The structural gene for phospholipase D (PLD) of an actinomycete, Streptoverticillium cinnamoneum, together with its promoter region was introduced into Streptomyces lividans using a shuttle ...vector--pUC702--for Escherichia coli and S. lividans. The transformant was found to secrete a large amount of PLD (about 2.0x10⁴ U/l, 42 mg/l) when cultured in a jar fermentor. Both an initial glucose concentration of 17.5 g/l and the feeding of carbon and nitrogen sources are effective for efficient secretion of PLD; under these culture conditions, the amount of PLD secreted reached a maximum level (about 5.5 x10⁴ U/l, 118 mg/l) after about 60 h. In contrast to the original producer, Stv. cinnamoneum, which secretes only a small amount of PLD (about 1.1x10³ U/l, 2 mg/l) along with other extracellular proteins, this heterologous expression system is markedly more efficient in production of secretory PLD.
A membrane-bound phospholipase D (PLD) has been identified and isolated in a soluble form from an actinomycete,
Streptoverticillium cinnamoneum. The enzyme has a monomeric structure with a molecular ...size of about 37 kDa, being the smallest among the enzymes so far reported. The enzyme catalyzes the hydrolysis of phosphatidylethanolamine and phosphatidylserine as preferred substrates, but not the transphosphatidylation reaction of their phospholipid groups to ethanol. Together with the absence of immunochemical cross-reactivity, these enzymatic properties demonstrate that the membrane-bound enzyme is distinct from the extracellular enzyme recently characterized and cloned from the same bacterial strain C. Ogino et al., J. Biochem. 125 (1999) 263–269 and is therefore regarded as a novel prokaryotic PLD.
Cyclic stresses around welding joint part affect the strength of mechanical components. In order to understand the fatigue phenomena caused by the cyclic stresses, non-destructive methods that can be ...related to number of stress cycles are necessary. In the present work, we used a newly developed scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor and observed three-dimensional magnetic fields of the specimen before and after four-point fatigue testing at room temperature in air. Low carbon steel plates (JIS SS400) were used in the experiments. It was found that the intensity of the magnet field in a direction perpendicular to the specimen surface was strongly affected by the fatigue cycles. This result means that we can evaluate the fatigue in welding joint area using quantitative magnetic field measurements. Furthermore, it was discovered that the key factor to evaluate the fatigue is the range between 'S' and 'N' ('peak to bottom' values) of the magnetic fields. The three-dimensional magnetic fields decrease before the dislocation does not accumulate enough to generate a small crack at the early stage of the fatigue.
Machine elements in humanoid robots for our life support require light weight, high accuracy and high output torque. In order to achieve low transmission error of the humanoid robot joints, wear of ...reinforced poly-ether-ether-ketone (PEEK) bushes against the 7075 aluminium alloy cam plates is investigated. Sliding fatigue wear tests of PEEK bushes in the humanoid robot leg joint were performed under various load torques. In the case of the bush under 127 Nm load torque at 5·7 mm s
−1
sliding velosity, the backlash values were stable after the running process in fatigue wear test. PEEK film was formed by the friction between PEEK bush and 7075 cam plate under compression load. The oscillation angle of the output axis in the robot joint was stable after early stage because of the solid lublication caused by the film. This means the backlash value was stable and decreased due to the PEEK film between the bush and the cam plate.
Due to constant exposure to high torque and loads toughness, compressive durability and light weight of joint parts are crucial factors for biped walking humanoid robot parts. When polymer ...transmission parts are used for the manufacture of humanoid robot joint, wear becomes an important factor in terms of transmission error (backlash) between the input and output axes, ex. between the motor and the robot's leg joint. In such joint system, a polymer bushes is directly connected to a cam plate, playing an important role in the robot's movement ability. In this work, the influence of wear of reinforced poly-ether-ether-ketone (PEEK) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order to establish the application possibilities in transmission parts in humanoid robot's joint. The PEEK bush surface conditions as well as the input axis-output axis backlash require close examination, so that efficient systems can be built. Sliding wear tests were performed on bushes under 0-50kgfcm loaded torque while the cam plate oscillated. Based on the wear observation, it was found that in a high load range the backlash increased along with number of cycles due to PEEK bush wear. The bush surface roughness also increased during testing. Roughness of PEEK bush surface and the loaded torque for output axis were significantly related to backlash of output axis in robot joint.
