274 research outputs found
In-situ thermally-reduced graphene oxide/epoxy composites: thermal and mechanical properties
Graphene has excellent mechanical, thermal, optical and electrical properties and this has made it a prime target for use as a filler material in the development of multifunctional polymeric composites. However, several challenges need to be overcome in order to take full advantage of the aforementioned properties of graphene. These include achieving good dispersion and interfacial properties between the graphene filler and the polymeric matrix. In the present work we report the thermal and mechanical properties of reduced graphene oxide/epoxy composites prepared via a facile, scalable and commercially-viable method. Electron micrographs of the composites demonstrate that the reduced graphene oxide (rGO) is well-dispersed throughout the composite. Although no improvements in glass transition temperature, tensile strength, and thermal stability in air of the composites were observed, good improvements in thermal conductivity (about 36%), tensile and storage moduli (more than 13%) were recorded with the addition of 2 wt% of rGO
Herida antebraquial infectada por Aeromonas hydrophila
Se presenta un caso de celulitis por Aeromonas hydrophila, en un paciente de
23 años, tras una herida antebraquial producida en el medio acuåtico. La celulitis se resolvió
mediante desbridamiento agresivo y quimioterapia. En los controles posteriores no se han
apreciado déficits funcionales tras la infección.A case of Aeromonas hidrophila cellulitis developped in a 23-year-old patient,
after aquatic environment forearm wound is presented. His cellulitis was effectively resolved
with aggressive debridement and chemotherapy. Follow-up examinations have shown no residual
functional deficits from the infection
Mechanochemically synthesized Pb-free halide perovskite-based Cs2AgBiBr6âCuâRGO nanocomposite for photocatalytic CO2 reduction
Pb-based halide perovskites have recently showed great potential in various applications such as solar cells, optoelectronics and photocatalysis. Despite their high performance, the Pb2+ toxicity along with poor stability hinders long term applications in photocatalysis. Herein, we report mechanochemically prepared Pb-free Cs2AgBiBr6 double perovskite nanoplates and their heterostructure with Cu-loaded reduced graphene oxide (CuâRGO) for gas-phase photocatalytic CO2 reduction using water vapor as the proton source in the absence of a hole scavenger. The resulting Cs2AgBiBr6âCuâRGO nanocomposite shows significant photocatalytic activity of 10.7 (±0.6) ÎŒmol CH4 gâ1 hâ1, 1.9 (±0.3) ÎŒmol CO gâ1 hâ1 and 1.0 (±0.2) ÎŒmol H2 gâ1 hâ1, with a CH4 selectivity of 93.0 (±0.5)% on an electron basis with 1 sun and a remarkable apparent quantum efficiency of 0.89 (±0.21)% at 590 nm. A further 32% enhancement in photocatalytic activity on an electron basis is achieved when the light intensity is doubled (2 suns). The high performance was attributed to their improved charge separation and suppressed electronâhole recombination, along with extended visible light absorption, better stability in a humid environment and improved CO2 adsorption. These findings support Cs2AgBiBr6 as a potential Pb-free alternative to conventional halide perovskites for photocatalytic solar-to-fuel conversion and CO2 utilization
Printing in three dimensions with graphene
Responsive graphene oxide sheets form nonâcovalent networks with optimum rheological properties for 3D printing. These networks have shear thinning behavior and sufficiently high elastic shear modulus (GâČ) to build selfâsupporting 3D structures by direct write assembly. Drying and thermal reduction leads to ultraâlight grapheneâonly structures with restored conductivity and elastomeric behavior
Acceso abierto y visibilidad de la investigaciĂłn. El caso de Dadun, DepĂłsito Digital de la Universidad de Navarra
ComunicaciĂłn presentada en el Congreso «Humanidades digitales: visibilidad y difusiĂłn de la investigaciĂłn», celebrado en Pamplona los dĂas 23 y 24 de mayo de 2013.
