Estudo do comportamento mecânico de areias artificialmente cimentadas

Soil improved with the addition of cement have been utilized as an alternative to the construction of various types of geotechnical works, almost always present economic and environmental advantages. This paper presents a study on the usage of cement in the improvement of mechanical properties of sandy soils, characteristic of the region of Natal, collected from its dunes. This research was made in order to analyze the influence of cement content, voids, and also including water immersion and confining pressure. Samples molded from cement-soil mixtures were tested for unconfined compression tests and triaxial tests. The samples had the percentage of cement mixed in 2.5%, 5% and 10% by weight. The cement agent used was the Portland Cement of High Early strength(CPV-ARI), which promoted agility to the experimental procedure for presenting a rapid gain in strenght. The void ratio used ranged from 0.7 (more compact), 0,9 and 1,1(softer). The soil under study can be considered as pure sand. In general, it can be stated that the larger the amount of cement added to the sand studied is, the greater ultimate strength will be. Likewise, as more compact the soil is, the less void ratio and more resistant it will be present. The confining pressure tends to increase the resistance of the specimens. The cementing adopted grades showed that the use of different criteria for failure did not significantly alter the stress-strain parameters for the sand studied. The angle of friction values were found within the typical range of medium and compact sands. Cementing acted in the sand providing an intercepted cohesion which increased enhancing the potential cementation. In triaxial compression tests, the sand with void ratio is equal to 0.7 and showed the expected behavior for a compact sand while the stress-strain behavior of the same sand with the void ratio of 0.9 tended to be expected for the soft sand as well

Ventilatory responses to skin extract in catfish

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

Tolerância à salinidade em feijão (Phaseolus vulgaris L)

Uma das aplicações das técnicas da cultura de tecidos no melhoramento é a identificação de linhas de células que apresentam tolerância à salinidade. Vários autores obtiveram linhas de células tolerantes ao estresse salino; e estudo de mecanismos bioquímicos da tolerância a sais em plantas tem demonstrado altas correlações entre estes e o acúmulo de macromoléculas em tecido de plantas superiores. Para verificar essas correlações em feijão (Phaseolus vulgaris cv IAC carioca), calos oriundos de eixos embrionários foram cultivados em meio sólido, suplementado com NaCl nas concentrações de 0 a 60 mM. Após 13 dias de incubação, os calos foram coletados e analisados quanto ao crescimento relativo, teor de proteínas, teor de prolina e atividade da peroxidase. Os parâmetros analisados mostraram decréscimo no crescimento relativo e no de proteínas em resposta ao NaCl. Paralelamente, observou-se aumento significativo no conteúdo de prolina e atividade da enzima peroxidase.

Expressão gênica diferencial durante déficit hídrico em duas cultivares de cana-de-açucar

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Quantificação da trealose e da prolina livre em cana-de-açúcar sob efeito da disponibilidade hídrica do solo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estados emocionais de estresse e cortisol salivar na escalada em rocha

Pós-graduação em Ciências da Motricidade - IBRC

The cone loading test to estimate deformability moduli of a tropical soil

The Cone Loading Test (CLT) consists of the execution of a load test on the piezocone probe in conjunction with the CPT test. The CLT yields the modulus ECLT, a parameter that can be used in the estimative of foundation settlement. It is also presented here the interpretation and the process to determine ECLT values from the stress-displacement curves obtained from cone loading tests. Several CLT tests were conducted at the experimental research site of São Paulo State University, Bauru-SP-Brazil. The geotechnical profile at the studied site is a brown to bright red slightly clayey fine sand, a tropical soil common to this region which is lateritic, unsaturated and collapsible. The results of CLT tests satisfactorily represent the behavior of the investigated soil. The penetrometric modulus ECLT for each depth was calculated considering the elastic behavior in the initial linear segment of the soil stress-strain curve. The ECLT moduli obtained for the various tests were compared to moduli obtained from PMT and DMT test results performed at same studied site. The shear modulus degradation curves obtained from the CLT tests are also presented. The comparison to PMT and DMT results indicates the CLT test is a viable complementary test to the CPT in the quest for better understanding stress-strain behavior of soils. Further, the CLT test provides a graphic visualization of the degradation of the shear modulus with increasing levels of strain. As a hybrid geotechnical test, CPT+CLT can be valuable in the investigation of non-conventional collapsible soils, whose literature lack reference parameters for the prediction of settlement in the design of foundations.

