Showing papers by "Kyungpook National University published in 1987"

Design and Economic Evaluation of Cellulose Hydrolysis Processes

Abstract: In this chapter, commercial hydrolysis processes for a variety of cellulosic materials are described; both enzymatically and acidically catalyzed processes are included. It appears, however, that the former remains largely at the conceptual or developmental stage; most of the commercial processes in operation, while rather limited in number, are said to belong to the latter. Nevertheless, the procedure for process economic evaluation and optimization of hydrolysis of cellulosic materials is illustrated with two examples from the former one utilizing relatively pure cellulose and the other lignocellulosic material as substrates, because of the future potential of the enzymatically catalyzed processes.

Acid Hydrolysis of Cellulose

Abstract: Cellulosic materials consist of three major components, namely, cellulose, hemicellulose, and lignin. The two modes of converting the carbohydrate components into their constituent sugars are enzymatic hydrolysis and acid hydrolysis. The former has been reviewed in the preceding chapter [38,39, 81 ]. The present chapter covers the latter with the focus on mechanism and kinetics of acid hydrolysis.

Nature of Cellulosic Material

Abstract: The hydroysis of native lignocellulosics, especially that catalyzed by enzyme, is a slow process. The heterogeneous degradation of lignocellulosics is governed primarily by their structural features since (1) cellulose present in biomass possesses a highly resistant crystalline structure, (2) lignin surrounding the cellulose forms a physical barrier, and (3) the reactive sites available are limited. The cellulose present in lignoeellulosics is composed of crystalline and amorphous components [7]. The amorphous component is usually more reactive than the crystalline component, and thus any means that will increase the amorphous content will enhance the hydrolysis rate [12,16,17, 50]. The presence of lignin forms a physical barrier for attack by either enzyme or acid molecules; therefore, treatments causing disruption of the lignin seal will increase the accessibility of cellulose to enzyme or acid molecules and eventually its hydrolysis rate. The limitation of available reactive sites stems from the fact that the average size of the capillaries in biomass is too small to allow the entry of reactive molecules, especially the large enzyme molecules.

Convection Patterns in the Polar Ionosphere for Northward IMF Inferred from Ground-Based Magnetometer Data

Abstract: Instantaneous, not statistical, convection patterns in the polar ionosphere are examined for periods of the northward interplanetary magnetic field (IMF) on the basis of the equivalent ionospheric current systems obtained from data of the IMS ground magnetometer. The equivalent current system is sufficient for this purpose, as long as one knows the relationship between the equivalent current system and the electrostatic potential distribution for such relatively quiet periods when no great spatial gradients in the ionospheric conductivity are expected to be present in the polar cap. In spite of the complexity of individual patterns, the following characteristic features are found. (1) During the late recovery phase of substorms, the clockwise current vortex in the postmidnight sector decays more rapidly than the counterclockwise one in the dusk sector. (2) As the IMF Bz component increases, a current system consisting of two current vortices with a sunward convection flow between them appears in the polar cap region. (3) As the IMF Bz component decreases, the clockwise current vortex in the afternoon sector decays rapidly while the counterclockwise vortex in the noon sector is shifted toward the afternoon sector. In the meantime, a new clockwise vortex emerges in the nightside and becomes enhanced.Thus the whole current system evolves gradually into the familiar two-cell type with an antisunward convection flow over the polar cap. In particular, it is important to note that all these changes occur before the IMF turns southward. (4) The effect of the IMF By dependence on the equivalent current system is also confirmed on our instantaneous data base during a prolonged Bz positive condition.

Thomas precession, Wigner rotations and gauge transformations

Abstract: The exact Lorentz kinematics of the Thomas precession is discussed in terms of Wigner’s O(3)-like little group which describes rotations in the Lorentz frame in which the particle is at rest. A Lorentz-covariant form for the Thomas factor is derived. It is shown that this factor is a Lorentz-boosted rotation matrix, which becomes a gauge transformation in the infinite-momentum or zero-mass limit.

Ultrastructural and phenotypic changes in Langerhans cells induced in vitro by contact allergens.

