Engineering cartilage like tissue using polymeric systems derived from 2-ethyl-2-pyrrolidone-methacrylate combined with hyaluronic acid

Hydrogels are potential candidates for Tissue engineering (TE), because of their water content, transport properties, and tissue like physical and chemical behaviour. This project was based on the production and characterization of implantable stimuli responsive scaffolds made of hyaluronic acid (HA) that presents a high water retention character, in combination with 2-ethyl (2-pyrrolidone) methacrylate (EPM), possessing temperature-dependent solubility in water, by bulk polymerization. [...]info:eu-repo/semantics/publishedVersio

Synthesis and characterization of sensitive hydrogels based on semi- interpenetrated networks of poly 2-ethyl-(2-pyrrolidone) methacrylate and hyaluronic acid

Sensitive hydrogels attract interest due to their soft wet appearance and shape response to environmental variations. The synthesis and characterization of semi-interpenetrated hydrogels obtained by radical-induced polymerization of 2-ethyl-(2-pyrrolidone)methacrylate (EPM) in the presence of different concentrations of hyaluronic acid (HA) using N,N′-methylene-bisacrylamide or triethylene glycol dimethacrylate as crosslinker, followed by freeze-drying, are described. Polymeric systems were characterized by NMR, FTIR, SEM, TGA, and DMA. PEPMHA hydrogels' mechanical properties and swelling were found to be intimately related to HA concentration and crosslinker. The swelling response was assessed for temperature and pH variation in order to study the behavior of the hydrogels. We found that the presence of HA in PEPM polymeric systems induced a sensitivity to pH variation rather than temperature. Finally, the biocompatibility profile of the hydrogels was evaluated, using mesenchymal stem cells. Cell adhesion and proliferation results revealed the non-cytotoxicity of the systems. We estimate that PEPMHA hydrogels can be used for applications in tissue engineering and for the controlled release of bioactive compounds.Contract grant sponsor: Marie Curie Early Stage Training Alea Jacta Est; contract grant number: MEST-CT-2004-8104The authors thank David Gomez, Sofia Caridade, and Justyna Chojnacka for their technical support and BIOIBERICA for the supply of hyaluronic acid. This work was carried out under the scope of the European NoE EXPERTISSUES, projects MAT 2007-63355, PTDC/QUI/68804/2006 (FCT), CIBER-BBN and Plan-E 2009-0144. In the memory of Prof. Roberto Sastre

Biomimetic Ca-P coatings Incorporating bisphosphonates produced on starch-based degradable biomaterials

In this study, sodium clodronate, a well-known therapeutic agent from the family of bisphosphonates (BPs), is incorporated in a biomimetic calcium phosphate (CaP) coating, previously formed on the surface of a starch-based biomaterial by a sodium silicate methodology, as a strategy to develop a site-specific drug delivery system for bone tissue regeneration applications. The effects on the resulting CaP coatings were evaluated in terms of morphology, chemistry, and structure. The dissolution of Ca and P from the coating and the release profiles of sodium clodronate was also assessed. As a preliminary approach, this first study also aimed at evaluating the effects of this BP on the viability of a human osteoblastic cell line since there is still little information available on the interaction between BPs and this type of cells. Sodium clodronate was successfully incorporated, at different doses, in the structure of a biomimetic CaP layer previously formed by a sodium silicate process. This type of BPs had a stimulatory effect on osteoblastic activity, particularly at the specific concentration of 0.32 mg/mL. It is foreseen that these coatings can, for instances, be produced on the surface of degradable polymers and then used for regulating the equilibrium on osteoblastic/osteoclastic activity, leading to a controlled regenerative effect at the interface between the biomaterial and bone

