Spider major ampullate gland silks (MAS) vary greatly in material properties among species but, this variation is shown here to be confined to evolutionary shifts along a single universal performance trajectory. This reveals an underlying design principle that is maintained across large changes in both spider ecology and silk chemistry. Persistence of this design principle becomes apparent after the material properties are defined relative to the true alignment parameter, which describes the orientation and stretching of the protein chains in the silk fiber. Our results show that the mechanical behavior of all Entelegynae major ampullate silk fibers, under any conditions, are described by this single parameter that connects the sequential action of three deformation micromechanisms during stretching: stressing of protein-protein hydrogen bonds, rotation of the β-nanocrystals and growth of the ordered fraction. Conservation of these traits for over 230 million years is an indication of the optimal design of the material and gives valuable clues for the production of biomimetic counterparts based on major ampullate spider silk.
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Resumen. Los ladrillos de tierra o adobes son parte del pasado y el presente en la cultura mexicana, desde tiempos inmemoriales han demostrado tener las propiedades y resistencia mecánica adecuados para un buen sistema constructivo. Los adobes se construyen a partir del suelo natural, un material abundante y por lo tanto potencialmente sostenible. El estudio cristalográfico de este tipo de materiales permite aumentar nuestra comprensión de la estructura y propiedades, esto se puede realizar al identificar el papel que juega cada mineral en las propiedades de los adobes integrando conocimientos de mineralogía y ciencia de materiales. Los adobes de la pirámide de Cholula están fabricados con suelos volcánicos y la presencia de materiales semicristalinos, amorfos y de distintos tamaños de gránulos les brinda propiedades especiales útiles para la ingeniería como, baja densidad, alto contenido de materia orgánica, alta porosidad, gran capacidad de retención de agua y límites de Atterberg altos, siendo los últimos muy importantes para un material de construcción dinámico [1-2]. La metodología que se utilizó involucra la identificación de los minerales que componen cada fase granulométrica de los adobes mediante observación por microscopía óptica de los agregados policristalinos, análisis petrográfico y difracción de rayos X (DRX) en un equipo Bruker D8 Advance con radiación Cu Kα en un intervalo angular 2θ de 6 a 90 grados. En el análisis cuantitativo de fases se determinó el contenido de material amorfo al calcular la relación entre material cristalino estándar y de la muestra de acuerdo al método combinado de refinamiento Rietveld con el de razón de intensidades de referencia (RIR), se utilizó una cantidad definida de óxido de zinc (ZnO) como material estándar cristalino [3-4]. A partir de este estudio cristalográfico fue posible identificar que la presencia de materiales amorfos y semicristalinos en la fase granulométrica más fina puede brindar las propiedades de cohesión necesarias para fabricar un material de construcción como el adobe.
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Orthotropic plastic-damage models (Betten, 1988; Luccioni et al., 1995; Luccioni and Rougier, 2005; Luccioni et al., 1996) are used for bricks and mortar in the micro-model. Even though different materials with different mechanical properties are dealt with, solid clay bricks, mortar and masonry are frictional materials, that is, their behaviour is influenced by hydrostatic pressure. Bricks are normally made of isotropic materials and mortar is also approximately isotropic. However, mortar and bricks are modelled as orthotropic materials in order to account for the weakness of the interfaces and the possibility of relative displacements without explicitly modelling the interfaces (Luccioni et al., 2005).
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one generally can ﬁnd a ﬁner and more detailed material distribution that is better than the coarser design. This phenomenon is called mesh-dependence. Ways to circumvent the ill-posedness problem are reviewed in  and can be divided into two groups, namely relaxation methods and restriction methods. Relaxation meth- ods, which are the aim of this chapter, expand the design space by introducing an inﬁnitely ﬁne microstructure as material properties in every element of the struc- ture, see  for details. Using this approach leads to structures with large “grey regions” (0 < χ < 1), which are very diﬃcult to manufacture but, by contrast, they allow us to design graded materials, that is to say, two-component composites characterized by a gradual variation from the α-material to the β-material. On the other hand, restriction methods, which will be described in Chapter 3, introduce ex- tra constraints on design variables so as to ﬁnd optimized solutions over the initial design space. It is specially useful when we are interested in designing optimized structures and mechanisms because we must distinguish where the materials should be placed separately.