Morphology and Deformation Mechanisms and Tensile Properties of Tetrafunctional Multigraft Copolymers

Morphology and deformation mechanisms and tensile properties of tetrafunctional multigraft (MG) polystrene-g-polyisoprene (PS-g-PI) copolymers were investigated dependent on PS volume fraction and number of branch points. The combination of various methods such as TEM, real time synchrotron SAXS, rheo-optical FTIR, and tensile tests provides comprehensive information at different dimension levels.TEMand SAXS studies revealed that the number of branch points has no obvious influence on the microphase-separated morphology of tetrafunction MG copolymers with 16 wt % PS. But for tetrafunctional MG copolymers with 25 wt % PS, the size and integrity of PS microdomains decrease with increasing number of branch point. The deformation mechanisms ofMGcopolymers are highly related to the morphology. Dependent on the microphase-separated morphology and integrity of the PS phase, the strain-induced orientation of the PS phase is at different size scales. Polarized FT-IR spectra analysis reveals that, for all investigated MG copolymers, the PI phase shows strain-induced orientation along SD at molecular scale. The proportion of the PI block effectively bridging PS domains controls the tensile properties of the MGcopolymers at high strain, while the stress-strain behavior in the low-mediate strain region is controlled by the continuity of PS microdomains. The special molecular architecture, which leads to the higher effective functionality of PS domains and the higher possibility for an individual PI backbone being tethered with a large number of PS domains, is proposed to be the origin of the superelasticity for MG copolymers.

Pre- and post-puberty physiological plasma oxytocin concentrations in male domestic cats (Felis silvestris catus)

Souza J.O.T., Andriolo A., Franci C.R. & Genaro G. 2012. Pre- and post-puberty physiological plasma oxytocin concentrations in male domestic cats (Felis silvestris catus). Pesquisa Veterinaria Brasileira 32(11):1196-1198. Programa de Pos-Graduacao em Psicobiologia, Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Cx. Postal 390, Ribeirao Preto, SP 14001-970, Brazil. E-mail: gelsongenaro@hotmail.com The hormone oxytocin is released by the neuropituitary gland through stimulation of the neurons of the supraoptic and paraventricular nuclei of the hypothalamus. In order to determine the physiological concentrations of this hormone in domestic cats, blood samples were collected from 15 male animals (Felis silvestris catus) during the pre- and post-puberty periods (at four and eight months of age, respectively). Oxytocin determination was accomplished by radioimmunoassay. The average oxytocin concentrations measured in the pre- and post-puberty periods were 2.54 +/- 0.24 (mu g/dL) and 2.53 +/- 0.28 (mu g/dL), respectively, and there were no statistical differences between these measurements. Because there are few literature on the analysis of this hormone, especially in the case of male Felis silvestris catus, more studies on the influence of oxytocin on the physiology and reproduction of this species should be conducted under maintenance and situations of stress (such as transportation), and other routine events.

Ventilatory responses to skin extract in catfish

The ventilation rate (VR) of an ostariophysan fish, the speckled catfish Pseudoplaty - stoma coruscans, exposed to a chemical alarm cue was measured in the present study in multiple contexts. The influence of the extraction techniques, skin donor food intake and quantity of the alarm cue (skin extract) on this autonomic response was considered. Overall, the catfish VR decreased significantly when exposed to the skin extract (chemical alarm cue) compared with exposure to distilled water (control). No effect of the extraction technique was found. Increasing doses of the skin extract induced a VR reduction of similar magnitude. However, extract obtained from daily-fed fish induced a significant decrease in the VR, whereas extract obtained from foodrestricted fish did not induce any change in the VR. Thus, food intake was associated with the production of a more easily recognizable alarm cue in the speckled catfish. Interestingly, this effect was not related to differences in the number of club cells in the donor catfish epidermis. Dashing, or rapid swimming, a normal component of the alarm response in fish, including this catfish species, was not observed here, and hypoventilation was always associated with no swimming reaction. Together, these results suggest that hypoventilation is a reaction to a chemical alarm cue, likely resulting in improved crypsis, causing the fish to become less easily perceived by a potential predator that usually strikes prey in response to movement.

