Cyclic variations in the permeability of the cell wall of Saccharomyces cerevisiae.

To study cell-cycle-related variations in wall permeability of Saccharomyces cerevisiae, two approaches were used. First, an asynchronous culture was fractionated by centrifugal elutriation into subpopulations containing cells of increasing size. The subpopulations represented different stages of the cell cycle as judged by light microscopy. Cell wall porosity increased when these subpopulations became enriched with budded cells. Secondly, synchronous cultures were obtained by releasing MATa cells from alpha-factor induced G1-arrest. These cultures grew synchronously for at least two generations. The cell wall porosity increased sharply in these cultures, shortly before buds became visible and was maximal during the initial stages of bud growth. It decreased in cells which had completed nuclear migration and before abscission of the bud had occurred. The porosity reached its lowest value during abscission and in unbudded cells. We examined the incorporation of mannoproteins into the wall during the cell cycle. SDS-extractable mannoproteins were incorporated continuously. However, the incorporation of glucanase-extractable mannoproteins, which are known to affect cell wall porosity, showed cyclic oscillations and reached its maximum after nuclear migration. This coincided with a rapid decrease in cell wall porosity, indicating that glucanase-extractable mannoproteins might contribute to this decrease.     

Consideration on Effective Diffusivity of Strontium in Granite

Abstract

Diffusive behavior of strontium and certain kinds of divalent cations in Inada granite were studied by a through-diffusion method. In order to examine the effect of sorption onto overall diffusive behavior, two kinds of solutions were used: 0.1M KCl solution and deionized water. The effective diffusion coefficient (D_e ) and rock capacity factor (a) were (2.0–3.6) xl0–¹³ m²/s and less than 0.022 in 0.1M KCl solution and (0.32–1.7) x 10 ^?13m²/s and 1.5–2.4 in deionized water respectively. The D_e , and α in deionized water were much larger than those in 0.1M KCl solution. These results are well explained by taking into account the diffusion of sorbed ion or the surface diffusion. In support of this mechanism, most D_e , values of Sr reported for various rocks are found proportional to the sorptivity ( _ρR_d )-In the case that the sorptivity is low, D_e of Sr depends on porosity like that of nonsorbed iodide. The effective diffusion coefficient of Sr in rocks was well explained by taking into account pore and surface diffusion and was expressed as D_e=2.1 xl0^?10 _? ^1.3+3.5xl0″^?12 _ρR_d . The effective diffusion coefficient of divalent cations in the granite was found proportional to their diffusion coefficients in bulk solution.     

活性氧化铝开发及建议

本文报道了粉状活性氧化铝、型体活性氧化铝的研究开发状况.开发活性氧化铝既低碳、环保,又有良好的经济效益、环保效益、社会效益.     

元素俘获测井在库车深层致密砂岩中的应用

库车前陆盆地深层砂岩气藏表现为低孔隙度特低渗透率特征,由于钻井取心少,评价复杂岩性储层存在困难。元素俘获测井(ECS)利用矿物成分获取地层岩性和骨架参数,能够指导评价复杂岩性地层。利用元素俘获测井获取的元素干重百分比,建立反演矿物模型求取矿物的含量。用ECS测井资料获得的矿物含量计算地层变骨架密度(地层骨架密度随深度变化而变化),再计算地层孔隙度,其孔隙度结果与岩心孔隙度基本吻合,验证了ECS测井技术求取地层孔隙度方法的可靠性。对库车前陆盆地深层7口井已知数据的验证,提高了地层孔隙度的解释精度。实践表明,ECS测井技术用于求取塔里木盆地库车深层致密砂岩地层中的储层参数,取得了很好的应用效果。     

利用神经网络的LM算法确定碳酸盐岩声波孔隙度

确定碳酸盐岩声波孔隙度是测井解释中的一个难题，传统方法是利用平均时差公式经过适当校正或使用声波、中子、密度等两种以上的测井资料求取，在具体使用中误差较大且很不方便。为此，基于Levenberg—Marquardt算法，提出一种确定碳酸盐岩声波孔隙度的神经网络方法，主要步骤包括：样本信息的预处理、网络结构的设计、采用LM算法的网络学习训练、碳酸盐岩声波孔隙度的确定。仿真实验和比较分析表明，该方法快速稳定，其结果与真实值吻合程度高。     