Abstract: SUMMARY Ultrastructural changes of murine Langerhans cells (LC) were examined following exposure of crude epidermal cell suspensions to the contact allergens dinitrochlorobenzene, nickel sulphate and lead nitrate at various concentrations and for various incubation times. An immunogold labelling technique was employed to study changes in surface expression of MHC Class II (Ia) molecules. In all cases, activation of LC was evident after as little as 15 min exposure and was characterized by a marked increase in surface expression of Ia molecules, prominent rough endoplasmic reticulum and numerous ribosomes and lysosomes. Degenerative changes in LC were apparent to varying degrees depending on the allergen, its concentration and the time of incubation. Degenerative changes included swollen mitochondria, membrane disruption or rupture, loss of density of the cytoplasm (cytolysis), loss of dendritic processes and decreased expression of Ia molecules. In the case of dinitrochlorobenzene, degenerative changes were present and usually severe at concentrations greater than 10 μg/ml, while exposure to nickel sulphate and lead nitrate was associated with only mild degenerative changes, These observations indicate that contact allergens have a variety of direct effects on LC, including activation and degeneration, which are dose- and time-dependent. Since these alterations of LC were observed in the absence of other immunologically active cells, peripolesis cannot be involved in these events.

Mesozoic granitic rocks of South Korea: Trace element evidence regarding their differentiation

Abstract: To understand the mode of differentiation of the Jurassic and Cretaceous granitic magmas in South Korea, a neutron activation analysis has been made to measure the REE abundance of the granitic rocks. We used the Rayleigh fractionation model as a crystallization model of the granitic melts. Since the model calculations fit the REE data for the Cretaceous granitic rocks very well, it is suggested that the Cretaceous granitic magma in South Korea were mainly differentiated by fractional crystallization. Because the REE patterns for the Jurassic granitic rocks do not show large negative Eu anomalies, it is difficult to consider that the Jurassic granitic magmas were chiefly differentiated by fractional crystallization.

A quadratic regulator with cheap control for a class of nonlinear systems

Abstract: A quadratic regulator problem for a class of nonlinear systems is considered in which the control cost is multiplied by a small parameter, which becomes a so-called cheap control problem Conditions are found under which the minimum cost becomes zero (perfect regulation) and the linear part in the optimal control law becomes dominant as the small parameter goes to zero Near optimality of control laws truncated from the optimal control law in series form is also found

Adaptive image restoration using local statistics and directional gradient information

Abstract: We present an adaptive restoration algorithm to effectively restore an image degraded by additive white Gaussian noise using local statistics and directional gradient information in the spatial domain. The proposed algorithm is a modified Lee algorithm considered to compensate its drawback that little noise is removed at edge regions even though the edges are well preserved. Experimental results show better performance than for conventional algorithms.

Analysis of a narrow slit in a parallel-plate transmission line: E-polarisation case

Abstract: The integro-differential equation is formulated for the equivalent magnetic current in the narrow slit in a parallel-plate transmission line when excited by an E-polarised, dominant (TE) mode wave. A solution (magnetic current) is presented to the approximated integro-differential equation for the narrow slit case. From knowledge of the magnetic current, the normalised resistance and reactance of the slit are computed.

Preparation of NiO-ZrO2/SO 4 -2 catalyst and its catalytic activity for ethylene dimerization

Abstract: NiO-ZrO2/SO 4 -2 catalysts were prepared by coprecipitation from the solution of nickel chloride -zirconium oxychloride mixture followed by treating with H2SO4 NiO-ZrO2 alone without SO 4 -2 was inactive as a catalyst for ethylene dimerization, but NiO-ZrO2/SO 4 -2 was found to be very active even at room temperature. The high catalytic activity of NiO-ZrO2/SO 4 -2 was closely correlated with the increase of acid strength by the inductive effect of sulfate ion adsorbed on NiO-ZrO2. The decrease of catalytic activity above 150‡C of evacuation temperature was explained in terms of the structural change of catalyst from amorphous phase to crystalline, and the sintering.

Serological cross-reactivity between Sarcocystis and Toxoplasma in pigs.

