Journal articles: 'Electric field gradient focusing'

1

Kelly, Ryan T., and Adam T. Woolley. "Electric field gradient focusing." Journal of Separation Science 28, no. 15 (October 2005): 1985–93. http://dx.doi.org/10.1002/jssc.200500228.

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Sun, Xuefei, Dan Li, Adam T. Woolley, Paul B. Farnsworth, H. Dennis Tolley, Karl F. Warnick, and Milton L. Lee. "Bilinear electric field gradient focusing." Journal of Chromatography A 1216, no. 37 (September 2009): 6532–38. http://dx.doi.org/10.1016/j.chroma.2009.07.050.

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Sun, Xuefei, Paul B. Farnsworth, H. Dennis Tolley, Karl F. Warnick, Adam T. Woolley, and Milton L. Lee. "Performance optimization in electric field gradient focusing." Journal of Chromatography A 1216, no. 1 (January 2009): 159–64. http://dx.doi.org/10.1016/j.chroma.2008.11.031.

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Koegler, Wendy S., and Cornelius F. Ivory. "Focusing proteins in an electric field gradient." Journal of Chromatography A 726, no. 1-2 (March 1996): 229–36. http://dx.doi.org/10.1016/0021-9673(95)01069-6.

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Anand, Robbyn K., Eoin Sheridan, Dzmitry Hlushkou, Ulrich Tallarek, and Richard M. Crooks. "Bipolar electrode focusing: tuning the electric field gradient." Lab Chip 11, no. 3 (2011): 518–27. http://dx.doi.org/10.1039/c0lc00351d.

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Petsev, Dimiter N., Gabriel P. Lopez, Cornelius F. Ivory, and Scott S. Sibbett. "Microchannel protein separation by electric field gradient focusing." Lab on a Chip 5, no. 6 (2005): 587. http://dx.doi.org/10.1039/b501538c.

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Humble, Paul H., John N. Harb, H. Dennis Tolley, Adam T. Woolley, Paul B. Farnsworth, and Milton L. Lee. "Influence of transport properties in electric field gradient focusing." Journal of Chromatography A 1160, no. 1-2 (August 2007): 311–19. http://dx.doi.org/10.1016/j.chroma.2007.04.013.

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Sun, Xuefei, Paul B. Farnsworth, Adam T. Woolley, H. Dennis Tolley, Karl F. Warnick, and Milton L. Lee. "Poly(ethylene glycol)-Functionalized Devices for Electric Field Gradient Focusing." Analytical Chemistry 80, no. 2 (January 2008): 451–60. http://dx.doi.org/10.1021/ac0713104.

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Hlushkou, Dzmitry, Robbyn K. Perdue, Rahul Dhopeshwarkar, Richard M. Crooks, and Ulrich Tallarek. "Electric field gradient focusing in microchannels with embedded bipolar electrode." Lab on a Chip 9, no. 13 (2009): 1903. http://dx.doi.org/10.1039/b822404h.

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Lin, Shu-Ling, Yuanyuan Li, Adam T. Woolley, Milton L. Lee, H. Dennis Tolley, and Karl F. Warnick. "Programed elution and peak profiles in electric field gradient focusing." ELECTROPHORESIS 29, no. 5 (March 2008): 1058–66. http://dx.doi.org/10.1002/elps.200700652.

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Trickett, Christopher A., Rowan D. Henderson, Rosanne M. Guijt, and Michael C. Breadmore. "Electric field gradient focusing using a variable width polyaniline electrode." ELECTROPHORESIS 33, no. 21 (October 2, 2012): 3254–58. http://dx.doi.org/10.1002/elps.201200335.

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12

Liu, Jikun, Xuefei Sun, Paul B. Farnsworth, and Milton L. Lee. "Fabrication of Conductive Membrane in a Polymeric Electric Field Gradient Focusing Microdevice." Analytical Chemistry 78, no. 13 (July 2006): 4654–62. http://dx.doi.org/10.1021/ac060204j.

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13

Huber, David E., and Juan G. Santiago. "Ballistic dispersion in temperature gradient focusing." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 464, no. 2091 (December 18, 2007): 595–612. http://dx.doi.org/10.1098/rspa.2007.0161.

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Molecular dispersion is caused by both molecular diffusion and non-uniform bulk fluid motion. While the Taylor–Aris dispersion regime is the most familiar regime in microfluidic systems, an oft-overlooked regime is that of purely kinematic (or ballistic) dispersion. In most microfluidic systems, this dispersion regime is transient and quickly gives way to Taylor–Aris dispersion. In electrophoretic focusing methods such as temperature gradient focusing (TGF), however, the characteristic time scales for dispersion are fixed, and focused peaks may never reach the Taylor limit. In this situation, generalized Taylor dispersion analysis is not applicable. A heuristic model is developed here which accounts for both molecular diffusion and advective dispersion across all dispersion regimes, from pure diffusion to Taylor dispersion to pure advection. This model is compared to results from TGF experiments and accurately captures both the initial decrease and subsequent increase in peak widths as electric field strength increases. The results of this combined analytical and experimental study provide a useful tool for estimation of dispersion and optimization of TGF systems.

