Surface characterization of poly(N-isopropylacrylamide) grafted tissue culture polystyrene by electron beam irradiation, using atomic force microscopy, and X-ray photoelectron spectroscopy

To understand features of polymers grafted by electron beam (EB) irradiation method, we investigated topology of poly(N-isopropylacrylamide) (PIPAAm) grafted tissue culture polystyrene (TCPS) (PIPAAm-TCPS) prepared by EB irradiation, using atomic force microscopy (AFM) in air and under aqueous conditions. Furthermore, surfaces properties of PIPAAm-TCPS surfaces before and after cell culture were also examined for evaluation of functionality of the surface as biomaterials, using XPS analysis. Three types of PIPAAm-TCPSs with different graft densities (1.0+/-0.1, 1.6+/-0.1, and 2.0+/-0.1 microg/cm2 of the grafted) were obtained (abbreviated as 11PIPAAm-, 16PIPAAm-, and 20PIPAAm-TCPS) by using different initial monomer concentration (20, 55, and 65 wt%). Contact angles (costheta value) of the surfaces increased with an increase in density of the grafted polymer. AFM observation in air clearly revealed that original TCPS surface possesses scratched and grooved topology (ca. 10 nm height of the scratch), while PIPAAm-TCPSs surfaces exhibited nanoordered PIPAAm particle-like domains. The size of the particles also increased proportionally initial IPAAm monomer concentration. The 11PIPAAm-and 16PIPAAm-TCPS surfaces having ca. 10-30 nm and ca. 40-50 nm size of the particles also displayed scratched and grooved topology featured in basal TCPS. However, the larger sizes of the particles (ca. 40-100 nm) formed on 20PIPAAm-TCPS surfaces adequately conceals the topological feature of the basal TCPS surfaces. The AFM images indicate that the graft polymer is as ultra thin as the scratch and grooves featured on basal TCPS are discernible, and the grafted PIPAAm layer become thicker with an increase of the monomer concentration. For 16PIPAAm-TCPS surfaces, the nanoordered particles were also observable in aqueous conditions at 20 degrees C and 37 degrees C. Comparison between the images obtained at 20 degrees C and 37 degrees C suggest that the domains are not likely to exhibit significant swelling and shrinking by temperature change, although the topology of PIPAAm grafted onto clover glass surface (50 microm thickness of the gel layer) were dramatically changed by temperature change in early reports. This difference should be due to ultra thin thickness of the grafted PIPAAm, which is subject to more restricted molecular motion by basal hydrophobic TCPS interfaces, as we reported previously. XPS C1s and N1s spectra of 16PIPAAm-TCPS surface after removal of cells suggest that proteins and/or peptides components possibly remained on the surfaces. Based on results from XPS analysis, we further discuss surface properties of 16PIPAAm-TCPS as biomaterials, comparing those of PIPAAm grafted polystyrene prepared by a radio frequency plasma method used in recent reports.     

Photodegradation of cellulose acetate film in the presence of benzophenone as a photosensitizer

To study the effectiveness of photosensitizers to accelerate the degradation of cellulose acetate (CA) under ambient environment, CA (degree of substitution = 2.45) films containing benzophenone, which is one of the typical photosensitizers, were prepared and their degradative behavior by photoirradiation was examined. Decrease in molecular weight of CA and generation of carbon dioxide, carbon monoxide, and acetic acid from the CA films were observed by the irradiation of xenon arc lamp light, which was passed through a filter for cutting off the wavelength shorter than 275 nm. With increasing the concentration of benzophenone, the molecular weight of CA decreased and the generation of the degradation products from the CA films increased. These results may suggest that radical reactions of CA films proceed by photoirradiation and lead to oxidation and random cleavage of CA, and that benzophenone is an effective additive to accelerate the degradation of CA under ambient environment. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Antioxidant and anticancer properties of metalloporphyrins embedded in liposomes

Reactive oxygen species (ROS) are implicated in many disease such as inflammation, arteriosclerosis, cancer. Therefore, a water-soluble cationic metalloporphyrins with SOD activity are studied widely as antioxidant drugs. Further, liposomes are applied to drug delivery system (DDS) as drug carriers and investigated for example disposition and stability. We designed PEG modified liposomes for avoiding reticuloendothelial system (RES) and embedded cationic metalloporphyrins for DDS, evaluated antioxidant and anticancer property. Preservation of these particle size measured DLS in an in vitro system, in order to simulate in vivo conditions of flow. Result of this measurement, we found Pluronic F-68/ liposomes have a long circulation property, and avoid fusion with plasma protein. SOD activity was determined by the stopped-flow analysis and cytochrome c assay, which allowed the evaluation of k(cat) and IC(50) for the reaction with a superoxide anion radical (.O(2)(-)). Anti cancer property was measured by cell viability test. We found that F-68/ liposomes were the most effective catalyst as antioxidant and anticancer. These results revealed that porphyrin-embedded PEG-liposomes had the property of long circulation in blood and that this compound was effective as a SOD model compound with a drug carrier capacity.     

