The Experts below are selected from a list of 89982 Experts worldwide ranked by ideXlab platform
Janusz Pawliszyn - One of the best experts on this subject based on the ideXlab platform.
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Diode laser-based Concentration Gradient detector for capillary isotachophoresis
Journal of Microcolumn Separations, 1993Co-Authors: Janusz PawliszynAbstract:A diode laser-based, universal Concentration Gradient detector was applied to capillary isotachophoresis (CITP). The inexpensive CITP instrument also included a 30 cm long, 300 μm i.d. capillary, a 5 cm focal length lens and a photodiode light beam position sensor. Factors affecting the sensitivity and performance of the detector, i.e., separation conditions, spatial resolution of the detector, and the Concentration of leading electrolyte, were discussed theoretically and experimentally. The diode laser-based Concentration Gradient detector appears to be one of the best detectors for CITP due to its high resolution, derivative nature, and low cost. The experimental detection limit reached 4 × 10−6 M for small cations, which was near the theoretical value. The detection limit can be further reduced by at least one order of magnitude if a longer capillary is used. The CITP-Concentration Gradient detector instrument has high efficiency, and was applied to detect impurities in antidepressant drugs.
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Capillary isoelectric focusing with a universal Concentration Gradient imaging system using a charge-coupled photodiode array
Analytical Chemistry, 1992Co-Authors: Janusz PawliszynAbstract:The focused patterns of protein samples by capillary isoelectric focusing (CIEF) were monitored without mobilization by a Concentration Gradient imaging detection system based on the Schileren shadowgraph method. The system consisted of a low-power He-Ne laser and a 1024 pixel charge-coupled device (CCD). The length of the capillary, the position of the CCD sensor, and the separation voltage were optimized. Computer software for background correction and noise reduction was also employed
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Chemical sensing using Concentration Gradient transients produced during diffusive transport of analytes
Analytical Chemistry, 1992Co-Authors: Janusz PawliszynAbstract:The formation of Concentration Gradients during the extraction of analytes from an aqueous sample into an organic liquid phase is the principle of this new chemical sensing method. The refractive index Gradient is probed by measuring the deflection of a focused laser beam which passes close to the interface between the two phases. The maximum of the Concentration Gradient transient is proportional to the Concentration of analyte in the sample. The large Concentration Gradients generated at the interface during the initial stages of the mass transport process ensure good sensitivity
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high performance capillary isoelectric focusing with a Concentration Gradient detector
Analytical Chemistry, 1992Co-Authors: Janusz PawliszynAbstract:The Concentration Gradient detector is based on Schlieren optics, consisting of a He-Ne laser and a light beam position sensor. A 50 μm wide zone of separated ovalbumin was monitored in the experiments. The sample Concentration could be estimated from the signal peak height with a dynamic range of 0.1- 1.0 mg/ml. The sensitivity of the detector for high molecular weight proteins is in the same order of magnitude as that of a UV absorbance detector, but with a much smaller detection volume.
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Isoelectric focusing of proteins in a microcapillary with universal Concentration Gradient detection
Journal of Microcolumn Separations, 1992Co-Authors: Janusz PawliszynAbstract:Proteins were separated by capillary isoelectric focusing (CIEF) performed in a 5-μm i.d., 12-cm long uncoated capillary, and detected by an on-column Concentration Gradient detector based on Schlieren optics. The narrow capillary allows the application of a 15-kV separation voltage. The high voltage resulted in a very narrow 30-μm wide zone for carbonic anhydrase, which corresponded to a 60-fL zone volume. All focused proteins could be detected by the universal Concentration Gradient detector without derivatization in less than 7 min. On-column mass detection limits for proteins were at the 100 amol level, which was lower than that of a UV-vis absorption spectrometric detector. The detection volume of the detector was calculated to be 20 fL, the smallest detection volumes reported to date for optical or spectroscopic detectors. This microcapillary CIEF-Concentration Gradient detector system may be a useful technique for direct analysis of proteins at the single cell level.
