oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2017 ( 1 )

2015 ( 13 )

2014 ( 11 )

2013 ( 21 )

Custom range...

Search Results: 1 - 10 of 156 matches for " Korine Ung "
All listed articles are free for downloading (OA Articles)
Page 1 /156
Display every page Item
Evidence of a Large Novel Gene Pool Associated with Prokaryotic Genomic Islands
William W. L Hsiao,Korine Ung,Dana Aeschliman,Jenny Bryan,B. Brett Finlay,Fiona S. L Brinkman
PLOS Genetics , 2005, DOI: 10.1371/journal.pgen.0010062
Abstract: Microbial genes that are “novel” (no detectable homologs in other species) have become of increasing interest as environmental sampling suggests that there are many more such novel genes in yet-to-be-cultured microorganisms. By analyzing known microbial genomic islands and prophages, we developed criteria for systematic identification of putative genomic islands (clusters of genes of probable horizontal origin in a prokaryotic genome) in 63 prokaryotic genomes, and then characterized the distribution of novel genes and other features. All but a few of the genomes examined contained significantly higher proportions of novel genes in their predicted genomic islands compared with the rest of their genome (Paired t test = 4.43E-14 to 1.27E-18, depending on method). Moreover, the reverse observation (i.e., higher proportions of novel genes outside of islands) never reached statistical significance in any organism examined. We show that this higher proportion of novel genes in predicted genomic islands is not due to less accurate gene prediction in genomic island regions, but likely reflects a genuine increase in novel genes in these regions for both bacteria and archaea. This represents the first comprehensive analysis of novel genes in prokaryotic genomic islands and provides clues regarding the origin of novel genes. Our collective results imply that there are different gene pools associated with recently horizontally transmitted genomic regions versus regions that are primarily vertically inherited. Moreover, there are more novel genes within the gene pool associated with genomic islands. Since genomic islands are frequently associated with a particular microbial adaptation, such as antibiotic resistance, pathogen virulence, or metal resistance, this suggests that microbes may have access to a larger “arsenal” of novel genes for adaptation than previously thought.
Canopy Net Photosynthesis Rate of a Mongolian Oak (Quercus mongolica) Forest Estimated by Field Experimental Data  [PDF]
Seung Jin Joo, Soon-Ung Park
American Journal of Plant Sciences (AJPS) , 2017, DOI: 10.4236/ajps.2017.83027
Abstract: The canopy net photosynthesis rate of Mongolian oak (Quercus mongolica) tree species that are dominant in East Asia and Korea is estimated with empirical models derived from field experimental data obtained from the Nam-San site in Seoul, Korea for the growing period from early May to late October in 2010. The empirical models include the attenuation function of photosynthetic photon flux density (PPFD) (r2 = 0.98-0.99, p < 0.001) and the photosynthetic light response function (r2 = 0.99, p < 0.001) derived from the measured data at several levels within the canopy. The incident PPFD at each level within canopy significantly varies diurnally and seasonally due to the seasonal variation of the total plant area index (TPAI = leaf area index + wood silhouette area index) and the light shielding effect of light path-length through the canopy in association with the variation of solar elevation angle. Consequently, a remarkable seasonal variation of the total canopy net photosynthesis rate of Q. mongolica forest stand is found for its growing period. The PPFD exceeding 1000 μmol m-2·s-1 is found to cause the decrease of net photosynthesis rate due to the thermal stress in the early (May) and late (September) growing period. During the whole growing season, the estimated total canopy net photosynthesis rate is found to be about 3.3 kg CO2
Evidence of a Large Novel Gene Pool Associated with Prokaryotic Genomic Islands.
Hsiao,Ung,Aeschliman,Bryan
PLOS Genetics , 2005,
Abstract: Microbial genes that are "novel" (no detectable homologs in other species) have become of increasing interest as environmental sampling suggests that there are many more such novel genes in yet-to-be-cultured microorganisms. By analyzing known microbial genomic islands and prophages, we developed criteria for systematic identification of putative genomic islands (clusters of genes of probable horizontal origin in a prokaryotic genome) in 63 prokaryotic genomes, and then characterized the distribution of novel genes and other features. All but a few of the genomes examined contained significantly higher proportions of novel genes in their predicted genomic islands compared with the rest of their genome (Paired t test = 4.43E-14 to 1.27E-18, depending on method). Moreover, the reverse observation (i.e., higher proportions of novel genes outside of islands) never reached statistical significance in any organism examined. We show that this higher proportion of novel genes in predicted genomic islands is not due to less accurate gene prediction in genomic island regions, but likely reflects a genuine increase in novel genes in these regions for both bacteria and archaea. This represents the first comprehensive analysis of novel genes in prokaryotic genomic islands and provides clues regarding the origin of novel genes. Our collective results imply that there are different gene pools associated with recently horizontally transmitted genomic regions versus regions that are primarily vertically inherited. Moreover, there are more novel genes within the gene pool associated with genomic islands. Since genomic islands are frequently associated with a particular microbial adaptation, such as antibiotic resistance, pathogen virulence, or metal resistance, this suggests that microbes may have access to a larger "arsenal" of novel genes for adaptation than previously thought.
Holographic Chiral Magnetic Conductivity
Ho-Ung Yee
Physics , 2009, DOI: 10.1088/1126-6708/2009/11/085
