High-power 2.8 W blue-violet laser diode for white light sources

High-power 2.8 W blue-violet InGaN LD was fabricated, applying AlN facet coating technology. The AlN was found to be crystallized on the facets and very stable even after 2200 h cw operation. Luminous flux over 380 lm is obtained with a phosphor-converted LD excitation white light source using just a single laser chip at 1A operating current.     

Generation of single-crystalline domain in nano-scale silicon pillars by near-field short pulsed laser

We observe laser-induced grain morphology change in silicon nanopillars under a transmission electron microscopy (TEM) environment. We couple the TEM with a near-field scanning optical microscopy pulsed laser processing system. This novel combination enables immediate scrutiny on the grain morphologies that the pulsed laser irradiation produces. We find unusual transformation of the tip of the amorphous or polycrystalline silicon pillar into a single crystalline domain via melt-mediated crystallization. On the basis of the three-dimensional finite difference simulation result and the dark field TEM data, we propose that the creation of the distinct single crystalline tip originates from the dominant grain growth initiated at the apex of the non-planar liquid–solid interface. Our microscopic observation provides a fundamental basis for laser-induced conversion of amorphous nanostructures into coarse-grained crystals.     

Interactive Phenomena of a Rotating Arc and a Premixed CH4 Flame

The interactive phenomena between a rotating arc and a premixed methane/air flame have been investigated. The effects of the rotating arc on the flame were observed: both lean and rich flammability limit was extended with the rotating arc on. More interestingly, the opposite interactions, i.e., the effects of the flame on the rotating arc, were also observed: the arc length, angular speed, and electrical characteristics are affected by the flame. An analysis of the optical emission spectra showed that the rotating arc generates chemically active species such as excited N₂ molecules and O and H atoms. An analysis of the gas products indicated that the concentrations of the major gas products such as CO₂, CO, and H₂ were not significantly affected by the rotating arc, although the flammability limit are significantly extended. Unlike these major gas products, minor products like NO_x emissions increased by an order of magnitude in the presence of a rotating arc under certain air/fuel conditions.     

Real‐Time Measurement of the Size Distribution of Diesel Exhaust Particles using a Portable 4‐stage Electrical Low Pressure Impactor

For this study, a 4 stage electrical low pressure impactor was designed to measure the real‐time size distribution of diesel particulate matter (DPM). For the performance evaluation, sodium chloride (NaCl) particles and dioctyl sebacate (DOS) particles were used. After evaluating the collection efficiency of each stage of the impactor, the size distributions of test particles were estimated using electrical current data and their inversion algorithm, and this was found to agree with the results obtained by a scanning mobility particle sizer (SMPS). For measurement of DPM, a common‐rail direct injection (CRDI) diesel engine, for engine speeds of 1,200 rpm and 1,500 rpm at 2.7 kgf·m, was used. Therefore, it was found that the size distribution of the DPM could be easily obtained, with the currents measured by the impactor and the data inversion algorithm, in less than 5 seconds. Furthermore, the effective density of the DPM could be obtained using the calculated results and the SMPS data.     

Side-lobeless far-field spectrum of a short pulse from a circular aperture with Gaussian form of transmittance

The spectrum change of a Gaussian pulse in the far field is studied with the Fresnel diffraction integral when it is incident on an aperture with Gaussian form transmittance. It is found that the side-lobes of the diffracted spectral intensity, which exist in a normal circular aperture with unit transmittance, can be eliminated completely under such a condition. Also, the red shift and blue shift of the spectral intensity maximum of the incident pulse are presented.     

The application of an in situ karyotyping technique for mesenchymal stromal cells: a validation and comparison study with classical G-banding

The cytogenetic analysis of mesenchymal stromal cells (MSCs) is essential for verifying the safety and stability of MSCs. An in situ technique, which uses cells grown on coverslips for karyotyping and minimizes cell manipulation, is the standard protocol for the chromosome analysis of amniotic fluids. Therefore, we applied the in situ karyotyping technique in MSCs and compared the quality of metaphases and karyotyping results with classical G-banding and chromosomal abnormalities with fluorescence in situ hybridization (FISH). Human adipose- and umbilical cord-derived MSC cell lines (American Type Culture Collection PCS-500-011, PCS-500-010) were used for evaluation. The quality of metaphases was assessed by analyzing the chromosome numbers in each metaphase, the overlaps of chromosomes and the mean length of chromosome 1. FISH was performed in the interphase nuclei of MSCs for 6q, 7q and 17q abnormalities and for the enumeration of chromosomes via oligo-FISH in adipose-derived MSCs. The number of chromosomes in each metaphase was more variable in classical G-banding. The overlap of chromosomes and the mean length of chromosome 1 as observed via in situ karyotyping were comparable to those of classical G-banding (P=0.218 and 0.674, respectively). Classical G-banding and in situ karyotyping by two personnel showed normal karyotypes for both cell lines in five passages. No numerical or structural chromosomal abnormalities were found by the interphase-FISH. In situ karyotyping showed equivalent karyotype results, and the quality of the metaphases was not inferior to classical G-banding. Thus, in situ karyotyping with minimized cell manipulation and the use of less cells would be useful for karyotyping MSCs.     

Environmentally Benign and Efficient Ag2S‐ZnO Nanowires as Photoanodes for Solar Cells: Comparison with CdS‐ZnO Nanowires

In this work, we develop a low‐temperature, facile solution reaction route for the fabrication of quantum‐dot‐sensitized solar cells (QDSSCs) containing Ag₂S‐ZnO nanowires (NWs), simultaneously ensuring low manufacturing costs and environmental safety. For comparison, a CdS‐ZnO NW photoanode was also prepared using the layer‐by‐layer growth method. Ultraviolet photoelectron spectroscopy analysis revealed type‐II band alignments for the band structures of both photoanodes which facilitate electron transfer/collection. Compared to CdS‐ZnO QDSSCs, Ag₂S‐ZnO QDSSCs exhibit a considerably higher short‐circuit current density (J_sc) and a strongly enhanced light‐harvesting efficiency, but lower open‐circuit voltages (V_oc), resulting in almost the same power‐conversion efficiency of 1.2 %. Through this work, we demonstrate Ag₂S as an efficient quantum‐dot‐sensitizing material that has the potential to replace Cd‐based sensitizers for eco‐friendly applications.