Influence of domain orientation on the mechanical properties of lead zirconate titanate piezoelectric ceramics

The influence of domain orientation on the mechanical properties of lead zirconate titanate (PZT) piezoelectric ceramics has been investigated using un-poled and poled PZT ceramics. High mechanical properties, e.g., high elastic modulus and compressive strength, were obtained for the polarized PZT ceramics due to strain hardening caused by more severe domain switching during the loading process, while low mechanical properties for the un-poled ceramics. Fracture mechanics of the ceramics were influenced by the direction of the tetragonal lattice structure since cracks propagate along the long axis of the tetragonal structure (c-axis). Using X-ray diffraction and electron back scatter diffraction analysis, the domain switching characteristics could be clarified.     

Critical Current Densities and Vortex Dynamics in Ba(Fe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>As<Subscript>2</Subscript> Single Crystals

Superconducting properties are evaluated for high-quality single crystals of Ba(Fe_1−x Co _x )₂As₂ in a wide range of doping levels. The critical current density, J _c , in an optimally-doped crystal (T _c ∼24 K) shows a fishtail effect with its value over 10⁵ A/cm² even at 5 T below 10 K. Magneto-optical imaging has clarified rather homogeneous supercurrent flow in the crystal, in spite of a large amount of impurities. In the heavy-ion irradiated sample, the presence of columnar defects are confirmed and J _c has been enhanced by a factor of five at low temperatures, reaching 6×10⁶ A/cm² at 2 K under zero field. Flux creep rate in the heavy-ion irradiated sample has been reduced in accordance with the enhancement of J _c .     

A new etching technique for revealing the plastic deformation zone in an Al–Cu–Mg alloy

A new etching technique for revealing the plastic deformation zone in an Al–Cu–Mg alloy has been developed. The etching with the proposed etching agent was conducted on the deformed sample after being heated to 673 K for 3 h. With this etching technique, the plastic deformation zone was clearly observed even under low magnification. This was due to the change of microstructural characteristics in the plastic deformation zone after the heating process, in which there is significant precipitation of Al₂Cu and Mg₂Si, caused by the high energy arising from the severe deformation.     

Asbestos and DNA double strand breaks

A radiosensitive DNA repair-deficient xrs-5 cell line was used to study asbestos cytotoxicity and DNA double strand breaks (DSBs). Although xrs-5 cells did not show any increase in sensitivity to chrysotile fibers in short-term (4-h) treatment when compared with wild-type CHO cells, longer-term exposure (24 h) gave significantly lower cell survival accompanied by a cell growth delay as well as a higher DNA DSB induction in this mutant cell line. These results suggest an important role played by DNA DSBs at the initial stage of asbestos injury.     

Biosensor-based control of nitrification inhibitor in municipal wastewater treatment plants.

The effect of potassium cyanide (KCN) on nitrification processes in municipal wastewater treatment plants was studied by batch nitrification tests, which indicated that nitrification processes tend to be inhibited at a lower KCN concentration than the present discharge standard to sewerage. The experiment of the biosensor using nitrifying bacteria was also conducted for continuous monitoring of nitrification inhibitor in influent wastewater, and demonstrated that the biosensor can detect KCN at as low as EC10 of the abovementioned batch nitrification test. Moreover, to determine the effectiveness of application of the biosensor to avoid the impact of KCN due to an accidental spillage in a sewerage system, KCN was intentionally injected into the experimental models of activated sludge process equipped both with and without the biosensor. The model with the biosensor that could detect KCN could divert the wastewater including KCN to a refuge tank, which resulted in the avoidance of upset of the activated sludge process. On the other hand, the model without the biosensor was upset in the nitrification process due to KCN. Such differences demonstrate the effectiveness of the biosensor applied to countermeasures of an accidental spillage of toxic chemicals to avoid upset of nitrification in municipal wastewater treatment plants.     

Distribution of estrogen, nonylphenol and its derivatives in the sediments of a shallow lake.

To determine the distribution of endocrine disruptors (EDs) in lake water and sediments, field investigation was conducted in Lake Teganuma, which is a shallow eutrophic lake, highly affected by human activities. Concentration profiles with sediment depths were obtained for estrogens, nonylphenol (NP), nonylphenol ethoxylates (NPnEO), and nonylphenoxy acetic acids (NPnEC). 17beta-Estradiol (E2) was rarely detected, and 17alpha-ethynylestradiol (EE2) and estriol (E3) were undetected at all depths (0-98 cm) in any of the sediment core samples. The sediment concentrations of estrone (E1) ranging from <0.05 to 3.5 microg/kg-dry wt. and NP from 11.8 microg/kg-dry wt. to 21 mg/kg-dry wt. were obtained. The maximum concentrations of NPnEO and NPnEC in the core sediments were 2.5 mg/kg-dry wt. and 1.4 mg/kg-dry wt., respectively. The EDs concentrations are higher at the inlet than at the outlet (except for NP) in the sediments near the surface. The longitudinal distributions of E1, NPnEO and NPnEC in the benthic sediments show that the concentrations are highest at the inlet, and are fairly constant at lower levels towards the downstream. The obtained results also indicate that NP tends to be adsorbed to the organic particulates produced by algae, followed by sedimentation near the outlet of the lake.     

