Additive Manufacturing with RepRap Methodology: Current Situation and Future Prospects

In February 2004, Adrian Bowyer, from the University of Bath, began an open initiative called RepRap, with the purpose of creating an open source rapid prototyping machine which, moreover, could replicate itself. This article analyzes the current status of the RepRap initiative, commenting the basic components of RepRap machines, the differences between the different 3D printers developed by the RepRap community so far, and the technical possibilities that opens this technology from the engineering point of view. In addition we propose some improvements that could be perfectly feasible in the short term. For this purpose, the assembly of a RepRap Mendel Prusa was performed, but with some modifications.Mechanical Engineerin

Bricking: A New Slicing Method to Reduce Warping

AbstractFused Deposition Modeling (FDM) is the most used 3D printing technology. In this technology, 3D pieces are built warming and extruding thermoplastic through a nozzle. When the thermoplastic gets cold, internal stresses may generate deformations, mainly in corners. In this paper we describe a method for reduce these deformations (called warping), splitting pieces in hexagonal or squared bricks spatially locked. We have developed and tested an application that calculates the necessary GCODE to build the bricking piece directly, and we have measured a significant reduction in warp deformations

Bioactive pectic polysaccharides from bay tree pruning waste: Sequential subcritical water extraction and application in active food packaging

The potential isolation of bio-active polysaccharides from bay tree pruning waste was studied using sequential subcritical water extraction using different time-temperature combinations. The extracted polysaccharides were highly enriched in pectins while preserving their high molecular mass (10–100 kDa), presenting ideal properties for its application as additive in food packaging. Pectin-enriched chitosan films were prepared, improving the optical properties (=95% UV-light barrier capacity), antioxidant capacity (?95% radical scavenging activity) and water vapor permeability (=14 g·Pa-1·s-1·m-1·10-7) in comparison with neat chitosan-based films. Furthermore, the antimicrobial activity of chitosan was maintained in the hybrid films. Addition of 10% of pectins improved mechanical properties, increasing the Young's modulus 12%, and the stress resistance in 51%. The application of pectin-rich fractions from bay tree pruning waste as an additive in active food packaging applications, with triple action as antioxidant, barrier, and antimicrobial has been demonstrated.Authors would like to thank the Spanish Ministry of Science and Innovation (Ramon y Cajal contract RYC-2015-17109) and Universidad de Cordoba, ´ Spain (Predoctoral Grant 2019) for the financial support during this work

Cellulose Nanofibers and Other Biopolymers for Biomedical Applications. A Review

Biopolymers are materials synthesised or derived from natural sources, such as plants, animals, microorganisms or any other living organism. The use of these polymers has grown significantly in recent years as industry shifts away from unsustainable fossil fuel resources and looks towards a softer and more sustainable environmental approach. This review article covers the main classes of biopolymers: Polysaccharides, proteins, microbial-derived and lignin. In addition, an overview of the leading biomedical applications of biopolymers is also provided, which includes tissue engineering, medical implants, wound dressings, and the delivery of bioactive molecules. The future clinical applications of biopolymers are vast, due to their inherent biocompatibility, biodegradability and low immunogenicity. All properties which their synthetic counterparts do not share

Determinación de las curvas de estado último de agotamiento en secciones rectangulares de hormigón armado con armadura simétrica o asimétrica

This paper shows an algorithm that allows to determine the M, N curves at ultimate limit state for rectangular sections of reinforced concrete, with simetric and non-simetric reinforcement, for any kind of concrete, cover and steel reinforcement. The use of this program, based on the parabolic-rectangular model, makes innecessary to utilize of theoretical abacus and tables. It's a valid procedure to check concrete structures in real conditions of stress and reinforcement.Se describe un programa de ordenador que permite la determinación de las curvas M, N de agotamiento de secciones rectangulares de hormigón armado, con armadura simétrica o asimétrica, cualquiera que sea el tipo de hormigón y el recubrimiento mecánico de las armaduras para aceros normales. El programa, que se basa en el método de cálculo de la Parábola-Rectángulo, permite prescindir del empleo de ábacos teóricos y supone un procedimiento válido para la comprobación de estructuras de hormigón en condiciones reales de carga y armado

Los nuevos retos de la industria farmacéutica

Diverse challenges of the modern pharmaceutical industry are analysed in this papero High competitiveness in the pharmaceutical sector and new regulations dictated by the different governments or organizations in charge of watching over public health have generated the need to devise new ways in the discovery of new drugs. On one hand, the rational drug design has acquired a leading role and on the other, the development of robotics has prompted the development of combinatorial chemistry and high production screening. The pharmaceutical industry of the future must be more dynamic and innovating. One of the observed phenomena has been the merging of a number of pharmaceutical fusions faced to the necessity of reducing production costs.En este trabajo se analizan los distintos retos de la industria farmacéutica moderna. La elevada competitividad del sector farmacéutico y las nuevas regulaciones dictadas por los diferentes gobiernos u organismos encargados de velar por la salud pública han generado la necesidad de idear nuevas vías en el descubrimiento de nuevos medicamentos. Por una parte, el diseño racional de fármacos ha adquirido un enorme protagonismo y, por otra, el desarrollo de la robótica han potenciado el desarrollo de la química combinatoria y del tamizado de alta producción. La futura industria farmacéutica debe ser más dinámica e innovadora. Uno de sus fenómenos observados ha sido el elevado número de fusiones de empresas farmacéuticas, ante la necesidad de reducir los costes de los productos

