Influence of drying and water supplying after drying on tensile strength of cement mortar

This paper is concerned with the change in tensile strength of cement mortar sibjected to rapid drying and water supply after drying. Flexural strength was investigated for several cement paste specimens cured in water for a certain period, with some specimens dried for 1 day and cured again in water after drying. As a result, it is known that the flexural strength of the specimen allowed to dry becomes about of that of a sound specimen, but it is almost recovered after about 3 h water curing after drying. The reason why the strength changes is usually connected with a restrained stress due to drying shrinkage and a stress relaxation due to expansion caused by water absorption. However, when the restrained stress at the surface overtakes the tensile strength, and a considerable number of minute cracks occur, as was observed, the above explanation cannot be accepted, because the tensile stress is almost perfectly relaxed by the occurrence of the cracks. In this paper, the reason for the strength recovery as a result of water absorption is reconsidered by means of stress analysis and microscopic examination of the cracks.     

Photoreflectance study of GaAs and GaAs/GaAlAs single quantum wells grown on (001) Si substrates

The optical features associated with biaxially strained bulk GaAs and three GaAs/GaAlAs quantum wells (QWs), with widths of 52 Å, 120 Å and 200 Å, grown on (001) Si have been studied using photoreflectance at 300 K and 77 K. The ordering and/or separation of the light- and heavy-hole quantum transitions in the QWs can be tuned by altering the width of the well.     

Cases of multiple ventricular septal defects

We had 4 cases with multiple ventricular septal defects (VSDs) in complexed congenital heart disease. One of four had two separate VSDs detected by two dimensional echocardiography before operation. Second of four had additional infundibular muscular VSD which was detected by echocardiography in the intensive care unit (ICU) after patch closure of a perimembranous VSD. The third case had two additional VSDs of inlet muscular and subaortic septum detected by transesophageal and direct echocardiography during reoperation, beside a subpulmonary VSD which was originally diagnosed before Jatene operation for double outlet right ventricle. The fourth case had multiple trabecular muscular VSDs diagnosed by postoperative angiography soon after Rastelli operation. Since these additional multiple VSDs compromise the postoperative hemodynamics if those are unrecognized, it is indispensable to detect all VSDs before operation, using transthoracic and transesophageal echocardiography.     

Pseudomonas aeruginosa as a model microorganism for investigation of chemotactic behaviors in ecosystem

Motile bacteria sense changes in the concentration of chemicals in environments and respond in a behavioral manner. This behavioral response is called chemotaxis. Bacterial chemotaxis can be viewed as an important prelude to metabolism, prey-predator relationships, symbiosis, infections, and other ecological interactions in biological communities. Genome analysis reveals that a large number of environmental motile bacteria possess a number of genes involved in chemosensing and chemotatic signal transduction. Pseudomonas aeruginosa has a very complex chemosensory system with more than 20 chemotaxis (che) genes in five distinct clusters and 26 chemoreceptor (methyl-accepting chemotaxis protein [mcp]) genes. Among the 26 MCPs of P. aeruginosa, nine have been identified as MCPs for amino acids, inorganic phosphate, oxygen, ethylene, and volatile chlorinated aliphatic hydrocarbons, whereas 3 MCPs were demonstrated to be involved in biofilm formation and biosynthesis of type IV pilus. Six che genes are essential for chemotactic responses, while genes in Pil-Chp cluster and Wsp cluster are involved in type IV pilus synthesis and twitching motility and biofilm formation, respectively. P. aeruginosa, with its complex chemotaxis system, is a better model microorganism for investigating ecological aspects of chemotaxis in environmental bacteria than Escherichia coli and Salmonella enterica serovar Typhimurium, which possess a relatively simpler chemotaxis system.     

Regularization for ultrasonic measurements of tissue displacement vector and strain tensor

In this report, we present the regularization results of displacement vector measurement by the multidimensional cross-spectrum phase gradient method (MCSPGM), multidimensional autocorrelation method (MAM), and multidimensional Doppler method (MDM) without lateral modulation. In addition to the results of spatially variant regularization in displacement vector measurement using displacement variances, the results of displacement component-dependent regularization are presented. That is, according to the measurement accuracy of displacement components, the regularization is properly applied to the respective displacement components. For instance, only the regularization on the lateral displacement is effective. That is, for the lateral nonmodulation case, the accuracies and stabilities of lateral/elevational displacement measurements significantly increase. In conjunction, the convergence speed of phase matching also increases. The demonstrated measurements of the displacement vector distributions in experiments using inhomogeneous shear modulus agar phantoms confirm that displacement-componentdependent regularization enables better strain tensor measurement and shear modulus reconstruction from the viewpoints of accuracy and stability. The contrast-to-noise ratio (CNR) is useful to set regularization parameters properly for the displacement regularization, whereas the CNR is useless for shear modulus regularization in the sense that the accuracy of reconstruction value cannot be evaluated.     