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Humble, Paul H., Ryan T. Kelly, Adam T. Woolley, H. Dennis Tolley, and Milton L. Lee. "Electric Field Gradient Focusing of Proteins Based on Shaped Ionically Conductive Acrylic Polymer." Analytical Chemistry 76, no. 19 (October 2004): 5641–48. http://dx.doi.org/10.1021/ac040055+.

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15

Quist, Jos, Paul Vulto, and Thomas Hankemeier. "Isotachophoretic Phenomena in Electric Field Gradient Focusing: Perspectives for Sample Preparation and Bioassays." Analytical Chemistry 86, no. 9 (April 16, 2014): 4078–87. http://dx.doi.org/10.1021/ac403764e.

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Lin, Shu-Ling, Yuanyuan Li, H. Dennis Tolley, Paul H. Humble, and Milton L. Lee. "Tandem electric field gradient focusing system for isolation and concentration of target proteins." Journal of Chromatography A 1125, no. 2 (September 2006): 254–62. http://dx.doi.org/10.1016/j.chroma.2006.05.041.

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17

Huang, Bing-Yau, Shuan-Yu Huang, Chia-Hsien Chuang, and Chie-Tong Kuo. "Electrically-Tunable Blue Phase Liquid Crystal Microlens Array Based on a Photoconductive Film." Polymers 12, no. 1 (January 2, 2020): 65. http://dx.doi.org/10.3390/polym12010065.

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This paper proposes an effective approach to fabricate a blue phase liquid crystal (BPLC) microlens array based on a photoconductive film. Owing to the characteristics of photo-induced conducting polymer polyvinylcarbazole (PVK), in which conductivity depends on the irradiation of UV light, a progressive mask resulting in the variation of conductivity is adopted to produce the gradient distribution of the electric field. The reorientations of liquid crystals according to the gradient distribution of the electric field induce the variation of the refractive index. Thus, the incident light experiences the gradient distribution of the refractive index and results in the focusing phenomenon. The study investigates the dependence of lens performance on UV exposure time, the focal length of the lens, and focusing intensities with various incident polarizations. The BPLC microlens array exhibits advantages such as electrically tunability, polarization independence, and fast response time.

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Lin, S. L., H. D. Tolley, and M. L. Lee. "Voltage-Controlled Electric Field Gradient Focusing with Online UV Detection for Analysis of Proteins." Chromatographia 62, no. 5-6 (August 29, 2005): 277–81. http://dx.doi.org/10.1365/s10337-005-0615-7.

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Cong, Yongzheng, Yu Liang, Lihua Zhang, Weibing Zhang, and Yukui Zhang. "Improved protein separation by microchip isoelectric focusing with stepwise gradient of electric field strength." Journal of Separation Science 32, no. 3 (February 2009): 462–65. http://dx.doi.org/10.1002/jssc.200800514.

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20

Janča, Josef, and Natalia Gospodinova. "Isoperichoric Focusing Phenomena Generated by Coupled Electric and Gravitational Field Forces in Bidisperse Mixtures of Colloidal Particles." Collection of Czechoslovak Chemical Communications 63, no. 2 (1998): 155–63. http://dx.doi.org/10.1135/cccc19980155.

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The first successful isopycnic focusing generated by the coupled electric and gravitational fields applied to the model bidisperse mixtures of the colloidal silica and polyaniline particles of low size ratio is described. The theoretical analysis and the experimental results show that the density gradient forming liquid should not necessarily behave as a continuum regarding the focused species. This finding confirms the original prediction which was evidenced previously by the focusing under the action of high intensity centrifugal field forces only.

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Burke, Jeffrey M., Zheng Huang, and Cornelius F. Ivory. "Simultaneous Separation of Negatively and Positively Charged Species in Dynamic Field Gradient Focusing Using a Dual Polarity Electric Field." Analytical Chemistry 81, no. 19 (October 2009): 8236–43. http://dx.doi.org/10.1021/ac901634y.

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Malik, M. Rizwan, Tie Lin Shi, and Zi Rong Tang. "Trapping and Manipulation of Bioparticles by a 3-D Optimal Multiple-Designed Offset Carbon-Microelectrode Array in C-MEMS Fabrication." Journal of Biomimetics, Biomaterials and Tissue Engineering 10 (May 2011): 25–42. http://dx.doi.org/10.4028/www.scientific.net/jbbte.10.25.

