Light polarization sensitive photodetectors with m- and r-plane homoepitaxial ZnO/ZnMgO quantum wells

Homoepitaxial ZnO/(Zn,Mg)O multiple quantum wells (MQWs) grown with m- and r-plane orientations are used to demonstrate Schottky photodiodes sensitive to the polarization state of light. In both orientations, the spectral photoresponse of the MQW photodiodes shows a sharp excitonic absorption edge at 3.48 eV with a very low Urbach tail, allowing the observation of the absorption from the A, B and C excitonic transitions. The absorption edge energy is shifted by ∼30 and ∼15 meV for the m- and r-plane MQW photodiodes, respectively, in full agreement with the calculated polarization of the A, B, and C excitonic transitions. The best figures of merit are obtained for the m-plane photodiodes, which present a quantum efficiency of ∼11%, and a specific detectivity D* of ∼6.4 × 1010 cm Hz1/2/W. In these photodiodes, the absorption polarization sensitivity contrast between the two orthogonal in-plane axes yields a maximum value of (R⊥/R||)max ∼ 9.9 with a narrow bandwidth of ∼33 meV.

Space density distribution of galaxies in the absolute magnitude - rotation velocity plane: a volume-complete Tully-Fisher relation from CALIFA stellar kinematics

We measured the distribution in absolute magnitude - circular velocity space for a well-defined sample of 199 rotating galaxies of the Calar Alto Legacy Integral Field Area Survey (CALIFA) using their stellar kinematics. Our aim in this analysis is to avoid subjective selection criteria and to take volume and large-scale structure factors into account. Using stellar velocity fields instead of gas emission line kinematics allows including rapidly rotating early-type galaxies. Our initial sample contains 277 galaxies with available stellar velocity fields and growth curve r-band photometry. After rejecting 51 velocity fields that could not be modelled because of the low number of bins, foreground contamination, or significant interaction, we performed Markov chain Monte Carlo modelling of the velocity fields, from which we obtained the rotation curve and kinematic parameters and their realistic uncertainties. We performed an extinction correction and calculated the circular velocity v_circ accounting for the pressure support of a given galaxy. The resulting galaxy distribution on the M-r - v(circ) plane was then modelled as a mixture of two distinct populations, allowing robust and reproducible rejection of outliers, a significant fraction of which are slow rotators. The selection effects are understood well enough that we were able to correct for the incompleteness of the sample. The 199 galaxies were weighted by volume and large-scale structure factors, which enabled us to fit a volume-corrected Tully-Fisher relation (TFR). More importantly, we also provide the volume-corrected distribution of galaxies in the M_r - v_circ plane, which can be compared with cosmological simulations. The joint distribution of the luminosity and circular velocity space densities, representative over the range of -20 > M_r > -22 mag, can place more stringent constraints on the galaxy formation and evolution scenarios than linear TFR fit parameters or the luminosity function alone.

Design and application of experimental methods for steel sheet shearing

Shearing is the process where sheet metal is mechanically cut between two tools. Various shearing technologies are commonly used in the sheet metal industry, for example, in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material. The constant development of sheet metals toward higher strength and formability leads to increased forces on the shearing equipment and tools. Shearing of new sheet materials imply new suitable shearing parameters. Investigations of the shearing parameters through live tests in the production are expensive and separate experiments are time consuming and requires specialized equipment. Studies involving a large number of parameters and coupled effects are therefore preferably performed by finite element based simulations. Accurate experimental data is still a prerequisite to validate such simulations. There is, however, a shortage of accurate experimental data to validate such simulations. In industrial shearing processes, measured forces are always larger than the actual forces acting on the sheet, due to friction losses. Shearing also generates a force that attempts to separate the two tools with changed shearing conditions through increased clearance between the tools as result. Tool clearance is also the most common shearing parameter to adjust, depending on material grade and sheet thickness, to moderate the required force and to control the final sheared edge geometry. In this work, an experimental procedure that provides a stable tool clearance together with accurate measurements of tool forces and tool displacements, was designed, built and evaluated. Important shearing parameters and demands on the experimental set-up were identified in a sensitivity analysis performed with finite element simulations under the assumption of plane strain. With respect to large tool clearance stability and accurate force measurements, a symmetric experiment with two simultaneous shears and internal balancing of forces attempting to separate the tools was constructed. Steel sheets of different strength levels were sheared using the above mentioned experimental set-up, with various tool clearances, sheet clamping and rake angles. Results showed that tool penetration before fracture decreased with increased material strength. When one side of the sheet was left unclamped and free to move, the required shearing force decreased but instead the force attempting to separate the two tools increased. Further, the maximum shearing force decreased and the rollover increased with increased tool clearance. Digital image correlation was applied to measure strains on the sheet surface. The obtained strain fields, together with a material model, were used to compute the stress state in the sheet. A comparison, up to crack initiation, of these experimental results with corresponding results from finite element simulations in three dimensions and at a plane strain approximation showed that effective strains on the surface are representative also for the bulk material. A simple model was successfully applied to calculate the tool forces in shearing with angled tools from forces measured with parallel tools. These results suggest that, with respect to tool forces, a plane strain approximation is valid also at angled tools, at least for small rake angles. In general terms, this study provide a stable symmetric experimental set-up with internal balancing of lateral forces, for accurate measurements of tool forces, tool displacements, and sheet deformations, to study the effects of important shearing parameters. The results give further insight to the strain and stress conditions at crack initiation during shearing, and can also be used to validate models of the shearing process.

