The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Xiangchu Xua - One of the best experts on this subject based on the ideXlab platform.
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tunable sheathless focusing of Diamagnetic particles in ferrofluid microflows with a single set of overhead permanent magnets
Analytical Chemistry, 2018Co-Authors: Qi Che, Amirreza Malekanfard, Quanliang Cao, Maohua Wang, Xiangchu XuaAbstract:There has been increasing interest in the use of magnetic fluids to manipulate Diamagnetic particles in microfluidic devices. Current methods for Diamagnetic-particle focusing in magnetic fluids require either a pair of repulsive magnets or a Diamagnetic sheath flow. We demonstrate herein a tunable, sheathless focusing of Diamagnetic particles in a microchannel ferrofluid flow with a single set of overhead permanent magnets. Particles are focused into a single stream near the bottom wall of a straight rectangular microchannel, where a magnetic-field minimum is formed as a result of the magnetization of the ferrofluid. This focusing can be readily switched off and on by removing and replacing the permanent magnets. More importantly, the particle-focusing position can be tuned by shifting the magnets with respect to the microchannel. We perform a systematic experimental study of the parametric effects of the fluid-particle-channel system on Diamagnetic-particle focusing in terms of a defined particle-focusi...
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simultaneous Diamagnetic and magnetic particle trapping in ferrofluid microflows via a single permanent magnet
Biomicrofluidics, 2015Co-Authors: Yilong Zhou, Dhileep Thanjavu Kuma, Akshay Kale, Joh Dubose, Yongxi Song, Junsheng Wang, Xiangchu XuaAbstract:Trapping and preconcentrating particles and cells for enhanced detection and analysis are often essential in many chemical and biological applications. Existing methods for Diamagnetic particle trapping require the placement of one or multiple pairs of magnets nearby the particle flowing channel. The strong attractive or repulsive force between the magnets makes it difficult to align and place them close enough to the channel, which not only complicates the device fabrication but also restricts the particle trapping performance. This work demonstrates for the first time the use of a single permanent magnet to simultaneously trap Diamagnetic and magnetic particles in ferrofluid flows through a T-shaped microchannel. The two types of particles are preconcentrated to distinct locations of the T-junction due to the induced negative and positive magnetophoretic motions, respectively. Moreover, they can be sequentially released from their respective trapping spots by simply increasing the ferrofluid flow rate. In addition, a three-dimensional numerical model is developed, which predicts with a reasonable agreement the trajectories of Diamagnetic and magnetic particles as well as the buildup of ferrofluid nanoparticles.
Babak Vaseghi - One of the best experts on this subject based on the ideXlab platform.
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simultaneous effects of pressure and temperature on the binding energy and Diamagnetic susceptibility of a laser dressed donor in a spherical quantum dot
Physica B-condensed Matter, 2012Co-Authors: Babak Vaseghi, T SajadiAbstract:Abstract Binding energies and Diamagnetic susceptibility of an impurity in a spherical GaAs quantum dot under the simultaneous influence of static pressure, temperature and laser radiation are investigated. Pressure- and temperature-dependent dressed potential which is produced by the combined effects of laser radiation and impurity considerably change the energy spectrum and Diamagnetic susceptibility of the system. It is shown that binding energies and Diamagnetic susceptibility increase with increasing pressure. Moreover, laser radiation effects on the Diamagnetic susceptibility are not significant in comparison with its effects on the binding energy.
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simultaneous effects of hydrostatic pressure and conduction band non parabolicity on binding energies and Diamagnetic susceptibility of a hydrogenic impurity in spherical quantum dots
Communications in Theoretical Physics, 2011Co-Authors: G Rezaei, N A Doostimotlagh, Babak VaseghiAbstract:Simultaneous effects of conduction band non-parabolicity and hydrostatic pressure on the binding energies of 1S, 2S, and 2P states along with Diamagnetic susceptibility of an on-center hydrogenic impurity confined in typical GaAs/AlxGa1 xAs spherical quantum dots are theoretically investigated using the matrix diagonalization method. In this regard, the effect of band non-parabolicity has been performed using the Luttinger-Kohn effective mass equation. The binding energies and the Diamagnetic susceptibility of the hydrogenic impurity are computed as a function of the dot radius and different values of the pressure in the presence of conduction band non-parabolicity effect. The results we arrived at are as follows: the incorporation of the band edge non-parabolicity increases the binding energies and decreases the absolute value of the Diamagnetic susceptibility for a given pressure and radius; the binding energies increase and the magnitude of the Diamagnetic susceptibility reduces with increasing pressure.