Abstract: We present holographic computations of the time-dependent chiral magnetic conductivity in the framework of gauge/gravity correspondence. Chiral magnetic effect is a phenomenon where an electromagnetic current parallel to an applied magnetic field is induced in the presence of a finite axial chemical potential. Motivated by a recent weak-coupling perturbative QCD calculation, our aim is to provide a couple of complementary computations for strongly coupled regime which might be relevant for strongly coupled RHIC plasma. We take two prototypical holographic set-ups for computing chiral magnetic conductivity; the first model is Einstein gravity with U(1)_L X U(1)_R Maxwell theory, and our second set-up is based on the Sakai-Sugimoto model in a deconfined and chiral symmetry restored phase. While the former takes into account full back-reaction while the latter not, the common feature is an important role played by the appropriate 5-dimensional Chern-Simons term corresponding to the 4-dimensional axial anomaly.
Parity asymmetric boost invariant plasma in AdS/CFT correspondence
Ho-Ung Yee
Physics , 2009, DOI: 10.1016/j.physletb.2009.08.069
Abstract: We consider a simple extension to the previously found gravity solution corresponding to a boost invariant Bjorken plasma, by allowing components that are asymmetric under parity flipping of the spacetime rapidity. Besides the question whether this may have a realization in collisions of different species of projectiles, such as lead-gold collision, our new time dependent gravity background can serve as a test ground for the recently proposed second order conformal viscous hydrodynamics. We find that non-trivial parity-asymmetric effects start to appear at second order in late time expansion, and we map the corresponding energy-momentum tensor to the second order conformal hydrodynamics to find certain second order transport coefficients. Our results are in agreement with the previous results in literature, giving one more corroborative evidence for the validity of the framework.
Optical surface waves over metallo-dielectric nanostructures: Sommerfeld integrals revisited
Bora Ung,Yunlong Sheng
Physics , 2008, DOI: 10.1364/OE.16.009073
Abstract: The asymptotic closed-form solution to the fundamental diffraction problem of a linear horizontal Hertzian dipole radiating over the metallo-dielectric interface is provided. For observation points just above the interface, we confirm that the total surface near-field is the sum of two components: a long-range surface plasmon polariton and a short-range radiative cylindrical wave. The relative phases, amplitudes and damping functions of each component are quantitatively elucidated through simple analytic expressions for the entire range of propagation: near and asymptotic. Validation of the analytic solution is performed by comparing the predictions of a dipolar model with recently published data
Fate of Z(N) walls in hot holographic QCD
Ho-Ung Yee
Physics , 2009, DOI: 10.1088/1126-6708/2009/04/029
Abstract: We first study Z(N) walls in a deconfined phase of Witten's D4-brane background of pure SU(N) Yang-Mills theory, motivated by a recent work in the case of N=4 SYM. Similarly to it, we propose that for a large wall charge k ~ N, it is described by k D2-branes blown up into a NS5-brane wrapping S^3 inside S^4 via Myers effect, and we calculate the tension by suitable U-duality. We find a precise Casimir scaling for the tension formula. We then study the fate of Z(N)-vacua in a presence of fundamental flavors in quenched approximation via gauge/gravity correspondence. In the case of D3/D7 system where one can vary the mass m_q of flavors, we show that there is a phase transition at T_c ~ m_q, below which the Z(N)-vacua survive while they are lifted above the critical temperature. We analytically calculate the energy lift of k'th vacua in the massless case, both in the D3/D7 system and in the Sakai-Sugimoto model.
Extreme nonlinear optical enhancement in chalcogenide glass fibers with deep-subwavelength metallic nanowires
Bora Ung,Maksim Skorobogatiy
Physics , 2011, DOI: 10.1364/OL.36.002527
Abstract: A nanostructured chalcogenide-metal optical fiber is proposed. This hybrid nanofiber is embedded with a periodic array of triangular-shaped deep-subwavelength metallic nanowires set up in a bowtie configuration. Our simulations show that the proposed nanostructured fiber supports a guided collective plasmonic mode enabling both subwavelength field confinement and extreme nonlinear light- matter interactions, much larger than a bare chalcogenide nanowire of comparable diameter. This is all achieved with less than 3% by volume of metal content.
Recent Theoretical Developments in Strongly Coupled QCD
Ho-Ung Yee
Physics , 2012, DOI: 10.1016/j.nuclphysa.2013.01.077
Abstract: Heavy-ion collisions involve strongly coupled dynamics of QCD in the entire history of time evolution. We review recent theoretical efforts to meet this challenge, focusing on the two approaches that the speaker has contributed to: 1) Holography or AdS/CFT correspondence, and 2) Symmetry protected phenomena such as those originating from triangle anomaly. The presentation is oriented to non-experts on these fields, and hence relies on intuitive pictures of the methods and the results, without going into specific details.
Flows and polarization of early photons with magnetic field at strong coupling
Ho-Ung Yee
Physics , 2013, DOI: 10.1103/PhysRevD.88.026001
Abstract: Recent experimental results from RHIC and LHC on hard photon emission rates in heavy-ion collisions indicate a large azimuthal asymmetry of photon emission rate parameterized by the elliptic flow v_2. Motivated by a recent proposal that the early magnetic field created by two colliding heavy-ions may be responsible for this large azimuthal asymmetry of photon emission rate, we compute the azimuthal dependence of the photon emission rate from a strongly coupled finite temperature plasma with magnetic field in the framework of gauge/gravity correspondence. We also propose and compute a new observable, "in/out-plane polarization asymmetry", constructed from the polarization dependence of the photon emission rates. We observe that both the azimuthal and polarization asymmetry of photon emissions are strongly affected by the triangle anomaly (chiral anomaly) for low frequency regime below 1 GeV.
Page 1 /156
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.