Este trabajo fue apoyado por la oficina de investigación Naval (ONR N00014-15-1-0020) [Tkacik y Keanini] y realizado en la Universidad de North Carolina en Motorsports investigación laboratorio pulido Charlotte media fue donado por Rosler.

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T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-time+behavior+of+the+velocity+autocorrelation+function+for+a+fluid+of+soft+repulsive+particles.">Long-time behavior of the velocity autocorrelation function for a fluid of soft repulsive particles.</a> Phys. Rev. Lett. 33, 277-280 (1970).</li><li>Lovesey, S. W., Lovesey, S. W., Springer, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Dynamics of solids and liquids by neutron scattering. , (1977).</li><li>Forster, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Hydrodynamic fluctuations, broken symmetry, and correlation functions. , (1990).</li><li>Mountain, R. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generalized+hydrodynamics.">Generalized hydrodynamics.</a> Adv. Mol. Relax. Processes. 9, 225-291 (1977).</li><li>Zwanzig, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-correlation+functions+and+transport+coefficients+in+statistical+mechanics.">Time-correlation functions and transport coefficients in statistical mechanics.</a> Ann. Rev. Phys. Chem. 16, 67-102 (1965).</li><li>Keanini, R. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macroscopic+liquid-state+molecular+hydrodynamics.">Macroscopic liquid-state molecular hydrodynamics.</a> Sci. Rep. 7, 41658 (2017).</li><li>Kushick, J., Berne, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+attractive+forces+in+self-diffusion+in+dense+Lennard-Jones+fluids.">Role of attractive forces in self-diffusion in dense Lennard-Jones fluids.</a> J. Chem. Phys. 59 (7), 3732-3736 (1973).</li><li>Mullany, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+application+of+computational+fluid+dynamics+to+vibratory+finishing+processes.">The application of computational fluid dynamics to vibratory finishing processes.</a> CIRP Annals. , (2017).</li><li>Fleischhauer, E., Azimi, F., Tkacik, P. T., Keanini, R. G., Mullany, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+particle+imaging+velocimetry+(PIV)+to+vibrational+finishing.">Application of particle imaging velocimetry (PIV) to vibrational finishing.</a> J. Mater. Process. Technol. 229, 322-328 (2016).</li><li>Navare, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Experimental and computational evaluation of a vibratory finishing process. , (2017).</li><li>Bolmatov, V., Brazhkin, V., Trachenko, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+phonon+theory+of+liquid+thermodynamics.">The phonon theory of liquid thermodynamics.</a> Sci. Rep. 2, 421 (2012).</li><li>Elton, D. C., Fernandez-Serra, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+hydrogen-bond+network+of+water+supports+propagating+optical+phonon-like+modes.">The hydrogen-bond network of water supports propagating optical phonon-like modes.</a> Nat. Commun. 7, 10193 (2016).</li><li>Pathria, R. K., Beale, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical mechanics. , (2011).</li><li>Gibbs, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Elementary principles in statistical mechanics. , (1902).</li><li>Toda, M., Kubo, R., Saito, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical physics I. , (1992).</li><li>Kubo, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Statistical+mechanical+theory+of+irreversible+processes.">Statistical mechanical theory of irreversible processes.</a> I. J. Phys. Soc. Japan. 12, 570-586 (1957).</li><li>Kubo, R., Toda, M., Hashitsume, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Statistical physics II: nonequilibrium statistical mechanics. , (1991).</li></ol>

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Para utilizar pilas de grano vibrado como análogos macroscópicos para investigar procesos hidrodinámicos moleculares, un experimentador debe, por un lado, aprender y utilizar cuatro medidas básicas y por el otro, dominar algunos elementos básicos de equilibrio y mecánica estadística de no equilibrio. Centrarse primero en las mediciones experimentales, estas incluyen: i) medición de la dinámica individual de grano a través de la medición de la función de autocorrelación simple partícula velocidad, ii) medici...

