Microscopic mechanisms for initiation and evolution of femtosecond laser-induced columnar structures above the surface level of aluminum.

A better understanding of the formation of femtosecond (fs) laser-induced surface structures is key to the control of their morphological profiles for desired surface functionalities on metals. In this work, with fs laser pulse irradiation, the two stages of formation mechanisms of the columnar structures (CSs) grown above the surface level are investigated on pure Al plates in ambient air. Here, we find that the redeposition of ablated microscale clusters following fs laser pulses of irradiation acts as the nucleation sites of CS formation, which strongly affects their location and density within the laser spot. Furthermore, we suggest their structural growths and morphological shape changes are directly associated with the competition among four laser-impact hydrodynamical phenomena: laser ablation, subsequent molten metal flow, particles' redeposition, and metal vapor condensation with continued pulse irradiation.

Rotationally symmetric colorization of metal surfaces through omnidirectional femtosecond laser-induced periodic surface structures.

Following femtosecond (fs) laser pulse irradiation, the formation of a new type of low-spatial-frequency laser-induced periodic surface structure (LSFL) patterns, namely, omnidirectional LSFLs (OD-LSFLs) with the periodic ordering of their orientations, are investigated on Ni in this Letter. Using a liquid crystal polymer patterned depolarizer, we periodically rotate the polarization of fs laser pulses across the laser spot and create OD-LSFLs by raster scanning fs laser pulses. We also show that the period of the OD-LSFL orientation rotation can be controlled with the defocused distance, and OD-LSFLs can significantly expand the viewing angle of the structural colors in the azimuthal direction without noticeable color degradations.

Synthesis of nanoparticles using electrical explosion of Ni wire in Pt solution.

The structure, size and morphology of nanoparticles produced by electrical explosion of Ni wire in Pt(NH3)2(NO2)2 solution were investigated. TEM results showed the formation of Ni and Pt nanoparticles as a result of the procedure. Ni nanoparticles were formed by the explosion of the Ni wire due to the passage of high current, evaporation, ionization, and cooling in the liquid medium. Ni nanoparticles were near spherical and showed particle sizes ranging from a few nanometers up to 50 nm. Pt nanoparticles were possible formed by the dissolution of OH- in Pt(NH3)2(NO2)2 solution during the electrical explosion of the Ni wire resulting in a plasma reaction. The formed Pt nanoparticles were ellipsoidal and showed particle sizes ranging to less than 5 nm. The lattice parameter of the Pt nanoparticles almost corresponded to the standard values reported. The obtained results indicate that Pt nanoparticles can be formed from a Pt solution without a reducing agent by electrical explosion of a metallic wire resulting in a plasma reaction.

Thermal resistance of light emitting diode PCB with thermal vias.

Light emitting diodes (LEDs) are already familiar for use as lighting sources in various electronic devices and displays. LEDs have many advantages such as long life, low power consumption, and high reliability. In the future, as an alternative to fluorescent lighting, LEDs are certain to receive much attention. However, in components related to advanced LED packages or modules there has been an issue regarding the heat from the LED chip. The LED chip is still being developed for use in high-power devices which generate more heat. In this study, we investigate the variation of thermal resistance in LED modules embedded with thermal vias. Through the analysis of thermal resistance with various test vehicles, we obtained the concrete relationship between thermal resistance and the thermal via structure.

Multi-Angular Colorimetric Responses of Uni- and Omni-Directional Femtosecond Laser-Induced Periodic Surface Structures on Metals.

We investigated the colorimetric behaviors of metal surfaces with unidirectional low-spatial-frequency laser-induced periodic surface structures (UD-LSFLs) and omnidirectional LSFLs (OD-LSFLs) fabricated using femtosecond laser pulse irradiation. With the CIE standard illuminant D65, incident at -45°, we show that UD-LSFLs on metals transform polished metals to gonio-apparent materials with a unique behavior of colorimetric responses, depending on both the detection and rotation angles, whereas OD-LSFLs have nearly uniform gonio-apparent colors at each detection angle, regardless of their rotation. These colorimetric behaviors can be observed not only at the angles of diffraction but also near the angle of reflection, and we find that the power redistribution due to Rayleigh anomalies also plays an important role in the colorimetric responses of UD- and OD-LSFLs, in addition to diffraction.

