Three-dimensional printed polycaprolactone-microcrystalline cellulose scaffolds

Microcrystalline cellulose (MCC) is proposed in this study as an additive in polycaprolactone (PCL) matrices to obtain three-dimensional (3D) printed scaffolds with improved mechanical and biological properties. Improving the mechanical behavior and the biological performance of polycaprolactone-based scaffolds allows to increase the potential of these structures for bone tissue engineering. Different groups of samples were evaluated in order to analyze the effect of the additive in the properties of the PCL matrix. The concentrations of MCC in the groups of samples were 0, 2, 5, and 10% (w/w). These combinations were subjected to a thermogravimetric analysis in order to evaluate the influence of the additive in the thermal properties of the composites. 3D printed scaffolds were manufactured with a commercial 3D printer based on fused deposition modelling. The operation conditions have been established in order to obtain scaffolds with a 0/90° pattern with pore sizes between 450 and 500 µm and porosity values between 50 and 60%. The mechanical properties of these structures were measured in the compression and flexural modes. The scaffolds containing 2 and 5% MCC have higher flexural and compression elastic modulus, although those containing 10% do not show this reinforcement effect. On the other hand, the proliferation of sheep bone marrow cells on the proposed scaffolds was evaluated over 8 days. The results show that the proliferation is significantly better (p < 0.05) on the group of samples containing 2% MCC. Therefore, these scaffolds (PCL:MCC 98:2) have suitable properties to be further evaluated for bone tissue engineering applications

Tunability of polycaprolactone hydrophilicity by carboxymethyl cellulose loading

[EN] Carboxymethyl cellulose (CMC) is herein proposed as additive in polycaprolactone (PCL) matrices to obtain composites with tunable hydrophilicity. This composite material can be obtained by compression molding. The thermogravimetric degradation profile, the FTIR spectra, values of the water contact angle (WCA), water and phosphate-buffered saline uptake values, and the results of a cytotoxicity assessment are presented herein. The concentrations of CMC in the groups of samples are 0, 2, 5, 10, and 20%. The WCA on the prewetted state decreases proportionally to the concentration of the additive. These results evidence the possibility of obtaining a PCL-based composite with tunable hydrophilicity. Besides, the biological assessment does not reveal any cytotoxic effects. Therefore, the addition of CMC entails an innovative strategy to control the water affinity of PCL in biomedical applications where such feature is required to improve diffusion of biological medium through, or accelerate degradation by hydrolysis.M.E.A.D. expresses her gratitude for the funding through the PhD Grant Program of ULPGC (Code of the grant: PIFULPGC-2014-ING-ARQU-2). J.A.G.T., A.V.L., and G.V.F. acknowledge the support of the Spanish Ministry of Economy and Competitiveness (MINECO) through the project DPI2015-65401-C3-2-R (including the FEDER financial support).Alemán-Domínguez, M.; Ortega, Z.; Benítez, A.; Vilariño, G.; Gómez-Tejedor, JA.; Vallés Lluch, A. (2017). Tunability of polycaprolactone hydrophilicity by carboxymethyl cellulose loading. Journal of Applied Polymer Science. 135(14):1-6. https://doi.org/10.1002/app.46134S161351

Microcrystalline cellulose as filler in polycaprolactone matrices

Polycaprolactone is a biomaterial widely used for tissue engineering applications. However, its hydrophobicity hinders cell attachment and proliferation on its surface. In this study microcrystalline cellulose has been proposed as a functional filler for polycaprolactone matrices expected to improve these properties. Composite material samples containing 0, 2, 5, 10 and 20% w/w of microcrystalline cellulose have been manufactured by compression molding and evaluated in terms of their mechanical properties, swelling behavior, water contact angle values and sheep mesenchymal cells viability. The results confirm that the presence of the additive is able to increase the swelling ability of the material (the samples containing 20% w/w of additive are able to absorb an amount of water 6 times higher than the value for polycaprolactone ones), the Young’s modulus (from 224±14 MPa for polycaprolactone to 388±30 MPa for the composites containing 20% of microcrystalline cellulose) and the bioaffinity of polycaprolactone based composite materials

