Preparation of thermosensitive and superabsorbent polymer hydrogels from trialkyl‐4‐vinylbenzyl phosphonium chloride‐N‐isopropylacrylamide‐N,N′‐methylenebisacrylamide copolymers and their properties

Thermosensitive and superabsorbent polymer hydrogels were synthesized by copolymerization of three kinds of tri‐n‐alkyl vinylbenzyl phosphonium chlorides (TRVB) with different lengths of alkyl chains, N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide (MBAAm). The water‐absorption ability and antibacterial activity of the hydrogels against Staphylococcus aureus (S. aureus) were investigated. The water content of TRVB–NIPAAm–MBAAm copolymers decreased with increasing temperature and increased with increasing phosphonium groups in the copolymers, while it decreased with increasing chain length of the alkyl groups in the phosphonium groups as well as with an increasing degree of crosslinking in the copolymers. The TRVB–NIPAAm–MBAAm copolymers with a higher TRVB content in the copolymers exhibited higher antibacterial activity against S. aureus, but decreased with increasing chain length of alkyl groups in phosphonium groups. The TRVB–NIPAAm–MBAAm copolymers exhibited the highest antibacterial activity at 30°C against S. aureus in deionized water. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 115–124, 2001     

A newly identified horseshoe crab lectin with specificity for blood group A antigen recognizes specific O-antigens of bacterial lipopolysaccharides

A 14-kDa lectin, named tachylectin-3, was newly identified from hemocytes of the Japanese horseshoe crab, Tachypleus tridentatus. This lectin exhibited hemagglutinating activity against human A-type erythrocytes, but not against the B- and O-types of erythrocytes and animal erythrocytes, including those of sheep, rabbit, horse, and bovine. The hemagglutinating activity of tachylectin-3 was equivalent to that of a previously identified lectin, named tachylectin-2, with affinity for N-acetyl-D-glucosamine or N-acetyl-D-galactosamine. However, the activity of tachylectin-3 was not inhibited by these two N-acetylhexosamines at 100 mM but was inhibited by a blood group A-pentasaccharide at a minimum inhibitory concentration of 0.16 mM. Furthermore, the hemagglutinating activity was strongly inhibited by bacterial S-type lipopolysaccharides (LPSs) from Gram-negative bacteria but not by R-type LPSs lacking O-antigens. One of the most effective S-type LPSs was from Escherichia coli O111:B4, with a minimum inhibitory concentration of 6 ng/ml. These data suggest that tachylectin-3 specifically recognizes Gram-negative bacteria through the unique structural units of O-antigens. Ultracentrifugation analysis revealed that tachylectin-3 is present in dimer in solution. A cDNA coding for tachylectin-3 was isolated from a hemocyte cDNA library. Tachylectin-3 consisted of two repeating sequences, each with a partial sequence similarity to rinderpest virus neuraminidase. Tachylectin-3 and three previously isolated types of tachylectins were all predominantly expressed in hemocytes and released from hemocytes in response to external stimuli. These lectins present at injured sites suggest that they probably serve synergistically to accomplish an effective host defense against invading microbes.     

Simulations of neutron deceleration in a multistage UCN turbine using a multilayer monochromator

A neutron turbine is a neutron decelerator with neutron reflectors on a rotor. The multistage neutron turbine using multilayer monochromators has three rotors to decelerate very cold neutrons to ultra-cold neutrons. Reflecting blades on the rotors are flat and the incident direction of neutrons is perpendicular to the mirror surface. The use of a multistage turbine makes the incident velocity to be about 150 m/s which is faster than the existing neutron turbines and the three rotors make the velocity change smaller in one stage than the Doppler shifter employing Bragg reflection. It simultaneously improves the neutron extraction efficiency from a cold neutron source and the neutron deceleration. The peak deceleration efficiency assuming unit reflectivity in this three-stage turbine is about 0.71 from 150 m/s to UCN, and that of the final stage is about 0.81 from 50 m/s to UCN.     