Molecular hidrodinámica estudia la dinámica y la mecánica estadística de moléculas individuales y colecciones de moléculas en líquidos. Entre las muchas técnicas experimentales desarrollaron para el estudio de sistemas moleculares hidrodinámica1,2, dispersión de la luz1,2,3, simulaciones dinámica molecular4, 5,6,7 y, en menor medida, de la dispersión inelástica de neutrones8 han sido utilizados más comúnmente. Por desgracia, limitaciones significativas Conecte a las dos últimas técnicas. Simulaciones de dinámica molecular (MD), por ejemplo: i) están limitadas a pequeñas espacial y temporal <img alt="Equation 1" src="/files/ftp_upload/56632/56632eq1.jpg"> dominios que contienen relativamente pocas moléculas <img alt="Equation 2" src="/files/ftp_upload/56632/56632eq2.jpg"> </img>, ii) requieren el uso de aproximado entre partículas potenciales, iii) suelen presentar periódica condiciones de contorno, válidas bajo condiciones de flujo a granel de no-equilibrio y iv) en la actualidad, no pueden responder la pregunta fundamental de cómo molecular-escala dinámica, que implica las moléculas individuales o colecciones de moléculas, son afectadas por y par de vuelta a granel, no equilibrio fluido. La principal limitación asociada a la dispersión de neutrones está ligada a la dificultad de acceder al número limitado de fuentes de neutrón viga disponibles.
Para proporcionar el contexto para la técnica experimental análoga presentada en este artículo, se destacan técnicas de dispersión de la luz aplicadas a los fluidos de gas denso y estado líquido simple. En un experimento de dispersión de la luz típico, se dirige un haz de luz láser polarizada a un volumen pequeño interrogatorio que contiene una muestra de líquido estacionaria. Luz dispersada de las moléculas dentro de la muestra entonces se detecta en un ángulo fijo respecto al haz incidente. Según el régimen de dinámico molecular de interés, la detección y análisis de la señal luminosa dispersa incorpora luz filtrado o mezcla de métodos de detección de luz. Señalados por Berna y Pecora1, técnicas de filtración que sonda dinámica molecular del estado líquido a tiempo escala menor <img alt="Equation 3" src="/files/ftp_upload/56632/56632eq3.jpg"> s, introducir un interferómetro de la dispersión o rejilla de difracción y permiten la exploración de la densidad espectral de la luz dispersada. Mezcla de técnicas, utilizadas para la escala de tiempo lenta dinámica, óptica <img alt="Equation 4" src="/files/ftp_upload/56632/56632eq4.jpg"> s, por el contrario, incorporar un analizador autocorrelador o espectro de la dispersión, en el que el contenido espectral de la señal dispersa se extrae de la luz dispersada medida intensidad.
En general, láser sondas, por lo menos las que operan en el rango visible del espectro, con longitudes de onda mucho más largas que el espacio característico entre las moléculas del estado líquido. En estas circunstancias, el haz de la sonda excita cinco colectiva, escala de tiempo lenta, modos hidrodinámico de larga longitud de onda2,9,10 (lentos en comparación con la frecuencia de colisión característico): dos viscosamente amortiguación, en propagación de ondas de sonido, dos modos de Vorticidad desacoplados, puramente difusivo y un modo solo difusión térmica (entropía). Los modos de sonido muy contentos en la dirección (longitudinal) del haz incidente, mientras que los modos en torbellino se excitan en la dirección transversal.
Considerando puramente experimental de dispersión de técnicas, de dos cuestiones fundamentales, en el centro del equilibrio y mecánica estadística de no equilibrio molecular, estado líquido sistemas, permanecen más allá de la luz y las medidas de dispersión de neutrones: 1) rigurosos argumentos9,11 muestran que la dinámica de colisión - y sub-collision-escala de tiempo al azar, de estado líquido las moléculas individuales, sujetos a la dinámica newtoniana clásica o dinámica cuántica, puede proceder a su refundición en el forma de ecuaciones de Langevin generalizadas (GLE). GLE, a su vez, conforman una herramienta teórica central en el estudio de la mecánica estadística de no equilibrio de las moléculas en los gases densos y líquidos. Por desgracia, ya que la dinámica de moléculas individuales (no macromolecular) no se puede resolver por cualquier técnica de dispersión, actualmente no hay manera directa, más allá de simulaciones, para probar la validez de la GLE. 2) una hipótesis fundamental estará en el centro de dinámica de fluidos de continuum macroscópico, así como microescala molecular hidrodinámica, postula en longitud - y escalas de tiempo grande en relación con la colisión, pero pequeña en relación con el continuum y diámetros moleculares y tiempo-escalas de la longitud, prevalece equilibrio termodinámico local (LTE). En continuo flujo y calor transferencia modelos, como las ecuaciones de Navier-Stokes (NS), la asunción de LTE es necesario9 para pareja intrínsecamente no-equilibrio, flujo continuo-escala y características de transporte de energía, como tensiones de esquileo viscosas y conducción térmica: a estrictamente equilibrio propiedades termodinámicas, como temperatura y energía interna. Asimismo, mientras que el transporte de momentum y energía de microescala son procesos intrínsecamente no-equilibrio, lo que refleja la aparición de masa acoplada, en microescala, impulso y corrientes de energía, los modelos de estos procesos de microescala asumen que las corrientes representan las perturbaciones pequeñas de LTE9. Una vez más, al mejor de nuestro conocimiento, no han sido pruebas experimentales directas de la asunción de LTE. En particular, parece que no hay experimentos de dispersión hidrodinámica molecular se han intentado en flujos de fluidos densos, móviles, no equilibrio.
En este trabajo, describiremos una técnica experimental análoga en la cual la partículas macroscópicas, solo y la dinámica de la partícula colectiva de montones de grano vibrado, medidos utilizando estándar partícula Imaging Velocimetry (PIV), puede utilizarse para predecir indirectamente, interpretar y exponer solo y multi molecule hidrodinámica en gases densos y líquidos. Los elementos físicos y teóricos que permitan a la técnica propuesta se afirmó en un reciente artículo publicado por nuestro grupo12. Experimentalmente, el sistema macroscópico debe exhibir: (i) una tendencia sostenida a la local, equilibrio mecánico estadístico de macroescala y (ii), lineares llegadas del equilibrio que imitan las fluctuaciones de no equilibrio (débiles) observado en sistemas hidrodinámicos moleculares. Teóricamente: modelos de microescala i clásico que describe el equilibrio y la mecánica estadística débil no equilibrio de denso, sistemas N-partículas interactuantes se deben replantear en forma de macroescala, y (ii) los modelos resultantes de la macroescala deben confiablemente predecir la dinámica de partícula única y múltiple, de cortas, partícula-colisión-plazos para largo, continuo-flujo-plazos.
Aquí, presentamos un protocolo experimental detallado así como representante de resultados obtenidos por la nueva técnica. En contraste con simulaciones y luz y métodos de dispersión de neutrones, la nueva técnica permite, por primera vez, un estudio detallado de procesos hidrodinámicos moleculares dentro fluyendo, fuertemente no-equilibrio, densa de gases y líquidos.

