Diatomic interactions in momentum space. The 2pπ u and 3dπ g states of H 2 + system

The recently proposed method of momentum electron density for interatomic interactions is applied to the two states of the H ₂ ⁺ system. The processes of the attractive 2P _u and repulsive 3d _g interactions are analysed based on the behaviour of the momentum density and Compton profile. The results are compared with the previous ones for the 1 _{S g} and 2p _u states. The guiding principle of contraction and expansion for the energy-density relation in momentum space is shown to be common to both the and states.     

Weak nucleon currents in beta decay and muon capture

We made extensive investigations on the weak charged nucleon currents and structure of complex nuclei in weak nuclear processes. Using our new formalism, which has almost no approximation as far as the lepton part is concerned, we have studied the beta-ray spectra and beta-ray angular distributions in the¹²B and¹²N beta decays. The weak magnetism predicted by CVC is in excellent agreement with the experimental data on beta-ray spectra given by the Columbia and Heidelberg groups. It is noticed here that the difference _– – ₊ of the coefficients in the beta-ray angular distributions in aligned¹²B and¹²N is free from ambiguity of the nuclear model. We found practically no second-class induced tensor current with the data given by the Osaka, Louvain and Zürich groups. On the other hand, the sum _– + ₊ of the coefficients represents the time component of the main axial vector current, and it is free from weak form factors. With this sum we studied the exchange-current and core-polarization effects. These two effects are large, and they are almost cancelled out by each other in this case. We also found the strength of the induced pseudoscalar form factor which is generally consistent with PCAC, from nuclear polarizations of¹²B in muon capture of¹²C performed by the Zürich and Tokyo groups. These nuclear polarizations are insensitive to the nuclear model, if the exchange-current and corepolarization effects are properly taken into account.This paper was partially delivered at the Annual Meeting of the Korean Physical Society, Seoul, 1983; the Asia Pacific Physics Conference, Singapore, 1983; and the International Symposium on Nuclear Spectroscopy and Nuclear Interactions, Osaka, 1984.The present paper is based on our recent theoretical investigations, which have been performed by the theory group, Department of Physics, Osaka Unicersity. The author would like to express his sincere thanks to Professors H. Ohtsubo, Y. Yokoo, Drs. T. Sato, K. Koshigiri, M. Nishimura, M. Kobayashi, and Mr. M. Fukui for their collaboration, to Professors C.W. Kim, Y.K. Lee and K. Kubodera for their stimulating discussions during his 1983 summer visit to Johns Hopkins University, to Professors K. Sugimoto, T. Minamisono, V.L. Telegdi, L. Grenacs, T. Yamazaki and K. Nagamine for sending him their experimental results before publication. Numerical calculations were performed with the aid of NEAC ACOS 1000, Computor Center, Osaka University. This work is partly supported by Grant-in-Aid for Scientific Research, The Ministry of Education, Science, and Culture.This paper is dedicated to Professor K. Sugimoto in commemoration of his sixtieth birthday.     

Dependence of the molecular aggregation state of octadecylsiloxane monolayers on preparation methods

The molecular aggregation state of octadecylsiloxane monolayers on Si-wafer substrate surfaces prepared from octadecyltrimethoxysilane (OTMS) or octadecyltrichlorosilane (OTS) was investigated on the basis of grazing incidence X-ray diffraction (GIXD), Fourier transform infrared spectroscopy (FT-IR), contact angle measurement, field emission scanning electron microscopy (FE-SEM), and scanning force microscopy (SFM). The OTMS monolayer was prepared by using the chemical vapor adsorption (CVA) method, and the OTS monolayers, which were used as reference samples, were prepared either by chemisorption (OTS-S) or by the water-cast method (OTS-W). The GIXD, FT-IR, lateral force microscopic (LFM) measurements, and FE-SEM observation revealed that the alkyl chains in the OTMS monolayers prepared using the CVA method are in an amorphous state at room temperature. According to the LFM measurement, the transition temperature from the hexagonal crystalline phase to the amorphous phase was found to be ca. 333 K for the OTS-S monolayer prepared by the chemisorption method. However, the phase transition was not observed in the OTMS monolayer prepared by the CVA method. Also, the atomic force microscopic (AFM) observation and the contact angle measurement showed that the OTMS monolayer prepared by the CVA method has a uniform surface when compared to the OTS monolayers. These results indicated that organosilane compounds in the monolayer prepared by the CVA method were immobilized on the Si-wafer substrate surface in an amorphous state, which was quite different from the hexagonal crystalline state obtained by the chemisorption and water-cast methods.     

Conformational and neighboring effects in graft polymerization of acrolein on 4(5)-vinylimidazole-acrylamide copolymer

The graft polymerization of acrolein (AL) on poly-4(5)-vinylimidazole or the copolymers of 4(5)-vinylimidazole(VIm) and acrylamide of varying composition were carried out kinetically in an ethanol–water mixture at 0°C. The graft polymerization rate R_p increased with an increasing concentration of water in the solvent. On the other hand, the R_p of the copolymer which incorporated 50 mol % VIm showed the highest value. These results were discussed by assuming interaction between amide and imidazole groups in copolymer.     

