Gas transport in poly(vinyl-p-isopropylbenzoate): Comparison and correlation with some other poly(vinyl esters)

Gas permeability in poly(vinyl-p-isopropylbenzoate) (PVp-i-PrB) was determined by a timelag method. The transport properties were discussed from comparison with the permeability data of other poly(vinyl esters), which were studied previously. All these polymers are structurally related, and the size of a side group or the position of its substituent was changed systematically. The isopropyl group of PVp-i-PrB is attached at the para position of a phenyl ring and is the largest in size. As a result gas diffusivity and therefore permeability were increased. The effect of the substituent on gas diffusivity was explained as it increases the interchain and intrachain distances. The discussion was supported from the comparison of the density data between PVp-i-PrB and other poly(vinyl esters). The diffusion coefficients of six glassy poly(vinyl esters) were correlated at their T_g and good correlations were shown to the free volume and its fraction. On the other hand, gas solubility was little affected by the change of an alkyl group on a phenyl ring. The solubility data of PVp-i-PrB and poly(vinyl benzoate) were shown to be clearly correlated with the critical properties of the penetrants. © 1995 John Wiley & Sons, Inc.     

Micro machining for control of wettability with surface topography

A micro fabrication is presented to manufacture hydrophobic surfaces with micro-scale structures. Hydrophobicity is controlled with the shape and the alignment of micro pillars in the structure. The structures are manufactured in large areas at high production rates in the following processes: (1) the structure is fabricated on a tool by focused ion beam sputtering; (2) the reverse structure is formed on a metal plate by incremental stamping using the structured tool; and (3) the structure is transferred onto plastic plates by molding. A consecutive stamping is also proposed to fabricate several structures on a surface accurately with a structured tool, in which the moving pitch of the structured tool is numerically controlled. The effect of the surface topography on hydrophobicity is discussed with measuring contact angles on the structured surfaces in the water droplet tests. Hydrophobicity on the plastic plate is associated with the solid fraction on the structured surface based on the Cassie–Baxter model. A larger contact angle is observed for a smaller solid fraction of the surface.     

Transverse surface waves in a piezoelectric material carrying a gradient metal layer of finite thickness

The existence and propagation behavior of transverse surface waves in a layered structure concerning a piezoelectric substrate and a gradient metal layer are theoretically investigated in this paper. The Wentzel-Kramers-Brillouin (WKB) method is applied to obtain the analytical solutions in the gradient metal layer. The dispersion equation for transverse surface waves in such structure is obtained in a quite simple mathematical form, where the material gradient of the metal layer assumes arbitrary functions. Effects of material gradient on three types of dispersion behavior are discussed in detail based on a proper classification. Numerical results show that the material gradient in the metal layer evidently affects the fundamental mode shape of the transverse surface waves but has negligible effects on the higher order modes.     

Asymmetry in object substitution masking occurs relative to the direction of spatial attention shift.

A sparse mask that persists beyond the duration of a target can reduce its visibility, a phenomenon called object substitution masking. Y. Jiang and M. M. Chun (2001a) found an asymmetric pattern of substitution masking such that a mask on the peripheral side of the target caused stronger substitution masking than on the central side. Assuming spatial attention was focused toward the target, the peripheral and central masks were located in the same and opposite direction of an attentional path with reference to the target in their study. We hypothesized that this asymmetric mask configuration relative to the attentional shift contributes to asymmetric substitution masking. To test this hypothesis, we conducted four experiments among which the presence or absence of the center–periphery relationship and the presence or absence of the asymmetric mask configuration were manipulated independently and orthogonally. The results suggest that asymmetric substitution masking occurs relative to the direction of spatial attention irrespective of the central–peripheral relation. We propose that the asymmetry in substitution masking might be explained by attentional momentum associated with orienting toward the target. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An Experimental Study of a Cooperative Positioning System

