Nanoscale molecular cavity in crystalline polymer membranes studied by molecular dynamics simulation

The size, shape, and connectivity of cavities in the crystals of syndiotactic polystyrene were investigated by molecular dynamics simulation. Cluster analysis of the free volume in the crystals clearly reveals the cavity structures: large individual holes are in an orderly manner connected by narrow channels. We call such a cavity structure a ‘molecular cavity’. The diffusion behavior and solubility of gases in the molecular cavity were also simulated. The extremely high solubility of a larger gas and the controllable diffusion path in the narrow channels proved the applicability of the concept of the molecular cavity to high performance separation membranes.     

3-D PTFE microstructure fabricated using synchrotoron radiation etching

Microfabrication technique using SR ablation for 3-D polytetrafluoroethylene (PTFE) structure is reported in this work. First of all, we investigated necessary basic data for the fabricated structure like the processing depth and the etching rate, etc. And, the exposure energy distribution was given to the surface of polytetrafluoroethylene by using the plane pattern to cross-section transfer (PCT) technique, 3-D microstructures was fabricated. To establish three dimension of highly accurate PTFE processing technology, we are researching the application to the device.     

Decomposition of Higher Oxides of Chromium Under Various Pressures of Oxygen

The formation of Cr₃O₈, Cr₂O₅, CrO₂, and Cr₂O₃ by the decomposition of anhydrous CrO₃ under a high oxygen pressure and their physical and chemical properties are presented. The crystal structure of CrO₂ is a rutile type and its lattice constants do not vary with the ratio O/Cr. The specific gravity of CrO₂ decreases with an increase in the ratio O/Cr. This is explained by assuming that the crystal structure of CrO₂ contains an excess of Cr ions at interstitial sites. This crystal model is supported by the low electrical resistivity of CrO₂. An electron microscopic examination showed an abnormal grain growth of CrO₂ during the decomposition of Cr₂O₅ to CrO₂. The activation energies of the decomposition of Cr₂O₅ and CrO₂ to Cr₂O₃ in air are 61.7 and 48.2 kcal. per mole, respectively. The pressure-temperature diagram of various chromium oxides has been determined. From the pressure-temperature curve of CrO₂-Cr₂O₃ the heat of decomposition is found to be 26.3 kcal. per mole.     

Neutron cloud poinds and concentration fluctuations of polymer blends

Summary Cloud points were observed in the blends of deuterated polystyrene (PSD) and hydrogeneous poly (vinyl methyl ether) (PVME) by means of temperature scanning Small Angle Neutron Scattering (SANS) technique. The scattering function in the miscible region can be described by the random phase approximation results calculated by de Gennes. This scattering function can also be expressed in the Ornstein-Zernike form in the small q region. A correlation length and spinodal point can then be determined from this critical fluctuation approach.     

Self-organized inorganic nanoparticle arrays on protein lattices

Cavities formed by proteins have been utilized as the reaction chamber for the fabrication of a range of inorganic nanoparticles, providing control of the size of particles by limiting growth and preventing agglomeration. In crystal form, proteins construct molecular arrays that can provide regularly arranged sites for nanoparticles. Here we report the fabrication of nanometric iron and indium particles using ferritin, an iron-storage protein. The indium nanoparticles thus formed have uniform spherical shape with diameter of 6.6 +/- 0.5 nm, while the iron nanoparticles are somewhat irregular in shape (5.8 +/- 1.0 nm). Regular two-dimensional arrays of these nanoparticles are successfully produced by crystallizing ferritin molecules on a water-air interface using the denatured protein film method. The lattice constant of these nanoparticle arrays is 13 nm with hexagonal packing, and arrays of more than 1 microm in area can be obtained by transfer onto silicon wafer.     