Abstract: The development of antibody titers and cross reation between Sarcocystis and Toxoplasma were investigated by means of IFA test and ELISA in pigs experimentally infected with 1.5 x 10(6) S. suicanis sporocysts and 10,000 T. gondii oocysts, respectively. The intact and soluble Sarcocystis antigens were prepared from the bradyzoites harvested by peptic digestion of infected pork. The intact and soluble Toxoplasma, antigens were prepared from the tachyzoites in mouse peritoneal cavity. IgG antibodies in pigs infeded with Sarcocystis and Toxoplasma, respectively were detected first at 2 weeks post infection on both IFA test and ELISA. The antibody titer to Toxoplasma reached its maximum at 6 weeks post infection and decreased thereafter. The antibody titer to Sarcocystis reached its maximum terminally. The cross-reaction titer in pigs infected with Toxoplasma against Sarcocystis antigen was up to 1:16 in IFA test and up to 1:32 in ELISA. The titer in control group was below 1:4 in both reactions.

Theory of direct-interband-transition line shapes based on Mori’s method

Abstract: A theory of direct interband optical transitions in the electronphonon system is introduced on the basis of the Kubo formalism and by using Mori’s method of calculation. The line shape functions are introduced in two different ways and are compared with those obtained by Choi and Chung based on Argyres and Sigel’s projection technique.

Expression of HLA-DR and OKT6 antigens on keratinocytes and dendritic cells in pemphigus

Abstract: The expression of HLA-DR and OKT6 antigens by epidermal cells in pemphigus was examined by immunohistochemical methods using skin biopsy specimens from human patients with pemphigus vulgaris. Changes in the distribution and subpopulations of Langerhans cells were observed in lesional (involved) skin. HLA-DR-positive, OKT6-negative dendritic cells were numerous and generally confined to the margins of epidermal clefts. OKT6-positive dendritic cells were rare or absent in lesional skin. The HLA-DR-positive, OKT6-negative dendritic cells associated with intraepidermal clefts are most likely functionally active antigen-presenting cells, which may play a role in lesion development. Aberrant expression of HLA-DR molecules by keratinocytes was observed in both involved and uninvolved skin, and may function to facilitate the recognition of surface-bound pemphigus antigen(s) by immunocompetent cells.

Isoprene polymerization with cerium(III) acetylacetonate–diethylaluminum chloride in toluene: Effects of water concentration

Abstract: Isoprene has been polymerized in toluene using a cerium(III) acetylacetonate–diethylaluminum chloride catalyst. The microstructure of obtained polyisoprene is predominantly trans-1,4 structure. For this system the effects of water concentration on the conversion of isoprene to polymer, the microstructure and the molecular weight of polyisoprene have been examined. The conversion at a given polymerization time has a maximum at [H2O]/[DEAC] ratio of 1:0–1.1. The amounts of trans-1,4 structure and the viscosity average molecular weights of polyisoprene are nearly independent of the water concentration. Although the conversion increases with the concentration of catalyst, the trans-1,4 content is not affected by the catalyst concentration and the molecular weight of polyisoprene decreases slightly with increasing catalyst concentration.

Basic characteristics of surface microcracks in type 304 stainless steel at 538°C

Abstract: This paper deals with the basic characteristics of surface micro-cracks on unnotched smooth specimens of Type 304 stainless steel under creep and creep-fatigue condition with holding time of 1 and 10 minutes respectively at 538°C in air. The behaviors of the microcracks have been analysed via surface replica method and photomicrographs techniques. Quantitative information, such as initiation period, growth and coalescence behavior, statistical distributions of crack length, density of cracks, distribution patterns and crack growth properties, was obtained. Knowledge of these parameters is critical for the application of fracture mechanics to the life assessment and the damage evaluation of structures at elevated temperature.

