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形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2018-04-24, 資料番号: PA1910003000

Microbially mediated arsenate (As(V)) and Fe(III) reduction play important roles in arsenic (As) cycling in nature. Extracellular electron shuttles can impact microbial Fe(III) reduction, yet little is known about their effects on microbial As mobilization in soils. In this study, microcosm experiments consisting of an As-contaminated soil and microbial communities obtained from several pristine soils were conducted, and the effects of electron shuttles on As mobilization were determined. Anthraquinone-2,6-disulfonate (AQDS) and riboflavin (RF) were chosen as common exogenous and biogenic electron shuttles, respectively, and both compounds significantly enhanced reductive dissolution of As and Fe. Accumulation of Fe(II)-bearing minerals was also observed, which may lead to re-immobilization of As after prolonged incubation. Interestingly, Firmicutes-related bacteria became predominant in all microcosms, but their compositions at the lower taxonomic level were different in each microcosm. Putative respiratory As(V) reductase gene (arrA) analysis revealed that bacteria closely related to a Clostridia group, especially those including the genera Desulfitobacterium and Desulfosporosinus, might play significant roles in As mobilization. These results indicate that the natural soil microbial community can use electron shuttles for enhanced mobilization of As; the use of this type of system is potentially advantageous for bioremediation of As-contaminated soils.

形態: カラー図版あり, Note: The International Tribology Conference (ITC) Tokyo 2015 Special Issue (Part 2), Physical characteristics: Original contains color illustrations, Accepted: 2016-01-01, 資料番号: PA1710001000

In the present study, two types of nine-recess hybrid journal bearings (HJBs) with different recess geometries, i.e., the Young Leaf Mark and the square, were operated at a rotational speed of up to 67,000 rpm using the cryogenic journal bearing test apparatus at JAXA to clarify influences of the journal rotating direction on the cryogenic HJB. Liquid nitrogen was supplied to the test bearings with a pressure of up to 4 MPa. The test bearings were 60 mm in diameter and 25 mm in width, with a 0.055 mm clearance and a recess area ratio of 0.186. Based on the experimental results the dependence of the rotor vibration on the rotational speed was confirmed to be affected by the journal rotating direction. The test HJBs with the positive sweepback angle of the recess leading edge showed the smallest rotor vibration in the high-rotational-speed operation where the hydrodynamic effect was predominant.

The temperature distribution on a centre-holed thin foil of molybdenum, used as a sample and heated using a sample-heating holder for electron microscopy, was measured using an infrared thermal camera. The temperature on the heated foil area located near the heating stage of the heating holder is almost equal to the temperature on the heating stage. However, during the measurement of the temperature at the edge of the hole of the foil located farthest from the heating stage, a drop in temperature should be taken into consideration; however, so far, no method has been developed to locally measure the temperature distribution on the heated sample. In this study, a method for the accurate measurement of temperature distribution on heated samples for electron microscopy is discussed.

In the present study, a nine-recess hybrid journal bearing (HJB) having a Young Leaf Mark recess was operated at a rotational speed of up to 75,000 rpm using the cryogenic journal bearing test apparatus at JAXA, to clarify an onset speed of the rotor instability supported by the cryogenic HJBs. Liquid nitrogen was supplied to the test bearing with a pressure of up to 4 MPa. The test bearing is 60 mm in diameter, 25 mm in width, with a 0.055-mm clearance and a recess area ratio of 0.186. When the HJB was operated at a rotational speed of over 74,000 rpm in liquid nitrogen, hard frictional contact between the bearing surface and the journal surface occurred, which consequently caused considerable damage to the Cr2O3 coating film on the journal. The results confirmed that the HJB surface damage had relatively little effect on HJB performance. Therefore, cryogenic HJB tested can be considered to have sufficient robustness when the rotational speed is below 60,000 rpm.

