Adsorption of N-2, Ar, acetone, chloroform and acetone-chloroform mixture on carbon black in the framework of molecular layer structure theory (MLST)

Adsorption of pure nitrogen, argon, acetone, chloroform and acetone-chloroform mixture on graphitized thermal carbon black is considered at sub-critical conditions by means of molecular layer structure theory (MLST). In the present version of the MLST an adsorbed fluid is considered as a sequence of 2D molecular layers, whose Helmholtz free energies are obtained directly from the analysis of experimental adsorption isotherm of pure components. The interaction of the nearest layers is accounted for in the framework of mean field approximation. This approach allows quantitative correlating of experimental nitrogen and argon adsorption isotherm both in the monolayer region and in the range of multi-layer coverage up to 10 molecular layers. In the case of acetone and chloroform the approach also leads to excellent quantitative correlation of adsorption isotherms, while molecular approaches such as the non-local density functional theory (NLDFT) fail to describe those isotherms. We extend our new method to calculate the Helmholtz free energy of an adsorbed mixture using a simple mixing rule, and this allows us to predict mixture adsorption isotherms from pure component adsorption isotherms. The approach, which accounts for the difference in composition in different molecular layers, is tested against the experimental data of acetone-chloroform mixture (non-ideal mixture) adsorption on graphitized thermal carbon black at 50 degrees C. (C) 2005 Elsevier Ltd. All rights reserved.

Effects of potential models in the vapor-liquid equilibria and adsorption of simple gases on graphitized thermal carbon black

In this paper, we investigate the effects of various potential models in the description of vapor–liquid equilibria (VLE) and adsorption of simple gases on highly graphitized thermal carbon black. It is found that some potential models proposed in the literature are not suitable for the description of VLE (saturated gas and liquid densities and the vapor pressure with temperature). Simple gases, such as neon, argon, krypton, xenon, nitrogen, and methane are studied in this paper. To describe the isotherms on graphitized thermal carbon black correctly, the surface mediation damping factor introduced in our recent publication should be used to calculate correctly the fluid–fluid interaction energy between particles close to the surface. It is found that the damping constant for the noble gases family is linearly dependent on the polarizability, suggesting that the electric field of the graphite surface has a direct induction effect on the induced dipole of these molecules. As a result of this polarization by the graphite surface, the fluid–fluid interaction energy is reduced whenever two particles are near the surface. In the case of methane, we found that the damping constant is less than that of a noble gas having the similar polarizability, while in the case of nitrogen the damping factor is much greater and this could most likely be due to the quadrupolar nature of nitrogen.

Equilibrium adsorption in cylindrical mesopores: A modified Broekhoff and de boer theory versus density functional theory

This paper presents a thermodynamic analysis of capillary condensation phenomena in cylindrical pores. Here, we modified the Broekhoff and de Boer (BdB) model for cylindrical pores accounting for the effect of the pore radius on the potential exerted by the pore walls. The new approach incorporates the recently published standard nitrogen and argon adsorption isotherm on nonporous silica LiChrospher Si-1000. The developed model is tested against the nonlocal density functional theory (NLDFT), and the criterion for this comparison is the condensation/evaporation pressure versus the pore diameter. The quantitative agreement between the NLDFT and the refined version of the BdB theory is ascertained for pores larger than 2 nm. The modified BdB theory was applied to the experimental adsorption branch of adsorption isotherms of a number of MCM-41 samples to determine their pore size distributions (PSDs). It was found that the PSDs determined with the new BdB approach coincide with those determined with the NLDFT (also using the experimental adsorption branch). As opposed to the NLDFT, the modified BdB theory is very simple in its utilization and therefore can be used as a convenient tool to obtain PSDs of all mesoporous solids from the analysis of the adsorption branch of adsorption isotherms of any subcritical fluids.

Synthesis, characterization and X-ray crystal structures of dinuclear nickel(II) complexes of a novel potentially hexadentate but functionally tetradentate binucleating ligand

A binucleating potentially hexadentate chelating agent containing oxygen, nitrogen and sulfur as potential donor atoms (H2ONNO) has been synthesized by condensing alpha,alpha-xylenebis(N-methyldithiocarbazate) with 2,4-pentanedione. An X-ray crystallographic structure determination shows that the Schiff base remains in its ketoimine tautomeric form with the protons attached to the imine nitrogen atoms. The reaction of the Schiff base with nickel(II) acetate in a 1:1 stoichiometry leads to the formation of a dinuclear nickel(II) complex [Ni(ONNO)](2) (ONNO2- = dianionic form of the Schiff base) containing N,O-chelated tetradentate ligands, the sulfur donors remaining uncoordinated. A single crystal X-ray structure determination of this dimer reveals that each ligand binds two low spin nickel(II) ions, bridged by a xylyl group. The nickel(II) atoms adopt a distorted square-planar geometry in a trans-N2O2 donor environment. Reaction of the Schiff base with nickel(II) acetate in the presence of excess pyridine leads to the formation of a similar dinuclear complex, [Ni(ONNO)(py)](2), but in this case comprises five coordinate high-spin Ni(II) ions with pyridine ligands occupying the axial coordination sites as revealed by X-ray crystallographic analysis. (c) 2005 Published by Elsevier B.V.

