The Experts below are selected from a list of 48915 Experts worldwide ranked by ideXlab platform
Kaoru Tsujii - One of the best experts on this subject based on the ideXlab platform.
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supercritical ethanol a fascinating Dispersion Medium for silica nanoparticles
Journal of Physical Chemistry B, 2007Co-Authors: Swapan K Ghosh, Shigeru Deguchi, Sadaatsu Mukai, Kaoru TsujiiAbstract:For the first time, the Dispersion stability of silica nanoparticles has been investigated in high-temperature and high-pressure ethanol by measuring the hydrodynamic diffusion coefficient of the particles by means of dynamic light scattering. The silica nanoparticles remain stable in ethanol within a wide temperature range of 24−304 °C at 12.3 MPa, and they start to aggregate at T ≥ 305 °C. Numerical analysis reveals that the net interparticle repulsive potential barrier decreases dramatically with increasing temperature due to the changes in the properties of the Medium. We observed that particles remain highly stable in the nonpolar supercritical ethanol in the temperature regime 241−304 °C, where the DLVO potential barrier is only 5−2 kBT. The Dispersion stability of silica nanoparticles at this low potential barrier in high-temperature and high-pressure ethanol, especially in the supercritical ethanol, is fascinating. The silica−ethanol system might be a unique and special example in the colloidal di...
Selim M Shahriar - One of the best experts on this subject based on the ideXlab platform.
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optomechanical resonator as a negative Dispersion Medium for enhancing the sensitivity bandwidth in a gravitational wave detector
Physical Review D, 2018Co-Authors: M Zhou, Selim M ShahriarAbstract:Recently, we proposed an optically pumped five-level gain with electromagnetically induced transparency system, which has a transparency dip superimposed on a gain profile and exhibits a negative Dispersion suitable for the white light cavity enhanced interferometric gravitational-wave detector [Phys. Rev. D 92, 082002 (2015)PRVDAQ1550-799810.1103/PhysRevD.92.082002]. Using this system as the negative Dispersion Medium in the white light cavity signal-recycling scheme, we get an enhancement in the quantum noise limited sensitivity–bandwidth product by a factor of ∼18. We have also shown how to realize such a system in practice using Zeeman sublevels in Rb87 at 795 nm [Opt. Commun. 402, 382 (2017)OPCOB80030-401810.1016/j.optcom.2017.06.036]. However, the Advanced Laser Interferometric Gravitational-Wave Observatory (aLIGO) operates at 1064 nm, and suitable transitions in Rb or other alkali atoms are not available at this wavelength. Therefore, it is necessary to consider a system that is consistent with the operating wavelength of aLIGO. Here, we present the realization of such a negative Dispersion Medium at 1064 nm with a microresonator, which supports optomechanical interaction. A strong control field is applied at a higher frequency, and, under certain conditions, a probe field at a lower frequency experiences a peak at the center of an absorption profile and a negative Dispersion in the transmission. Unlike in the gain with electromagnetically induced transparency case, we use the compound-cavity signal-recycling scheme, in which an auxiliary mirror is inserted in the dark port of the detector, and show that the enhancement factor can be as high as ∼15. However, using the parameters required for the sensitivity enhancement, the optomechanical system enters an instability region where the control field is depleted. We present an observer-based feedback control process used to stabilize the system.
Vicki Stone - One of the best experts on this subject based on the ideXlab platform.
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Inflammation and gene expression in the rat lung after instillation of silica nanoparticles: effect of size, Dispersion Medium and particle surface charge.
