Este projeto de pesquisa recebeu financiamento do Conselho Europeu de Investigação no âmbito do Programa da Comunidade Europeia Quadro (FP7/2007-2013) / subvenção CEI acordo n ° 242710 e foi ainda o apoio do Programa Ciência das Fronteiras Humanas e do Programa de Emmy Noether do Alemão Research Foundation (SCHR 995/2-1).

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E., Pines, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+imaging+using+a+targeted+magnetic+resonance+hyperpolarized+biosensor.">Molecular imaging using a targeted magnetic resonance hyperpolarized biosensor.</a> Science. 314, 446-449 (2006).</li><li>Schrank, G., Ma, Z., Schoeck, A., Saam, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+a+low-pressure+high-capacity+129Xe+flow-through+polarizer.">Characterization of a low-pressure high-capacity 129Xe flow-through polarizer.</a> Phys. Rev. A. 80, 063424 (2009).</li><li>Levron, D., Walter, D. K., Appelt, S., Fitzgerald, R. J., Kahn, D., Korbly, S. E., Sauer, K. E., Happer, W., Earles, T. L., Mawst, L. J., Botez, D., Harvey, M., DiMarco, L., Connolly, J. C., M&#246;ller, H. E., Chen, X. J., Cofer, G. P., Johnson, G. 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Lett. 21, 1501-1503 (2004).</li><li>Zhou, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hyperpolarized+noble+gases+as+contrast+agents.">Hyperpolarized noble gases as contrast agents.</a> Methods Mol. Biol. 771, 189-204 (2011).</li><li>Seltzer, S. J., Michalak, D. J., Donaldson, M. H., Balabas, M. V., Barber, S. K., Bernasek, S. L., Bouchiat, M. A., Hexemer, A., Hibberd, A. M., Kimball, D. F., Jaye, C., Karaulanov, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+antirelaxation+coatings+for+alkali-metal+vapor+cells+using+surface+science+techniques.">Investigation of antirelaxation coatings for alkali-metal vapor cells using surface science techniques.</a> J. Chem. Phys. 133, 144703 (2010).</li></ol>

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Aspectos críticos na preparação de xénon hiperpolarizado são impurezas de oxigénio no colector de gás, incluindo a célula de bombagem e iluminação suficiente da célula com luz polarizada circularmente. O teste de lâmpada de luz acima mencionada é uma maneira simples para detectar concentrações de oxigénio deletérios durante a transferência de rubídio. O metal alcalino pode perder a sua superfície brilhante quando a célula está instalado no polarizador. No entanto, a vaporização suficiente de Rb n...

