Supercool and Superheat in bcc-hcp Transition of Solid 4He

The nucleation phenomenon in the structural transition between bcc and hcp phase of solid ⁴ He is investigated by an optical method together with pressure and temperature. At T_c1 (1.46 K), the single new phase seed was nucleated at some spot on the wall in contact with the superfluid and grown into the superfluid region. The nucleation is nothing to do with the original solid. The situation is almost the same for both cases of bcc to hcp (cooling) and hcp to bcc (warming). Whereas at T_c2 (1.77 K), the new phase seeds were nucleated at many sites inside the original crystal, which is the typical Martensitic transition. Since the transition is of first order, supercool and superheat were observed. Though the transition event occurred at random, accumulated events were pretty well represented by a standard nucleation probability model. The temperature width of supercool is larger than that of superheat at T_c1 . Whereas it is larger for superheat at T_c2 . In other words, supercool (and superheat) is more likely in the transition from bcc to hcp regardless of warming or cooling. It is qualitatively understood by the fact that the surface tension of hcp crystal against liquid is much larger than that of bcc crystal.     

A 12-ns 8-Mbyte DRAM secondary cache for a 64-bit microprocessor

This paper describes three circuit technologies that have been developed for high-speed large-bandwidth on-chip DRAM secondary caches. They include a redundancy-array advanced activation scheme, a bus-assignment-exchangeable selector scheme and an address-zero access refresh scheme. By using these circuit technologies and new small subarray structures, a row-address access time of 12 ns and a row-address cycle time of 16 ns were obtained. An experimental chip made up of an 8-Mbyte DRAM and a 64-bit microprocessor was developed using 0.25-μm merged logic and DRAM process technology     

Photoelectrochemical study of lanthanide titanium oxides, Ln2Ti2O7 (Ln = La, Sm, and Gd)

Photocatalytic activities for hydrogen evolution of lanthanide titanium oxides, Ln₂Ti₂O₇ (Ln = La, Pr, Nd, Sm, Gd, Dy, Ho, Er, and Yb) prepared by a solid-state reaction were studied. Hydrogen gas was clearly evolved in distilled water suspension of La₂Ti₂O₇ and Sm₂Ti₂O₇. From the photoelectrochemical measurements, the values of the flat band potential were estimated to be −0.04, −0.02, +0.27 eV for La₂Ti₂O₇, Sm₂Ti₂O₇, Gd₂Ti₂O₇, respectively, versus the normal hydrogen electrode (NHE). The values of the band gap energy were calculated to be about 3.29, 2.79, 2.82 eV for La₂Ti₂O₇, Sm₂Ti₂O₇, Gd₂Ti₂O₇, respectively. The photocatalytic activities of Ln₂Ti₂O₇ (La, Sm, and Gd) were discussed along with detailed band structures estimated in this study. From the band structures, Sm₂Ti₂O₇ is a possible candidate of photocatalyst responding to visible light.     

MD simulations to evaluate effects of applied tensile strain on irradiation-induced defect production at various PKA energies

Molecular Dynamics (MD) simulations were conducted to investigate the influence of applied tensile strain on defect production during cascade damages at various Primary Knock-on Atom (PKA) energies of 1–30 keV. When 1% strain was applied, the number of surviving defects increased at PKA energies higher than 5 keV, although they did not increase at 1 keV. The rate of increase by strain application was higher with higher PKA energy, and attained the maximum at 20 keV PKA energy with a subsequent gradual decrease at 30 keV PKA energy The cluster size, mostly affected by strain, was larger with higher PKA energy, although clusters with fewer than seven interstitials did not increase in number at any PKA energy.     

