Effects of Fe doping in La1/2Ca1/2MnO3

The effect of Fe doping in the Mn site on the magnetic, transport and structural properties of polycrystalline La1/2Ca1/2MnO3 was studied. Doping with low Fe concentration (< 10%) strongly affects electrical transport and magnetization. Long range charge order is disrupted even for the lowest doping level studied (~2%). For Fe concentration up to 5% a ferromagnetic state develops at low temperature with metallic like conduction and thermal hysteresis. In this range, the Curie temperature decreases monotonously as a function of Fe doping. Insulating behavior and a sudden depression of the ferromagnetic state is observed by further Fe doping.Comment: 2 pages, presented at ICM2000, to appear in JMM

Low attenuation frequency bands for Lamb waves immersed in viscous fluids: theoretical analysis and experimental validation.

6 páginas, 3 figuras. Proceedings of the 2013 International Congress on Ultrasonics (ICU 2013). 2-5 may 2013, SingaporeThe application of Lamb waves is a promising technique i n ultrasonic NDE techniques for inspection and fluid characterization due to multi modal and dispersive characteristics. When a plate is in contact with a viscous fluid these waves are strongly attenuated. However, for most of the Lamb wave modes there is a low at tenuation frequency band that could be used for non-destructive testing or fluid characteriz ation. In order to explore this feature the phase velocity and attenuation curves of Lamb modes are expe rimentally measured in these low attenuation frequency bands, showing good agreement with theory .The present work was supported by the Brazilian National Council for Scientific and Technological Development – CNPq and the Spanish Ministery of Economy and Competitivity through the projects 560825/2010-2 and PIB2010BZ-00570, respectively.Peer reviewe

Molecularly imprinted intelligent scaffolds for tissue engineering applications

The development of molecularly imprinted polymers (MIPs) using biocompatible production methods enables the possibility to further exploit this technology for biomedical applications. Tissue engineering (TE) approaches use the knowledge of the wound healing process to design scaffolds capable of modulating cell behavior and promote tissue regeneration. Biomacromolecules bear great interest for TE, together with the established recognition of the extracellular matrix, as an important source of signals to cells, both promoting cellâ cell and cellâ matrix interactions during the healing process. This review focuses on exploring the potential of protein molecular imprinting to create bioactive scaffolds with molecular recognition for TE applications based on the most recent approaches in the field of molecular imprinting of macromolecules. Considerations regarding essential components of molecular imprinting technology will be addressed for TE purposes. Molecular imprinting of biocompatible hydrogels, namely based on natural polymers, is also reviewed here. Hydrogel scaffolds with molecular memory show great promise for regenerative therapies. The first molecular imprinting studies analyzing cell adhesion report promising results with potential applications for cell culture systems, or biomaterials for implantation with the capability for cell recruitment by selectively adsorbing desired molecules.The authors wish to thank Dr. Julia Vela-Ramirez, Ms. Heidi Culver, and Mr. John Clegg for important discussions and suggestions. This work was supported in part by the University of Texas-Portugal Collaborative Research Program, and the Grant UTAP-ICDT/CTM-BIO/0023/2014. M.E.W. is supported by a National Science Foundation Graduate Research Fellowship

Noncollinear magnetic ordering in small Chromium Clusters

We investigate noncollinear effects in antiferromagnetically coupled clusters using the general, rotationally invariant form of local spin-density theory. The coupling to the electronic degrees of freedom is treated with relativistic non-local pseudopotentials and the ionic structure is optimized by Monte-Carlo techniques. We find that small chromium clusters (N \le 13) strongly favor noncollinear configurations of their local magnetic moments due to frustration. This effect is associated with a significantly lower total magnetization of the noncollinear ground states, ameliorating the disagreement between Stern-Gerlach measurements and previous collinear calculations for Cr_{12} and Cr_{13}. Our results further suggest that the trend to noncollinear configurations might be a feature common to most antiferromagnetic clusters.Comment: 9 pages, RevTeX plus .eps/.ps figure

Simulated hypergravity induces changes in human tendon-derived cells: from cell morphology to gene expression