X Factors (Rebecca's Mermaid and Sonja's Plane)

Combined media on photographic paper.

Plane

Mixed media. 23" x 19", Complexity Series.

A novel two-stage discrete crack method based on the screened Poisson equation and local mesh refinement

We propose an alternative crack propagation algo- rithm which effectively circumvents the variable transfer procedure adopted with classical mesh adaptation algo- rithms. The present alternative consists of two stages: a mesh-creation stage where a local damage model is employed with the objective of defining a crack-conforming mesh and a subsequent analysis stage with a localization limiter in the form of a modified screened Poisson equation which is exempt of crack path calculations. In the second stage, the crack naturally occurs within the refined region. A staggered scheme for standard equilibrium and screened Poisson equa- tions is used in this second stage. Element subdivision is based on edge split operations using a constitutive quantity (damage). To assess the robustness and accuracy of this algo- rithm, we use five quasi-brittle benchmarks, all successfully solved.

Debonding and crack propagation in cracked steel beams strengthened with CFRP and subjected to cyclic loads.

The reinforcement methods used to restore or increase the bearing capacity of metal structures are based on the application of steel plates to be bolted or welded to the original structure, which can cause problems to the integrity of the original structure. These difficulties can be overcome with the introduction of fiber-reinforced composite materials. FRPs are characterized by high strength to weight ratio, and they are very resistant to corrosion. In this dissertation a cracked steel I-beam reinforced with Carbon Fiber-Reinforced Polymer will be studied by performing a numerical evaluation of the structure with the commercial Finite Element Method software ABAQUS. The crack propagation will be computed using XFEM, while the debonding of the reinforcement layer will be found by considering a cohesive contact interface between the beam and the CFRP plate. The results will show the efficiency of the strengthening method in increasing the load carrying capacity of the cracked beam, and in reducing the crack opening of the initial notch.

Agravos decorrentes do uso de drogas como o crack

Questões que abordam os agravos decorrentes do uso de drogas como o crack.

Caso Jefferson: tuberculose, crack e redução de danos [exercício]

Palavras cruzadas sobre tuberculose, consumo de crack e redução de danos

Cocaína e crack: conceitos básicos

Texto que compõe a unidade 1 do módulo 4 “Cocaína e Crack” do Curso de Capacitação em Dependência Química, produzido pela UNA-SUS/UFMA. Aborda alguns conceitos básicos sobre a cocaína e o crack, as formas de uso, a farmacocinética e farmacodinâmica, os fatores de risco, a correlação da neurobiologia com a clínica do dependente de cocaína, bem como os déficits neurocognitivos associados ao uso de crack e da cocaína.

Cocaína e crack: tratamento

Texto que compõe a unidade 2 do módulo 4, “Cocaína e crack”, do Curso de Capacitação em Dependência Química, produzido pela UNA-SUS/UFMA. Aborda os principais tipos de tratamento de dependentes de cocaína e crack, destacando as principais medidas a serem tomadas no processo de reconhecimento do problema e que propiciem a mudança no estilo de vida do dependente químico

Cocaína e crack: outras drogas

Texto que compõe a unidade 3 do módulo 4, “Cocaína e crack”, do Curso de Capacitação em Dependência Química, produzido pela UNA-SUS/UFMA. Aborda os efeitos e tratamentos à algumas substâncias que são cada vez mais utilizadas por adolescentes e jovens, tais como a ecstasy, LSD, Rohypnol, anfetaminas e outras

Cocaína e crack: intervenção familiar

Texto que compõe a Unidade 4 do Módulo 4, “Cocaína e crack”, do Curso de Capacitação em Dependência Química, produzido pela UNA-SUS/UFMA. Apresenta as intervenções psicossociais, destacando a intervenção familiar na abordagem ao dependente químico

Curso EaD sobre saúde mental na Atenção Primária à Saúde para médicos: álcool e drogas, dependência de cocaína e crack

Este vídeo integra o "Curso EaD sobre saúde mental na Atenção Primária à Saúde para médicos”, desenvolvido pelo TelessaúdeRS/UFRGS. Trata do problema da dependência de cocaína e crack. Apresenta informações básicas para médicos da Atenção Primária à Saúde sobre as duas drogas, com ênfase para efeitos agudos e crônicos provocados pela sua utilização.

Saúde mental: caso clínico [dependência de cocaína e crack]

Vídeo produzido com o GoAnimate! que apresenta Jair que, desde a adolescência, faz o consumo de álcool e outras drogas, o que o levou a um quadro de transtorno depressivo. A partir da situação, o vídeo propõe a reflexão sobre o manejo adequado do caso.