306,096 research outputs found
Recent advances on intelligent packaging as tools to reduce food waste
No full text[EN] Food waste is one of the main issues for international organisms. It is not only an ethical and economic issue but it also depletes the environment of limited natural resources. Among strategies suitable for fighting such challenge, intelligent packaging is an interesting tool to reduce waste derived from households and retailers. A revision of 45 recent advances in the area of optical systems for freshness monitoring is reported herein. The study covers fruits, vegetables, fish products and meat since they are the most representative fields of application. Furthermore, a discussion about the main research challenges and opportunities that will be faced by intelligent packaging in the coming years is included. (C) 2017 Elsevier Ltd. All rights reserved.The authors thank financial support from the Spanish Government (project MAT2015-64139-C4-1-R) and the Generalitat Valenciana (project (Project PROMETEOII/2014/047).Poyatos-Racionero, E.; Ros-Lis, JV.; Vivancos, J.; Martínez-Máñez, R. (2018). Recent advances on intelligent packaging as tools to reduce food waste. Journal of Cleaner Production. 172:3398-3409. https://doi.org/10.1016/j.jclepro.2017.11.075S3398340917
Humanización de la revolución de la información
No full textProvides a brief historical perspective on the role of books and libraries in the United States and asks whether the impact of electronic media will result in the loss of the 'values of the book culture that made democracy and the responsible use of freedom possible'. Describes the efforts of the Library of Congress to create a National Digital Library of American history and culture, to make free and reliable educational content accessible on the Web and develop human mediators who can help integrate new online knowledge with the older wisdom in books.
Translated by A. Lozano Palacios, y E. Poyatos Huertas
Control o caos bibliográfico : un programa para los servicios bibliográficos nacionales del siglo XXI
No full textPaper presented at the 67th IFLA General Conference and Council, Bos-ton, USA, August 16-25, 2001. Reviews inter-national efforts over the past 30 years to achieve Universal Bibliographic Control through international standardization of cataloguing rules and formats, and concludes that, while there is no reason in principle these should not be applied to electronic documents and resources, there are practical reasons why this is a formidable task. Suggests that the idea of cataloguing the World Wide Web is not only unattainable but also undesirable, since most of what is on the Web does not merit the expense and time of cataloguing. Criticizes the concept of metadata, and particularly the Dublin Core as a method of describing electronic bibliographic entities, which have the same attributes as other bibliographic entities and can thus be catalogued in such a way that the resulting records can be fully integrated into library catalogues.
Translated by A. Lozano Palacios, y E. Poyatos Huertas
Advanced finite elements for modelling additive-manufactured composite components
No full textThe massive use of composites in the aerospace industry is now possible because of the advent of two enabling technologies; the Automated Tape Laying (ATL) and the Automated Fibre Placement (AFP) processes. On the other hand, the emergence of composite 3D printing techniques has widened the design capabilities in a plethora of applications. In particular, Fused Deposition Modelling (FDM) has concentrated lots of interest by researchers due to its apparently simple manufacturing of components. Indeed, many investigators have work on the experimental testing to retrieve the elastic properties of materials employed for 3D printed, such as Nylon, Onyx or PEEK. Furthermore, numerical testing has also been conducted to predict the aforementioned properties, allowing to reduce the costs of an engineering project. However, to the authors’ knowledge, very little investigation has faced the numerical simulation of actually 3D printed components, such as plates or beams. To fill that gap, this work shows some preliminary results on the mechanical performance of additive-manufactured parts, and how these properties may be affected by printing parameters, such as infill density, number of walls, or curvilinear fibre paths deposition. For doing so, high-order numerical models are derived by means of the Carrera Unified Formulation (CUF), which permits to obtain low- to high-order structural theories in a hierarchic and consistent manner, and has demonstrated its suitability for solving several mechanical applications
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Microscale thermo-elastic analysis of composite materials by high-order geometrically accurate finite elements
No full textThe present work proposes a new approach for conducting thermo-elastic micromechanical analysis. It relies on the use of high-order and geometrically accurate beam finite elements to model the microstructures. The governing equations of the micromechanics models involving the unit cell concept are derived through the Mechanics of Structure Genome (MSG). MSG allows multiscale analysis where global and local scales are decoupled and provides the constitutive information and local fields without needing ad hoc assumptions or requiring different loading steps. The high-order beam elements are derived instead by means of the well-known Carrera Unified Formulation (CUF). These advanced models provide a level of accuracy comparable to conventional solid elements with a fraction of the computational effort. Depending on the problem considered, the cross-section of the refined beam model is modelled by a set of Legendre polynomials, whilst the main direction of the representative unit cell is discretised using one-dimensional (1D) finite elements. Additionally, a non-isoparametric mapping technique allows a perfect description of the microstructural constituents. The present approach enables the resolution of both thermo-elastic homogenisation problems and the recovery of local stress fields through a single run of a CUF-MSG-based code. Several numerical examples compared with numerous other representative solutions of fibre and particle reinforced composites are conducted in order to demonstrate the validity and the efficiency of the presented methodology
Smart microdevices for nutraceutical-controlled delivery
No full text[ES] La presente tesis doctoral, titulada "Microportadores inteligentes para la liberación controlada de sustancias de interés nutracéutico", se centra en el diseño y evaluación de sistemas híbridos orgánico-inorgánicos para proteger y liberar controladamente compuestos bioactivos. Dichos sistemas están basados en (i) materiales de sílice, principalmente partículas mesoporosas, como soporte inorgánico para almacenar y proteger la carga bioactiva; y (ii) una capa externa de biomoléculas como puerta molecular, que regula la liberación de la carga ante ciertos estímulos.
