Acoustic resonator transducer for operation in air

An acoustic resonator and electronic system for operation in air are described. The transducer operates in a resonant mode and can be utilised to measure the distance between the transducer and a reflecting object. Experimental results are presented for a 275 kHz resonator transducer that can measure distances with better than 0.5 ?m resolution at a 0.6 mm range. Applications to noncontacting surface profile measurements are also demonstrated.     

Hyperproduction of L-threonine by an Escherichia coli mutant with impaired L-threonine uptake

An efficient production strain for L-threonine fermentation was derived from Escherichia coli by multiple rounds of mutation programs that aimed at deregulation of the L-threonine biosynthetic pathway and blocking of L-threonine degradation pathways. When the optimum amount of DL-methionine was added, this strain KY10935, an L-methionine auxotroph, gave 100 g/liter L-threonine after 77 h cultivation. In this strain, key enzymes in the L-threonine biosynthetic pathway were highly derepressed, but some were inhibited by lower concentrations of L-threonine than the accumulated level. Such incomplete deregulation of the pathway was accounted for by the intracellular concentration of L-threonine being lower than the extracellular level. In an assessment of L-threonine transport in terms of phenotypic growth responses to the amino acid, L-threonine-auxotrophic mutants with a lesion in the L-threonine operon were derived from strain KY10935 by selection for auxotrophy for dipeptide L-alanyl-L-threonine or glycyl-L-threonine, the transport systems of which were different from those of L-threonine. All three independent mutants isolated needed an extraordinarily high concentration (10 mg/ml) of L-threonine, but grew in the presence of a low concentration (10 micrograms/ml) of either dipeptide, indicating that strain KY10935 had impaired L-threonine uptake. These results suggested that the strain had an unusual mechanism of L-threonine hyperproduction: the inability to take up L-threonine that had accumulated extracellularly decreased the steady-state level of intracellular L-threonine, freeing the remaining regulatory steps of feedback inhibition.     

Synthesis of Poly(alcohol)s by Hydroboration/Oxidation of Poly(methylallene) Prepared by π-Allylnickel-Catalyzed Living Coordination Polymerization

Summary The π-allylnickel-catalyzed living coordination polymerization of methylallene gave polymers with predictable molecular weight and narrow molecular weight distribution in high yields. The polymers possessing various microstructural units (i.e., the ratio of the 1,2- and the 2,3-polymerizations), produced by varying the nature of the catalyst and the solvents, were subjected to the hydroboration with borane reagents such as borane tetrahydrofuran complex (BH₃•THF) and 9-borabicyclo[3.3.1]nonane (9-BBN). Subsequent oxidation gave poly(alcohol)s whose hydroxy-content could be varied by the borane reagents used. For example, the quantitative conversion of the double bonds in poly(methylallene) into the hydroxy group was attained by the hydroboration using an excess amount of BH₃•THF. Thermal properties of poly(alcohol)s were found to be dependent upon the microstructure and the hydroxy-content of the polymers.     

Continuous degradation of dimethyl sulfoxide to sulfate ion by Hyphomicrobium denitrificans WU-K217

With the objective of removing dimethyl sulfoxide (DMSO) contained in wastewater from semiconductor or liquid crystal display factories, biodegradation of DMSO, particularly at a low concentration, was examined. Through the screening of DMSO-degrading microorganisms, Hyphomicrobium denitrificans WU-K217 utilizing DMSO as the sole source of carbon was isolated from soil. DMSO at less than 20 mM was degraded to sulfate ion by WU-K217 with 100% molar conversion ratio based on DMSO added during 60-h cultivation at 30 degrees C under aerobic conditions. Even in the presence of 116 mM or 225 mM DMSO, WU-K217 showed growth although the amount of DMSO degraded was only 33 mM or 10 mM, respectively. Similar to the growing cells, the resting cells of WU-K217 degraded DMSO at over a wide range of temperature, 20-40 degrees C. The highest DMSO-degradation activity was obtained at 30 degrees C, and 0.64 mM (50 mg/l) DMSO was completely degraded to sulfate ion with 100% molar conversion ratio within only 15 min. Furthermore, to examine whether WU-K217 would be useful for the removal of DMSO contained in wastewater exhausted in large amounts, continuous degradation of DMSO was examined. When 0.64 mM DMSO was added to the resting cells periodically at 15-min intervals, DMSO was completely degraded to sulfate ion without any decrease of the degradation activity at least during the twelve times of DMSO addition.     

Simulation verification for the robustness of passive compass gait with a joint stiffness adjustment

A passive walking robot can achieve a smooth gait without any sensory feedback while walking down a slope. This phenomenon is based on the transformation of potential energy into kinetic energy in the legs. Although the entrainment is observed in a passive gait motion, there is a possibility that the passive gait cannot be achieved in the case of variations in physical parameters, initial conditions, and disturbances. To realize a robust passive gait against variations in physical parameters, this paper proposes a passive gait system that possesses a joint stiffness adjustment. Targeting a compass model, this paper investigates the effectiveness of the proposed method for a passive gait against variations in slope angle and hip joint mass through simulation. As a result, the simulation results show that this method especially has strong robustness against the slope angle variation.     

