低浓度萘在SBA-15上吸附等温线推算

为了获取低挥发性有机物的吸附等温线,基于Langmuir方程,提出一种推算低浓度低挥发性有机物的吸附等温线的方法.脱附活化能由改进的程序升温脱附模型进行动力学分析获得,由此获得的Langmuir方程中的平衡常数B,较经典程序升温脱附模型求算值更接近本征值,且不受是否发生再吸附现象影响;饱和吸附量可结合吸附剂表征结果可得到.此方法应用于低浓度萘在SBA-15上的吸附等温线的推算,脱附活化能为58.37 kJ·mol^-1,平衡常数为0.01149 Pa^-1,饱和吸附量为55.11 mg·g^-1,相对误差约5%,与实验值较好吻合.     

The adsorption of phloretin to lipid monolayers and bilayers cannot be explained by langmuir adsorption isotherms alone

Phloretin and its analogs adsorb to the surfaces of lipid monolayers and bilayers and decrease the dipole potential. This reduces the conductance for anions and increases that for cations on artificial and biological membranes. The relationship between the change in the dipole potential and the aqueous concentration of phloretin has been explained previously by a Langmuir adsorption isotherm and a weak and therefore negligible contribution of the dipole-dipole interactions in the lipid surface. We demonstrate here that the Langmuir adsorption isotherm alone is not able to properly describe the effects of dipole molecule binding to lipid surfaces--we found significant deviations between experimental data and the fit with the Langmuir adsorption isotherm. We present here an alternative theoretical treatment that takes into account the strong interaction between membrane (monolayer) dipole field and the dipole moment of the adsorbed molecule. This treatment provides a much better fit of the experimental results derived from the measurements of surface potentials of lipid monolayers in the presence of phloretin. Similarly, the theory provides a much better fit of the phloretin-induced changes in the dipole potential of lipid bilayers, as assessed by the transport kinetics of the lipophilic ion dipicrylamine.     

抗菌吸附材料的制备及其在再生水处理的应用

以具有良好脱氮效果的改性沸石为原材料,制备抗菌吸附材料.将其用于处理大肠菌群浓度和氨氮含量较高的市政污水厂二级出水结果表明,分别采用银、锌和铜三种金属离子制备抗菌吸附材料,其中银离子的抗菌性能最好,有助于氨氮的去除.最佳制备条件为:AgNO₃用量85mg·g^-1,pH6～7,制备时间120min,制备温度40℃,转速150r·min^-1.优化后材料的载银量为49.79mg·g^-1.将该材料应用于再生水处理,在混合投加抗菌吸附材料0.5g·L^-1和沸石2g·L^-1条件下,反应120min,该材料的杀菌率98.87%,氨氮去除率66.54%,剩余氨氮的质量浓度为8.36mg·L^-1,出水达到城市杂用水水质指标.     

Estimation of specific glucose uptake rates in cultures of hybridoma cells

The specific glucose uptake rate of a hybridoma cell line was determined in batch and continuous suspension cultures. For high density cultivation a membrane dialysis reactor was used. The aim was to obtain data, which can be used for process design and control. A decrease of the specific glucose uptake rate was observed during the course of batch cultures, even when the specific growth rate remained constant. These results are valid for cell densities between 2 x 10(5) and 2 x 10(6) ml-1. At cell densities between 2 x 10(6) and 1.5 x 10(7) ml-1 during continuous cultivation the specific glucose uptake rate remained constant. A relationship between the specific glucose uptake rate and the cell number was found and formulated in a mathematical equation. Literature data for different hybridoma cell lines fit in this plot very well. Applying this relationship, a correct estimation of the course of the glucose concentration in batch and continuous cultivation is possible.     

Astrocytic glutamate uptake and prion protein expression

Factors influencing glutamate uptake by astrocytes may indirectly influence neuronal survival. Elevated extracellular glutamate may be excitotoxic or may exacerbate neurodegeneration in various neurological diseases. By using a cell culture model, we have investigated the influence of astrocytic prion protein (PrPc) expression on glutamate uptake. Type 1 astrocytes expressing PrPc have a higher rate of Na+-dependent glutamate uptake than PrPc-deficient type 1 astrocytes. This difference is exacerbated when serum free media is used to culture the astrocytes. Further analysis suggested that a decrease in substrate affinity is responsible for the sensitivity of PrP-deficient astrocytic glutamate uptake to culture conditions. PrPc has been shown to bind copper. Greater sensitivity of cells to copper concentrations may be responsible for the decreased substrate affinity observed. PrPc-deficient cerebellar cells are more sensitive to glutamate toxicity in the presence of copper. These results show that glutamate uptake from astrocytes is dependent on PrPc expression which in turn may be related to copper metabolism.     

