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Search Results: 1 - 10 of 35390 matches for " Seil Hong "
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A DO- and pH-Based Early Warning System of Nitrification Inhibition for Biological Nitrogen Removal Processes
Seil Hong,Il Choi,Byung Jin Lim,Hyunook Kim
Sensors , 2012, DOI: 10.3390/s121216334
Abstract: In Korea, more than 80% of municipal wastewater treatment plants (WWTPs) with capacities of 500 m3·d?1 or more are capable of removing nitrogen from wastewater through biological nitrification and denitrification processes. Normally, these biological processes show excellent performance, but if a toxic chemical is present in the influent to a WWTP, the biological processes (especially, the nitrification process) may be affected and fail to function normally; nitrifying bacteria are known very vulnerable to toxic substances. Then, the toxic compound as well as the nitrogen in wastewater may be discharged into a receiving water body without any proper treatment. Moreover, it may take significant time for the process to return back its normal state. In this study, a DO- and pH-based strategy to identify potential nitrification inhibition was developed to detect early the inflow of toxic compounds to a biological nitrogen removal process. This strategy utilizes significant changes observed in the oxygen uptake rate and the pH profiles of the mixed liquor when the activity of nitrifying bacteria is inhibited. Using the strategy, the toxicity from test wastewater with 2.5 mg·L?1 Hg2+, 0.5 mg·L?1 allythiourea, or 0.25 mg·L?1 chloroform could be successfully detected.
Antimicrobial applications of nanotechnology: methods and literature
Seil JT, Webster TJ
International Journal of Nanomedicine , 2012, DOI: http://dx.doi.org/10.2147/IJN.S24805
Abstract: ntimicrobial applications of nanotechnology: methods and literature Review (5690) Total Article Views Authors: Seil JT, Webster TJ Published Date June 2012 Volume 2012:7 Pages 2767 - 2781 DOI: http://dx.doi.org/10.2147/IJN.S24805 Received: 03 August 2011 Accepted: 31 August 2011 Published: 06 June 2012 Justin T Seil, Thomas J Webster Laboratory for Nanomedicine Research, School of Engineering, Brown University, Providence, RI, USA Abstract: The need for novel antibiotics comes from the relatively high incidence of bacterial infection and the growing resistance of bacteria to conventional antibiotics. Consequently, new methods for reducing bacteria activity (and associated infections) are badly needed. Nanotechnology, the use of materials with dimensions on the atomic or molecular scale, has become increasingly utilized for medical applications and is of great interest as an approach to killing or reducing the activity of numerous microorganisms. While some natural antibacterial materials, such as zinc and silver, possess greater antibacterial properties as particle size is reduced into the nanometer regime (due to the increased surface to volume ratio of a given mass of particles), the physical structure of a nanoparticle itself and the way in which it interacts with and penetrates into bacteria appears to also provide unique bactericidal mechanisms. A variety of techniques to evaluate bacteria viability, each with unique advantages and disadvantages, has been established and must be understood in order to determine the effectiveness of nanoparticles (diameter ≤100 nm) as antimicrobial agents. In addition to addressing those techniques, a review of select literature and a summary of bacteriostatic and bactericidal mechanisms are covered in this manuscript.
Spray deposition of live cells throughout the electrospinning process produces nanofibrous three-dimensional tissue scaffolds
Seil J, Webster TJ
International Journal of Nanomedicine , 2011, DOI: http://dx.doi.org/10.2147/IJN.S18803
Abstract: ay deposition of live cells throughout the electrospinning process produces nanofibrous three-dimensional tissue scaffolds Short Report (4312) Total Article Views Authors: Seil J, Webster TJ Published Date May 2011 Volume 2011:6 Pages 1095 - 1099 DOI: http://dx.doi.org/10.2147/IJN.S18803 Justin T Seil, Thomas J Webster Laboratories for Nanomedicine Research, School of Engineering, Brown University, Providence, RI, USA Abstract: Compared with traditional in-vitro cell culture materials, three-dimensional nanofibrous scaffolds provide a superior environment for promoting cell functions. Since nanofibrous scaffolds have nanometer pore sizes, cells are unable to penetrate on their own, so must be incorporated into the scaffold during fabrication to ensure proper cell distribution. In this study, biodegradable and cytocompatible poly(DL-lactide-co-glycolide) (PLGA) nanofibers were produced using an electrospinning process. As a model cell line, fibroblasts were periodically sprayed from a pump-action spray bottle onto the developing scaffold. The viability of cells before and after spraying, and also after incorporation into the scaffold, was compared. Results indicated that cell spraying and the scaffold fabrication process did not significantly reduce cell viability. These findings, thus, contribute to the understanding of how to produce more physiological relevant cell-seeded nanofibrous scaffolds, an important element for the future of nanotechnology and tissue engineering.