Direct observation of local atomic order in a metallic glass

The determination of the atomic configuration of metallic glasses is a long-standing problem in materials science and solid-state physics. So far, only average structural information derived from diffraction and spectroscopic methods has been obtained. Although various atomic models have been proposed in the past fifty years, a direct observation of the local atomic structure in disordered materials has not been achieved. Here we report local atomic configurations of a metallic glass investigated by nanobeam electron diffraction combined with ab initio molecular dynamics simulation. Distinct diffraction patterns from individual atomic clusters and their assemblies, which have been theoretically predicted as short- and medium-range order, can be experimentally observed. This study provides compelling evidence of the local atomic order in the disordered material and has important implications in understanding the atomic mechanisms of metallic-glass formation and properties.     

Near infrared spectroscopy as high-throughput technology for screening of xylose-fermenting recombinant Saccharomyces cerevisiae strains

Recently, genetic engineering efforts have been made to develop recombinant Saccharomyces cerevisiae strains able to utilize xylose, an inexpensive and abundant carbon source. However, their construction and selection processes are limited by the speed and expenses of the existing testing methods, thus a rapid and equally precise method will significantly increase the number of tested strains. Here, near infrared (NIR) spectroscopy is proposed as a successful alternative method for screening recombinant xylose-fermenting S. cerevisiae. Supernatant samples of fermentation solutions from one diploid and three haploid recombinant strains were collected along the fermentation process. NIR spectra of the diluted supernatant provided effective differentiation of strains consistent with their phenotypic and genotypic features. This result could be used as a feedback for multicomponent analysis, in order to develop regression model for quantification of consumed glucose and xylose, produced ethanol, glycerol, and xylitol. Robust partial least-squares regression models with high prediction accuracy that are effective with any strain were achieved for all components when the modeling was performed with combined data of all strains, achieving 0.21-1.49 g/L of standard error of prediction with calibration, prediction, limit of detection and limit of quantification in the range of 1.0-4.5 and 3.0-13.4 g/L, respectively.     

Large area thin film Si module

An initial efficiency of 14.1% (J_sc=13.6 mA/cm², V_oc=1.392 V, FF=74.3%) has been achieved for a-Si/transparent interlayer/poly Si solar cell (total area of 1 cm²). Both a-Si and crystalline Si films were fabricated by plasma chemical deposition at low temperature. The short circuit current was enhanced by the introduction of a transparent intermediate layer. An initial aperture efficiency of 11.7% has been achieved for 910×455 mm² a-Si/poly Si integrated solar cell submodule, where the laser-scribing techniques were applied for series interconnections. The results of our first run of 266 submodules in our pilot plant showed the average efficiency of 11.2%, which is applicable for mass production.     

Effect of spectral irradiance distribution on the outdoor performance of amorphous Si//thin-film crystalline Si stacked photovoltaic modules

Effects of spectral irradiance distributions on the outdoor performance of amorphous Si//thin-film crystalline Si stacked photovoltaic (PV) modules installed at Shiga-prefecture in Japan have been investigated. Outdoor solar spectrum measurements revealed that more than 95% of annual total spectra were blue-rich compared to AM1.5 standard solar spectrum. The outdoor performance of the modules had a higher spectral dependence than that of polycrystalline Si modules. Also, the peak of the histogram of annual spectral indexes well corresponded to the peak of the outdoor performance. The results indicate that the actual spectral irradiance distribution is important in designing stacked PV modules.     

Estimation of traffic congestion distance using frequency division multiplexing based on IEEE802.15.4

We propose a system to estimate the traffic congestion distance using IEEE 802.15.4, that is extended by multicommunication frequency division multiplexing. Our proposed system is developed at 20% equipped rate, where five lanes are considered. Furthermore, in our proposed system, it is assumed that the equipped rate in all lanes increases. Our proposed method can estimate an error rate lower than 10% approximately at on equipped rate greater than 50%. Additionally, we use 16 terminals in the actual environment. From the actual experiment, we find that our proposed method involving the use of communication pattern 2 is 300% faster than the existing method. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.