Short steel and concrete columns under high temperatures

The growing demand for knowledge about the effect of high temperatures on structures has stimulated increasing research worldwide. This article presents experimental results for short composite steel and concrete columns subjected to high temperatures in ovens with or without an axial compression load, numerically analyzes the temperature distribution in these columns after 30 and 60 minutes and compares them with experimental results. The models consist of concrete-filled tubes of three different thicknesses and two different diameters, and the concrete fill has conventional properties that remained constant for all of the models. The stress-strain behavior of the composite columns was altered after exposure to high temperatures relative to the same columns at room temperature, which was most evident in the 60-minute tests due to the higher temperatures reached. The computational analysis adopted temperature rise curves that were obtained experimentally.

Experimental study on Carbon FRP-confined elliptical concrete columns

It is well recognized that the technique of strengthening reinforced concrete (RC) using fiber-reinforced polymer (FRP) jackets is more effective for circular sections, but less effective for rectangular sections. Indeed the presence of angular corners does not permit a uniform confinement to be provided by the FRP jackets to the columns. While rounded corners can enhance the effectiveness of FRP confinement, it will be more efficient to modify the rectangular section into an elliptical section. In addition to the better confinement effectiveness, from an aesthetical point of view, the shape modification would be a surprise to the built environment. This paper presents an experimental study on the behavior of FRP-confined concrete columns with elliptical section. Thirty-two short columns, divided in eight batches, were tested under axial compression. Each batch presents four specimens with different elliptical sections, determined by the aspect ratio a/b, that is the ratio between the minor and mayor axis. By varying this value from 1.0 to 2.0 (1.0, 1.3., 1.7, 2.0), the section becomes more and more elliptical starting from a circular shape. In this way it is possible to study the trend of effectiveness of FRP confinement for different section geometries. It is also interesting to study how the confinement effectiveness may vary by changing the cylinder strength of concrete and the number of the layers of CFRP. For this reason, a cylinder strength of concrete of 25 and 45 MPa have been used for the present research work, and half of the specimens were wrapped by one layer of CFRP, while the remaining specimens were wrapped with two layers. A simple analysis of the results has been carried out for evaluating the experimental work described in the present document. Further studies and analysis on this work should help to achieve a new and more accurate stress-strain model for CFRP-confined concrete columns with an elliptical section.

Phytoremediation by poplar: polyphenols polyamines and oxidative damage in the response to heavy metals in in vitro and in hydroponic cultures.

Poplar is considered a good candidate for phytoremediation, but its tolerance to heavy metals has not been fully investigated yet. In the present work, two different culture systems (in vitro and aeroponic/hydroponic) and two different stress tolerant clones of Populus alba (AL22 and Villafranca) were investigated for their total polyphenol and flavonoid content, individual phenolic compounds, polyamine, lipid peroxidation and hydrogen peroxide levels in response to Cu. In AL22 poplar plants cultured in vitro in the presence or absence of 50 μM Cu, total leaves polyphenol and flavonoid content was higher in treated samples than in controls but unaltered in the roots. Equally the same clone, grown under aeroponic conditions and hydroponically treated for 72 h with 100 μM Cu, displayed increased amount of polyphenols and flavonoids in the leaves, in particular chlorogenic acid and quercetin, and no differences in the roots. In exudates from treated roots total polyphenols and flavonoids, in particular catechin and epicatechin, were more abundant than in controls. Polyamine levels show an increase in conjugated putrescine (Put) and spermidine (Spd) was found. In the Villafranca clone, treated with 100 μM Cu for 6, 24 and 72 h, the pattern of polyphenol and flavonoid accumulation was the same as in AL22; in Cu-treated roots these compounds decreased compared with controls while they increased in root exudates. Free polyamine levels rose at 24 and 72 h while only conjugated Put increased at 24 h. Cu-treated Villafranca plants exhibited a higher malondialdehyde production than controls indicative of membrane lipid peroxidation and, therefore, oxidative stress. An in vitro experiment was carried to investigate the antioxidant effect of the polyamine spermidine (Spd). Exogenous Spd, supplied together with 100 μM Cu, reduced the accumulation of polyphenols and flavonoids, MDA and hydrogen peroxide induced by Cu.