Zhenghe Xu - One of the best experts on this subject based on the ideXlab platform.
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synthesis of porous mnco2o4 microspheres with yolk shell structure induced by Concentration Gradient and the effect on their performance in electrochemical energy storage
RSC Advances, 2016Co-Authors: Guoyong Huang, Shengming Xu, Yue Yang, Zhenghe XuAbstract:In this study, novel spherical yolk–shell MnCo2O4 powders with Concentration Gradient have been synthesized. The porous microspheres with yolk–shell structure (2.00–3.00 μm in average diameter, ∼200 nm in thickness of shell) are built up by irregular nanoparticles attached to each other. It is shown that the formation of yolk–shell structure may be induced by the core–shell Concentration Gradient. And the Co:Mn atomic ratios of core and shell are about 1.65:1 and 2.61:1, respectively. Interestingly, a similar uniform spherical MnCo2O4 without yolk–shell structure and Concentration Gradient prepared as a contrast, the superior electrochemical performance of the former by using in Li-ion batteries and supercapacitors has been proved including higher initial discharge capacity (1445.1 mA h g−1 at 0.2 A g−1) and initial specific capacitance (761.3 F g−1 at 2 A g−1), and more advanced capacity retention (∼860.0 mA h g−1 after 40 cycles at 0.2 A g−1, and ∼330.0 F g−1 after 3000 cycles at 12 A g−1).
Guoyong Huang - One of the best experts on this subject based on the ideXlab platform.
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synthesis of porous mnco2o4 microspheres with yolk shell structure induced by Concentration Gradient and the effect on their performance in electrochemical energy storage
RSC Advances, 2016Co-Authors: Guoyong Huang, Shengming Xu, Yue Yang, Zhenghe XuAbstract:In this study, novel spherical yolk–shell MnCo2O4 powders with Concentration Gradient have been synthesized. The porous microspheres with yolk–shell structure (2.00–3.00 μm in average diameter, ∼200 nm in thickness of shell) are built up by irregular nanoparticles attached to each other. It is shown that the formation of yolk–shell structure may be induced by the core–shell Concentration Gradient. And the Co:Mn atomic ratios of core and shell are about 1.65:1 and 2.61:1, respectively. Interestingly, a similar uniform spherical MnCo2O4 without yolk–shell structure and Concentration Gradient prepared as a contrast, the superior electrochemical performance of the former by using in Li-ion batteries and supercapacitors has been proved including higher initial discharge capacity (1445.1 mA h g−1 at 0.2 A g−1) and initial specific capacitance (761.3 F g−1 at 2 A g−1), and more advanced capacity retention (∼860.0 mA h g−1 after 40 cycles at 0.2 A g−1, and ∼330.0 F g−1 after 3000 cycles at 12 A g−1).
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core shell ellipsoidal mnco2o4 anode with micro nano structure and Concentration Gradient for lithium ion batteries
ACS Applied Materials & Interfaces, 2014Co-Authors: Guoyong Huang, Hongyu SunAbstract:In this study, novel core–shell ellipsoidal MnCo2O4 powders with desired micro/nano-structure and a unique Concentration Gradient have been synthesized as anode material for Li-ion batteries. The special porous ellipsoid (2.5–4.5 μm in the long axis, 1.5–2.5 μm in the short axis, 200–300 nm in the thickness of shell) is built up by irregular nanoparticles attached to each other, and corresponding to the ellipsoid with Concentration Gradient, the Co/Mn atomic ratios of core and shell are about 1.76:1 and 2.34:1, respectively. The good performance, including high initial discharge capacities (1433.3 mAhg–1 at 0.1 Ag–1 and 1248.4 mAhg–1 at 0.4 Ag–1), advanced capacity retention (∼900.0 mAhg–1 after 60 cycles at 0.1 Ag–1), and fair rate performance (∼620.0 mAhg–1 after 50 cycles at 0.4 Ag–1) has been measured by the battery test. Remarkably, the ellipsoidal shape and core–shell microstructure with Concentration Gradient are still maintained after 70 cycles of charge/discharge at 0.1 Ag–1.