Newly Identified Star Clusters in M33. III. Structural Parameters

We present the morphological properties of 161 star clusters in M33 using the Advanced Camera For Surveys Wide Field Channel onboard the Hubble Space Telescope using observations with the F606W and F814W filters. We obtain, for the first time, ellipticities, position angles, and surface brightness profiles for a significant number of clusters. On average, M33 clusters are more flattened than those of the Milky Way and M31, and more similar to clusters in the Small Magellanic Cloud. The ellipticities do not show any correlation with age or mass, suggesting that rotation is not the main cause of elongation in the M33 clusters. The position angles of the clusters show a bimodality with a strong peak perpendicular to the position angle of the galaxy major axis. These results support the notion that tidal forces are the reason for the cluster flattening. We fit King and EFF models to the surface brightness profiles and derive structural parameters including core radii, concentration, half-light radii and central surface brightness for both filters. The surface brightness profiles of a significant number of clusters show irregularities such as bumps and dips. Young clusters (Log age < 8) are notably better fitted by models with no radial truncation (EFF models), while older clusters show no significant differences between King or EFF fits. M33 star clusters seem to have smaller sizes, smaller concentrations, and smaller central surface brightness as compared to clusters in the MW, M31, LMC and SMC. Analysis of the structural parameters presents a age-radius relation also detected in other star cluster systems. The overall analysis shows differences in the structural evolution between the M33 cluster system and cluster systems in nearby galaxies. These differences could have been caused by the strong differences in these various environments.Comment: 30 pages, 12 figures, accepted for publication in MNRA

Testing the chemical tagging technique with open clusters

Context. Stars are born together from giant molecular clouds and, if we assume that the priors were chemically homogeneous and well-mixed, we expect them to share the same chemical composition. Most of the stellar aggregates are disrupted while orbiting the Galaxy and most of the dynamic information is lost, thus the only possibility of reconstructing the stellar formation history is to analyze the chemical abundances that we observe today. Aims. The chemical tagging technique aims to recover disrupted stellar clusters based merely on their chemical composition. We evaluate the viability of this technique to recover co-natal stars that are no longer gravitationally bound. Methods. Open clusters are co-natal aggregates that have managed to survive together. We compiled stellar spectra from 31 old and intermediate-age open clusters, homogeneously derived atmospheric parameters, and 17 abundance species, and applied machine learning algorithms to group the stars based on their chemical composition. This approach allows us to evaluate the viability and efficiency of the chemical tagging technique. Results. We found that stars at different evolutionary stages have distinct chemical patterns that may be due to NLTE effects, atomic diffusion, mixing, and biases. When separating stars into dwarfs and giants, we observed that a few open clusters show distinct chemical signatures while the majority show a high degree of overlap. This limits the recovery of co-natal aggregates by applying the chemical tagging technique. Nevertheless, there is room for improvement if more elements are included and models are improved.Comment: accepted for publication in Astronomy and Astrophysics. Corrected typo

Total Degree Formula for the Generic Offset to a Parametric Surface

We provide a resultant-based formula for the total degree w.r.t. the spatial variables of the generic offset to a parametric surface. The parametrization of the surface is not assumed to be proper.Comment: Preprint of an article to be published at the International Journal of Algebra and Computation, World Scientific Publishing, DOI:10.1142/S021819671100680

Stellar populations of galaxies in the ALHAMBRA survey up to z∼1z \sim 1. II. Stellar content of quiescent galaxies within the dust-corrected stellar mass−-colour and the UVJUVJ colour−-colour diagrams

Our aim is to determine the distribution of stellar population parameters (extinction, age, metallicity, and star formation rate) of quiescent galaxies within the rest-frame stellar mass$-$colour and $UVJ$ colour$-$colour diagrams corrected for extinction up to $z\sim1$. These novel diagrams reduce the contamination in samples of quiescent galaxies owing to dust-reddened galaxies, and they provide useful constraints on stellar population parameters. We set constraints on the stellar population parameters of quiescent galaxies combining the ALHAMBRA multi-filter photo-spectra with our SED-fitting code MUFFIT, making use of composite stellar population models. The extinction obtained by MUFFIT allowed us to remove dusty star-forming (DSF) galaxies from the sample of red $UVJ$ galaxies. The distributions of stellar population parameters across these rest-frame diagrams are revealed after the dust correction and are fitted by the LOESS method to reduce uncertainty effects. Quiescent galaxy samples defined via classical $UVJ$ diagrams are typically contaminated by a $\sim20$% fraction of DSF galaxies. A significant part of the galaxies in the green valley are actually obscured star-forming galaxies ($\sim30-65$%). Consequently, the transition of galaxies from the blue cloud to the red sequence, and hence the related mechanisms for quenching, seems to be much more efficient and faster than previously reported. The rest-frame stellar mass$-$colour and $UVJ$ colour$-$colour diagrams are useful for constraining the age, metallicity, extinction, and star formation rate of quiescent galaxies by only their redshift, rest-frame colours, and/or stellar mass. Dust correction plays an important role in understanding how quiescent galaxies are distributed in these diagrams and is key to performing a pure selection of quiescent galaxies via intrinsic colours.Comment: (37 pages, 29 figures, accepted for publication in A&A