Comparison of beam theory and finite-element analysis with in vivo bone strain data from the alligator cranium

The mechanical behavior of the vertebrate skull is often modeled using free-body analysis of simple geometric structures and, more recently, finite-element (FE) analysis. In this study, we compare experimentally collected in vivo bone strain orientations and magnitudes from the cranium of the American alligator with those extrapolated from a beam model and extracted from an FE model. The strain magnitudes predicted from beam and FE skull models bear little similarity to relative and absolute strain magnitudes recorded during in vivo biting experiments. However, quantitative differences between principal strain orientations extracted from the FE skull model and recorded during the in vivo experiments were smaller, and both generally matched expectations from the beam model. The differences in strain magnitude between the data sets may be attributable to the level of resolution of the models, the material properties used in the FE model, and the loading conditions (i.e., external forces and constraints). This study indicates that FE models and modeling of skulls as simple engineering structures may give a preliminary idea of how these structures are loaded, but whenever possible, modeling results should be verified with either in vitro or preferably in vivo testing, especially if precise knowledge of strain magnitudes is desired. (c) 2005 Wiley-Liss, Inc.

Adsorption in slit pores and pore-size distribution: A molecular layer structure theory

A new approach is developed to analyze the thermodynamic properties of a sub-critical fluid adsorbed in a slit pore of activated carbon. The approach is based on a representation that an adsorbed fluid forms an ordered structure close to a smoothed solid surface. This ordered structure is modelled as a collection of parallel molecular layers. Such a structure allows us to express the Helmholtz free energy of a molecular layer as the sum of the intrinsic Helmholtz free energy specific to that layer and the potential energy of interaction of that layer with all other layers and the solid surface. The intrinsic Helmholtz free energy of a molecular layer is a function (at given temperature) of its two-dimensional density and it can be readily obtained from bulk-phase properties, while the interlayer potential energy interaction is determined by using the 10-4 Lennard-Jones potential. The positions of all layers close to the graphite surface or in a slit pore are considered to correspond to the minimum of the potential energy of the system. This model has led to accurate predictions of nitrogen and argon adsorption on carbon black at their normal boiling points. In the case of adsorption in slit pores, local isotherms are determined from the minimization of the grand potential. The model provides a reasonable description of the 0-1 monolayer transition, phase transition and packing effect. The adsorption of nitrogen at 77.35 K and argon at 87.29 K on activated carbons is analyzed to illustrate the potential of this theory, and the derived pore-size distribution is compared favourably with that obtained by the Density Functional Theory (DFT). The model is less time-consuming than methods such as the DFT and Monte-Carlo simulation, and most importantly it can be readily extended to the adsorption of mixtures and capillary condensation phenomena.

Long-term flow rates and biomat zone hydrology in soil columns receiving septic tank effluent

Soil absorption systems (SAS) are used commonly to treat and disperse septic tank effluent (STE). SAS can hydraulically fail as a result of the low permeable biomat zone that develops on the infiltrative surface. The objectives of this experiment were to compare the hydraulic properties of biomats grown in soils of different textures, to investigate the long-term acceptance rates (LTAR) from prolonged application of STE, and to assess if soils were of major importance in determining LTAR. The STE was applied to repacked sand, Oxisol and Vertisol soil columns over a period of 16 months, at equivalent hydraulic loading rates of 50, 35 and 8 L/m(2)/d, respectively Infiltration rates, soil matric potentials, and biomat hydraulic properties were measured either directly from the soil columns or calculated using established soil physics theory. Biomats 1 to 2 cm thick developed in all soils columns with hydraulic resistances of 27 to 39 d. These biomats reduced a 4 order of magnitude variation in saturated hydraulic conductivity (K.) between the soils to a one order of magnitude variation in LTAR. A relationship between biomat resistance and organic loading rate was observed in all soils. Saturated hydraulic conductivity influenced the rate and extent of biomat development. However, once the biomat was established, the LTAR was governed by the resistance of the biomat and the sub-biomat soil unsaturated flow regime induced by the biomat. Results show that whilst initial soil K. is likely to be important in the establishment of the biomat zone in a trench, LTAR is determined by the biomat resistance and the unsaturated soil hydraulic conductivity, not the K, of a soil. The results call into question the commonly used approach of basing the LTAR, and ultimately trench length in SAS, on the initial K, of soils. (c) 2006 Elsevier Ltd. All rights reserved.