Several position identification methods are being used for mobile robots. Dead reckoning is a popular method but due to the error accumulation from wheel slippage, its reliability is low for measurement of long distances especially on uneven surfaces. Another popular method is the landmark method, which estimates current position relative to known landmarks, but the landmark method's limitation is that it cannot be used in an uncharted environment. Thus, this paper proposes a new method called Cooperative Positioning System (CPS) that is able to overcome these shortcomings. The main concept of CPS is to divide the robots into two groups, A and B where group A remains stationary and acts as a landmark while group B moves and then group B stops and acts as a landmark for group A. This process is repeated until the target position is reached. Compared with dead reckoning, CPS has a far lower accumulation of positioning errors, and can also work in three dimensions. Furthermore, CPS employs inherent landmarks and therefore can be used in uncharted environments unlike the landmark method. In this paper, we introduce the basic concept of CPS and its positioning principle. Next, we outline a second prototype CPS machine model (CPS-II) and discuss the method of position estimation using the variance of positioning error and weighted least squares method. Position identification experiments using the CPS-II model give a positioning accuracy of 0.12% for position and 0.32 degree for attitude after the robots traveled a distance of 21.5 m.     

Doping Mechanism and Permittivity Correlations in Nd-Doped BaTiO3

BaTiO₃ forms an extensive range of solid solutions with Nd₂O₃ by means of the double substitution mechanism: Ba + Ti 2Nd, as shown by both a phase diagram study and Rietveld refinement using powder neutron diffraction data. The solid solutions have the general formula Ba_1-xTi_1-xNd_2xO₃Odxd0.12 at 1300°C and 1300°C and O dxd at 1400°C. With increasing x, the symmetry changes from tetragonal to cubic at x 0.09. The sharp permittivity maximum at 127°C in stoichiometric BaTiO₃ broadens very rapidly with increasing x and gradually moves to lower temperatures: this appears to be because, with substitution of Nd onto Ti sites, formation of the ferroelectric domains is increasingly difficult because of the presence of dipole-inactive Nd³⁺ ions on the Ti sites.     

Clinicopathological study of cases with Mycobacterium szulgai infection

Pulmonary mycobacteriosis is usually caused by Mycobacterium tuberculosis, Mycobacterium avium complex, or Mycobacterium kansasii. There are, however, other slow-growing mycobacteria which can cause pulmonary infection. Mycobacterium szulgai, first reported in 1972, is a scotochromogenic species which can affect human lungs, although human-to-human spread of infection is thought to be unlikely. We have recently treated three cases of middle-aged to elderly persons (45-87 year-old), two of them had underlying diseases (one with intrapulmonary and the other with extrapulmonary). All patients had constitutional symptoms (cough, sputum, dyspnea), and chest roentgenograms demonstrated either cavitation with scattered nodules or peripheral infiltrates predominantly in upper lobes, resembling pulmonary tuberculosis. In two cases, M. szulgai was identified by using DNA-DNA hybridization method. The in vitro susceptibility of M. szulgai to antimycobacterial drugs was better than that of M. avium complex, and it was resistant only to paraaminosalicylate, cycloserine, and partially to isoniazid. Pulmonary disease of three patients were successfully treated with a combination of multiple antimycobacterial agents including rifampin, ethambutol, isoniazid, or streptomycin.     

Extralobar pulmonary sequestration mimicking cystic adenomatoid malformation in prenatal sonographic appearance and histological findings

An infant girl with extralobar pulmonary sequestration (PS) composed of congenital cystic adenomatoid malformation (CCAM)-like structure is presented. Initially, the antenatal sonographic findings indicated CCAM. The macroscopic findings of the resected specimen were compatible with extralobar PS; however, the microscopic findings showed cystic structure mimicking type II CCAM. The combination of PS and CCAM is rare, and it is likely that the embryological origin is common to both. There is confusion in the classification of these two congenital anomalies. In this report, the histological and sonographic findings of PS and CCAM are discussed.     

Renin and prorenin in hog brain: ubiquitous distribution and high concentration in the pituitary and pineal

With the objective of clarifying the nature of renin-like activity in the brain, we have devised methods to distinguish true renin from acid protease. These methods were used to determine the regional distribution of true renin in hog brain. The pineal was found to be the richest source of renin followed by the adenohypophysis and choroid plexus. The hypothalamus, cerebellum and amygdala contained moderately high concentrations of renin. Renin concentration in the neurohypophysis was negligible. Many regions contained activatable prorenin. The molecular weight and the pH-dependence of the brain renin were identical to these same properties of renal and plasma renins. Based upon its specific affinity to concanavalin A, brain renin was judged to be a glycoprotein. The electrofocusing pattern of renin from different regions of the brain differed from that of plasma and kidney renins, a discrepancy which could be interpreted as evidence for the endogenous synthesis of renin in the brain.