Preparation of PET using homogeneous catalysts. II. Effect of BHPP, NPG and PD in Sb2O3 glycol solution catalysts

In the polycondensation reaction of polyethyleneterephthalate(PET), Sb₂O₃ can react effectively as a catalyst, if physically transformed. Sb₂O₃ powder is transformed into liquid solution by dissolving in ethylene glycol(EG). Homogeneous catalyst is made by mixing this liquid solution with glycols having different solubility. The efficient reaction of PET polymerization is expected by using homogeneous catalyst. PET was synthesized using homogeneous catalysts of 4 wt.% Sb₂O₃ solution dissolved in glycol[EG, 2,2-bis(4-(2-hydroxyethoxy)phenol)propane(BHPP), neopentyl glycol(NPG), and 1,3-propandiol(PD)]. PET using EG-BHPP(Sb₂O₃) catalysts shows the highest I.V. within a reaction time of 120 min. In the p-d analysis, PET using EG-BHPP(Sb₂O₃) catalysts has the fastest propagation rate and slowest degradation rate. EG-BHPP(Sb₂O₃) catalysts are more efficient than EG(Sb₂O₃) catalysts and Sb₂O₃ powder catalysts.     

Effect of silicate fertilizer on reducing methane emission during rice cultivation

Slag-type silicate fertilizer, which contains high amount of active iron oxide, a potential source of electron acceptor, was applied at the rate of 0, 2, 6, 10, and 20 Mg ha⁻¹ to reduce methane (CH₄) emission from rice planted in potted soils. Methane emission rates measured by closed chamber method decreased significantly with increasing levels of silicate fertilizer application during rice cultivation. Soil redox potential (Eh) decreased rapidly after flooding, but floodwater pH and soil pH increased significantly with increasing levels of silicate fertilizer application. Iron concentrations in potted soils and in percolated water significantly increased with the increasing levels of silicate fertilizer application, which acted as oxidizing agents and electron acceptors, and thereby suppressed CH₄ emissions. Silicate fertilization significantly decreased CH₄ production activity, while it increased carbon dioxide (CO₂) production activity. Rice plant growth, yield parameters, and grain yield were positively influenced by silicate application levels. The maximum increase in grain yield (17% yield increase over the control) was found with 10 Mg ha⁻¹ silicate application along with 28% reduction in total CH₄ flux during rice cultivation. It is, therefore, concluded that slag-type silicate fertilizer could be a suitable soil amendment for reducing CH₄ emissions as well as sustaining rice productivity and restoring the soil nutrient balance in rice paddy soil.     

Laboratory Investigation of the Geochemical Behavior of Metals in Paddy Soils Contaminated with Mine Tailings

The geochemical behavior of metals, including Fe, Mn, Pb and Zn, in contaminated paddy soils was investigated during the cultivation of rice crops through laboratory microcosm experiments. From the two paddy fields contaminated by mine tailings, Siheung and Deokeum in Korea, paddy soils were collected and analyzed for their geochemical characteristics. The Siheung paddy soil showed higher levels of heavy metals, whereas the higher potential for the release of metals was anticipated due to the extremely acidic conditions at Deokeum. In microcosm experiments of flooded paddy soils over 18 weeks, Fe and Mn were released in subsurface pore waters by reductive dissolution, and Pb and Zn were dissolved in high amounts at the surface by oxidation of sulfides. Although amorphous Fe oxide-rich layers were formed at the surface of both paddy soils, the release of Pb and Zn were controlled at the surface by these layers only under slightly alkaline conditions at Siheung. Lead and Zn were associated with the reducible and carbonate fractions at the surface paddy soil of Siheung from the sequential extraction on core samples collected during the flooded period. In the acidic conditions at Deokeum, Pb and Zn were continuously released until the late stage of flooding. A great increase in the exchangeable fraction of metals was observed after the soils had drained. The bioavailability of metals for rice crops would be high under acidic conditions at Deokeum, despite the lower levels of heavy metal contamination.     

Flavor compounds and quality parameters of chevon as influenced by sericea lespedeza hay

This research assessed the utilization of sericea lespedeza (SL, Lespedeza cuneata ) hay, a highly condensed tannin (CT) forage (87-181 g CT/kg), as a dietary regimen of meat goats, and thereby the effects on physicochemical properties of goat meat (chevon) and flavor compounds in cooked chevon chops were evaluated. Although it is commonly believed that higher amounts of CT can have deleterious effects on animal performance due to low digestibility and low voluntary intakes in ruminants, feeding meat goats with SL hay increased the body weight compared to goats fed bermudagrass hay without altering the chemical composition and meat quality of chevon. Feeding SL hay to meat goats also did not significantly influence the flavor volatiles in cooked chevon chops. The findings indicate that SL hay can be used as a low-input forage to replace expensive forages.     

