Packing effects on argon and methanol adsorption inside graphitic cylindrical and slit pores: a GCMC simulation study

Using Grand Canonical Monte Carlo simulation, we have studied the effects of confinement on argon and methanol adsorption in graphitic cylindrical and slit pores. Linear chain, zigzag and incomplete helical packing are observed for argon adsorption in cylindrical pores. However, for methanol adsorption different features appear because the electrostatic interactions favour configurations that maximize the hydrogen bonding among methanol molecules. We have found zigzag chains with hydrogen-bonded structures for methanol adsorption in cylindrical and slit pores. To investigate how dense the adsorbed phase is and how many molecules could be packed per unit physical volume of the solid, we consider two different definitions of pore density; one based on the physical volume and the other on the accessible volume. That based on accessible volume gives a measure of the fluid density, while that based on the physical volume gives a measure of how much adsorbate can be stored per unit volume of the adsorbent. It is found that the adsorbate is denser in cylindrical pores, but that slit pores can pack more molecules per unit solid volume. We also discuss the effects on the isosteric heat of argon and methanol of pore size, pore geometry and loading.     

Application of kinetic Monte Carlo method to equilibrium systems: vapour-liquid equilibria

Kinetic Monte Carlo (kMC) simulations were carried out to describe the vapour-liquid equilibria of argon at various temperatures. This paper aims to demonstrate the potential of the kMC technique in the analysis of equilibrium systems and its advantages over the traditional Monte Carlo method, which is based on the Metropolis algorithm. The key feature of the kMC is the absence of discarded trial moves of molecules, which ensures larger number of configurations that are collected for time averaging. Consequently, the kMC technique results in significantly fewer errors for the same number of Monte Carlo steps, especially when the fluid is rarefied. An additional advantage of the kMC is that the relative displacement probability of molecules is significantly larger in rarefied regions, which results in a more efficient sampling. This provides a more reliable determination of the vapour phase pressure and density in case of non-uniform density distributions, such as the vapour-liquid interface or a fluid adsorbed on an open surface. We performed kMC simulations in a canonical ensemble, with a liquid slab in the middle of the simulation box to model two vapour-liquid interfaces. A number of thermodynamic properties such as the pressure, density, heat of evaporation and the surface tension were reliably determined as time averages.     

A biphenylene-bridged dinuclear constrained geometry titanium complex for ethylene and ethylene/1-octene polymerizations

Permethylated cyclopentadienyl dinuclear constrained geometry titanium catalyst, [μ-(C₆H₄)₂-2,2′]{(η⁵-C₅Me₃)[1-Me₂Si(η¹-N-^tBu)](TiCl₂)}₂ (BPTi₂) linked by a biphenylene bridge was synthesized and tested in ethylene and ethylene/1-octene polymerizations upon activation by TIBA (triisobutylaluminum)/[Ph₃C][B(C₆F₅)₄]. When compared with the corresponding highly active, mononuclear analogs, Me₂Si(η⁵-2-PhC₅Me₃)(η¹-N-^tBu)TiCl₂ (PhTi₁) and Me₂Si(η⁵-C₅Me₄)(η¹-N-^tBu)TiCl₂ (MeTi₁), BPTi₂ exhibits significantly increased molecular weight of polymer (>two-fold), as well as high level of activity and 1-octene incorporations in ethylene and ethylene/1-octene polymerizations. Although the lower activity was observed at high 1-octene feeds, the combined effects of rigidity and electronic conjugation induced by the biphenylene bridge might be responsible for the observed polymerization properties of BPTi₂.     

Enantioselective Synthesis of α-Alkyl-β-ketoesters: Asymmetric Roskamp Reaction Catalyzed by an Oxazaborolidinium Ion

Breaking kamp: A catalytic route toward chiral α-alkyl-β-ketoesters using the title reaction of α-alkyl diazoester with aldehydes has been developed. The reaction proceeds with high to excellent enantioselectivities and this methodology was applied to a concise two-step synthesis of the natural pheromone sitophilate.     

Correlations,hierarchies and networks of the world’s automotive companies

We investigate, within the scope of econophysics, the correlations, hierarchies and networks of the world’s automotive companies over the 2003–2010 period by using the concept of a minimal spanning tree (MST) and hierarchical tree (HT). We derive a hierarchical organization and construct the MSTs and HTs for the 2003–2010 period and illustrate how the MSTs and their associated HTs developed over time. These periods are divided into two subperiods, such as 2003–2006 and 2007–2010, in order to test various time-windows and understand the temporal evolution of the correlation structure over time. We perform the bootstrap techniques to investigate a value of the statistical reliability to the links of the MSTs. We also use average linkage cluster analysis (ALCA) to observe the cluster structure more clearly in HTs. From the structural topologies of these trees, we identify different clusters of companies according to their geographical proximity and economic ties. Our results show that some companies are more important within the network, due to a tighter connection with other companies. We also find that these important companies play a predominant role in the world’s automotive industry.     

Prediction of the 1H NMR spectra of epoxy-fused cyclopentane derivatives by calculations of chemical shifts and spin–spin coupling constants

¹H NMR spectra of epoxy-fused cyclopentane derivatives have been computationally investigated with density functional calculations in order to unravel the shielding effect of the epoxy ring on the ¹H NMR chemical shifts of N-substituted epoxy-fused cyclopentane-3, 5-diol derivatives. Both ¹H NMR chemical shifts and spin–spin coupling constants have been calculated with the WP04/cc-pVTZ level of theory in solution. The WP04/cc-pVTZ// B3LYP/6-31+G(d) methodology has been found to reproduce the best experimental results on epoxy-fused cyclopentane derivatives. This study is expected to lead experimentalists in their endeavour to characterize epoxy-fused cyclic systems with ease.     

Some rationally looking faces of Ω n having irrational minimum permanents

Let Ω _n denote the convex polytope consisting of all n × n doubly stochasiic matrices. We determine the minimum permanents which may or may not be rational and the permanent-minimizing matrices over some rationally looking faces of Ω _n We also discuss the barycentricity of the (0, l)-matrices with which we consider the permanent-minimization problem.     

B cell activation factor (BAFF) is a novel adipokine that links obesity and inflammation

B cell activation factor (BAFF) is a novel member of the TNF ligand superfamily, mainly produced by myeloid cells. BAFF has been shown to participate in B-cell survival and B- and T-cell maturation. BAFF expression in adipocytes has been recently demonstrated. In the current study, we verified that BAFF expression is increased during adipocyte differentiation. BAFF expression was augmented by TNF-α treatment and was decreased by rosiglitazone treatment. BAFF secretion in lean and in ob/ob mice sera were compared and smaller amount of BAFF was secreted in ob/ob mice. mRNA and protein expression were different between epididymal and visceral adipose tissue. BAFF expression was also increased in ob/ob mouse adipose tissue. We sought to identify known BAFF receptors (BAFF-R, BCMA, and TACI) in adipocytes, and determined that all three were present and upregulated during adipocyte differentiation. However, the expression of TACI was distinct from that of BAFF-R and BCMA under TNF-α and BAFF ligand treatment. BAFF-R and BCMA expression levels were upregulated under pro-inflammatory conditions, but TACI was reduced. Conversely, BAFF-R and BCMA expression levels were downregulated by rosiglitazone treatment, but TACI was increased. Taken together, our results suggest that BAFF may be a new adipokine, representing a link between obesity and inflammation.