Correlation of microcrack fracture size with fatigue cycling on non-crimp fabric/RTM6 composite in the uniaxial fatigue test

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

Evaluation of stitched fabric composite processed by RTM in quasi-static test

Stitched fabrics have been widely studied for potential application in aircraft structures since stitch yarns offer improvements in the out-of-plane mechanical properties and also can save time in the lay up process. The down side of stitch yarns came up in the manufacturing process of fabric in which defects introduced by the needle movement creating fiber-free-zones, fiber breakage and misalignment of fibers. The dry stitched carbon fabric preform has mainly been used in the Resin Transfer Molding (RTM) process which high fiber content is aimed, those defects influence negatively the injection behavior reducing the mechanical properties of final material. The purpose of this research work focused on testing in quasi-static mechanical mode (in-plane tension) of a monocomponent resin CYCOM (R) 890 RTM/carbon fiber anti-symmetric quadriaxial fabric stitched by PE 80Dtex yarn processed by RTM. The evaluation consisted in comparing the scatter of the quasi-static test with the attenuation of ultrasonic maps, which show the path of the resin and possible dry spots considering that interference of yarn in resin flow is detectable in ultrasonic measurement. Microscopic analysis was also considered for further evaluation in case of premature failure. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11

Behavioral responses evoked in honey bee workers by Dufour gland extracts (Hymenoptera : Apidae)

A series of experiments was performed to assess possible roles of the honey bee Dufour gland secretion. Bioassays with extracts of queen and worker glands from two colonies were made under artificial conditions, in which nestmate and non-nestmate forager workers were tested. The results demonstrate that forager workers display behavioral responses when exposed to Dufour gland extracts of nestmates, but remain indifferent when exposed to non-nestmate extracts. Also, the results demonstrate that forager workers are attracted by virgin queen gland extracts, and repelled by forager worker extracts. The data demonstrate that the Dufour gland secretion is colony- and caste-specific. The attractant remains in the nest. The repellent effect of forager worker extracts is interpreted as an alarm-like pheromone. The attractant effect of virgin queen extracts could be useful in the swarming process to attract scout bees to the eventual founder virgin queen or to attract old foragers to the virgin queen that remains in the nest.

Analysis of transient otoacoustic emissions and brainstem evoked auditory potentials in neonates with hyperbilirubinemia

A hiperbilirrubinemia é tóxica às vias auditivas e ao sistema nervoso central, deixando sequelas como surdez e encefalopatia. OBJETIVOS: avaliar a audição de neonatos portadores de hiperbilirrubinemia, utilizando-se a pesquisa das emissões otoacústicas evocadas transientes (EOAET) e dos potenciais evocados auditivos do tronco encefálico (PEATE). Estudo prospectivo. CASUÍSTICA E MÉTODOS: Constituíram-se dois grupos: GI (n-25), neonatos com hiperbilirrubinemia; GII (n-22), neonatos sem hiperbilirrubinemia e sem fatores de risco para surdez. Todos os neonatos tinham até 60 dias de vida e foram submetidos à EOAET e ao PEATE. RESULTADOS: 12 neonatos de GI e 10 de GII eram meninas e 13 de GI e 12 de GII eram meninos. As EOAET estavam presentes em todas as crianças, porém com amplitudes menores em GI, especialmente nas frequências de 2 e 3KHz (p < 0,05). No PEATE, observou-se discreto prolongamento de PV e de LI-V em GI. As alterações observadas nesses testes não se correlacionaram aos níveis séricos da bilirrubinemia. CONCLUSÕES: em neonatos portadores de hiperbilirrubinemia, menores amplitudes das EOAET e discreto prolongamento de PV e de LI-V foram constatados indicando comprometimento coclear e retrococlear das vias auditivas, salientando-se a importância da utilização e da interpretação minuciosa de ambos os testes nessas avaliações.

AMS and grain shape fabric of the Late Palaeozoic diamictites of the Southeastern Paran Basin, Brazil

Diamictites interbedded with marine shales and turbidites onlap the eastern border of the Parana Basin (Southern Brazil). These poorly sorted sediments were deposited during the Permo-Carboniferous glaciation, and their matrix-supported clasts show no preferred orientation. These massive rocks have been studied using anisotropy of magnetic susceptibility (AMS) and grain shape fabric. Hysteresis loops and thermomagnetic measurements show that AMS depends mostly on the paramagnetic clays, but fine ferromagnetic particles also contribute to the anisotropy. The coarse silt to sand grain preferred orientation study supports the use of AMS in describing the diamictite fabric, at least regarding the orientation of the foliation. AMS and grain shape data reveal subhorizontal to weakly inclined magnetic and grain shape foliation parallel to the regional bedding. The magnetic lineations are normally scattered within the foliation plane in agreement with the oblate AMS ellipsoids found in these rocks. Both fabric patterns are consistent with deposition by subaqueous mudflows that were resedimented downslope, with elastic supply from continental sources. The off-vertical grain shape foliation poles suggest that the deposition of diamictites was controlled by the depocentre topography of the Rio do Sul sub-basin.

