Thermal tunability of photonic bandgaps in photonic crystal fibers selectively filled with nematic liquid crystal

We address the bandgap effect and the thermo-optical response of high-index liquid crystal (LC) infiltrated in photonic crystal fibers (PCF) and in hybrid photonic crystal fibers (HPCF). The PCF and HPCF consist of solid-core microstructured optical fibers with hexagonal lattice of air-holes or holes filled with LC. The HPCF is built from the PCF design by changing its cladding microstructure only in a horizontal central line by including large holes filled with high-index material. The HPCF supports propagating optical modes by two physical effects: the modified total internal reflection (mTIR) and the photonic bandgap (PBG). Nevertheless conventional PCF propagates light by the mTIR effect if holes are filled with low refractive index material or by the bandgap effect if the microstructure of holes is filled with high refractive-index material. The presence of a line of holes with high-index LC determines that low-loss optical propagation only occurs on the bandgap condition. The considered nematic liquid crystal E7 is an anisotropic uniaxial media with large thermo-optic coefficient; consequently temperature changes cause remarkable shifts in the transmission spectrums allowing thermal tunability of the bandgaps. Photonic bandgap guidance and thermally induced changes in the transmission spectrum were numerically investigated by using a computational program based on the beam propagation method. © 2010 SPIE.

Morphological and molecular analysis of the collagen fibers in inflammatory process

Collagen makes up one third of the total protein in humans, being formed by the connection of three polypeptide chains arranged in a triple helix. This protein has fundamental importance in the formation of extracellular matrix of connective tissue. This study aimed to analyze the structural changes of collagen, which are resulting from inflammatory processes in oral mucosa, and to make the comparative analysis between the histopathology and the Raman spectra. The samples of tissues with inflammatory fibrous hyperplasia (IFH) and normal mucosa (NM) were evaluated by Raman Spectroscopy, hematoxylin-eosin and Massons trichrome stain. The histological analysis in both stains showed differences in collagen fibers, which was presented as thin fibers and arranged in parallel direction in NM and as collagen fibers are thick, mature and not organized, showing that these types of stain show morphological changes of collagen in IFH. The Raman Spectroscopy discriminate the groups of NM and IFH based on vibrational modes of proline, hydroxiproline and CH3, CH2. The histological stains only shows information from morphological data, and can be complemented by Raman spectra. This technique could demonstrate that inflammatory process caused some changes in collagen structure which is related to aminoacids such as proline and hidroxyproline. © 2011 SPIE-OSA.

Histochemical and ultrastructural analysis of hepatic glycogen and collagen fibers in alloxan-induced diabetic rats submitted to long-term physical training

Alterations in liver functions are common among diabetic patients, and many symptoms in the liver have been reported, including changes in glycogen stores and in the amount of collagen fibers. The practice of physical training and its morphological effects in this organ, however, are scarcely studied. In order to observe the morphological effects of alloxan-induced diabetes and the alterations arising from the practice of long-term chronic physical training in the liver, samples were collected and processed, and then analyzed by means of the histochemical techniques Periodic Acid-Schiff and Picrosirius-Hematoxylin, and ultrastructural cytochemical test of Afzelius. Through evaluation of the tissue, it was observed a drastic reduction in hepatic glycogen stores of sedentary diabetics, recovered in trained diabetic rats. Furthermore, it was detected a decrease in the content of perisinusoidal collagen fibers in the diabetic liver, also recovered due to the development of a training protocol. On ultrastructural level, cytochemical analysis confirmed the loss of glycogen and the recovery obtained by training. In conclusion, the practice of a long-term chronic physical training protocol may be considered an important assistant in the treatment of diabetes, mitigating the occurrence of possible damages to liver tissue. © 2011 Elsevier Ltd.