Crack propagation life prediction of a perforated plate under thermal fatigue

Superheater outlet headers of boilers are well known to be subjected to the cycling of high pressure and high thermal stress during plant operations. Thermal stresses during cyclic operation are generally severest on the inside surface of the ligaments between the stub-tube holes, where many examples of ligament cracking due to thermal fatigue have been found recently. A method to predict the crack propagation life of the ligaments of boiler headers under thermal fatigue has been required. Firstly in this paper, to model the crack propagation behavior of the ligament regions of boiler headers, a perforated plate of normalized and tempered 2 1/4Cr–1Mo steel was examined under out-of-phase thermal fatigue at a maximum temperature of 600°C in the air. Inelastic analysis of the perforated plate under thermal fatigue was carried out, and the nonlinear fracture mechanics parameters such as the J and C^* integral were obtained by the line integral for observed cracks. A simplified method was proposed for predicting these parameters under displacement-controlled conditions such as thermal fatigue. In this method, the change of the macroscopic stress–strain relation of the perforated plate with propagating cracks was combined with the reference stress concept under displacement-controlled conditions. The predicted fracture mechanics parameters from this method coincided well with those from the inelastic analysis. The prediction of the crack propagation life on the basis of the proposed method provided a good correspondence with the test results of the perforated plate under thermal fatigue.     

Synthesis of π-conjugated polymers possessing 1,3-butadiene-1,4-diyl units by reactions of regioregular organometallic polymer having titanacyclopentadiene moieties in the main chain

The synthesis and properties of π-conjugated polymers possessing phenylene-1,4-diyl and 1,3-butadiene-1,4-diyl alternating units in the main chain by reactions of a regioregular organometallic polymer having titanacyclopentadiene-2,5-diyl unit are described. The polymerization of 1,4-diethynyl-2,5-dioctyloxybenzene with a low-valent titanium complex, generated in situ from titanium(IV) isopropoxide and isopropyl magnesium chloride, was carried out at ?78 °C to ?50 °C for 12 h to give the regioregular organotitanium polymer. The diene-containing π-conjugated polymers were obtained by the reactions of the organotitanium polymer with electrophiles such as hydrochloric acid and iodine. For example, the reaction with hydrochloric acid gave a diene-containing polymer in a 61% yield whose M_n and M_w/M_n were estimated as 5700 and 1.61, respectively (by GPC). The π-conjugated character of the resulting polymer could be supported by its UV–vis spectrum. That is, the absorption maximum (λ_max) of the polymer was observable at 470 nm, which was bathochromically shifted by 115 nm compared to that of a model compound (1,4-bis(2-methoxyphenyl)-1,3-butadiene, λ_max = 355 nm).     

Gene cloning and characterization of Mycobacterium phlei flavin reductase involved in dibenzothiophene desulfurization

Mycobacterium phlei WU-F1 possesses the ability to convert dibenzothiophene (DBT) to 2-hydroxybiphenyl with the release of inorganic sulfur over a wide temperature range from 20 degrees C to 50 degrees C. The conversion is initiated by consecutive sulfur atom-specific oxidations by two monooxygenases, and a flavin reductase is essential in combination with these flavin-dependent monooxygenases. The flavin reductase gene (frm) of M. phlei WU-F1, which encodes a protein of 162 amino acid residues with a molecular weight of 17,177, was cloned and the deduced amino acid sequence shares approximately 30% identity with those of several flavin reductases in two protein-component monooxygenases. It was confirmed that the coexpression of frm with the DBT-desulfurization genes (bdsABC) from M. phlei WU-F1 was critical for high DBT-desulfurizing ability over a wide temperature range from 20 degrees C to 55 degrees C. The frm gene was overexpressed in Escherichia coli cells, and the enzyme (Frm) was purified to homogeneity from the recombinant cells. The purified Frm was found to be a 34-kDa homodimeric protein with a monomeric molecular mass of 17 kDa. Frm exhibited high flavin reductase activity over a wide temperature range, and in particular, the turnover rate for FMN reduction with NADH as the electron donor reached 564 s(-1) at 50 degrees C, which is one of the highest activities among all of the flavin reductases previously reported. Intriguingly, Frm also exhibited a high ferric reductase activity.     

Alpha-anomer-selective glucosylation of menthol with high yield through a crystal accumulation reaction using lyophilized cells of Xanthomonas campestris WU-9701

L-Menthyl alpha-D-glucopyranoside (alpha-MenG) is a desirable derivative of L-menthol with useful properties for the production of new flavors and novel food additives. Bacteria were screened for alpha-anomer-selective glucosylation activity toward l-menthol, resulting in the isolation of two strains, Xanthomonas campestris WU-9701 and Stenotrophomonas maltophilia WU-9702, from independent soil samples. Since the safety of X. campestris for use in the food industry is well established, WU-9701 was selected as the more suitable strain for further study. When 50 mg X. campestris WU-9701 lyophilized cells as a biocatalyst were incubated with 1.0 M maltose and 100 mg L-menthol in 10 ml of 10 mM H3BO3NaOHKCl buffer (pH 8.0) at 40 degrees C, alpha-MenG was accumulated, mainly in a crystalline form, through the anomer-selective synthesis reaction without any by-product formation. Under the optimal conditions, 202 mg alpha-MenG was obtained over 48 h with a highest conversion yield of 99.1% based on the supplied L-menthol. Crude alpha-MenG formed through this "crystal accumulation reaction" was easily collected from the reaction mixture by separation on filter paper. Plank-like crystals of purified alpha-MenG were subsequently obtained by recrystallization in ethyl acetate solution.