Crystallographic report: Bis(O‐methoxyethyldithiocarbonato)(4,7‐dimethyl‐1,10‐phenanthroline)cadmium(II)

The structure of mononuclear Cd(S₂COCH₂CH₂OCH₃)₂(4,7‐Me₂phen) shows an N₂S₄ donor set about cadmium that defines a coordination geometry intermediate between octahedral and trigonal prismatic. Copyright © 2003 John Wiley & Sons, Ltd.     

Crystallographic report: Chloro(N,N‐diethyldithiocarbamato)(4,7‐dimethyl‐1, 10‐phenanthroline)mercury(II) hemi‐chloroform solvate

The X‐ray crystal structure of Hg(S₂CNEt₂)(4,7‐Me₂‐phen)Cl features an essentially four‐coordinate geometry for mercury within a ClN₂S donor set that defines a distorted tetrahedral arrangement. Copyright © 2003 John Wiley & Sons, Ltd.     

Crystallographic report: Bis[bis(N,N‐dibenzyldithiocarbamato)zinc(II)](4,4′‐bipyridine)

The centrosymmetric structure of {Zn[S₂CN(CH₂Ph)₂]₂}₂(4,4′‐bipy) features chelating dithiocarbamate ligands so that a trigonal bipyramidal NS₄ coordination geometry for zinc results. Copyright © 2003 John Wiley & Sons, Ltd.     

Crystallographic report: Bis(N,N‐dibenzyldithiocarbamato)mercury(II)

The monomeric structure of Hg[S₂CN(CH₂Ph)₂]₂, in which the mercury atom lies on a two fold axis that relates the unsymmetrically chelating dithiocarbamate ligands, features a severely distorted tetrahedral geometry. Copyright © 2004 John Wiley & Sons, Ltd.     

Complex economic dynamics: Chaotic saddle, crisis and intermittency

Complex economic dynamics is studied by a forced oscillator model of business cycles. The technique of numerical modeling is applied to characterize the fundamental properties of complex economic systems which exhibit multiscale and multistability behaviors, as well as coexistence of order and chaos. In particular, we focus on the dynamics and structure of unstable periodic orbits and chaotic saddles within a periodic window of the bifurcation diagram, at the onset of a saddle-node bifurcation and of an attractor merging crisis, and in the chaotic regions associated with type-I intermittency and crisis-induced intermittency, in non-linear economic cycles. Inside a periodic window, chaotic saddles are responsible for the transient motion preceding convergence to a periodic or a chaotic attractor. The links between chaotic saddles, crisis and intermittency in complex economic dynamics are discussed. We show that a chaotic attractor is composed of chaotic saddles and unstable periodic orbits located in the gap regions of chaotic saddles. Non-linear modeling of economic chaotic saddle, crisis and intermittency can improve our understanding of the dynamics of financial intermittency observed in stock market and foreign exchange market. Characterization of the complex dynamics of economic systems is a powerful tool for pattern recognition and forecasting of business and financial cycles, as well as for optimization of management strategy and decision technology.     

Interaction of Dipalmitoyl Phosphatidylcholine with n‐Hexadecanol in Monolayer and Liposome

The monolayer collapse behavior of n‐hexadecanol/dipalmitoyl phosphatidylcholine (DPPC) was investigated in this study at the air/water interface at 37 °C. Surface pressure variations with time for the mixed monolayers of DPPC with 20 mol% and 50 mol% n‐hexadecanol at corresponding collapse points were recorded by a Langmuir trough system. In addition, the interaction of n‐hexadecanol with a pure DPPC monolayer was identified by fluorescence microscopy (FM). The results demonstrated distinct differences between these systems; according to our observation, the higher the ratio of n‐hexadecanol to DPPC, the more nucleation domains can be induced. The FM images demonstrated that pronounced domain formation was associated with a longer relaxation time of the collapsed DPPC and DPPC/n‐hexadecanol monolayers, and the presence of n‐hexadecanol appeared to enhance the relaxation processes. The liposome was prepared by the thin‐film hydration method. The average diameter of DPPC and DPPC/n‐hexadecanol liposomes was investigated by dynamic light scattering. It is shown that the diameter of DPPC liposome with n‐hexadecanol is smaller than pure DPPC liposome at the initial state. After 24 hours, DPPC/n‐hexadecanol liposome became larger than pure DPPC liposome and lasted for the next four days. The effects of a greater ratio of n‐hexadecanol did not play an important role in DPPC liposome formation based on our dynamic light scattering analysis. Our result demonstrated that n‐hexadecanol might affect the DPPC liposome stability. The increased ratio of n‐hexadecanol in DPPC liposomes could only a play a minor role in DPPC liposome fusion.     

