Polar optical phonons in core-shell semiconductor nanowires

We obtain the the long-wavelength polar optical vibrational modes of semiconductor core-shell nanowires by means of a phenomenological continuum model. A basis for the space of solutions is derived, and by applying the appropriate boundary conditions, the transcendental equations for the coupled and uncoupled modes are attained. Our results are applied to the study of the GaAs-GaP core-shell nanowire, for which we calculate numerically the polar optical modes, analyzing the role of strain in the vibrational properties of this nanosystem

Gestão do Conhecimento e Cooperação

Adquirir uma compreensão mais aprofundada da importância do conhecimento e da sua gestão. Ampliar a compreensão dos processos de gestão do conhecimento. Aprofundar a compreensão das relações entre a gestão do conhecimento e a cooperação. Enquadrar a compreensão da cooperação e da gestão do conhecimento numa visão qualificada dos negócios e das organizações. Conteúdos: Perspectivas da gestão do conhecimento Gestão do conhecimento e desempenho organizacional Abordagens da cooperação Processos de gestão do conhecimento e cooperação

Low-frequency phonons in carbon nanotubes: A continuum approach

7 págs.; 6 figs.; 2 apéndices ; PACS number s : 68.65. k, 63.22. mLow-frequency phonons in carbon nanotubes are studied using a continuum model which allows consideration of an arbitrary wall thickness for the nanotube. Phonon dispersion relations are calculated for two archetypal examples of carbon nanotubes, the (5,5) and (10,10) tubes. The dependence of the radial breathing mode frequency at Γ on the inverse nanotube diameter is verified within this model; furthermore, we prove it to hold for all pure modes within the thin-shell approximation. The effect of the nanotube wall thickness on the eigenfrequencies of carbon nanotubes is also analyzed, and a criterion to fix this parameter within a continuum model is presented. We compare our results to other continuum approaches, and show that by choosing the appropriate parameters, excellent agreement with recent first-principles calculations can be achieved. © 2006 The American Physical Society.This work has been partly supported by the Spanish DGES Grant No. MAT 2002-04540-C05-03 and the Vicerrectorado de Relaciones Internacionales UCLM.Peer Reviewe

Decent work: an aim for all made by all

The aim of this article is to analyse the 11 substantive elements of the Decent Work concept developed by the International Labour Organization. We identify 4 main aspects regarding the pursuit of decent work, which are challenges for the different agents who operate in society: (1) the responsibility shared among the various social agents; (2) cultural differentiation in expressing Decent Work; (3) its evolving character arising from the advancement of scientific knowledge; and finally, (4) the global interdependence in the scenario in which social agents operate. Four propositions aligned with those aspects are formulated, and consequences for research and intervention are proposed

Search algorithm for a gravitational wave signal in association with Gamma Ray Burst GRB030329 using the LIGO detectors

One of the brightest Gamma Ray Burst ever recorded, GRB030329, occurred during the second science run of the LIGO detectors. At that time, both interferometers at the Hanford, WA LIGO site were in lock and acquiring data. The data collected from the two Hanford detectors was analyzed for the presence of a gravitational wave signal associated with this GRB. This paper presents a detailed description of the search algorithm implemented in the current analysis.Comment: To appear in the Proceedings of 8th Gravitational Wave Data Analysis Workshop (Milwaukee, WI) (Class. Quantum Grav.

Effects of protein incorporation on calcium phosphate coating

The incorporation of proteins into calcium phosphate (Ca–P) coatings is expected to alter their properties. The aim of this work is, therefore, to study the effect of protein concentration on the formation of Ca–P film. A biodegradable blend of corn starch/ethylene vinyl alcohol (SEVA-C) was used as substrate and bioactive glass (45S5 Bioglass®) was used as a nucleating agent. Bovine serum albumin (BSA) and α-amylase were added, separately, at a concentration of 0.5, 1, and 5 mg/mLto simulated body fluid (SBF) solutions, at the nucleation stage. The incorporation of protein molecules was shown to affect the properties of Ca–P coatings in terms of morphology, composition and crystallinity. Both proteins seem to inhibit in some extent and/or retard the growth of Ca–P nuclei at 0.5 and 5 mg/mL concentrations. FTIR analyses revealed the presence of phosphate and carbonate groups, confiming the formation of a Ca–P layer. The characteristic groups of protein molecules were also detected on the IR spectra, which indicate the efficient incorporation of the proteins into the coatings. When α-amylase was added to the SBF solution the production of reducing sugars was detected, proving the retention of enzyme activity. These results suggest the carrier potential of Ca–P coatings for the sustained delivery of other biologically active proteins and consequently with a strong potential for inducing bone tissue regeneration.This work was partially supported by Portuguese Foundation for Science and Technology (FCT) and was performed within the framework of the project BIOLEARN (POCTI/CTM/38803/2001) through funds from the POCH and/or FEDER Programmes. 1. B. Leonor thanks FCT for providing her a PhD scholarship (SFRH/BD/9031/2002)

