Characterization of a convection-based support microstructure through a flow resistance parameter

Modern convection-based supports differ substantially in pore size, porosity, and microstructure topology. Due to such variability, it is challenging to evaluate the contribution of a particular microstructure topology on flow resistance. We demonstrated that the flow resistance parameter ($\varphi$) introduced decades ago can be used as a criterion to evaluate the effect of microstructure topology on a pressure drop when the pore size is used as a characteristic support dimension. Furthermore, the $\varphi$ value of simple cubic packing was calculated over the entire range of open porosity and compared to the $\varphi$ values determined for pressure drop models derived for particular convection-based supports and experimental values of various convection-based supports from the literature. It was shown that different convection-based supports become clustered into distinct groups when plotted according to their $\varphi$ and open porosity values, allowing their discrimination.     

Flux decline behaviors in dead-end microfiltration of activated sludge and its supernatant

The properties of dead-end microfiltration were explored under constant pressure using two types of activated sludge controlled under the condition of different air flow rates. The activated sludge cultured at the air flow rate of 0.15 L min⁻¹ (the anaerobic condition) exhibited a significant flux decline compared with the case of the air flow rate of 2.33 L min⁻¹ (the aerobic condition). It was found from the results of microfiltration of the supernatant separated by centrifugation that the constituents in the supernatant caused a major cake resistance in microfiltration of the activated sludge. The average specific filtration resistance for filtration of the activated sludge was closely consistent with that for filtration of the supernatant at low pressure (49 kPa). However, the cake resistance of the microbial floc in microfiltration of the activated sludge became substantial with increasing filtration pressure because of high compressibility of the microbial floc. Moreover, the foulant and the fouling mechanism in microfiltration of the supernatant were evaluated from both microfiltration test of the supernatant and microfiltration test of the filtrate collected thereby. As a result, the effects of the pore size and material of the microfiltration membrane on the flux decline behaviors in dead-end microfiltration were reasonably elucidated.     

Ab initio calculations ofp-Cl2C6H4 molecule and its35Cl NQR parameters

Ab initio calculations ofp-dichlorobenzene molecule were carried out using the Hartree-Fock method in the 6–31 G* valence-split basis set. The molecule was also calculated by the MNDO method in the valence sp-basis set for comparison. The populations of the valent p-orbitals of the C and CI atoms were analyzed. The optimized geometry of the molecule as well as its³⁵Cl NQR frequency and the asymmetry parameter of the electric field gradient at the³⁵CI nuclei calculated using the populations of the less diffuse components of the valent p-orbitals of the Cl atoms are in agreement with the corresponding experimental values for the -modification of 1,4-Cl₂C₆H₄.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2177–2179, September, 1996.     

Sr／Ca比变化对红色荧光粉Ca1-xSrxS：Eu^2＋的影响

在CO气氛下采用固相反应法合成了发红光的Ca1-xSrxS:Eu^2 荧光粉，研究了基质阳离子Sr／Ca比变化对其晶体性质及发光性能的影响。结果表明，随着Sr／Ca比的减少，荧光粉的晶胞参数逐渐降低；同时，由于受电子云膨胀效应和晶体场影响，发射主峰向长波方向移动，红色比逐渐增大，色纯度提高。     

Cation-crown ether complex formation in water. II. Alkali and alkaline earth cations and 12-crown-4, 15-crown-5, and 18-crown-6

The stability constants and the partial molal volume and isentropic partial molal compressibility changes of complex formation between cations and crown ethers in water at 25°C are presented. The cations involved are Na⁺, K⁺, Rb⁺, Cs⁺, Ca²⁺, and Ba²⁺, and the crown ethers are 12-crown-4, 15-crown-5, and 18-crown-6. Values of V of complex formation have been discussed in terms of two simple models, one based on the scaled particle theory, and the others on the Drude-Nernst continuum model. The results indicate that the charge of the potassium cation in 18-crown-6 is especially well screened from the water. On this basis hydration numbers of complexed cations have been calculated. This shows that the size of the cation compared to the crown ether hole is important for the contacts between complexed cations and water.     