Studio numerico e sperimentale delle miscele di aggregati per i conglomerati bituminosi

I crescenti volumi di traffico che interessano le pavimentazioni stradali causano sollecitazioni tensionali di notevole entità che provocano danni permanenti alla sovrastruttura. Tali danni ne riducono la vita utile e comportano elevati costi di manutenzione. Il conglomerato bituminoso è un materiale multifase composto da inerti, bitume e vuoti d'aria. Le proprietà fisiche e le prestazioni della miscela dipendono dalle caratteristiche dell'aggregato, del legante e dalla loro interazione. L’approccio tradizionalmente utilizzato per la modellazione numerica del conglomerato bituminoso si basa su uno studio macroscopico della sua risposta meccanica attraverso modelli costitutivi al continuo che, per loro natura, non considerano la mutua interazione tra le fasi eterogenee che lo compongono ed utilizzano schematizzazioni omogenee equivalenti. Nell’ottica di un’evoluzione di tali metodologie è necessario superare questa semplificazione, considerando il carattere discreto del sistema ed adottando un approccio di tipo microscopico, che consenta di rappresentare i reali processi fisico-meccanici dai quali dipende la risposta macroscopica d’insieme. Nel presente lavoro, dopo una rassegna generale dei principali metodi numerici tradizionalmente impiegati per lo studio del conglomerato bituminoso, viene approfondita la teoria degli Elementi Discreti Particellari (DEM-P), che schematizza il materiale granulare come un insieme di particelle indipendenti che interagiscono tra loro nei punti di reciproco contatto secondo appropriate leggi costitutive. Viene valutata l’influenza della forma e delle dimensioni dell’aggregato sulle caratteristiche macroscopiche (tensione deviatorica massima) e microscopiche (forze di contatto normali e tangenziali, numero di contatti, indice dei vuoti, porosità, addensamento, angolo di attrito interno) della miscela. Ciò è reso possibile dal confronto tra risultati numerici e sperimentali di test triassiali condotti su provini costituiti da tre diverse miscele formate da sfere ed elementi di forma generica.

Desarrollo de nuevos tratamientos térmicos para aleaciones avanzadas de interés aeroespacial

