Jin-Won Lee

Identification and functional analysis of light-responsive unique genes and gene family members in rice.

Functional redundancy limits detailed analysis of genes in many organisms. Here, we report a method to efficiently overcome this obstacle by combining gene expression data with analysis of gene-indexed mutants. Using a rice NSF45K oligo-microarray to compare 2-week-old light- and dark-grown rice leaf tissue, we identified 365 genes that showed significant 8-fold or greater induction in the light relative to dark conditions. We then screened collections of rice T-DNA insertional mutants to identify rice lines with mutations in the strongly light-induced genes. From this analysis, we identified 74 different lines comprising two independent mutant lines for each of 37 light-induced genes. This list was further refined by mining gene expression data to exclude genes that had potential functional redundancy due to co-expressed family members (12 genes) and genes that had inconsistent light responses across other publicly available microarray datasets (five genes). We next characterized the phenotypes of rice lines carrying mutations in ten of the remaining candidate genes and then carried out co-expression analysis associated with these genes. This analysis effectively provided candidate functions for two genes of previously unknown function and for one gene not directly linked to the tested biochemical pathways. These data demonstrate the efficiency of combining gene family-based expression profiles with analyses of insertional mutants to identify novel genes and their functions, even among members of multi-gene families.

Mutations in the rice liguleless gene result in a complete loss of the auricle, ligule, and laminar joint

The area between the upper part of the leaf sheath and the basal portion of the leaf blade contains several specialized organs, such as the laminar joint, auricle and ligule. Here we report the identification of T-DNA insertional mutant lines that lack all of these organs. The gene knocked out in the mutant lines encodes a protein that contains a SBP (SQUAMOSA promoter Binding Protein)-domain and is highly homologous to the maize LIGULELESS1 (LG1) gene. At the amino acid sequence level, the OsLG1 protein is 69% identical to maize LG1 and 78% identical to barley LG1. We named the rice gene OsLIGULELESS1 (OsLG1). Transient expression of an OsLG1:RFP (Red Fluorescent Protein) fusion protein indicated that the protein is localized to the nucleus. Transgenic plants harboring the OsLG1 promoter:GUS (β-glucuronidase) reporter gene construct display preferential expression in developing laminar joint regions and meristemic regions. The gene is also weakly expressed in the ligule, auricles, and leaf sheaths at the basal region. These results indicate that OsLG1 is a transcriptional factor that plays an important role in building the laminar joint between leaf blade and leaf sheath boundary, thereby controlling ligule and auricle development.

Stochastic simulation of particle charging and collection characteristics for a wire-plate electrostatic precipitator of short length

Abstract In order to estimate more exactly the performance of wire-plate electrostatic precipitators (ESP), a new computational scheme has been developed, where the involved physical phenomena such as corona-field, turbulent electrohydrodynamic (EHD) flow field, in situ particle charging and turbulent motion of particles are treated simultaneously. To overcome the deficiencies of the Eulerian method used up to now, a Lagrangian particle-tracking method coupled with the Monte-Carlo method for simulating the stochastic nature of turbulence is used. The scheme is applied to the analysis of an experimental wire-plate ESP of short length (Kihm, Ph.D. thesis, Stanford University, Stanford, 1987), where the effect of developing flow in the entrance region is substantial. The simulation results for two different flow conditions of high and low turbulent intensity at the inlet clearly reproduced the steeper increase of efficiency with voltage for low turbulence case observed in the experiment, and also the efficiency values agree very well with the experimental data for one particle size of 4 μm.

Inertial focusing of particles with an aerodynamic lens in the atmospheric pressure range

The performance of an aerodynamic lens operating at atmospheric pressure is analyzed numerically, and the results are verified through experiments measuring the particle beam size by laser light scattering. It is shown that a strongly focused particle beam is obtainable with a single orifice at atmospheric pressure, when the orifice Reynolds number is in the range 300 ≤ Re ≤ 700. Two different orifice sizes, d/D = 0.1 and 0.2, and particle sizes of 1-10 μm are studied with the Stokes number in the range 0.01 < St < 3.0. The smaller beam can be generated with the smaller orifice, but the concentration factors for different orifice sizes overlap giving a universal curve, when plotted versus Stokes number. Experimental results are in a very good agreement with numerical results.

