Thermoacoustic effects of inviscid fluids

Thermoacoustic effects of inviscid fluids are studied with the use of linearized hydrodynamic equations. The heat flux and the acoustic energy source due to acoustic waves are related to entropy oscillations due to irreversible processes, and are evaluated for a plane wave in a long cylindrical tube with the boundary condition that the local oscillation of the temperature is absent at the wall surface. The heat flux and acoustic energy source obtained in the standing wave approximation give qualitative explanations of heat pumping and similar experiments and stability limits.     

H Robust servo problem with H∞ norm constraint

A robust servo problem with an H-infinity norm constraint is investigated based on the LMI (Linear Matrix Inequality) approach to the H-infinity control problem. The following results are obtained. (1) A necessary and sufficient condition for the existence of an H-infinity controller with robust tracking property is derived. It consists of the following two indepent conditions: (i) the existence of an H-infinity controller; (ii) a boundary constraint at the reference mode. (2) If there exists an H-infinity controller with robust tracking performance, there exists one whose order equals the sum of an H-infinity controller and the internal model.     

Single-trial analysis of voice-stimulus-evoked potentials

We are developing a brain-computer interface (BCI) for event-related potentials (P300) using speech stimulus in the Japanese language based on the need to investigate amyotrophic lateral sclerosis (ALS) patients. Previously, we studied a single-trial analysis of P300 with a 4-Hz lowpass filter in order to improve the entry speed of the BCI. However, the problem was a low detection accuracy, i.e., approximately 30%–80%. In this article, we reviewed the application of independent component analysis (ICA) in order to improve the accuracy of single-trial analysis of P300. As a result, the detection ratio improved from 54.2% for the traditional 4-Hz low-pass filter to 90.9% in the choice of one between two. Furthermore, in an off-line experiment, the detection ratio of the P300 response to each sound of “a, i, u, e and o” improved in the task to choose one among five with synthetic speech stimulus. The maximum detection ratio was 94.7%, and the detection ratio per sound improved from 47.0% to 85.1%.     

Responses of an Amazonian teleost, the tambaqui (Colossoma macropomum), to low pH in extremely soft water

Our goal was to compare the internal physiological responses to acid challenge in an acidophilic tropical teleost endemic to dilute low-pH waters with those in nonacidophilic temperate species such as salmonids, which have been the subjects of most previous investigations. The Amazonian tambaqui (Colossoma macropomum), which migrates between circumneutral water and dilute acidic "blackwater" of the Rio Negro, was exposed to a graded low-pH and recovery regime in representative soft water (Na+ = 15, Cl- = 16, Ca2+ = 20 mumol L-1). Fish were fitted with arterial catheters for repetitive blood sampling. Water pH was altered from 6.5 (control) to 5.0, 4.0, 3.0, and back to 6.5 (recovery) on successive days. Some deaths occurred at pH 3.0. Throughout the regime, there were no disturbances of blood gases (O2 and CO2 tensions and contents) or lactate levels, and only very minor changes in acid-base status of plasma and red cells. However, erythrocytic guanylate and adenylate levels increased at pH's less than or equal to 5.0. Down to pH 4.0, plasma glucose, cortisol, and total ammonia levels remained constant, but all increased at pH 3.0, denoting a stress response. Plasma Na+ and Cl- levels declined and plasma protein concentration increased at pH 3.0, indicative of ionoregulatory and fluid volume disturbance, and neither recovered upon return to pH 6.5. Cortisol and ammonia elevations also persisted. Transepithelial potential changed progressively from highly negative values (inside) at pH 6.5 to highly positive values at pH 3.0; these alterations were fully reversible. Experimental elevations in water calcium levels drove the transepithelial potential positive at circumneutral pH, attenuated or prevented changes in transepithelial potential at low pH, and reduced Na+ and Cl- loss rates to the water during acute low-pH challenges. In general, tambaqui exhibited responses to low pH that were qualitatively similar but quantitatively more resistant than those previously documented in salmonids.     

Chemical composition and its distribution of emulsion copolymers composed of styrene and ethyl acrylate as hydrophobic and hydrophilic comonomers

Summary Chemical composition and its distribution of styrene (St)-ethyl acrylate (EA) copolymers synthesized by emulsion copolymerization under different monomer ratios and polymerization conditions were examined by ¹H-NMR and high-performance liquid chromatography (HPLC), respectively, and compared with those of bulk copolymers. It was newly found that the chemical composition of copolymer at early stage is affected by the concentration of emulsifier (SDS, sodium dodecyl sulfate) and monomer/water ratio, and is almost independent of the concentration of initiator or polymerization temperature. The EA fraction decreased with the increase of SDS concentration and converged to the value calculated using distribution factor (f_d) when SDS concentration was extrapolated to zero. These results indicate that the EA fraction in micelle decreased compared to the expected value from f_d due to the interaction of EA monomer with emulsifier. From HPLC, it was found that each copolymer showed a sharp single peak at an early stage of polymerization indicating that no homopolymer or copolymer with different composition was produced.     