Mycoses in Korea

Abstract: In Korea, ringworm, tinea versicolor and cutaneous candidosis are the principal fungal infections. Around the outbreak of the Korean War, tinea capitis was the most frequent clinical type of ringworm due to its nation-wide epidemic, but it has been rapidly reduced since 1960. In recent years, tinea pedis and manuum as a whole, occupy over half of the total cases of ringworm; tinea cruris, tineafaciei and corporis have an increasing tendency to show atypical clinical manifestations. In the last 10 years the aspect of dermatophytic flora has remarkably changed compared with that seen around World War II. While Trichophyton ferrugineum, the principal causative organism of tinea capitis and tinea corporis in the past, has been abruptly decreasing in frequency since 1960. Microsporum canis has spread all over the country and T. rubrum is increasing. The number of tinea capitis due to M. canis, which was isolated for the first time in 1957, has been increasing steadily every year especially since 1978. During 10 years from 1976 to 1985, the total number of cases with dermatophytoses observed at Chilgok Catholic Skin Clinic in Taegu was 34, 261, representing 14.2% of the total new out-patients. Of these, tinea pedis was the most frequent (40.4%), followed by tinea cruris (23.8%), tinea faciei and corporis (12.9%), tinea unguium (10.7%), tineamanuum (8.5%), tinea capitis (3.7%) and tineafavosa (2 cases). The total number of dermatophytes isolated during the same 10-year-period was 21, 754 strains, composed of T. rubrum (77.6%), T. mentagrophytes (10.8%), M. canis (7.2%), Epidermophyton floccosum (3.7%), M. gypseum (0.4%), T, ferrugineum (0.3%) and T. schoenleinii (2 strains). In viewing of teleomorphic state, M. canis exhibited only Nannizzia otae “-” mating type. Among 474 strains of T. mentagrophytes, 225 were Arthroderma vanbreuseghemii “+” mating type, with the remaining 249 being “-”. “+” Type of A. vanbreuseghemii was frequently identified in tinea pedis and unguium, while “-” type in tinea capitis, tinea faciei and corporis, tinea manuum. In case of M. gypseum, N. incurvata and N. gypsea have been isolated at almost the same rate. Sporotrichosis is rare but occurs sporadically throughout the country, showing no evidence of increasing. Inrecent years, although very rare, infections due to Cryptococcus neoformans, Phoma species, Fusarium species, Paecilomyces lilacinus, Wangiella dermatitidis have been reported. Deep mycoses seem very rare. Pulmonary infections due to Aspergillus, Cryptococcus, Candida albicans and Pseudallescheria boydii have been observed. Diseases such as tinea imbricata, tinea nigra, chromomycosis and coccidioidomycosis, which are observed in the other nations, have not been described.

Rotations and gauge transformations

Abstract: The energy-momentum r e l a t i o n for a n o n r e l a t i v i s t i c p a r t i c l e is E : P?/2m, whi le that for a massless p a r t i c l e is E = P. I t was Einstein who un i f i ed these two re la t i ons through his formula E = [p2 + m211/2 In add i t ion to the fourmomentum, a r e l a t i v i s t i c p a r t i c l e has i t s in te rna l space-time degrees o f freedom. When the p a r t i c l e is slow or at res t , the space-time symmetry manifests i t s e l f through by the spin. On the other hand, i f the p a r t i c l e is massless, i t has the h e l i c i t y and gauge degrees of freedom. ~ e question is whether the in te rna l space-time symmetries for massive and massless pa r t i c l es can be un i f i ed . In order to study th i s problem, we use Wigner's l i t t l e groups. I The l i t t l e group is the maximal subgroup o f the Lorentz group which leaves the four-momentum of the p a r t i c l e i nva r i an t . In order to construct a t ransformation which leaves the four-momentum i n v a r i a n t , l e t us consider a p a r t i c l e moving along the z d i r e c t i o n with v e l c i t y parameter m. We can ro ta te th is p a r t i c l e around the y axis by e. We can then make a boost to come back to the o r i g i n a l momentum, me four-momentum is unchanged under th i s boost preceded by the above-mentioned r o t a t i o n . 2 The matr ix which performs th i s t ransformat ion is

A theory of noise based on generalized random walks

Abstract: Based on a generalized random walks (GRW) model proposed by one of the present authors, a theory of noise is developed. In the present system, two different types of randomness, internal and external, are considered. Internal noises yield the ususal randomness for a walker and lead one to a description based on random walks. External noises appear as additional fluctuations around the original processes. Jumping probabilities are composed of the corresponding two types of randomness. It is shown that a specification of these jumping reduces the present basic equation to the expression used in the conventional noise theory.

Preparation of Linear Low Density Polyethylene with Titanium Tetra- n -butoxide-Diethylaluminum Chloride Catalyst in Slurry Phase

Abstract: Preparation of Linear Low Density Polyethylene with Titanium Tetra- n -butoxide-Diethylaluminum Chloride Catalyst in Slurry Phase