Hiperpolarizados agentes estão ganhando cada vez mais atenção por RMN / RM aplicações, uma vez que pode resolver o problema de sensibilidade em certas circunstâncias 2. Três principais abordagens são usados ​​atualmente (polarização nuclear dinâmica, DNP, para-hidrogênio polarização induzida, PHIP e troca de spin bombeamento óptico, Seop) que todas as preparar uma diferença de população aumentada artificialmente rodada fora de um ímã RMN antes da espectroscopia real ou experiência de imagem . Aqui descreve-se a função e operação de uma instalação de Seop que foi optimizada para a produção de 129Xe hiperpolarizado utilizado em experiências de estado de solução. Um componente essencial é uma intensa fonte de luz que emite fótons infravermelhos em 795 nm. Matrizes laser de diodo (LDA) são dispositivos que fornecem convenientes alta potência&gt; W 100 a um custo razoável. Em muitas configurações, o LDA é emissor para uma fibra óptica, que mais ou menos mantém a polarização do the luz laser. Para garantir um processo de Seop suficiente dessa polarização elíptica deve ser convertido em polarização circular de alta pureza. Os principais componentes do sistema óptico de polarização são mostrados nas Figuras 1 e 2 e a configuração do sistema é explicada esquematicamente em filme suplementar 1. Para circularmente polarizar a luz que primeiro fixe a extremidade da fibra óptica para um feixe primário de expansão (por exemplo, um colimador da fibra) para reduzir a densidade de potência. A luz passa através de um divisor de feixe polarizador cubo, a geração de luz polarizada linearmente. Rodando este cubo, podemos determinar o eixo preferencial da polarização remanescente com um medidor de potência. Máximo de transmissão corresponde à situação em que o eixo rápido de o cubo está alinhado com o eixo principal de luz de polarização. Cubos com coeficientes de extinção elevados (100000: 1 ou superior) produzir uma boa separação de componentes de polarização. Isto pode ser testadoutilizando um divisor de cubo segundo feixe como um analisador que é rodado enquanto a primeira está alinhada para a transmissão máxima do feixe de extra-ordinária. Uma vez que a polarização linear da luz transmitida tenha sido confirmada, uma placa de onda λ / 4 concebido para 795 nm introduz-se o feixe de extraordinária para converter linear em polarização circular. Para este efeito, o eixo rápido da placa de onda é girado em 45 ° em relação ao eixo do cubo separador de feixes rápido. (Se desejado, a polarização circular do feixe reflectido comum com o seu eixo perpendicular a polarização linear do feixe de extra-ordinária pode ser conseguida de uma maneira semelhante.) A qualidade da polarização circular pode ser testado com um segundo cubo separador de feixes, que deve produzir transmissão constante durante a rotação. A óptica de feixe secundário de expansão (por exemplo, duas lentes em uma configuração telescópio Galileu), em seguida, aumenta o diâmetro do feixe de completamente illuminate a célula de vidro para o processo de bombeamento dentro de uma caixa de forno. A absorção da luz do laser por Rb vapor na célula é monitorada por meio de um furo de fixação atrás da célula de bombagem na extremidade da caixa: um colimador recolhe um feixe de luz infravermelha atenuado a ser analisado, com um espectrómetro de óptica (ver Figura 3 para o bombeamento de configuração celular ). Um mecanismo de aquecimento para fora da célula de bombagem parcialmente vaporiza uma gotícula Rb sentado no interior da célula (Figura 4-A) e, portanto, faz com que a absorção de luz laser. Densidade do vapor pode ser ajustado por meio do ponto de regulação de aquecimento do controlador PID correspondente. As altas temperaturas (cerca de 190 ° C) são boas para configurações compactas, onde o xenon tem uma quantidade limitada de tempo para construir polarização. A mistura de gás contendo Xe, N2 e ele flui através da célula de bombagem oposta à direcção do feixe laser (Figura 3). Um campo magnético externo alinhada com o feixe de laser que garante thfotões E IR só são bombeando uma transição Rb. Relaxamento dos estados de elétrons é rápido e devem ser não-radiativos para evitar a emissão de fótons com polarização IR &quot;errado&quot;. Aqui, a 2 N entra em jogo na forma de gás de têmpera. Eventualmente, o sistema Rb constrói uma superpopulação de um dos sub-níveis de estado de terra, enquanto o outro é continuamente descarregada pelo laser (Figura 5). Xenon ficando em contacto estreito com os átomos de Rb experimenta interacções spin-spin e a polarização do spin electrónico é transferido para Xe núcleos em flip-flop processos. O gás hiperpolarizado fluir para fora da célula de bombagem contém traços de vapor de Rb que o condensado sobre a parede de tubo dentro de alguns cm de saída, devido à temperatura baixa (semelhante à Figura 4b). As aplicações in vivo, no entanto, exigiria eliminação adicional do de metal alcalino (por exemplo, através de uma câmara de frio), enquanto in vitro experiments pode ser realizada de forma segura com o gás que sai do hiperpolarizadora. Tubagem de Teflon liga a saída polarizador com a entrada de um aparelho de vidro para realizar experiências de RMN em soluções de teste. Os controladores de fluxo de massa são usados ​​para ajustar a quantidade de Xe fluir para a instalação de RMN. Eles são acionados por comandos na seqüência de pulsos de RMN. Depois de verificar o aumento de polarização atingida, o gás pode ser usado como um agente de contraste de RMN / RM em experimentos de estado de solução. Xe tem uma solubilidade em água de certo (4,5 mM / atm) e outros solventes. É, por conseguinte, podem servir já por si só como um agente de contraste para obter a distribuição de alguns líquidos. No entanto, é também possível ligar o núcleo de RMN-activo a certas moléculas, a fim de adquirir molecular informações específicas através do gás de outra forma inerte. Ao proporcionar um hospedeiro molecular para o Xe dissolvido, é possível conferir especificidade molecular para o sinal de RMN de XE. Isto oferece a oportunidade deOs agentes de contraste de design funcionalizadas - também chamado de biossensores - quando a estrutura de um tal hospedeiro é acoplado a uma unidade de direccionamento que se liga a analitos específicos de interesse biomédico (Figura 6). Aumento de sensibilidade adicional é necessária quando o biossensor deve ser detectado em concentrações que são de baixo para os agentes de contraste para RM (&lt;100 | iM). Isto pode ser conseguido por transferência de produtos químicos de saturação de câmbio (CET). Este método detecta a biossensor indirectamente através da destruição da magnetização do Xe enjaulado e observando a alteração de sinais de Xe livre em solução. Uma vez que os núcleos são continuamente substituídos hiperpolarizado, após cerca de 10 ms de transferência de núcleo, muitas 100-1000 a informação para a piscina detectado e amplificar o sinal ca. 10 3 vezes (ver o filme 2).