Comparison of continuation rates of intrauterine devices

The optimal heart rate in the immediate period following acute coronary occlusion has been controversial from the standpoint of arrhythmias and the extent of ischaemic injury. In the present study we have examined the effect of heart rate on both local myocardial contractile ability and ischaemia in 10 open chested dogs using strain gauge arches and epicardial electrograms. After sinus node destruction, atrial pacing was instituted for rate control at 100/min and increased randomly to 150, 175, and 200/min. Before coronary occlusion, total tension and rate of tension rise progressively increased at higher rates while ST segments demonstrated no significant changes. After coronary artery occlusion, total tension and rate of tension rise in the ischaemic zone decreased markedly and showed no significant change with increments in pacing rate. In the border zone, after the initial decrease in tension, pacing at 150 beats/min improved tension without a change in ST segments. However, when the rate was increased to 175 and 200 beats/min, although border zone tension increased further, ST segments rose significantly. Thus, a heart rate between 100-150/min provides the optimal range for increasing contractile ability in the nonischaemic and border zones without adversely affecting the degree of ischaemic injury.     

Batch uptake of lysozyme: effect of solution viscosity and mass transfer on adsorption

In this study, solid-phase adsorption by macroporous and hyper-diffusive resins was investigated in a batch uptake adsorption system to quantify solid-phase diffusion rates as a function of bulk phase viscosity. The performance of chromatographic resins used for adsorption of proteins is dependent on several factors including solid and liquid-phase diffusivity, boundary layer mass transfer, and intraparticle mass transfer effects. Understanding these effects is critical to process development and optimization of both packed and fluidized bed adsorption systems. The macroporous resin used here was Streamline SP, and the hyper-diffusive resin was S-HyperD LS. Both have been frequently used in fluidized bed adsorption of proteins; however, factors that affect uptake rates of these media are not well quantified. Adsorption isotherms were well represented by an empirical fit of a Langmuir isotherm. Solid-phase diffusion coefficients obtained from simulations were in agreement with other models for macroporous and hyper-diffusive particles. S-HyperD LS in the buffer system had the highest uptake rate, but increased bulk phase viscosity decreased the rate by approximately 50%. Increases in bulk phase viscosity increased film mass transfer effects, and uptake was observed to be a strong function of the film mass transfer coefficient. Uptake by Streamline SP particles was slower than S-HyperD in buffer, due to a greater degree of intraparticle mass transfer resistance. The effect of increased film mass transfer resistance coupled with intraparticle mass transfer resistances at an increased bulk phase viscosity resulted in a decrease of 80% in the uptake rate by Streamline SP relative to S-HyperD.     

Aortic cross-clamping influences regional net release and uptake rates of tissue-type plasminogen activator in pigs

BACKGROUND: The key regulator of intravascular fibrinolysis, tissue-type plasminogen activator (t-PA), is released from a dynamic endothelial storage pool. The aim of the study was to investigate regional t-PA net release and uptake rates in response to infra-renal aortic cross-clamping (AXC) and declamping (DC). METHODS: Anesthetized pigs were studied during 5 min of AXC, followed by a 35-min declamping (DC) period. Arterio-venous concentration gradients of total and active t-PA, as well as respective plasma flows, were simultaneously obtained across the preportal, hepatic, coronary and pulmonary vascular beds. Plasma levels of total t-PA (ELISA with purified porcine t-PA as standard), and active t-PA (spectrophotometric functional assay) were determined. RESULTS: Prior to AXC, we found a high net release rate of total t-PA across the preportal vascular bed (1700 ng.min-1 P < 0.001), and a high hepatic net uptake (4900 ng.min-1, P < 0.001), while coronary and pulmonary t-PA net fluxes were small and variable. AXC per se did not induce significant alterations in net fluxes of t-PA. Following DC, preportal and coronary net releases of total t-PA increased (to 2900 ng.min-1 and 60 ng.min-1, respectively). Despite an increase in hepatic net uptake of total t-PA (to 6100 ng.min-1) after DC, a significant increase in hepatic venous total t-PA occurred. CONCLUSIONS: The release and uptake of t-PA is indicated to be dynamic and organ-specific. DC induces an acute profibrinolytic reaction in preportal organs. The high hepatic t-PA uptake capacity restricts preportal profibrinolytic events to affect the systemic circulation.     