In this work, wear of reinforced poly-ether-ether-ketone (PEEK containing PTFE, graphite and carbon fibres) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order ...to establish the application possibilities in transmission parts in humanoid robot joints. The PEEK bush surface conditions as well as the input axis-output axis transmission error (backlash) require close examination. Sliding wear tests were performed on bushes under 900 kgfcm loaded torque, while the cam plate oscillated. Based on the wear observation, it was found that PEEK wear fragments in the interface between PEEK bush and aluminium alloy cam plate formed a PEEK film.
Root length density of maize (
Zea mays L.) and soybean
Glycine max (L.) Merr., measured with minirhizotrons, was compared with soil-water depletion, measured with neutron probes, to determine ...whether the soil-water-depletion method could indicate root length density and root depth in a stratified soil. The study was carried out in southeast Kansas, USA, on a Parsons silt loam soil (Mollic Albaqualf fine, mixed, thermic) overlying clay (a claypan). Measurements were taken during two dry periods, one in 1983 and one in 1984, to a depth of 1.35 m for soil water and to a depth of 1.15 m for root length density. At the beginning of the dry period, average soil water content for both crops throughout the profile was 0.47 m
3 m
−3 in 1983 and 0.42 m
3 m
−3 in 1984. During both dry periods, roots died back in the surface soil because the silt loam dried out; it was drier than the clay. The claypan inhibited root growth. In the clay, roots of both crops increased in root length density in the water year (1983) or decreased in root length density in the drier year (1984). In both years, the depth of maximum water depletion in the soil profile for maize (0.45 m in 1983, 0.90 m in 1984) corresponded well with the depth of maximum root length density measured with minirhizotrons (0.50 m in 1983, 0.80 m in 1984). The depths of maximum depletion for soybean (0.15 m and 0.30 m in 1983, and 0.60 m in 1984) also corresponded relatively well with the zones of maximum root length density (0.15 and 0.50 m in 1983, and 0.40 m in 1984). Depth of rooting was not evident from the soil-water measurements. Root length densities for both crops were low (less than about 1000 and 300 mm
−3 for maize and soybean, respectively) at bottom depths of the profile.
With the atmospheric concentration of CO2 increasing, it is important to know how this will affect crop growth. The objective of this study was to determine the effect of enriched CO2 on root growth ...of winter wheat (Triticum aestivum L. 'Newton') under both well-watered and dry conditions. The wheat was grown for 3 yr in 16 plastic chambers (121 by 92 by 168 cm) in the field under ambient CO2 (340 micro L L-1) and elevated levels of CO2 (485, 660, and 825 micro L L-1). Each chamber was placed over an underground box (77 by 37 cm at the top; 180 cm deep) containing a Muir silt loam (fine-silty, mixed, mesic Cumulic Haplustoll). The boxes could be pulled out of the ground for observation of roots. Half of the boxes were maintained at field capacity (0.38 m3 m-3) (well-watered or not stressed plants) and half between 0.14 to 0.25 m3 m-3 (drought-stressed plants). At harvest, root dry weights at different depths and stem dry weight were determined. Roots of plants grown under the three elevated levels of CO2 penetrated to the maximum depth of observation (176 cm) before roots of plants grown under the ambient level. At harvest, the difference in root growth between elevated and ambient levels of CO2 was most pronounced at the top level (0- to 10- cm depth). Roots of drought-stressed plants grown with 825 micro L L-1 CO2 had a grater dry weight than roots of well-watered plants grown with ambient CO2. The ratio of root to stem weight usually showed no trend (neither increase or decrease) with increasing CO2 concentration. Total dry weight at harvest of well-watered root grown at ambient CO2 (3-yr mean: 118 g m-2) was similar to that of drought-stressed roots grown at the highest level of CO2 (3-yr mean: 123 g m-2). The results indicated that high CO2 (825 micro L L-1) can compensate for restrictions in root growth by drought
