Questo lavoro è stato supportato dall'Office of Naval Research (ONR N00014-15-1-0020) [Tkacik e Keanini] ed eseguito presso University of North Carolina a Motorsports Research Lab. lucidatura di Charlotte media è stato donato da Rosler.

<ol>
	<li>Berne, B. J., Pecora, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Dynamic Light Scattering. , (1976).</li><li>Boon, J. P., Yip, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular Hydrodynamics. , (1980).</li><li>Brown, J. C., Pusey, P. N., Goodwin, J. W., Ottewill, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+scattering+study+of+dynamic+and+time-averaged+correlations+in+dispersions+of+charged+particles.">Light scattering study of dynamic and time-averaged correlations in dispersions of charged particles.</a> J. Phys. A: Math Gen. 5 (8), 664-682 (1975).</li><li>Wainwright, T. E., Alder, B. J., Gass, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Decay+of+time+correlations+in+two+dimensions.">Decay of time correlations in two dimensions.</a> Phys. Rev. A. 4, 233-236 (1971).</li><li>Evans, D. J., Morriss, G. P. <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 of Nonequilibrium Liquids. , (2007).</li><li>Levesque, D., Verlet, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computer+"experiments"+on+classical+fluids,+III.+time-dependent+self+correlation+functions.">Computer "experiments" on classical fluids, III. time-dependent self correlation functions.</a> Phys. Rev. A. 2, 2514-2528 (1970).</li><li>Levesque, D., Ashurst, W. 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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Per poter utilizzare mucchi di grano vibrato come macroscopici analoghi per l'indagine molecolari processi idrodinamici, un sperimentalista deve, da un lato, imparare e utilizzare quattro misure di base e da altro, padroneggiare alcuni elementi di base dell'equilibrio e meccanica statistica di non equilibrio. In primo luogo concentrarsi su misure sperimentali, questi includono: i) misurazione della dinamica di grano individuale attraverso la misura della funzione di autocorrelazione di particella singola velocità, ii) m...