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A dielectrophoretic approach with latest developed three-dimensional (3-D) carbon micro-electro-mechanical system (C-MEMS) has been extended as a potential route with idyllic solution to recommend a low-cost, biocompatible and high throughput manipulation and positioning for bio-particles as compared to 2D-planar microelectrodes. Presented in this paper is a novel platform for modelling and simulation of C-MEMS microfabrication process for dielectrophoresis (DEP) force based on various 3-D offset-microelectrode configurations. Numerical solutions are employed to investigate the upshots of multi-designed microelectrodes, applied voltage, electrode edge-to-edge gap and geometric size of microelectrodes on the electric field intensity gradient, induced by an AC voltage for the deployment of broad categories of bioparticles creation, utilization and their manipulation (separation, concentration, transportation and focusing). Sharp edge electrodes are the principle focus of this paper for DEP manipulation that is more convenient to enhance the electric field intensity distribution. The results show that square column electrodes configuration comparatively create large gradient magnitude in electric field intensity as compared to all other configurations. It is also observed that electric field extends drastically with increases in microelectrode height. These findings are consistent with literature experimental reports and will provide vital strategy for optimal design of DEP devices with 3-D C-MEMS.

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Davies, Collin D., and Richard M. Crooks. "Focusing, sorting, and separating microplastics by serial faradaic ion concentration polarization." Chemical Science 11, no. 21 (2020): 5547–58. http://dx.doi.org/10.1039/d0sc01931c.

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Weng, Zi Hua. "Gradient Force of Electromagnetic Strength to Drive Precisely the Small Mass." Key Engineering Materials 656-657 (July 2015): 670–75. http://dx.doi.org/10.4028/www.scientific.net/kem.656-657.670.

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J. C. Maxwell applied the quaternion analysis and vector terminology to study the physics properties of electromagnetic field. Nowadays the spaces of electromagnetic and gravitational fields can be chosen as the quaternion spaces, while their coordinates are able to be the complex numbers. The complex quaternion space can be used to describe the physics feature of forces in the electromagnetic and gravitational fields. The paper is capable of writing the terms of force into a single definition, including the inertial force, gravity, electromagnetic force, energy gradient and so on. Further the definition of force can deduce some new but weak terms of force. One of them is the ‘strength gradient force’. The strength gradient force relates only with the gradient and distribution of field strength, and is independent to the electric charge and mass. And this force is able to exert the interaction on neutral and charged particles. As the driving force, the strength gradient force can be used to drive precisely the motion of small mass, and applied to operate the precision machine. By analogy with the optical tweezers and magnetic mirror, the strength gradient force is possible to be applied to devices in the future, including in the precision machine for the focusing, the collimating of the polarization maintaining optical fibers and so forth.

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25

Ramachandran, Ashwin, Diego A. Huyke, Eesha Sharma, Malaya K. Sahoo, ChunHong Huang, Niaz Banaei, Benjamin A. Pinsky, and Juan G. Santiago. "Electric field-driven microfluidics for rapid CRISPR-based diagnostics and its application to detection of SARS-CoV-2." Proceedings of the National Academy of Sciences 117, no. 47 (November 4, 2020): 29518–25. http://dx.doi.org/10.1073/pnas.2010254117.

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The rapid spread of COVID-19 across the world has revealed major gaps in our ability to respond to new virulent pathogens. Rapid, accurate, and easily configurable molecular diagnostic tests are imperative to prevent global spread of new diseases. CRISPR-based diagnostic approaches are proving to be useful as field-deployable solutions. In one basic form of this assay, the CRISPR–Cas12 enzyme complexes with a synthetic guide RNA (gRNA). This complex becomes activated only when it specifically binds to target DNA and cleaves it. The activated complex thereafter nonspecifically cleaves single-stranded DNA reporter probes labeled with a fluorophore−quencher pair. We discovered that electric field gradients can be used to control and accelerate this CRISPR assay by cofocusing Cas12–gRNA, reporters, and target within a microfluidic chip. We achieve an appropriate electric field gradient using a selective ionic focusing technique known as isotachophoresis (ITP) implemented on a microfluidic chip. Unlike previous CRISPR diagnostic assays, we also use ITP for automated purification of target RNA from raw nasopharyngeal swab samples. We here combine this ITP purification with loop-mediated isothermal amplification and the ITP-enhanced CRISPR assay to achieve detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA (from raw sample to result) in about 35 min for both contrived and clinical nasopharyngeal swab samples. This electric field control enables an alternate modality for a suite of microfluidic CRISPR-based diagnostic assays.

