冠带层新平台技术

子午线轮胎出现不久，就采用钢丝带束层代替了纤维带束层，这对于实现子午线轮胎提高使用寿命和改善操纵性能的潜能是必要的。     

A facile chemical synthesis of cholest-4-en-3-one. Carbon-13 nuclear magnetic resonance spectral properties of cholest-4-en-3-one and cholest-5-en-3-one

This paper presents a simplified method for the chemical synthesis of cholest-4-en-3-one, which is a naturally occurring steroid and a salient intermediate in steroid chemistry. Pyridinium chlorochromate (PCC) in refluxing benzene has been found to be an effective and convenient reagent for the oxidation and concomitant isomerization of cholest-5-en-3β-ol (cholesterol) to cholest-4-en-3-one in high yield. Also described are the carbon-13 nuclear magnetic resonance spectral properties of cholest-4-en-3-one and of the isolated reaction intermediate cholest-5-en-3-one. Based on a paper presented at the Symposium on Plant and Fungal Sterols: Biosynthesis Metabolism and function held at the AOCS Annual Meeting, Baltimore, MD, April 1990.     

THERMAL REGENERATION OF ACTIVATED CARBONS

The thermal regeneration of activated carbons loaded with p-nitrophenol (PNP) and other aromatic compounds was studied using a thermal balance. After pyrolysis of the adsorbates in nitrogen at 700°C, the residues were gasified with oxygen at 415 to 500°C or with steam at 840 to 920°C. Residues from PNP were several times more reactive to oxygen than the base carbons and also showed greater chemisorption of oxygen. For steam gasification, only small differences between spent and fresh carbons were found.     

A colorimetric determination of fatty acids as a new assay of lipases in reverse micelles

A new simple spectrophotometric method is described for the determination of the free fatty acid content in triglyceride oils or other lipophilic samples. The method utilizes phenol red as fatty acid indicator, which is solubilized phenol red as fatty acid indicator, which is solubilized in reverse micelles formed by AOT [sodiumbis(2-ethylhexyl) sulfosuccinate] in isooctane. Fatty acid determinations in vegetable oils can be carried out rapidly with oil samples of less than 100 mg. The acid value of three different oils tested agreed quite well with the acid value obtained for the same samples with another colorimetric determination using cupric acetate. The method can be extended to a continuous determination of fatty acids which are released during the initial stage of a lipase catalyzed hydrolysis of triglyceride substrates in reverse micelles. This new sensitive lipase assay has been applied for a lipase ofPseudomonas bacteria with lipase concentrations as low as 0.1 μg/ml. Using trioctanoylglycerol as substrate in 50 mM AOT/isooctane with w_o=[H₂O]/[AOT]=11.1 (pH 9.0), the apparent overall Michaelis-Menten constant (K_m′app,ov) is 27 mM and the turnover number (k_cat) 44 sec⁻¹.     

Liquid Immiscibility in the System K2O-B2O3-SiO2

The subliquidus miscibility gap in the system K₂O-B₂O₃-SiO₂ has been determined for compositions with molar ratios SiO₂/B₂O₃<2 and T≥550°C. The shape of the miscibility gap is an elongated dome similar in form to, but less extensive than those in the lithium and sodium borosilicate systems. The consolute composition (molar) and temperature are estimated to be 4 ± 1 K₂O -30±8 B₂O₃-66±8 SiO₂ and 629±5°C, respectively .     

Optimizing storage performance in public cloud platforms

Cloud computing is an elastic computing model where users can lease computing and storage resources on demand from a remote infrastructure.It is gaining popularity due to its low cost,high reliability,...     

ON THE CHEMICAL OSCILLATIONS IN DIFFERENTIAL REACTORS: A CASE STUDY OF AMMONIA OXIDATION ON PLATINUM

Trying to identify the mechanism(s) responsible for isothermal oscillatory behavior of heterogeneous catalytic reaction systems, many investigators have assumed low conversions with respect to the limiting reactant(s) so that the bulk phase concentrations of the reactants may be considered constant. In this study, it is shown that even in a differential catalytic CSTR, in which conversion of the reactants may be less than %, the changes of the gas phase concentrations of the reacting.species may play a key role in the overall dynamic behavior of a reaction system; for instance, they may drive the oscillations observed. The reduction of nitric oxide by ammonia on polycrystalline platinum is discussed in detail within this context. Several other oxidation reactions are also discussed