Idrodinamica molecolare studia la dinamica e la meccanica statistica delle singole molecole e collezioni di molecole all'interno dei fluidi. Tra le tante tecniche sperimentali sviluppate per lo studio di sistemi molecolari idrodinamica1,2, dispersione della luce1,2,3, simulazioni di dinamica molecolare4, 5,6,7 e, in misura minore, di scattering anelastico neutroni8 sono stati utilizzati più comunemente. Purtroppo, significative limitazioni collegare le due tecniche di quest'ultime. Simulazioni di dinamica molecolare (MD), ad esempio: i) sono limitata a piccole spaziale e temporale <img alt="Equation 1" src="/files/ftp_upload/56632/56632eq1.jpg"> domini contenenti relativamente poche molecole <img alt="Equation 2" src="/files/ftp_upload/56632/56632eq2.jpg"> </img>, ii) richiedono l'uso delle potenzialità di inter-particella approssimativa, iii) in genere introdurre periodiche condizioni al contorno, valide in condizioni di flusso di massa di non-equilibrio e iv) non possono, al momento, rispondere alla domanda fondamentale della dinamica come scala molecolare, che coinvolgono sia le singole molecole o collezioni di molecole, sono influenzate e coppie Torna a, massa, quantità di fluido non-equilibrio. La limitazione principale connessa con lo scattering di neutroni è legata alla difficoltà di accesso a numero limitato di sorgenti di neutroni fascio disponibile.
Al fine di fornire un contesto per la tecnica sperimentale analog presentata in questo articolo, evidenziamo tecniche di dispersione della luce applicate ai fluidi densi-gas e liquido-stato semplice. In un esperimento di scattering di luce tipica, un fascio di luce polarizzata laser è diretto ad un volume di interrogatorio piccola contenente un campione di fluido stazionario. Luce diffusa dalle molecole all'interno del campione viene quindi rilevato in qualche angolo fisso rispetto al fascio incidente. A seconda del regime di dinamico molecolare di interesse, rilevamento e analisi del segnale luce sparso incorpora né luce filtro o metodi di rilevamento di miscelazione. Come descritto da Berna e Pecora1, tecniche, di filtraggio che sonda dinamica molecolare allo stato fluido il tempo scale più corto <img alt="Equation 3" src="/files/ftp_upload/56632/56632eq3.jpg"> s, introdurre un interferometro post-scattering o un reticolo di diffrazione e consentire una scansione della densità spettrale di luce diffusa. Ottica mescolando tecniche, utilizzate per dinamica a scala di tempo lento, <img alt="Equation 4" src="/files/ftp_upload/56632/56632eq4.jpg"> s, al contrario, incorporare un analizzatore di autocorrelazione o spettro post-scattering, in cui il contenuto spettrale del segnale sparso viene estratto dalla luce sparsa misurata intensità.
In genere, laser sonde, almeno quelli che operano nella gamma visibile dello spettro, hanno lunghezze d'onda molto più tempo la caratteristica spaziatura tra molecole di liquido-stato. In queste circostanze, il fascio sonda eccita cinque collettivo, scala di tempo lento, modalità idrodinamico di lungo-lunghezza d'onda2,9,10 (lento rispetto la frequenza delle collisioni caratteristico): due viscously attenuato, contro-propagazione delle onde sonore, due modalità di vorticità disgiunto, puramente diffusivo e una modalità singola termica diffusiva (entropia). La modalità di suono sono eccitati in direzione (longitudinale) del fascio incidente, mentre la modalità vorticoso sono eccitati in direzione trasversale.
Considerando puramente sperimentale spargendo tecniche, due domande fondamentali, che si trova al centro dell'equilibrio e meccanica statistica di non-equilibrio di molecolare, sistemi liquido-stato, rimangono di là di luce e misure di scattering di neutroni: 1) rigorosi argomenti9,11 mostrano che la dinamica di collisione - e sub-collision-scala tempo casuale, delle singole molecole di liquido-stato, soggetto a dinamica newtoniana classica o dinamica quantistica, possa essere rielaborata nella forma di equazioni generalizzate di Langevin (GLE). GLE, a loro volta, costituiscono uno strumento teorico centrale nello studio della meccanica statistica di non-equilibrio delle molecole nel denso gas e liquidi. Purtroppo, poiché le dinamiche delle singole molecole (macromolecolare) non possono essere risolto da una delle due tecniche di scattering, non c'è attualmente nessun modo diretto, di là di simulazioni MD, per testare la validità di GLE. 2) un'ipotesi fondamentali che si trova nel cuore della fluidodinamica di continuum macroscopica, anche su microscala molecolare idrodinamica, postula che su - e tempo-scale di lunghezza grande rispetto diametri molecolari e collisione volte, ma piccolo rispetto al continuum scale di lunghezza e tempo, equilibrio termodinamico locale (LTE) prevale. In flusso e calore modelli trasferimento continui, come le equazioni di Navier-Stokes (NS), il presupposto di LTE è richiesto9 per accoppiarsi intrinsecamente non-equilibrio, flusso di continuum-scala e funzionalità di trasporto di energia — piace viscosi sollecitazioni di taglio e conduzione termica — rigorosamente equilibrio termodinamico proprietà, come temperatura ed energia interna. Allo stesso modo, mentre su microscala slancio ed energia trasporti sono processi intrinsecamente non-equilibrio, che riflette l'apparenza della massa accoppiati, di Microscala, slancio e correnti d'energia, modelli di questi processi di Microscala supporre che le correnti rappresentano piccole perturbazioni da LTE9. Ancora una volta, al meglio della nostra conoscenza, non ci sono stati nessun test sperimentali diretti dell'assunzione LTE. In particolare, sembra che non sono stati tentati esperimenti di dispersione idrodinamica molecolare all'interno di flussi di fluidi densi, commoventi e di non-equilibrio.
In questo articolo, descriviamo una tecnica sperimentale analogica in cui la particella macroscopica, singola e collettivo delle particelle dinamiche dei mucchi di grano vibrato, misurate utilizzando standard Particle Imaging Velocimetry (PIV), può essere utilizzato per predire indirettamente, interpretare ed esporre single - e multi - molecule idrodinamica in denso gas e liquidi. Gli elementi fisici e teorici che consentono la tecnica proposta sono indicati in un recente documento pubblicato dal nostro gruppo di12. Sperimentalmente, il sistema macroscopico deve esibire: (i) una tendenza sostenuta verso locale, equilibrio meccanico statistico di macroscala e (ii) piccolo, partenze lineare dall'equilibrio che imitano le fluttuazioni di non-equilibrio (debole) osservati in sistemi molecolari idrodinamici. Teoricamente: microscale (i) classici modelli che descrivono l'equilibrio e la meccanica statistica debolmente-non-equilibrio di denso, sistemi di N particelle interagenti devono essere rielaborati in forma di macroscala, e (ii) i modelli di macroscala risultanti devono in modo affidabile prevedere la dinamica di particella singola e multipla, da breve, particella-collisione-scale temporali a lunghe, continuum-flusso-tempo-scale.
Qui, presentiamo un dettagliato protocollo sperimentale, nonché rappresentante risultati ottenuti con la nuova tecnica. In contrasto con simulazioni MD e luce e metodi di scattering di neutroni, la nuova tecnica consente, per la prima volta, studio dettagliato dei processi molecolari idrodinamici all'interno che scorre, fortemente non-equilibrio, densa di gas e liquidi.