Control in spin-delocalization into the 2-substituted π-systems in 3-oxophenalenoxyl neutral radicals: evaluation by their dimeric structures and DFT calculations

3-Oxophenalenoxyl derivatives, neutral π-radicals having two oxygen atoms at 1,3-position on a phenalenyl skeleton, possess most of their spin densities at the two oxygen atoms and the 2-position, featuring in easy dimerization at the 2-position. For the decrease in spin density at the 2-position by invoking spin-delocalization into the 2-substituted π-systems, we have designed 2-thienyl-3-hydroxyphenalenone derivatives as synthetic precursors of neutral π-radicals, and conducted their oxidation reactions by using a variety of oxidants. The chemical structures of the dimer obtained were unambiguously determined by FABMS, IR, and NMR spectra with help of density functional theory calculations, showing the formation of the bonds on the thienyl moieties. These observations and DFT calculations illustrate the occurrence of a considerable amount of spin-delocalization into the 2-substituted-thienyl moieties from the 3-oxophenalenoxyl skeletons.     

CNDO/2 calculations and configuration analyses for some hydrogen-bonded systems

The potential energy curves of hydrogen-bonded systems were calculated for the water, methanol, and formic acid dimers and for the hydrogen maleate ion by a modified CNDO/2 method, the core resonance integrals between-electrons being distinguished from those between-electrons, the different bonding parameters being used for -O- and =O, and the core potential integralsV _AB ^c for O-H, C=O, and O...O being determined semi-empirically. Consequently, the following results were obtained: 1) a potential energy curve with a single minimum atr(O-H)=0.95 Å and with a concavity near 1.70 Å for the linear chain dimers of water and methanol; 2) a symmetrical potential energy curve with two minima atr(O-H)=0.95 and 1.78 Å for the cyclic dimer of formic acid; 3) a flat-bottomed symmetrical potential energy curve for the hydrogen maleate ion. The configuration analysis method was applied to the hydrogen-bonded systems; the contributions of the covalent ((O-H-O)^–1) and ionic (O^–H⁺O^–) structures being 54% and 39%, respectively, for the symmetrical hydrogen bonding of the hydrogen maleate ion.

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Zusammenfassung Die Kurven potentieller Energie von Systemen mit H-Brücken wurden im Fall von H₂O-, CH₃OH- und HCOOH-Dimeren und für das Hydrogen-Maleatanion mittels eines modifizierten CNDO-Verfahrens berechnet, wo für Rumpf-- und --Elektronen jeweils verschiedene Resonanzintegrale und verschiedene Bindungsparameter für =O und -O- verwendet und wo die Rumpfpotential-Integrale für O-H, C=O und O...O semiempirisch bestimmt werden.Die Resultate sind 1) eine Potentialkurve mit einem einfachen Minimum für lineare Ketten von H₂O und CH₃OH, 2) eine symmetrische Potentialkurve mit zwei Minima für das cyclische Diniere von HCOOH und 3) eine Potentialkurve mit einem flachen Minimum für das Maleatanion. Konfigurationsanalyse ergab einen Beitrag von 39% für die ionischen Strukturen.

     

New antimitotic bicyclic peptides, celogentins D-H, and J, from the seeds of Celosia argentea

Six new bicyclic peptides, celogentins D-H (1-5) and J (6) have been isolated from the seeds of Celosia argentea, and the structures including its absolute stereochemistry were determined by using extensive NMR methods and chemical means. Celogentins E-H (2-5) and J (6) showed potent inhibition of tubulin polymerization, while the inhibitory activity of celogentin D (1) was modest. Structure-activity relationship study indicates that ring size of the bicyclic ring system including unusual β^s-Leu, Trp, and His residues would be important for their biological activity.     

Electrochemical quartz crystal microbalance analysis of the cathodic process in a lithium-ion battery

The surface processes at carbon and platinum electrodes have been studied using the electrochemical quartz crystal microbalance technique in organic electrolyte solutions for lithium ion batteries. The changes in resonance frequency were analyzed as a function of the electrode potential, indicating that the process depended not only on the electrode material but also on the cathode potential. In the solution containing LiBF₄ as the electrolyte, the main product at the platinum surface was Li₂CO₃ and LiF, whereas formation of lithium alkylcarbonates was the primary process at the platinum and carbon electrodes in LiPF₆ solution.     

Antiviral agents of plant origin. II. Antiviral activity of scopadulcic acid B derivatives

Scopadulcic acid B derivatives were synthesized and their antiviral activities against herpes simplex virus type 1 (HSV-1) were examined. All the derivatives synthesized showed lower inhibitory activities against HSV-1 than scopadulcic acid B (2). Five compounds, 7, 8, 15, 16, and 18, however, had in vitro therapeutic indexes larger than 7 and were considered to merit further investigation.