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Search Results: 1 - 10 of 147515 matches for " Brian K. Kwon "
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Multi-walled carbon nanotubes induce COX-2 and iNOS expression via MAP Kinase-dependent and -independent mechanisms in mouse RAW264.7 macrophages
Jong Kwon Lee, Brian C. Sayers, Kyung-Soo Chun, Huei-Chen Lao, Jeanette K. Shipley-Phillips, James C. Bonner, Robert Langenbach
Particle and Fibre Toxicology , 2012, DOI: 10.1186/1743-8977-9-14
Abstract: RAW264.7 macrophages were exposed to MWCNTs or carbon black nanoparticles (CBNPs) over a range of doses and time course. Uptake and subcellular localization of MWCNTs was visualized by transmission electron microscopy (TEM). Protein levels of COX-2, iNOS, and ERK1,2 (total ERK and phosphorylated ERK) were measured by Western blot analysis. Prostaglandin-E2 (PGE2) and nitric oxide (NO) levels in cell supernatants were measured by ELISA and Greiss assay, respectively.MWCNTs, but not CBNPs, induced COX-2 and iNOS in a time- and dose-dependent manner. COX-2 and iNOS induction by MWCNTs correlated with increased PGE2 and NO production, respectively. MWCNTs caused ERK1,2 activation and inhibition of ERK1,2 (U0126) blocked MWCNT induction of COX-2 and PGE2 production, but did not reduce the induction of iNOS. Inhibition of iNOS (L-NAME) did not affect ERK1,2 activation, nor did L-NAME significantly decrease COX-2 induction by MWCNT. Nickel nanoparticles (NiNPs), which are present in MWCNTs as a residual catalyst, also induced COX-2 via ERK-1,2. However, a comparison of COX-2 induction by MWCNTs containing 4.5 and 1.8% Ni did not show a significant difference in ability to induce COX-2, indicating that characteristics of MWCNTs in addition to Ni content contribute to COX-2 induction.This study identifies COX-2 and subsequent PGE2 production, along with iNOS induction and NO production, as inflammatory mediators involved in the macrophage response to MWCNTs. Furthermore, our work demonstrates that COX-2 induction by MWCNTs in RAW264.7 macrophages is ERK1,2-dependent, while iNOS induction by MWCNTs is ERK1,2-independent. Our data also suggest contributory physicochemical factors other than residual Ni catalyst play a role in COX-2 induction to MWCNT.
Differentiation of Material Temperature through the Application of Increased Localized Dissolution via Heat Transfer  [PDF]
Brian K. Chen
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2015, DOI: 10.4236/jasmi.2015.53005
Abstract: Increased temperature of a solution increases its solubility, allowing for a greater level of dissolution of the solute. A greater level of dissolution will result in a change in the density of the solution. When a localized area of the solution is of a different temperature, this will affect the localized density. Density is one of the factors affecting rate of sinking and the difference in temperature will lead to a change in the rate of sinking. Thus, when an object is at different temperatures, it will transfer heat to or from the solution in different manners and the rate of sinking will be different. This study tested whether sinking rate in a solution with excess solute could be used to judge the temperature of an object and the effect was confirmed with impure Graphite blocks in a Potassium Iodide solution.
Novel Biomarkers of Arterial and Venous Ischemia in Microvascular Flaps
Gerard K. Nguyen, Brian H. Hwang, Yiqiang Zhang, John F. W. Monahan, Gabrielle B. Davis, Yong Suk Lee, Neli P. Ragina, Charles Wang, Zhao Y. Zhou, Young Kwon Hong, Ryan M. Spivak, Alex K. Wong
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0071628
Abstract: The field of reconstructive microsurgery is experiencing tremendous growth, as evidenced by recent advances in face and hand transplantation, lower limb salvage after trauma, and breast reconstruction. Common to all of these procedures is the creation of a nutrient vascular supply by microsurgical anastomosis between a single artery and vein. Complications related to occluded arterial inflow and obstructed venous outflow are not uncommon, and can result in irreversible tissue injury, necrosis, and flap loss. At times, these complications are challenging to clinically determine. Since early intervention with return to the operating room to re-establish arterial inflow or venous outflow is key to flap salvage, the accurate diagnosis of early stage complications is essential. To date, there are no biochemical markers or serum assays that can predict these complications. In this study, we utilized a rat model of flap ischemia in order to identify the transcriptional signatures of venous congestion and arterial ischemia. We found that the critical ischemia time for the superficial inferior epigastric fasciocutaneus flap was four hours and therefore performed detailed analyses at this time point. Histolgical analysis confirmed significant differences between arterial and venous ischemia. The transcriptome of ischemic, congested, and control flap tissues was deciphered by performing Affymetrix microarray analysis and verified by qRT-PCR. Principal component analysis revealed that arterial ischemia and venous congestion were characterized by distinct transcriptomes. Arterial ischemia and venous congestion was characterized by 408 and 1536>2-fold differentially expressed genes, respectively. qRT-PCR was used to identify five candidate genes Prol1, Muc1, Fcnb, Il1b, and Vcsa1 to serve as biomarkers for flap failure in both arterial ischemia and venous congestion. Our data suggests that Prol1 and Vcsa1 may be specific indicators of venous congestion and allow clinicians to both diagnose and successfully treat microvascular complications before irreversible tissue damage and flap loss occurs.