Experimental investigation of dissolution rates of carbonaceous materials in liquid iron-carbon melts

Interactions of carbonaceous materials in liquid Fe-C melts have been investigated experimentally by determining the rates of dissolution at temperatures ranging from 1623 to 1935 K. The rates of dissolution of spectroscopic graphite and an industrial coke obeyed the correlation for natural convection under turbulent conditions. The experimental data for the graphite suggested that the rate of dissolution was controlled by mass transfer in liquid boundary layer adjacent to the solid sample. The value of the empirical parameter correlating the dissolution coefficient and the operating variables was found to be 0.19, which was close to that reported in the literature. The comparison of the results obtained for coke and low-volatile coal char samples with those for the graphite revealed that impurities and porosity of the samples can effect the dissolution rates. The values ofk ₁, for coke decreased with increasing the dissolution time. The examination of some of the partially dissolved coke samples by electron micro-scopy revealed that a thin, viscous ash layer was forming on the sample surface, which must be the main reason for the behavior. The dissolution rates were controlled by both mass transfer and phase boundary reactions when sulfur was present in the bath. The extent of devolatilization and dissolution of coal particles when they were injected into an Fe-C melt depended on the particle size and location. Formerly Visiting Professor, Massachusetts Institute of Technology. Formerly with the Department of Materials Science and Engineering, Massachusetts Institute of Technology Formerly with the Department of Materials Science and Engineering, Massachusetts Institute of Technology, is deceased.     

提金活性炭吸附材料的制备与研究现状

活性炭因具有优异的吸附性能和来源广泛等特点,在黄金工业提金工艺生产中得到广泛应用.总结了提金活性炭制备材料、结构性能的研究现状,介绍了活性炭的制备方法及活化手段,其中活化手段主要分为物理活化法、化学活化法和物理-化学联合活化法,且化学活化法效果最佳、应用最为广泛.阐述了氰化浸金体系和非氰浸金体系提金活性炭的应用现状及新...     

新型功能介孔材料的合成及其对铅离子吸附性能研究

2O3-3 %CaF2-KCl体系的初晶温度,并对测定数据进行回归分析,得到初晶温度的回归方程。研究结果表明,在铝电解质中添加氯化钾能够降低电解质的初晶温度。本文旨在获得铝电解质初晶温     

Excretion and uptake of putrescine by the PotE protein in Escherichia coli

The structure and function of the polyamine transport protein PotE was studied. Uptake of putrescine by PotE was dependent on the membrane potential. In contrast, the putrescine-ornithine antiporter activity of PotE studied with inside-out membrane vesicles was not dependent on the membrane potential (Kashiwagi, K., Miyamoto, S., Suzuki, F., Kobayashi, H., and Igarashi, K. (1992) Proc. Natl. Acad. Sci. U. S. A. 89, 4529-4533). The Km values for putrescine uptake and for putrescine-ornithine antiporter activity were 1.8 and 73 microM, respectively. Uptake of putrescine was inhibited by high concentrations of ornithine. This effect of ornithine appears to be due to putrescine-ornithine antiporter activity because it occurs only after accumulation of putrescine within cells and because ornithine causes excretion of putrescine. Thus, PotE can function not only as a putrescine-ornithine antiporter to excrete putrescine but also as a putrescine uptake protein. Both the NH2 and COOH termini of PotE were located in the cytoplasm, as determined by the activation of alkaline phosphatase and beta-galactosidase by various PotE-fusion proteins. The activities of putrescine uptake and excretion were studied using mutated PotE proteins. It was found that glutamic acid 207 was essential for both the uptake and excretion of putrescine by the PotE protein and that glutamic acids 77 and 433 were also involved in both activities. These three glutamic acids are located on the cytoplasmic side of PotE, and the function of these three residues could not be replaced by other amino acids. Putrescine transport activities did not change significantly with mutations at the other 13 glutamic acid or aspartic acid residues in PotE.