Analysis and occurrence of estrogen in wastewater in Japan.

This paper describes an analytical procedure for free estrogens and their conjugates in domestic wastewater. The procedure demonstrated in this study is innovative in terms of levels of detection and quantification of the following substances: estrone (E1); 17beta-estradiol (E2); 17alpha-ethynylestradiol (EE2); estriol (E3); estrone-3-sulfate (E1-S); beta-estradiol 3-sulfate (E2-S); estriol 3-sulfate (E3-S); estrone beta-D-glucuronide (E1-G); beta-estradiol 17-(beta-D)-glucuronide (E2-G); estriol 3-(beta-D)-glucuronide (E3-G); beta-estradiol 3-sulfate 17-glucuronide (E2-SandG); and estradiol 3,17-disulfate (E2-diS). The detection limits of this method ranged from 0.1 to 1.4 ng/l. The recovery efficiencies of the estrogens in the analysis from influent and effluent of the secondary settling tank in a wastewater treatment plant (WWTP) were higher than 94% for the free estrogens, but were less than 50% for the conjugated estrogens. The field study using this method was conducted at twenty WWTPs in Japan. The median concentrations of the estrogens ranged from ND to as high as >100 ng/l. In the influent and secondary effluent samples, the concentrations of E1, E2 and E3 were the same levels as those previously reported. We found that the conjugated estrogens exist at higher concentrations in the influent and the secondary effluent than in the other studies, and that the concentrations of the conjugated estrogens were higher than those of the free estrogens.     

Clinical evaluation of Dumon stent for tracheobronchial stenosis due to advanced esophageal carcinoma

We inserted Dumon stent to 13 patients with tracheobronchial stenosis due to advanced or recurrent esophageal carcinoma. Severe dyspnea was improved in 11 patients except for 2 patients with bilateral recurrent nerve palsy. 3 cases who had radiation therapy or chemotherapy lived over 150 days. We inserted esophageal stent in 4 cases. 2 patients died due to hemoptysis after 156 days and 35 days. We conclude that Dumon stent is one of the useful treatments in order to improve quality of life and prognosis of advanced or recurrent esophageal carcinoma.     

Induction of DNA double-strand breaks by restriction enzymes in X-ray-sensitive mutant Chinese hamster ovary cells measured by pulsed-field gel electrophoresis

This investigation was designed to determine whether the cytotoxic effects of different restriction endonucleases are related to the number and type of DNA double-strand breaks (DSBs) they produce. Chinese hamster ovary (CHO) K1 and xrs-5 cells, a radiosensitive mutant of CHO K1, were exposed to restriction endonucleases HaeIII, HinfI, PvuII and BamHI by electroporation. These enzymes represent both blunt and sticky end cutters with differing recognition sequence lengths. The number of DSBs was measured by pulsed-field gel electrophoresis (PFGE). Two forms of PFGE were employed: asymmetric field-inversion gel electrophoresis (AFIGE) for measuring the kinetics of DNA breaks by enzyme digestion and clamped homogeneous gel electrophoresis (CHEF) for examining the size distributions of damaged DNA. The amount of DNA damage induced by exposure to all four restriction enzymes was significantly greater in xrs-5 compared to CHO K1 cells, consistent with the reported DSB repair deficiency in these cells. Since restriction endonucleases produce DSBs alone as opposed to the various types of DNA damage induced by X rays, these results confirm that the repair defect in this mutant involves the rejoining of DSBs. Although the cutting frequency was directly related to the length of the recognition sequence for four restriction enzymes, there was no simple correlation between the cytotoxic effect and the amount of DNA damage produced by each enzyme in either cell line. This finding suggests that the type or nature of the cutting sequence itself may play a role in restriction enzyme-induced cell killing.     

A study of the effects of vibration on the electric power generation properties of lead zirconate titanate piezoelectric ceramic

To better understand how the electric power generated from PZT piezoelectric ceramics is affected by mechanical loading conditions the power generation was examined during cyclic loading under various loading conditions. The electric power generation was continuously examined using a monitoring system that we have recently developed. This system revealed that the electric power increased with increase of the applied load but then decreased when the applied load exceeded a certain level. In addition, greater electric power was generated with a simple beam configuration compared with a cantilevered beam. The change of electric power generation was directly related to the stress direction; high stress in the tetragonal structure parallel to the c-axis gave rise to high electric power generation. On the other hand, material failure, including domain switching and crack generation, caused a reduction of the electric power generated. Based upon our experimental data, suitable loading conditions to give high piezoelectric energy generation have been clarified.