Kaons in Dense Half-Skyrmion Matter

Dense hadronic matter at low temperature is expected to be in crystal and at high density make a transition to a {\em chirally restored but color-confined} state which is a novel phase hitherto unexplored. This phase transition is predicted in both skyrmion matter in 4D and instanton matter in 5D, the former in the form of half-skyrmions and the latter in the form of half-instantons or dyons. We predict that when $K^-$'s are embedded in this half-skyrmion or half-instanton (dyonic) matter which may be reached not far above the normal density, there arises an enhanced attraction from the soft dilaton field figuring for the trace anomaly of QCD and the Wess-Zumino term. This attraction may have relevance for a possible strong binding of anti-kaons in dense nuclear matter and for kaon condensation in neutron-star matter. Such kaon property in the half-skyrmion phase is highly non-perturbarive and may not be accessible by low-order chiral perturbation theory. Relevance of the half-skyrmion or dyonic matter to compact stars is discussed.Comment: 5 pages, 2 figure

Stent Application for the Treatment of Cerebral Aneurysms

Rapid and striking development in both the techniques and devices make it possible to treat most of cerebral aneurysms endovascularly. Stent has become one of the most important tools in treating difficult aneurysms not feasible for simple coiling. The physical features, the dimensions, and the functional characteristics of the stents show considerable differences. There are also several strategies and tips to treat difficult aneurysms by using stent and coiling. Nevertheless, they require much experience in clinical practice as well as knowledge of the stents to treat cerebral aneurysms safely and effectively. In this report, a brief review of properties of the currently available stents and strategies of their application is presented

Production of biohydrogen by recombinant expression of [NiFe]-hydrogenase 1 in Escherichia coli

<p>Abstract</p> <p>Background</p> <p>Hydrogenases catalyze reversible reaction between hydrogen (H₂) and proton. Inactivation of hydrogenase by exposure to oxygen is a critical limitation in biohydrogen production since strict anaerobic conditions are required. While [FeFe]-hydrogenases are irreversibly inactivated by oxygen, it was known that [NiFe]-hydrogenases are generally more tolerant to oxygen. The physiological function of [NiFe]-hydrogenase 1 is still ambiguous. We herein investigated the H₂production potential of [NiFe]-hydrogenase 1 of <it>Escherichia coli in vivo </it>and <it>in vitro</it>. The <it>hya</it>A and <it>hya</it>B genes corresponding to the small and large subunits of [NiFe]-hydrogenase 1 core enzyme, respectively, were expressed in BL21, an <it>E. coli </it>strain without H₂producing ability.</p> <p>Results</p> <p>Recombinant BL21 expressing [NiFe]-hydrogenase 1 actively produced H₂(12.5 mL H₂/(h·L) in 400 mL glucose minimal medium under micro-aerobic condition, whereas the wild type BL21 did not produce H₂even when formate was added as substrate for formate hydrogenlyase (FHL) pathway. The majority of recombinant protein was produced as an insoluble form, with translocation of a small fraction to the membrane. However, the membrane fraction displayed high activity (~65% of total cell fraction), based on unit protein mass. Supplement of nickel and iron to media showed these metals contribute essentially to the function of [NiFe]-hydrogenase 1 as components of catalytic site. In addition, purified <it>E. coli </it>[NiFe]-hydrogenase 1 using his₆-tag displayed oxygen-tolerant activity of ~12 nmol H₂/(min·mg protein) under a normal aeration environment, compared to [FeFe]-hydrogenase, which remains inactive under this condition.</p> <p>Conclusions</p> <p>This is the first report on physiological function of <it>E. coli </it>[NiFe]-hydrogenase 1 for H₂production. We found that [NiFe]-hydrogenase 1 has H₂production ability even under the existence of oxygen. This oxygen-tolerant property is a significant advantage because it is not necessary to protect the H₂production process from oxygen. Therefore, we propose that [NiFe]-hydrogenase can be successfully applied as an efficient biohydrogen production tool under micro-aerobic conditions.</p

Discrete Adjoint Approach for Aerodynamic Sensitivity Analysis and Shape Optimization on Overset Mesh System

In the present talk, the strategies to apply the sensitivity analysis method to aerodynamic shape optimization problems of complex geometries are intensively discussed. To resolve the design of complicated aircraft geometries such as high-lift devices, wing/body configurations, overset mesh techniques are adopted. In addition, a noticeable sensitivity analysis method, adjoint approach, which shows very good efficiency and accuracy for aerodynamic design problems, is also introduced. For the incorporation of the adjoint method into the overset mesh system, adjoint formulations are derived for the overset boundary conditions based on linear interpolation. The feasibility of non-conservative adjoint overset boundary conditions for external flow applications is carefully investigated by comparison with a single block design result for the same geometry. Through the several design application problems for realistic aircraft geometries, the present design framework demonstrates its capability and applicability for aerodynamic design of complex geometries.This work was supported by the second stage of the Brain Korea 21 Project in 2008