<table>
	<tbody>
		<tr>
			<td>Vibratory Polishing Bowl</td>
			<td>Raytech</td>
			<td>AV-75</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Meter</td>
			<td>Peristaltic Pumps</td>
			<td>913 Mity Flex</td>
			<td></td>
		</tr>
		<tr>
			<td>Scale</td>
			<td>Pelouze</td>
			<td>4040</td>
			<td></td>
		</tr>
		<tr>
			<td>Triaxial Accelerometer</td>
			<td>PCB Piezotronics</td>
			<td>PCB 356B11</td>
			<td>Accelerometer with Sensor Signal Conditioner</td>
		</tr>
		<tr>
			<td>Data Acquisition Computer</td>
			<td>IBM</td>
			<td>Thinkpad</td>
			<td>Used with high speed camera</td>
		</tr>
		<tr>
			<td>High Speed Camera</td>
			<td>Redlake</td>
			<td>Motionxtra HG-XR</td>
			<td></td>
		</tr>
		<tr>
			<td>Zoom Lens</td>
			<td>Tamron</td>
			<td>Model A18</td>
			<td>18-250mm F/3.5-6.3&#160;</td>
		</tr>
		<tr>
			<td>High intensity Light</td>
			<td>ARRI</td>
			<td>EB 400/575 D</td>
			<td></td>
		</tr>
		<tr>
			<td>Data Processing Computer</td>
			<td>Dell</td>
			<td>Dell Precision Tower 7910</td>
			<td></td>
		</tr>
		<tr>
			<td>PIV Software&#160;</td>
			<td>Dantec Dynamics</td>
			<td>Dynamic Studio 2013</td>
			<td>version 3.41.38</td>
		</tr>
		<tr>
			<td>Data Acquisition Hardware</td>
			<td>National Instruments</td>
			<td>SCXI</td>
			<td>SCXI-1000 Chasis with SCXI 1100 Card and SCXI 1303 Adapter</td>
		</tr>
		<tr>
			<td>Data Acquisition Software</td>
			<td>National Instruments</td>
			<td>LabVIEW 2012</td>
			<td></td>
		</tr>
		<tr>
			<td>Data Processing Software</td>
			<td>MATHWORKS</td>
			<td>MATLAB</td>
			<td></td>
		</tr>
		<tr>
			<td>Polishing Media</td>
			<td>Rosler</td>
			<td>RSG 10/10S</td>
			<td>Multiple media types used (mixed, spherical, triangular)</td>
		</tr>
		<tr>
			<td>Polishing Solution</td>
			<td>Rosler</td>
			<td>FC KFL (3%)</td>
			<td>3% soap solution with water</td>
		</tr>
		<tr>
			<td>Ruled Scale</td>
			<td>Swiss Precision Instruments</td>
			<td>13-911-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Graduated Cylinder</td>
			<td>Global Scientific</td>
			<td>601082</td>
			<td></td>
		</tr>
	</tbody>
</table>

