Dieses Forschungsprojekt mit Mitteln aus dem European Research Council unter der Europäischen Gemeinschaft Siebten Rahmenprogramms (FP7/2007-2013) / ERC Finanzhilfevereinbarung n ° 242710 erhalten und wurde zusätzlich durch das Human Frontier Science Program und dem Emmy Noether-Programm der Deutschen unterstützt Forschungsgemeinschaft (SCHR 995/2-1).

<ol>
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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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Kritischen Aspekte bei der Herstellung von hyperpolarisiertem Xenon Sauerstoff sind Verunreinigungen in der Gasverteiler einschließlich der Pumpzelle und eine ausreichende Beleuchtung der Zelle mit zirkular polarisiertem Licht. Der oben erwähnte Glühbirne Test ist ein einfacher Weg, um schädliche Sauerstoffkonzentrationen detektieren beim Übertragen Rubidium. Das Alkalimetall kann der glänzenden Oberfläche durch die Zeit, die Zelle in dem Polarisator installiert verlieren. . Einmal, jedoch kann eine ausreichende ...

Hyperpolarisierte Agenten gewinnen zunehmend an Aufmerksamkeit für NMR / MRI-Anwendungen, da sie die Empfindlichkeit Problem unter Umständen lösen können 2. Drei wichtige Ansätze werden derzeit verwendet (dynamische Kernpolarisation, DNP; para-Wasserstoff-induzierte Polarisation, PHIP und Spinaustausch optisches Pumpen, SEOP), dass alle einen künstlich erhöht Spinpopulation Differenz außerhalb eines NMR-Magneten vor der eigentlichen Spektroskopie oder Bildgebung Experiment vorzubereiten . Hier beschreiben wir die Funktions-und Wirkungsweise einer Einrichtung SEOP die für die Produktion von hyperpolarisiertem 129 Xe in Lösungszustand verwendet Experimenten optimiert wurde. Ein wesentlicher Bestandteil ist eine intensive Lichtquelle, Infrarot-Photonen bei 795 nm. Laser-Dioden-Arrays (LDA) sind bequem, die eine hohe Leistung&gt; 100 W zu vertretbaren Kosten bieten. In vielen Aufbauten wird die LDA in eine optische Faser emittiert, daß mehr oder weniger die Polarisation beibehält the Laserlicht. Um eine ausreichende SEOP Prozesses garantieren elliptische Polarisation muss in Zirkularpolarisation von hoher Reinheit umgewandelt werden. Hauptkomponenten der Polarisationsoptik sind in den 1 und 2 gezeigt und der Einrichtung des Systems ist schematisch in ergänzenden Film 1 erläutert. Das zirkulare Polarisieren von Licht wir zuerst den Faserende an einen primären Strahlaufweitungsoptik (zB ein Faserkollimator) zum Reduzieren Leistungsdichte. Das Licht geht dann durch einen polarisierenden Strahlteilerwürfel, Erzeugen linear polarisiertes Licht. Durch Drehen dieses Würfels können wir die bevorzugte Achse des verbleibenden Polarisation mit einem Leistungsmesser bestimmen. Maximale Übertragungsrate entspricht der Situation, wo der schnellen Achse des Würfels mit dem Hauptlichtbündel Polarisationsachse ausgerichtet ist. Cubes mit hohen Extinktionskoeffizienten (100.000: 1 oder besser) ergeben eine gute Trennung der Polarisationskomponenten. Dies kann getestet werdenVerwendung eines zweiten Strahlteilerwürfel als Analysator, der gedreht wird, während das erste für maximale Transmission des außerordentlichen Strahls ausgerichtet ist. Sobald die lineare Polarisation des durchgelassenen Lichts bestätigt wurde, wird ein λ / 4 Plättchen für 795 nm ausgelegt in den außerordentlichen Strahl zu konvertieren in Zirkularpolarisation linearen eingeführt. Zu diesem Zweck ist die schnelle Achse der Wellenplatte um 45 ° gedreht gegenüber dem Strahlteilerwürfel schnellen Achse. (Falls gewünscht, können kreisförmige Polarisation des reflektierten Strahls mit seinen gewöhnlichen linearen Polarisation senkrecht zu der außerordentlichen Strahls auf eine ähnliche Weise erreicht werden.) Die Qualität der Zirkularpolarisation kann mit einem zweiten Strahlteilerwürfel, die konstante Transmission bei Drehung nachgeben