Gravity influences physical and biological processes, having an impact on development, as well as homeostasis of living systems. The musculoskeletal system is comprised of several mechano- responsive tissues and altered gravitational forces are known to influence distinct properties, including bone mineral density and skeletal muscle mass. This is particularly relevant in a near- weightlessness (microgravity) environment, which is found during spaceflight and, not less importantly, during bed resting. Over the years, several studies have been conducted under simulated conditions of altered gravity owing to the advances on ground-based facilities, such as bioreactors for microgravity / hypo-gravity (1g) studies. Interestingly, microgravity-induced alterations are comparable to tissue degeneration caused by disuse and ageing. In turn, exposing musculoskeletal tissues to hypergravity may constitute a way of simulating (over)loading or, eventually, to be used as a measure to rescue cell phenotype after exposure to near-weightlessness conditions. Different studies have focused on bone, cartilage and skeletal muscle, but effects on tendons and ligaments have been underappreciated. Therefore, we evaluated the influence of increasing g-levels (5g, 10g, 15g and 20g) and different hypergravity exposure periods (4 and 16 h) on the behaviour of human tendon- derived cells (hTDCs). For this purpose, hTDCs were exposed to simulated hypergravity conditions using the Large Diameter Centrifuge (LDC) from the European Space Research and Technology Centre (ESTEC, ESA, The Netherlands). Human TDCs cultured under standard conditions (1g, normogravity, Earth gravity force) were used as controls. The effects of hypergravity on the viability of hTDCs, as well as on the expression of tendon related markers at the gene level were evaluated. Simulated hypergravity resulted in a reduced cell content after 16 h independently of g-level, as determined by DNA quantification. Additionally, the different g-levels studied led to changes in cell and cytoskeleton morphology. Strikingly, a 16-hour period of exposure resulted in alterations of gene expression profiles. Overall, gene expression of tendon-related markers, including collagen types I (col1a1) and III (col3a1), scleraxis (scx), tenomodulin (tnmd), decorin (dcn) and tenascin (tnc), seemed to be increased upon hypergravity stimulation and in comparison to cells cultured under control conditions. Altogether, these results highlight that altered gravity, particularly simulated hypergravity, has an influence on the phenotype of tendon cells, opening new avenues for research focused on using altered gravity as a model for overloading-induced tendon tissue injury or as measure to rescue the phenotype of degenerated tendon cells. Acknowledgements The authors would like to thank ESA Education Office for Spin Your Thesis! 2016 programme. R.C-A acknowledges the PhD grant SFRH/BD/96593/2013 from FCT â Fundação para a Ciência e a Tecnologia. SFRH/BD/96593/2013 from FCT –Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

Vibrational Properties of Nanoscale Materials: From Nanoparticles to Nanocrystalline Materials

The vibrational density of states (VDOS) of nanoclusters and nanocrystalline materials are derived from molecular-dynamics simulations using empirical tight-binding potentials. The results show that the VDOS inside nanoclusters can be understood as that of the corresponding bulk system compressed by the capillary pressure. At the surface of the nanoparticles the VDOS exhibits a strong enhancement at low energies and shows structures similar to that found near flat crystalline surfaces. For the nanocrystalline materials an increased VDOS is found at high and low phonon energies, in agreement with experimental findings. The individual VDOS contributions from the grain centers, grain boundaries, and internal surfaces show that, in the nanocrystalline materials, the VDOS enhancements are mainly caused by the grain-boundary contributions and that surface atoms play only a minor role. Although capillary pressures are also present inside the grains of nanocrystalline materials, their effect on the VDOS is different than in the cluster case which is probably due to the inter-grain coupling of the modes via the grain-boundaries.Comment: 10 pages, 7 figures, accepted for publication in Phys. Rev.

The expression of monocarboxylate transporters in thyroid carcinoma can be associated with the morphological features of BRAF (V600E) mutation

BRAF (V600E) mutation, usually performed by DNA techniques, is one of the most common diagnostic markers in papillary thyroid carcinoma. Few papers have demonstrated that plump cells (eosinophilic cytoplasms and papillary thyroid carcinoma nuclei) and peculiar sickle-shaped nuclei represent morphological features of BRAF (V600E) on papillary thyroid carcinomas. These features seem to be linked to glycolytic phenotype whereby monocarboxylate transporters 1-4 are hypothesized to have a dominant role as lactate transporters. We investigated the association between these morphological features and monocarboxylate transporters 1 and 4 in 48 cyto-histological samples diagnosed as "positive for malignancy-favoring papillary thyroid carcinoma". These cases were processed with liquid-based cytology and underwent BRAF (V600E) mutational analysis (pyrosequencing) on liquid-based cytology and monocarboxylate transporters immunostaining on histology. The expression of monocarboxylate transporter 1, monocarboxylate transporter 4, glucose trasporter-1 and carbonic anhidrase were scored semi-quantitatively with expression from 0 to 3+ (strong positivity). The 33 mutated and 15 wild type cases showed 100 % cyto-histological concordance. The cytological evaluation revealed plump cells and sickle nuclear shape in 100 % mutated cases. Monocarboxylate transporter 1 yielded 76 % positivity in the mutated cases especially in both the plump cells and sickle-shaped nuclei, whereas the wild types showed 13.3 % positive monocarboxylate transporter 1 (p = 0.00013). Monocarboxylate transporter 4 resulted in 100 % positivity in mutated and 40 % in wild types (p 0.05). This is the first report analyzing the association between monocarboxylate transporter expression and the morphological features of BRAF (V600E) mutated papillary thyroid carcinomas suggesting the possible involvement of lactate in the morphological features.info:eu-repo/semantics/publishedVersio