Perfluoroalkyl acids in the egg yolk of birds from Lake Shihwa, Korea

Concentrations of perfluoroalkyl acids (PFAs) were measured in egg yolks of three species of birds, the little egret (Egretta garzetta), little ringed plover (Charadrius dubius), and parrot bill (Paradoxornis webbiana), collected in and around Lake Shihwa, Korea, which receives wastewaters from an adjacent industrial complex. Mean concentrations of perfluorooctanesulfonate (PFOS) ranged from 185 to 314 ng/g ww and were similar to those reported for bird eggs from other urban areas. Long-chain perfluorocarboxylic acids (PFCAs) were also found in egg yolks often at great concentrations. Mean concentrations of perfluoroundecanoic acid (PFUnA) ranged from 95 to 201 ng/g ww. Perfluorooctanoic acid was detected in 32 of 44 egg samples, but concentrations were 100-fold less than those of PFOS. Relative concentrations of PFAs in all three species were similar with the predominance of PFOS (45-50%). There was a statistically significant correlation between PFUnA and perfluorodecanoic acid in egg yolks (p < 0.05), suggesting a common source of PFCAs. Using measured egg concentrations and diet concentrations, the ecological risk of the PFOS and PFA mixture to birds in Lake Shihwa was evaluated using two different approaches. Estimated hazard quotients were similar between the two approaches. The concentration of PFOS associated with 90th centile in bird eggs was 100-fold less than the lowest observable adverse effect level determined for birds, and those concentrations were 4-fold less than the suggested toxicity reference values. On the basis of limited toxicological data, current concentrations of PFOS are less than what would be expected to have an adverse effect on birds in the Lake Shihwa region.     

Development of antimicrobial polyolefin films containing lauroyl arginate and their use in the packaging of strawberries

Low-density polyethylene (LDPE) films were supplemented with lauroyl arginate ethyl (LAE) and characterized for physical, mechanical and antimicrobial properties as well as their use for fresh ‘Sulhyang’ strawberries packaging. LAE powder was added into the LDPE films at 0, 1, 3, 5, and 10% (w/w) and assessed for physical properties, gas permeation, thickness and color values. The results showed that incorporation of LAE into the LDPE matrix did not affect film thickness and color. The thermal stability of the LAE/LDPE film decreased with increasing concentrations of LAE. The LAE/LDPE film exhibited a rough surface and compact structure. Tensile strength were affected by addition of LAE on the other hand value of elongation at break were increased. The LAE/LDPE containing 5 and 10% LAE showed significant antimicrobial properties against mycelium growth. Further, 5 and 10% LAE/LDPE films were used for storage study and it showed that incorporation of LAE into LDPE film was an effective method for maintaining the quality of strawberries. Films containing LAE were very effective at reducing the total weight loss, maintaining firmness, and reduced fungal decay compared to the control strawberries at 10?°C. These results suggest that LAE/LDPE films are potential candidates for advanced packaging materials for the fruits packaging application.     

Optical and electrical nano eco-sensors using alternative deposition of charged layer

This review focuses on layer by layer (LBL) assembly-based nano ecological sensor (hereafter, eco-sensor) for pesticide detection, which is one of the most versatile methods. The effects of pesticides on human health and on the environment (air, water, soil, plants, and animals) are of great concern due to their increasing use. We highlight two of the most popular detecting methods, i.e., fluorescence and electrochemical detection of pesticides on an LBL assembly. Fluorescence materials are of great interest among researchers for their sensitivity and reliable detection, and electrochemical processes allow us to investigate synergistic interactions among film components through charge transfer mechanisms in LBL film at the molecular level. Then, we noted some prospective directions for development of different types of sensing systems.     

Hygrothermal effect on henequen or silk fiber reinforced poly(butylene succinate) biocomposites

The hygrothermal effect of poly(butylene succinate) biocomposites reinforced with silk or henequen fibers was investigated. The biocomposites were fabricated using a compression molding method. The biocomposites were maintained in the chamber at 60 °C and 85% RH for 1000 h. The results show that the degradation of PBS matrix is the main cause for the deterioration of biocomposites performance and the biocomposites degraded much slowly than PBS matrix did. The storage modulus for the biocomposites exposed at 60 °C and 85% RH for 1000 h was decreased 20% and 50% with the silk and henequen fibers comparing to the original specimens, respectively.     

Structural and electrochemical properties of Ag nano-dots combined amorphous Si electrodes for thin-film lithium rechargeable batteries

We have one-pot fabricated Si-based nanocomposite electrodes containing Ag nano-dots for thin-film Li rechargeable batteries by a co-sputtering method. The structural and electrochemical properties of the Si/Ag nanocomposite electrodes are investigated via transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and cycler. The TEM and XRD results show that crystalline Ag nano-dots (approximately 5-9 in size) are well-dispersed within an amorpohous Si matrix. It is shown that the Si/Ag nanocomposite electrode shows much better structural stability than the Si only sample. It is also shown that the Si/Ag nanocomposite electrode shows superior capacity retention compared to the Si only electrode. The results indicate that the presence of the Ag nano-dots is important minimizing the formation of cracks in the electrode, so leading to the better life-time for thin-film Li rechargeable batteries.     

Controlled fluorescence resonance energy transfer between ZnO nanoparticles and fluorophores in layer-by-layer assemblies

We controlled the fluorescence resonance energy transfer (FRET) between ZnO nanoparticles and rhodamine B (RB) within multilayered thin films prepared by the layer-by-layer (LbL) assembling method. Positively charged ZnO nanoparticles and RB-labeled poly(allyamine hydrochloride) (RB-PAH) were accurately incorporated into LbL assemblies of polyelectrolytes. The distance between ZnO nanoparticles and RB-PAH was adjusted by varying the number of layers of pure polyelectrolytes, leading to the controlled FRET from ZnO nanoparticles to RB-PAH.     

基于小波有限元的移动荷载识别

小波有限元桥梁模型以区间B样条小波尺度函数为插值函数,构造了小波有限元梁单元,并通过单元转换矩阵建立了小波空间与物理空间各参数之间的关系;代表车载的移动力则投影到小波空间,从而建立基于小波的车桥系统相互作用模型。采用动态规划技术与T ikhonov正则化方法识别移动力,避免了直接处理反问题时的两端振荡与数值计算病态解等问题。仿真算例表明,与传统有限元模型相比,在相同条件下,小波有限元模型以较少的单元,在相似的识别时间内可获得相似的移动力识别精度。