Topological Structure of Dense Hadronic Matter

We present a summary of work done on dense hadronic matter, based on the Skyrme model, which provides a unified approach to high density, valid in the large $N_c$ limit. In our picture, dense hadronic matter is described by the {\em classical} soliton configuration with minimum energy for the given baryon number density. By incorporating the meson fluctuations on such ground state we obtain an effective Lagrangian for meson dynamics in a dense medium. Our starting point has been the Skyrme model defined in terms of pions, thereafter we have extended and improved the model by incorporating other degrees of freedom such as dilaton, kaons and vector mesons.Comment: 13 pages, 8 figures, Talk given at the KIAS-APCTP Symposium in Astro-Hadron Physics "Compact Stars: Quest for New States of Dense Matter", November 10-14, 2003, Seoul, Korea, published by World Scientific. Based on talk by B.-Y. Par

Improved production of biohydrogen in light-powered Escherichia coli by co-expression of proteorhodopsin and heterologous hydrogenase

<p>Abstract</p> <p>Background</p> <p>Solar energy is the ultimate energy source on the Earth. The conversion of solar energy into fuels and energy sources can be an ideal solution to address energy problems. The recent discovery of proteorhodopsin in uncultured marine γ-proteobacteria has made it possible to construct recombinant <it>Escherichia coli </it>with the function of light-driven proton pumps. Protons that translocate across membranes by proteorhodopsin generate a proton motive force for ATP synthesis by ATPase. Excess protons can also be substrates for hydrogen (H₂) production by hydrogenase in the periplasmic space. In the present work, we investigated the effect of the co-expression of proteorhodopsin and hydrogenase on H₂production yield under light conditions.</p> <p>Results</p> <p>Recombinant <it>E. coli </it>BL21(DE3) co-expressing proteorhodopsin and [NiFe]-hydrogenase from <it>Hydrogenovibrio marinus </it>produced ~1.3-fold more H₂in the presence of exogenous retinal than in the absence of retinal under light conditions (70 μmole photon/(m²·s)). We also observed the synergistic effect of proteorhodopsin with endogenous retinal on H₂production (~1.3-fold more) with a dual plasmid system compared to the strain with a single plasmid for the sole expression of hydrogenase. The increase of light intensity from 70 to 130 μmole photon/(m²·s) led to an increase (~1.8-fold) in H₂production from 287.3 to 525.7 mL H₂/L-culture in the culture of recombinant <it>E. coli </it>co-expressing hydrogenase and proteorhodopsin in conjunction with endogenous retinal. The conversion efficiency of light energy to H₂achieved in this study was ~3.4%.</p> <p>Conclusion</p> <p>Here, we report for the first time the potential application of proteorhodopsin for the production of biohydrogen, a promising alternative fuel. We showed that H₂production was enhanced by the co-expression of proteorhodopsin and [NiFe]-hydrogenase in recombinant <it>E. coli </it>BL21(DE3) in a light intensity-dependent manner. These results demonstrate that <it>E. coli </it>can be applied as light-powered cell factories for biohydrogen production by introducing proteorhodopsin.</p

Physical properties of transparent perovskite oxides (Ba,La)SnO3 with high electrical mobility at room temperature

Transparent electronic materials are increasingly in demand for a variety of optoelectronic applications. BaSnO3 is a semiconducting oxide with a large band gap of more than 3.1 eV. Recently, we discovered that La doped BaSnO3 exhibits unusually high electrical mobility of 320 cm^2(Vs)^-1 at room temperature and superior thermal stability at high temperatures [H. J. Kim et al. Appl. Phys. Express. 5, 061102 (2012)]. Following that work, we report various physical properties of (Ba,La)SnO3 single crystals and films including temperature-dependent transport and phonon properties, optical properties and first-principles calculations. We find that almost doping-independent mobility of 200-300 cm^2(Vs)^-1 is realized in the single crystals in a broad doping range from 1.0x10^19 to 4.0x10^20 cm^-3. Moreover, the conductivity of ~10^4 ohm^-1cm^-1 reached at the latter carrier density is comparable to the highest value. We attribute the high mobility to several physical properties of (Ba,La)SnO3: a small effective mass coming from the ideal Sn-O-Sn bonding, small disorder effects due to the doping away from the SnO2 conduction channel, and reduced carrier scattering due to the high dielectric constant. The observation of a reduced mobility of ~70 cm^2(Vs)^-1 in the film is mainly attributed to additional carrier-scatterings which are presumably created by the lattice mismatch between the substrate SrTiO3 and (Ba,La)SnO3. The main optical gap of (Ba,La)SnO3 single crystals remained at about 3.33 eV and the in-gap states only slightly increased, thus maintaining optical transparency in the visible region. Based on these, we suggest that the doped BaSnO3 system holds great potential for realizing all perovskite-based, transparent high-frequency high-power functional devices as well as highly mobile two-dimensional electron gas via interface control of heterostructured films.Comment: 31 pages, 7 figure