La presentación la realizaron Salomé Eslava y Arantxa Iturbide, del Servicio de Biblioteca de la Univeridad de Navarra
Robust Conditional Independence maps of single-voxel Magnetic Resonance Spectra to elucidate associations between brain tumours and metabolites.
The aim of the paper is two-fold. First, we show that structure finding with the PC algorithm can be inherently unstable and requires further operational constraints in order to consistently obtain models that are faithful to the data. We propose a methodology to stabilise the structure finding process, minimising both false positive and false negative error rates. This is demonstrated with synthetic data. Second, to apply the proposed structure finding methodology to a data set comprising single-voxel Magnetic Resonance Spectra of normal brain and three classes of brain tumours, to elucidate the associations between brain tumour types and a range of observed metabolites that are known to be relevant for their characterisation. The data set is bootstrapped in order to maximise the robustness of feature selection for nominated target variables. Specifically, Conditional Independence maps (CI-maps) built from the data and their derived Bayesian networks have been used. A Directed Acyclic Graph (DAG) is built from CI-maps, being a major challenge the minimization of errors in the graph structure. This work presents empirical evidence on how to reduce false positive errors via the False Discovery Rate, and how to identify appropriate parameter settings to improve the False Negative Reduction. In addition, several node ordering policies are investigated that transform the graph into a DAG. The obtained results show that ordering nodes by strength of mutual information can recover a representative DAG in a reasonable time, although a more accurate graph can be recovered using a random order of samples at the expense of increasing the computation time
A facile way to produce epoxy nanocomposites having excellent thermal conductivity with low contents of reduced graphene oxide
A well-dispersed phase of exfoliated graphene oxide (GO) nanosheets was
initially prepared in water. This was concentrated by centrifugation and was
mixed with a liquid epoxy resin. The remaining water was removed by evaporation,
leaving a GO dispersion in epoxy resin. A stoichiometric amount of an
anhydride curing agent was added to this epoxy-resin mixture containing the
GO nanosheets, which was then cured at 90 C for 1 h followed by 160 C for
2 h. A second thermal treatment step of 200 C for 30 min was then undertaken
to reduce further the GO in situ in the epoxy nanocomposite. An examination of
the morphology of such nanocomposites containing reduced graphene oxide
(rGO) revealed that a very good dispersion of rGO was achieved throughout the
epoxy polymer. Various thermal and mechanical properties of the epoxy
nanocomposites were measured, and the most noteworthy finding was a
remarkable increase in the thermal conductivity when relatively very low contents
of rGO were present. For example, a value of 0.25 W/mK was measured at
30 C for the nanocomposite with merely 0.06 weight percentage (wt%) of rGO
present, which represents an increase of *40% compared with that of the
unmodified epoxy polymer. This value represents one of the largest increases in
the thermal conductivity per wt% of added rGO yet reported. These observations
have been attributed to the excellent dispersion of rGO achieved in these
nanocomposites made via this facile production method. The present results
show that it is now possible to tune the properties of an epoxy polymer with a
simple and viable method of GO addition.
A
Creative destruction over the business cycle: a stochastic frontier analysis
[[abstract]]This paper examines the within-industry distributions of jobs created and destructed across plants in terms of technical efficiency, technical efficiency change, scale effect, and technical change. It further investigates how these distributions vary with economic activity. By applying the stochastic frontier analysis to plant-level longitudinal data on Taiwanâs 23 two-digit manufacturing industries spanning the period 1992â2003, we find that jobs created (destructed) are disproportionately clustered at plants with lower technical efficiency but higher rate of technical change. A fall in economic activities is associated with a statistically significant decrease (increase) in the fraction of newly created (destructed) jobs accounted for by plants with a higher rate of technical change, indicating that creative destruction is more pronounced during economic contractions.[[journaltype]]ćć€[[incitationindex]]SSCI[[ispeerreviewed]]Y[[countrycodes]]US
- âŠ