Skin and pulmonary models using coated bentonite particles for the study of the inflammation evoked by Paracoccidioides brasiliensis antigens in previously immunized mice

Bentonite particles coated with polysaccharide antigen or crude soluble antigen of Paracoccidioides brasiliensis were injected intradermally or intravenously in mice. In control animals that were not pre-immunized with P. brasiliensis antigens, coated and uncoated bentonite caused minimal and nonspecific inflammation around the cutaneous injection site or around the bentonite thrombi in small lung vessels after intravenous injection. However, in mice previously immunized with P. brasiliensis antigens, the coated bentonite particles boosted the humoral and cellular immune responses to P. brasiliensis and evoked intense inflammatory reactions. Twelve days after intradermal injection, the inflammatory reaction around the bentonite was rich in neutrophils, macrophages, lymphocytes and plasma cells associated with young granulation tissue. In intravenously injected mice, the pulmonary inflammation was maximal at day 2, and was characterized by a florid neutrophilic and macrophagic cellular infiltration around bentonite thrombi; in some foci, there was incipient organization to mature granuloma. However, in both models, there was no formation of epithelioid granulomata, demonstrating that in paracoccidioidomycosis cellular immunity alone, without the presence of intact micro-organisms, may not be enough for the development of this type of granuloma.

Multimodal evoked potentials and the ovarian cycle in young ovulating women

There is controversy over how hormonal conditions influence cerebral physiology. We studied pattern-shift visual evoked potentials (PS-VEP), brain stem auditory evoked potentials (BAEP) and short-latency somatosensory evoked potentials (SSEV) in 20 female volunteers at different phases of the menstrual cycle (estrogen phase, ovulatory day and progesterone phase). Statistical analysis showed decreased latencies for P 100 (PS-VEP), N 19and P 22 (SSEV) waves in the progesterone phase compared with the estrogen phase. There was no significant difference between the estrogen and the ovulation day values. Comparing the three above stages, there were no significant differences in the brainstem auditory evoked potentials. The reduction of the latencies of the potentials generated in multisynaptic circuits provides the first consistent neurophysiological basis for a tentative comprehension of human pre-menstrual syndrome.

Effects of ethanol on human visual evoked potentials

Studies of the effect of ethanol on human visual evoked potentials are rare and usually involve chronic alcoholic patients. The effect of acute ethanol ingestion has seldom been investigated. We have studied the effect of acute alcoholic poisoning on pattern-reversal visual evoked potentials (PR-VEP) and flash light visual evoked potentials (F-VEP) in 20 normal volunteers. We observed different effects with ethanol: statistically significant prolonged latencies of F-VEP after ingestion, and no significant differences in the latencies of the PR-VEP components. We hypothesize a selective ethanol effect on the afferent transmission of rods, mainly dependent on GABA and glutamatergic neurotransmission, influencing F-VEP latencies, and no effect on cone afferent transmission, as alcohol doesn't influence PR-VEP latencies.

Catecholamine effects on human melanoma cells evoked by α1-adrenoceptors

The biological effects of catecholamines in mammalian pigment cells are poorly understood. Our previous results showed the presence of α1-adrenoceptors in SK-Mel 23 human melanoma cells. The aims of this work were to (1) characterize catecholamine effects on proliferation, tyrosinase activity and expression, (2) identify the α1- adrenoceptor subtypes, and (3) verify whether chronic norepinephrine (NE) treatment modified the types and/or pharmacological characteristics of adrenoceptors present in SK-Mel 23 human melanoma cells. Cells treated with the aradrenergic agonist, phenylephrine (PHE, 10-5 or 10-4 M), for 24-72 h, exhibited decreased cell proliferation and enhanced tyrosinase activity, but unaltered tyrosinase expression as compared with the control. The proliferation and tyrosinase activity responses were inhibited by the α1-adrenergic antagonist prazosin, suggesting they were evoked by α1-adrenoceptors. The presence of actinomycin D, a transcription inhibitor, did not diminish PHE-induced effects. RT-PCR assays, followed by cloning and sequencing, demonstrated the presence of α1A- and α1B-adrenoceptor subtypes. NE-treated cells (24 or 72 h) were used in competition assays, and showed no significant change in the competition curves of α1-adrenoceptors as compared with control curves. Other adrenoceptor subtypes were not identified in these cells, and NE pretreatment did not induce their expression. In conclusion, the activation of SK-Mel 23 human melanoma α1- radrenoceptors elicit biological effects, such as proliferation decrease and tyrosinase activity increase. Desensitization or expression of other adrenoceptor subtypes after chronic NE treatment were not observed.