an analog macroscopic technique for studying molecular hydrodynamic processes in dense gases and liquids

Se describe un método análogo, macroscópico para el estudio de procesos hidrodinámicos de escala molecular en gases densos y líquidos. La técnica aplica un estándar líquido dinámico diagnóstico, partícula imagen velocimetry (PIV), para medir: i) las velocidades de las partículas individuales (granos), extant en colisión de grano corto, escalas de tiempo, velocidades ii) de los sistemas de partículas, en tanto corto colisión-época - y iii largo, continuo-flujo-tiempo-escalas,) modos hidrodinámicos colectivos existe en líquidos moleculares densos y iv) funciones de autocorrelación de velocidad corto - y largo-tiempo-escala, centrales para entender la dinámica de la partícula-escala en sistemas de fluidos densos, interacción. El sistema básico se compone de un sistema de proyección de imagen, fuente de luz, sensores de vibración, sistema de vibración con un software de análisis y PIV y los medios de comunicación, conocido. Se destacan requiere mediciones experimentales y un esquema de las herramientas teóricas necesarias cuando se utiliza la técnica análoga para estudiar procesos hidrodinámicos de escala molecular. La propuesta técnica proporciona una alternativa relativamente sencilla a la fotónica y métodos de dispersión utilizados tradicionalmente en estudios hidrodinámicos moleculares de la viga de neutrón.

En la presentación de resultados representativos, nos referimos a procesos de escala de tiempo continuo como ésos observados y predichos sobre escalas de tiempo, <img alt="Equation 25" src="/files/ftp_upload/56632/56632eq25.jpg"> que son largas en relación con la escala de tiempo de colisión de grano característica, <img alt="Equation 26" src="/files/ftp_upload/56632/56632eq26.jpg"> <img alt="Equation 27" src="/files/ftp_upload/56632/56632eq27.jpg"> y escala de tiempo d...

Watch this Scientific Journal Video about An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids at JoVE.com

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

Se presenta un método analógico experimentalmente accesible para el estudio de procesos hidrodinámicos moleculares en fluidos densos. La técnica utiliza la velocimetría de imagen de partículas de montones de grano vibrado, de alta-restitución y permite la observación directa, macroscópica de dinámicos procesos conocidos y predice que existen en la interacción, alta densidad de gases y liquidos.