西西伯利亚含油气省北部侏罗系油气藏的渗容特征随埋深的变化规律

在侏罗系油气藏地区划分和对大量分析资料(约8000有效孔隙度和粒间渗透率样品)分析的基础上,阐明了侏罗系粒状储集层的渗容特征,并查明了它们随埋藏深度而变化的规律。指出,侏罗系油藏储集层总的特点是具有中、低孔隙度和较低、低的渗透率。在区域性的油气藏中,牛津阶和巴统阶具有最大的渗容值,而阿林巴依奥斯阶和托阿尔阶的渗容值较低,普林斯巴赫和赫唐- 辛涅缪尔阶渗容值最低,而生产层Ю11- Ю14、Ю2、Ю3 层的特点是中等孔隙度和中等、较低的渗透率。油气藏储集层的渗容值取决于储集层的埋深,上侏罗统砂具有中等有效孔隙度和粒间渗透率,孔隙度由14.2%降至 11.2%,粒间渗透率由 19.62×10-3μm2,降至 236×10-3μm2,而下侏罗统在2750—3750m,有效孔隙由 14.8%降至7%,粒间渗透率由7.90×10-3μm2 降至 0.03×10-3μm2,4250m以下,侏罗系粒状储集层的分布空间有限,其含油气远景可能与欠压实次生作用和裂隙型储集层的发育带有关。随着储集层埋深的加大,渗容值降低,这主要与上覆地层压力作用下的压实作用有关。     

Permeability Measurements of Porous Food Materials

Permeability of air through porous pre-gelatinized flour dough was measured as a function of porosity (0.10–0.60), moisture content (15–50%, wet basis), and fat content (0–6%). At free stream velocities <2 cm/sec, flow rate and pressure drop followed Darcy's law for flow through porous media. Permeability values ranged from 0.02 darcies at 0.10 porosity to about 23 darcies at 0.60 porosity. Permeability of dough does not follow the Kozeny model for granular materials, possibly due to differences in tortuosity between dough and granular materials. Moisture content <50% and fat content to 6% did not directly affect permeability.     

间隙对5754铝合金激光填丝搭接焊气孔的影响

气孔是5754铝合金激光搭接焊接过程中经常出现的缺陷,它对焊缝的机械性能有很大的影响。实验采用光纤激光器研究了在搭接铝合金板间设置间隙对气孔的影响及其机理,发现,间隙的设置为气孔的逃逸提供了一个通道,气孔率有明显减小的趋势。当间隙从0变化到0.2mm时,由于间隙较小而有毛细现象的发生,搭接间隙气孔的逃逸通道被液态焊缝金属的凝固过程封闭,气孔减小并不明显;当间隙从0.30mm变化到0.75mm时,由于间隙增大,间隙部位的焊缝液态金属发生的毛细现象减弱甚至消失,导致这部分金属距离熔合线很近,表面保持液态,气孔逃逸的通道被打开,气孔有明显减小的变化。实验还发现,随着间隙的增大,搭接焊缝的剪切强度有了很大的提高。     

格栅孔隙率对某空调室外机性能影响的CFD研究

为了满足建筑物外观的要求,通常采用格栅将空调室外机的安装阳台密封起来。然而,格栅孔隙率的大小将直接影响机组的通风与换热性能。本文运用数值模拟的方法对某室外机周围的流场进行计算,研究格栅孔隙率对机组性能的影响。计算结果表明,增大格栅的孔隙率将会增加阳台的通流能力,有效降低盘管的进风温度。在实例中,当格栅孔隙率从0.25增加到0.64时,通过格栅的流量百分比将从35.2%增大到108.4%;为了满足该机组正常运行的要求,格栅的孔隙率应该大于0.6。     

淀粉替代剂在双胶纸中的应用

探讨了淀粉替代剂部分替代淀粉进行表面施胶,使双胶纸质量有一定提高,并降低了生产成本。实验表明,当淀粉替代剂替代比例为20%时,方案最佳,吨纸成本可节约22.09元,胶液成膜性比未使用替代剂要好,而且成纸的表面强度和裂断长分别比未使用替代剂时提高21%（正面）/17%（反面）和24%,透气度也有所降低,平滑度与之前相当,表面施胶剂烷基烯酮二聚体（AKD）的用量比未使用替代剂时节约3.1 kg/t（纸）。