<table border="1"><tbody><tr><td> Nome do reagente </td><td> Companhia </td><td> Número de catálogo </td><td> Comentários (opcional) </td></tr><tr><td> Lingote Rb </td><td> Sigma-Aldrich </td><td> 276332-1G </td><td></td></tr><tr><td> P 4 O 10 </td><td> Sigma-Aldrich </td><td> 79610-500G </td><td></td></tr><tr><td> Ar </td><td> Praxair </td><td></td><td></td></tr><tr><td> Xe </td><td> Sigma-Aldrich </td><td> 00.472-1EA </td><td></td></tr><tr><td> O 2 </td><td> Sigma-Aldrich </td><td> 00.476-1EA </td><td></td></tr><tr><td> Sistema laser </td><td> Lasers QPC / Operações Laser </td><td> Brightlock 50 </td><td></td></tr><tr><td> Sistema de vácuo </td><td> Pfeiffer </td><td> HiCube </td><td></td></tr><tr><td> Termopares </td><td> NewportÓmega </td><td> SA2F-KI-3M </td><td></td></tr><tr><td> Aquecedor de silício </td><td> Newport Omega </td><td> FMA5514 </td><td></td></tr><tr><td> O transdutor de pressão </td><td> Newport Omega </td><td> PR 33X-V-10 </td><td></td></tr><tr><td> Medidor de processo </td><td> Newport Omega </td><td> INFCP-100B </td><td></td></tr><tr><td> Fluxo de controladores de massa </td><td> Newport Omega </td><td> MFC </td><td></td></tr><tr><td> Reguladores PID </td><td> Newport Omega </td><td> CN7800 </td><td></td></tr><tr><td> Software de controle </td><td> Newport Omega </td><td> DasyLab </td><td></td></tr><tr><td> A aquisição de dados </td><td> Newport Omega </td><td> Daqboard 3000 </td><td></td></tr><tr><td> Sensor de vácuo </td><td> Oerlikon </td><td> TTR91 </td><td></td></tr><tr><td> Controlador de vácuo </td><td> Vacom </td><td> MVC-3 </td><td></td></tr><tr><td> Feixe colimador </td><td> Thorlabs </td><td> F810SMA-780 </td><td></td></tr><tr><td> Divisor de feixe de polarização cubo </td><td> Thorlabs </td><td> GL15-B </td><td></td></tr><tr><td> λ placa / 4 onda </td><td> Thorlabs </td><td> WPQ10M-780 </td><td></td></tr><tr><td> Expansão lentes de feixe </td><td> Thorlabs </td><td></td><td></td></tr><tr><td> Espectrômetro óptico </td><td> Ocean Optics </td><td> HR4000 </td><td></td></tr><tr><td> Fibra ótica </td><td> Ocean Optics </td><td></td><td></td></tr><tr><td> Tubo de RMN a baixa pressão </td><td> Wilmad </td><td> 513-7LPV-7 </td><td></td></tr><tr><td> Tubo NMR 5 milímetros </td><td> Sigma-Aldrich </td><td> HX58.1 </td><td></td></tr><tr><td> Bobinas de Helmholtz </td><td> Phywe </td><td> 06960-00 </td><td></td></tr><tr><td> Sili Fusedca capilares </td><td> Polymicro </td><td> TSG 250350 </td><td></td></tr></tbody></table>