En el primer capítulo de la tesis se describe el ácido oleico como puerta molecular. Este capítulo se subdivide en tres artículos diferentes, con distintos objetivos. En el primer artículo se emplea por primera vez el ácido oleico como puerta molecular de un soporte mesoporoso, cargado con la molécula modelo rodamina B. El material preparado es capaz de proteger la carga en las condiciones presentes en la boca y en el estómago, e inducir su liberación en el intestino con la acción surfactante de las sales biliares. El sistema se ha empleado para la liberación de vitamina B2, demostrando así la utilidad del diseño para la protección y liberación controlada de nutracéuticos. El segundo artículo evalúa la efectividad de esta puerta molecular en diferentes tipos de partículas mesoporosas de sílice, con diversos tamaños y estructuras de poro (MCM-41, MCM-48, SBA-15 y UVM-7). En todos los sistemas estudiados, la puerta molecular es capaz de mantener protegidas las moléculas cargadas, y liberarlas ante la presencia de sales biliares. El sólido basado en la estructura de UVM-7 se validó in vivo, observándose un retraso en la absorción intestinal de la rodamina gracias a su encapsulación. Por último, el tercer artículo incluido en este capítulo ha estudiado la posibilidad de incorporar puertas moleculares en filosilicatos. Se ha conseguido la protección y liberación controlada de biomoléculas de gran tamaño implicadas en el metabolismo humano (vitamina B12 y hematina) empleando filosilicatos funcionalizados con ácido oleico como puerta molecular.
El segundo capítulo describe por primera vez el uso de la proteína zeína (prolamina de maíz) como puerta molecular. La presencia de la prolamina de maíz inhibe la salida de los compuestos antimicrobianos encapsulados (timol, carvacrol y cinamaldehído) liberándolos en presencia de las enzimas proteolíticas excretadas durante el crecimiento bacteriano. De todos los materiales desarrollados, el sistema cargado con cinamaldehído ha demostrado una inhibición del crecimiento de E. coli superior a la del compuesto libre.
Finalmente, el tercer capítulo estudia la efectividad de la lactosa como puerta molecular para proteger aceites esenciales y liberarlos solo en las condiciones presentes en el intestino. Se han preparado tres materiales diferentes basados en MCM-41, cargados con timol, eugenol y cinamaldehído, y funcionalizados con lactosa para inhibir la salida de los compuestos. La acción enzimática de la lactasa secretada en el intestino es capaz de hidrolizar la puerta molecular en los correspondientes monosacáridos, liberando la carga a lo largo del lumen intestinal. Los microdispositivos diseñados han sido validados in vitro con células Caco-2, donde se ha observado el aumento de la capacidad citotóxica del cinamaldehído y la disminución de la permeabilidad a través del modelo de membrana intestinal gracias a su encapsulación. Finalmente, el microdispositivo cargado con cinamaldehído se ha validado in vivo ratificándose la disminución de la permeabilidad del compuesto y su mayor permanencia en el lumen intestinal.
Así, la presente tesis doctoral ha demostrado la posibilidad de emplear biomoléculas sencillas de grado alimentario como puertas moleculares sobre diversos materiales de sílice. Estos nuevos sistemas han permitido proteger y liberar control[CA] La present tesi doctoral, titulada "Microportadors intel·ligents per a l'alliberament controlat de substàncies d'interès nutracèutic", se centra en el disseny i avaluació de sistemes híbrids orgànic-inorgànics per a la protecció i alliberament controlat de compostos bioactius. Aquests sistemes estan basats en (i) materials de sílice, principalment partícules mesoporoses, com a suport inorgànic per emmagatzemar i protegir la càrrega bioactiva; i (ii) una capa externa de biomolècules com a porta molecular, que regula l'alliberament d'aquesta càrrega davant de determinats estímuls.
