Digital Laser Micropainting for Reprogrammable Optoelectronic Applications

Structural coloration is closely related to the progress of innovative optoelectronic applications, but the absence of direct, on-demand, and rewritable coloration schemes has impeded advances in the relevant area, particularly including the development of customized, reprogrammable optoelectronic devices. To overcome these limitations, a digital laser micropainting technique, based on controlled thin-film interference, is proposed through direct growth of the absorbing metal oxide layer on a metallic reflector in the solution environment via a laser. A continuous-wave laser simultaneously performs two functions—a photothermal reaction for site-selective metal oxide layer growth and in situ real-time monitoring of its thickness—while the reflection spectrum is tuned in a broad visible spectrum according to the laser fluence. The scalability and controllability of the proposed scheme is verified by laser-printed painting, while altering the thickness via supplementary irradiation of the identical laser in the homogeneous and heterogeneous solutions facilitates the modification of the original coloration. Finally, the proof-of-concept bolometer device verifies that specific wavelength-dependent photoresponsivity can be assigned, erased, and reassigned by the successive application of the proposed digital laser micropainting technique, which substantiates its potential to offer a new route for reprogrammable optoelectronic applications.     

The optical characteristics in the layers of Compact Disc-Recordable

The optical characteristics of the laser beam in the layers of Compact Disc Recordable (CD-R) has been studied. The optical disk which is compatible with currently used CD-drive consists of transparent polycarbonate (PC) substrate, organic dye recording layer, reflective gold layer, and ultra-violet (UV) cured protecting layer. For proper design of the layer structure, modeling of the optical characteristics in each layer is necessary. The reflection and local absorption of the laser beam energy in the layers of the disk were numerically calculated. The reflection of the disk oscillates with the thickness of dye layer due to the interference in the multilayers. The oscillation magnitude and period depend on the complex refractive index of the material. The energy absorption profile in the recording layer is dependent on the thickness of the layer.     

Crack-tip constraints of through-wall cracked pipes and its similarity to curved wide plates

In the present study, the effects of pipe geometries, material properties and loading conditions on crack-tip constraints of pipes with circumferential Through-wall crack (TWC) were investigated via systematic 3-dimensional (3-D) Finite element (FE) analyses. The crack-tip constraints were quantified by Q-stress, and to characterize the elastic-plastic strain hardening material behavior, Ramberg-Osgood (R-O) material was employed. Based on the FE results, it was observed that crack-tip constraints of pipes with TWC were dependent on crack length and thickness of pipe, however, the effects of each variables decreased as either thickness of pipe becomes thinner or crack length becomes longer. Moreover, the effects loading modes on Q-stresses for thin-walled pipes with TWC are negligible. Finally, the present Q-stresses of pipes were compared with those of Curved wide plate (CWP) in tension to address the similarity of crack-tip constraints between pipe and CWP, which could be used to produce the CWP to measure the fracture toughness of pipes accurately.     

Effect of Molecular Weight of Poly(Ethylene Glycol) Dicarboxylate on the Properties of Cross-Linked Hydrogel Film as an Antiadhesion Barrier

Poly(ethylene glycol) dicarboxylate (PEGDC)/poly(ethylene oxide) (PEO) cross-linked hydrogel films were developed as an antiadhesion barrier using an e-beam. The effects of molecular weight of PEGDC on hydrogel properties were investigated. The decrease in molecular weight of PEGDC increased the gel fraction and tissue adhesion, whereas the mechanical strength did not change considerably. On the other hand, the swelling ratio decreased rapidly with decreasing molecular weight of PEGDC. The cytotoxicity of PEGDC (2000 or 3000) was low, whereas that of PEGDC (1000) was higher. In animal studies, all hydrogels showed a better antiadhesive effect compared to the control.     

Rod-Like Structure of Cotton Cellulose/Polyvinyl Alcohol/Tellurium Dioxide (TeO2) Hybrid Nanocomposite and Antimicrobial Properties

We report on the in situ synthesis through sol-gel processing of a tellurium dioxide (TeO₂)–cellulose–polyvinyl alcohol (PVA) hybrid composite. The cellulose–PVA hybrid composite was synthesized through chemical graft in the presence of aqueous sodium hydroxide. Field emission scanning electron microscopy, SEM-EDX, high-resolution transition microscopy (FE-TEM) revealed that polycrystalline nanorods were uniformly distributed with sizes of 20?nm in the cotton cellulose–PVA–TeO₂ hybrid nanocomposite. The average size of TeO₂ crystallite was calculated to be 0.292?nm, as shown in the FE-TEM, SAED, and X-ray diffraction analysis. Furthermore, the hybrid nanocomposites were studied for their antimicrobial activity against Bacillus cereus and Escherichia coli strains, which was inhibited at a size of 10–12?mm after 24?h of incubation.     