SHARDS: A global view of the star formation activity at z∼ 0.84 and z∼ 1.23

et al.In this paper, we present a comprehensive analysis of star-forming galaxies (SFGs) at intermediate redshifts (z ∼ 1). We combine the ultra-deep optical spectro-photometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) with deep UV-to-FIR observations in the GOODS-N field. Exploiting two of the 25 SHARDS medium-band filters, F687W17 and F823W17, we select [O ii] emission line galaxies at z ∼ 0.84 and z ∼ 1.23 and characterize their physical properties. Their rest-frame equivalent widths (EW([O ii])), line fluxes, luminosities, star formation rates (SFRs), and dust attenuation properties are investigated. The evolution of EW([O ii]) closely follows the SFR density evolution of the universe, with a trend of EW([O ii]) (1 + z) up to redshift z ≃ 1, followed by a possible flattening. The SF properties of the galaxies selected on the basis of their [O ii] emission are compared with complementary samples of SFGs selected by their MIR and FIR emission, and also with a general mass-selected sample of galaxies at the same redshifts. We demonstrate observationally that the UVJ diagram (or, similarly, a cut in the specific SFR) is only partially able to distinguish the quiescent galaxies from the SFGs. The SFR-M relation is investigated for the different samples, yielding a logarithmic slope ∼1, in good agreement with previous results. The dust attenuations derived from different SFR indicators (UV(1600), UV(2800), [O ii], IR) are compared and show clear trends with respect to both the stellar mass and total SFR, with more massive and highly star-forming galaxies being affected by stronger dust attenuation.The work of A.C. is supported by the STARFORM Sinergia Project funded by the Swiss National Science Foundation, and also benefited from a MERAC Funding and Travel Award. P.G.P.-G. acknowledges support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2012-31277. A.V.G. acknowledges support from the ERC via an Advanced Grant under grant agreement no. 321323-NEOGAL. N.C. acknowledges support from the Spanish Ministry of Economy and Competitiveness under grant AYA2013-46724-P. A.A.H. and A.H.C. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2012-31447, which is partly funded by the FEDER program. A.J.C. is a Ramón y Cajal Fellow of the Spanish Ministry of Science and Innovation and acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2012-30789, partly funded by the FEDER program.Peer Reviewe

SHARDS: A global view of the star formation activity at z~0.84 and z~1.23

In this paper, we present a comprehensive analysis of star-forming galaxies (SFGs) at intermediate redshifts (z~1). We combine the ultra-deep optical spectro-photometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) with deep UV-to-FIR observations in the GOODS-N field. Exploiting two of the 25 SHARDS medium-band filters, F687W17 and F823W17, we select [OII] emission line galaxies at z~0.84 and z~1.23 and characterize their physical properties. Their rest-frame equivalent widths (EW$_{\mathrm{rf}}$([OII])), line fluxes, luminosities, star formation rates (SFRs) and dust attenuation properties are investigated. The evolution of the EW$_{\mathrm{rf}}$([OII]) closely follows the SFR density evolution of the universe, with a trend of EW$_{\mathrm{rf}}$([OII])$\propto$(1+z)$^3$ up to redshift z~1, followed by a possible flattening. The SF properties of the galaxies selected on the basis of their [OII] emission are compared with complementary samples of SFGs selected by their MIR and FIR emission, and also with a general mass-selected sample of galaxies at the same redshifts. We demonstrate observationally that the UVJ diagram (or, similarly, a cut in the specific SFR) is only partially able to distinguish the quiescent galaxies from the SFGs. The SFR-M$_*$ relation is investigated for the different samples, yelding a logarithmic slope ~1, in good agreement with previous results. The dust attenuations derived from different SFR indicators (UV(1600), UV(2800), [OII], IR) are compared and show clear trends with respect to both the stellar mass and total SFR, with more massive and highly star-forming galaxies being affected by stronger dust attenuation.Comment: Replaced to match the accepted version (24 pages, 1 table, 17 figures). Published in ApJ, 812, 155 (2015): http://stacks.iop.org/0004-637X/812/15

Boro-nitriding coating on pure iron by powder-pack boriding and nitriding processes

To alleviate spallation and crack difficulties exhibited by a borided metallic surface when it is subjected to a normal, heavy and sliding load under dry conditions, a boron nitride coating was produced on pure iron in two stages: boriding the iron surface at 950 °C for 6 h and then nitriding the pre-borided iron at 550 °C for 6 h. The powder-pack technique was used in both stages. XRD measurements confirmed that the grown layers were nitrides and duplex borides. The produced diffusion of the layers reached 240 µm in depth as measured by SEM images. The measured microhardness across the case favoured the interphase cohesion between the iron nitrides and iron borides layers. Consequently, the multicomponent coating exhibited superior wear resistance to an applied normal load under dry sliding contact conditions in comparison to borided iron