Giant optical gain in a rare-earth-ion-doped microstructure

Modal gain per unit length versus launched pump power is predicted and measured in a 47.5 at.% Yb(3+) -doped potassium double tungstate channel waveguide. The highest measured gain exceeds values previously reported for rare-earth-ion-doped materials by two orders of magnitude.     

Plasmon spectroscopy and imaging of individual gold nanodecahedra: a combined optical microscopy, cathodoluminescence, and electron energy-loss spectroscopy study

Imaging localized plasmon modes in noble-metal nanoparticles is of fundamental importance for applications such as ultrasensitive molecular detection. Here, we demonstrate the combined use of optical dark-field microscopy (DFM), cathodoluminescence (CL), and electron energy-loss spectroscopy (EELS) to study localized surface plasmons on individual gold nanodecahedra. By exciting surface plasmons with either external light or an electron beam, we experimentally resolve a prominent dipole-active plasmon band in the far-field radiation acquired via DFM and CL, whereas EELS reveals an additional plasmon mode associated with a weak dipole moment. We present measured spectra and intensity maps of plasmon modes in individual nanodecahedra in excellent agreement with boundary-element method simulations, including the effect of the substrate. A simple tight-binding model is formulated to successfully explain the rich plasmon structure in these particles encompasing bright and dark modes, which we predict to be fully observable in less lossy silver decahedra. Our work provides useful insight into the complex nature of plasmon resonances in nanoparticles with pentagonal symmetry.     

Severe hemorrhage because of delayed iliac vein rupture after dialysis catheter placement: Is it preventable?

Mechanical complications of femoral catheterization for hemodialysis include pseudoaneurysm, arteriovenous fistulae, neurological injury, and vessel perforation. With regard to the latter, severe hemorrhage is a rare but devastating and potentially fatal complication. We report the case of a 76-year-old female who underwent femoral catheterization for hemodialysis using ultrasound guidance. The first hemodialysis session was conducted without incident. Unfortunately, inadvertent injury and delayed perforation of the iliac vein resulted in severe hemorrhage and retroperitoneal hematoma. Surgical repair was performed. The patient was asymptomatic after the procedure and was discharged 15 days later. Based on this case and a review of the literature, we present mechanisms and ways to prevent this complication.     

Ni doped Fe3O4 magnetic nanoparticles

In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.     

Acoustically driven photon antibunching in nanowires

The oscillating piezoelectric field of a surface acoustic wave (SAW) is employed to transport photoexcited carriers, as well as to spatially control exciton recombination in GaAs-based nanowires (NWs) on a subns time scale. The experiments are carried out in core-shell NWs transferred to a SAW delay line on a LiNbO(3) crystal. Carriers generated in the NW by a focused laser spot are acoustically transferred to a second location, leading to the remote emission of subns light pulses synchronized with the SAW phase. The dynamics of the carrier transport, investigated using spatially and time-resolved photoluminescence, is well-reproduced by computer simulations. The high-frequency contactless manipulation of carriers by SAWs opens new perspectives for applications of NWs in opto-electronic devices operating at gigahertz frequencies. The potential of this approach is demonstrated by the realization of a high-frequency source of antibunched photons based on the acoustic transport of electrons and holes in (In,Ga)As NWs.     

Chitosan/poly(dl,lactide-co-glycolide) scaffolds for tissue engineering

Chitosan/poly(dl-lactide-co-glycolide) (Ch/dl PLG) composite scaffolds were fabricated by freeze-drying lyophilization, and were evaluated and compared for use as a bone regeneration scaffold through measurements of the compression mechanical properties of the porous scaffolds. Also, In vitro cell culture of Sprague?CDawley rat??s osteoblasts were used to evaluate the phenotype expression of cells in the scaffolds, characterizing the cellular adhesion, proliferation and alkaline phosphatase activity. The gene expression of osteocalcin, sialoprotein, alkaline phosphatase, Type I collagen and TGF??1 were confirmed in the samples; moreover, it was confirmed, the mineralization by IR spectra and EDS analysis. Our results thus show that Ch/dl PLG scaffolds are suitable for biological applications.     