hyperpolarized xenon for nmr and mri applications

Ressonância magnética nuclear (RMN) e de imagem (MRI) sofrem de baixa sensibilidade intrínseca, porque mesmo fortes campos magnéticos externos de ~ 10 T gerar apenas uma pequena detectável líquido magnetização da amostra à temperatura ambiente 1. Assim, a maioria das aplicações de RMN e RM se baseiam na detecção de moléculas com uma concentração relativamente alta (por exemplo, água para a imagiologia de tecido biológico) ou requerem tempos de aquisição excessivos. Isto limita a capacidade de explorar a especificidade molecular muito útil de sinais de RMN para muitas aplicações bioquímicos e médicos. No entanto, novas abordagens têm surgido nos últimos anos: Manipulação da espécie de spin detectadas antes da detecção dentro do magneto RMN / RM pode aumentar dramaticamente a magnetização e, portanto, permite a detecção de moléculas com uma concentração muito mais baixa 2. A seguir, apresentamos um processo para a polarização de uma mistura de gás de xénon (Xe 2-5%, 10%N 2, Ele equilíbrio) em uma configuração compacta com um ca. 16.000 vezes o aumento do sinal. Modern lasers de diodo-linha estreitadas permitir polarização 7 e eficiente utilização imediata da mistura de gás, mesmo que o gás nobre não é separado dos outros componentes. O aparelho de Seop é explicado e determinação da polarização do spin alcançado é demonstrada pelo controlo do desempenho do método. O gás hiperpolarizado pode ser usado para imagiologia de espaço vazio, incluindo imagiologia de fluxo de gás ou de estudos de difusão nas interfaces com outros materiais 8,9. Além disso, o sinal de RMN de Xe é extremamente sensível ao seu ambiente molecular 6. Isto permite a opção de utilizar como um agente de contraste de RMN / RM quando dissolvido numa solução aquosa com funcionalizados hospedeiros moleculares que aprisionam o gás temporariamente 10,11. A detecção directa e de alta sensibilidade de detecção indirecta de tais construções é demonstrada tanto em modo de espectroscopia e de imagem. &lt;/ P&gt;

Watch this Scientific Journal Video about Hyperpolarized Xenon for NMR and MRI Applications at JoVE.com

Hyperpolarized Xenon for NMR and MRI Applications

A produção de xénon hiperpolarizado através da troca de spin bombeamento óptico (Seop) é descrita. Este método produz um realce ~ 10000 vezes da polarização do spin nuclear do Xe-129 e tem aplicações em espectroscopia de ressonância magnética nuclear e de imagem. Exemplos de fase gasosa e em solução são as experiências de estado dado.

Xenon hiperpolarizada para RMN e Aplicações de ressonância magnética

Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 ...

hyperpolarized-xenon-for-nmr-and-mri-applications

Research

JoVE Journal

Engineering

19.4K visualizações.  Leibniz-Institut für Molekulare Pharmakologie. A produção de xénon hiperpolarizado através da troca de spin bombeamento óptico (Seop) é descrita. Este método produz um realce ~ 10000 vezes da polarização do spin nuclear do Xe-129 e tem aplicações em espectroscopia de ressonância magnética nuclear e de imagem. Exemplos de fase gasosa e em solução são as experiências de estado dado.

