D.H. Yoon

Microstructure of Y2O3 doped Al2O3/ZrO2 eutectic fibers grown by the micro-pulling-down method

Al2O3/ZrO2 eutectic crystal fibers containing various amounts of Y2O3 were grown by the micro-pulling-down method. The eutectic microstructures and some mechanical properties were investigated as a function of growth rate and doping amount of Y2O3. Doped with Y2O3, Al2O3/ZrO2 eutectic fibers 0.3–2 mm in diameter and 500 mm in length have been grown over the range of pulling rate 0.1–15 mm/min. The dominant zirconia phase was changed from monoclinic to cubic as the doping amount of Y2O3 increased. The eutectic microstructures were oriented to a common direction which depended on the growth rate and doping amount of Y2O3. The uniform lamellar structure obtained at a lower growth rate below 1 mm/min transformed to an ellipsoidal cellular structure at a growth rate above 10 mm/min, and circular or triply facetted cellular patterns were observed at intermediate growth rates. The intercellular spacing increased as the doping amount of Y2O3 increased. The hardness value reached 20 GPa for 9 mol% Y2O3 doped fibers grown at a rate of 15 mm/min. The highest tensile strength reached 2000 MPa at room temperature and 560 MPa at 1500°C for the 3 mol% Y2O3 doped fibers grown at a rate of 15 mm/min.

Phase identification of Al2O3/RE3Al5O12 and Al2O3/REAlO3 (RE = Sm-Lu, Y) eutectics

Abstract Growth of various kinds of eutectic fibers based on Al 2 O 3 and oxides of Y and rare earths from Sm to Lu using micro-pulling-down (μ-PD) method was investigated. The effect of rare-earth element substitution on growth, microstructure and mechanical properties are discussed. Eutectic materials were classified into Al 2 O 3 /garnet system and Al 2 O 3 /perovskite system types at the boundary between Gd and Tb. Al 2 O 3 /garnet eutectic fibers showed superior high-temperature strength properties. This is the first systematic study of the characteristics of these eutectic materials.

Very fast YbxY1-xAlO3 single-crystal scintillators

Scintillation, radioluminescence, photoluminescence, and thermoluminescence characteristics of Czochralski-grown YbxY1−xAlO3 single crystals for x=0.02–0.45 are described. Under x-ray excitation, the intensity of Yb3+ charge-transfer luminescence is increasing with x and reaches at room temperature more than 11% of Bi4Ge3O12 (BGO) for x=0.45, while at 80 K it is over 170% of BGO for x⩾0.3. At room temperature, scintillation decay shows a dominant decay time of 0.8–0.9 ns for x⩾0.3 and no significant slow components were detected. The photoluminescence decay time is tuned by temperature and Yb concentration from tens of nanoseconds at 80 K down to about 0.8 ns at 295 K. Thermoluminescence glow curve below room temperature evidences very low concentration of shallow traps compared to the Ce-doped YAlO3 scintillator.

Lead generation of heat shock protein 90 inhibitors by a combination of fragment-based approach, virtual screening, and structure-based drug design

Heat shock protein 90 (Hsp90) is a molecular chaperone which regulates maturation and stabilization of its substrate proteins, known as client proteins. Many client proteins of Hsp90 are involved in tumor progression and survival and therefore Hsp90 can be a good target for developing anticancer drugs. With the aim of efficiently identifying a new class of orally available inhibitors of the ATP binding site of this protein, we conducted fragment screening and virtual screening in parallel against Hsp90. This approach quickly identified 2-aminotriazine and 2-aminopyrimidine derivatives as specific ligands to Hsp90 with high ligand efficiency. In silico evaluation of the 3D X-ray Hsp90 complex structures of the identified hits allowed us to promptly design CH5015765, which showed high affinity for Hsp90 and antitumor activity in human cancer xenograft mouse models.

High aspect ratio via etching conditions for deep trench of silicon

Abstract Deep trench etching of silicon was investigated as a function of platen power, operational pressure and the SF6:C4F8 gas flow rate. Their effects on the etch rate, etch profile and scallops were also studied. As the platen power was increased from 5 to 30 W, the etch rate was increased from 0.54 to 2.51 μm/min. However, the etch rate was decreased at platen power higher than 30 W. As the pressure was increased from 10 to 25 mTorr, the etch rate was increased from 1.93 to 2.69 μm/min but the etch rate was decreased at the pressure higher than 35 mTorr. As the SF6:C4F8 gas flow rate was increased from 50:50 to 200:160 sccm, the etch rate was increased from 1.91 to 2.31 μm/min and at the SF6:C4F8 gas flow rate of 260:220 sccm, it was decreased to 2.21 μm/min.

