Fenarimol,a Pyrimidine-Type Fungicide,Inhibits Brassinosteroid Biosynthesis

The plant steroid hormone brassinosteroids (BRs) are important signal mediators that regulate broad aspects of plant growth and development. With the discovery of brassinoazole (Brz), the first specific inhibitor of BR biosynthesis, several triazole-type BR biosynthesis inhibitors have been developed. In this article, we report that fenarimol (FM), a pyrimidine-type fungicide, exhibits potent inhibitory activity against BR biosynthesis. FM induces dwarfism and the open cotyledon phenotype of Arabidopsis seedlings in the dark. The IC₅₀ value for FM to inhibit stem elongation of Arabidopsis seedlings grown in the dark was approximately 1.8 ± 0.2 μM. FM-induced dwarfism of Arabidopsis seedlings could be restored by brassinolide (BL) but not by gibberellin (GA). Assessment of the target site of FM in BR biosynthesis by feeding BR biosynthesis intermediates indicated that FM interferes with the side chain hydroxylation of BR biosynthesis from campestanol to teasterone. Determination of the binding affinity of FM to purified recombinant CYP90D1 indicated that FM induced a typical type II binding spectrum with a K_d value of approximately 0.79 μM. Quantitative real-time PCR analysis of the expression level of the BR responsive gene in Arabidopsis seedlings indicated that FM induces the BR deficiency in Arabidopsis.     

Genome Mining of the Hitachimycin Biosynthetic Gene Cluster: Involvement of a Phenylalanine‐2,3‐aminomutase in Biosynthesis

Hitachimycin is a macrolactam antibiotic with (S)‐β‐phenylalanine (β‐Phe) at the starter position of its polyketide skeleton. To understand the incorporation mechanism of β‐Phe and the modification mechanism of the unique polyketide skeleton, the biosynthetic gene cluster for hitachimycin in Streptomyces scabrisporus was identified by genome mining. The identified gene cluster contains a putative phenylalanine‐2,3‐aminomutase (PAM), five polyketide synthases, four β‐amino‐acid‐carrying enzymes, and a characteristic amidohydrolase. A hitA knockout mutant showed no hitachimycin production, but antibiotic production was restored by feeding with (S)‐β‐Phe. We also confirmed the enzymatic activity of the HitA PAM. The results suggest that the identified gene cluster is responsible for the biosynthesis of hitachimycin. A plausible biosynthetic pathway for hitachimycin, including a unique polyketide skeletal transformation mechanism, is proposed.     

Change in the Thermal Expansion of a Perovskite-Type Mixed Conductor Upon Sample Density

Thermal expansions (TEs) of dense and porous samples were studied for mixed conductor Sr(Co_0.9Nb_0.1)O_3−δ (SCNb). In Ar, the TEs of the porous samples were almost the same as those of a dense sample, which had the character of conventional TEs. In air, on the other hand, the TEs of porous samples were larger than the dense sample. The difference of TE in air resulted from a change in the chemical expansion, which originated from the variation of oxygen vacancy concentration. On decreasing the density, oxygen incorporation from air into SCNb took place at a lower temperature, and the length change upon chemical expansion was increased.     

Effects of a Single and Short-Term Ingestion of Diacylglycerol on Fat Oxidation in Rats

This study examines the effect of diacylglycerol (DAG) oil consisting mainly of 1,3-species on fat oxidation as a possible mechanism for anti-obesity. We examined the following: (1) the long-term (23-week) effects of a DAG oil diet on the development of obesity; (2) the effect of a single ingestion of DAG oil on fat oxidation; and, (3) the short-term (2-week) effect of a DAG oil diet on fat metabolism in rats. Rats fed a DAG oil diet accumulated significantly less body fat compared to rats fed a triacylglycerol (TAG) oil diet, each oil possesses a similar fatty acid composition. More ¹⁴C-CO₂ was expired and less ¹⁴C-radioactivity was incorporated into visceral fat after administration of a tracer emulsion containing 1,3-[oleoyl-1-¹⁴C] diolein compared to [carboxyl-¹⁴C] triolein. Indirect calorimetry showed respiratory quotients were significantly lower in the DAG oil diet group than in the TAG oil diet group. More ¹⁴C-CO₂ was expired and less ¹⁴C-radioactivity was incorporated into visceral fat in the DAG oil diet group than in the TAG oil diet group after a single intragastric administration of [carboxyl-¹⁴C] triolein. These results suggest the following. (1) DAG oil has an inhibitory effect on diet-induced fat accumulation. (2) 1,3-DAG, a major component of DAG oil, is more susceptible to oxidation. (3) A short-term ingestion of DAG oil increases fat utilization at the whole body level and results in increased oxidation of dietary fat. The stimulated fat oxidation might be one explanation for the anti-obesity effect of long-term DAG oil ingestion.     