Engineering of Pseudomonas aeruginosa lipase by directed evolution for enhanced amidase activity: mechanistic implication for amide hydrolysis by serine hydrolases

A lipase from Pseudomonas aeruginosa was subjected to directed evolution for increased amidase activity to probe the catalytic mechanism of serine hydrolases for the hydrolysis of amides. Random mutagenesis combined with saturation mutagenesis for all the amino acid residues at the substrate-binding site successfully identified the mutation at the residue 252 next to the catalytic H251 as a hot spot for selectively increasing the amidase activity of the lipase. The saturation mutagenesis targeted for the oxyanion hole (M16 and H83) gave no positive results. The substitutions of Met or Phe for Leu252 significantly increased the amidase activity toward N-(2-naphthyl)oleamide (2), whereas the esterase activity toward structurally similar 2-naphthyl oleate (1) was not affected by the substitution. The triple mutant F207S/A213D/M252F (Sat252) exhibited amidase activity (k(cat)/K(m)) 28-fold higher than that of the wild-type lipase. Kinetic analysis of Sat252 and its parental clone 10F12 revealed that the amidase activity was increased by the increase in the catalytic efficiency (k(cat)). The increase in k(cat) suggested the importance of the leaving group protonation by the catalytic His during the break down of the tetrahedral intermediate in the hydrolysis of amides.     

Relationship between selected indoor volatile organic compounds, so-called microbial VOC, and the prevalence of mucous membrane symptoms in single family homes

Microorganisms are known to produce a range of volatile organic compounds, so-called microbial VOC (MVOC). Chamber studies where humans were exposed to MVOC addressed the acute effects of objective and/or subjective signs of mucosal irritation. However, the effect of MVOC on inhabitants due to household exposure is still unclear. The purpose of this epidemiological study was to measure indoor MVOC levels in single family homes and to evaluate the relationship between exposure to them and sick building syndrome (SBS). All inhabitants of the dwellings were given a self-administered questionnaire with standardized questions to assess their symptoms. Air samples were collected and the concentrations of eight selected compounds in indoor air were analyzed by gas chromatography/mass spectrometry — selective ion monitoring mode (GC/MS-SIM). The most frequently detected MVOC was 1-pentanol at a detection rate of 78.6% and geometric mean of 0.60 μg/m³. Among 620 participants, 120 (19.4%) reported one or more mucous symptoms; irritation of the eyes, nose, airway, or coughing every week (weekly symptoms), and 30 (4.8%) reported that the symptoms were home-related (home-related symptoms). Weekly symptoms were not associated with any of MVOC, whereas significant associations between home-related mucous symptoms and 1-octen-3-ol (per log₁₀-unit: odds ratio (OR) 5.6, 95% confidence interval (CI): 2.1 to 14.8) and 2-pentanol (per log₁₀-unit: OR 2.3, 95% CI: 1.0 to 4.9) were obtained after adjustment for gender, age, and smoking. Associations between home-related symptoms and 1-octen-3-ol remained after mutual adjustment. However, concentrations of the selected compounds in indoors were lower than the estimated safety level in animal studies. Thus, the statistically significant association between 1-octen-3-ol may be due to a direct effect of the compounds or the associations may be being associated with other offending compounds. Additional studies are needed to evaluate these possibilities.     

A pilot test plan of the thermochemical water-splitting iodine–sulfur process

Research and development (R&D) of hydrogen production systems using high-temperature gas-cooled reactors (HTGR) are being conducted by the Japan Atomic Research Institute (JAERI). To develop the systems, superior hydrogen production methods are essential. The thermochemical hydrogen production cycle, the IS (iodine–sulfur) process, is a prospective candidate, in which heat supplied by HTGR can be consumed for the thermal driving load. With this attractive feature, JAERI will conduct pilot-scale tests, aiming to establish technical bases for practical plant designs using HTGR. The hydrogen will be produced at a maximum rate of 30 m³/h, continuously using high-temperature helium gas supplied by a helium gas loop, with an electric heater of about 400 kW. The plant will employ an advanced hydroiodic acid-processing device for efficient hydrogen production, and the usefulness of the device was confirmed from mass and heat balance analysis. Through design works and the hydrogen production tests, valuable data for construction and operation will be acquired to evaluate detailed process performance for practical systems. After completing the pilot-scale tests, JAERI will move onto the next R&D step, which will be demonstrations of the IS process to which heat is supplied from a high-temperature engineering test reactor (HTTR).     