Finite deformation model of simple shear of fault with microrotations: apparent strain localisation and en-echelon fracture pattern

Strain localisation is a widespread phenomenon often observed in shear and compressive loading of geomaterials, for example, the fault gouge. It is believed that the main mechanisms of strain localisation are strain softening and mismatch between dilatancy and pressure sensitivity. Observations show that gouge deformation is accompanied by considerable rotations of grains. In our previous work as a model for gouge material, we proposed a continuum description for an assembly of particles of equal radius in which the particle rotation is treated as an independent degree of freedom. We showed that there exist critical values of the model parameters for which the displacement gradient exhibits a pronounced localisation at the mid-surface layers of the fault, even in the absence of inelasticity. Here, we generalise the model to the case of finite deformations characteristic for the gouge deformation. We derive objective constitutive relationships relating the Jaumann rates of stress and moment stress to the relative strain and curvature rates, respectively. The model suggests that the pattern of localisation remains the same as in the linear case. However, the presence of the Jaumann terms leads to the emergence of non-zero normal stresses acting along and perpendicular to the shear layer (with zero hydrostatic pressure), and localised along the mid-line of the gouge; these stress components are absent in the linear model of simple shear. These additional normal stresses, albeit small, cause a change in the direction in which the maximal normal stresses act and in which en-echelon fracturing is formed.

Synthesis and evaluation of asperlicin analogues as non-peptidal cholecystokinin-antagonists

The SAR of Asperlicin analogues is reported, leading to bioactive 1,4-benzodiazepine-2-ones, which were prepared in a 3 step reaction sequence. The Asperlicin substructure was built up using Tryptophan and readily available 2-amino-acetophenones. This template, containing a 1,4-benzodiazepin-2-one moiety with a 3-indolmethyl side chain, was transformed into mono- and di-substituted 3-indol-3 '-yl-methyl-1,4-benzodi-azepine-2-ones by selective alkylation and acylation reactions. The SAR optimization of the 1,4-benzodiazepine scaffold has included variations at the 5-, 7-, 8-position, at the N1, N-indole nitrogen and the configuration of the C3-position. The most active Asperlicin analogue, having an IC50 of 1.6 microM on the CCKA receptor subtype, was obtained from Tryptophan in only 3 steps in an overall yield of 48%.

Mobile phone and e-government in Turkey:practices and technological choices at the cross-road

Enhanced data services through mobile phones are expected to be soon fully transactional and embedded within future mobile consumption practices. While private services will surely continue to take the lead, others such as government and NGOs will become more prominent m-players. It is not yet sure which form of technological standards will take the lead including enhance SMS based operations or Internet based specifically developed mobile phone applications. With the introduction of interactive transactions via mobile phones, currently untapped segment of the populations (without computers) have the potential to be accessed. Our research, as a reflection of the current market situation in an emerging country context, in the case of mobile phones analyzes the current needs or emergence of dependencies regarding the use of m/e-government services from the perspective of municipality officers. We contend that more research is needed to understand current preparatory bottlenecks and front loading activities to be able to encourage future intention to use e-government services through mobile phone technologies. This study highlights and interprets the current emerging practices and praxis for consuming m-government services within government.

Genetic and environmentally derived variation in the cell wall composition of miscanthus and implications for thermo-chemical conversion

Fifteen Miscanthus genotypes grown in five locations across Europe were analysed to investigate the influence of genetic and environmental factors on cell wall composition. Chemometric techniques combining near infrared reflectance spectroscopy and conventional chemical analyses were used to construct calibration models for determination of acid detergent lignin, acid detergent fibre, and neutral detergent fibre from sample spectra. The developed equations were shown to predict cell wall components with a good degree of accuracy and significant genetic and environmental variation was identified. The influence of nitrogen and potassium fertiliser on the dry matter yield and cell wall composition of M. x giganteus was investigated. A detrimental affect on feedstock quality was observed to result from application of these inputs which resulted in an overall reduction in concentrations of cell wall components and increased accumulation of ash within the biomass. Pyrolysis-gas chromatography-mass spectrometry and thermo-gravimetric analysis indicates that genotypes other than the commercially cultivated M. x giganteus have potential for use in energy conversion processes and in the bio-refining. The yields and quality parameters of the pyrolysis liquids produced from Miscanthus compared favourably with that produced from SRC willow and produced a more stable pyrolysis liquid with a higher lower heating value. Overall, genotype had a more significant effect on cell wall composition than environment. This indicates good potential for dissection of this trait by QTL analysis and also for plant breeding to produce new genotypes with improved feedstock characteristics for energy conversion.