Influence of enclosure size on growth of breast and leg muscle fibers in domestic fowl

This experiment evaluated the growth of breast and leg muscle fibers of domestic fowl raised in two enclosure sizes (SE: Small Enclosure, 1.125 m2/10 birds; LE: Large Enclosure, 5.25 m2/10 birds). In breast muscles, the number of fibers per area decreased over time and higher values were observed in broilers housed in SE compared to LE. The fiber size increased with age and was greater in LE than SE at 56 days of age, suggesting greater hypertrophic growth of fibers in breast muscle for broilers maintained in LE. In leg muscles, the muscle cross-sectional area was greater for broilers raised in LE than SE at 56 days of age and decreased from 42 to 56 days of age in broilers raised in SE, suggesting leg muscle atrophy in these birds. The Fast Glycolytic (FG), Fast Oxidative-Glycolytic (FOG) and Slow Oxidative (SO) fibers grew until 42 days of age in both enclosure sizes. The area of FOG fibers was greater in broilers raised in LE than those in SE at 28 and 56 days of age; in LE-raised broilers, the SO area was greater at 28, 42 and 56 days of age, suggesting that the muscles of broilers housed in LE are more oxidative. The BW gain was greater for broilers raised in LE than SE, whereas BW, feed intake and feed conversion were not influenced by enclosure size. Thus, the enclosure space affected hypertrophic growth and metabolic characteristics of breast and leg muscle fibers. © Asian Network for Scientific Information, 2012.

Atmospheric plasma treatment of carbon fibers for enhancement of their adhesion properties

Plasma processing of carbon fibers (CFs) is aimed to provide better contact and adhesion between individual plies without decrease in the CF mechanical resistance. This paper deals with surface modification of CFs by an atmospheric pressure dielectric barrier discharge (DBD) for enhancing the adhesion between the CF and the polymeric matrix. The scanning electron microscopy of the treated samples revealed many small particles distributed over entire surface of the fiber. These particles are product of the fiber surface etching during the DBD treatment that removes the epoxy layer covering as-received samples. The alteration of the CF surface morphology was also confirmed by the Atomic force microscopy (AFM), which indicated that the CF roughness increased as a result of the plasma treatment. The analysis of the surface chemical composition provided by X-ray photoelectron spectroscopy showed that oxygen and nitrogen atoms are incorporated onto the surface. The polar oxygen groups formed on the surface lead to the increasing of the CF surface energy. The results of interlaminar shear strength test (short beam) of CFs/polypropylene composites demonstrated a greater shear resistance of the composites made with CFs treated by DBD than the one with untreated fibers. Both the increase in surface roughness and the surface oxidation contribute for the enhancement of CF adhesion properties. © 2012 IEEE.

Involvement of central cholinergic mechanisms on sodium intake induced by gabaergic activation of the lateral parabrachial nucleus

Bilateral injections of the GABAA agonist muscimol into the lateral parabrachial nucleus (LPBN) disrupt satiety and induce strong ingestion of water and 0.3M NaCl in fluid-replete rats by mechanisms not completely clear. In the present study, we investigated the effects of the blockade of central muscarinic cholinergic receptors with atropine injected intracerebroventricularly (i.c.v.) on 0.3M NaCl and water intake induced by muscimol injections into the LPBN in fluid-replete rats. Male Holtzman rats with stainless steel cannulas implanted bilaterally into the LPBN and unilaterally into the lateral ventricle (LV) were used. Bilateral injections of muscimol (0.5nmol/0.2μL) into the LPBN induced 0.3M NaCl (32.2±9.9mL/4h, vs. saline: 0.4±0.2mL/4h) and water intake (11.4±4.4mL/4h, vs. saline: 0.8±0.4mL/4h) in fluid-replete rats previously treated with i.c.v. injection of saline. The previous i.c.v. injection of atropine (20nmol/1μL) reduced the effects of LPBN-muscimol on 0.3M NaCl (13.5±5.0mL/4h) and water intake (2.9±1.6mL/4h). The i.c.v. injection of atropine did not affect 0.3M NaCl (26.8±6.2mL/2h, vs. saline i.c.v.: 36.5±9.8mL/2h) or water intake (14.4±2.5mL/2h, vs. saline i.c.v.: 15.6±4.8mL/2h) in rats treated with furosemide+captopril subcutaneously combined with bilateral injections of moxonidine (α2-adrenoceptor/imidazoline agonist, 0.5nmol/0.2μL) into the LPBN, suggesting that the effect of atropine was not due to non-specific inhibition of ingestive behaviors. The results show that active central cholinergic mechanisms are necessary for the hypertonic NaCl and water intake induced by the blockade of the inhibitory mechanisms with injections of muscimol into the LPBN in fluid-replete rats. The suggestion is that in fluid-replete rats the action of LPBN mechanisms inhibits facilitatory signals produced by the activity of central cholinergic mechanisms to maintain satiety. © 2012 Elsevier B.V.

