched with polarization and diffuse functions for atoms of the parent neutral systems and of the enolates anions (cycloheptanone enolate, 2,5-dimethyleyelopentanone enolate, 4-heptanone enolate, and di-isopropyl ketone enolate) from the literature, in order to assess their performance in ab initio molecular calculations, and applied for calculations of electron affinities of the enolates. The calculations were performed at the DFT (BLYP and B3LYP) and HF levels and compared with the corresponding experimental values and with those obtained by using other 6-3 1 + +G((*)) and 6-311 + +G((*)) basis sets from literature. For the enolates studied, the differences between the electron affinities obtained with GCHF basis sets, at the B3LYP level, and the experimental values are -0.001, -0,014, -0.001, and -0.001 eV. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Linamarin - The toxic compound of cassava

Cassava is a widely grown root crop which accumulates two cyanogenic glucosides, linamarin and lotaustralin. Linamarin accounts for more than 80% of the cassava cyanogenic glucosides. It is a β-glucoside of acetone cyanohydrin and ethyl-methyl-ketone-cyanohydrin. Linamarin β-linkage can only be broken under high pressure, high temperature and use of mineral acids, while its enzymatic break occurs easily. Linamarase, an endogenous cassava enzyme, can break this β-linkage. The enzymatic reaction occurs under optimum conditions at 25°C, at pH 5.5 to 6.0. Linamarin is present in all parts of the cassava plant, being more concentrated on the root and leaves. If the enzyme and substrate are joined, a good detoxification can occur. All the cassava plant species are known to contain cyanide. Toxicity caused by free cyanide (CN-) has already been reported, while toxicity caused by glucoside has not. The lethal dose of CN- is 1 mg/kg of live weight; hence, cassava root classification into toxic and non-toxic depending on the amount of cyanide in the root. Should the cyanide content be high enough to exceed such a dose, the root is regarded as toxic. Values from 15 to 400 ppm (mg CN-/kg of fresh weight) of hydrocyanic acid in cassava roots have been mentioned in the literature. However, more frequent values in the interval 30 to 150 ppm have been observed. Processed cassava food consumed in Brazil is safe in regard to cyanide toxicity.

Aryltetralone lignans and 7,8-seco-lignans from Holostylis reniformis

Aryltetralone lignans and two 7,8-seco-lignans were isolated from the acetone and hexane extracts of the roots of Holostylis reniformis, together with (-)-galbacin. Their structures were determined by spectroscopic methods. © 2004 Elsevier Ltd. All rights reserved.

Hypochlorous acid inhibition by acetoacetate: Implications on neutrophil functions

Type-1 diabetic patients experience hyperketonemia caused by an increase in fatty acid metabolism. Thus, the aim of this study was to measure the effect of ketone bodies as suppressors of oxidizing species produced by stimulated neutrophils. Both acetoacetate and 3-hydroxybutyrate have suppressive effect on the respiratory burst measured by luminol-enhanced chemiluminescence. Through measurements of hypochlorous acid production, using neutrophils or the myeloperoxidase/H2O2/Cl- system, it was found that acetoacetate but not 3-hydroxybutyrate is able to inhibit the generation of this antimicrobial oxidant. The superoxide anion scavenging properties were confirmed by ferricytochrome C reduction and lucigenin-enhanced chemiluminescence assays. However, ketone bodies did not alter the rate of oxygen uptake by stimulated neutrophils, measured with an oxygen electrode. A strong inhibition of the expression of the cytokine IL-8 by cultured neutrophils was also observed; this is discussed with reference to the antioxidant-like property of acetoacetate. © 2004 Pharmaceutical Society of Japan.