Showing papers by "Korea University published in 1984"

Liquid crystal polymers with flexible spacers in the main chain

Abstract: This review is be concerned primarily with the synthesis and properties of such polymers which show thermotropic behaviour.

Thermotropic Compounds with Two Terminal Mesogenic Units and a Central Spacer. 51. Homologous Series of Polymethylene-α, ω-Bis (p-Oxybenzylidene Aniline)

Abstract: Two series of new thermotropic compounds with two terminal mesogenic units, p-oxybenzylidene-p-substituted anilines, attached to both ends of a central polymethylene spacer were prepared. The first series of compounds has central polymethylene spacers of varying length, while the second has different substituents on the aniline moiety of the mesogenic groups which are bracketing the central decamethylene spacer. The mesomorphic properties of the compounds were investigated by differential scanning calorimetry and on the hot-stage of a polarizing microscope. A thermodynamic analysis of the phase transitions of the compounds was made and the results are explained in relation to their structure.

A Study On The Parasitic Helminths Of Domestic Duck(Anas Platyrhynchos Var. Domestica Linnaeus) In Korea.

Abstract: During February 1982 to Septemner 1983, a total of 105 domestic ducks (Anas platyrhynchos var. domestica Linnaeus) were collected from Ichon Gun, Puasn City, Chunchon City, Yanggu Gun, Taejeon City and unknown areas in Korea. In the results, six trematode and one nematode species of helminth parasites were obtained and described as follows: Amphimerus anatis Yamaguti, 1933, Echinostoma miyagawai Ishii, 1932, Echinochasmus japonicus Tanabe, 1926, Cryptocotyle sp., Notocotylus attenuatus (Rudolphi, 1809) Kossack, 1911, Apatemon sp, and nematode species, Heterakis gallinarum Schrank, 1788. From this collection, Amphimerus anatis Yamaguti, 1933, Echinochasmus japonicus Tanabe, 1926, Genus Cryptocotyle Luhe, 1899 and genus Apatemon Szidat, 1928 were firtstly recorded in Korea.

Geology and geochemistry of the Sambo Pb-Zn deposit, Republic of Korea

Abstract: The Sambo lead-zinc deposits are composed of fissure-filling quartz-barite veins within Proterozoic biotite schist which has been intruded by granite and granodiorite stocks. K-Ar dates of biotite and muscovite from the intrusions are 177 + or - 4 and 164 + or - 3 m.y., suggesting a Jurassic age for Pb-Zn-Ba mineralization. This age is in agreement with data for metallogenic epochs in Korea. Ba-rich Pb-Zn deposits are related to a Jurassic-Early Cretaceous epoch, whereas Ba-poor Pb-Zn deposits are generally related to Late Cretaceous-Tertiary igneous activity. Mineralization at Sambo consists of three distinct stages of quartz-barite veins (I, II, and III) which were separated in time by tectonic fracturing and brecciation events. Ore textures of Stage II suggest rhythmic deposition. Five successive mineralization cycles of Stage II, each with up to seven nearly monomineralic bands, are recognized. Fluid inclusion data suggest that each stage evolved from early high temperatures (near 300 degrees C) to later lower temperatures (less than 200 degrees C). Sulfur isotope and fluid inclusion evidence indicates that galena, sphalerite, and barite were deposited at temperatures near 160 degrees to 265 degrees C from solutions with salinities ranging from 2 to 17 equivalent weight percent NaCl. Fluid inclusion evidence of boiling suggests pressures of less than 100 bars during portions of stage II mineralization. This pressure corresponds to depths at the time of mineralization of between 500 and 1,250 m.--Modified journal abstract.

The Production of L-serine with a methylotrophic microorganism using the L-serine pathway and coupling with an L-tryptophan-producing process

Abstract: The cultural conditions for the production of enhanced formation of L-serine (up to 7 g/L) are described with the methylotrophic bacterium Pseudomonas 3 ab (DSM 672) The batch process is divided into three parts: (1) the biomass production phase, (2) substrate limitation period, and (3) L-serine accumulation phase The initial specific production rate of qp = 01 g L-serine/g dry wt/h is based on the inhibition of the L-serine pathway This is accomplished by high precursor concentrations (glycine) and a pH shift to pH 85 The enzymatic background is discussed Furthermore, a coupling of the L-serine process with a L-tryptophan-producing process is demonstrated

Epitaxial integrated dE1 − dE2 silicon detectors

Abstract: Epitaxial integrated dE1 − dE2 silicon detectors have been developed by using the multilayer epitaxial crystal growth technique combined with the chemical preferential etching technique. These detectors are useful for eliminating events affected by channeling and blocking effects in the identification of heavy ions using multiple detector telescope systems. Characteristics of dE detectors of the integrated dE1 − dE2 type are confirmed to as good as those of integrated E − dE detectors.

Effect of spices on hepatic microsomal enzyme function in mice

Abstract: The effect of twenty two spices on liver microsomal monooxygense activity was tested as measured by alteration of hexobarbital (HB) narcosis and strychnine mortality in mice. Oral administration of seven spices for 7 consecutive days caused a significant shortening of the duration of HB-induced sleeping time. The treatment of mice with a singlei.p. injection of 9 spices resulted in a significant prolongation of the sleeping time. White pepper, dill and fennel reduced the toxicity of strychine. These results strongly indicated that some spices might affect the activity of liver microsomal drug metabolizing enzyme (DME) function.