Magnetic sensitivity enhanced novel fluorescent magnetic silica nanoparticles for biomedical applications

We synthesized novel fluorescent magnetic silica nanoparticles (FMSNPs) containing large magnetic components for biomedical application. By employing assemblies of magnetic nanoparticles as kernels against FMSNPs, both the saturation of magnetization and the magnetic resonance (MR) signal intensity were significantly enhanced. Furthermore, the cellular binding of FMSNPs was improved by introducing a positive charge on the surface of the FMSNPs, and fluorescent dyes on the surface of FMSNPs enable optical imaging of sub-cellular regions.     

Nanosurface-confined anisotropic growth and magnetism of ellipsoidal alpha-Fe nanogranules

We have investigated the nanosurface-confined anisotropic growth of ordered-ellipsoidal Fe nanogranules when an Fe plume was deposited at a slanting angle onto an anodized aluminum oxide (AAO) film. Layer-by-layer growth was also investigated. This growth is driven by two critical factors: (1) a new rhombic AAO cell and (2) the slanting deposition of the Fe plume. During slanting deposition, the rhombic AAO cell induces strong restrictions in the nucleation site, growth direction, and granular size; therefore, the degree of freedom during growth is restricted. The magnetic dipoles of the ordered Fe nanogranules are placed along the long axis of the ellipsoid at an angle of 180 degrees (antiparallel) due to the demagnetizing field, shape anisotropy, and magnetic dipole-to-dipole interactions.     

Isolation and identification of antimicrobial substances from Korean Lettuce (<Emphasis Type="Italic">Youngia sonchifolia</Emphasis> M.)

The aim of this study was to identify of antimicrobial substances from Korean Lettuce (Youngia sonchifolia M.). Water and ethanol extracts of Youngia sonchifolia M. exhibited antimicrobial activities against the microorganisms tested. Ethanol extract showed strong antimicrobial activities against most Gram positive and Gram negative microorganisms, whereas no lactic acid bacteria and yeasts were not affected. The antimicrobial compound G-6 was isolated from the ethyl acetate fraction obtained by silica gel column chromatography and HPLC and was confirmed as stable against heat treatment. Molecular weight of G-6 was calculated as 154 kDa based on information in the MS spectrum. G-6 was identified as 2-nonynoic acid (C₉H₁₄O₂) by UV, LC-EI/MS, and LC-CI/MS. In support of this, the chromatogram of G-6 was consistent with that of the 2-nonynoic acid standard. Antimicrobial activity of 2-nonynoic acid was identified in all samples, with a significant difference based on concentratio.     

Tuneable elastomeric nanochannels for nanofluidic manipulation

Fluidic transport through nanochannels offers new opportunities to probe fundamental nanoscale transport phenomena and to develop tools for manipulating DNA, proteins, small molecules and nanoparticles. The small size of nanofabricated devices and the accompanying increase in the effect of surface forces, however, pose challenges in designing and fabricating flexible nanofluidic systems that can dynamically adjust their transport characteristics according to the handling needs of various molecules and nanoparticles. Here, we describe the use of nanoscale fracturing of oxidized poly(dimethylsiloxane) to conveniently fabricate nanofluidic systems with arrays of nanochannels that can actively manipulate nanofluidic transport through dynamic modulation of the channel cross-section. We present the design parameters for engineering material properties and channel geometry to achieve reversible nanochannel deformation using remarkably small forces. We demonstrate the versatility of the elastomeric nanochannels through tuneable sieving and trapping of nanoparticles, dynamic manipulation of the conformation of single DNA molecules and in situ photofabrication of movable polymeric nanostructures.     

Radiation sensitivity of an Escherichia coli mutant lacking NADP+-dependent isocitrate dehydrogenase

Ionizing radiation induces the production of reactive oxygen species, which play an important causative role in radiation damage. NADP+-dependent isocitrate dehydrogenase (ICDH) in Escherichia coli produces NADPH, an essential reducing equivalent for the antioxidant system. The protective role of ICDH against ionizing radiation in E. coli was investigated in wild-type and ICDH-deficient strains. Upon exposure to ionizing radiation, the viability was lower and the lipid peroxidation was higher in mutant cells compared to wild-type cells. Activities of key antioxidant enzymes such as superoxide dismutase, catalase, glutathione reductase, and glucose-6-phosphate dehydrogenase were decreased by irradiation in both cells. Results suggest that ICDH plays an important role as an antioxidant enzyme in cellular defense against ionizing radiation.