Tae-Won Lee

Highly Effective Electromagnetic Interference Shielding Materials based on Silver Nanowire/Cellulose Papers

We fabricated silver nanowire (AgNW)-coated cellulose papers with a hierarchical structure by an efficient and facile dip-coating process, and investigated their microstructures, electrical conductivity and electromagnetic interference (EMI) shielding effectiveness. SEM images confirm that AgNWs are coated dominantly on the paper surfaces, although they exist partially in the inner parts of the cellulose papers, which demonstrates that the AgNW density gradually decreases in thickness direction of the AgNW/cellulose papers. This result is supported by the anisotropic apparent electrical conductivity of the AgNW/cellulose papers depending on in-plane or thickness direction. Even for a AgNW/cellulose paper obtained by a single dip-coating cycle, the apparent electrical conductivity in the in-plane direction of 0.34 S/cm is achieved, which is far higher than the neat cellulose paper with ∼10(-11) S/cm. In addition, the apparent electrical conductivity of the papers in the in-plane direction increases significantly from 0.34 to 67.51 S/cm with increasing the number of dip-coating cycle. Moreover, although the AgNW/cellulose paper with 67.51 S/cm possesses 0.53 vol % AgNW only, it exhibits high EMI shielding performance of ∼48.6 dB at 1 GHz. This indicates that the cellulose paper structure is highly effective to form a conductive AgNW network. Overall, it can be concluded that the AgNW/cellulose papers with high flexibility and low density can be used as electrically conductive components and EMI shielding elements in advanced application areas.

Spawning Area of the Japanese Eel

The millennium-old mystery of eel spawning that has fascinated naturalists since the time of Aristotle still remains largely unsolved. There are only 3 species, the European eel, Anguilla anguilla, the American eel, A. rostrata, and the Japanese eel, A. japonica, for which the general spawning areas have been successfully outlined so far, but the spawning areas of the other 12 species of the genus Anguilla worldwide are still not well understood. In addition, even in the Atlantic Ocean, which has a long history of eel research, no one has ever observed spawning adults or collected eggs at the estimated spawning area in the Sargasso Sea. With respect to this point, the problem of the breeding place of freshwater eels has yet to be solved. Thus, research interest in eel migration is still focused on the actual spawning location for anguillid eels.

Microstructural growth in otoliths of black rockfish, sebastes schlegeli , from prenatal larval to early juvenile stages

Microstructural growth in the sagittae ofSeastes schlegeli, a viviparous scorpaenid, is described from prenatal larval to early juvenile stages, and related to morphological changes. Embryos and prenatal larvae were extruded from a gravid female from 21 d prior to birth onwards, and released larvae reared and sampled up to 58 d after birth. Eggs hatched in the ovary 14 d prior to birth. At this time, otoliths consisted of a core surrounded by a prominent check, similar to the otolith structure seen in oviparous fishes. Fourteen growth increments had been deposited by birth. The parturition mark it-self comprised a prominent check and narrow growth increment Growth increments were deposited daily from hatching up to 58 d after birth, whereas accessory primordia first appeared in otoliths by ca. 32 d after birth, at a specimen total length of ca. 13 mm. This corresponded to the period during which the larvae metamorphosed into juveniles. Otoliths grew exponentially during the larval stage and linearly during the juvenile stage. when plotted against total length. Growth in total length from hatching to 58 d after birth could be represented by the Gompertz curve.

Regenerated cellulose/multiwalled carbon nanotube composite films with efficient electric heating performance.

We have manufactured regenerated cellulose-based composite films reinforced with pristine multiwalled carbon nanotube (MWCNT) by a facile casting of cellulose/DMAc/LiCl solutions containing 0.2-10.0wt% MWCNT and have investigated their application as electric heating materials by examining microstructure, thermal stability, and electrical properties. TEM images showed that the pristine MWCNT was dispersed well in the regenerated cellulose matrix. The composite films were found to be stable thermally up to ∼275°C. The electrical resistivity of the regenerated cellulose/MWCNT composite films decreased significantly from ∼10(9)Ωcm to ∼10(1)Ωcm with increasing the MWCNT loading, particularly at a certain MWCNT content between 2.0 and 3.0wt%. Accordingly, the composite films with 5.0-10.0wt% MWCNT contents, which possessed low electrical resistivity of ∼10(2)-10(1)Ωcm, exhibited excellent electric heating performance in aspects of temperature responsiveness, steady-state maximum temperature, and electrical energy efficiency at constant applied voltages. For instance, the composite film with 10.0wt% MWCNT had well-controlled steady-state maximum temperatures of 40-189°C at 20-80V, characteristic temperature growth constant of ∼1s, and electric power efficiency of ∼5.4mW/°C, which performance remained unchanged under repeated experiments for several hours.

Age, Growth, and Maturity of Chub Mackerel off Korea

Abstract The age, growth, and maturity of chub mackerel Scomber japonicus were determined by otolith analysis and gonad observation. Fish were subsampled monthly from Korean offshore commercial catches between September 1994 and August 1995. Gonad observations suggest that chub mackerel spawned mainly in May. The size at 50% maturity was calculated to be 28.8 cm fork length at an age of 1.01 years. Annuli in otoliths can be distinguished from false annuli because the true annuli were formed continuously all around the sagittal plane as distinct dark marks. They were mainly formed in May, coinciding with the main spawning season. Chub mackerel grew to over 20 cm by December and attained up to 28 cm in 1 year. Thereafter, the growth rate slowed down. The age composition was 40.2, 42.5, 15.4, 1.7, and 0.1% for age-groups 0–4, respectively. Using three different approaches, the von Bertalanffy growth parameter was estimated to be between 1.51 and 2.19 and the maximum length between 34.1 and 34.6 cm. The growt...