Dielectric behavior of epoxy/BaTiO3 composites using nanostructured ceramic fibers obtained by electrospinning

Composite materials made of epoxy resin and barium titanate (BT) electrospun nanostructured fibers were prepared. BT fibers were synthesized from a sol based on barium acetate, titanium isopropoxide, and poly(vinyl pyrrolidone). The fibers were heat-treated at different temperatures and characterized by X-ray diffraction, scanning electron microscopy (SEM), and Raman spectroscopy. Mats of BT fibers heat-treated at 800 C were embedded in epoxy resin into suitable molds. The composites were characterized by SEM, and dielectric measurements were performed by means of dielectric spectroscopy. The dielectric permittivity and dielectric modulus of epoxy resin/BT-fiber composites were measured for two types of samples: with the electrodes parallel and perpendicular to the BT fiber layers. Interestingly, composite samples with electrodes perpendicular to the fiber layers and a BT content as low as 2 vol % led to dielectric permittivities three times higher than that of pure epoxy resin. © 2013 American Chemical Society.

Characterization of high density polyethylene (HDPE) reinforced with banana peel fibers

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

The Edinger-Westphal nucleus II: Hypothalamic afferents in the rat

Numerous functions have been attributed to the Edinger-Westphal nucleus (EW), including those related to feeding behavior, pain control, alcohol consumption and the stress response. The EW is thought to consist of two parts: one controls accommodation, choroidal blood flow and pupillary constriction, primarily comprising cholinergic cells and projecting to the ciliary ganglion; and the other would be involved in the non-ocular functions mentioned above, comprising peptide-producing neurons and projecting to the brainstem, spinal cord and prosencephalic regions. Despite the fact that the EW is well known, its connections have yet to be described in detail. The aim of this work was to produce a map of the hypothalamic sources of afferents to the EW in the rat. We injected the retrograde tracer Fluoro-Gold into the EW, and using biotinylated dextran amine, injected into afferent sources as the anterograde control. We found retrogradely labeled cells in the following regions: subfornical organ, paraventricular hypothalamic nucleus, arcuate nucleus, lateral hypothalamic area, zona incerta, posterior hypothalamic nucleus, medial vestibular nucleus and cerebellar interpositus nucleus. After injecting BDA into the paraventricular hypothalamic nucleus, lateral hypothalamic area and posterior hypothalamic nucleus, we found anterogradely labeled fibers in close apposition to and potential synaptic contact with urocortin 1-immunoreactive cells in the EW. On the basis of our findings, we can suggest that the connections between the EW and the hypothalamic nuclei are involved in controlling stress responses and feeding behavior. © 2013 The Authors.

Sintering of porous alumina obtained by biotemplate fibers for low thermal conductivity applications

In this research report, a sintering process of porous ceramic materials based on Al2O3 was employed using a method where a cation precursor solution is embedded in an organic fibrous cotton matrix. For porous green bodies, the precursor solution and cotton were annealed at temperatures in the range of 100-1600°C using scanning electron microscopy (SEM) and thermogravimetric (TG) analysis to obtain a porous body formation and disposal process containing organic fibers and precursor solution. In a structure consisting of open pores and interconnected nanometric grains, despite the low porosity of around 40% (calculated geometrically), nitrogen physisorption determined a specific surface area of 14m2/g, which shows much sintering of porous bodies. Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analytical methods revealed a predominant amount of α-Al2O3 in the sintered samples. Thermal properties of the sintered Al2O3 fibers were obtained by using the Laser Flash which resulted in the lower thermal conductivity obtained by α-Al2O3 and therefore improved its potential use as an insulating material. © 2012 Elsevier Ltd.