Una técnica análoga macroscópica para el estudio de procesos hidrodinámicos Molecular en Gases densos y líquidos

An analog, macroscopic method for studying molecular-scale hydrodynamic processes in dense gases and liquids is described. The technique applies a ...

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8.4K vistas.  University of North Carolina at Charlotte. Se presenta un método analógico experimentalmente accesible para el estudio de procesos hidrodinámicos moleculares en fluidos densos. La técnica utiliza la velocimetría de imagen de partículas de montones de grano vibrado, de alta-restitución y permite la observación directa, macroscópica de dinámicos procesos conocidos y predice que existen en la interacción, alta densidad de gases y liquidos.

Video: An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids

Revealing Dynamic Processes of Materials in Liquids Using Liquid Cell Transmission Electron Microscopy

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted significant interests across the research fields of materials science, physics, chemistry and biology. The key enabling technology is a liquid cell. We fabricate liquid cells with thin viewing windows through a sequential microfabrication process, including silicon nitride membrane deposition, photolithographic patterning, wafer etching, cell bonding, etc. A liquid cell with the dimensions of a regular TEM grid can fit in any standard TEM sample holder. About 100 nanoliters reaction solution is loaded into the reservoirs and about 30 picoliters liquid is drawn into the viewing windows by capillary force. Subsequently, the cell is sealed and loaded into a microscope for in situ imaging. Inside the TEM, the electron beam goes through the thin liquid layer sandwiched between two silicon nitride membranes. Dynamic processes of nanoparticles in liquids, such as nucleation and growth of nanocrystals, diffusion and assembly of nanoparticles, etc., have been imaged in real time with sub-nanometer resolution. We have also applied this method to other research areas, e.g., imaging proteins in water. Liquid cell TEM is poised to play a major role in revealing dynamic processes of materials in their working environments. It may also bring high impact in the study of biological processes in their native environment.

We have developed a self-contained liquid cell, which allows imaging through liquids using a transmission electron microscope. Dynamic processes of nanoparticles in liquids can be revealed in real time with sub-nanometer resolution.

Revelando los procesos dinámicos de los materiales en líquidos con líquido de transmisión celular Microscopía Electrónica

The recent development for in situ transmission electron microscopy, which allows imaging through liquids with high spatial resolution, has attracted ...

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Simulation of the Planetary Interior Differentiation Processes in the Laboratory

A planetary interior is under high-pressure and high-temperature conditions and it has a layered structure. There are two important processes that led to that layered structure, (1) percolation of liquid metal in a solid silicate matrix by planet differentiation, and (2) inner core crystallization by subsequent planet cooling. We conduct high-pressure and high-temperature experiments to simulate both processes in the laboratory. Formation of percolative planetary core depends on the efficiency of melt percolation, which is controlled by the dihedral (wetting) angle. The percolation simulation includes heating the sample at high pressure to a target temperature at which iron-sulfur alloy is molten while the silicate remains solid, and then determining the true dihedral angle to evaluate the style of liquid migration in a crystalline matrix by 3D visualization. The 3D volume rendering is achieved by slicing the recovered sample with a focused ion beam (FIB) and taking SEM image of each slice with a FIB/SEM crossbeam instrument. The second set of experiments is designed to understand the inner core crystallization and element distribution between the liquid outer core and solid inner core by determining the melting temperature and element partitioning at high pressure. The melting experiments are conducted in the multi-anvil apparatus up to 27 GPa and extended to higher pressure in the diamond-anvil cell with laser-heating. We have developed techniques to recover small heated samples by precision FIB milling and obtain high-resolution images of the laser-heated spot that show melting texture at high pressure. By analyzing the chemical compositions of the coexisting liquid and solid phases, we precisely determine the liquidus curve, providing necessary data to understand the inner core crystallization process.

The high-pressure and high-temperature experiments described here mimic planet interior differentiation processes. The processes are visualized and better understood by high-resolution 3D imaging and quantitative chemical analysis.