sollte getestet werden. Ein sekundärer Strahlaufweitungsoptik (zB zwei Linsen in einer Galilei-Fernrohr-Konfiguration), dann erhöht sich die Strahldurchmesser vollständig illuminate die Glaszelle für den Pumpvorgang in einem Ofen ein. Absorption des Laserlichts durch Rb-Dampf in der Zelle wird durch ein Stiftloch hinter der Pumpzelle am Ende des Kastens überwacht: einen Kollimator sammelt ein attenuiertes IR-Strahls, mit einem optischen Spektrometer analysiert werden (siehe Abbildung 3 für Pumpzelle Setup ). Ein Heizmechanismus außerhalb der Pumpzelle eine teilweise verdampft Rb Tröpfchens sitzt innerhalb der Zelle (4a) und somit bewirkt Laserlichtabsorption. Dichte des Dampfes kann über den Heizsollwert des jeweiligen PID-Regler eingestellt werden. Hohe Temperaturen (ca. 190 ° C) sind gut für kompakte Setups, wo die Xenon hat eine begrenzte Menge an Zeit für den Aufbau Polarisation. Das Gasgemisch, das Xe, N 2 und He durchströmt die Pumpzelle entgegengesetzt zur Richtung des Laserstrahls (Abbildung 3). Ein äußeres Magnetfeld mit dem Laserstrahl ausgerichtet ist sichergestellt, dass the IR-Photonen werden nur Pumpen ein Rb Übergang. Relaxation der Elektronen Zustände schnell und muss nicht strahlende zur Emission von IR-Photonen mit &#39;falschen&#39; Polarisierung zu vermeiden. Hier kommt die N 2 ins Spiel als Quenchgas. Schließlich baut der Rb System eine Überbevölkerung eines der Grundzustaenden während die andere kontinuierlich durch den Laser (Abbildung 5) abgereichert. Xenon immer in engem Kontakt mit den Atomen Rb erfährt Spin-Spin-Wechselwirkungen und die Elektronenspinpolarisation wird auf Xe Kerne in Flip-Flop-Prozesse übertragen. Das hyperpolarisierte Gas fließt aus der Pumpzelle enthält Spuren von Rb-Dampf, daß Kondensat an der Schlauchwand in wenigen cm der Auslaß aufgrund der niedrigen Temperatur (ähnlich Figur 4b). In-vivo-Anwendungen sind jedoch zusätzliche Elimination erfordern würde der Alkali-(zB durch eine Kühlfalle), während in vitro experiments können sicher mit dem Gas durchgeführt werden, wie es die Hyperpolarisator verlässt. Teflonschlauch verbindet den Polarisator Auslass mit dem Einlass eines Glasapparatur NMR Experimente an Testlösungen durchzuführen. Massendurchflussregler verwendet, um die Menge von Xe einströmende NMR Einstellung anpassen. Sie werden durch Befehle in der NMR-Pulssequenz ausgelöst. Nach Überprüfung der erzielte Polarisations-Enhancement kann das Gas als NMR / MRI Kontrastmittels in Lösungszustand Experimente verwendet werden. Xe hat eine gewisse Löslichkeit in Wasser (4,5 mM / atm) und anderen Lösungsmitteln. Es kann somit bereits in eigener dienen als Kontrastmittel, um die Verteilung von einigen Flüssigkeiten anzuzeigen. Es ist jedoch auch möglich, die NMR-aktiven Kernen, bestimmte Moleküle zu koppeln, um molekular-spezifische Informationen durch die sonst Inertgas erwerben. Durch die Bereitstellung einer molekularen Wirt für den gelösten Xe, ist es möglich, molekularen Spezifität zur Xe-NMR-Signal zu übertragen. Dies bietet die Möglichkeit,Design funktionalisierten Kontrastmitteln - auch als Biosensoren - wenn eine solche Wirtstruktur an ein Targeting-Einheit, die auf bestimmte Analyten von biomedizinischem Interesse (Abbildung 6) bindet, gekoppelt ist. Weitere Empfindlichkeitsanhebung ist erforderlich, wenn der Biosensor in Konzentrationen, die niedriger sind für MR-Kontrastmitteln (&lt;100 uM) erkannt werden sollte. Dies kann durch chemische Austausch Sättigungstransfer (CEST) erreicht werden. Dieses Verfahren erfasst die Biosensor indirekt durch Zerstören der Magnetisierung des caged Xe und Beobachten der Signaländerung von freien Xe in Lösung. Da das hyperpolarisierte Kerne werden kontinuierlich nach einigen 10 ms, viele 100-1000 Kerne Übertragung der Information auf dem erfassten Pools ersetzt und das Signal verstärken ca. 10 3-fach (siehe Film 2).