A fast cholinergic modulation of the primary acoustic startle circuit in rats

Cochlear root neurons (CRNs) are the first brainstem neurons which initiate and participate in the full expression of the acoustic startle reflex. Although it has been suggested that a cholinergic pathway from the ventral nucleus of the trapezoid body (VNTB) conveys auditory prepulses to the CRNs, the neuronal origin of the VNTB-CRNs projection and the role it may play in the cochlear root nucleus remain uncertain. To determine the VNTB neuronal type which projects to CRNs, we performed tract-tracing experiments combined with mechanical lesions, and morphometric analyses. Our results indicate that a subpopulation of non-olivocochlear neurons projects directly and bilaterally to CRNs via the trapezoid body. We also performed a gene expression analysis of muscarinic and nicotinic receptors which indicates that CRNs contain a cholinergic receptor profile sufficient to mediate the modulation of CRN responses. Consequently, we investigated the effects of auditory prepulses on the neuronal activity of CRNs using extracellular recordings in vivo. Our results show that CRN responses are strongly inhibited by auditory prepulses. Unlike other neurons of the cochlear nucleus, the CRNs exhibited inhibition that depended on parameters of the auditory prepulse such as intensity and interstimulus interval, showing their strongest inhibition at short interstimulus intervals. In sum, our study supports the idea that CRNs are involved in the auditory prepulse inhibition of the acoustic startle reflex, and confirms the existence of multiple cholinergic pathways that modulate the primary acoustic startle circuit. © 2013 Springer-Verlag Berlin Heidelberg.

Study of the glass transition temperature of as-s glasses for the fabrication of chalcogenide optical fibers

Values of glass transition temperature (Tg) and of linear expansion coefficient (α) for Asx S100-x glasses were measured in the range of concentrations 35 × 42. Because of the importance of the glass formation region 35 × 42 for the optical fibers elaboration, special attention was made on high-pure Asx S100-x glasses. For the glass in the range of 35 × 38, we measure Tg with the interval of x equal to 1 at.% of arsenic. We also measured the Tg values with the interval of x equal to 0.5 at.% of As. We obtained nonlinear behavior of Tg, reflecting the change in molecular composition of As-S glass in the glass composition range studied. The control of such parameters is important to produce optical fibers with specific numerical aperture. © 2013 The American Ceramic Society and Wiley Periodicals, Inc.

Lead-germanate glasses and fibers: A practical alternative to tellurite for nonlinear fiber applications

We report on the fabrication of novel lead-germanate glasses and fibers. We have characterized these glasses in terms of their thermal properties, Raman spectra and refractive indices (both linear and nonlinear) and present them as viable alternatives to tellurite glasses for applications requiring highly nonlinear optical fibers. © 2013 Optical Society of America.

Extraction of oil from pressed palm oil (Elaes guineensis) fibers using supercritical CO2

Residual fibers from palm oil production are a good source of carotene, since they contain more than 5% of the original oil, with about 5000 ppm of carotenoids. As carotenoids are thermosensitive molecules, supercritical CO₂ can be used for oil recovery, because this technique employs low temperatures. In this work results of oil extraction experiments from pressed palm oil fibers are shown. Fibers were from AGROPALMA, an industry which is located in Tailândia (Pará, Brazil). Extractions were carried out at 200, 250 and 300 bar and at temperatures of 45 and 55oC. Oil was analyzed by UV/vis spectrophotometry for total carotene determination. Results showed a large increase in extraction rate from 200 to 250 bar and a small variation from 250 to 300 bar. The total amount of carotenes did not increase in the course of extraction at 300 bar, but it showed a large increase at 200 and at 250 bar. Free fatty acids are present in amounts larger than those found in commercial oils.

Production and evaluation of recycled polymers from açaí fibers

The possibility of recycling and the favorable mechanical properties of the products have encouraged the study and production of thermoplastic composites from natural fibrous waste. Açaí (cabbage palm) fiber, which is removed from the seed, has been slightly investigated, as compared to what is already known about the fruit pulp. In this study, the influence of açaí fiber as an element of reinforcement in recycled everyday usage thermoplastics using simple, low cost methodology was evaluated. Recycled matrixes of high impact polystyrene and polypropylene were molded by hot compression from which the fiber composites were obtained. The FTIR technique showed that the process was efficient in preventing degradation of the açaí fibers. The influence of the fiber on the mechanical behavior of the recycled matrixes was investigated by microscopic images of compression and impact tests. The results showed better impact performance for the fiber combined with the polymeric matrixes.