En el primer capítol de la tesi es descriu l'àcid oleic com a porta molecular. Aquest capítol se subdivideix en tres articles diferents, amb objectius diferents. En el primer article s'empra per primera vegada l'àcid oleic com a porta molecular d'un suport mesoporós, carregat amb la molècula model rodamina B. El material preparat és capaç de protegir la càrrega en les condicions presents a la boca i a l'estómac, i induir el seu alliberament a l'intestí amb l'acció surfactant de les sals biliars. El sistema s'ha emprat per a l'alliberament de vitamina B2, demostrant així la utilitat del disseny per a la protecció i alliberament controlat de nutracèutics. El segon article avalua l'efectivitat d'aquesta porta molecular en diferents tipus de partícules mesoporoses de sílice, amb diverses mides i estructures de porus (MCM-41, MCM-48, SBA-15 i UVM-7). En tots els sistemes estudiats, la porta molecular és capaç de mantindre protegides les molècules carregades, i alliberar-les davant la presència de sals biliars. El sòlid basat en l'estructura de UVM-7 es validà in vivo, observant-se un retard en l'absorció intestinal de la rodamina gràcies a la seua encapsulació. Finalment, en el tercer article inclòs en aquest capítol s'ha estudiat la possibilitat d'incorporar portes moleculars en fil·losilicats. S'ha aconseguit la protecció i alliberament controlat de biomolècules de grans dimensions implicades en el metabolisme humà (vitamina B12 i hematina) emprant fil·losilicats funcionalitzats amb àcid oleic com a porta molecular.
El segon capítol descriu per primera vegada l'ús de la proteïna zeïna (prolamina de dacsa) com a porta molecular. La presència de la prolamina de dacsa inhibeix la sortida dels compostos antimicrobians encapsulats (timol, carvacrol i cinamaldèhid) alliberant-los en presència dels enzims proteolítics excretades durant el creixement bacterià. De tots els materials desenvolupats, el sistema carregat amb cinamaldèhid ha demostrat una inhibició de l'creixement d'E. coli superior a la del compost lliure.
Finalment, el tercer capítol estudia l'efectivitat de la lactosa com a porta molecular per protegir olis essencials i alliberar-los només en les condicions presents a l'intestí. S'han preparat tres materials diferents basats en MCM-41, carregats amb timol, eugenol i cinamaldèhid, i funcionalitzats amb lactosa per inhibir l'eixida dels compostos. L'acció enzimàtica de la lactasa secretada a l'intestí és capaç d'hidrolitzar la porta molecular en els corresponents monosacàrids, alliberant la càrrega al llarg del lumen intestinal. Els microdispositius dissenyats s'han validat in vitro amb cèl·lules Caco-2, on s'observà l'augment de la capacitat citotòxica del cinamaldèhid i la disminució de la permeabilitat a través del model de membrana intestinal gràcies a la seua encapsulació. Finalment, el microdispositiu carregat amb cinamaldèhid s'ha validat in vivo ratificant la disminució de la permeabilitat del compost i la seua major permanència al lumen intestinal.
Així, la present tesi doctoral ha demostrat la possibilitat d'emprar biomolècules senzilles de grau alimentari com portes moleculars sobre diversos materials de sílice. Aquests nous sistemes han permès protegir i alliberar controladament diferents nutracèutics, millorant així la seua biodisponibilitat.[EN] This PhD thesis, entitled "Smart microdevices for nutraceutical-delivery", is focused on the design and evaluation of organic-inorganic hybrid systems for the protection and controlled release of bioactive molecules. These systems are based on (i) silica materials, mainly mesoporous particles, as inorganic support to store and protect the bioactive cargo; and (ii) an outer layer of biomolecules that regulate the payload release triggered by certain stimuli.
In the first chapter of the thesis oleic acid is described as a molecular gate. This chapter is subdivided into three different articles, with different objectives. In the first article, oleic acid is used for the first time as molecular gate of a mesoporous support, loaded with the rhodamine B model molecule. The designed material is capable of protecting the cargo under the conditions present in the mouth and stomach, and inducing its release in the small intestine with the surfactant action of bile salts. The system has been used for the release of vitamin B2, thus demonstrating the validity of the design for the protection and controlled release of nutraceuticals. The second article evaluates the effectiveness of this molecular gate in different types of mesoporous silica particles, with different sizes and pore structures (MCM-41, MCM-48, SBA-15 and UVM-7). In all the systems studied, the molecular gate is capable of keeping cargo molecules protected and releasing them in the presence of bile salts. The solid based on the structure of UVM-7 was validated in vivo, observing a delay in the intestinal absorption of rhodamine thanks to its encapsulation. Lastly, the third article included in this chapter has studied the possibility of incorporating molecular gates onto phyllosilicates. The protection and controlled release of large biomolecules involved in human metabolism (vitamin B12 and hematin) have been achieved using phyllosilicates functionalized with oleic acid as molecular gate.