<table border="1"><tbody><tr><td> Name des Reagenzes </td><td> Firma </td><td> Katalog-Nummer </td><td> Kommentare (optional) </td></tr><tr><td> Rb Ingot </td><td> Sigma-Aldrich </td><td> 276.332-1G </td><td></td></tr><tr><td> P 4 O 10 </td><td> Sigma-Aldrich </td><td> 79.610-500G </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> Laser-System </td><td> QPC Laser / Laser Operationen </td><td> BrightLock 50 </td><td></td></tr><tr><td> Vakuum-System </td><td> Pfeiffer </td><td> HiCube </td><td></td></tr><tr><td> Thermoelemente </td><td> NewportOmega </td><td> SA2F-KI-3M </td><td></td></tr><tr><td> Silicon Heizung </td><td> Newport Omega </td><td> FMA5514 </td><td></td></tr><tr><td> Druckmessumformer </td><td> Newport Omega </td><td> PR 33X-V-10 </td><td></td></tr><tr><td> Prozess-Anzeige </td><td> Newport Omega </td><td> INFCP-100B </td><td></td></tr><tr><td> Mass Flow Controller </td><td> Newport Omega </td><td> MFC </td><td></td></tr><tr><td> PID-Regler </td><td> Newport Omega </td><td> CN7800 </td><td></td></tr><tr><td> Control Software </td><td> Newport Omega </td><td> DasyLab </td><td></td></tr><tr><td> Datenerfassung </td><td> Newport Omega </td><td> DAQBOARD 3000 </td><td></td></tr><tr><td> Vakuumsensor </td><td> Oerlikon </td><td> TTR91 </td><td></td></tr><tr><td> Vakuum-Controller </td><td> Vacom </td><td> MVC-3 </td><td></td></tr><tr><td> Kollimator </td><td> Thorlabs </td><td> F810SMA-780 </td><td></td></tr><tr><td> Polarisierenden Strahlteilerwürfel </td><td> Thorlabs </td><td> GL15-B </td><td></td></tr><tr><td> λ / 4 Plättchen </td><td> Thorlabs </td><td> WPQ10M-780 </td><td></td></tr><tr><td> Strahlaufweitung Objektive </td><td> Thorlabs </td><td></td><td></td></tr><tr><td> Optisches Spektrometer </td><td> Ocean Optics </td><td> HR4000 </td><td></td></tr><tr><td> Lichtleitfaser </td><td> Ocean Optics </td><td></td><td></td></tr><tr><td> Niederdruck-NMR-Röhrchen </td><td> Wilmad </td><td> 513-7LPV-7 </td><td></td></tr><tr><td> 5mm NMR-Röhrchen </td><td> Sigma-Aldrich </td><td> HX58.1 </td><td></td></tr><tr><td> Helmholtz-Spulen </td><td> Phywe </td><td> 06960-00 </td><td></td></tr><tr><td> Fused silica Kapillaren </td><td> Polymicro </td><td> TSG 250350 </td><td></td></tr></tbody></table>

