Surface electronic structure of zinc-blende-type GaN(111)

The electronic structure (layer resolved density of states) has been calculated for the gallium nitride (111) oriented slab, using the linear combination of atomic orbitals procedure. The existence of surface states on both Ga- and N-terminated surfaces has been shown. The origin and localization properties of these states have also been analysed.     

Hydrophilic-lipophilic balance and surface film state of nonionic surfactants

Summary The polarographic study on the effect of nonionic surfactants on the damping of oxygen maximum confirms the validity ofVan Voorst Vader's rule and a major part which play the hydrophilic-lipophilic balance of surfactant molecules in surface phenomena. On this basis the simple relationships are presented between the molecular area in surface film (A) andGriffin's andDavies' HLB. It is shown that at a specific pressure theA increases with increasing HLB values for homologous series of nonionic surfactants. The limitations of the validity of the relations derived with respect to the specific surface pressure chosen are also considered.

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Zusammenfassung Polarographische Studien über die Wirkung nichtionogener Tenside auf die Dämpfung des Sauerstoff maximums bestätigen die Gültigkeit der Regel vonVan Voorst Vader und den überwiegenden Einfluß, welchen der Anteil hydrophil-lipophil in den Tensidmolekülen für Grenzflächenphänomene spielt. Auf dieser Basis wird eine einfache Beziehung erhalten zwischen dem Flächenbedarf eines Moleküls im Grenzflächenfilm (A) undGriffin's undDavies HLB-Werten. Es wird gezeigt, daß bei einem spezifischen Oberflächendruck dieA-Werte mit steigenden HLB-Werten in homologen Reihen nichtionogener Tenside ansteigen. Die Grenzen der Gültigkeit dieser Regel werden diskutiert.

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With 2 tables     

The decay of theT=1 isospin triplet inA=12 systems: II. The induced interactions in the anisotropy of beta-rays

Nuclear Structure: calculation of the asymmetryα _? ofβ rays emitted from polarized¹²B and¹²N nuclei. Comparison with experimental values. Formulae for the asymmetry parametersα _? ofβ rays emitted from polarized nuclei is derived using the formalism developed by Behrens-Bühring. The induced interactions are studied in detail. It is demonstrated that the expressions forα _? are independent of the induced pseudoscalar interaction. It was found that the corrections to the lowest order approximation are small. Experimental data of the Louvain and Osaka laboratories are analyzed. We should point out that the data of the asymmetry of theβ ^? decay of¹²B obtained in these two laboratories are quite different. Although the data reported by the Osaka Group require the existence of the induced pseudotensor (IPT) interaction as it has also been stated by other authors, if we combine data of¹²N from Osaka and of¹²B from Lauvain such experimental results can be understood without including the IPT interaction. Thus, we found some evidence that the IPT interaction could be not necessary to explain the asymmetries in the decay of members of theA=12 system.     

Induced scalar interaction in the analysis of superallowed fermi β transitions

Nuclear Structure superallowed Fermiβ transitions; derivation of the coupling constant for the induced scalar interactionf _s from experimental data. Very recent works reported a significant improvement in the consistency of ?t values for superallowed Fermiβ-decays. This fact led us to investigate some aspects which are not usually tackled in a study of this kind of transition. In a recent paper we suggested that an upper limit for the coupling constantf _s for the induced scalar interaction can be derived analyzing superallowed Fermiβ-transitions. In the present work we revise and improve the method for the determination off _s . The result obtained,f _s /f _v =(? 0.4±1.4) × 10^?3, agrees with the prediction of the CVC theory.     

Ultrahigh modulus polyethylene. II. Effect of drawing temperature on void formation and modulus

The maximum degree of molecular orientation and deformation obtained by ultradrawing of high-density polyethylene in air is limited by formation of internal voids (both longitudinal separation of fibrils and perpendicular cracking), and thus values of Young's moduli which are achievable by ultradrawing techniques are also limited to values much below the theoretical limit for fully extended chains. Temperature has a significant effect on the critical draw ratios at which intensive void formation begins, and also on the draw ratio at which failure occurs during the ultradrawing. The temperature effect is observed only for high-density polyethylene having a wide molecular-weight distribution, and which can be drawn at higher temperatures (30–40°C below its melting point), e.g., Dow Chemical polyethylene LP51.1. As a result of ultradrawing at higher temperatures, transparent, ultrahigh modulus samples having draw ratios of order of 40 have been obtained. The higher drawing temperatures significantly reduce fibril separation, and perpendicular cracking is shifted toward higher draw ratios. Hence, with LP51.1 the highest Young's moduli (65–70 GPa) have been exhibited by the samples which were ultradrawn at 100–105°C.     

Extended convergence to continuous in probability processes with independent increments

Summary A special (extended) kind of convergence in distribution of processes with filtration is considered. Recent theorems on the functional convergence of semimartingales are improved by showing that their assumptions imply the extended convergence of semimartingales to continuous in probability processes with independent increments.     

Molecular tight-binding method. II. One- and many-electron method for excess electron bands of molecular crystals

An ab initio method for calculating the energies of excess-electron bands in a molecular crystal is developed. These energies represent the electron affinities of a crystal. The present method employs a tight-binding approximation to describe the molecules in a crystal and a set of local functions to describe the excess electron. One- and many-electron formulations of the method are given, the latter takes into account the effect of polarization of all the molecules in the crystal by the excess electron. A scheme for approximate determination of the electronic-correlation corrections to the one-electron bands is developed and applied to calculation of the excess-electron bands in the HCP helium crystal.     

The Photophysics of β-Tyrosine and Its Simple Derivatives

Synthesis and photophysical studies of (O-methyl)--tyrosine (-tyrosine; an analogue of tyrosine, in which the amino group is moved from the - to the -carbon, closer to the phenol ring) and its derivatives with a blocked amino and/or carboxyl group were performed to explain the nature of the fluorescence of tyrosine derived analogues. All -tyrosine derivatives, except Ac-Tyr(Me), displayed the monoexponential fluorescence decay. The biexponential fluorescence decay observed for Ac-Tyr(Me) is assumed to be the result of the presence of two low-energy conformations (extended and with an intramolecular hydrogen bond). Higher quenching of the fluorescence of -tyrosine derivatives by the N-acetyl group than by the N-methylamide group moved farther was found, contrary to the data found for the respective derivatives of natural tyrosine. The obtained photophysical data are discussed with theoretical calculations (AMBER, AM1) on the basis of the rotamer model.     

Molecular applications of the intermediate Hamiltonian Fock-space coupled-cluster method for calculation of excitation energies

The intermediate Hamiltonian Fock-space coupled-cluster (FS-CC) method with singles and doubles is applied to calculate vertical excitation energies (EEs) for some molecular systems. The calculations are performed for several small molecules, such as H2O, N2, and CO, and for larger systems, such as C2H4, C4H6, and C6H6. Due to the intermediate Hamiltonian formulation, which provides a robust computational scheme for solving the FS-CC equations, and the efficient factorization strategy, relatively large basis sets and model spaces are employed permitting a comparison of the calculated vertical EEs with the experimental data.