Vídeo: Hyperpolarized Xenon for NMR and MRI Applications

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 &deg;C), flammable, and volatile organic electrolytes. These organic based electrolyte systems are viable at ambient temperatures, but require a cooling system to ensure that temperatures do not exceed 80 &deg;C. These cooling systems tend to increase battery costs and can malfunction which can lead to battery malfunction and explosions, thus endangering human life. Increases in petroleum prices lead to a huge demand for safe, electric hybrid vehicles that are more economically viable to operate as oil prices continue to rise. Existing organic based electrolytes used in lithium ion batteries are not applicable to high temperature automotive applications. A safer alternative to organic electrolytes is solid polymer electrolytes. This work will highlight the synthesis for a graft copolymer electrolyte (GCE) poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature (Tg) poly(oxyethylene) acrylate (POEA). The conduction mechanism has been discussed and it has been demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence. Batteries containing commercially available LP30 organic (LiPF6 in ethylene carbonate (EC):dimethyl carbonate (DMC) at a 1:1 ratio) and GCE were cycled at ambient temperature. It was found that at ambient temperature, the batteries containing GCE showed a greater overpotential when compared to LP30 electrolyte. However at temperatures greater than 60 &deg;C, the GCE cell exhibited much lower overpotential due to fast polymer electrolyte conductivity and nearly the full theoretical specific capacity of 170 mAh/g was accessed.

Lithium ion batteries employ flammable and volatile organic electrolytes that are suitable for ambient temperature applications. A safer alternative to organic electrolytes are solid polymer batteries. Solid polymer batteries operate safely at high temperatures (&gt;120 &deg;C), thus making them applicable to high temperature applications such as deep oil drilling and hybrid electric vehicles. This paper will discuss (a) the polymer synthesis, (b) the polymer conduction mechanism, and (c) provide temperature cycling for both solid polymer and organic electrolytes.

Eletrólitos copolímero de enxerto de estado sólido para Aplicações da bateria de lítio

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 ...

Engenharia

Use of a Multi-compartment Dynamic Single Enzyme Phantom for Studies of Hyperpolarized Magnetic Resonance Agents

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due to fundamental constraints imposed by the hyperpolarized state, exotic imaging and reconstruction techniques are commonly used. A practical system for characterization of dynamic, multi-spectral imaging methods is critically needed. Such a system must reproducibly recapitulate the relevant chemical dynamics of normal and pathological tissues. The most widely utilized substrate to date is hyperpolarized [1-13C]-pyruvate for assessment of cancer metabolism. We describe an enzyme-based phantom system that mediates the conversion of pyruvate to lactate. The reaction is initiated by injection of the hyperpolarized agent into multiple chambers within the phantom, each of which contains varying concentrations of reagents that control the reaction rate. Multiple compartments are necessary to ensure that imaging sequences faithfully capture the spatial and metabolic heterogeneity of tissue. This system will aid the development and validation of advanced imaging strategies by providing chemical dynamics that are not available from conventional phantoms, as well as control and reproducibility that is not possible in vivo.

A multi-compartment dynamic phantom is used to simulate some biology of interest for metabolic studies using hyperpolarized magnet resonance agents.

O uso de um compartimento Multi-dinâmica única enzima Fantasma de Estudos de hyperpolarized agentes Ressonância Magnética

Imaging of hyperpolarized substrates by magnetic resonance shows great clinical promise for assessment of critical biochemical processes in real time. Due ...

Three-dimensional Particle Tracking Velocimetry for Turbulence Applications: Case of a Jet Flow

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic recording of image sequences. The basic components, features, constraints and optimization tips of a 3D-PTV topology consisting of a high-speed camera with a four-view splitter are described and discussed in this article. The technique is applied to the intermediate flow field (5 &#60;x/d &#60;25) of a circular jet at Re &#8776; 7,000. Lagrangian flow features and turbulence quantities in an Eulerian frame are estimated around ten diameters downstream of the jet origin and at various radial distances from the jet core. Lagrangian properties include trajectory, velocity and acceleration of selected particles as well as curvature of the flow path, which are obtained from the Frenet-Serret equation. Estimation of the 3D velocity and turbulence fields around the jet core axis at a cross-plane located at ten diameters downstream of the jet is compared with literature, and the power spectrum of the large-scale streamwise velocity motions is obtained at various radial distances from the jet core.