Fei Peng - One of the best experts on this subject based on the ideXlab platform.
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in vitro reconstruction of branched tubular structures from lung epithelial cells in high cell Concentration Gradient environment
Scientific Reports, 2015Co-Authors: Masaya Hagiwara, Fei PengAbstract:We have succeeded in developing hollow branching structure in vitro commonly observed in lung airway using primary lung airway epithelial cells. Cell Concentration Gradient is the key factor that determines production of the branching cellular structures, as optimization of this component removes the need for heterotypic culture. The higher cell Concentration leads to the more production of morphogens and increases the growth rate of cells. However, homogeneous high cell Concentration does not make a branching structure. Branching requires sufficient space in which cells can grow from a high Concentration toward a low Concentration. Simulation performed using a reaction-diffusion model revealed that long-range inhibition prevents cells from branching when they are homogeneously spread in culture environments, while short-range activation from neighboring cells leads to positive feedback. Thus, a high cell Concentration Gradient is required to make branching structures. Spatial distributions of morphogens, such as BMP-4, play important roles in the pattern formation. This simple yet robust system provides an optimal platform for the further study and understanding of branching mechanisms in the lung airway, and will facilitate chemical and genetic studies of lung morphogenesis programs.
David Juncker - One of the best experts on this subject based on the ideXlab platform.
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microfluidic quadrupole and floating Concentration Gradient
Nature Communications, 2011Co-Authors: Mohammad A Qasaimeh, Thomas Gervais, David JunckerAbstract:The concept of fluidic multipoles, in analogy to electrostatics, has long been known as a particular class of solutions of the Navier-Stokes equation in potential flows; however, experimental observations of fluidic multipoles and of their characteristics have not been reported yet. Here we present a two-dimensional microfluidic quadrupole and a theoretical analysis consistent with the experimental observations. The microfluidic quadrupole was formed by simultaneously injecting and aspirating fluids from two pairs of opposing apertures in a narrow gap formed between a microfluidic probe and a substrate. A stagnation point was formed at the centre of the microfluidic quadrupole, and its position could be rapidly adjusted hydrodynamically. Following the injection of a solute through one of the poles, a stationary, tunable, and movable-that is, 'floating'-Concentration Gradient was formed at the stagnation point. Our results lay the foundation for future combined experimental and theoretical exploration of microfluidic planar multipoles including convective-diffusive phenomena.
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Microfluidic quadrupole and floating Concentration Gradient
Nature Communications, 2011Co-Authors: Mohammad A Qasaimeh, Thomas Gervais, David JunckerAbstract:Quadrupoles have many engineering applications, but experimental observations of fluidic multipoles have not been reported. This study presents an experimental two-dimensional microfluidic quadrupole, a theoretical analysis consistent with observations, and a first application as a channel-free floating Gradient generator. The concept of fluidic multipoles, in analogy to electrostatics, has long been known as a particular class of solutions of the Navier-Stokes equation in potential flows; however, experimental observations of fluidic multipoles and of their characteristics have not been reported yet. Here we present a two-dimensional microfluidic quadrupole and a theoretical analysis consistent with the experimental observations. The microfluidic quadrupole was formed by simultaneously injecting and aspirating fluids from two pairs of opposing apertures in a narrow gap formed between a microfluidic probe and a substrate. A stagnation point was formed at the centre of the microfluidic quadrupole, and its position could be rapidly adjusted hydrodynamically. Following the injection of a solute through one of the poles, a stationary, tunable, and movable—that is, 'floating'—Concentration Gradient was formed at the stagnation point. Our results lay the foundation for future combined experimental and theoretical exploration of microfluidic planar multipoles including convective–diffusive phenomena.