Towards a Classification of Rough Set Bireducts

Size reduction mechanisms are very important in several mathematical fields. In rough set theory, bireducts arose to reduce simultaneously the set of attributes and the set of objects of the considered dataset, providing subsystems with the minimal sets of attributes that connect the maximum number of objects preserving the information of the original dataset. This paper presents the main properties of bireducts and how they can be used for removing inconsistencies. © 2020, Springer Nature Switzerland AG

Gamma photometric redshifts for long gamma-ray bursts

It is known that the soft tail of the gamma-ray bursts' spectra show excesses from the exact power-law dependence. In this article we show that this departure can be detected in the peak flux ratios of different BATSE DISCSC energy channels. This effect allows to estimate the redshift of the bright long gamma-ray bursts in the BATSE Catalog. A verification of these redshifts is obtained for the 8 GRB which have both BATSE DISCSC data and measured optical spectroscopic redshifts. There is good correlation between the measured and esti redshifts, and the average error is $\Delta z \approx 0.33$. The method is similar to the photometric redshift estimation of galaxies in the optical range, hence it can be called as "gamma photometric redshift estimation". The estimated redshifts for the long bright gamma-ray bursts are up to $z \simeq 4$. For the the faint long bursts - which should be up to $z \simeq 20$ - the redshifts cannot be determined unambiguously with this method.Comment: accepted in A&A, 7 pages incl. 7 figure

Contenido de carbono orgánico y características texturales de los sedimentos del sistema costero lagunar Chantuto-Panzacola, Chiapas

Seasonal and spatial distribution of surface sediments from the Chantuto-Panzacola coastal lagoon system were analyzed, including organic carbon (O.C.) content, during the years 1997 to 2003. Surface sediments were taken from 10 sites by means of a small van Veen grab sampler (3L) and sediment composition (sand, silt and clay components) was obtained by pipette analysis. There were differences in the sediments O.C. inbetween dry and wet seasons, with higher levels corresponding to the latter and showing that O.C. contributions to the system come from autochthonous and allochthonous sources through fluvial drainage. O.C. levels throughout the lagoons were highest in stations 4 (Chantuto), 5 and 6 (Panzacola), while station 1 (the entrance, influenced by marine conditions) showed lower values. Sediment texture values were markedly heterogenous throughout years, seasons and stations. The effect of tropical storm Javier was found to be significant in incrementing the sand content in almost the entirety of the system, as well as decreasing the O.C. contents. The 2003 O.C. values were similar to those measured in 1997; on the other hand, continuous change in grain size has been the norm, affecting mainly those areas where dredging activities have taken place since 2001.En este estudio se analizó la distribución textural estacional y espacial de los sedimentos superficiales y el contenido de carbono orgánico (C.O.) en ellos en el sistema costero Chantuto-Panzacola durante el período de 1997 a 2003. Los sedimentos superficiales se colectaron en 10 estaciones de muestreo con una draga tipo van Veen (3L). Se determinó el carbono orgánico (C.O.%) y se analizó la distribución textural (arena, limo, arcilla) con el método del pipeteo. Hubo diferencias significativas de C.O. en los sedimentos entre las estaciones de secas y de lluvias. El contenido de C.O. fue mayor en los meses asociados a la época de lluvias, mostrando que el aporte de C.O. proviene de fuentes tanto autóctonas, como alóctonas (por medio de la descarga fluvial). La distribución espacial de C.O. a través de las lagunas fue mayor principalmente en la E4 (Chantuto) - E6 - E5 (Panzacola), mientras que en la E1 (en la boca con influencia marina) fue mucho menor debido al flujo de agua de mar que mantiene en suspensión la materia particulada. La distribución del tamaño de grano fue muy heterogénea entre años, épocas climáticas y estaciones en las lagunas ya que varió de limo-arenoso y arena-limo-arcilloso a arcilla-arenosa. El efecto de la tormenta tropical Javier de septiembre de 1998 fue significativo, con un incremento en la proporción de arenas y disminución del C.O. en casi todo el sistema lagunar. Para el año 2003, el porcentaje de C.O. fue similar al de 1997, sin embargo, la granulometría continúa modificándose, sobre todo en las áreas donde se han realizado dragados desde el año 2001