La corrosión bajo tensiones (SCC) es un problema de gran importancia en las aleaciones de aluminio de máxima resistencia (serie Al-Zn-Mg-Cu). La utilización de tratamientos térmicos sobremadurados, en particular el T73, ha conseguido prácticamente eliminar la susceptibilidad a corrosión bajo tensiones en dichas aleaciones pero a costa de reducir su resistencia mecánica. Desde entonces se ha tratado de optimizar simultáneamente ambos comportamientos, encontrándose para ello diversos inconvenientes entre los que destacan: la dificultad de medir experimentalmente el crecimiento de grieta por SCC, y el desconocimiento de las causas y el mecanismo por el cual se produce la SCC. Los objetivos de esta Tesis son mejorar el sistema de medición de grietas y profundizar en el conocimiento de la SCC, con el fin de obtener tratamientos térmicos que aúnen un óptimo comportamiento tanto en SCC como mecánico en las aleaciones de aluminio de máxima resistencia utilizadas en aeronáutica. Para conseguir los objetivos anteriormente descritos se han realizado unos cuarenta tratamientos térmicos diferentes, de los cuales la gran mayoría son nuevos, para profundizar en el conocimiento de la influencia de la microestructura (fundamentalmente, de los precipitados coherentes) en el comportamiento de las aleaciones Al-Zn-Mg-Cu, y estudiar la viabilidad de nuevos tratamientos apoyados en el conocimiento adquirido. Con el fin de obtener unos resultados aplicables a productos o semiproductos de aplicación aeronáutica, los tratamientos térmicos se han realizado a trozos grandes de una plancha de 30 mm de espesor de la aleación de aluminio 7475, muy utilizada en las estructuras aeronáuticas. Asimismo con el objeto de conseguir una mayor fiabilidad de los resultados obtenidos se han utilizado, normalmente, tres probetas de cada tratamiento para los diferentes ensayos realizados. Para la caracterización de dichos tratamientos se han utilizado diversas técnicas: medida de dureza y conductividad eléctrica, ensayos de tracción, calorimetría diferencial de barrido (DSC), metalografía, fractografía, microscopia electrónica de transmisión (MET) y de barrido (MEB), y ensayos de crecimiento de grieta en probeta DCB, que a su vez han permitido hacer una estimación del comportamiento en tenacidad del material. Las principales conclusiones del estudio realizado se pueden resumir en las siguientes: Se han diseñado y desarrollado nuevos métodos de medición de grieta basados en el empleo de la técnica de ultrasonidos, que permiten medir el crecimiento de grieta por corrosión bajo tensiones con la precisión y fiabilidad necesarias para valorar adecuadamente la susceptibilidad a corrosión bajo tensiones. La mejora de medida de la posición del frente de grieta ha dado lugar, entre otras cosas, a la definición de un nuevo ensayo a iniciación en probetas preagrietadas. Asimismo, se ha deducido una nueva ecuación que permite calcular el factor de intensidad de tensiones existente en punta de grieta en probetas DCB teniendo en cuenta la influencia de la desviación del plano de crecimiento de la grieta del plano medio de la probeta. Este aspecto ha sido determinante para poder explicar los resultados experimentales obtenidos ya que el crecimiento de la grieta por un plano paralelo al plano medio de la probeta DCB pero alejado de él reduce notablemente el factor de intensidades de tensiones que actúa en punta de grieta y modifica las condiciones reales del ensayo. Por otro lado, se han identificado los diferentes constituyentes de la microestructura de precipitación de todos los tratamientos térmicos estudiados y, en especial, se ha conseguido constatar (mediante MET y DSC) la existencia de zonas de Guinier-Preston del tipo GP(II) en la microestructura de numerosos tratamientos térmicos (no descrita en la bibliografía para las aleaciones del tipo de la estudiada) lo que ha permitido establecer una nueva interpretación de la evolución de la microestructura en los diferentes tratamientos. Al hilo de lo anterior, se han definido nuevas secuencias de precipitación para este tipo de aleaciones, que han permitido entender mejor la constitución de la microestructura y su relación con las propiedades en los diferentes tratamientos térmicos estudiados. De igual manera, se ha explicado el papel de los diferentes microconstituyentes en diversas propiedades mecánicas (propiedades a tracción, dureza y tenacidad KIa); en particular, el estudio realizado de la relación de la microestructura con la tenacidad KIa es inédito. Por otra parte, se ha correlacionado el comportamiento en corrosión bajo tensiones, tanto en la etapa de incubación de grieta como en la de propagación, con las características medidas de los diferentes constituyentes microestructurales de los tratamientos térmicos ensayados, tanto de interior como de límite de grano, habiéndose obtenido que la microestructura de interior de grano tiene una mayor influencia en el comportamiento en corrosión bajo tensiones que la de límite de grano. De forma especial, se ha establecido la importancia capital, y muy negativa, de la presencia en la microestructura de zonas de Guinier-Preston en el crecimiento de la grieta por corrosión bajo tensiones. Finalmente, como consecuencia de todo lo anterior, se ha propuesto un nuevo mecanismo por el que se produce la corrosión bajo tensiones en este tipo de aleaciones de aluminio, y