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Fitting the experimental data to Mason’s model requires precise values of the material properties of all layers involved in the test structures and of all the dimensions of the devices (thickness of layers and areas of the resonators). The area of the top electrode, which defined the areas of the SMRs, was measured carefully with an optical microscope to avoid errors due to the undercutting during the electrode definition. The properties of the different materials used for fitting the
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Castings are produced by a manufacturing method which gives the components local properties that are dependent on design, metallurgy and casting method. E.g. the wall thickness influences the resulting coarseness and type of microstructure, and the material will have local material properties which depend on the local metallurgical and thermal history. The mechanical behaviour of a cast iron component can vary significantly in the casting volume, which makes it difficult to optimize the castings with good accuracy. Structural analyses of cast products in service, e.g. using Finite Element Method (FEM) simulations, are typically based on the assumption of constant material properties throughout the product. This is not an optimal representation of the variations that are actually found in the casting. By predicting the distribution of microstructural features and establishing quantitative relationships between microstructure and mechanical behaviour, it will be possible to calculate the local material properties and the deformation behaviour of cast products with higher precision.
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The m ain aim o f D EM i s t o ade quately r epresent a par ticular r eal phen omenon. It t herefore requires the use of contact models that represent the characteristics of the simulated material as reliably as possible. It also requires the use of values that adequately describe the properties of t he m aterial under s tudy. T hese values can be determined by direct m easurements or via calibration procedures. The f irst method is usually preferable to the second since, in the latter, the ad justed v alues can be s trongly dependent on the nu merical c ode em ployed in the calibration procedure. However, these properties must be obtained at a particle (microscopic) level and it sometimes makes the direct determination difficult. Until now very few procedures have been described in the scientific literature and, in addition, very little accurate information about the values of the material properties is available.
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This manuscript is divided in two main blocks. The first one includes Chaps. 2 to 4 and comprises the theoretical basis necessary for the comprehension of the study carried out in this Thesis. Particularly, the second chapter focuses on the material properties of wurzite III-nitride semiconductors (AlN, GaN, InN) in terms of structural, morphological and optical properties. The growth techniques used within the framework of this Thesis are also described there. Furthermore, Chap. 3 summarizes the different experimental techniques used along this work for the characterization of group-III-nitrides. The fourth chapter aims at being a basic guide on the theoretical concepts of integrated optics. A large section is dedicated to the analytic study of light modal guiding in planar waveguides as well as the numerical analysis technique used for investigating more complex non-planar optical devices. Furthermore, the theory of design and fabrication of optical waveguides is also treated while the description of the experimental setup used for optical characterization of the devices in the linear and nonlinear regimes is also described.
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microscopy (AFM), and photoluminescence (PL) spectroscopy. Our experimental results indicate that on changing porosity of the PS substrates, regularity of the spatial distribution of the ZnO nanocrystallites can be controlled. While the morphology and grain size of ZnO depended strongly on the morphology and pore size of the PS substrates, the rectifying factors of the metal semiconductor junction were found to be different by a factor of 3. The deposition of semiconducting oxides on such mesoporous substrates/templates offers the possibility to control their properties and amplify their sensing response.
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Medical grade titanium alloys have a significantly higher strength to weight ratio than competing stainless steels. The range of available titanium alloys enables medical specialist designers to select materials and forms closely tailored to the needs of the application. The full range of alloys reaches from high ductility commercially pure titanium where extreme formability is essential, to fully heat treatable alloys with strength above 1300 MPa (190 ksi). Shape memory alloys, based on titanium, further extend the range of useful properties and applications. Light, strong and totally bio- compatible, titanium is one of the few materials that naturally match the requirements for implantation in the human body in several applications such as: bone and joint replacements, dental implants, cardiovascular devices, external prostheses, and surgical instruments [Lowrie, 2001].