hyperpolarized xenon for nmr and mri applications

Kernspinresonanz (NMR)-Spektroskopie und-Imaging (MRI) leiden unter inneren geringe Empfindlichkeit weil selbst starke externe Magnetfelder von ~ 10 T nur einen kleinen nachweisbar net-Magnetisierung der Probe bei Raumtemperatur 1 zu erzeugen. Folglich basieren die meisten NMR und MRI-Anwendungen auf dem Nachweis von Molekülen an relativ hohen Konzentration (zB Wasser zur Bildgebung biologischer Gewebe) oder erfordern übermäßige Erfassungszeiten. Dies schränkt unsere Fähigkeit, die sehr nützlich molekularen Spezifität von NMR-Signalen für viele biochemische und medizinische Anwendungen zu nutzen. Jedoch neuartige Ansätze sind in den letzten Jahren herauskristallisiert: Manipulation der erfassten Spinspezies vor der Detektion im NMR / MRI-Magneten drastisch erhöhen kann die Magnetisierung und damit ermöglicht den Nachweis von Molekülen bei viel niedrigeren Konzentration 2. Hier präsentieren wir eine Methode zur Polarisation von einer Xenon-Gas-Gemisch (2-5% Xe, 10%N 2, He-Balance) in einem kompakten Aufbau mit einem ca. 16000-fache Signalverstärkung. Modernen Line-Diodenlasern verengte ermöglichen effiziente Polarisation 7 und sofortigen Nutzung Gasgemisch auch wenn das Edelgas nicht von den anderen Komponenten getrennt sind. Die Vorrichtung SEOP erklärt und Bestimmung der Spinpolarisation erreicht wird zur Leistungsregelung des Verfahrens demonstriert. Die hyperpolarisiertem Gas können Leerraum Bildgebung verwendet werden, einschließlich Gasstrom Bildgebung oder Diffusion Studien an den Schnittstellen mit anderen Materialien 8,9. Darüber hinaus ist das NMR-Signal Xe extrem empfindlich auf seiner molekularen Umgebung 6. Dies ermöglicht die Möglichkeit, es als NMR / MRI-Kontrastmittel verwenden, wenn in wässriger Lösung mit funktionalisierten molekularen Gastgeber, die vorübergehend fangen das Gas 10,11 aufgelöst. Direkte Erfassung und hohe Empfindlichkeit indirekten Nachweis solcher Konstrukte wird sowohl spektroskopische und Imaging-Modus gezeigt. &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

Die Produktion von hyperpolarisiertem Xenon mittels Spin-Austausch optisches Pumpen (SEOP) beschrieben. Dieses Verfahren ergibt ein ~ 10.000-fache Verstärkung der Kernspinpolarisation von Xe-129 und hat Anwendungen in Kernresonanzspektroskopie und Bildgebung. Beispiele von Gasphase und Lösungszustand Experimenten angegeben.

Hyperpolarisiertem Xenon für NMR-und MRI-Anwendungen

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

19.5K Aufrufe.  Leibniz-Institut für Molekulare Pharmakologie. Die Produktion von hyperpolarisiertem Xenon mittels Spin-Austausch optisches Pumpen (SEOP) beschrieben. Dieses Verfahren ergibt ein ~ 10.000-fache Verstärkung der Kernspinpolarisation von Xe-129 und hat Anwendungen in Kernresonanzspektroskopie und Bildgebung. Beispiele von Gasphase und Lösungszustand Experimenten angegeben.

Serie: 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.

Solid-State-Graft Copolymer Elektrolyte für Lithium-Batterie-Anwendungen

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

Forschung

Ingenieurwesen

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.

Die Verwendung eines Mehrfach Dynamische einzelner Enzym-Phantom für Studien von hyperpolarisiertem Magnetic Resonance Agents

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.

Dreidimensionale Particle Tracking Velocimetry für Turbulence Anwendungen: Fall eines Jet Fluss

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.

Kolloidales Synthese von Nanopatch Antennen für Anwendungen in Plasmonics und 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.

Herstellung von Polymer-Mikrosphären für optische Resonator- und Laseranwendungen

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.

Protokoll für die Bewertung von MRI Artefakte verursacht durch Metall-Implantate um die Eignung der Implantate und die Anfälligkeit von Impulsfolgen zu bewerten

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.

Herstellung von Superhydrophob Metalloberflächen für Anti-Icing-Anwendungen

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.

Steuerbare Keimbildung der Kavitation von Plasmonische Gold-Nanopartikel für die Verbesserung der hohen Intensität konzentriert Ultraschallanwendungen

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.

Optimierung, Test und Diagnose von miniaturisierten Hall Triebwerke

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.

Anwendung eines Kupplungsmittels zur Verbesserung der dielektrischen Eigenschaften polymerbasierter Nanokompositen

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