<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

È descritto un metodo analogico, macroscopico per lo studio su scala molecolare processi idrodinamici in denso gas e liquidi. La tecnica si applica un standard fluido dinamico diagnostica, particella image velocimetry (PIV), per misurare: i) le velocità delle singole particelle (grani), ancora esistenti sul breve, grano-collisione scale temporali, ii) le velocità dei sistemi di particelle, sia a breve collisione-tempo - e lungo, continuum-flusso-tempo-bilance, iii) modi collettivi idrodinamici, conosciute per esistere in fluidi densi molecolare e iv) funzioni di autocorrelazione di velocità e lungo-tempo-scala corta, centrale per comprendere le dinamiche delle particelle-scala in sistemi fluidi fortemente interagenti, densi. Il sistema base è composto di un sistema di imaging, fonte di luce, sensori vibrazionali, sistema vibrazionale con un noto software di media e PIV e analisi. Necessarie misure sperimentali e un contorno degli strumenti teorici necessari quando si utilizza la tecnica analogica per studiare processi idrodinamici su scala molecolare sono evidenziati. La tecnica proposta fornisce un'alternativa relativamente semplice a fotonici e metodi di dispersione tradizionalmente utilizzati in studi idrodinamici molecolari del fascio di neutroni.

Nel presentare i risultati rappresentativi, ci riferiamo ai processi di continuum-tempo-scala come quelli osservati e previsti su scale temporali, <img alt="Equation 25" src="/files/ftp_upload/56632/56632eq25.jpg"> che sono lunghi rispetto alla scala di tempo di collisione caratteristica grana, <img alt="Equation 26" src="/files/ftp_upload/56632/56632eq26.jpg"> <img alt="Equation 27" src="/files/ftp_upload/56632/56632eq27.jpg"> e particella-tempo-scala processi come que...

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

Viene presentato un metodo analogico sperimentalmente accessibile per lo studio di processi molecolari idrodinamici in fluidi densi. La tecnica utilizza particle image velocimetry dei mucchi di grano vibrato, alta-restituzione e permette l'osservazione diretta, macroscopici di processi dinamici noto e previsto di esistere in fortemente interagenti, ad alta densità gas e liquidi.

Una tecnica Analog macroscopica per studiare i processi molecolari idrodinamici in denso gas e liquidi

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 Views.  University of North Carolina at Charlotte. Viene presentato un metodo analogico sperimentalmente accessibile per lo studio di processi molecolari idrodinamici in fluidi densi. La tecnica utilizza particle image velocimetry dei mucchi di grano vibrato, alta-restituzione e permette l'osservazione diretta, macroscopici di processi dinamici noto e previsto di esistere in fortemente interagenti, ad alta densità gas e liquidi.

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.

Rivelare processi dinamici dei materiali in liquidi con liquido di trasmissione microscopia elettronica cellulare

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.

Simulazione del Planetary Interior differenziazione processi in 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.

Separazione spaziale di conformatori molecolari e cluster

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 preparazione di Electrohydrodynamic Ponti da Polar dielettrici liquidi

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 formazione di spesse Dense ittrio ferro Garnet Films Utilizzando Aerosol Deposizione

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.

Metodi sperimentali per le indagini di memoria di forma a base processi di raffreddamento Elastocaloric e validazione del modello

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.

Lo studio dei processi dinamici di dimensioni nano oggetti in liquidi di utilizzare la scansione microscopia elettronica a trasmissione

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.

Wicking Test per unidirezionali Tessuti: Misure di capillare parametri per valutare capillare pressione nei Processi Liquid Composite Molding

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.

Preparazione delle reti di cristalli liquidi per moto oscillatorio macroscopica indotta da luce

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 tecnica disponibile per la preparazione del nuovo Cast MnCuNiFeZnAl lega con Superior servizio capacità e ad alta temperatura di smorzamento

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. ...