A three-dimensional particle tracking velocimetry (3D-PTV) system based on a high-speed camera with a four-view splitter is described here. The technique is applied to a jet flow from a circular pipe in the vicinity of ten diameters downstream at Reynolds number Re &#8776; 7,000.

Tridimensional Velocímetro de Partículas de Rastreamento for Applications Turbulência: Case de um fluxo de Jet

3D-PTV is a quantitative flow measurement technique that aims to track the Lagrangian paths of a set of particles in three dimensions using stereoscopic ...

Colloidal Synthesis of Nanopatch Antennas for Applications in Plasmonics and Nanophotonics

We present a method for colloidal synthesis of silver nanocubes and the use of these in combination with a smooth gold film, to fabricate plasmonic nanoscale patch antennas. This includes a detailed procedure for the fabrication of thin films with a well-controlled thickness over macroscopic areas using layer-by-layer deposition of polyelectrolyte polymers, namely poly(allylamine) hydrochloride (PAH) and polystyrene sulfonate (PSS). These polyelectrolyte spacer layers serve as a dielectric gap in between silver nanocubes and a gold film. By controlling the size of the nanocubes or the gap thickness, the plasmon resonance can be tuned from about 500 nm to 700 nm. Next, we demonstrate how to incorporate organic sulfo-cyanine5 carboxylic acid (Cy5) dye molecules into the dielectric polymer gap region of the nanopatch antennas. Finally, we show greatly enhanced fluorescence of the Cy5 dyes by spectrally matching the plasmon resonance with the excitation energy and the Cy5 absorption peak. The method presented here enables the fabrication of plasmonic nanopatch antennas with well-controlled dimensions utilizing colloidal synthesis and a layer-by-layer dip-coating process with the potential for low cost and large-scale production. These nanopatch antennas hold great promise for practical applications, for example in sensing, ultrafast optoelectronic devices and for high-efficiency photodetectors.

A protocol for the colloidal synthesis of silver nanocubes and fabrication of plasmonic nanoscale patch antennas with sub-10 nm gaps is presented.

Coloidal Síntese de nanopatch Antenas para aplicações em plasmônica e Nanophotonics

We present a method for colloidal synthesis of silver nanocubes and the use of these in combination with a smooth gold film, to fabricate plasmonic ...

Fabrication of Polymer Microspheres for Optical Resonator and Laser Applications

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, interface precipitation, and mini-emulsion. In all methods, well-defined, micrometer-sized spheres are obtained from a self-assembling process in solution. The vapor diffusion method can result in spheres with the highest sphericity and surface smoothness, yet the types of the polymers able to form these spheres are limited. On the other hand, in the mini-emulsion method, microspheres can be made from various types of polymers, even from highly crystalline polymers with coplanar, &#960;-conjugated backbones. The photoluminescent (PL) properties from single isolated microspheres are unusual: the PL is confined inside the spheres, propagates at the circumference of the spheres via the total internal reflection at the polymer/air interface, and self-interferes to show sharp and periodic resonant PL lines. These resonating modes are so-called "whispering gallery modes" (WGMs). This work demonstrates how to measure WGM PL from single isolated spheres using the micro-photoluminescence (&#181;-PL) technique. In this technique, a focused laser beam irradiates a single microsphere, and the luminescence is detected by a spectrometer. A micromanipulation technique is then used to connect the microspheres one by one and to demonstrate the intersphere PL propagation and color conversion from coupled microspheres upon excitation at the perimeter of one sphere and detection of PL from the other microsphere. These techniques, &#181;-PL and micromanipulation, are useful for experiments on micro-optic application using polymer materials.

Protocols for the synthesis of microspheres from polymers, the manipulation of microspheres, and micro-photoluminescence measurements are presented.

