The excess enthalpy for a mixture of krypton and xenon: experiment and theory

Measurements of the excess enthalpy of krypton and xenon mixtures at 163 K are reported. These results are found to disagree with the only other published result. This discrepancy is discussed. Conformal solution theory is used to provide an unbiased prediction of the excess enthalpy. We review published experimental and calculated excess thermodynamic properties of the K_r/Xe system at zero pressure and 161.38 K and 165 K.     

Structure–activity relationships of cannabinoids: A joint CoMFA and pseudoreceptor modelling study

A cannabinoid pseudoreceptor model for the CB1-receptor has been constructed for 31 cannabinoids using the molecular modelling software YAK. Additionally, two CoMFA studies were performed on these ligands, the first of which was conducted prior to the building of the pseudoreceptor. Its pharmacophore is identical with the initial superposition of ligands used for pseudoreceptor construction. In contrast, the ligand alignment for the second CoMFA study was taken directly from the final cannabinoid pseudoreceptor model. This altered alignment gives markedly improved cross-validated r² values as compared to those obtained from the original alignment with values of 0.79 and 0.63, respectively, for five components. However, the pharmacophore alignment has the better predictive ability. Both the CoMFA and pseudoreceptor methods predict the free energy of binding of test ligands well.     

Design, synthesis and evaluation of graftable thrombin inhibitors for the preparation of blood-compatible polymer materials

Piperazinyl-amide derivatives of N-alpha-(3-trifluoromethyl-benzenesulfonyl)-L-arginine (1) were synthesized as graftable thrombin inhibitors. The possible disturbance of biological activity due to a variable spacer-arm fixed on the N-4 piperazinyl position was evaluated in vitro, against human alpha-thrombin, and in blood coagulation assay. Molecular modelling (in silico analysis) and X-ray diffraction studies of thrombin-inhibitor complexes were also performed. The fixation of bioactive molecules on poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) membranes was performed by wet chemistry treatment and evaluated by XPS analysis. Surface grafting of inhibitor 1d improved the membrane hemocompatibility by reducing blood clot formation on the modified surface.     

The liquid structure of the solvents dimethylformamide (DMF) and dimethylacetamide (DMA)

The liquid structure of the commonly used solvents dimethylformamide (DMF) and dimethylacetamide (DMA)were measured using state-of-the-art state neutron diffraction augmented with isotopic substitution (NDIS) and interpreted with empirical potential structure refinement (EPSR). Both solvents are found to develop rich local ordering with similar local packing densities, though with differences related to their three-dimensional molecular structure. While DMF’s dipole preferentially orientates anti-parallel to maximise hydrogen bonding, DMA favours parallel arrangement maximising non-directional dispersive forces. The highly-developed local orientational structure found in these solvents rationalises their ability to solvate a range of charged and neutral nanomaterials and highlights that the understanding of nanomaterial dispersions is a multi-body problem in which the geometry of the molecule, as well its dipole moment, must be incorporated.     

Properties of Bromine Fused Salts Based on Quaternary Ammonium Molecules and Their Relevance for Use in a Hydrogen Bromine Redox Flow Battery

Bromine complexing agents (BCA) in aqueous electrolytes for hydrogen bromine flow batteries are used to reduce bromine‘s vapour pressure, while an insoluble and liquid fused salt is formed. The properties (concentrations, composition, conductivity and viscosity) of this fused salt are investigated in this study systematically ex situ by using 7 BCAs at different state of charge in HBr/Br₂/H₂O electrolytes with a theoretical capacity of 179.6 Ah L⁻¹. Bromine is stored in the fused salt at concentrations up to 13.6 M, reaching theoretical volumetrical capacities up to 730 Ah L⁻¹ in fused salts. The fused salt consists of a pure, bromine- and water-free ionic liquid of organic [BCA]⁺ cations and polybromides, and its conductivity bases on a hopping mechanism among the polybromides. Alkyl side chain length of the BCAs and distribution of polybromides influence strongly the conductivity and viscosity of the fused salts. 1-ethylpyridin-1-iumbromide results to be favoured BCA for application.     

[1]Benzothienopyrimidines. I. Etude de la 3H-benzothieno[3,2-d]pyrimidone-4

3H-benzothieno[3,2-d]pyrimidin-4-one (3) was synthesized by bimolecular cyclising the 3-amino-2-carbethoxybenzothiophene (1) with formamide. The electrophilic substituion of 3 afforded N-methylated lactam derivavtives, the structure of which was assigned by 'H nmr and unequivocal synthesis. The sysnthesis of benzothieno[3,2-d]pyrimidine (7) was achieved by desulphurization of the 3H-benzothieno[3,2-d]-[3,2-d]pyrimisine-4-thione (6) or by oxydation of the 4-hydrazinobenzothieno[3,2-d]primidine (5).     

Characterizing the nature of virtual amorphous silicon

Virtual samples of approximations to real amorphous silicon, a-Si, have been prepared using several different processing routes. These include a fast quench from the melt followed by a long slow annealing period using molecular dynamics, a Reverse Monte Carlo approach, and an ab initio minimization. The characterization of these virtual a-Si samples includes a consideration of structural data (the radial distribution function, angular order, etc.), electronic properties (through the density of states), and thermodynamic information (chiefly the nature of the phase transformation from a-Si to liquid). The properties of a-Si are compared to network models, via the continuous random network model, and to experiment. We investigated the stability of virtual a-Si and consider its implications for use in future simulation studies. We have demonstrated the necessity for the accuracy provided by ab initio-based models to describe the interatomic potentials. Throughout this study, we have monitored the role of order in determining physical properties, as characterized by traditional routes (such as angular correlations) and more novel ones (the signature cell method).     

Some small ramsey numbers

In previous work, the Ramsey numbers have been evaluated for all pairs of graphs with at most four points. In the present note, Ramsey numbers are tabulated for pairs F₁, F₂ of graphs where F₁ has at most four points and F₂ has exactly five points. Exact results are listed for almost all of these pairs.