Ketogenic Diet Improves Forelimb Motor Function after Spinal Cord Injury in Rodents
Femke Streijger, Ward T. Plunet, Jae H. T. Lee, Jie Liu, Clarrie K. Lam, Soeyun Park, Brett J. Hilton, Bas L. Fransen, Keely A. J. Matheson, Peggy Assinck, Brian K. Kwon, Wolfram Tetzlaff
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078765
Abstract: High fat, low carbohydrate ketogenic diets (KD) are validated non-pharmacological treatments for some forms of drug-resistant epilepsy. Ketones reduce neuronal excitation and promote neuroprotection. Here, we investigated the efficacy of KD as a treatment for acute cervical spinal cord injury (SCI) in rats. Starting 4 hours following C5 hemi-contusion injury animals were fed either a standard carbohydrate based diet or a KD formulation with lipid to carbohydrate plus protein ratio of 3:1. The forelimb functional recovery was evaluated for 14 weeks, followed by quantitative histopathology. Post-injury 3:1 KD treatment resulted in increased usage and range of motion of the affected forepaw. Furthermore, KD improved pellet retrieval with recovery of wrist and digit movements. Importantly, after returning to a standard diet after 12 weeks of KD treatment, the improved forelimb function remained stable. Histologically, the spinal cords of KD treated animals displayed smaller lesion areas and more grey matter sparing. In addition, KD treatment increased the number of glucose transporter-1 positive blood vessels in the lesion penumbra and monocarboxylate transporter-1 (MCT1) expression. Pharmacological inhibition of MCTs with 4-CIN (α-cyano-4-hydroxycinnamate) prevented the KD-induced neuroprotection after SCI, In conclusion, post-injury KD effectively promotes functional recovery and is neuroprotective after cervical SCI. These beneficial effects require the function of monocarboxylate transporters responsible for ketone uptake and link the observed neuroprotection directly to the function of ketones, which are known to exert neuroprotection by multiple mechanisms. Our data suggest that current clinical nutritional guidelines, which include relatively high carbohydrate contents, should be revisited.
Spectral element modelling of the thermally induced vibration of an axially moving plate
U. Lee,K. Kwon
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: To develop a spectral element model for accurate prediction of the dynamic characteristics of an axially moving thin uniform plate subjected to sudden thermal loadings on its surfaces.Design/methodology/approach: First, we have derived the governing equations of motion by using the Hamilton’s principle. Secondly, we have used the wave solutions, which satisfy the governing equations of motion in the frequency domain, as the frequency-dependent shape functions to formulate the spectral element matrix by using the variational approach. Thirdly, the extremely high accuracy of the spectral element model has been evaluated by comparing the dynamic responses obtained by the spectral element analysis with the results obtained by using the conventional finite element analysis.Findings: It has been numerically shown that the present spectral element model provides very accurate dynamic responses of an axially moving uniform plate by treating the whole plate as a single finite element, regardless of its length.Practical implications: Numerical investigations have shown that the thermally induced vibration characteristics of an axially moving plate depends on the duration and frequency characteristics of externally applied thermal loadings as well as its moving speed.Originality/value: The paper is the first to develop the spectral element model for the axially moving plates subjected to thermal loadings. The present spectral element model can be applied to the galvanized steel strip passing through a hot zinc tank, for instance.
Thermally induced vibration of an axially- traveling strip: spectral element analysis
U. Lee,K. Kwon
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: A spectral element model is developed for accurate prediction of the dynamic characteristics of an axially-traveling strip subjected to a sudden thermal loading.Design/methodology/approach: The spectral element model is formulated from the frequency-dependent dynamic shape functions which satisfy the governing equations in the frequency-domain and its extremely high accuracy is evaluated by comparing with the conventional finite element model in which simple polynomials are used as the shape functions. Also some numerical studies are conducted to investigate the vibration characteristics of an example axially-traveling strip subjected to a sudden thermal loading on its upper surface.Findings: The present spectral element model is shown to provide very accurate dynamic characteristics by treating a whole uniform strip between two boundary supports as a single finite element, regardless of its length, when compared with the conventional finite element model.Practical implications: Numerical studies for the typical example problem show that the dynamic characteristics of an axially-traveling strip may depend on the traveling speed and the duration and frequency characteristics of the externally applied thermal loading.Originality/value: The spectral element model presented in this paper is the first one for the axially-traveling strips subjected to thermal loadings and is applicable to the engineering problems such as the galvanized steel strip passing through a hot zinc tank, for instance.