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Tsori, Yoav, and Ludwik Leibler. "Phase-separation in ion-containing mixtures in electric fields: Fig. 1." Proceedings of the National Academy of Sciences 104, no. 18 (April 18, 2007): 7348–50. http://dx.doi.org/10.1073/pnas.0607746104.

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When a liquid mixture is subjected to external electric fields, ionic screening leads to field gradients. We point out that, if the mixture is initially in the homogeneous phase, this screening can bring about a robust phase-separation transition with two main features: (i) the phase separation is expected to occur in any electrode geometry, and (ii) the voltage required is typically of the order of 1 V and even less. We discuss several applications of the effect relevant to the field of microfluidics, focusing on the creation of a nanometer-scale lubrication layer in the phase separation process and the modification of the slip length.

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GILSON, ERIK P., RONALD C. DAVIDSON, PHILIP C. EFTHIMION, RICHARD MAJESKI, and HONG QIN. "The Paul Trap Simulator Experiment." Laser and Particle Beams 21, no. 4 (October 2003): 549–52. http://dx.doi.org/10.1017/s0263034603214129.

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The assembly of the Paul Trap Simulator Experiment (PTSX) is now complete and experimental operations have begun. The purpose of PTSX, a compact laboratory facility, is to simulate the nonlinear dynamics of intense charged particle beam propagation over a large distance through an alternating-gradient transport system. The simulation is possible because the quadrupole electric fields of the cylindrical Paul trap exert radial forces on the charged particles that are analogous to the radial forces that a periodic focusing quadrupole magnetic field exert on the beam particles in the beam frame. By controlling the waveform applied to the walls of the trap, PTSX will explore physics issues such as beam mismatch, envelope instabilities, halo particle production, compression techniques, collective wave excitations, and beam profile effects.

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SOUNART, T. L., and J. C. BAYGENTS. "Lubrication theory for electro-osmotic flow in a non-uniform electrolyte." Journal of Fluid Mechanics 576 (March 28, 2007): 139–72. http://dx.doi.org/10.1017/s0022112006003867.

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A lubrication theory has been developed for the electro-osmotic flow of non-uniform buffers in narrow rectilinear channels. The analysis applies to systems in which the transverse dimensions of the channel are large compared with the Debye screening length of the electrolyte. In contrast with related theories of electrokinetic lubrication, here the streamwise variations of the velocity field stem from, and are nonlinearly coupled to, spatiotemporal variations in the electrolyte composition. Spatially non-uniform buffers are commonly employed in electrophoretic separation and transport schemes, including iso-electric focusing (IEF), isotachophoresis (ITP), field-amplified sample stacking (FASS), and high-ionic-strength electro-osmotic pumping. The fluid dynamics of these systems is controlled by a complex nonlinear coupling to the ion transport, driven by an applied electric field. Electrical conductivity gradients, attendent to the buffer non-uniformities, result in a variable electro-osmotic slip velocity and, in electric fields approaching 1 kV cm−1, Maxwell stresses drive the electrohydrodynamic circulation. Explicit semi-analytic expressions are derived for the fluid velocity, stream function, and electric field. The resulting approximations are found to be in good agreement with full numerical solutions for a prototype buffer, over a range of conditions typical of microfluidic systems. The approximations greatly simplify the computational analysis, reduce computation times by a factor 4–5, and, for the first time, provide general insight on the dominant fluid physics of two-dimensional electrically driven transport.

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Kelly, Ryan T., Yi Li, and Adam T. Woolley. "Phase-Changing Sacrificial Materials for Interfacing Microfluidics with Ion-Permeable Membranes To Create On-Chip Preconcentrators and Electric Field Gradient Focusing Microchips." Analytical Chemistry 78, no. 8 (April 2006): 2565–70. http://dx.doi.org/10.1021/ac0521394.

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Nalimov, A. G. "Energy flux of a vortex field focused using a secant gradient lens." Computer Optics 44, no. 5 (October 2020): 707–11. http://dx.doi.org/10.18287/2412-6179-co-688.

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In this paper we simulated the focusing of left circular polarized beam with a second order phase vortex and a second-order cylindrical vector beam by a gradient index Mikaelian lens. It was shown numerically, that there is an area with a negative Poynting vector projection on Z axis, that can be called an area with backward energy flow. Using a cylindrical hole in the output surface of the lens and optimizing it one can obtain a negative flow, which will be situated in the maximum intensity region, unlike to previous papers, in which such backward energy flow regions were situated in a shadow area. Thereby, this lens will work as an “optical magnet”, it will attract Rayleigh particles (with diameter about 1/20 of the wavelength) to its surface.