Simulación de la Planetary Interior Diferenciación Procesos en el Laboratorio

A planetary interior is under high-pressure and high-temperature conditions and it has a layered structure. There are two important processes that led to ...

Spatial Separation of Molecular Conformers and Clusters

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold molecular beams. However, these beams often contain multiple conformers and clusters, even at low rotational temperatures. We present an experimental methodology that allows the spatial separation of these constituent parts of a molecular beam expansion. Using an electric deflector the beam is separated by its mass-to-dipole moment ratio, analogous to a bender or an electric sector mass spectrometer spatially dispersing charged molecules on the basis of their mass-to-charge ratio. This deflector exploits the Stark effect in an inhomogeneous electric field and allows the separation of individual species of polar neutral molecules and clusters. It furthermore allows the selection of the coldest part of a molecular beam, as low-energy rotational quantum states generally experience the largest deflection. Different structural isomers (conformers) of a species can be separated due to the different arrangement of functional groups, which leads to distinct dipole moments. These are exploited by the electrostatic deflector for the production of a conformationally pure sample from a molecular beam. Similarly, specific cluster stoichiometries can be selected, as the mass and dipole moment of a given cluster depends on the degree of solvation around the parent molecule. This allows experiments on specific cluster sizes and structures, enabling the systematic study of solvation of neutral molecules.

We present a technique that allows the spatial separation of different conformers or clusters present in a molecular beam. An electrostatic deflector is used to separate species by their mass-to-dipole moment ratio, leading to the production of gas-phase ensembles of a single conformer or cluster stoichiometry.

Separación espacial de conformadores moleculares y cúmulos

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold ...

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical electrohydrodynamic liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields and polar dielectric liquids. The construction of basic apparatus and operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

La Preparación de electrohidrodinámicos Puentes de Polar dieléctricas Líquidos

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and ...

Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk. The primary advantage of AD is that the deposition takes place entirely at ambient temperature; thereby enabling film growth in material systems with disparate melting temperatures. This report describes in detail the processing steps for preparing the powder and for performing AD using the custom-built system. Representative characterization results are presented from scanning electron microscopy, profilometry, and ferromagnetic resonance for films grown in this system. As a representative overview of the capabilities of the system, focus is given to a sample produced following the described protocol and system setup. Results indicate that this system can successfully deposit 11 &#181;m thick yttrium iron garnet films that are &#160;&#62; 90% of the bulk density during a single 5 min deposition run. A discussion of methods to afford better control of the aerosol and particle selection for improved thickness and roughness variations in the film is provided.

This report describes the use of a custom-built system to perform aerosol deposition of thick films of yttrium iron garnet onto sapphire substrates at RT. The deposited films are characterized using scanning electron microscopy, profilometry, and ferromagnetic resonance to give a representative overview of the capabilities of the technique.

La formación de gruesas densos itrio Iron Garnet Films Usando Aerosol Deposición

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

Métodos experimentales para procesos de enfriamiento Elastocaloric Investigación de memoria de forma basada y validación del modelo

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Studying Dynamic Processes of Nano-sized Objects in Liquid using Scanning Transmission Electron Microscopy

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a microfluidic chamber assembled in the specimen holder for Transmission Electron Microscopy (TEM) and STEM. The microfluidic system consists of two silicon microchips supporting thin Silicon Nitride (SiN) membrane windows. This article describes the basic steps of sample loading and data acquisition. Most important of all is to ensure that the liquid compartment is correctly assembled, thus providing a thin liquid layer and a vacuum seal. This protocol also includes a number of tests necessary to perform during sample loading in order to ensure correct assembly. Once the sample is loaded in the electron microscope, the liquid thickness needs to be measured. Incorrect assembly may result in a too-thick liquid, while a too-thin liquid may indicate the absence of liquid, such as when a bubble is formed. Finally, the protocol explains how images are taken and how dynamic processes can be studied. A sample containing AuNPs is imaged both in pure water and in saline.