Biomarkers for Severity of Spinal Cord Injury in the Cerebrospinal Fluid of Rats
Joanna M. Lubieniecka,Femke Streijger,Jae H. T. Lee,Nikolay Stoynov,Jie Liu,Randy Mottus,Tom Pfeifer,Brian K. Kwon,Jens R. Coorssen,Leonard J. Foster,Thomas A. Grigliatti,Wolfram Tetzlaff
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0019247
Abstract: One of the major challenges in management of spinal cord injury (SCI) is that the assessment of injury severity is often imprecise. Identification of reliable, easily quantifiable biomarkers that delineate the severity of the initial injury and that have prognostic value for the degree of functional recovery would significantly aid the clinician in the choice of potential treatments. To find such biomarkers we performed quantitative liquid chromatography-mass spectrometry (LC-MS/MS) analyses of cerebrospinal fluid (CSF) collected from rats 24 h after either a moderate or severe SCI. We identified a panel of 42 putative biomarkers of SCI, 10 of which represent potential biomarkers of SCI severity. Three of the candidate biomarkers, Ywhaz, Itih4, and Gpx3 were also validated by Western blot in a biological replicate of the injury. The putative biomarkers identified in this study may potentially be a valuable tool in the assessment of the extent of spinal cord damage.
Nanoscale Quantum Solvation of para-H$_2$ around the Linear OCS Molecule inside $^4$He Droplets
Yongkyung Kwon,K. Birgitta Whaley
Physics , 2003, DOI: 10.1023/B:JOLT.0000012566.13979.3a
Abstract: We present a microscopic analysis of the quantum solvation structures of para-H$_2$ around the OCS molecule when embedded in low temperature $^4$He droplets. The structures of clusters containing M=5 and 6 para-H$_2$ molecules are compared with corresponding structures for M=1 (OCS-H$_2$ complex) and M=17 (a full solvation shell), as well as with the clusters in the absence of helium. We find that the helium has negligible effect on the structures for the small and large OCS(H$_2$)$_M$ clusters, but that it modifies the cluster structure for M=6. We discuss implications of these results for the onset of superfluidity in the solvating hydrogen shell and for spectroscopic measurements.
Girvin-MacDonald-Platzman Collective Mode at General Filling Factors: Magneto-Roton Minimum at Half-Filled Landau Level
Kwon Park,J. K. Jain
Physics , 1999, DOI: 10.1016/S0038-1098(00)00181-2
Abstract: The single mode approximation has proved useful for the excitation spectrum at $\nu=1/3$. We apply it to general fractions and find that it predicts $n$ magneto-roton minima in the dispersion of the Girvin-MacDonald-Platzman collective mode for the fractional quantum Hall states at $\nu=n/(2n+1)$, and one magneto-roton minimum for both the composite Fermi sea and the paired composite fermion state. Experimental relevance of the results will be considered.
Microscopic two-fluid theory of rotational constants of the OCS-H$_2$ complex in $^4$He droplets
Yongkyung Kwon,K. Birgitta Whaley
Physics , 2003, DOI: 10.1063/1.1582850
Abstract: We present a microscopic quantum analysis for rotational constants of the OCS-H$_2$ complex in helium droplets using the local two-fluid theory in conjunction with path integral Monte Carlo simulations. Rotational constants are derived from effective moments of inertia calculated assuming that motion of the H$_2$ molecule and the local non-superfluid helium density is rigidly coupled to the molecular rotation of OCS and employing path integral methods to sample the corresponding H$_2$ and helium densities. The rigid coupling assumption for H$_2$-OCS is calibrated by comparison with exact calculations of the free OCS-H$_2$ complex. The presence of the H$_2$ molecule is found to induce a small local non-superfluid helium density in the second solvation shell which makes a non-negligible contribution to the moment of inertia of the complex in helium. The resulting moments of inertia for the OCS-H$_2$ complex embedded in a cluster of 63 helium atoms are found to be in good agreement with experimentally measured values in large helium droplets. Implications for analysis of rotational constants of larger complexes of OCS with multiple H$_2$ molecules in helium are discussed.
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