The effect of high pressure on the ion pair equilibrium constant of alkali metal fluorides: A spectrophotometric study

Bromophenol blue indicator was used in UV-visible spectrophotometric measurements to study ion association constants of alkali metal fluorides. The equilibrium constants for the ion pair formation of the alkali metal fluorides were determined as a function of ionic strength at one atmosphere pressure and 25°C. The effect of pressure on these association constants was measured at a constant total ionic strength of 1.0 mol-kg^–1 over a pressure range of 1 to 2000 atmospheres at 25°C. The pressure dependences of the stoichiometric association constants of the alkali metal fluorides are given by: lnK _LiF ^* =0.77–2.47×10^–4P–2.12×10^–8P²; lnK _NaF ^* =0.53–1.08×10^–4P–1.66×10^–8P²; lnK _KF ^* =0.24–4.41×10^–5P–7.15×10^–8P²; lnK _RbF ^* =–0.17–8.65×10^–5P–4.51×10^–8P²; and lnK _CsF ^* = –0.37–1.14×10^–4P–6.82×10^–8P², where P is the pressure in atmospheres. The stoichiometric molar volume and compressibility changes for ion pair formation of the alkali metal fluorides were evaluated from the pressure dependence of K _MF ^* data. The thermodynamic association constants were also calculated making use of activity coefficient data from the Pitzer equations. The partial molal volume and compressibility changes for ion pair formation of each alkali metal fluoride are reported.     

基本参数法在能量色散X射线荧光分析金属样品中的应用

在X射线荧光分析中,基本参数法是校正元素间吸收增强效应的数学方法之一。我们使用带有不锈钢窗的~(241)Am59.6keVγ射线作为激发源,用Si(Li)半导体探测器和多道脉冲幅度分析器作为实验手段。采用无标样法,即绝对测量法,因而具有更大的广泛性和实用性。实验中,我们除了考虑元素间的二次、三次荧光吸收增强作用外,对样品中元素     

The effect of pressure on the dissociation constant of hydrofluoric acid and the association constant of the NaF ion pair at 25°C

The effect of pressure on the dissociation constant of hydrofluoric acid was determined by using the indicator technique at 25°C at an ionic strength of 0.1m over a pressure range of 1 to 2000 atm. A value of 3.14 for pK _a ^* at I =0 was obtained by extrapolation to zero ionic strength at 1 atm. The pressure dependence yielded a partial molar volume change of –9.6 cm³-mol^–1 and a compressibility change of — 35×10^–3 cm³-mol^–1 –atm^–1 for the dissociation. The dependence of ionic strength on the association constant K _A ^* of NaF was studied at 25°C and 1 atm. Extrapolation to I=0 yielded a pK _A ^* of –0.78. The pressure dependence of K _A ^* gave a change of volume of 3.26 cm³-mol^–1 and a change in compressibility of 6×10^–3 cm³-mol^–1-atm^–1 for the formation of the ion pair.     

Artificial red cells with crosslinked hemoglobin membranes

Artificial cells containing concentrated hemoglobin (Hb) solution were prepared by interfacial polymerization of Hb with glutaraldehyde (GA) in liquid membrane capsules (LMC). A solution containing 30% of Hb was emulsified in mineral oil as red cell-size microdroplets, and this emulsion was dispersed in an aqueous phase containing glutaraldehyde to form LMC. The LMC were semipermeable templates that held the microdroplets of Hb in suspension while GA diffused through the oil to the microdroplet surfaces. The GA crosslinked Hb at the surface of each microdroplet to form an artificial red-cell membrane encapsulating Hb solution. A water-soluble surfactant was used to eject the cells from the LMC and suspend them in saline. Several surfactants were evaluated. Cell size was controlled by agitation speed during preparation of the original emulsion. Cells of 2.52 = ±1.69 μm were prepared. The encapsulated Hb retained capacity to bind and release O₂. The cells had aP ₅₀ of 8.9 torr (1200 Pa) and a capacity of 0.55 cc O₂/g of total Hb, indicating that the crosslinked portion of the Hb did not contribute to O₂ transport.     

Isentropic partial molal compressibilities of alcohols in propylene carbonate at 25°C

The isentropic coefficients of compressibility of the homologous series of alcohols and diols R _n CH₂OH (n=2–6), CH₃CHOHR _n (n=1–5), 1,2-propanediol, 1,3- 1,4- and 2,3-butanediol, 1,5-pentanediol, and 1,7-heptanediol dissolved in propylene carbonate have been measured at 25°C. Isentropic partial molal compressibilities and group partial molal compressibilities at infinite dilution have been evaluated. The isentropic partial molal compressibilities of these alcohols and diols have been compared with the corresponding values in water. This comparison shows that the values in propylene carbonate are higher than in water by a factor of 10 due to an increased compressibility of the solvation sheath around nonpolar groups in PC.