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Resultados: diecinueve compuestos fueron separados y los principales eran biciclogermacreno (20,5 %), betacariofileno (19,7 %) y espatulenol (19,2 %). Conclusiones: dada la extensa distribución del material crudo en el estado de Río Grande do Sul, Brasil, se debe incrementar los estudios sobre las características químicas y las actividades biológicas del aceite esencial de Schinus molle.
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For example, it binds negatively charged red blood cells thereby promoting clotting, and this hemostatic property has made it an important component in wound dressings. Similar to other cationic polymers, chitosan possesses antimicrobial properties. Although the mechanisms behind its antimicrobial nature are not completely understood, it is thought that because chitosan is cationic, it likely disrupts anions in bacterial cell walls leading to suppression of biosynthesis and disruption of mass transport across the cell walls (Levengood and Zhang 2014).
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Este artigo investiga a influência da utilização de Inconel 182 como um terceiro material, nas propriedades mecânicas de diferentes aços inoxidáveis soldados a aços carbono com uso de eletrodo revestido. Para tanto foram usados os seguintes métodos: análise microestrutural, ensaios de microdureza Vickers e ensaios mecânicos de tensão. Tem sido empregado o processo de solda com eletrodo revestido, porque é o mais comum no campo de solda para a construção. Os resultados mostram que quando as uniões são realizadas sem esse terceiro material, as propriedades mecânicas são superiores às das juntas soldadas com auxílio do Inconel 182. Esta metodologia, ora criticada, tem sido proposta para a reabilitação de estruturas de concreto em ambiente marinho, com uso de barras de aço inox como reforços.
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Wear tests were carried out in a wear-testing machine (WAZAU TRM 1000) with a pin-on-disc conﬁguration under dry sliding conditions and without eliminating the formed debris. Before the test, the specimen and the count- erbody were cleaned using methanol in order to avoid the presence of humidity and other undesirable ﬁlms such as grease. The average sample roughness was always kept in the range 10 ± 3 lm. Most of the procedures for the ASTM standard G99-04 were followed . However, sev- eral modiﬁcations were introduced that primarily involved the pin shape. Prismatic pins were made of the material under study (with modiﬁed and with conventional coat- ings) with a rectangular section of 2.5 mm 6.3 mm. With this geometry, the nominal contact area remained constant during the tests despite the wear process. The disc was made to have the same coating as the sample and all the wear test conditions were selected according to the indus- trial application in which this material is involved. The disc rotates horizontally at a sliding speed of 0.1 m s 1 . A dead- weight loading system was used to perform the tests at nominal normal pressures ranging from 5 to 65 MPa. At least three tests were carried out at for each experimental condition. The coeﬃcient of friction was obtained using a torque transducer and the variation of the pin height was registered using a linear variable diﬀerential transformer with a precision of ±1 lm. The pin wear rate was calcu- lated through mass measurements using a METTLER– TOLEDO balance with a resolution of 0.01 mg. The wear rate was computed using the following equation:
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considerations such as part geometry, material, mold design and process variables. The simulation module being considered in this study is the mold fill analysis (based on Cadmould, a commercial simulation system). Material, mold design, injection machine is already defined. As part of this study, complexity taxonomy for plastic parts was developed, as well as a differentiation between the engineering team involved in terms of expertise. Several information sources were used to develop a case study, which approaches a part fill time optimization. The scenario in which this optimization is made is a