Diffraction of Plane Wave by Strip with Arbitrary Orientation of Wave Vector
Seil S. Sautbekov
PIER M , 2011, DOI: 10.2528/PIERM11071801
Abstract: The classical problem for diffraction of a plane wave with an arbitrarily oriented wave vector at a strip is considered asymptotically by Wiener-Hopf method. The boundary-value problem has been broken down into distinct Dirichlet and Neumann problems. Each of these boundary-value problems is consecutively solved by a reduction to a system of singular boundary integral equations and then to a system of Fredholm integral ones of second kind. They are solved effectively by a reduction to a system of linear algebraic equations with the help of the etalon integral and the saddle point method.
Factorization Method for Finite Fine Structures
Seil S. Sautbekov
PIER B , 2010, DOI: 10.2528/PIERB10071801
Abstract: This paper deals with the development of the Wiener-Hopf method for solving the diffraction of waves at fine strip-slotted structures. The classical problem for diffraction of plane wave at a strip is an important canonical problem. The boundary value problem is consecutively solved by a reduction to a system of singular boundary integral equations, and then to a system of Fredholm integral equations of the second kind, which effiectively is solved by one of three presented methods: A reduction to a system of the linear algebraic equations with the help of the etalon integral and the saddle point method numerical discretization based on Gauss quadrature formulas the method of successive approximations. The solution to the problem in the first method contains a denominator that takes into account the resonance process. Moreover, the precision of the main contribution of the short-wave asymptotic solution is ensured down to the quasi-stationary limit. The paper presents also comparisons of with earlier known results.
Spray deposition of live cells throughout the electrospinning process produces nanofibrous three-dimensional tissue scaffolds
Seil J,Webster TJ
International Journal of Nanomedicine , 2011,
Abstract: Justin T Seil, Thomas J WebsterLaboratories for Nanomedicine Research, School of Engineering, Brown University, Providence, RI, USAAbstract: Compared with traditional in-vitro cell culture materials, three-dimensional nanofibrous scaffolds provide a superior environment for promoting cell functions. Since nanofibrous scaffolds have nanometer pore sizes, cells are unable to penetrate on their own, so must be incorporated into the scaffold during fabrication to ensure proper cell distribution. In this study, biodegradable and cytocompatible poly(DL-lactide-co-glycolide) (PLGA) nanofibers were produced using an electrospinning process. As a model cell line, fibroblasts were periodically sprayed from a pump-action spray bottle onto the developing scaffold. The viability of cells before and after spraying, and also after incorporation into the scaffold, was compared. Results indicated that cell spraying and the scaffold fabrication process did not significantly reduce cell viability. These findings, thus, contribute to the understanding of how to produce more physiological relevant cell-seeded nanofibrous scaffolds, an important element for the future of nanotechnology and tissue engineering.Keywords: nanomaterials, tissue engineering, PLGA, nanotechnology
Decreased astroglial cell adhesion and proliferation on zinc oxide nanoparticle polyurethane composites
Justin T Seil,Thomas J Webster
International Journal of Nanomedicine , 2008,
Abstract: Justin T Seil, Thomas J WebsterLaboratory for Nanomedicine Research, Division of Engineering, Brown University, Providence, RI, USAAbstract: Nanomaterials offer a number of properties that are of interest to the field of neural tissue engineering. Specifically, materials that exhibit nanoscale surface dimensions have been shown to promote neuron function while simultaneously minimizing the activity of cells such as astrocytes that inhibit central nervous system regeneration. Studies demonstrating enhanced neural tissue regeneration in electrical fields through the use of conductive materials have led to interest in piezoelectric materials (or those materials which generate a transient electrical potential when mechanically deformed) such as zinc oxide (ZnO). It has been speculated that ZnO nanoparticles possess increased piezoelectric properties over ZnO micron particles. Due to this promise in neural applications, the objective of the present in vitro study was, for the first time, to assess the activity of astroglial cells on ZnO nanoparticle polymer composites. ZnO nanoparticles embedded in polyurethane were analyzed via scanning electron microscopy to evaluate nanoscale surface features of the composites. The surface chemistry was characterized via X-ray photoelectron spectroscopy. Astroglial cell response was evaluated based on cell adhesion and proliferation. Astrocyte adhesion was significantly reduced on ZnO nanoparticle/polyurethane (PU) composites with a weight ratio of 50:50 (PU:ZnO) wt.