0412-1961

本文提出在非晶态合金的形成中,元素的原子半径采用实测的原子间距之半来衡量。在总结归纳大量实验资料的基础上发现二元或多元非晶态合金,其组成元素的尺寸因素(ΔR/R_i)都大于9％(个别例外)。分析了影响形成二元非晶态合金的因素,得到了形成二元非晶态合金的必要条件为:     

Protein-nucleic acid recognition: simulation of base and "model" amino acids complexes in DMSO by the Monte Carlo method

Phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis catalyzes the hydrolysis of phosphatidylinositol (PI) in discrete steps: (i) an intramolecular phosphotransferase reaction to form inositol 1,2-(cyclic)-phosphate (cIP), followed by (ii) a cyclic phosphodiesterase activity that converts cIP to inositol 1-phosphate. Water-soluble cIP was used as the substrate to study the cyclic phosphodiesterase activity and interfacial behavior of PI-PLC. Different detergent micelles and phospholipid vesicles were used to examine if "interfacial activation" of the enzyme could occur toward a soluble substrate. Almost all detergents examined activated the enzyme at least 2-fold, with PC species yielding the largest increases in PI-PLC specific activity. Kinetic parameters were measured in the absence and presence of several representative detergents (e.g., Triton X-100 and diheptanoylphosphatidylcholine (diC7PC)). Gel filtration experiments showed that, under these conditions, the cIP did not partition to any measurable extent with these detergent micelles. The concentration at which half the maximum activation was observed occurred near the detergent CMC. Both Km and Vmax were altered by the presence of a surface: Km decreased to different degrees depending on the detergent, while Vmax increased substantially. The Km for cIP was 90 mM without detergent and decreased to 29 mM with diC7PC micelles added; Vmax increased almost 7-fold in the presence of diC7PC micelles. The enzyme efficiency (Vmax/Km) in the presence of diC7PC increased more than 21-fold, but it was still 20-fold lower than initial phosphotransferase activity for monomeric dihexanoylphosphatidylinositol. The poor efficiency of the cyclic phosphodiesterase activity is largely due to substrate binding affinity. The dependence of rate on substrate concentration exhibits cooperative behavior, especially without detergent. This cooperativity is discussed in terms of protein aggregation and ligand binding sites on the enzyme.     

白于山井区长4 5_2油组储层沉积微相研究

通过对构造背景、岩心、古生物特征、测井资料的综合分析,查明了鄂尔多斯盆地白于山井区长4 52油组的沉积特征和沉积微相的平面展布规律,认为白于山井区长4 52油组储集体发育的是一套三角洲前缘亚相砂体,其沉积微相可进一步划分为水下分流河道、河口砂坝、远砂坝和支流间湾微相。根据不同沉积微相的测井响应特征,研究了沉积相在平面上的分布特征,并总结出研究区的相层序。     

Signal standardization of the secondary ion mass spectrometry (SIMS) microscope for quantification of halogens and calcium in biological applications

The secondary ion mass spectrometry (SIMS) microscope is able to map chemical elements in tissue sections. Although absolute quantification of an element remains difficult, a relative quantitative approach is possible for soft tissue by using carbon (¹²C) as an internal reference present at large homogeneous and constant concentration in specimen and embedding resin. In this study, this approach is used to standardize the signal of an SIMS microscope for the quantification of halogens (¹⁹F^—, ³⁵Cl^— and ⁷⁹Br^—) and calcium (⁴⁰Ca⁺). Standard preparation was determined based on homogeneity and stability criteria by molecular incorporation (halogens) or mixing (calcium) in methacrylate resin. Standard measurements were performed by depth analysis on areas of 8 μm (halogens) and 150 μm (calcium) in diameter for 10–30 min, under Cs⁺ (halogens) or O₂⁺ (calcium) bombardment. Results obtained from 100–120 measurements for each standard dilution show that the relationship between the signal intensity measured and the elemental concentration (μg/mg of wet tissue or mm ) is linear in the range of biological concentrations. This quantitative approach was applied firstly to bromine of the 5-bromo-2′-deoxyuridine (BrdU) used as nuclear marker of rat hepatocytes in proliferation. The second model concerns depletion of calcium concentration in cortical compartment in Paramecium tetraurelia during exocytosis. Then signal standardization in SIMS microscopy allows us to correlate quantitative results with those obtained from other methods.     

一种基于变结构的预测控制算法及其应用研究

将变结构控制方法引入预测控制中，提出了一种基于变结构的预测控制算法。与传统的预测控制方法相比，该算法具有设计简单、易于实现的优点。将其应用于火电机组过热汽温控制进行仿真研究，结果表明所提出的预测控制算法具有优良的控制性能和很好的鲁棒性。     

Influence of solvents on the photoinduced birefringence in chitosan films incorporating azo dyes

The photoinduced birefringence arising from trans–cis–trans isomerization has been studied in chitosan cast films doped with the azo dye Ponceau‐S. The chitosan/Ponceau‐S films are highly resistant to several solvents, which allowed the study of their optical storage features after immersion in various solvents. We demonstrate that the induced birefringence and its dynamics are influenced by the solvent. From experiments using such different solvents as water, dimethylsulfoxide, ethylene glycol, methanol and chloroform, it was found that the induced birefringence and the writing rate increase linearly with the dielectric constant of the solvent. At high dielectric constant, photoinduced molecular reorientation is facilitated, leading both to a larger birefringence and faster dynamics. Copyright © 2007 Society of Chemical Industry     

Effects of different calcium salts on properties of milk related to heat stability

Insoluble calcium salts were added to milk to increase total calcium by 30 mM, without changing properties influencing heat stability, such as pH and ionic calcium. There were no major signs of instability associated with coagulation, sediment formation or fouling when subjected to ultra high temperature (UHT) and in‐container sterilisation. The buffering capacity was also unaltered. On the other hand, addition of soluble calcium salts reduced pH, increased ionic calcium and caused coagulation to occur. Calcium chloride showed the largest destabilising effect, followed by calcium lactate and calcium gluconate. Milk became unstable to UHT processing at lower calcium additions compared to in‐container sterilisation.     

安森美半导体16W xDSL调制解调器AC-DC适配器参考设计

文章介绍了安森美半导体用于xDSL调制解调器AC—DC适配器的一种经过完备构建及测试的Green Point^TM解决方案。     

A comparison of the nasal mask and the nasopharyngeal airway in paediatric chair dental anaesthesia

This study compared the quality of anaesthesia and surgical access afforded by two techniques for the administration of anaesthesia during paediatric chair dental procedures. A total of 50 ASA 1 paediatric day case patients were randomly assigned to receive anaesthesia through either the traditional Goldman nasal mask or through a nasopharyngeal airway. Patients in the nasal mask group were judged to have significantly worse airway patency (p = 0.0001) and significantly more episodes of airway obstruction (14 vs. 4; p = 0.0032) than those in the nasopharyngeal airway group. Anaesthetic, surgical and oxygen saturation data did not differ significantly between the two groups. Operating conditions were universally graded as excellent in the nasopharyngeal airway group, while those in the nasal mask group were graded as excellent/good in only 79% of cases (p < 0.0001). These results suggest that better quality anaesthesia and operating conditions can be achieved by using a nasopharyngeal airway rather than the traditional nasal mask for the administration of anaesthesia to paediatric chair dental patients.