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Early Gonadal Differentiation of the Protogynous Red Spotted Grouper, Epinephelus akaara
김현규,Jung-Hyun Kim,Woo Sik Kim,백혜자,권준영 한국발생생물학회 2015 발생과 생식 Vol.19 No.4
Red spotted grouper, Epinephelus akaara is a popular aquaculture species in many Asian countries. This species is a protogynous hermaphrodite that first differentiates into female and changes to male later. Due to this reproductive characteristic, stable supply of male and female gametes is a key to the success of seed production in this species. Thus, understanding early gonadal differentiation is required to develop effective sex control techniques. Red spotted grouper were reared in indoor tanks and sampled every 5 days from 40 days post-hatch (DPH) to 130 DPH. Changes of gonadal tissues were examined and analyzed by means of histology. A pair of gonadal primordium has already existed underneath the kidney in the posterior part of the body cavity at 38 DPH when this study began. Gonadal primordia of 38, 40 DPH consisted of germ cells surrounded by a few somatic cells. The blood vessel was observed in the gonadal primordium at 45 DPH. The number of somatic cells and size of gonadal primordium increased age-dependently up to 60 DPH. Formation of ovarian cavity was obvious by two protuberant aggregations of somatic cells at 65 DPH. Completed ovarian cavity and oogonia were first observed in the gonad of one fish sample at 105 DPH. Based on these histological observations, it can be suggested that induction of primary male differentiation could be more successfully applied at around 60 DPH in this species.
대체에너지 분야에서의 촉매기술 심포지엄 2 : F-33
김현규,장점석,지상민,배상원,손효창,이재성 한국화학공학회 2007 화학공학의이론과응용 Vol.10 No.2
Perovskite-type oxide materials based on transition metals are efficient photocatalysts for overall water splitting with high quantum yields. However, the band gaps of these materials (ca. 3.8-4 eV) are not adequate for visible light-induced photocatalysis. The development and fabrication of materials showing photocatalytic activity for water splitting into H2 and O2 and degradation of organic pollutants under visible light irradiation, therefore, is the most important topic in the photocatalysis research today. In search of novel oxide photocatalysts with high photocatalytic activity under visible light irradiation, we have investigated a vast number of perovskite-type oxides, and discovered that PbBi2Nb2O9, an Aurivillius phase type layered perovskite containing bismuth (Bi3+) was an efficient photocatalyst for water splitting and degradation of organic pollutants under visible light irradiation (420nm).
An adaptive procedure based on combining finite elements with meshless methods
김현규,김혜영 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.8
This paper presents a new method for combining finite elements with meshless methods, which increases the accuracy of computational solutions in a coarse mesh by adding nodes in the domain of interest. The present method shares the features of the finite element and meshless methods such as (a) the meshless interpolation of the MLS type is employed; (b) integration domains are consistent with support domains; and (c) essential boundary conditions can be applied directly. In the present method, a ground mesh with triangular or quadrilateral elements is constructed to define polygonal support domains, and then additional nodes are placed arbitrarily in a domain without the reconstruction of a mesh. The method is very useful in an adaptive calculation, because nodes can be easily added or removed without any remeshing process.