Comparison of Figulla Flex® and Amplatzer™ devices for atrial septal defect closure: A meta-analysis

Background: Atrial septal defect (ASD) is one of the most common congenital heart diseases. Percutaneousclosure is the preferred treatment, but certain complications remain a concern. The most common devices are AMPLATZER™ (ASO) (St. Jude Medical, St. Paul, MN, USA) and Figulla Flex® septal occluders (FSO) (Occlutech GmbH, Jena, Germany). The present study aimed to assess main differences in outcomes.Methods: A systematic search in Pubmed and Google scholarship was performed by two independent reviewers for any study comparing ASO and FSO. Searched terms were “Figulla”, “Amplatzer”, and “atrial septal defect”. A random-effects model was used.Results: A total of 11 studies including 1770 patients (897 ASO; 873 FSO) were gathered. Baseline clinical and echocardiographic characteristics were comparable although septal aneurysm was more often reported in patients treated with ASO (32% vs. 25%; p = 0.061). Success rate (94% vs. 95%; OR: 0.81; 95% CI: 0.38–1.71; p = 0.58) and peri-procedural complications were comparable. Procedures were shorter, requiring less fluoroscopy time with an FSO device (OR: 0.59; 95% CI: 0.20–0.97; p = 0.003). Although the global rate of complications in long-term was similar, the ASO device was associated with a higher rate of supraventricular arrhythmias (14.7% vs. 7.8%, p = 0.009).Conclusions: Percutaneous closure of ASD is a safe and effective, irrespective of the type of device. No differences exist regarding procedural success between the ASO and FSO devices but the last was associated to shorter procedure time, less radiation, and lower rate of supraventricular arrhythmias in follow-up. Late cardiac perforation did not occur and death in the follow-up was exceptional

The M33 Globular Cluster System with PAndAS Data: The Last Outer Halo Cluster?

We use CFHT/MegaCam data to search for outer halo star clusters in M33 as part of the Pan-Andromeda Archaeological Survey (PAndAS). This work extends previous studies out to a projected radius of 50 kpc and covers over 40 square degrees. We find only one new unambiguous star cluster in addition to the five previously known in the M33 outer halo (10 kpc <= r <= 50 kpc). Although we identify 2440 cluster candidates of various degrees of confidence from our objective image search procedure, almost all of these are likely background contaminants, mostly faint unresolved galaxies. We measure the luminosity, color and structural parameters of the new cluster in addition to the five previously-known outer halo clusters. At a projected radius of 22 kpc, the new cluster is slightly smaller, fainter and redder than all but one of the other outer halo clusters, and has g' ~ 19.9, (g'-i') ~ 0.6, concentration parameter c ~ 1.0, a core radius r_c ~ 3.5 pc, and a half-light radius r_h ~ 5.5 pc. For M33 to have so few outer halo clusters compared to M31 suggests either tidal stripping of M33's outer halo clusters by M31, or a very different, much calmer accretion history of M33.Comment: 37 pages, 9 figures. Accepted by the Astrophysical Journa

The Gaia-ESO Survey: Detailed Abundances in the Metal-poor Globular Cluster NGC 4372

We present the abundance analysis for a sample of 7 red giant branch stars in the metal-poor globular cluster NGC 4372 based on UVES spectra acquired as part of the Gaia-ESO Survey. This is the first extensive study of this cluster from high resolution spectroscopy. We derive abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, Fe, Cr, Ni, Y, Ba, and La. We find a metallicity of [Fe/H] = -2.19 $\pm$ 0.03 and find no evidence for a metallicity spread. This metallicity makes NGC 4372 one of the most metal-poor galactic globular clusters. We also find an {\alpha}-enhancement typical of halo globular clusters at this metallicity. Significant spreads are observed in the abundances of light elements. In particular we find a Na-O anti-correlation. Abundances of O are relatively high compared with other globular clusters. This could indicate that NGC 4372 was formed in an environment with high O for its metallicity. A Mg-Al spread is also present which spans a range of more than 0.5 dex in Al abundances. Na is correlated with Al and Mg abundances at a lower significance level. This pattern suggests that the Mg-Al burning cycle is active. This behavior can also be seen in giant stars of other massive, metal-poor clusters. A relation between light and heavy s-process elements has been identified.Comment: 14 pages, 14 figures, accepted for publication in A&