Nuclear interaction of 300 GeV negative poins in emulsion

Abstract: Experimental data are presented on charged particle multiplicities production in interactions of 300 GeV/c negative poins with emulsion nuclei. Correlations were established and the obtained parameters of multiplicity distributions compared with those obtained from proton-nucleus interaction data at 300 GeV/c.

Complex Formation of Polyamides Containing Dibenzo-18-Crown-6 Moieties with Alkali Metal Ions

Abstract: New polyamides containing dibenzo-18-crown-6 structural units along the main chain were synthesized from cis- or trans-4,4′-diaminodibenzo-18-crown-6 and a 4,4′-dicarboxy-α, ω-diphenoxyalkane. In addition to their general properties, the complexing capabilities of polymers with alkali metal ions were studied by examining their solution viscosities in the presence of the P-toluenesulfonates of Rb+, K+, Na+, and Li+ and potassium salts of CH3C6H4SO3−, SCN−, I−, and Br−. The viscosity of the polymer solutions in the presence of K+ or Rb+ salts resembled that of typical polyelectrolytes, with reduced viscosities strongly enhanced at low concentrations. This was explained in terms of complexation between the metal ions and the crown ether moieties in the polymer chain.

Phase-Transfer Polycondensation of Bisphenolate Anions and 1,6-Dibromohexane

Abstract: Phase-transfer catalysis, also often referred to as “ion pair partition” is a novel synthetic technique which has been the subject of much interest in recent years not only in the field of organic synthesis but also in polymer chemistry. The term “phase-transfer catalysis” was first introduced in 1971 by Stark1,2 who studied kinetics in detail and the mechanism of reactions which are catalyzed by small amounts of onium salts such as quaternary ammonium or phosphonium compounds. Brandstrom3–5 and Makosza6–8 also made major initial contributions in the understanding of such reactions and the application thereof in various synthetic reactions. A generally accepted phase-transfer reaction scheme is shown in Fig. 1 for the reaction of RX + Y-→ RY + X-. Catalytic onium ion (Q+) transfers the nucleophile Y- into the organic phase in the form of ion pair Q+Y-, which then reacts with RX in organic phase producing the products RY and X-. X-’s are removed by Q+ from organic phase into aqueous phase as they are formed.

Effects of the side groove on the characteristics of high purity silicon detectors

Abstract: A remarkable characteristic of the surface barrier detector with a side groove cooled down to liquid nitrogen temperature has been observed. That is, an abrupt increase of the output noise at a definite voltage when increasing the bias voltage slowly. This is caused by a carrier injection from the side surface of the groove near the neck narrowed by the side groove. This excess noise disappears after the depletion layer extends into the neck of the side groove. This is confirmed by the fact that the capacitance of the detector decreases abruptly at the bias voltage corresponding to decrease of the excess noise. This detector is capable of operation at a voltage higher than this bias voltage with low noise.

Effect of mesogenic unit and spacer structures on the thermotropic properties of main chain liquid crystal polyesters

Abstract: The thermotropic liquid crystal behavior of polymers is of strong current interest among polymer scientists both because of their possible development into new materials with unique properties and to expand our knowledge on structured fluid phases of 1—6 polymers. The structures of polymers which are capable of forming thermotropic liquid crystal phases are of great variety. However, essentially all of them can be assigned to one of two categories: either to those which have mesogenic units attached, directly or through spacers, to a polymer backbone (“side chain liquid crystal polymers”) or those having mesogenic units and rigid or flexible spacers in the polymer backbone (“main chain liquid crystal polymers”).

One- and two-particle inclusive distributions in pion- and proton-nucleus interactions at 300 GeV

Abstract: We report the data on 300 GeV pion-emulsion-nucleus reactions and compare the results to proton-emulsion-nucleus reactions at the same energy. In particular we present results on the one- and two-particle inclusive pseudorapidity distributions. Two-particle distributions are investigated by using the correlation function formalism. The dependence of one-particle inclusive spectra on the projectile and nuclear excitation obeys scaling. Short-range correlations are observed for pairs of charged particles. No differences are observed between the analogous correlations in pion- and proton-nucleus interactions.

Many-Body Properties of a One-Dimensional Bose Liquid,

Abstract: The elementary excitations of one-dimensional Bose liquids interacting via a soft potential with a Lennard-Jones-type attractive tail are evaluated in the ring-diagram approximation. Starting with this potential, we have evaluated the structure factor, thermodynamic functions, pair-distribution function, ground-state energy, and sound velocity explicitly. The energy spectrum and structure factor resemble the bulk cases, but the minimum energy is much lower and the first peak of the structure factor is higher. The pair-distribution function decreases as ${r}^{\ensuremath{-}2}$ at large distances, which is characteristic of phonons in one dimension. The ground-state energy is expressed analytically in powers of a dimensionless parameter. The expression agrees with the one obtained from a $\ensuremath{\delta}$- function-type potential.

Magnetic properties of amorphous metal-metalloid alloys

Abstract: The dependence of the magnetic moment on the alloying elements in amorphous Fe-Si-B, Fe-Co-B and Fe-Ni-B alloys has been investigated systematically. The average magnetic moment per atom changes linearly with composition in these amorphous systems. The magnetization mechanism in these amorphous systems is considered with Donor model and the magnetic moment of each element of Fe, Co, Ni, Si and B in Bohr magneton is determined as 2.20, 1.34, 0.24, -5.00 and -0.50, respectively.