Harmonic resonance in a composite right‐handed and left‐handed transmission line periodically loaded with Schottky varactors

Harmonic resonance is characterized in a composite right‐handed and left‐handed (CRLH) transmission line periodically loaded with Schottky varactors, termed a Schottky CRLH line, to achieve efficient second harmonic generation. CRLH line dispersion can cause the second harmonic wave to have the same phase velocity as the fundamental. Application of such fundamental wave enables its second harmonic to develop spontaneously. Both the fundamental and second harmonic waves can gain amplitudes as their phases advance owing to left‐handedness so that a second harmonic of significant amplitude can be obtained with the aid of cavity resonance. In this study, we discuss the design criteria for a Schottky CRLH line as a platform for second harmonic generation based on harmonic resonance. Copyright © 2015 John Wiley & Sons, Ltd.     

Verification and evaluation of automatically designed cooling channels for block-laminated molds

This study discusses an automatic design method of injection mold cooling channels using a genetic algorithms (GA) and a finite element method (FEM), combined with an evaluation function based on unsteady-state heat transfer and linear static deformation. The uniformity of cooling and the deformation effect were observed in the injection mold with the automatically designed cooling channel through a verification experiment. The genetic algorithm was applied in the following steps: the generation of finite elements of individuals expressing different cooling channel shapes, the definition of the fitness function to evaluate individuals, the genetic operation for individuals, and the automatic generation of the cooling channel shape. Finally, based on a molding experiment, the cooling and deformation effects were investigated. Results of resin cooling uniformity, temperature distribution of molding parts, and deformation of mold were demonstrated.     

Synthesis and characterization of polytriphenylamine containing ether bond in the main chain

Four triarylamine monomers that have an ether linkage, bis(N-phenyl-N-4-t-butylphenyl-4-aminophenoxy)ethane (TPAE), bis(N-phenyl-N-4-t-butylphenyl-4-aminophenoxy)butane (TPAB), bis(N-phenyl-N-4-t-butylphenyl-4-aminophenyl)ether (TPAO), and bis(N-4-tolyl-N-1-naphtyl-4-aminophenoxy)ether (NPAO) were prepared and polymerized using iron (III) chloride as an oxidant. Polymers, which are soluble in common organic solvents, were obtained at the yields of higher than 70%, and with glass transition temperatures of higher than 170 °C. The hole mobility decreased in the order of PNPAO > PTPAO > PTPAE = PTPAB > PBTPA, which indicates that the ether oxygen increases mobility.     

Increased prevalence of penicillin-resistant viridans group streptococci in Japanese children with upper respiratory infection treated by beta-lactam agents and in those with oncohematologic diseases

BACKGROUND: Viridans group streptococci, especially penicillin-resistant strains, have been emerging as pathogens of bacteremia in neutropenic patients with hematologic malignancies. OBJECTIVES: To survey the penicillin susceptibilities of viridans group streptococci in Japanese children with and without oncohematologic diseases and to evaluate the effect of the short term administration of beta-lactam agents on the antibiotic susceptibility. METHODS: We tested 113 isolates of viridans group streptococci by the microdilution method for the minimal inhibitory concentrations (MICs) to 10 antibiotics. We isolated 40 isolates from the throats of children with an upper respiratory infection (URI) before beta-lactam antibiotic treatment, 32 isolates after the treatment, 33 isolates in hospitalized children with oncohematologic diseases and 8 isolates from blood. RESULTS: Twenty-five isolates (62.5%) from the children with URI before treatment were penicillin-intermediate or -high level resistant (MIC > or = 0.25 microg/ml). The prevalence of those isolates after antibiotic treatment (87.5%) was significantly increased compared with that before treatment (P = 0.03). The prevalences of the penicillin-high level resistant isolates (MIC > or = 4 microg/ml) in the children with oncohematologic diseases (39.4%) and in the isolates from blood (62.5%) were significantly higher than that in the children with URI before treatment (12.5%) (P < 0.01). Decreased susceptibilities to other beta-lactam agents were observed in the penicillin-high level resistant strains. CONCLUSIONS: The high prevalence of penicillin-intermediate or -high level resistant viridans group streptococci in healthy Japanese children was documented. The administration of beta-lactam agents decreased the prevalence of penicillin-susceptible isolates in the children with URI. High prevalences of penicillin-high level resistant isolates were observed in the oncohematologic patients and in the isolates from blood.