Electron microscopy of tRNA crystals. I. Thin crystals negatively stained with uranyl acetate

The first attempt to study crystal structures of tRNA by electron microscopy is described. Sufficiently thin crystals were prepared from yeast tRNAphe. The thickness of the thinnest was estimated at 130 A corresponding to a bilayer of the molecules. The L-shaped structure seemed to be maintained even after the negative staining with uranyl acetate. Optically filtered images from electron micrographs were compared with those simulated from the drawing of the molecular model by optical transform. The results suggest that the observed images reflect the real molecular arrangements within the crystal lattice although the shape of tRNA molecules seems to be somewhat modified by the uneven staining.     

The effect of cast iron graphite on friction and wear performance III: The lubricating effect of graphite under rolling-sliding contacts

The formation of nodular cast iron graphite films and the factors affecting squeeze film formation during rolling-sliding contact are discussed. The lubricating effect of the graphite is confirmed by roller tests and by practical gear tests. The frictional torque behaviour and wear change with surface treatments such as etching and hardening. The wear loss of ground specimens is greater than that of etched specimens because of differences in the substrate hardness and the microstructure. The formation of cast iron graphite films on hardened ground surfaces covered with a plastic flowed layer is difficult because of the small plastic deformation of the substrate, and severe wear occurs. The lowest values of the frictional torque and of the wear rate are obtained for ground surfaces with a substrate hardness of about 300 HV. This is due to the ease of formation of a graphite film as a result of the combined effects of fatigue failure of the surface and a squeeze phenomenon. The size of the spherical graphite particles affects film formation. If the size is doubled, the wear rate is halved. The grinding of tooth surfaces has a detrimental effect on the fatigue wear life.     

Meteorological parameters contributing to variability in 222Rn activity concentrations in soil gas at a site in Sapporo, Japan

Continuous ²²²Rn monitoring in soil gas since November 22, 2004 has revealed variability in activity concentration with time in the semi-natural woods on the campus of Hokkaido University in Sapporo, Japan. Among various factors affecting soil radon levels and variability, temperature was found to be dominant during three seasons when activity concentrations of ²²²Rn showed a diurnal high and nocturnal low with a boundary around 10 o'clock in the morning. This pattern was disturbed by low pressure fronts with occasional rain. The activity gradually decreased as soil temperatures decreased from late November to mid-December. After the ground surface was completely covered with snow, soil radon levels became low with a small fluctuation. There were several peaks of ²²²Rn on the time-series chart in winter. Those peaks appearing in early winter and early spring may be interpreted by considering meteorological parameters. In a few cases, the radon activity suddenly increased with increasing pressure in the soil at a depth of 10 cm, which may be associated with subsurface events such as seismic activity in the area.     

Molecular Dynamics Study of Interactions between the Water/ice Interface and a Nanoparticle in the Vicinity of a Solid Surface

ABSTRACT

In this study, non-equilibrium molecular dynamics simulations were conducted for a coexistence system of water and ice on a wall surface with a single nanoparticle to reveal the effects of water solidification on the nanoparticle in the vicinity of a wall surface. We further investigated the effect of the presence and size of particles on the density profile of water in the vicinity of the wall surface and the force acting on particles from water molecules, when the solidification interface contacted the wall and the particles. The results revealed that a strong mutual influence exists between the solidification interface and the nanoparticle on the wall’s surface; the nanoparticle on the wall prevents water solidification in proximity to the wall. Moreover, the force acting on the nanoparticle from water molecules changes as the solidification interface approaches; the cooling temperature is shown to affect the direction of this force. It indicates that the solidification process is a key influential factor which affects nanoparticle movements on a wall surface at molecular scales.     

Isolation of a novel mouse gene MA-3 that is induced upon programmed cell death

Haematopoietic progenitor cells were isolated from human fetal liver, obtained between 6 and 15 weeks gestation. After preparation of a single cell suspension, the cells were stored using a stepwise freezing protocol; taking the cells from room temperature through -70 degrees C to liquid nitrogen. Viability (trypan blue exclusion), morphology (Leishman stain), identification of cell type (flow cytometry) and growth characteristics in semi-solid culture medium were assessed using the fresh cell suspension. We were able to confirm that the predominant cells in human fetal liver up to about 15 weeks gestation are those of the erythroid lineage. It was established that viability in excess of 75% was required to ensure adequate growth in culture after frozen storage and it was deemed important to ensure morphological integrity of the cell preparations. The colonies formed in culture were observed to be producing haemoglobin between 7 and 9 days after initial seeding. We have determined that cells can be stored in liquid nitrogen for up to 2 years without loss of (1) viability, (2) morphological features and (3) ability to form colonies and produce haemoglobin in culture. These findings offer encouragement for the implementation of a cell bank to support an in utero transplantation programme.     

Linearity and nondeletion on monadic context-free tree grammars

In this paper, subclasses of monadic context-free tree grammars (CFTGs) are compared. Since linear, nondeleting, monadic CFTGs generate the same class of string languages as tree adjoining grammars (TAGs), it is examined whether the restrictions of linearity and nondeletion on monadic CFTGs are necessary to generate the same class of languages.     

Ricinoleic Acid in Common Vegetable Oils and Oil Seeds

An original gas chromatography/mass spectrometry method for quantifying trace amounts of ricinoleic acid (12-hydroxy-cis-9-octadecenoic acid) is detailed. Data are presented on trace amounts of ricinoleic acid found in several common vegetable oils and oils extracted from common oil seeds: e.g., ca. 30 ppm in commercial olive oil was the lowest amount; and ca. 2,690 ppm in oil extracted from cottonseeds was the highest amount.