Slab optical waveguide high-acidity sensor based on an absorbance change of protoporphyrin IX

A sensitive and fast-responsive evanescent wave absorption sensor has been constructed for pH measurements in highly acidic ranges. This sensor is based on a pH-dependent color change of protoporphyrin IX (PPIX). For the sensitive detection, a visible attenuated total reflection spectrometer with a slab optical waveguide (SOWG) was laboratory-made, and the guiding layer surface was modified with a PPIX-immobilized acrylamide-based thin membrane. The sensing membrane with a thickness of approximately 1 mum was directly fabricated on the SOWG glass surface by copolymerization of acrylamide, N,N'-methylene bisacrylamide, and PPIX in the narrow space confined by a cover plate. PPIX possesses two double bonds in its structure, and so it can be covalently incorporated into the membrane. The response characteristics of the PPIX-immobilized optode membrane were explored using aqueous solutions with different concentrations of HNO(3) or HCl. The optode membrane provided characteristic Soret band absorption spectra depending on the hydrogen ion concentration; the absorbance at 410 nm increased with increasing the concentrations in the range of 0.15-2 M, corresponding to the range of pH -0.3 to 0.8. The absorption signal reached 90% of its final value within 10 s, while the absorption signal was quite readily returned to background level simply by passing 2 mL of distilled water through a flow cell with a volume of 16.5 muL placed on the SOWG. Due to the rapid response and reversibility, this sensor could be operated in a flow-through mode as well as in a conventional static mode, where deionized water was conveniently used as a carrier and conditioning solution. In terms of the stability and precision, this sensor showed no significant change in response even after 100 assays and after being stored in a dry condition for over 6 months. Relative standard deviations for 10 replicate measurements were less than 1.8% in the linear range, and the detection limit calculated from 3 times of the standard deviation was 0.02 pH unit.     

Structure of optical singularities in coaxial superpositions of Laguerre-Gaussian modes

We investigate optical singularities in coaxial superpositions of two Laguerre-Gaussian (LG) modes with a common beam waist from the viewpoints of a general formulation of phase structure, experimental generation of various superposition beams, and evaluation of the generated beams' fidelity. By applying a holographic phase-amplitude modulation scheme using a phase-modulation-type spatial light modulator, output fidelity beyond 0.960 was observed under several typical conditions. Additionally, an elliptic-type folded singularity, which provides a different class of phase structures from familiar helical singularities, was predicted and observed in a superposition involving two LG modes of both radially and azimuthally higher orders.     

Superior performance of non-activated multi-walled carbon nanotube polymer actuator containing ruthenium oxide over a single-walled carbon nanotube

The electrochemical and electromechanical properties of actuators developed using a non-activated multi-walled carbon nanotube (MWCNT)–ionic liquid (IL) gel electrode containing ruthenium oxide (RuO₂) were compared with only-MWCNT and only-single-walled carbon nanotube (SWCNT) based actuators. The double-layer capacitance of the non-activated MWCNT electrode containing RuO₂ was larger than that of the only-MWCNT electrode. The non-activated MWCNT polymer actuator containing RuO₂ surpassed the performance of the only-MWCNT and only-SWCNT actuators in terms of the strain and maximum generated stress. Both MWCNTs and RuO₂ were required to produce large strain and quick response actuators that surpassed the performance of the only-SWCNT polymer actuator and exhibited characteristics sufficient for practical applications (e.g. tactile display).     

A multi-walled carbon nanotube/polymer actuator that surpasses the performance of a single-walled carbon nanotube/polymer actuator

Actuators were developed using activated and non-activated multi-walled carbon nanotube (MWCNT)–ionic liquid (IL) gel electrodes and compared to a single-walled carbon nanotube (SWCNT)-based actuator with respect to the electrochemical and electromechanical properties. The activated MWCNT–COOH/polymer actuator surpassed the SWCNT/polymer actuator in terms of the generated strain.     

Isolation and characterization of benzene-tolerant Rhodococcus opacus strains

Twenty-two benzene-utilizing bacteria were isolated from soil samples. Among them, three isolates were highly tolerant to benzene. They grew on benzene when liquid benzene was added to the basal salt medium at 10--90% (v/v). Taxonomical analysis identified the benzene-tolerant isolates as Rhodococcus opacus. One of the benzene-tolerant isolates, designated B-4, could utilize many aromatic and aliphatic hydrocarbons including benzene, toluene, styrene, xylene, ethylbenzene, propylbenzene, n-octane and n-decane as sole sources of carbon and energy. Strain B-4 grew well in the presence of 10% (v/v) organic solvents that it was capable of using as growth substrates. Genetic analysis revealed the benzene dioxygenase pathway is involved in benzene catabolism in strain B-4. A deletion-insertion mutant defective in the benzene dioxygenase large and small subunits genes (bnz A 1 and bnz A 2) was as tolerant to organic solvents as the wild-type strain B-4, suggesting that utilization or degradation of organic solvents is not essential for the organic solvent tolerance of R. opacus B-4.