This protocol describes the operation of a liquid flow specimen holder for scanning transmission electron microscopy of AuNPs in water, as used for the observation of nanoscale dynamic processes.

El estudio de procesos dinámicos de nano-objetos de tamaño en el líquido de utilizar el escaneado Microscopía Electrónica de Transmisión

Samples fully embedded in liquid can be studied at a nanoscale spatial resolution with Scanning Transmission Electron Microscopy (STEM) using a ...

Wicking Tests for Unidirectional Fabrics: Measurements of Capillary Parameters to Evaluate Capillary Pressure in Liquid Composite Molding Processes

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify their influence on void formation in composite parts. Wicking in a fibrous medium described by the Washburn equation was considered equivalent to a flow under the effect of capillary pressure according to the Darcy law. Experimental tests for the characterization of wicking were conducted with both carbon and flax fiber reinforcement. Quasi-unidirectional fabrics were then tested by means of a tensiometer to determine the morphological and wetting parameters along the fiber direction. The procedure was shown to be promising when the morphology of the fabric is unchanged during capillary wicking. In the case of carbon fabrics, the capillary pressure can be calculated. Flax fibers are sensitive to moisture sorption and swell in water. This phenomenon has to be taken into account to assess the wetting parameters. In order to make fibers less sensitive to water sorption, a thermal treatment was carried out on flax reinforcements. This treatment enhances fiber morphological stability and prevents swelling in water. It was shown that treated fabrics have a linear wicking trend similar to those found in carbon fabrics, allowing for the determination of capillary pressure.

An experimental method to measure geometrical parameters and the apparent advancing contact angles describing capillary wicking in unidirectional synthetic and natural fabrics is proposed. These parameters are mandatory for the determination of the capillary pressures that must be taken into account for liquid composite molding (LCM) applications.

Las pruebas de mecha para unidireccionales Tejidos: Las mediciones de parámetros para evaluar capilar capilar de presión en los procesos de líquido compuesto de moldeo

During impregnation of a fibrous reinforcement in liquid composite molding (LCM) processes, capillary effects have to be understood in order to identify ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

Preparación de redes de cristal líquido para macroscópico movimiento oscilatoria inducida por luz

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

An Available Technique for Preparation of New Cast MnCuNiFeZnAl Alloy with Superior Damping Capacity and High Service Temperature

Manganese (Mn)-copper (Cu)-based alloys have been found to have&#160;damping capacity and can be used to reduce harmful vibrations and noise effectively. M2052 (Mn-20Cu-5Ni-2Fe, at%) is an important branch of Mn-Cu-based alloys, which possesses both excellent damping capacity and processability. In recent decades, lots of studies have been carried out on the performance optimization of M2052, improving the damping capacity, mechanical properties, corrosion resistance, and service temperature, etc. The major methods of performance optimization are alloying, heat treatment, pretreatment, and different ways of molding etc., among which alloying, as well as adopting a reasonable heat treatment, is the simplest and most effective method to obtain perfect and comprehensive performance. To obtain the M2052 alloy with excellent performance for casting molding, we propose to add Zn and Al to the MnCuNiFe alloy matrix and use a variety of heat treatment methods for a comparison in the microstructure, damping capacity, and service temperature. Thus, a new type of cast-aged Mn-22.68Cu-1.89Ni-1.99Fe-1.70Zn-6.16Al (at.%) alloy with&#160;superior damping capacity and high service temperature is obtained by an optimized heat treatment method. Compared with the forging technique, cast molding is simpler and more efficient, and the damping capacity of this as-cast alloy is excellent. Therefore, there is a suitable reason to think that it is a good choice for engineering applications.

Here we present a protocol to obtain a novel Mn-Cu-based alloy with excellent comprehensive performances by a high-quality smelting technology and reasonable heat treatment methods.

Una técnica disponible para la preparación de nuevas MnCuNiFeZnAl aleación fundido con Superior capacidad y alta temperatura de amortiguación

Manganese (Mn)-copper (Cu)-based alloys have been found to have&#160;damping capacity and can be used to reduce harmful vibrations and noise effectively. ...