Faddeev-Noble Versus Sasakawa-Sawada Equations for the Nuclear Three-Body Coulomb Problem

We compare the efficiency of two Faddeev-type approaches for the nuclear three-body Coulomb problem. The first one is a modification of Noble’s approach, the second one is due to Sasakawa and Sawada. In an integral-equation formulation both of these methods rely on the same Green’s operators and driving terms. The differences lie in the treatment of the long-range Coulomb potentials. Numerical examples show that the modified Faddeev-Noble approach provides for faster convergence.     

Monte Carlo study of the aqueous hydration of dimethylphosphate conformations

Monte Carlo computer simulations were performed on dilute aqueous solutions of the dimethylphosphate anion and the sodium dimethylphosphate ion pair, with the two phosphodiester torsional angles in the gauche–gauche, gauche–trans, and trans–trans conformations. The structural and energetic aspects of the aqueous hydration of each molecule were analyzed in terms of quasi component distribution functions based on the proximity criterion and partitioned into ionic, hydrophilic, and hydrophobic contributions to facilitate an understanding of the hydration pattern and conformational trends in these multifunctional solutes. Special attention was also paid to methodological issues affecting hydration, such as statistical uncertainty in the determined hydration indices, choice of partial atomic charges for the solute atoms, and solute–water interaction potentials adopted in the simulations. The results showed that gauche–trans and gauche–gauche forms are equally favorable for the dimethylphosphate anion with the trans extended form destabilized by hydration. The sodium dimethylphosphate ion pair hydration energetically favors the trans–trans conformation.     

Operating mechanism of the electrolyte cathode atmospheric glow discharge

Cathode fall ( U(cf)), cathodic current density and atomic emission intensities originating from metal salts in the electrolyte cathode were measured as a function of different discharge parameters. Emission intensities in function of cathode fall indicate a potential barrier in the sputtered mass flux. This means that the primary particles of the cathode sputtering are of positive charge and the cathode fall including its internal variables is the most important factor. The measured current density and the U(cf) as a function of pressure are in accordance with the low pressure data in the literature. The observed decrease of the U(cf) with decreasing pH was explained by a model in that the secondary electron emission coefficient of the cathode (gamma) is controlled through a reaction net of competing reactions of different electron scavengers involving the hydroxonium ions of the cathode solution. The model revealed two different electron emission processes of the electrolyte cathode, an emission coupled with hydrated electrons is dominating below pH 2.5 while a proton-independent emission of poor efficiency is working above pH 3. Our model fits to the reported yields of the ultimate products both in the solution and in the gas phase and offers a calculation of gamma and U(cf) in the function of the cathode acidity. The model provides two other independent gamma calculation methods based on product analysis data.     

Effect of cholesterol on the properties of phospholipid membranes. 4. Interatomic voids

The properties of the interatomic voids present in fully hydrated dimyristoylphosphatidylcholine (DMPC)-cholesterol mixed membranes of different compositions are analyzed in detail using a generalized variant of the Voronoi-Delaunay method on the basis of computer simulation results. The systems investigated are chosen from both sides of the DMPC-cholesterol miscibility gap; the pure DMPC bilayer has also been included in the analysis as a reference system. The results obtained show that the empty space is organized in a more compact way, forming larger voids in the presence than in the absence of cholesterol. The voids located in the region of the rigid cholesterol rings become, on average, less spherical, oriented more parallel with the membrane normal axis with increasing cholesterol concentration, whereas an opposite effect of cholesterol is observed in the middle of the membrane among the chain terminal methyl groups. In general, the preferential orientation of the voids is found to strongly correlate with that of the molecules in the hydrocarbon phase of the membranes. The membranes are found to contain rather large voids, the volume of which can be an order of magnitude larger than the largest spherical cavities present in the systems. These voids are elongated or branching channels rather than big empty holes. The voids located among the DMPC and cholesterol molecules are lying preferably parallel with the membrane normal axis. The existence of such empty channels can be of great importance in the cross-membrane permeation of small, uncharged penetrants, in particular, of polar molecules.     

Differing Coordination Modes of (O‐Alkyl)‐p‐Ethoxyphenyldithiophosphonato Ligands in Copper(I), Silver(I) and Gold(I) Triphenylphosphine Complexes

The three (O‐methyl)‐p‐ethoxyphenyldithiophosphonato triphenylphosphine complexes of copper, silver and gold, [(Ph₃P)_nM{S₂P(OMe)C₆H₄OEt‐p}] (M = Cu, n = 2; M = Ag, Au, n = 1) investigated structurally by X‐ray diffraction exhibit remarkable structural differences. The copper compound is a four‐coordinate chelate monomer with Cu–S 2.4417(6) and 2.5048(6) Å; P–Cu–S 104.24(2)–114.01(2)°; Cu–S–P 82.49(3)° and 80.85(2)°. The silver compound is a cyclic dimer with bridging dithiophosphonato ligands and three‐coordinate silver atoms [Ag–S 2.5371(5) and 2.6867(5) Å; P–Ag–S 122.88(2)° and 122.17(2)°; Ag–S–P 89.32(2)° and 103.56(2)°]. The gold compound is monomeric with linear dicoordinate gold [Au–S 2.3218(6) Å; P–Au–S 177.72(2)°, Au–S–P 100.97(3)°].     

How different are ranking methods for fuzzy numbers? A numerical study

Ranking fuzzy numbers is often a necessary step in many mathematical models, and a large number of ranking methods have been proposed to perform this task. However, few comparative studies exist and nowadays it is still unknown how similar ranking methods are in practice, i.e., how likely they are to induce the same ranking. In this study, by means of numerical simulations, we try to answer this question. We shall discover that there are some very similar methods as well as some outliers. We end the paper interpreting the results and giving some recommendations on the use of ranking methods.     

Conformational properties of propargyloxy-calix[4]arene tricarboxamides: NMR and DFT studies on the O-through-the-annulus rotation

The size limit of substituents allowing O-through-the-annulus rotation of substituted calix[4]arenes was further extended to the propargyloxy group in 24-propargyloxy-25,26,27-tris(N,N-dimethylcarbamoylmethoxy)-p-tert-butylcalix[4]arene by demonstrating its free but slow motion affording equilibrium between the partial cone and 1,2-alternate conformers. The effect of solvent and upper rim substituents R¹ on the conformational inversion was investigated by means of ¹H NMR. The rotational isomerisation of the parent (R¹ = H) analogue could not unambiguously be detected. The experimental results were supported by comprehensive density functional theory studies.