Fabricação de Microsferas de Polímeros para Resonadores Ópticos e Aplicações Laser

This paper describes three methods of preparing fluorescent microspheres comprising &#960;-conjugated or non-conjugated polymers: vapor diffusion, ...

Protocol for the Evaluation of MRI Artifacts Caused by Metal Implants to Assess the Suitability of Implants and the Vulnerability of Pulse Sequences

As the number of magnetic resonance imaging (MRI) scanners and patients with medical implants is constantly growing, radiologists increasingly encounter metallic implant-related artifacts in MRI, resulting in reduced image quality. Therefore, the MRI suitability of implants in terms of artifact volume, as well as the development of pulse sequences to reduce image artifacts, are becoming more and more important. Here, we present a comprehensive protocol which allows for a standardized evaluation of the artifact volume of implants on MRI. Furthermore, this protocol can be used to analyze the vulnerability of different pulse sequences to artifacts. The proposed protocol can be applied to T1- and T2-weighted images with or without fat-suppression and all passive implants. Furthermore, the procedure enables the separate and three-dimensional identification of signal loss and pile-up artifacts. As previous investigations differed greatly in evaluation methods, the comparability of their results was limited. Thus, standardized measurements of MRI artifact volumes are necessary to provide better comparability. This may improve the development of the MRI suitability of implants and better pulse sequences to finally improve patient care.

We describe a standardized method to evaluate magnetic resonance imaging artifacts caused by implants to estimate the suitability of the implants for magnetic resonance imaging and/or the vulnerability of different pulse sequences to metallic artifacts simultaneously.

Protocolo para a avaliação de MRI artefatos causados pelo Metal implantes para avaliar a adequação dos implantes e a vulnerabilidade das sequências de pulso

As the number of magnetic resonance imaging (MRI) scanners and patients with medical implants is constantly growing, radiologists increasingly encounter ...

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in industry. The wettability of the produced surface was analyzed by bouncing drop experiments and the topography was analyzed by confocal microscopy. In addition, we show various methodologies to measure its durability and anti-icing properties. Superhydrophobic surfaces hold a special texture that must be preserved to keep their water-repellency. To fabricate durable surfaces, we followed two strategies to incorporate a resistant texture. The first strategy is a direct incorporation of roughness to the metal substrate by acid etching. After this surface texturization, the surface energy was decreased by silanization or fluoropolymer deposition. The second strategy is the growth of a ceria layer (after surface texturization) that should enhance the surface hardness and corrosion resistance. The surface energy was decreased with a stearic acid film.
The durability of the superhydrophobic surfaces was examined by a particle impact test, mechanical wear by lateral abrasion, and UV-ozone resistance. The anti-icing properties were explored by studying the ability to repeal subcooled water, freezing delay, and ice adhesion.

We illustrate several methodologies to produce superhydrophobic metal surfaces and to explore their durability and anti-icing properties.

Fabricação de superfícies de Metal Superhydrophobic para aplicações antigelo

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in ...

Controllable Nucleation of Cavitation from Plasmonic Gold Nanoparticles for Enhancing High Intensity Focused Ultrasound Applications

In this study, plasmonic gold nanoparticles were simultaneously exposed to pulsed near-infrared laser light and high intensity focused ultrasound (HIFU) for the controllable nucleation of cavitation in tissue-mimicking gel phantoms. This in vitro protocol was developed to demonstrate the feasibility of this approach, for both enhancement of imaging and therapeutic applications for cancer. The same apparatus can be used for both imaging and therapeutic applications by varying the exposure duration of the HIFU system. For short duration exposures (10 &#181;s), broadband acoustic emissions were generated through the controlled nucleation of inertial cavitation around the gold nanoparticles. These emissions provide direct localization of nanoparticles. For future applications, these particles may be functionalized with molecular-targeting antibodies (e.g. anti-HER2 for breast cancer) and can provide precise localization of cancerous regions, complementing routine diagnostic ultrasound imaging. For continuous wave (CW) exposures, the cavitation activity was used to increase the localized heating from the HIFU exposures resulting in larger thermal damage in the gel phantoms. The acoustic emissions generated from inertial cavitation activity during these CW exposures was monitored using a passive cavitation detection (PCD) system to provide feedback of cavitation activity. Increased localized heating was only achieved through the unique combination of nanoparticles, laser light and HIFU. Further validation of this technique in pre-clinical models of cancer is necessary.