Photometric redshifts from reconstructed QSO templates

From SDSS commissioning photometric and spectroscopic data, we investigate the utility of photometric redshift techniques to the task of estimating QSO redshifts. We consider empirical methods (e.g. nearest-neighbor searches and polynomial fitting), standard spectral template fitting and hybrid approaches (i.e. training spectral templates from spectroscopic and photometric observations of QSOs). We find that in all cases, due to the presence of strong emission-lines within the QSO spectra, the nearest-neighbor and template fitting methods are superior to the polynomial fitting approach. Applying a novel reconstruction technique, we can, from the SDSS multicolor photometry, reconstruct a statistical representation of the underlying SEDs of the SDSS QSOs. Although, the reconstructed templates are based on only broadband photometry the common emission lines present within the QSO spectra can be recovered in the resulting spectral energy distributions. The technique should be useful in searching for spectral differences among QSOs at a given redshift, in searching for spectral evolution of QSOs, in comparing photometric redshifts for objects beyond the SDSS spectroscopic sample with those in the well calibrated photometric redshifts for objects brighter than 20th magnitude and in searching for systematic and time variable effects in the SDSS broad band photometric and spectral photometric calibrations.Comment: 21 pages, 9 figures, LaTeX AASTeX, submitted to A

Strongly anisotropic spin relaxation in graphene/transition metal dichalcogenide heterostructures at room temperature

Graphene has emerged as the foremost material for future two-dimensional spintronics due to its tuneable electronic properties. In graphene, spin information can be transported over long distances and, in principle, be manipulated by using magnetic correlations or large spin-orbit coupling (SOC) induced by proximity effects. In particular, a dramatic SOC enhancement has been predicted when interfacing graphene with a semiconducting transition metal dechalcogenide, such as tungsten disulphide (WS$_2$). Signatures of such an enhancement have recently been reported but the nature of the spin relaxation in these systems remains unknown. Here, we unambiguously demonstrate anisotropic spin dynamics in bilayer heterostructures comprising graphene and WS$_2$. By using out-of-plane spin precession, we show that the spin lifetime is largest when the spins point out of the graphene plane. Moreover, we observe that the spin lifetime varies over one order of magnitude depending on the spin orientation, indicating that the strong spin-valley coupling in WS$_2$ is imprinted in the bilayer and felt by the propagating spins. These findings provide a rich platform to explore coupled spin-valley phenomena and offer novel spin manipulation strategies based on spin relaxation anisotropy in two-dimensional materials

Precise measurement of near-barrier 8He+208Pb elastic scattering : comparison with 6He

Dramatic differences in the elastic scattering of the neutron rich nuclei 6He and 8He are found when new high quality data for the 8He+208Pb system are compared with previously published 6He+208Pb data at the same laboratory frame incident energy. The new 8He data are of the same level of detail as for stable beams. When comparing them with those previously obtained for 6He+208Pb at the same energy, it is possible to determine from the data alone that 6He has a much longer range absorption than 8He. However, both nuclei show significant absorption beyond their strong absorption radii. While it has been known for a long time that elastic scattering at energies around the barrier only determines the optical potential over a small distance in radial space, typically ±0.5 fm or so, both the 6He and the 8He imaginary potentials obtained from various optical model fits to these data are the same over a much wider range of ±1.5 fm.The authors would like to thank the staff of the GANIL accelerator facility for providing the high quality 8He beam. This work was supported in part by Grant No. FPA2010-22131-C02-01 (FINURA) and Grant No. FPA2013-47327-C2-1-R from the Spanish Ministry of Economy and Competitiveness, UNAM-PAPIIT IA101616 (Mexico), Grant No. N202 033637 from the Ministry of Science and Higher Education of Poland, and Contract No. EUI2009-04163 (EUROGENESIS) from the European Science Foundation

\b{eta}-delayed three-proton decay of 31Ar

The beta decay of 31Ar, produced by fragmentation of a 36Ar beam at 880 MeV/nucleon, was investigated. Identified ions of 31Ar were stopped in a gaseous time projection chamber with optical readout allowing to record decay events with emission of protons. In addition to \b{eta}-delayed emission of one and two protons we have clearly observed the beta-delayed three-proton branch. The branching ratio for this channel in 31Ar is found to be 0.07(2)%.Comment: 5 pages, 3 figures, submitted to Physical Rev.