Gene expression profile related to prognosis of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a heterogeneous group of diseases with respect to biology and clinical course. Through genome-wide scanning, we can have an improvement of the diagnosis and assay system of AML. Microarray was performed for the identification of acute myeloid leukemia prognosis. We divided patients into two groups (good prognosis group, GPG and poor prognosis group, PPG) based on differences in the individual reactions to treatment. Gene expression profiles were analyzed using microarray. Among genes up-regulated at least two-fold and down-regulated at least 0.5-fold in HL-60, we chose three up-regulated genes (PPP2CA, ME3, and CCDN2) and three down-regulated genes (GLO1, ANXA2, and BMI1) and confirmed the expression of these six genes by RT-PCR. We created a leukemia-specific subclass microarray, based on the gene expression profiles. Clinical samples from the bone marrow of four patients were hybridized on this microarray. Among the genes selected by the microarray technology, NB4, silenced TRIB3 and overexpressed XRN2 were not differentiated in spite of treatment with ATRA. This indicates that XRN2 and TRIB3 play an important role in cell differentiation. These data provided an expression profile for the diagnosis and prognosis of AML patients and identified candidate genes that might allow the prognosis of AML through the relative comparison of the expression level of genes between GPG and PPG.

Improved Sensing Behaviors in Reduced Graphene Oxide Functionalized with Ni(OH)2 Nanoparticles.

In this paper, we detail improvements in the sensing properties of reduced graphene oxide (RGO), which were achieved through functionalization. The functionalization process utilizes graphene oxide suspensions, generating nanoparticles on the RGO surface mainly comprised of Ni(OH)2 phase. Raman spectra indicate that functionalization increases the degree of disorder in RGOs. NO2 gas sensing tests reveal an approximate increase of 154% in the sensor response of the RGOs after functionalization. Possible mechanisms for improving sensing responses via functionalization are discussed. The enhancement is due to the spillover effect, to the increase of the sensor surface by the catalytic particles, to the reduction of RGO conduction volume through the generation of depletion region, and to the resistance modulation of the heterojunctions.

Microstructure and properties of cross-roll rolled and heat treated metastable TiNbSn alloy.

A (Ti-35mass%Nb)-4mass%Sn alloy was cross-roll rolled with a reduction ratio of 70% in which the roll axes are tilted by ± 5 degrees away from the transverse direction of the rolled sample and then aged at 250 degrees C for 2 h. Cross-roll rolling was found to increase yield strength and Young's modulus, simultaneously. Yield strength was higher in cross-roll rolled than in conventionally rolled at same reduction ratio. Yield and tensile strength further increased by a low temperature ageing by ψ precipitation hardening and microstructure refinement. Yield and tensile strength of the aged 70% cross-roll rolled sample were higher than those of the aged 70% conventionally rolled one.

Expression profile identifies novel genes involved in neuronal differentiation.

In the presence of NGF, PC12 cells extend neuronal processes, cease cell division, become electrically excitable, and undergo several biochemical changes that are detectable in developing sympathetic neurons. We investigated the expression pattern of the apoptosis-related genes at each stage of neuronal differentiation using a cDNA microarray containing 320 apoptosis-related rat genes. By comparing the expression patterns through time-series analysis, we identified candidate genes that appear to regulate neuronal differentiation. Among the candidate genes, HO2 was selected by real-time PCR and Western blot analysis. To identify the roles of selected genes in the stages of neuronal differentiation, transfection of HO2 siRNA in PC12 cells was performed. Down-regulation of HO2 expression causes a reduction in neuronal differentiation in PC12 cells. Our results suggest that the HO2 gene could be related to the regulation of neuronal differentiation levels.

High-resolution analysis of condition-specific regulatory modules in Saccharomyces cerevisiae.

We present an approach for identifying condition-specific regulatory modules by using separate units of gene expression profiles along with ChIP-chip and motif data from Saccharomyces cerevisiae. By investigating the unique and common features of the obtained condition-specific modules, we detected several important properties of transcriptional network reorganization. Our approach reveals the functionally distinct coregulated submodules embedded in a coexpressed gene module and provides an effective method for identifying various condition-specific regulatory events at high resolution.

NCAM as a cystogenesis marker gene of PKD2 overexpression.

ADPKD (Autosomal Dominant Polycystic Kidney Disease) is characterized by the progressive expansion of multiple cystic lesions in the kidneys. ADPKD is caused by mutations in Ed-pl. consider PKD1 and PKD2. Recently a relation between c-myc and the pathogenesis of ADPKD was reported. In addition, c-Myc is a downstream effector of PKD1. To identify the gene regulated by PKD2 and c-Myc, we performed gene expression profiling in PKD2 and c-Myc overexpressing cells using a human 8K cDNA microarray. NCAM (neuronal cell adhesion molecule) levels were significantly reduced in PKD2 overexpressing systems in vitro and in vivo. These results suggest that NCAM is an important molecule in the cystogenesis induced by PKD2 overexpression.