Prediction of MOR and MOE of structural plywood board using an artificial neural network and comparison with a multivariate regression model

The structural application of plywood boards has increased considerably in recent years. In this context, determining plywood mechanical properties such as bending strength and modulus of elasticity through predictive models using more-easily obtained properties is a very useful tool for in-factory quality control. Artificial neural networks have demonstrated their high capacity for modelling complex relations between variables, considerably improving on results obtained through regression techniques. Four neural networks were developed to obtain these mechanical properties by determining board thickness, moisture content, specific gravity, bending strength and modulus of elasticity of test pieces of small dimensions. The results were compared with those of a regression model and in all cases the results of the present study were better.     

Nonlinear thermal analysis of multi-holed lightweight concrete blocks used in external and non-habitable floors by FEM

The aim of this current and innovative work is the numerical thermal analysis of multi-holed lightweight concrete blocks for external and non-habitable floors by the finite element method (FEM). Twelve different block designs with the same external dimensions 0.57 × 0.45 × 0.20 m were built varying the number of the horizontal intermediate bulkheads, from 3 to 12. Besides, five different compositions of the lightweight aggregate concrete (LWAC) and five different bulk temperatures have been taken into account, giving place to a total of 600 different floor configurations, 300 cases per each heat flow direction: upward and downward heat flows. A nonlinear thermal problem is solved for all cases analysed and then, it is possible to choose the best candidate block from the standard rule requirements. Mathematically, the nonlinearity due to the radiation boundary condition inside the inner recesses of the blocks is tackled by the matrix radiation method. Once the nonlinear thermal problem is solved, the temperature distribution is obtained and the thermal characteristic values of the floors, both for downward and upward heat flows, are calculated. From the numerical results, we can conclude that the main variables in the thermal performance are the total number of recesses and the material conductivities. Therefore, increasing the number of horizontal intermediate bulkheads and decreasing the material conductivities, the best thermal efficiency is obtained. The selection of the best candidate block of external floors and floors in contact with non-habitable spaces is carried out through the following parameters: the average mass overall thermal efficiency and the equivalent thermal conductivity. Finally, detailed instructions are provided in order to select the appropriate floor satisfying the standard rule requirements and conclusions of this work are exposed.     

Junction and Drop-Shaft Boundary Conditions for Modeling Free-Surface, Pressurized, and Mixed Free-Surface Pressurized Transient Flows

A junction and drop-shaft boundary conditions (BCs) for one-dimensional modeling of transient flows in single-phase conditions (pure liquid) are formulated, implemented and their accuracy are evaluated using two computational fluid dynamics (CFD) models. The BCs are formulated in the case when mixed flows are simulated using two sets of governing equations, the Saint-Venant equations for the free-surface regions and the compressible water hammer equations for the pressurized regions. The proposed BCs handle all possible flow regimes and their combinations. The flow in each pipe can range from free surface to pressurized flow and the water depth at the junction or drop shaft can take on all possible levels. The BCs are applied to the following three cases: (1) a three-way merging flow; (2) a three-way dividing flow; and (3) a drop shaft connected to a single-horizontal pipe subjected to a rapid variation of the water surface level in the drop shaft. The flow regime for the first two cases range from free surface to pressurized flows, while for the third case, the flow regime is pure pressurized flow. For the third case, laboratory results as well as CFD results were used for evaluating its accuracy. The results suggest that the junction and drop-shaft BCs can be used for modeling transient free-surface, pressurized, and mixed flow conditions with good accuracy.     

Forensic analysis of buildings affected by mining subsidence

This work presents a forensic analysis of ground subsidence occurred in Lo Tacón industrial area, which is located at the outskirts of La Unión (Murcia, SE Spain). Subsidence was triggered by the collapse of abandoned underground mining labours occurred in 1998. Coinciding in time with this event, it was detected a seismic movement, whose epicentre was located close to the study area.In the first part the affected area is analysed and delimited, as well as the spatial and temporal evolution of the damages attributed to the collapse of 1998. Then the causes of ground failure are also determined, as well as their possible temporal and spatial relationship with the seismic movement detected. Through this analysis it is presented a methodology to determine the effects of this phenomenon. It consists on extending field work radially to all existing buildings within the affected area, considering the centre around the zone where the greatest damage was produced. Finally it is analysed the temporal and spatial evolution of the cracks inventoried in buildings to determine active areas where certain subsidence persists. According to the results presented in this work, it may be concluded that damages are the consequence of buildings constructed in a potentially dangerous area where ground settlement occurs due to mining subsidence.