Chloroform sorption in nanoporous crystalline and amorphous phases of syndiotactic polystyrene

The transport of chloroform in films of atactic polystyrene and of semicrystalline syndiotactic polystyrene in its nanoporous form (δ‐form) has been investigated by gravimetric analysis. Experimental tests have been performed at 35, 49, and 56 °C and at several vapor pressures ranging from 0.5 to 100 Torr. Nonequilibrium lattice fluid prediction of the amorphous sorption behavior was used to enucleate the sorption contribution of the crystalline nanoporous phase from semicrystalline samples. Sorption behavior of the crystalline phase has been interpreted on the basis of Langmuir equation. Moreover, the chloroform sorption at low activities in the crystalline nanoporous phase has been predicted by using Grand Canonical Monte Carlo molecular simulations. Isosteric heats of sorption were also experimentally evaluated for the crystalline phase, and compared with the corresponding prediction of molecular simulation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 8–15, 2008     

A measurement of the azimuthal angle dependence of the process ep → enπ+ near threshold

The azimuthal angle dependence of the process ep → enπ⁺ has been measured by detecting the electron and neutron in coincidence. Data are presented for momentum transfers (?k²) between 0.08 and 0.32 $\text{(}\text{GeV}\text{c}\text{)}{}^2$ and at energies close to threshold. Fixed-t dispersion relation models give predictionsin good qualitative agreement with the data.     

Scalar quantum electrodynamics on lattice correlation inequalities and infinite volume limit

We consider Wilson's lattice approximation to scalar Quantum Electrodynamics. We establish correlation inequalities of Griffiths-Kelly-Sherman type and a rigorous transfer matrix formalism, from which existence and non triviality of the infinite volume limit follow.     

Study of vector mesons in dimuon production in a large kinematic region in p-W and S-W interactions at 200 GeV/c/nucleon

Results are presented on and production in p–W and S–W interactions at 200 GeV/c/nucleon measured via the dimuon decay in a large kinematic region. The data are normalized to the charged particle multiplicity in the same rapidity interval. They have been collected using the HELIOS/3 muon spectrometer at the CERN SPS. The ratio , where is the relevant resonance branching fraction, increases between proton and sulphur projectiles, and is somewhat enhanced going from peripheral to central S–W interactions. This results from an increase in the number of produced 's per charged particle. The ratio is measured in different intervals of p and rapidity. It is not clearly dependent on p, but is larger at higher rapidities. production, likewise normalized to charged multiplicity, is significantly lower in S–W compared to p–W interactions. Received: 27 October 1997 / Revised version: 5 March 1998 / Published online: 13 July 1998     

Intense shake-up satellites in the XPS spectra of planar and sterically hindered N-piperidyl-nitrobenzenes and -nitrothiophens

The shake-up satellites present in the O_1s and N_1s energy regions of the XPS spectra of the planar 4-N-piperidyl-nitrobenzene (1) and 2-N-piperidyl-5-nitrothiophen (3), and of the sterically hindered 2-N-piperidyl-nitrobenzene (2), 2-N-piperidyl-3-nitrothiophen (4) and 3-N-piperidyl-2-nitrothiophen (5) and, for comparison, of 2-bromo-3-nitrothiophen (6) have been analyzed with the help of CNDO/S CI calculations. The spectra of the planar derivatives closely resemble these of the related compounds previously analysed, the main satellites deriving from the transition between the highest occupied molecular orbital (HOMO, localized at the donor-ring moiety) towards the lowest unoccupied one (LUMO, localized at the nitro group). Calculations indicate that in the ortho derivatives new relaxation processes are allowed upon N_1s/NO₂ ionization. In 2, where the angle of rotation θ is closer to 90° than 60°, the NR ₂ lone-pair orbital relaxes through space towards the core-ionized N/NO₂ atom. In 4 and 5, where 45° ? θ ? 60°, both through-ring and through-space relaxations are present. The assignment of the main N_1s/NO₂ line in 1 is discussed.     

Sulphonylium ions in the gas phase

Electron impact mass spectrometry was used to investigate the fragmentation of a series of arenesulphonyl chlorides. Sequential losses of a chlorine atom and sulphur dioxide from the molecular ions occurred and the reverse of these reactions had small critical energies that were generally unaffected by the ring substituent. However, an interesting intramolecular cyclization reaction occurring on the ortho-nitro derivative is discussed with the aid of kinetic energy release measurements on this derivative and on a model compound. Appearance energy measure ments combined with multiple scattering Xα calculations led to an estimate of the sulphur-chlorine bond strength in benzenesulphonyl chloride.     

An mo study of the substituent effect in benzene radical ions

The effect of various types of substituents (X=OH, CH₃, CN, SiH₃) in benzene radical cations and anions have been investigated using INDO-SCF computations with and without π conjugation admitted between the substituent and the adjacent substrate. The inductive effect of the substituent has been found to play a minor role in determining the more stable configuration, the latter being determined in all cases investigated by the π conjugative interactions. A OEMO analysis of such interactions provides a better understanding of the key factors controlling the configuration preferentially stabilized in the various cases.     

Scalar Quantum Electrodynamics on the lattice as classical statistical mechanics

Wilson's lattice approximation allows us to apply classical statistical mechanics ideas to the study of Scalar Quantum Electrodynamics. Our main tools are Griffiths-Kelly-Sherman inequalities, the transfer matrix formalism and exponential bounds. Our main result is the existence of the infinite volume limit for every value of the coupling parameters.     

Conformational studies by dynamic NMR. Part XV. The rotational barrier of N-methyl aniline

Low temperatures C-13 NMR spectra allowed the determination of the rotational barrier of N-methyl aniline in solution. The shifts of the anisochronous ortho and meta carbons were assigned by $\text{ab initio}$ calculations.