Viscoelastic evaluation of effects of fiber size and composition on cellulose‐polypropylene composite of high filler content

In wood/plastic composite of high wood filler content, filler dispersion in resin is important which determines mobility of compound and mechanical properties of products. This work reports on the dispersion of components in compound by evaluation of viscoelasticity using a cone rheometer. The effects of size of cellulose fiber and resin content on viscoelasticity were analyzed, and the dispersion of cellulose is discussed to reach the following conclusions: The viscoelasticity measured by a cone rheometer was dependent on the dispersion state of compound, and evaluation of viscoelasticity affords the evidence for dispersion state of filler in compound; On the basis of viscoelastic evaluation of compound with different resin content, a model for dispersion of cellulose and resin with tangle of fiber is proposed; Viscoelastic analysis showed that cellulose size has influence on tangle of fiber, and results of viscoelasticity and mechanical properties of mold products suggested that an important factor determining tangle of fiber is its average aspect ratio. The proposed analysis of viscoelasticity presents a new technique for estimating the dispersion state of compound of high filler content which is hardly accessible by conventional fluid evaluation methods. The present method is simple and useful for quality control in manufacture. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers     

Electronic‐Type‐ and Diameter‐Dependent Reduction of Single‐Walled Carbon Nanotubes Induced by Adsorption of Electron‐Donor Molecules

The adsorption of the organic donor molecules tetrakis(dimethylamino)ethylene (TDAE) and cobaltocene (CoCp₂) on high‐pressure CO decomposition (HiPco) single‐walled carbon nanotubes (SWNTs) is investigated using density functional theory (DFT), optical absorption, and Raman spectra methods. The selective reduction of SWNTs according to the electronic type and diameter of SWNTs is revealed. The reduction rate decreases in the order: metallic SWNTs ≥ large‐diameter semiconducting SWNTs > small‐diameter semiconducting SWNTs.     

超声波共振度对铸锭内气孔生成的影响

为了弄清超声波对金属熔体除气的影响,研究了超声波共振度对Al-1．0%Cu、Al-1．0％Si及Al-1．0％Zn合金铸锭内气孔生成的影响,同时也考察了超声波共振度对铝合金铸锭细化的影响,分析了超声波共振度时铸锭内气孔生成的影响原因。结果表明,超声波处于共振状态下的铸锭密度值和细化效果均远大于非共振状态下的铸锭密度值和细化效果;超声处理过程中,声空化气泡的“表面效应”和“层效应”起着决定作用;超声波的细化作用来自于声空化气泡的膨胀和收缩期间而形成的高温、高压的反应场,因而刺激熔体内的动态形核。     

六氯乙烷预处理对超声波处理铸锭内气孔的影响

研究六氯乙烷脱气剂对超声波处理铸锭内气孔的影响.结果表明,超声波处理的初期,添加六氯乙烷脱气剂的金属熔体,超声脱气效果明显,随后与未添加六氯乙烷脱气剂的情况相比差异逐渐缩小,接近凝固时两者均会导致铸锭内气孔的增加.添加脱气剂有助于改善后续的超声波除气效果.     

Elastic modulus and bend strength of a nuclear graphite at high temperature

The elastic modulus of a nuclear graphite was measured in the range from room temperature to 1400°C by the ultrasonic pulse echo method. Little or no change in the elastic modulus was observed up to 450°C. Above 500°C, however, it increased almost linearly with increasing temperature. The fractional increase was about 10% at 1000°C and 24% at 1400°C. The four-point bend test was also measured at temperatures between room temperature and 1200°C. Changes in bend strength with temperature were found to parallel to those of the elastic modulus. The mechanism for the correlation between the bend strength and the elastic modulus, as well as the effect of moisture on the strength, was discussed.     

Fabrication and Evaluation of Al2O3–AgCl–Agl Composites by Use of Electrochemical Deposition

Al₂O₃–AgCl–AgI composites were fabricated by an electrochemical deposition technique utilizing porous α–Al₂O₃ ceramics as a matrix. The growth process was presumed to be dominated by the diffusion rate of the Ag⁺ ion. The phases identified in the composites were α-Al₂O₃, AgCl, and β-AgI. The deposited AgCl and AgI showed enhanced conductivity compared with the reported bulk values. The deposited mixture exhibited enhanced conductivity compared with pressed polycrystalline AgCl or AgI. The enhancement was explained using a model that a deposit with a high conductivity grows much faster than that with a low conductivity.