Toxicology letters, 2014Co-Authors: David M. Brown, Nilesh Kanase, Birgit K Gaiser, Helinor Jane Johnston, Vicki StoneAbstract:We investigated the effects of silica particles and nanoparticles (NPs) (50 nm and 200 nm) with a neutral and positively charged surface when dispersed in saline, bovine serum albumin (BSA) or lung lining fluid (LLF) 24 h post instillation into the lungs of rats. There was a significant increase in the recruitment of neutrophils in animals instilled with 50 nm plain and aminated NPs compared with 200 nm particles when dispersed in saline or BSA, but not when dispersed in LLF. There was no evidence of toxicity or an increase in the albumin content of the bronchoalveolar lavage fluid. Immunostaining for the transcription factor Nrf2 in BAL cells indicated that there was a significant increase in nuclear colocalisation in animals treated with plain and aminated 50 nm NPs compared with plain and aminated 200 nm particles when dispersed in saline, but no difference was observed between 50 nm and 200 nm aminated particles when dispersed in BSA. There was no difference in nuclear colocalisation with any of the particle types dispersed in LLF.This study suggests that low dose intratracheal exposure to silica nanoparticles can produce an acute inflammatory response and that the Dispersion Medium may influence the magnitude of this response.
Marc Secanell - One of the best experts on this subject based on the ideXlab platform.
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experimental and theoretical analysis of ink Dispersion stability for polymer electrolyte fuel cell applications
Journal of The Electrochemical Society, 2017Co-Authors: Shantanu Shukla, Subir Bhattacharjee, Adam Z Weber, Marc SecanellAbstract:Author(s): Shukla, S; Bhattacharjee, S; Weber, AZ; Secanell, M | Abstract: © The Author(s) 2017. The aggregate size in fuel cell catalyst inks depends on the type of Dispersion Medium, particle concentration, and addition of stabilizing agents. In this work, ink stability and particle size of carbon black and carbon black/Nafion Dispersions in four non-aqueous media, viz., methanol, ethanol, isopropanol and ethyl acetate are studied. Based on visual inspection, isopropanol is found to be the best Medium for Dispersion of carbon black inks. To rationalize this observation, a semi-empirical model based on diffusion-limited aggregation was developed to evaluate the rate of particle aggregation and predict the ink stability time for each Dispersion Medium. The proposed model supports the experimental observation by qualitatively predicting the same relationship between carbon stability and the Dispersion media. The model also showed that the dielectric constant of the Dispersion Medium and the particle zeta potential are primarily responsible for the ink stability. Particle size for the different inks was determined by dynamic light scattering with and without dilution. Experimental results show that Nafion is a strong stabilizing agent, increasing the ink stability and decreasing the particle size of carbon aggregates. The beneficial effects of Nafion are independent of its concentration and are observed even at Nafion volume fractions of 10 wt%. The interaction energy is found to be a strong function of the surface potential for the Dispersion Medium with a higher dielectric constant.
Hee-tak Kim - One of the best experts on this subject based on the ideXlab platform.
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Tuning the Ionomer Distribution in the Fuel Cell Catalyst Layer with Scaling the Ionomer Aggregate Size in Dispersion.
ACS Applied Materials & Interfaces, 2018Co-Authors: Gisu Doo, Ji Hye Lee, Seongmin Yuk, Sungyu Choi, Dong-hyun Lee, Dong Wook Lee, Hyun Gyu Kim, Sung Hyun Kwon, Seung Geol Lee, Hee-tak KimAbstract:With the demands for better performance of polymer electrolyte membrane fuel cells, studies on controlling the distribution of ionomers have recently gained interest. Here, we present a tunable ionomer distribution in the catalyst layer (CL) with dipropylene glycol (DPG) and water mixtures as the ionomer Dispersion Medium. Dynamic light scattering and molecular dynamics simulation demonstrate that, by increasing the DPG content in the Dispersion, the size of the ionomer aggregates in the Dispersion is exponentially reduced because of the higher affinity of DPG for Nafion ionomers. The ionomer distribution of the resulting CLs dictates the dimensional feature of the ionomer Dispersion. Although the ionomer distribution becomes more uniform with increasing the DPG content, an optimal power performance is obtained at a DPG content of 50 wt % regardless of feed humidity because of balanced proton and mass transports. As a guide for tuning the ionomer distribution, we suggest that the ionomer aggregates in the...