The durability of a hybrid ceramic 25-mm-bore ball bearing having a single outer land-guided retainer was evaluated and improved in liquid hydrogen at speeds up to 120,000 rpm (120,000 min-1) (3 million DN) by comparing the propagation of superficial thermal microcracks on Si3N4 balls at various speeds. To select a tough Si3N4 ball capable of restraining crack propagation, bearing tests were conducted for three kinds of the Si3N4 balls with different jet-cooling systems. The test results showed that the Si3N4 ball having high fracture toughness as well as high thermal shock resistance could restrain the propagation of wide-ditch microcracks. With regard to the jet-cooling system, four nozzles were better than two nozzles with increasing jet speed. Furthermore, the jet flow aimed at the retainer was superior to that aimed at the inner race, and its result indicated that microcracks might be generated at the trace in contact with the outer raceway under insufficient cooling conditions with a large centrifugal force. Thus, decreasing the maximum contact stress of the outer race to 2.0 GPa by a limited race curvature of 0.51 could restrain the propagation of superficial microcracks.

In this study, we propose a simple hopping mechanism using the vibration of a two-degree-of-freedom system for a wheel-based stair-climbing robot. The robot, consisting of two bodies connected by springs and a wire, hops by releasing energy stored in the springs and quickly travels using wheels mounted in its lower body. The trajectories of the bodies during hopping change in accordance with the design parameters, such as the reduced mass of the two bodies, the mass ratio between the upper and lower bodies, the spring constant, the control parameters such as the initial contraction of the spring and the wire tension. This property allows the robot to quickly and economically climb up and down stairs, leap over obstacles, and landing softly without complex control. In this paper, the characteristics of hopping motion for the design and control parameters are clarified by both numerical simulations and experiments. Furthermore, using the robot design based on the results the abilities to hop up and down a step, leap over a cable, and land softly are demonstrated.

We propose a simple hopping mechanism using the vibration of a two-degrees-of-freedom (DOF) system for a fast stair-climbing robot. The robot, consisting of two bodies connected by springs, hops by releasing energy stored in springs and travels quickly using wheels mounted on its lower body. The trajectories of bodies during hopping change based on design parameters such as the reduced mass of the two bodies, mass ratio between the upper and lower bodies, spring constant, and control parameters such as initial contraction of the spring and wire tension. This property allows the robot to quickly and economically climb stairs and land softly. In this paper, the characteristics of hopping for the design and control parameters are clarified by both numerical simulation and experiments. Furthermore, fast stair climbing and soft landing are demonstrated.

はじめに: 胆管癌では高頻度に上皮内進展を伴うことが知られているが, その生物学的特徴は明らかにされていない. 我々は, 上皮内進展部 (intraepithelial spread portion: IESP) と浸潤部 (invasive portion: IP) の差異を明らかにする目的でMIB-1 positive rate(MIB-1 PR), AgNOR dot数 (AgNOR数) およびp53 positive rate (p53 PR) について解析した. 方法: 対象は胆管癌切除例20例で, MIB-1 PR, AgNOR数をそれぞれ算出した. p53 PRは4段階に分類し評価した (PR

Detection and location of failed fuel in a liquid-metal fast breeder reactor (LMFBR) are very important both for safety and availability. When a fuel failure is detected, it is desirable to identify the failed subassembly quickly to reduce plant shutdown time. The flux tilting method is expected to effectively identify the defective subassembly. The feasibility of the flux tilting method is investigated for an LMFBR with a 100-MW (electric) homogeneous core. A numerical simulation is performed to estimate the viability of the flux tilting method, and a combination of the flux tilting method and the sipping method is found to be very effective in identifying the failed subassembly. In this paper a functional scheme for a computer-aided failed fuel detection and location system is discussed as part of a future on-line support system.

ASME, SAE, and ASEE, Joint Propulsion Conference and Exhibit, 31st, San Diego, CA, July 10-12, 1995, 資料番号: AC1000102000, レポート番号: AIAA-1995-2718