Purified Canola Lutein Selectively Inhibits Specific Isoforms of Mammalian DNA Polymerases and Reduces Inflammatory Response

In the screening of DNA polymerase (pol) inhibitor, we isolated lutein, a carotenoid, from the crude (unrefined) pressed oil of canola (low erucic acid rapeseed, Brassica napus L.). Commercially prepared carotenoids such as lutein (1), zeaxanthin (2), β-cryptoxanthin (3), astaxanthin (4), canthaxanthin (5), β-carotene (6), lycopene (7), capsanthin (8), fucoxanthin (9) and fucoxanthinol (10), were investigated for the inhibitory activities of pols. Compounds 1, 2 and 8 exhibited strong inhibition of the activities of mammalian pols β and λ, which are DNA repair- and/or recombination-related pols. On the other hand, all carotenoids tested had no influence on the activity of a mammalian pol α, which is a DNA replicative pol. Lutein (1) was the strongest pol inhibitor of mammalian pols β and λ in the prepared ten carotenoids tested, but did not influence of the activities of mammalian pols α, γ, δ and ε. The tendency for pols β and λ inhibition by these carotenoids showed a positive correlation with the suppression of TPA (12-O-tetradecanoylphorbol-13-acetate)-induced inflammation. These results suggest that cold pressed unrefined canola/rapeseed oil, or other oils with high levels of lutein and other carotenoids, may be useful for their anti-inflammatory properties.     

β-Sitosteryl (6'-O-linoleoyl)-glucoside of soybean (Glycine max L.) crude extract inhibits Y-family DNA polymerases

In the screening of selective DNA polymerase (pol) inhibitors, we isolated an acylated steryl glycoside, β-sitosteryl (6'-O-linoleoyl)-glucoside (compound 1), from the waste extract of soybean (Glycine max L.) oil. This compound exhibited a marked ability to inhibit the activities of eukaryotic Y-family pols (pols η, ι and κ), which are repair-related pols. Among mammalian Y-family pols, the activity of mouse pol κ was most strongly inhibited by compound 1, with an IC(50) value of 10.2 μM. On the other hand, compound 1 had no effect on the activities of other eukaryotic pols such as A-family (pol γ), B-family (pols α, δ, and ε), or X-family (pols β, λ and terminal deoxynucleotidyl transferase) pols. In addition, compound 1 had no effect on prokaryotic pols or other DNA metabolic enzymes such as calf primase of pol α, T7 RNA polymerase, T4 polynucleotide kinase, or bovine deoxyribonuclease I. Compound 1 consists of 3 groups: β-sitosteryl (compound 2), linoleic acid (compound 3), and D-glucose (compound 4). Compound 3 inhibited the activities of all mammalian pols tested, but compounds 2 and 4 did not have any effect on the tested pols. Kinetic studies showed that the inhibition of pol κ activity by compound 1 was noncompetitive with both the DNA template-primer and nucleotide substrate, whereas compound 3-induced inhibition was competitive with the DNA template-primer and noncompetitive with the nucleotide substrate. The relationship between the structure of compound 1 and the selective inhibition of eukaryotic Y-family pols is discussed.     

Heterogeneous nucleation and growth mechanism on hydrophilic and hydrophobic surface

Heterogeneous nucleation and nucleation period of calcium carbonate on the mica and the highly oriented pyrolytic graphite (HOPG) substrate have been investigated. Calcium carbonate was prepared by the reaction of calcium nitrate solution with sodium carbonate solution. In the reaction crystallization of calcium carbonate, calcite and vaterite were nucleated on the both substrates. We counted the number of crystalline calcium carbonate on the substrates obtained from various initial supersaturations of calcium carbonate. The number of crystals on the mica surface was much higher than on the HOPG surface. Additionally, the number of crystals on the mica was greatly affected by changing of initial supersaturation. In order to explain the difference between the mica and the HOPG surface, a possible model for the nucleation period of calcium carbonate has been discussed. The surface crystallization on the mica and the HOPG could be described by considering the supersaturation in the bulk solution and in the vicinity of substrate, separately.