Removal of 10-nm contaminant particles from Si wafers using CO2 bullet particles

Removal of nanometer-sized contaminant particles (CPs) from substrates is essential in successful fabrication of nanoscale devices. The particle beam technique that uses nanometer-sized bullet particles (BPs) moving at supersonic velocity was improved by operating it at room temperature to achieve higher velocity and size uniformity of BPs and was successfully used to remove CPs as small as 10 nm. CO2 BPs were generated by gas-phase nucleation and growth in a supersonic nozzle; appropriate size and velocity of the BPs were obtained by optimizing the nozzle contours and CO2/He mixture fraction. Cleaning efficiency greater than 95% was attained. BP velocity was the most important parameter affecting removal of CPs in the 10-nm size range. Compared to cryogenic Ar or N2 particles, CO2 BPs were more uniform in size and had higher velocity and, therefore, cleaned CPs more effectively.

Effect of geometric variations on pressure loss for a model bifurcation of the human lung airway

Characteristics of pressure loss (ΔP) in human lung airways were numerically investigated using a realistic model bifurcation. Flow equations were numerically solved for the steady inspiratory condition with the tube length, the branching angle and flow velocity being varied over a wide range. In general, the ΔP coefficient K showed a power-law dependence on Reynolds number (Re) and length-to-diameter ratio with a different exponent for Re≥100 than for Re<100. The effect of different branching angles on pressure loss was very weak in the smooth-branching airways.

Numerical Simulation of Laser Shock Cleaning Process for Micro-Scale Particle Removal

Recent studies have demonstrated that micro/nano-scale particles can be removed effectively from solid surfaces by laser-induced plasma shockwaves. This work proposes a two-dimensional theoretical model for numerical simulation of the hydrodynamics and particle behavior in the laser shock cleaning process. The spatial variation of the cleaning efficiency on the surface and the pressure/temperature/velocity fields are analyzed by numerical simulation. Furthermore, the model predicts the trajectory of the detached particles after the shockwave passage. Parametric studies are conducted to examine the effect of such process parameters as the laser pulse energy and the spot size on the cleaning process, with discussion of optimal cleaning conditions.

Gas-phase removal of biofilms from various surfaces using carbon dioxide aerosols

The present study evaluated the removal of Escherichia coli XL1-blue biofilms using periodic jets of carbon dioxide aerosols (a mixture of solid and gaseous CO2) with nitrogen gas. The aerosols were generated by the adiabatic expansion of high-pressure CO2 gas through a nozzle and used to remove air-dried biofilms. The areas of the biofilms were measured from scanning electron micrographs before and after applying the aerosols. The removal efficiency of the aerosol treatment was measured with various air-drying times of the biofilms before the treatment, surface materials, and durations of CO2 aerosols in each 8-s aerosol–nitrogen cleaning cycle. Nearly 100% of the fresh biofilms were removed from the various surfaces very reliably within 90 s. This technique can be useful for removing unsaturated biofilms on solid surfaces and has potential applications for cleaning bio-contaminated surfaces.

Small‐angle neutron scattering study of the miscibility of metallocene‐catalyzed octene linear low‐density polyethylene and low‐density polyethylene blends

Small-angle neutron scattering (SANS) analysis was performed to investigate the miscibility of blends of metallocene-catalyzed octene linear low-density polyethylene (octene-mLLDPE) and low-density polyethylene (LDPE). The quantitative SANS analysis found that the blends are miscible in both the melt and the quenched states. Moreover, this analysis confirmed that the radii of gyration of octene-mLLDPE(D) and LDPE(H) remain unchanged in the quenched state and that the two polymer components cocrystallize via fast crystallization from the melt state.

Removing 20 nm Particles Using a Supersonic Argon Particle Beam Generated with a Contoured Laval Nozzle

A cryogenic particle beam is an effective means of removing nano-sized contaminant particles, but the particle beam generated with a simple-hole nozzle has not been successful in removing particles smaller than 30 nm. Based on molecular dynamics (MD) simulation results that smaller cryogenic particles moving at a higher velocity are more effective in removing contaminant particles in the 10 nm range, a contoured Laval nozzle of a particular expansion angle and length was used in this study, instead of the simple-hole nozzle, to generate particle beams of high intensity and controlled size moving at high velocities. A variety of particle size and velocity were obtained by controlling the stagnation pressure/temperature and the back pressure, and using Laval nozzles with differing throat sizes and expansion angles. The new particle beams could remove almost completely a variety of ceramic and Cu particles, down to 20 nm size range, on a flat surface or in trenches.