Flow pattern,void fraction and pressure drop of refrigerant two-phase flow in a horizontal pipe—II: Analysis of frictional pressure drop

Two-phase flow in horizontal pipe was analyzed with simplified models for annular and stratified flow. The velocity profiles for the liquid and gas phase were described with the Prandtl mixing length. From this analysis, the frictional pressure drop was calculated with the modified Baker map for flow pattern transition. The intermediate region, i.e. wavy flow, was interpolated between annular and stratified flow. Comparison of this analysis with existing experimental data of refrigerants showed good agreement.     

Structure of protonated thioformaldehyde

It is proposed, from an ab initio (4–31G) SCF calculation, that the most stable forms of protonated thioformaldehyde may be the C-protonated complexes H₃CS⁺. The energy-gradient technique was used for geometry optimization, and an energy decomposition analysis was carried out to elucidate the origin of this abnormal behavior of the C=S group.     

Nachweis der heterogenen Nukleierung von Polypropylen-Sph?roliten mittels Elektronen-Mikroanalyse

Ohne Zusammenfassung     

Electronic structure of C84 and KxC84: Comparison to C60 and graphite

X ray photoemission spectra show ～10 valence band features in C₆₀ and C₈₄ films, although they are less distinct in C₈₄ because of the increased number of valence electrons and the decreased molecular symmetry. The presence of inequivalent carbon atoms in C₈₄ is reflected by the fact that the C 1s main line is ～0.2 eV wider than in C₆₀. The C 1s satellite region of C₈₄ exhibits four features within 15 eV of the main line and shows that the HOMO-LUMO π-π* excitation energy of C₈₄ is ～0.5 eV smaller than in C₆₀. Potassium 2p spectra for K-doped C₈₄ films suggest the formation of a phase with composition K₃C₈₄ with two spectroscopically-distinguishable K sites. A new spectral feature emerges when the K content is increased beyond K₃C₈₄, suggesting a phase transition and a saturated composition of K₆C₈₄, as for K_xC₆₀. These similarities are intriguing since K_xC₈₄ is insulating for all x while K₃C₆₀ is metallic and superconducting.     

Synthesis of a versatile functionalized tetraquinane. Convenient access to 1,3-bishomopentaprismanedione

The tetracyclic diene dione 1 has been synthesized by a short oxidative decarboxylation route starting with the domino Diels-Alder adduct 2. Photocyclization of the bisketal of 1 was used to arrive expediently at 1,3-bishomopentaprismanedione (7).     

Determination of peptide φ angles in solids by relayed anisotropy correlation NMR

A solid state NMR method is presented for determination of a backbone dihedral angle φ in peptides, being based on the previously reported method, relayed anisotropy correlation (RACO) NMR [Y. Ishii et al., Chem. Phys. Lett. 256 (1996) 133]. In the present method, the and the dipolar tensors in the system are two-dimensionally (2D) correlated via polarization transfer from to under magic angle spinning (MAS). This method was applied to N-acetyl , -valine, and the H–C–N–H dihedral angle was determined to be 154.0±1.4° or 206.0±1.4°, the former agreeing with the X-ray value of 154±5°.     

Doppler-free resonant two-photon transition for isotope separation

The Doppler-free two-photon transition by the use of two opposing laser beams makes the highly selective excitation of isotopic molecules possible. Saturation and pressure dependence of Doppler-free two-photon excitation with arbitrary amplitudes of the optical fields have been calculated and compared with those of the two-step transition and the single-photon transition. The result at the Doppler limit for low pressure gas reveals that the probability of the selective two-photon excitation with a moderate laser power can be larger than that of the single-photon excitation as well as that of the two-step excitation.