%, 75:25 (PU:ZnO) wt.%, and 90:10 (PU:ZnO) wt.% in comparison to pure PU. The successful production of ZnO nanoparticle composite scaffolds suitable for decreasing astroglial cell density demonstrates their potential as a nerve guidance channel material with greater efficiency than what may be available today.Keywords: zinc oxide, nanoparticles, astrocytes, neural tissue, nervous system, biomaterials
A closed form analytical solution to the radiation problem from a short dipole antenna above flat ground using spectral domain approach
Seil Sautbekov,Panayiotis Frangos,Christos Christakis,Konstantina Ioannidi
Physics , 2013,
Abstract: In this paper we consider the problem of radiation from a vertical short dipole above flat ground with losses, which represents the well known in the literature Sommerfeld radiation problem. We end up with a closed form analytical solution to the above problem for the received electric and magnetic field vectors above the ground in the far field area. The method of solution is formulated in the spectral domain, and by inverse three dimensional Fourier transformation and subsequent application of the Stationary Phase Method the final solutions in the physical space are derived. To our knowledge, the above closed form solutions are novel in the literature for the Sommerfeld radiation problem. Finally, the physical interpretation for the received fields formulae derived this paper are provided.
Inhibition of DNA ejection from bacteriophage by Mg+2 counterions
SeIl Lee,C. V. Tran,T. T. Nguyen
Quantitative Biology , 2008, DOI: 10.1063/1.3569133
Abstract: The problem of inhibiting viral DNA ejection from bacteriophages by multivalent counterions, specifically Mg$^{+2}$ counterions, is studied. Experimentally, it is known that MgSO$_4$ salt has a strong and non-monotonic effect on the amount of DNA ejected. There exists an optimal concentration at which the minimum amount of DNA is ejected from the virus. At lower or higher concentrations, more DNA is ejected from the capsid. We propose that this phenomenon is the result of DNA overcharging by Mg$^{+2}$ multivalent counterions. As Mg$^{+2}$ concentration increases from zero, the net charge of DNA changes from negative to positive. The optimal inhibition corresponds to the Mg$^{+2}$ concentration where DNA is neutral. At lower/higher concentrations, DNA genome is charged. It prefers to be in solution to lower its electrostatic self-energy, which consequently leads to an increase in DNA ejection. By fitting our theory to available experimental data, the strength of DNA$-$DNA short range attraction energies, mediated by Mg$^{+2}$, is found to be $-$0.004 $k_BT$ per nucleotide base. This and other fitted parameters agree well with known values from other experiments and computer simulations. The parameters are also in aggreement qualitatively with values for tri- and tetra-valent counterions.
Reentrant behavior of divalent counterion mediated DNA-DNA electrostatic interaction
SeIl Lee,Tung T Le,Toan T Nguyen
Quantitative Biology , 2009, DOI: 10.1103/PhysRevLett.105.248101
Abstract: The problem of DNA-DNA interaction mediated by divalent counterions is studied using computer simulation. Although divalent counterions cannot condense free DNA molecules in solution, we show that if DNA configurational entropy is restricted, divalent counterions can cause DNA reentrant condensation similar to that caused by tri- or tetra-valent counterions. DNA-DNA interaction is strongly repulsive at small or large counterion concentration and is negligible or slightly attractive for a concentration in between. Implications of our results to experiments of DNA ejection from bacteriophages are discussed. The quantitative result serves to understand electrostatic effects in other experiments involving DNA and divalent counterions.
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