一类可压缩超弹性柱体中微孔的径向增长

研究了一类可压缩超弹性材料组成的柱体在给定的径向拉伸作用下预存微孔的增长问题.利用能量变分原理将此类问题的数学模型归结为一个二阶非线性常微分方程的边值问题,并通过变数变换求得了方程的参数型解析解,得到了微孔的增长与给定的拉伸之间的精确关系.通过相应的数值算例,解释了材料参数和结构参数对微孔增长的影响,分析了柱体中应力的分布及径向位移的变化情况.     

Solids flow diagram of a CFB riser using Geldart B-type powders

Riser operating modes are vital to designing a circulating fluidized bed (CFB) reactor for a required process of either a gas-solid or a gas-catalytic nature. Different operating modes provide different solids’ residence times and mixing behaviors, which define the reactions’ efficiency and yield. The literature demonstrates distinct operating modes resulting from observed differences in slip factors and the range of particle velocities and their associated residence time distribution. The present research uses positron emission particle tracking (PEPT) in a riser of B-type bed material to determine the different operating modes by measuring (i) particle velocities and residence time distribution, (ii) population densities of these particles in the cross-sectional area of the riser, and (iii) solids flow pattern at the bottom of the riser. Data treatment defines four distinct solids hold-up regimes in the riser and proposes a "phase diagram" depicting the existence of the different operating modes (dilute, dense, core-annulus and combined) as a function of the superficial gas velocity and solids circulation flux in the riser. The delineated regimes have good agreement with available literature data and known industrial operations. Comparison with literature data for risers using A-type powders is also fair. The diagram enables CFB designers to better delineate operating characteristics.     

Characterization of Major and Minor Organic Pollutants in Wastewaters from Coal Gasification Processes

Abstract

In order to investigate the feasibility of anaerobic biological treatment for wastewaters generated from thermal gasification processes of coal, a characterization program was implemented whose major effort consisted in the elucidation of specific organic constituents contained in the wastewater. Solvent extraction in acid and base conditions followed by glass capillary gas chromatography in combination with several detectors (i.e., FID, NPD, and MS-DS) were employed for the investigation of major and minor “extractable” organic constituents. Direct aqueous injection on a polar glass capillary column (i.e., OV-351) was used for the major “nonsolvent extractable” organic constituents amenable to GC. The identity of 28 organic compounds was confirmed by comparison with pure standards. Phenol, the three cresol isomers, 5,5-dimethyl-hydantoin and 5-methyl,5-ethylhydantoin were identified as major wastewater constituents. Several substituted phenols (e.g., methyl, dimethyl, trimethyl, methylethyl, hydroxy and methoxy), pyridines, anilines, quinolines, PAHs, dibenzofuran and aldehydes were either confirmed or tentatively identified as minor wastewater constituents. Although the organics identified did not account for the total organic content, which implies the presence of still unidentified highly polar compounds, the information was utilized to set a data base for monitoring the biological treatment operations. Process monitoring data indicated that several organics (i.e., 5,5-dimethyl-hydantoin, 5-methyl,5-ethylhydantoin, o-cresol, m-cresol and p-cresol) were only partially removed by the treatment process employed.