Comparison between Wild and Hatchery Populations of Korean Pen Shell (Atrina pectinata) Using Microsatellite DNA Markers

Pen shell (Atrina pectinata) is a popular food source with a high commercial value in a number of Asian Pacific areas. The natural A. pectinata population has been declining continuously over the past several decades. Microsatellite DNA markers are a useful DNA-based tool for monitoring the genetic variation of pen shell populations. In this study, 20 polymorphic microsatellite (MS) DNA markers were identified from a partial genomic pen shell DNA library enriched in CA repeats, and used to compare allelic variation between wild and hatchery pen shell populations in Korea. A total of 438 alleles were detected at the 20 MS loci in the two populations. All loci were easily amplified and demonstrated allelic variability, with the number of alleles ranging from 5 to 35 in the wild population and from 5 to 22 in the farmed population. The average observed and expected heterozygosities were 0.69 and 0.82, respectively, in the hatchery samples and 0.69 and 0.83, respectively, in the wild samples. Statistical analysis of fixation index (F(ST)) and analysis of molecular variance (AMOVA) showed minor, but significant, genetic differences between the wild and hatchery populations (F(ST) = 0.0106, CI(95%) = 0.003-0.017). These microsatellite loci may be valuable for future aquaculture and population genetic studies for developing conservation and management plans. Further studies with additional pen shell samples are needed to conclusively determine the genetic diversity between the wild and hatchery populations.     

Effect of Nafion ionomer and catalyst in cathode layers for the direct formic acid fuel cell with complex capacitance analysis on the ionic resistance

Using platinum (Pt) black and carbon-supported Pt (Pt/C) as cathode catalysts, membrane-electrode assemblies (MEAs) were fabricated with various Nafion ionomer content, and their direct formic acid fuel cell (DFAFC) performances were investigated. In MEAs incorporating Pt black catalysts, the current density at 0.6 V was highest at ionomer/catalyst volume ratio of 1.0, which was consistent with the electrochemical active area (EAS) variation measured by cyclic voltammetry. However, the current density measured at 0.3 V, the cell performance increased with Nafion ionomer content, especially at low ionomer loading, indicating that proton transport rate played an important role. The variation in ionic resistance (R_ion) of cathode layers with Nafion ionomer content was experimentally confirmed by using the complex capacitance analysis of impedance data implemented with nitrogen (cathodes)/hydrogen (anodes) atmosphere. For Pt/C, the layer thickness and EAS of cathode were larger than those of MEA cathode using Pt black; and the current densities at 0.6 V were lower than those of Pt black, suggesting that smaller fraction of EAS was utilized.     

Effects of (NH4)2SO4 and BTA on the nanostructure of copper foam prepared by electrodeposition

Copper foam with dendritic copper nanostructure was synthesized by an electrodeposition process using hydrogen bubbles as dynamic templates. To modify the morphology of the copper nanostructure in the foam walls, (NH₄)₂SO₄ and BTA (benzotriazole) were introduced into the electrolytic bath as chemical additives, and their influences on the morphologies and the structural characteristics of copper deposits were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanical strength and stiffness of the copper foam were evaluated by the compression test. The corncob-like deposits of the copper foam were changed to needle-like nanodendrites by the addition of (NH₄)₂SO₄, which significantly improved the mechanical strength and stiffness due to the self-supporting effects of the tightly interlocked needle-like nanodendrites. In contrast, the copper foam prepared from the solution with (NH₄)₂SO₄ and BTA shows high ductility but low mechanical strength due to the formation to grape-like copper deposits. Both the copper foams exhibited higher mechanical properties than the one with corncob-like deposits formed in the additive-free solution. The reaction mechanism of (NH₄)₂SO₄ and BTA on the nanostructure of the copper foam at high cathodic current density was clarified by analyzing the effects of the additives on the copper deposition reaction and hydrogen gas evolution reaction, respectively.     

Effect of wall friction on variation of formwork pressure over time in self-consolidating concrete

In order to accurately predict the varying of formwork pressure over time, it is necessary to consider various factors influencing the development of formwork pressure. A prediction model has been previously proposed, but that model has some limitations in that only intrinsic material characteristics are taken into account. Extrinsic effects such as wall friction, formwork flexibility, and external temperature are excluded in the model. This study focuses on the wall friction effect as one of the extrinsic factors. First, by incorporating the intrinsic model and friction stress acting on the interface, a method of calculating formwork pressure considering the wall friction effect is suggested. To find out how much friction stress is acting on the interface and how it varies over time, formwork pressure tests were performed with circular column formworks having three different diameters. In these columns, the vertical pressure at the bottom and the lateral pressures were measured. To calibrate parameters of the intrinsic model for the same material as that used in the formwork pressure tests, additional tests were conducted with a specially designed apparatus that can exclude effects of extrinsic factors. From tests and analysis results, it was found that wall friction greatly affects the variation of formwork pressure over time. The newly suggested calculation method can give a good prediction of real formwork pressure.     