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conduction band non parabolicity effect on the binding energy and the Diamagnetic susceptibility of an on center hydrogenic impurity in spherical quantum dots
Physica E-low-dimensional Systems & Nanostructures, 2011Co-Authors: G Rezaei, N A Doostimotlagh, Babak VaseghiAbstract:Energy eigenvalues, binding energy and Diamagnetic susceptibility of an on-center hydrogenic impurity confined in typical GaAs/AlxGa1� xAs spherical quantum dots are theoretically investigated, using the matrix diagonalization method. In this regard, the effect of band non-parabolicity has been performed, by means of the Luttinger–Kohn effective mass equation. The lower-lying states, the binding energy and the Diamagnetic susceptibility of the hydrogenic impurity are computed as a function of the dot size, with and without conduction band non-parabolicity effect. Results show that the band edge nonparabolicity considerably changes the electronic structure, the binding energy and the Diamagnetic susceptibility, especially at small radii.
Lixin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Magnetic Field Is the Dominant Factor to Induce the Response of Streptomyces avermitilis in Altered Gravity Simulated by Diamagnetic Levitation
2013Co-Authors: Mei Liu, Hong Gao, Peng Shang, Xianlong Zhou, Elizabeth Jane Ashforth, Ying Zhuo, Difei Chen, Biao Ren, Zhiheng Liu, Lixin ZhangAbstract:Background: Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to simulate an altered gravity environment, as in space. In this study, using Streptomyces avermitilis as the test organism, we investigate whether changes in magnetic field and altered gravity induce changes in morphology and secondary metabolism. We find that a strong magnetic field (12T) inhibit the morphological development of S. avermitilis in solid culture, and increase the production of secondary metabolites. Methodology/Principal Findings: S. avermitilis on solid medium was levitated at 0 g*, 1 g * and 2 g * in an altered gravity environment simulated by Diamagnetic levitation and under a strong magnetic field, denoted by the asterix. The morphology was obtained by electromicroscopy. The production of the secondary metabolite, avermectin, was determined by OD 245 nm. The results showed that Diamagnetic levitation could induce a physiological response in S. avermitilis. The difference between 1 g * and the control group grown without the strong magnetic field (1 g), showed that the magnetic field was a more dominant factor influencing changes in morphology and secondary metabolite production, than altered gravity. Conclusion/Significance: We have discovered that magnetic field, rather than altered gravity, is the dominant factor in altered gravity simulated by Diamagnetic levitation, therefore care should to be taken in the interpretation of results when using Diamagnetic levitation as a technique to simulate altered gravity. Hence, these results are significant, and timely t
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magnetic field is the dominant factor to induce the response of streptomyces avermitilis in altered gravity simulated by Diamagnetic levitation
PLOS ONE, 2011Co-Authors: Mei Liu, Hong Gao, Peng Shang, Xianlong Zhou, Elizabeth Jane Ashforth, Ying Zhuo, Difei Chen, Biao Ren, Zhiheng Liu, Lixin ZhangAbstract:Background Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to simulate an altered gravity environment, as in space. In this study, using Streptomyces avermitilis as the test organism, we investigate whether changes in magnetic field and altered gravity induce changes in morphology and secondary metabolism. We find that a strong magnetic field (12T) inhibit the morphological development of S. avermitilis in solid culture, and increase the production of secondary metabolites. Methodology/Principal Findings S. avermitilis on solid medium was levitated at 0 g*, 1 g* and 2 g* in an altered gravity environment simulated by Diamagnetic levitation and under a strong magnetic field, denoted by the asterix. The morphology was obtained by electromicroscopy. The production of the secondary metabolite, avermectin, was determined by OD245 nm. The results showed that Diamagnetic levitation could induce a physiological response in S. avermitilis. The difference between 1 g* and the control group grown without the strong magnetic field (1 g), showed that the magnetic field was a more dominant factor influencing changes in morphology and secondary metabolite production, than altered gravity. Conclusion/Significance We have discovered that magnetic field, rather than altered gravity, is the dominant factor in altered gravity simulated by Diamagnetic levitation, therefore care should to be taken in the interpretation of results when using Diamagnetic levitation as a technique to simulate altered gravity. Hence, these results are significant, and timely to researchers considering the use of Diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena.
Rajkumar Hajra - One of the best experts on this subject based on the ideXlab platform.