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31

Williams, R. L., C. E. Clayton, C. Joshi, T. Katsouleas, and W. B. Mori. "Studies of relativistic wave–particle interactions in plasma-based collective accelerators." Laser and Particle Beams 8, no. 3 (September 1990): 427–49. http://dx.doi.org/10.1017/s0263034600008673.

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The interaction of externally injected charged particles (electrons) with plasma waves moving with a phase velocity that is very close to the speed of light is examined. Such plasma waves form the basis of at least three collective accelerator schemes: the plasma beat wave accelerator (PBWA), the plasma wake-field accelerator (PWFA), and the laser wake-field accelerator (LWFA). First, the electron trapping threshold, energy gain and acceleration length are examined using a 1-D model. This model elucidates how the final energies of the injected test electrons depend upon their injection and extraction phases and phase slippage. Phase energy diagrams are shown to be extremely useful in visualizing wave-particle interactions in 1-D. Second, we examine, using a two-dimensional model, the effects of radial electric fields on focusing or defocusing the injected particles depending upon their radial positions and phases in the relativistically moving potential well. Finally, we extend the model to 3-D so that the effect of injected particles' emittance on the acceleration process may be determined. This simple 3-D model will be extremely useful in predicting the electron energy spectra of several current experiments designed to demonstrate ultrahigh gradient acceleration of externally injected test particles by relativistic plasma waves.

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Wang, Guangxin, Huantong Xie, Shulian Hou, Wei Chen, and Xiuhong Yang. "Development of High-Field Permanent Magnetic Circuits for NMRI/MRI and Imaging on Mice." BioMed Research International 2016 (2016): 1–11. http://dx.doi.org/10.1155/2016/8659298.

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The high-field permanent magnetic circuits of 1.2 T and 1.5 T with novel magnetic focusing and curved-surface correction are developed. The permanent magnetic circuit comprises a magnetic yoke, main magnetic steel, nonspherical curved-surface magnetic poles, plugging magnetic steel, and side magnetic steel. In this work, a novel shimming method is proposed for the effective correction of base magnetic field (B0) inhomogeneities, which is based on passive shimming on the telescope aspheric cutting, grinding, and fine processing technology of the nonspherical curved-surface magnetic poles and active shimming adding higher-order gradient coils. Meanwhile, the magnetic resonance imaging dedicated alloy with high-saturation magnetic field induction intensity and high electrical resistivity is developed, and nonspherical curved-surface magnetic poles which are made of the dedicated alloy have very good anti-eddy-current effect. In addition, the large temperature coefficient problem of permanent magnet can be effectively controlled by using a high quality temperature controller and deuterium external locking technique. Combining our patents such as gradient coil, RF coil, and integration computer software, two kinds of small animal Micro-MRI instruments are developed, by which the high quality MRI images of mice were obtained.

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Xiao, J. H., Y. C. Du, S. Z. Zhang, and Y. T. Zhao. "Ultrafast High-Energy Electron Radiography Application in Magnetic Field Delicate Structure Measurement." Laser and Particle Beams 2021 (January 19, 2021): 1–9. http://dx.doi.org/10.1155/2021/6683245.

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Transient electromagnetic field plays very important roles in the evolution of high-energy-density matter or laser plasma. Now, a new design is proposed in this paper to diagnose the transient magnetic field, using relativistic electron bunch as a probe based on high-energy electron radiography. And based on this scheme, the continuous distribution of magnetic strength field can be snapshotted. For 1 mm thick quadrupole magnet model measured by 50 MeV probe electron beams, the simulation result indicates that this diagnosis has spatial resolution better than 4 microns and high measurement accuracy for strong magnetic strength and high magnetic gradient field no matter whether the magnetic interaction is focusing or defocusing for the range from -510 T ∗ μm to 510 T ∗ μm.

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Thakur, Vishal, and Niti Kant. "Exponential density transition-based enhanced second harmonic generation in plasma." Laser and Particle Beams 36, no. 3 (September 2018): 363–68. http://dx.doi.org/10.1017/s0263034618000393.

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AbstractEnhanced harmonic generation of second order based on exponential density ramp in plasma has been noticed. It is well known that self-focusing of pump laser induces a transverse intensity gradient, which gives rise to the plasma wave at the pump frequency. Highly intense Gaussian laser with exponential density ramp profile generates a second harmonic pulse in plasma. It is noticed that the amplitude of second-harmonic pulse varies periodically with the distance and reaches its peak value in the focal region. Further, it is found that exponential plasma density ramp is useful for stronger self-focusing, which lead to rise second harmonic generation (SHG). Wiggler magnetic field provides the additional angular momentum required for second harmonic photon and aids in growing of resonant process. One may clearly see that exponential plasma density ramp imparts a major role in enhancing the SHG in plasma. Further, the combined effect of exponential density ramp and wiggler magnetic field boosts the SHG in plasma.