Liquid rubber as a reactive softener for 1-chlorobutadiene–butadiene rubber

Blending of hydroxyl-terminated liquid butadiene rubber (HT-BR) with 1-chlorobutadiene–butadiene rubber (CB–BR) was carried out in the presence of isopropylidenedicyclohexyl diisocianate (IPCI) or sulfur as a curing agent, It was found that the HT-BR/CB–BR blend displayed a good plasticity, i.e., its Mooney viscosity became lower than that of CB–BR, which brought abcut a good processability. The HT-BR fraction (E_s from the HT-BR/CB–BR blend vulcanizates, which was prepared by the IPCI-cured system, was evaluated to be ca. 20% by the equilibium swelling test in benzene. The E_s of the sulfur-cured blend was ca. 70% This result shows that HT-BR acted as a reactive softener when it was compounded with CB–BR by curing with the diisocyanate. The tensile strength of the IPCI vulcanizate was exceedingly higher than that of sulfur-cured vulcanizate at all blend raios of HT-BR to CB–BR. © 1996 John Wiley & Sons, Inc.     

Remote radiation imaging system using a compact gamma-ray imager mounted on a multicopter drone

A remote radiation imaging system comprising a lightweight Compton camera and a multicopter drone was developed to remotely and quickly measure radioactive contamination inside the buildings of the Fukushima Daiichi Nuclear Power Station (FDNPS). The drone system is used for measuring detailed radiation distributions in narrow areas, which have been difficult to gauge with conventional aircraft monitoring using helicopters. A measurement of radiation distributions in outdoor environments in the coastal areas of Fukushima, Japan, was performed. The drone system with the Compton camera succeeded in remote observations of dense hotspots from the sky over a contaminated area near the FDNPS. The time required for image reconstruction is approximately 550 s in the case of a 9-m flight altitude for the hotspots with a surface dose rate of several tens of µSv/h. This drone system will be used inside the buildings of the FDNPS for remote measurement of radioactive contamination.     

Radiation imaging using a compact Compton camera inside the Fukushima Daiichi Nuclear Power Station building

The Fukushima Daiichi Nuclear Power Station (FDNPS), operated by Tokyo Electric Power Company Holdings, Inc., went into meltdown in the aftermath of a large tsunami caused by the Great East Japan Earthquake of 11 March 2011. The measurement of radiation distribution inside the FDNPS buildings is indispensable to execute decommissioning tasks in the reactor buildings. We conducted a radiation imaging experiment inside the turbine building of Unit 3 of the FDNPS by using a compact Compton camera and succeeded in visualizing high-dose contamination (up to 3.5 mSv/h). In addition, we drew a three-dimensional radiation distribution map inside the turbine building by integrating the radiation image resulting from the Compton camera into the point cloud data of the experimental environment acquired using a scanning LRF. The radiation distribution map shows the positions of these contaminations on a real space image of the turbine building. The radiation distribution map helps workers to easily recognize radioactive contamination and to decrease their own exposure to radiation because the contamination cannot be observed with the naked eye.     

Ca2+/Mg(2+)-dependent endonuclease in marrow CD34 positive and erythroid cells in myelodysplasia

Endonucleases capable of producing internucleosomal DNA cleavage are one of the key enzymes in apoptosis. We examined endonuclease activities contained in nuclei of CD34+ and erythroid cells in the bone marrow (BM) from 12 patients with the myelodysplastic syndromes. The levels of Mg(2+)-dependent and acidic endonucleases showed little changes as compared with those from normal BM. By contrast, the level of Ca2+/Mg(2+)-dependent endonuclease was appreciably higher in MDS erythroid cells than normal counterparts, although the activity varied markedly in CD34+ and erythroid cells. Our results suggested that Ca2+/Mg(2+)-dependent endonuclease is related to ineffective erythropoiesis in MDS.     

Parallel operation of voltage source inverters

Parallel operating systems of voltage source inverters with other inverters or with the utility source are sensitive to disturbances from the load or other sources and can easily be damaged by overcurrent. Thus extremely careful attention should be given to the system design of parallel operating inverters. Types of system configuration, control methods, and means of protection against failure are summarized, and several methods are proposed. Features and problems of these systems are discussed     

Vector-controlled double-inverter-fed wound-rotor induction motorsuitable for high-power drives

In this paper, the principle and the results of an experimental study concerning a new high-power inverter drive system are presented. One usual method of supplying large vector-controlled AC drives is by three-level inverters configured with 6-in 6-kV 6-kA gate-turn-off thyristors. These inverters can be adopted for drives that have ratings less than several thousand kilowatts. However, in the case of drives rated more than several thousand kilowatts, two inverters have been combined using interphase reactors. However, interphase reactors have problems of acoustic noise and high losses and, in addition, are bulky and expensive. To overcome these problems, a new configuration using a wound-rotor induction motor and two current controlled pulsewidth modulation inverters is proposed. In this configuration, the outputs of the two inverters are combined electromechanically in the machine and, as a result, novel features can be obtained