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The aim of this work is the synthesis and chemical and structural characterization of four oligomeric poly(ether- azomethine)s, designated PAM-I, PAM-II, PAM-III and PAM-IV, which contain silicon atoms and imino functions in their main chains in addition to methyl or phenyl groups in their lateral segments. Thus, the structural properties of the materials were studied using nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and elemental analyses. The optical properties of the samples were measured via UV-vis spectroscopy (optical absorption). Their solubilities were tested in several organic solvents, and their thermal behavior was established by thermogravimetric analysis (TGA) and diﬀerential scanning calorimetry (DSC). Finally, two diﬀerent lms were prepared using the spin-coating technique for deposition, using silicon wafers previously treated with piranha solution (H 2 SO 4 : H 2 O 2 ) as the substrate. The samples
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Fig. 3 compares the XRD patterns of a degummed silkworm silk fiber 16 (Fig. 3a) and that of a silkworm silk gut prepared after immersion in a 2% acetic acid bath for 2 minutes (Fig. 3b). Fig. 2 Tensile properties of silkworm guts expressed as engineering stress–engineering strain curves. 2% acetic acid solution and immersion time of 2 minutes are taken as reference conditions. (a) Silkworm guts prepared in a 2% acetic acid solution for different times. (b) Silkworm guts prepared after 2 minutes of immersion in different acetic acid concentration solutions. (c) Comparison of the engineering stress–strain curves of representative silkworm guts and those of native silkworm silk fibers either as spun (forcibly silked, black lines) or after being subjected to degumming. (d) Comparison of the tensile properties of silkworm guts and naturally spun silkworm silk fibers in terms of force–engineering strain curves. Forces of the naturally spun fibers are multiplied by 100 in order to allow comparison in a single plot.
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The addition of gadolinium at different percentages in the catalyst affects its optical and structural properties, causing a phase change due to a transition in the crystalline structure of the material. The phase transition occurs from the monoclinic alpha phase to a tetragonal beta phase, due to the rearrangement of the atoms as gadolinium is added to the catalyst. A reduction of the Bandgap in the doped materials was also obtained, since the Bi 2 O 3 presents an optical Bandgap of 2.95 eV and when adding the
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En la presente investigación se estudió la relación entre las propiedades del estado fresco y el estado endurecido de un material compuesto formado por una matriz de cemento Pórtland reforzado con fibra de fique dispuestas al azar, las propiedades evaluadas en estado fresco fueron: ondulabilidad, fluidez, drenabilidad y en estado endurecido el módulo de la resistencia a la flexión. Las muestras se prepararon con diferentes materias primas (Fibra de fique, Bentonita, Pulpa, Humo de Sílice y Acronal), las componentes se agregaron a una mezcladora a velocidad constante, luego se vertió la mezcla en una cámara de drenado donde se extrajo el agua y se conformó la lámina con dimensiones de 130x50x6 mm, luego se sumergió en una piscina de curado por 28 días para ser evaluado el módulo de la resistencia a la flexión. El modelo de regresión lineal que se propuso para predecir el módulo de la resistencia a la flexión, en función de las propiedades en estado fresco, se realizó a través del análisis de las interacciones entre las variables de la formulación de la mezcla utilizada. Como resultado del modelo de regresión se obtuvo que existe una clara correlación entre el módulo de la resistencia a la flexión y las propiedades predictoras ondulabilidad, fluidez y drenabilidad, además estas tienen un efecto negativo sobre el módulo de la resistencia a la flexión.
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Precursor graphite and PET substrate were characterized by XRD (Fig. 2b). Graphite diffractogram showed typical peak at 26.5°, corresponding to (002) plane and interlaminar distance of 0.334 nm , while peak of GOx showed a displacement at lower 2-theta degrees of 11.25° (001) and interlaminar distance of 0.786nm. The increase on interlaminar distance was attributed to the bond of different oxygen functionalities in basal plane and edges, such as hydroxyl, carboxyl and epoxy groups. GOx presented a base peak broader than graphite, which could be related to decrease on crystallinity of GO due to exfoliation treatment allowing a better delamination of rGOx sheets. RGO_15C HP and RGO_20 C films showed a decrement on characteristic rGOx peak, mainly attributed to loss of oxygen functionalities due to thermal reduction process. However, the presence of GOx after laser treatment indicated remaining oxidized material on the film bottom . Bands at 23° and 26° in rGOx films correspond to PET substrate where rGOx is supported.
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