Metallization of cross-linked polyurethane resins by reduction of polymer-incorporated metal ion

Polyurethane (PU) resins having different degree of cross-linking were prepared by the reaction of 4,4′-methylenebis(phenyl isocyanate) (MDI) with various molar ratio of two kind of pentaerythritol ethoxylates (PEE15, ratio of ethyleneoxy (EO) unit/hydroxyl (OH) unit=15/4; PEE3, EO/OH=3/4) in the presence of cobalt(II) chloride at 100 °C for 48 h. Metallization behavior of the CoCl₂-containing PU resins by reduction with aqueous sodium tetrahydroborate solution was investigated by means of infra-red (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). It was confirmed by the measurement of degree of swelling and glass transition temperature that the PU resin having a higher molar ratio of PEE15/PEE3 has a lower degree of cross-linking. When the PU films were reduced at 20 °C, the PU resins with PEE15/PEE3=10/0, 8/2, and 6/4 afforded the films with a metallic luster, whose surface resistance increased in this order. The formation of cobalt metal on both the sides of the PU film was revealed from the results of the XPS and EPMA measurements. The PU resin having a lower degree of cross-linking could be more easily metallized by this reduction treatment.     

Representative velocity scale of Rayleigh-Bénard convection with shear-thinning fluids

Although natural convection is frequently encountered in various chemical processes, Rayleigh number (Ra) cannot be defined fully in shear-thinning fluid systems. In particular, the velocity scale, which is necessary to estimate the effective viscosity of the system, should be discussed carefully. Thus, in this study, the representative velocity scale of Rayleigh-Bénard (RB) convection, which is a typical example of natural convection, with shear-thinning fluids was investigated based on the velocity fields obtained using computational fluid dynamics. Numerical simulations revealed that the critical temperature difference at which RB convection starts to fully develop decreases with an increase in the shear-thinning property. The shear-thinning property also induced subcritical bifurcation. In addition, the velocity scale of convection increases with an increase in the shear-thinning property. Thus, the shear-thinning property is considered to accelerate convection. Compared with several types of velocity scales used by other researchers, significant deviations from the actual scale were observed. Therefore, a new type of velocity scale, including the buoyant to viscous force ratio, arbitrary parameter, and thermal diffusivity, was proposed. The proposed velocity scale allowed an approximate estimation of the actual velocity scale. Although further investigation of the validity is necessary with varying geometries and rheological parameters, this velocity scale will be useful for controlling RB convection with Newtonian/shear-thinning fluids.     

Filter-based energy-resolved X-ray computed tomography with a clinical imager

Filter-based energy-resolved X-ray computed tomography (CT) is an approach for implementing energy-resolved CT imaging using a flat-panel-detector-based cone-beam system. In this study, we performed experiments with a 20-cm-diameter phantom on a clinical X-ray imager. The material density results showed good agreement with the ideal values. We also propose an improved method for obtaining the detector response function and the X-ray spectrum, which requires fewer measurements and will be practical for future clinical use. Issues such as scatter and image noise remain to be addressed.     

Effect of practice on similar and dissimilar skills in patient transfer through training with a robot patient

With the number of hospital stays increasing, nurses require more training to handle a variety of patients. However, time for training in nursing schools is limited, and students lack the opportunity to practice on a diverse variety of patients. Using a robot to simulate actual patients, this study observes the learning transfer effect of practice on practice-similar and practice-dissimilar skills from one patient to another, and investigates which types of practice suit which kinds of training. An experiment was conducted by administering a pre-test, practice, a post-test, and a transfer test to two groups (N?=?8), each with different practice-related skills. The evaluation used a checklist covering required skills that were either similar or dissimilar across groups, depending on their practice. The effect of practice can be observed through a comparison of skills similar to one group but dissimilar to the other. The results show that practice facilitates learning transfer on similar skills but not, or to a lesser degree, on dissimilar skills. Furthermore, if skills needed to handle given symptoms are unfamiliar or inaccessible to students, practice related to those symptoms should be emphasized through simulated training with robots.