This protocol demonstrates the controllable nucleation of cavitation in gel phantoms, through simultaneous exposure to both near-infrared pulsed laser light and high intensity focused ultrasound (HIFU). The cavitation activity can then be used for enhancing imaging and/or therapeutic uses of HIFU.

Controlável nucleação de cavitação de nanopartículas de ouro plasmônico para reforçar a alta intensidade focada aplicações de ultra-som

In this study, plasmonic gold nanoparticles were simultaneously exposed to pulsed near-infrared laser light and high intensity focused ultrasound (HIFU) ...

Optimization, Test and Diagnostics of Miniaturized Hall Thrusters

Miniaturized spacecraft and satellites require smart, highly efficient and durable low-thrust thrusters, capable of extended, reliable operation without attendance and adjustment. Thermochemical thrusters which utilize thermodynamic properties of gases as a means of acceleration have physical limitations on their exhaust gas velocity, resulting in low efficiency. Moreover, these engines demonstrate extremely low efficiency at small thrusts and may be unsuitable for continuously operating systems which provide real-time adaptive control of the spacecraft orientation, velocity and position. In contrast, electric propulsion systems which use electromagnetic fields to accelerate ionized gases (i.e., plasmas) do not have any physical limitation in terms of exhaust velocity, allowing virtually any mass efficiency and specific impulse. Low-thrust Hall thrusters have a lifetime of several thousand hours. Their discharge voltage ranges between 100 and 300 V, operating at a nominal power of &lt;1 kW. They vary from 20 to 100 mm in size. Large Hall thrusters can provide fractions of millinewton of thrust. Over the past few decades, there has been an increasing interest in small mass, low power, and high efficiency propulsion systems to drive satellites of 50-200 kg. In this work, we will demonstrate how to build, test, and optimize a small (30 mm) Hall thruster capable of propelling a small satellite weighing about 50 kg. We will show the thruster operating in a large space environment simulator, and describe how thrust is measured and electric parameters, including plasma characteristics, are collected and processed to assess key thruster parameters. We will also demonstrate how the thruster is optimized to make it one of the most efficient small thrusters ever built. We will also address challenges and opportunities presented by new thruster materials.

Here, we present a protocol to test and optimize space propulsion systems based on miniaturized Hall-type thrusters.

Otimização, teste e diagnóstico dos propulsores miniaturizados Hall

Miniaturized spacecraft and satellites require smart, highly efficient and durable low-thrust thrusters, capable of extended, reliable operation without ...

Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites

In this work, an easy, low-cost, and widely applicable method was developed to improve the compatibility between the ceramic fillers and the polymer matrix by adding 3-aminopropyltriethoxysilane (KH550) as a coupling agent during the fabrication process of BaTiO3-P(VDF-CTFE) nanocomposites through solution casting. Results show that the use of KH550 can modify the surface of ceramic nanofillers; therefore, good wettability on the ceramic-polymer interface was achieved, and the enhanced energy storage performances were obtained by a suitable amount of the coupling agent. This method can be used to prepare flexible composites, which is highly desirable for the production of high-performance film capacitors. If an excessive amount of coupling agent is used in the process, the non-attached coupling agent can participate in complex reactions, which leads to a decrease in dielectric constant and an increase in dielectric loss.

Here, we demonstrate a simple and low-cost solution-casting process to improve the compatibility between the filler and the matrix of polymer-based nanocomposites using surface modified BaTiO3 fillers, which can effectively enhance the energy density of the composites.

Aplicação de um agente de acoplamento para melhorar as propriedades dielétricas de nanocompactos baseados em polímeros

In this work, an easy, low-cost, and widely applicable method was developed to improve the compatibility between the ceramic fillers and the polymer ...