The second chapter describes for the first time the use of the protein zein (corn prolamine) as a molecular gate. The presence of corn prolamine inhibits the release of encapsulated antimicrobial compounds (thymol, carvacrol and cinnamaldehyde) releasing them in the presence of the proteolytic enzymes excreted during bacterial growth. Among all the materials developed, the cinnamaldehyde-loaded system has shown greater inhibition of E. coli growth than the free compound.
Finally, the third chapter studies the effectiveness of lactose as a molecular gate to protect essential oils and release them only under the conditions present in the intestine. Three different materials based on MCM-41 loaded with thymol, eugenol, and cinnamaldehyde, and functionalized with lactose to inhibit the release of the compounds have been prepared. The enzymatic action of the lactase secreted in the intestine is capable of hydrolyzing the molecular gate into the corresponding monosaccharides, thus releasing the cargo along the intestinal lumen. The designed microdevices have been validated in vitro with Caco-2 cells, where an increase in the cytotoxic capacity of cinnamaldehyde and a decrease in permeability through the intestinal membrane model have been observed thanks to its encapsulation. Finally, the cinnamaldehyde-loaded microdevice has been validated in vivo, confirming the decrease in the permeability of the compound and its greater permanence in the intestinal lumen.
Thus, the present PhD thesis has demonstrated the possibility of using simple food-grade biomolecules as gatekeepers on various silica materials. These new systems have allowed the protection and controlled release of different nutraceuticals, thus improving their bioavailability.The authors also thank the Electron Microscopy Service at the UPV for support. The authors also thank Prof. Pedro Amorós for his explanations and
guidance on the knowledge of phyllosilicates.Poyatos Racionero, E. (2020). Smart microdevices for nutraceutical-controlled delivery [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/159247TESI
Sensitivity analysis of variable stiffness composite plates by CUF-based layerwise models
No full textComposite materials are increasingly used in many engineering fields thanks to their lightness and high mechanical properties. Currently, many research activities are focused on the optimization of structures using conventional composite materials, i.e. Constant Stiffness Composite Materials (CSCM). High-performance structures, such as those employed in aerospace engineering, could be further enhanced by using modern automated fibre placement machines, which brought to the emergence of a new class of composites; namely, the Variable Angle Tow (VAT) composites. The main idea of VAT composites is to have an increased freedom in the tailoring of the material properties since the fibres are no longer restricted to be straight and can actually have a curvilinear pattern within each layer. This work presents some sensitivity analyses based on a refined model developed in the domain of the Carrera Unified Formulation (CUF), which has been already demonstrated to be effective for the analysis of VAT structures. Essentially, CUF makes use of arbitrarily high-order kinematics to relax 3D elasticity equations into 1D or 2D theories [1]. Lagrange polynomials have been employed in this work to describe the cross-section variables, because refined 1D models are utilized, obtaining a layer-wise description of the primary variables. Layer-wise approach confirmed the highest accuracy in comparison with equivalent-single-layer models, also for VAT as demostrated by Demasi et al. [2]. The main objective is to study the effect of manufacturing processes on the mechanical response of VAT. Particular attention is focussed on the misalignments of the fibres, which ultimately affect the global properties of the structure. Such misalignment fields are generated by means of stochastic field theory exploiting the correlation matrix decomposition (CMD) method (like those presented in Broek et al. [3]), where relative distances between structural nodes are considered. Several numerical examples show the importance of using a layer-wise approach for sensitivity analysis and design of VAT composite panels, especially when buckling response and redistribution of stress fields are considere
Accurate stress analysis of variable angle tow shells by high-order equivalent-single-layer and layer-wise finite element models
No full textNew concepts of lightweight components are conceived nowadays thanks to the advances in the manufacture of composite structures. For instance, mature technologies such as Automatic Fibre Placement (AFP) are employed in the fabrication of structural parts where fibres are steered along curvilinear paths, namely variable angle tow (VAT), which can enhance the mechanical performance and alleviate the structural weight. This is of utmost importance in the aerospace field, where weight savings are one of the main goals. For that reason, shell structures are commonly found in the aerospace industry because of their capabilities of supporting external loadings. Straight-fibre composite shell structures have been studied in recent decades and, now, spatially varying composite shells are attracting the attention of manufacturers. This work analyses the mechanical behaviour of VAT composite shells subjected to different external loadings and boundary conditions. The Carrera Unified Formulation (CUF) is employed to obtain the different structural models in a systematic and hierarchic manner. The outcomes of such numerical models are discussed and compared with commercial software Abaqus
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