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Makarevich, R. A., and W. A. Bristow. "Coordinated radar observations of plasma wave characteristics in the auroral F region." Annales Geophysicae 32, no. 7 (July 29, 2014): 875–88. http://dx.doi.org/10.5194/angeo-32-875-2014.

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Abstract. Properties of decameter-scale plasma waves in the auroral F region are investigated using coordinated observations of plasma wave characteristics with the Kodiak HF coherent radar (KOD) and Poker Flat Incoherent Scatter Radar (PFISR) systems in the Alaskan sector. We analyze one event on 14 November 2012 that occurred during the first PFISR Ion-Neutral Observations in the Thermosphere (PINOT) campaign when exceptionally good F region backscatter data at 1 s resolution were collected by KOD over the wide range of locations also monitored by PFISR. In particular, both radar systems were observing continuously along the same magnetic meridian, which allowed for a detailed comparison between the line-of-sight (l-o-s) velocity data sets. It is shown that l-o-s velocity correlation for data points strictly matched in time (within 1 s) depends strongly on the number of ionospheric echoes detected by KOD in a given post-integration interval or, equivalently, on the KOD echo occurrence in that interval. The l-o-s velocity correlations reach 0.7–0.9 for echo occurrences exceeding 70%, while also showing considerable correlations of 0.5–0.6 for occurrences as low as 10%. Using the same approach of strictly matching the KOD and PFISR data points, factors controlling coherent echo power are investigated, focusing on the electric field and electron density dependencies. It is demonstrated that the signal-to-noise ratio (SNR) of F region echoes increases nearly monotonically with an increasing electric field strength as well as with an increasing electron density, except at large density values, where SNR drops significantly. The electric field control can be understood in terms of the growth rate of the gradient-drift waves being proportional to the convection drift speed under conditions of fast-changing convection flows, while the density effect may involve over-refraction at large density values and radar backscatter power proportionality to the perturbation density.

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Chen, Jin, Yang Yang Zhou, Hong Chen Chu, Yun Lai, Huan Yang Chen, Mingji Chen, and Daining Fang. "Highly Efficient Gradient Solid Immersion Lens with Large Numerical Aperture for Broadband Achromatic Deep Subwavelength Focusing and Magnified Far Field." Advanced Optical Materials 9, no. 17 (June 18, 2021): 2100509. http://dx.doi.org/10.1002/adom.202100509.

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Sokolovsky, S. A., A. I. Sokolovsky, and O. A. Hrinishyn. "Hydrodynamic states of electron plasma of semiconductors in the generalized Chapman–Enskog method." Journal of Physics and Electronics 28, no. 1 (September 10, 2020): 9–16. http://dx.doi.org/10.15421/332002.

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The hydrodynamic states of polar semiconductors are investigated. Such states are described by the temperature, mass velocity, and density of the number of particles of the electron subsystem, which is considered as rarefied one. The phonon subsystem of a semiconductor is considered to be equilibrium. The electron-phonon interaction in the system is described by the Fröhlich Hamiltonian. The theory is based on Bogolyubov’s linear kinetic equation for the electron distribution function in the presence of a weak electric field. The reduced description of the system is investigated by the generalized Chapman–Enskog method, which leads to a nonlinear equation for the electron distribution function in the reduced description. The zone structure of the system is neglected, focusing on the study of fundamental issues of relaxation of temperature and velocity. Gradients of hydrodynamic parameters are considered small; the same smallparameters determine the smallness of the electric field. In the basic order of the perturbation theory, the distribution function of the system satisfies a nonlinear equation. The method of spectral theory of the collision integral operator shows that the study of the basic approximation is reduced to an analysis of a first-order quasilinear equation, which, in particular, has a solution that we found earlier.

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Kotlyar, V. V., S. S. Stafeev, A. G. Nalimov, and A. A. Kovalev. "Formation of the reverse flow of energy in a sharp focus." Computer Optics 43, no. 5 (October 2019): 714–22. http://dx.doi.org/10.18287/2412-6179-2019-43-5-714-722.

