A modern approach to the solution and analysis of the Simha-Somcynsky model for the description of pressure-volume-temperature properties of polymer fluids

We revisit the Simha-Somcynsky model of polymer fluids with the purpose of developing novel theoretical and computational approaches to simplify and speed up its solution as well as the fitting of experimental data, and decrease its level of mathematical complexity. We report a novel method that allows us to solve one of the two equations of the model exactly, thus putting the level of mathematical difficulty on a par with the one of other models for polymer fluids. Moreover, we describe a computational algorithm capable of fitting all five parameters of the model in an unbiased way. The results obtained reproduce literature results and fit experimental pressure-volume-temperature and solubility parameter data for three polymers very accurately. Moreover, the new techniques allow for the investigation of the model at very low temperatures. Unexpectedly, the model predicts behaviors that could be interpreted as a glass transition, as routinely observed in dilatometry and differential scanning calorimetry, and a glass phase. We compared the predicted and experimental T g’s for cis poly(1,4-butadiene) and found an excellent quantitative agreement.     

Linearized Stability of Charged Thin-Shell Wormholes

The linearized stability of charged thin shell wormholes under spherically symmetric perturbations is analyzed. It is shown that the presence of a large value of charge provides stabilization to the system, in the sense that the constraints onto the equation of state are less severe than for non-charged wormholes.     

Kinetics of the thermal decomposition of bis(trifluoromethyl) peroxydicarbonate,CF3OC(O)OOC(O)OCF3

Thermal decomposition of bis(trifluoromethyl) peroxydicarbonate has been studied. The mechanism of decomposition is a simple bond fission, homogeneous first‐order process when the reaction is carried out in the presence of inert gases such as N₂ or CO. An activation energy of 28.5 kcal mol^?1 was determined for the temperature range of 50–90°C. Decomposition is accelerated by nitric oxide because of a chemical attack on the peroxide forming substances different from those formed with N₂ or CO. An interpretation on the influence of the substituents in different peroxides on the O? O bond is given. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 15–19, 2003     

One‐step synthesis of aminopyrimidines from 5‐Oxo‐4H‐benzopyrans

Novel 4‐amino‐6‐aryl‐2‐phenylpyrimidine‐5‐carbonitriles have been prepared in one step procedure from the readily available 4‐aryl‐2‐amino‐3‐cyano‐5,6,7,8‐tetrahydro‐7,7‐dimethyl‐5‐oxo‐4H‐benzopyrans. The mass spectroscopy study under EI conditions shows molecular peaks with high intensity corresponding to the loss of benzonitrile from the C2 position of the pyrimidine ring. Semiempirical (AMI and PM3) and ab initio HF/6–31G* calculations reveal a favored distorted geometry where the three rings are not in the same plane.     

Effect of nanotube functionalization on the properties of single‐walled carbon nanotube/polyurethane composites

A commercially available aliphatic thermoplastic polyurethane formulated with a methylene bis(cyclohexyl) diisocyanate hard segment and a poly(tetramethylene oxide) soft segment and chain‐extended with 1,4‐butanediol was dissolved in dimethylformamide and mixed with dispersed single‐walled carbon nanotubes. The properties of composites made with unfunctionalized nanotubes were compared with the properties of composites made with nanotubes functionalized to contain hydroxyl groups. Functionalization almost eliminated the conductivity of the tubes according to the conductivity of the composites above the percolation threshold. In most cases, functionalized and unfunctionalized tubes yielded composites with statistically identical mechanical properties. However, composites made with functionalized tubes did have a slightly higher modulus in the rubbery plateau region at higher nanotube fractions. Small‐angle X‐ray scattering patterns indicated that the dispersion reached a plateau in the unfunctionalized composites that was consistent with the plateau in the rubbery plateau region. The room‐temperature modulus and tensile strength increase was proportionally higher than almost all increases seen previously in thermoplastic polyurethanes; however, the increase was still an order of magnitude below what has been reported for the best nanotube–polymer systems. Nanotube addition increased the hard‐segment glass transition temperature slightly, whereas the soft‐segment glass transition was so diffuse that no conclusions could be drawn. Unfunctionalized tubes suppressed the crystallization of the hard segment; whereas functionalized tubes had no effect. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 490–501, 2007     

An unusual syn conformation of 5‐formyluracil stabilized by supramolecular interactions

The asymmetric unit of the amino–oxo tautomer of 5‐formyluracil (systematic name: 2,4‐dioxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carbaldehyde), C₅H₄N₂O₃, comprises one planar amino–oxo tautomer, as every atom in the structure lies on a crystallographic mirror plane. At variance with all the previously reported small‐molecule crystal structures containing the 5‐formyluracil residue, the formyl substituent in the title compound exhibits an unusual syn conformation. The molecules are linked into planar sheets parallel to the bc plane by a combination of six N—H...O and C—H...O hydrogen bonds. Four of the hydrogen bonds are utilized to stabilize the formyl group in the syn conformation.     

Normalization and noise-reduction algorithm for fringe patterns

This paper presents a fringe pattern normalization and noise-reduction algorithm. Locally the background noise is suppressed, the modulation normalized and the noise smoothed. An expression to calculate the cosine-only term is formulated. It is related to the directional derivatives of the intensity fringes. Two-dimensional Fourier series are used to calculate the parameters needed for the algorithm. Experimental work is presented using diffraction and ESPI images. The programming is relatively simple and involves mainly local convolutions. The processing time using a 2 GHz computer to normalize an image of 256 × 256 pixels is approximately one second.     

Synthesis and intramolecular cyclization of bisthiadiazinylmethane derivatives

Bisthiadiazinylmethane derivatives obtained from 1,2,6-thiadiazine 1,1-dioxides and formaldehyde, undergo unusual intramolecular cyclizations to thiadiazino [4,3-g] [2,1,3] benzothiadiazine tetraoxides. The structures of the newly synthesized compounds are discussed on the basis of ¹H and ¹³C-NMR data and X-ray analysis.     

Losartan potassium,a non‐peptide agent for the treatment of arterial hypertension

In the title compound, potassium 2‐butyl‐4‐chloro‐1‐{[2′‐(5‐tetrazolido)­bi­phenyl‐4‐yl]­methyl}‐1H‐imidazol‐5‐yl­methanol, K⁺·C₂₂H₂₂ClN₆O^?, the imidazole and tetrazole rings are at angles of 85.0 (2) and 51.8 (1)°, respectively, to the phenyl rings to which they are attached, while the dihedral angle between the latter two rings is 46.7 (1)°. The coordination sphere of the metal cation consists of six tetrazoyl N atoms, the methanol O atom and the π cloud of one of the phenyl rings. These interactions determine the formation of columns of molecular anions that lie parallel to the b axis, while hydrogen bonding contributes to intercolumnar cohesion. Far from the centre of the columns, the hydro­carbon chain is immersed in a hydro­phobic environment.     

Homogeneous hydrogenation of ketones to alcohols with ruthenium complex catalysts

A number of ruthenium triphenylphosphine complexes catalyse the reduction of ketones to their corresponding alcohols in the presence of water. The most convenient catalyst precursors are carbonyl containing complexes which do not promote decarbonylation of the substrate. The hydrogenation of acetone with hydridochlorocarbonyltris(triphenylphosphine)ruthenium is first order with respect to the substrate concentration, the catalyst concentration, the hydrogen pressure and the water concentration. Turnover numbers up to 15,000 have been achieved with this catalyst. Other ketones are also reduced by RuHCl(CO)(PPh₃)₃ and the rate of the reaction is dependent on the nature of the substrate.