Patterned surface topographies play vital roles in cellular response such as adhesion, proliferation, and differentiation. Here, we characterized adsorption of fibronectin (Fn) as a typical cell adhesion protein onto honeycomb-patterned porous films (“honeycomb film”) of poly (ε-caprolactone) (PCL) incubated in a Fn phosphate-buffered saline (PBS) solution by using atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). In order to determine how cells respond to a honeycomb film, focal adhesion of porcine aortic endothelial cells (PAECs) cultured on the Fn coated honeycomb films in a serum free medium were characterized by using immunofluorescencet labeling of vinculin and focal adhesion kinase autophosphorylated at the tyrosine residue 397 (pY 397 FAK). Fn adsorbed around the pore periphery of a honeycomb film to form fibriller aggregates in a ring-shape structure. The sites of pY 397 FAK and vinculin were overlapped and agreed well with the adsorption site of Fn fibrils. This demonstrated that PAECs adhered onto the honeycomb films at focal contact points localized around pore periphery. The expression of pY397FAK determined by an immunoprecipitation method was 3 times higher than that on a PCL flat film as a reference. These results imply that the signaling mediated by a integrin receptor-Fn binding were activated on honeycomb films and this type of signaling was activated effectively on a honeycomb film compared with on a flat film. The cell response to honeycomb films (adhesion pattern and phosphorilation of FAK) was supposed to originate from the regularly arraigned adsorption pattern of Fn determined by the pore structure of the film.
Perovskite-type La1−xBixMnO3 (LBMO), which are prepared by doping the Bismuth (Bi) ion in LaMnO3, were shown to exhibit the colossal magnetoresistance (CMR) effect. Samples were produced using a sintering process in an air atmosphere as a function of the Bi composition ratio x. X-ray diffraction measurements showed that the LBMO crystal structure varied among an orthorhombic (or rhombohedral) type with 0.0<x<0.3, to a cubic type with 0.3<x<0.5, and to a monoclinic type with for 0.5<x. The CMR effect of LBMO for x=0.2 was approximately 400% at 140 K. In addition, the magnetoresistance of the LBMO system was found to be proportional to the square of the magnetization. It was interpreted that, from XPS analysis, the valence states of manganese and bismuth atoms in LBMO contain [Mn3+,Mn4+] and [Bi3+, Bi2+ (or pseudo-divalent Bismuth)] ionic states.
Enhancement of the secondary ion intensity in the TOF-SIMS spectra obtained by Au+ and Au3+ bombardment was investigated in comparison with Ga+ excitation using polymer samples with different molecular weight distributions. Since the polymer samples used in this experiment have wide molecular weight distributions, the advantages of a gold cluster primary ion source over a monoatomic ion source could systematically be evaluated. It was found that a Au primary ion source for a TOF-SIMS instrument has advantages in such terms as (1) the mass effect of the monoatomic primary ion, i.e., Au+ vs. Ga+, (2) the cluster primary ion effect of Au3+ compared with Au+ and Ga+, and (3)decrease in the degree of fragmentation by usage of a cluster primary ion beam compared with a monoatomic ion beam.
Quantum confinement effect in the valence band of Ge nanodots, fabricated onto an ultrathin SiO2 film on Si(111) substrate, was clearly measured by means of photoemission spectroscopy. Dot-size dependent shifts of the highest occupied state were well described by quantized energy levels of confined holes by the spherical parabolic potential. Two-types of Ge nanodots with different interface conditions, named as ‘epitaxial’ and ‘non-epitaxial’, can be fabricated depending on the growth temperature. The actual confining potentials for the quantum states in the two-types of Ge nanodots were evaluated, which clearly indicates drastic reduction of the confining potential barrier height for the epitaxial dots owing to voids formed in the interface SiO2 layer just below the Ge nanodots.
Atomic force microscopy (AFM) is now recognized as one of the major tools to investigate the structural and mechanical properties of polymer surfaces. We were particularly interested in information obtained from force-distance curves of rubbery or melt state samples. By analyzing the force-distance curves, the sample deformation by the force applied on the surface and the resultant real height free from sample deformation were estimated. The force-distance curves also gave us Young's modulus by analyzing curves with Hertz theory. Thus, when force-distance curve measurements were performed on every point of the sample (force-volume measurements), we could obtain a sample deformation image, a real height image, and a Young's modulus image simultaneously. We demonstrated the application of this method on the blend of unvulcanized natural rubber and ethylene-propylene diene elastmer.
We investigate lateral manipulation of single adatoms on Si(111)-(7×7) surface using non-contact atomic force microscopy at room temperature. An atomic vacancy is used as an open space for the lateral manipulation. The tip trajectory signal of line scans during the manipulation can be successfully detected and clarifies the presence of quasi-stable adsorption sites on the surface. We also show that the mechanism of the manipulation is attributed to the short-range attractive interaction force from the tip apex atoms.
We have developed a newly designed high efficiency spectrometer system for ultra-soft X-rays with a VLS (Varied-Line-Spacing) grating and a two-dimensional CCD detector. This system can be adapted to the analysis of Li with Li Kα at high sensitivity. A polycapillary system is set in the upstream of the instrument as an X-ray lens to condense the ultra-soft X-rays for high efficiency measurement. There are no moving parts such as slit and drive system of grating in this system at all. And, these advantages make it possible to construct the high-resolution ultra-soft X-ray spectrometer with maximum possible desiring transmission efficiency and reproducibility. This instrument can be applied to the precision analysis of the chemical state of Li metallic, which is one of the key elements of the industrial materials such as an electrode material used for a fuel cell or a lithium battery for controlling the process of the reaction with an electrolyte.
Pentacene films grown on a graphite surface has been studied by using High-Resolution Electron-Energy-Loss Spectroscopy (HREELS) as a function of film thickness and of sample temperature. The HREELS spectra show that the adsorbed pentacene molecules are in a flat-lying geometry with the molecular plane parallel to the substrate. Further, we discuss the thickness and temperature dependences of the vibrational energies in terms of molecule-substrate and intermolecular interactions.