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It was theoretically shown that in the interference pattern of four plane waves with specially selected directions of linear polarization it is formed a reverse flow of energy. The areas of direct and reverse flow alternate in a staggered order in the cross section of the interference pattern. The absolute value of the reverse flow directly depends on the angle of convergence of the plane waves (on the angle between the wave vector and the optical axis) and reach the maximum at an angle of convergence close to 90 degrees. The right-handed triples of the vectors of four plane waves (the wave vector with positive values of projection to optical axis and the vector of electric and magnetic fields) when added in certain areas of the interference pattern form an electromagnetic field described by the left-handed triple of vectors; however, the projection of wave vector to optical axis has negative values. In these areas, the light propagates in the opposite direction. A similar explanation of the mechanism of the formation of a reverse flow can be applied to the case of a sharp focusing of a laser beam with a second-order polarization singularity. It is also shown that if a spherical dielectric Rayleigh nanoparticle is placed in the backflow region, then a force directed in the opposite direction will act on it (the scattering force will be more than the gradient force).

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Sadaba, I., Colin H. J. Fox, and Stewart McWilliam. "An Investigation of Residual Stress Effects due to the Anodic Bonding of Glass and Silicon in MEMS Fabrication." Applied Mechanics and Materials 5-6 (October 2006): 501–8. http://dx.doi.org/10.4028/www.scientific.net/amm.5-6.501.

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Anodic bonding is widely-used in the fabrication of Micro-Electro-Mechanical Systems (MEMS) devices to join silicon and glass components. The process involves the application of temperature, moderate pressure and an electric field. This paper investigates residual stresses arising during anodic bonding, focusing on the resulting induced distortions. Components of a MEMS silicon rate sensor, in which a silicon wafer is anodically bonded to Pyrex™ glass, were used as the vehicle for the investigation. Distortions generated by the anodic bonding process when using two different electrode configurations (point and planar) were measured using a surface optical profiler. These showed a particular pattern across the wafers for both configurations. An efficient FEM study was carried out to model the qualitative effect of the following residual stress sources; thermal stress, glass shrinkage due to structural relaxation and compositional gradients due to ion migration. Importantly, the FE model takes account the actual multi-device wafer-level configuration, as opposed to a single device. The results demonstrate that compositional gradients can make a significant contribution to the observed pattern of distortions.

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Singh, Arvinder, and Naveen Gupta. "Higher harmonic generation by self-focused q-Gaussian laser beam in preformed collisionless plasma channel." Laser and Particle Beams 32, no. 4 (October 27, 2014): 621–29. http://dx.doi.org/10.1017/s0263034614000639.

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AbstractThis paper presents an investigation of self-focusing of a q-Gaussian laser beam and its effect on harmonic generation in a preformed collisionless parabolic plasma channel. In the presence of a q-Gaussian laser beam, the carriers get redistributed from high field region to low field region on account of ponderomotive force as a result of which a transverse density gradient is produced in the channel which in turn generates plasma wave at pump frequency. Generated plasma wave interacts with the incident laser beam and generate higher harmonics of the incident laser beam. Moment theory has been used to derive differential equation for the spot size of laser beam propagating through the channel. The differential equation so obtained has been solved numerically. The effect of the intensity of laser beam, deviation of intensity distribution of laser beam along its wave front from Gaussian distribution, plasma density and depth of channel on beam width of laser beam and harmonic yield has been investigated. The effect of order of higher harmonic on harmonic yield has been also investigated.

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Kale, Akshay, Amirreza Malekanfard, and Xiangchun Xuan. "Analytical Guidelines for Designing Curvature-Induced Dielectrophoretic Particle Manipulation Systems." Micromachines 11, no. 7 (July 21, 2020): 707. http://dx.doi.org/10.3390/mi11070707.

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Curvature-induced dielectrophoresis (C-iDEP) is an established method of applying electrical energy gradients across curved microchannels to obtain a label-free manipulation of particles and cells. This method offers several advantages over the other DEP-based methods, such as increased chip area utilisation, simple fabrication, reduced susceptibility to Joule heating and reduced risk of electrolysis in the active region. Although C-iDEP systems have been extensively demonstrated to achieve focusing and separation of particles, a detailed mathematical analysis of the particle dynamics has not been reported yet. This work computationally confirms a fully analytical dimensionless study of the electric field-induced particle motion inside a circular arc microchannel, the simplest design of a C-iDEP system. Specifically, the analysis reveals that the design of a circular arc microchannel geometry for manipulating particles using an applied voltage is fully determined by three dimensionless parameters. Simple equations are established and numerically confirmed to predict the mutual relationships of the parameters for a comprehensive range of their practically relevant values, while ensuring design for safety. This work aims to serve as a starting point for microfluidics engineers and researchers to have a simple calculator-based guideline to develop C-iDEP particle manipulation systems specific to their applications.

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Tătulea-Codrean, Maria, and Eric Lauga. "Artificial chemotaxis of phoretic swimmers: instantaneous and long-time behaviour." Journal of Fluid Mechanics 856 (October 12, 2018): 921–57. http://dx.doi.org/10.1017/jfm.2018.718.