Localization of osteocalcin (BGP) during fish (Sparus aurata) development by in situ hybridization and immunohistochemistry: comparison between gene expression/protein distribution and skeletal mineralization

Osteocalcin (Bone Gla protein, BGP) is a small noncollagenous protein which is synthesized by osteoblasts and odontoblasts and is found exlusively in mineralized bony tissues. Although isolated for the first time in 1978, only recently has a function for this protein been suggested, specifically in controlling hydroxyapatite crystal growth. Appearance of osteocalcin could be linked to the presence of an hydroxyapatite-containing bony skeleton, since the protein was never found in cartilaginous fishes. Furthermore, within its primary sequence the amino acid residues known to be essential for its function are present in fish as well as in mammals, suggesting that function has been conserved over 400 million years of evolution. Taken totgether, these findings prompted us to study in detail the localization of osteocalcin gene expression in fish

Silk fibroin-spider silk-like protein biomaterials for preventing microbial infections

Publicado em "Frontiers in Bioengineering and Biotechnology. Conference Abstract: 10th World Biomaterials Congress"Introduction: Microbial contamination of medical devices, such as sutures, are one of the major causes of hospital infections despite improvements in medical healthcare[1]. Thus, it is important to explore new biomaterials with antimicrobial properties in order to overcome microbial colonisation and biofilm formation. Spider silk has been considered an excellent biomaterial because of its toughness, strength and outstanding elasticity[2]. Also, through recombinant DNA technology, we can bioengineer and functionalize spider silk-based materials with antimicrobial peptides (AMP), thus evolving a new type of biomaterials[3]. Herein, the aim of this study was to develop silk-based fibers with antimicrobial properties by combining silk fibroin (SF) with recombinant spider silk proteins functionalized with AMP. Materials and Methods: Silk-based sutures were produced by combining spider silk chimeric proteins SSP (6mer and 6mer-HNP1) with different ratios of SF extracted from Bombyx mori through wet-spinning. The structure and topography of the sutures were characterized by scanning electron microscopy (SEM) and the tensile properties and knot strength of the sutures was assessed using an INSTRON 5540 Universal Machine. The formation of biofilm on the fibers was assessed and hemolytic effects of the materials were evaluated. Results and Discussion: Silk fibers containing spider silk 6mer or 6mer-HNP1 showed improved tensile behaviour when compared to silk fibers without SPP (Figure 1). The results suggest that the combination of spider silk chimeric proteins with SF increased the tensile stress of the fibers, when compared to those without spider silk chimeric proteins. No bacterial biofilm was observed on the fibers containing SSP functionalized with AMP, suggesting that the presence of the 6mer-HNP1 prevented the formation of biofilm. Conclusions: The outcomes suggest that silk-based fibers functionalized with AMP showed better mechanical properties when compared to silk fibers alone. The data also demonstrate the positive effect of the presence of AMP in preventing biofilm formation on the fibers, suggesting that the functionalized silk fibers could be used as a new strategy to produce sutures capable of preventing microbial proliferation, while retaining useful mechanical properties. Further investigation is still need in order to understand the in vivo performance of sutures and their physical changes during wound healing.Portuguese Foundation for Science and Technology under the scope of the project PTDC/BBB­BIO/0827/201

Redox activity of melanin from the ink sac of Sepia officinalis by means of colorimetric oxidative assay

The redox properties of natural extract from cuttlefish ink sac (Sepia officinalis) and synthetic melanin used as a biomimetic in melanin structural investigation were determined by comparison of this phenol-based heterogeneous pigment with gallic acid used as a standard in Folinâ Ciocalteu colorimetric assay widely employed for characterisation of oxidative properties of biomaterials. Reactivity of sepia melanin reported here is much higher than previously indicated and this protocol should allow the redox characterisation of all melanins irrespective of their origin and composition.European Union’s Seventh Framework Programme (FP7/2007-2013) [grant agreement number REGPOT-CT2012-316331-POLARIS