Influence of hydrogen on SiON thick film for silica waveguide deposited by PECVD and annealing effect

Abstract Silicon oxynitride (SiON) films containing various hydrogen concentrations were deposited in a plasma enhanced chemical vapor deposition (PECVD) reactor using SiH 4 and N 2 O as precursor gases. In this work, the influence of annealing temperature on the optical and physical properties of SiON films is presented. It can be seen that the refractive index for the as-deposited SiON and annealed SiON films can be varied continuously between 1.4554 and 1.4513 at a wavelength of 1552 nm by using a prism coupler. The silicon content of the films is independent of the annealing temperature and for all layers it is approximately 33%. As annealing temperature increased, the oxygen content of the films increased from 64 to 66.2%, and the nitrogen content decreased from 1.98 to 0.02%.

Luminescence, radiation damage, and color center creation in Eu3+-doped Bi4Ge3O12 fiber single crystals

Doped Bi4Ge3O12 (BGO) fiber single crystals were grown by the micro-pulling-down method with the resistance heating system. Optical absorption measurements before and after x-ray irradiation (induced absorption) were performed in order to investigate the radiation damage of the crystals. The Eu3+-doped BGO has shown higher radiation resistance with respect to the equivalently grown undoped BGO fibers. Radio- and photoluminescence characteristics were obtained to clarify the role of Eu3+ in luminescence and scintillation mechanism. Radioluminescence spectra show the intense and slow (decay time of 1.61 ms) 5D0,1−7Fx(x=0−6) radiative transitions of Eu3+, while the intrinsic BGO emission becomes weaker with respect to the undoped BGO. Photoluminescence decay of the intrinsic BGO emission becomes nonexponential and noticeably faster in Eu-doped samples, which evidences the nonradiative energy transfer from intrinsic emission centers to Eu3+ ions. Thermally stimulated luminescence (TSL) measurements above room...

Design and synthesis of 2-amino-6-(1H,3H-benzo[de]isochromen-6-yl)-1,3,5-triazines as novel Hsp90 inhibitors.

A novel series of 2-amino-1,3,5-triazines bearing a tricyclic moiety as heat shock protein 90 (Hsp90) inhibitors is described. Molecular design was performed using X-ray cocrystal structures of the lead compound CH5015765 and natural Hsp90 inhibitor geldanamycin with Hsp90. We optimized affinity to Hsp90, in vitro cell growth inhibitory activity, water solubility, and liver microsomal stability of inhibitors and identified CH5138303. This compound showed high binding affinity for N-terminal Hsp90α (Kd=0.52nM) and strong in vitro cell growth inhibition against human cancer cell lines (HCT116 IC50=0.098μM, NCI-N87 IC50=0.066μM) and also displayed high oral bioavailability in mice (F=44.0%) and potent antitumor efficacy in a human NCI-N87 gastric cancer xenograft model (tumor growth inhibition=136%).

N2 doped SiO2–SiON planar waveguides deposited by PECVD method

Abstract Silica based planar lightwave circuits (PLCs) have been applied to various kinds of wave-guided optical passive devices. Silicon dioxide (SiO2) and silicon oxynitride (SiON) thick films have been deposited by plasma enhanced chemical vapor deposition (PECVD). SiO2 and SiON films were obtained at low temperatures (

Optical Properties of Er Doped Congruent and Stoichiometric LiNbO3 Single Crystals

Erbium doped LiNbO 3 (Er:LiNbO 3 ) single crystal fibers were grown free of cracks along c-axis by the micro-pulling down (μ-PD) method. We have investigated the up-conversion property with the change of doped Er 2 O 3 concentration and the starting melt composition. An enhancement of green up-conversion according host matrix is also observed the stoichiometric LiNbO 3 . And, the dependence of the green emission according to Er 3+ concentration is analyzed. The possible application of the Er 3+ doped stoichiometric LiNbO 3 single crystal fiber for up-conversion based optical devices is discussed.