Assembly of strands of multiwall carbon nanotubes and gold nanoparticles using alkanedithiols

Multiwall carbon nanotubes and gold nanoparticles (MWCNT–AuNP) were assembled into strands by cross-linking with alkanedithiols. Long MWCNT strands were first shortened to ∼0.25 μm by chemical oxidation followed by ball-milling, and then thiolated by reaction with cysteamine. The thiol groups on the surfaces of the MWCNT strands combined with Au nanoparticles to produce MWCNT–AuNP strands. A simple mixing of these strands with alkanedithiols resulted in an assembly of strands linked by the alkanedithiols which adsorbed onto the surfaces of the AuNPs attached to the MWCNT–AuNP strands. Short MWCNT–AuNP strands connected to one another in a parallel arrangement, whereas long strands assembled in a crossing arrangement. The possibility of using this method to chemically bond MWCNTs to lower the contact resistance of thin CNT films is discussed.     

Alignment of a nematic liquid crystal on nano‐grooved material

We demonstrate the alignment characteristics of a nematic liquid crystal on the surface of a nanoimprinted material that is a functionally graduated composite suitable for the alignment of a liquid crystal on a groove surface processed by nanoimprinting lithography. With the electro‐optic characteristics shown in twisted nematic and in‐plane switching modes, the potential liquid crystal applications are examined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of poly(ε‐caprolactone)/clay nanocomposites using polyhedral oligomeric silsesquioxane surfactants as organic modifier and initiator

Poly(ε‐caprolactone)/clay nanocomposites were synthesized by in situ ring‐opening polymerization of ε‐caprolactone in the presence of montmorillonite modified by hydroxyl functionalized, quaternized polyhedral oligomeric silsesquioxane (POSS) surfactants. The octa(3‐chloropropyl) polyhedral oligomeric silsesquioxane was prepared by hydrolytic condensation of 3‐chloropropyltrimethoxysilane, which was subsequently quaternized with 2‐dimethylaminoethanol. Montmorillonite was modified with the quaternized surfactants by cation exchange reaction. Bulk polymerization of ε‐caprolactone was conducted at 110°C using stannous octoate as an initiator/catalyst. Nanocomposites were analyzed by X‐ray diffraction, transmission electron microscopy, thermo gravimetric analysis, and differential scanning calorimetry. Hydroxyl functionalized POSS was employed as a surface modifier for clay which gives stable clay separation for its 3‐D structure and also facilitates the miscibility of polymer with clay in the nanocomposites due to the star architecture. An improvement in the thermal stability of PCL was observed even at 1 wt % of clay loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and characterization of high‐molecular‐weight sericin by γ irradiation

We conducted this study to examine the changes in the molecular structure and physiological activities of silk sericin after γ irradiation. Sericin from Bombyx mori was extracted with an Na₂CO₃ solution. The molecular weight distribution of sericin increased in the gel permeation chromatography and sodium dodecyl sulfate/polyacrylamide gel electrophoresis results as the irradiation dose increased. Circular dichroism data also revealed that the α‐helix contents decreased with the irradiation dose. Ultraviolet absorption was shown a different pattern between the irradiated and unirradiated sericin. However, the Fourier transform infrared spectrum was not changed in all of the groups. Furthermore, the irradiated sericin was significantly increased in 2,2‐diphenyl‐1‐picryl‐hydrazil radical scavenging, and the tyrosinase inhibitory activities increased with irradiation dose. Therefore, γ irradiation was an effective method for producing high‐molecular‐weight sericin and for developing functional foods and cosmetics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Extinction effectiveness of pyrogenic condensed-aerosols extinguishing system

We studied the extinction effectiveness of pyrogenic condensed-aerosols in gaseous fire extinguishing systems through the ISO (International Organization for Standard) 15779. The thermal characteristics of solid aerosols as an extinguishing agents were evaluated by using TG and DTA. The modified closed pressure vessel test (MCPVT) and the conductivity of the solid aerosol extinguishant were also measured to ensure the safety of extinguishant. The TG and DTA result showed that the resin added to the main component of Potassium Nitrate (PN) has the effectiveness to mitigating the exothermic reaction of the pyrogenic condensed-aerosol extinguishant. The results of maximum height test revealed the extinguishing capability of a pyrogenic condensed-aerosol extinguishing agent as a gaseous extinguishing system.     

Reaction sequence and electrochemical properties of lithium vanadium oxide cathode materials synthesized via a hydrothermal reaction

Lithium vanadium oxide (Li_1+xV₃O₈) cathode materials were synthesized via a simple hydrothermal reaction followed by heat treatment at 300 or 400 °C. From both XRD and TG/DTA analyses, a detailed comprehensive reaction sequence for the formation of single-phase LiV₃O₈ is proposed. Li_1+xV₃O₈ (x=0.2) materials with different thermal histories show clear differences in morphologies and sizes, although they maintained an impurity-free single phase regardless of thermal treatment. Samples that were heat treated at 300 °C show an agglomerated particle shape with many nanorod-like Li_1+xV₃O₈ particles over the surface that enhance the surface area of the particles. In contrast, samples treated at 400 °C have a bi-modal particle size distribution with improved crystallinity. Such differences in morphologies clearly influence the electrochemical properties. LiV₃O₈ cathode materials that were treated at 300 and 400 °C showed initial discharge capacacities of 346.52 and 261.23 mA h/g, respectively, and discharge capacities of 78.66 and 157.35 mA h/g, respectively, after 100 cycles. The improved cyclability of LiV₃O₈ cathode materials that were heat treated at 400 °C is due to their increased crystallinity and structural stability.