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Phoretic swimmers are a class of artificial active particles that has received significant attention in recent years. By making use of self-generated gradients (e.g. in temperature, electric potential or some chemical product) phoretic swimmers are capable of self-propulsion without the complications of mobile body parts or a controlled external field. Focusing on diffusiophoresis, we quantify in this paper the mechanisms through which phoretic particles may achieve chemotaxis, both at the individual and the non-interacting population level. We first derive a fully analytical law for the instantaneous propulsion and orientation of a phoretic swimmer with general axisymmetric surface properties, in the limit of zero Péclet number and small Damköhler number. We then apply our results to the case of a Janus sphere, one of the most common designs of phoretic swimmers used in experimental studies. We next put forward a novel application of generalised Taylor dispersion theory in order to characterise the long-time behaviour of a population of non-interacting phoretic swimmers. We compare our theoretical results with numerical simulations for the mean drift and anisotropic diffusion of phoretic swimmers in chemical gradients. Our results will help inform the design of phoretic swimmers in future experimental applications.

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Gomes, Marcelo Pego, Janaina Correa Nascimento, Itamar Magno Barbosa, Inacio Malmonge Martin, Rodrigo Savio Pessoa, Francisco das Chagas Carvalho, Luis Madson de Sousa Costa, and Bogos Nubar Sismanoglu. "Electric field gradient in microplasmas." IEEE Latin America Transactions 14, no. 2 (February 2016): 493–502. http://dx.doi.org/10.1109/tla.2016.7437184.

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Rizzo, Antonio, Kenneth Ruud, Trygve Helgaker, and Michał Jaszuński. "Electric field gradient, generalized Sternheimer shieldings and electric field gradient polarizabilities by multiconfigurational SCF response." Journal of Chemical Physics 109, no. 6 (August 8, 1998): 2264–74. http://dx.doi.org/10.1063/1.476794.

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Yang, Pei-Kun. "Modified Poisson equation for the electric field and electric field gradient." Journal of Molecular Liquids 223 (November 2016): 1213–25. http://dx.doi.org/10.1016/j.molliq.2016.09.021.

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Petrilli, Helena M., and Sonia Frota-Pessa. "Electric-field gradient inZr3Fe,Zr2Fe, andZr2Cu." Physical Review B 44, no. 19 (November 15, 1991): 10493–501. http://dx.doi.org/10.1103/physrevb.44.10493.

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Ponnambalam, M. J. "Electric field gradient in Ag alloys." physica status solidi (b) 135, no. 2 (June 1, 1986): 715–21. http://dx.doi.org/10.1002/pssb.2221350231.

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Yue, Yanmei, Kaiyu Xu, and Elias C. Aifantis. "Strain gradient and electric field gradient effects in piezoelectric cantilever beams." Journal of the Mechanical Behavior of Materials 24, no. 3-4 (August 1, 2015): 121–27. http://dx.doi.org/10.1515/jmbm-2015-0014.

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AbstractA piezoelectric beam model with strain gradient and electric gradient effects is proposed. An energy variational principle with strain, strain gradient, electric field, and electric field gradient considered as independent variables is postulated to develop the governing equations and boundary conditions. Moreover, two strain gradient coefficients and one electric field gradient coefficient are introduced to account for higher order coupling effects of underlying microstructure. Then the bending problem of a cantilever beam is solved to illustrate the theory. It is found that the deflection of the cantilever may depend strongly on the so-introduced gradient effects. As a result of the electromechanical coupling, the generated electric field may also be affected by the strain gradient. However, electric field gradient has a limited effect on the electric field.

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Govindaraj, R., and C. S. Sundar. "Anomalous variation of electric field gradient in." Physica B: Condensed Matter 406, no. 11 (May 2011): 2245–48. http://dx.doi.org/10.1016/j.physb.2011.03.041.

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Schwarz, K., H. Ripplinger, and P. Blaha. "Electric Field Gradient Calculations of Various Borides." Zeitschrift für Naturforschung A 51, no. 5-6 (June 1, 1996): 527–33. http://dx.doi.org/10.1515/zna-1996-5-627.

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Abstract A first-principles method for the computation of electric field gradients (EFG) is illustrated for various borides. It is based on energy band calculations using the full-potential linearized aug-mented plane wave (LAPW) method within density functional theory. From the self-consistent charge density distribution the EFG is obtained without further approximations by numerically solving Poisson's equation. The dependence of the EFG on structure, chemical composition or substitution is demonstrated for the diborides MB2 (with M = Ti, V, Cr, Zr, Nb, Mo, and Ta), the hexaborides (CaB6, SrB6 and BaB6) and boron carbide which is closely related to α-boron.

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Journal articles on the topic 'Electric field gradient focusing'

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