que de forma muy resumida se puede concretar lo siguiente: la acumulación de hidrógeno (formado, básicamente, por un proceso corrosivo de disolución anódica) delante de la zonas GP (en especial, de las zonas GP(I)) próximas a la zona libre de precipitados que se desarrolla alrededor del límite de grano provoca enfragilización local y causa el rápido crecimiento de grieta característico de algunos tratamientos térmicos de este tipo de aleaciones. ABSTRACT The stress corrosion cracking (SCC) is a major problem in the aluminum alloys of high resistance (series Al-Zn-Mg-Cu). The use of overaged heat treatments, particularly T73 has achieved virtually eliminate the susceptibility to stress corrosion cracking in such alloys but at the expense of reducing its mechanical strength. Since then we have tried to simultaneously optimize both behaviors, several drawbacks found for it among them: the difficulty of measuring experimentally the SCC crack growth, and ignorance of the causes and the mechanism by which SCC occurs. The objectives of this thesis are to improve the measurement system of cracks and deeper understanding of the SCC, in order to obtain heat treatments that combine optimum performance in both SCC and maximum mechanical strength in aluminum alloys used in aerospace To achieve the above objectives have been made about forty different heat treatments, of which the vast majority are new, to deepen the understanding of the influence of microstructure (mainly of coherent precipitates) in the behavior of the alloys Al -Zn-Mg-Cu, and study the feasibility of new treatments supported by the knowledge gained. To obtain results for products or semi-finished aircraft application, heat treatments were performed at a large pieces plate 30 mm thick aluminum alloy 7475, widely used in aeronautical structures. Also in order to achieve greater reliability of the results obtained have been used, normally, three specimens of each treatment for various tests. For the characterization of these treatments have been used several techniques: measurement of hardness and electrical conductivity, tensile testing, differential scanning calorimetry (DSC), metallography, fractography, transmission (TEM) and scanning (SEM) electron microscopy, and crack growth tests on DCB specimen, which in turn have allowed to estimate the behavior of the material in fracture toughness. The main conclusions of the study can be summarized as follows: We have designed and developed new methods for measuring crack based on the use of the ultrasound technique, for measuring the growth of stress corrosion cracks with the accuracy and reliability needed to adequately assess the susceptibility to stress corrosion. Improved position measurement of the crack front has resulted, among other things, the definition of a new initiation essay in pre cracked specimens. Also, it has been inferred a new equation to calculate the stress intensity factor in crack tip existing in DCB specimens considering the influence of the deviation of the plane of the crack growth of the medium plane of the specimen. This has been crucial to explain the experimental results obtained since the crack growth by a plane parallel to the medium plane of the DCB specimen but away from it greatly reduces the stress intensity factor acting on the crack tip and modifies the actual conditions of the essay. Furthermore, we have identified the various constituents of the precipitation microstructure of all heat treatments studied and, in particular note has been achieved (by TEM and DSC) the existence of the type GP (II) of Guinier-Preston zones in the microstructure of several heat treatments (not described in the literature for alloys of the type studied) making it possible to establish a new interpretation of the evolution of the microstructure in the different treatments. In line with the above, we have defined new precipitation sequences for these alloys, which have allowed a better understanding of the formation of the microstructure in relation to the properties of different heat treatments studied. Similarly, explained the role of different microconstituents in various mechanical properties (tensile properties, hardness and toughness KIa), in particular, the study of the relationship between the tenacity KIa microstructure is unpublished. Moreover, has been correlated to the stress corrosion behavior, both in the incubation step as the crack propagation, with the measured characteristics of the various microstructural constituents heat treatments tested, both interior and boundary grain, having obtained the internal microstructure of grain has a greater influence on the stress corrosion cracking behavior in the grain boundary. In a special way, has established the importance, and very negative, the presence in the microstructure of Guinier-Preston zones in crack growth by stress corrosion. Finally, following the above, we have proposed a new mechanism by which stress corrosion cracking occurs in this type of aluminum alloy, and, very briefly, one can specify the following: the accumulation of hydrogen (formed basically by a corrosive process of anodic dissolution) in front of the GP zones (especially the GP (I) zones) near the precipitates free zone that develops around grain boundary causes local embrittlement which characterizes rapid crack growth of some heat treatments such alloys.