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dynamic unmagnetized plasma in the Diamagnetic cavity around comet 67p churyumov gerasimenko
Monthly Notices of the Royal Astronomical Society, 2018Co-Authors: Rajkumar Hajra, Pierre Henri, X Vallieres, Jerome More, N Gilet, Gaetan Wattieaux, Charlotte Goetz, I Richter, B T Tsurutani, H GunellAbstract:The Rosetta orbiter witnessed several hundred Diamagnetic cavity crossings (unmagnetized regions) around comet 67P/Churyumov–Gerasimenko during its two year survey of the comet. The characteristics of the plasma environment inside these Diamagnetic regions are studied using in situ measurements by the Rosetta Plasma Consortium instruments. Although the unmagnetized plasma density has been observed to exhibit little dynamics compared to the very dynamical magnetized cometary plasma, we detected several localized dynamic plasma structures inside those Diamagnetic regions. These plasma structures are not related to the direct ionization of local cometary neutrals. The structures are found to be steepened, asymmetric plasma enhancements with typical rising-to-descending slope ratio of ∼2.8 (±1.9), skewness ∼0.43 (±0.36), mean duration of ∼2.7 (±0.9) min and relative density variation ΔN/N of ∼0.5 (±0.2), observed close to the electron exobase. Similar steepened plasma density enhancements were detected at the magnetized boundaries of the Diamagnetic cavity as well as outside the Diamagnetic region. The plausible scalelength and propagation direction of the structures are estimated from simple plasma dynamics considerations. It is suggested that they are large-scale unmagnetized plasma enhancements, transmitted from the very dynamical outer magnetized region to the inner magnetic field-free cavity region.
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Diamagnetic region(s): structure of the unmagnetized plasma around Comet 67P/CG
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: Pierre Henri, Rajkumar Hajra, X Vallieres, Charlotte Goetz, I Richter, K.-h Glassmeier, M. Galand, M. Rubin, A. I. Eriksson, Z. NemethAbstract:The ESA's comet chaser Rosetta has monitored the evolution of the ionized atmosphere of comet 67P/Churyumov–Gerasimenko (67P/CG) and its interaction with the solar wind, during more than 2 yr. Around perihelion, while the cometary outgassing rate was highest, Rosetta crossed hundreds of unmagnetized regions, but did not seem to have crossed a large-scale Diamagnetic cavity as anticipated. Using in situ Rosetta observations, we characterize the structure of the unmagnetized plasma found around comet 67P/CG. Plasma density measurements from RPC-MIP are analysed in the unmagnetized regions identified with RPC-MAG. The plasma observations are discussed in the context of the cometary escaping neutral atmosphere , observed by ROSINA/COPS. The plasma density in the different Diamagnetic regions crossed by Rosetta ranges from ∼100 to ∼1500 cm −3. They exhibit a remarkably systematic behaviour that essentially depends on the comet activity and the cometary ionosphere expansion. An effective total ionization frequency is obtained from in situ observations during the high outgassing activity phase of comet 67P/CG. Although several Diamagnetic regions have been crossed over a large range of distances to the comet nucleus (from 50 to 400 km) and to the Sun (1.25–2.4 au), in situ observations give strong evidence for a single Diamagnetic region, located close to the electron exobase. Moreover, the observations are consistent with an unstable contact surface that can locally extend up to about 10 times the electron exobase.
Sarah L Price - One of the best experts on this subject based on the ideXlab platform.
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calculation of Diamagnetic susceptibility tensors of organic crystals from coronene to pharmaceutical polymorphs
Journal of Physical Chemistry A, 2020Co-Authors: Nadia M Uddin, Louise S. Price, Sarah L PriceAbstract:Understanding why crystallization in strong magnetic fields can lead to new polymorphs requires methods to calculate the Diamagnetic response of organic molecular crystals. We develop the calculation of the macroscopic Diamagnetic susceptibility tensor, χcryst, for organic molecular crystals using periodic density functional methods. The crystal magnetic susceptibility tensor, χcryst, for all experimentally known polymorphs, and its molecular counterpart, χmol, are calculated for flexible pharmaceuticals such as carbamazepine, flufenamic acid, and chalcones, and rigid molecules, such as benzene, pyridine, acridine, anthracene, and coronene, whose molecular magnetic properties have been traditionally studied. A tensor addition method is developed to approximate the crystal Diamagnetic susceptibility tensor, χcryst, from the molecular one, χmol, giving good agreement with those calculated directly using the more costly periodic density functional method for χcryst. The response of pharmaceutical molecules a...