Physicochemical, antimicrobial, and cytotoxic characteristics of a chitosan film cross-linked by a naturally occurring cross-linking agent, aglycone geniposidic acid

The purpose of this study was to evaluate the characteristics of a chitosan film cross-linked by a naturally occurring compound, aglycone geniposidic acid (aGSA). This newly developed aGSA-cross-linked chitosan film may be used as an edible film. The chitosan film without cross-linking (fresh) and the glutaraldehyde-cross-linked chitosan film were used as controls. The characteristics of test chitosan films evaluated were their degree of cross-linking, swelling ratio, mechanical properties, water vapor permeability, antimicrobial capability, cytotoxicity, and enzymatic degradability. It was found that cross-linking of chitosan films by aGSA (at a concentration up to 0.8 mM) significantly increased its ultimate tensile strength but reduced its strain at fracture and swelling ratio. There was no significant difference in the antimicrobial capability between the cross-linked chitosan films and their fresh counterpart. However, the aGSA-cross-linked chitosan film had a lower cytotoxicity, a slower degradation rate, and a relatively lower water vapor permeability as compared to the glutaraldehyde-cross-linked film. These results suggested that the aGSA-cross-linked chitosan film may be a promising material as an edible film.     

Principal component analysis and discriminant analysis (PCA-DA) for discriminating profiles of terminal restriction fragment length polymorphism (T-RFLP) in soil bacterial communities

To assess the impact of a transgenic crop on soil environment, we compared soil bacterial communities from the rhizospheres of cucumber green mottle mosaic virus (CGMMV)-resistant transgenic watermelon (Citrullus vulgaris [Twinser] cv. Gongdae) and non-transgenic parental line watermelon at an experimental farm in Miryang, Korea. Soil microbial community structure was studied using terminal restriction fragment length polymorphism (T-RFLP) using HaeIII and HhaI enzymes on products from polymerase chain amplification reactions (PCR) of total DNA from rhizosphere. We used principal component analyses (PCA) to reduce dimensionality of T-RFLP profiles before comparison. On these PCA scores, we conducted discrimination analyses to compare soil microbial communities from the rhizosphere of transgenic and non-transgenic. Discriminant analyses indicate that microbial communities from rhizosphere of transgenic and non-transgenic watermelon did not differ with significance at 95% level. Our study could be used as a model case to assess the environmental risk assessment of transgenic crops on soil microbial organisms.     

Biologically inspired artificial compound eyes

This work presents the fabrication of biologically inspired artificial compound eyes. The artificial ommatidium, like that of an insect's compound eyes, consists of a refractive polymer microlens, a light-guiding polymer cone, and a self-aligned waveguide to collect light with a small angular acceptance. The ommatidia are omnidirectionally arranged along a hemispherical polymer dome such that they provide a wide field of view similar to that of a natural compound eye. The spherical configuration of the microlenses is accomplished by reconfigurable microtemplating, that is, polymer replication using the deformed elastomer membrane with microlens patterns. The formation of polymer waveguides self-aligned with microlenses is also realized by a self-writing process in a photosensitive polymer resin. The angular acceptance is directly measured by three-dimensional optical sectioning with a confocal microscope, and the detailed optical characteristics are studied in comparison with a natural compound eye.     

Accuracy evaluation of the crop-weather yield predictive models of Italian ryegrass and forage rye using cross-validation

The objective of this study was to evaluate the accuracy of the yield predictive models of Italian ryegrass (IRG, Lolium multiflorum Lam.) and forage rye (FR, Secale cereale L.) reported in previous studies through K-fold cross-validation method. In previous studies, statistical models were constructed for dry matter yield prediction of IRG and FR using general linear model based on climatic data by locations in the Republic of Korea. The yield predictive model for IRG cultivated in the southern region of the Korean Peninsula and Jeju Island were DMY = 78.178AGD–254.622MTJ + 64.156SGD–76.954PAT150 + 4.711SAP + 1028.295 + Location and DMY =–8.044AAT + 18.640SDS–7.542SAT + 9.610SAP + 17282.191, respectively. The yield predictive model for FR was as follows: DMY = 20.999AGD + 163.705LTJ + 113.716SGD + 64.379PAT100–4964.728 + Location. However, accuracy evaluation was not performed in the previous research. In this study, the reported models and the data set used for model construction were investigated. Subsequently, K-fold cross-validation was performed to assess the accuracy of the models. The results showed that the yield predictive models fit to the data sets well, while the accuracy of these models was in the common level since the data sources might keep major variances in cultivars, climatic conditions, and cultivated locations. Therefore, models with better fitness and accuracy might be constructed based on a data set with smaller variance. Hence, the standardization of the crop cultivation experiments is very necessary to decrease the variance in the historical data used for future crop yield modeling.     

The complete chloroplast genome sequence of <Emphasis Type="Italic">Glycyrrhiza lepidota</Emphasis> (Nutt.) Pursh - An American wild licorice

The wild species are considered as primary and secondary genepools for the world’s most important food crops. Here, we sequenced the complete chloroplast (cp) genome sequence of an American wild licorice, Glycyrrhiza lepidota for the first time to investigate their phylogenetic relationship among inverted-repeat-lacking clade (IRLC) legumes. The total length of the chloroplast genome is 127,939 bp, with 34.2% overall GC content. The chloroplast genome harbors 110 known genes, including 76 protein-coding genes, four ribosomal RNA genes, and 30 tRNA genes. Similar to other closely related plastomes, rpl22 and rps16 are absent. A total of 464 cp microsatellites (cpSSRs) were analyzed in the G. lepidota. The majority of the SSRs in this cp genome are penta-nucleotides (61.6%). Locally collinear blocks (LCBs) identified between the Glycyrrhiza glabra and G. lepidota cp genomes were showed that they were well conserved with respect to gene organization and order. Moreover, the phylogenetic analysis indicates that G. lepidota is closely related to its confamilial counterparts than to the other taxa of the IRLC legumes.