In the present study, the characteric-structure relationship of epoxidized soybean oils (ESO) with various degrees of epoxidation
has been investigated. FTIR analysis was used to identify the relative extent of epoxidation of the samples during the epoxidation
reaction. The viscosities of ESO were much higher than that of the raw oil, viscosity increased with degree of epoxidation.
The viscous-flow activation energy of ESO was determined to be higher than that of the raw oil (20.72 to 77.93% higher). Thermogravimetry
analysis (TG) of ESO was used to investigate the thermodynamic behavior of the samples. With increasing degree of epoxidation,
the thermal stability of the samples initially decreased, then increased at the final reacting stage. Differential scanning
calorimeter (DSC) indicated that the melting point of ESO was higher than that of soybean oil. Gel permeation chromatography
(GPC) indicated the molecular mass of the samples increased initially, then decreased, with an increase in the extent of epoxidation.
Authors:B. Lin, L. Yang, H. Dai, Q. Hou, and L. Zhang
Soybean oil based polyols (5-OH polyol, 10-OH polyol and 15-OH polyol) were synthetised from epoxidized soybean oil. The melting
peak of polyols and the relationship between melting peak and the number-average functionality of hydroxyl in polyols were
investigated by differential scanning calorimetry (DSC). The thermal decomposition of polyols and some of their thermal properties
by thermogravimetry (TG) and derivative thermogravimetry (DTG) were also studied. The thermal stability of polyols in a nitrogen
atmosphere was very close hence they had a same baseplate of triglyceride for polyols. The extrapolated onset temperature
of polyols in their thermal mass loss, first step had a decreasing order: 5-OH polyol>10-OH polyol>15-OH polyol due to the
difficulty in forming multiple elements ring of them had the same order.
The thermal behavior of polyols under non-isothermal conditions using Friedman’s differential isoconversional method with
different heating rates indicated that the 5-OH polyol had the lowest activation energy in thermal decomposition amongst these
polyols according to the same fractional mass loss because of the weakest intramolecular oligomerization. The 15-OH polyol
was prior to reach the mass loss region because the six-member ring is more stable than the three-member ring from 10-OH polyol
and more easily formed.
Authors:J. Zhang, L. Ge, X. Zhang, Y. Dai, H. Chen, and L. Mo
The thermal decomposition of Zn[NFA]2
5H2O (NFA=C16H18FN3O3, norfloxacin) and its kinetics were studied under non-isothermal conditions in air by TG-DTG and DTA methods. The intermediate and residue for each decomposition were identified from the TG curve. The non-isothermal kinetic data were analyzed by means of the Achar method and the Madhusudanan-Krishnan-Ninan (MKN) method. The possible reaction mechanisms were investigated by comparing the kinetic parameters. The kinetic equation for the second stage can be expressed as d/dt=Aexp(–E/RT)(1–).
Authors:J. Li, W. Dai, G. Xiao, H. Wang, Z. Zhang, and T. Wu
99Tc is an important radionuclides related to repository safety assessment. The mobility pertechnetate (TcO4−) can be reduced to immobility technetium(IV) hydrous oxides (TcO2·nH2O) by Fe(II)-bearing minerals. In China, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling material
for the HLW repository, which is contained some FeO. The diffusion behavior of 99Tc was investigated in GMZ bentonite by through- and out-diffusion methods. The effective diffusion coefficient (De), the accessible porosity (εacc), apparent diffusion coefficient (Da) and distribution coefficient (Kd) were decreased with the increasing of dry density. The De values were (2.8 ± 0.2) × 10−11 m2/s and (3.5 ± 0.2) × 10−12 m2/s at dry density of 1,600 and 1,800 kg/m3, respectively. It was indicated that the dominating species was TcO4− during the diffusion processing. While, out-diffusion results showed that part of TcO4− may be reduced by Fe(II). The relationship of De and εacc could be described by Archie’s law with exponent n = 2.4 for 99Tc diffusion in GMZ bentonite. Furthermore, the relationship between Da and dry density (ρ) was exponential.
Authors:S.F. Dai, D.Y. Xu, Z.J. Wen, Z.P. Song, H.X. Chen, H.Y Li, J.R. Li, L.Z. Kang, and Z.H. Yan
A novel 4.0-kb Fy was sequenced and bacterially expressed. This gene, the largest y-type HMW-GS currently reported, is 4,032-bp long and encodes a mature protein with 1,321 amino acid (AA) residues. The 4.0-kb Fy shows novel modifications in all domains. In the N-terminal, it contains only 67 AA residues, as three short peptides are absent. In the repetitive domain, the undecapeptide RYYPSVTSPQQ is completely lost and the dodecapeptide GSYYPGQTSPQQ is partially absent. A novel motif unit, PGQQ, is present in addition to the two standard motif units PGQGQQ and GYYPTSPQQ. Besides, an extra cysteine residue also occurs in the middle of this domain. The large molecular mass of the 4.0-kb Fy is mainly due to the presence of an extra-long repetitive domain with 1,279 AA residues. The novel 4.0-kb Fy gene is of interest in HMW-GS gene evolution as well as to wheat quality improvement with regard to its longest repetitive domain length and extra cysteines residues.
Authors:Y. Jean, X. Hong, J. Liu, C. Huang, H. Cao, C. Chung, G. Dai, K. Cheng, and Hsinjin Yang
Positron annihilation lifetime (PAL) experiments are performed in polycarbonate (PC) exposed to CO2 and He gases as a function of time and pressure. In PC/CO2 systems, hole size and fraction reduced from PAL data increase as a function of CO2 pressure and exposure time. Significant hysteresis in positron lifetime data is observed during CO2 abasorption/desorption. In PC/He systems, no variation is observed. Hole size distribution in the CO2-exposed polymers is found to be significantly broader than in unexposed samples. The high sensitivity of PAL results to CO2 exposure of PC is thought to relate to the microstructural changes in the polymer matrix, such as penetrant plasticization, gas hydrostatic pressure effect, and molecular filling and creation of holes.
Authors:Y. Cao, Y. Wang, K. Ji, S. Dai, Q. Li, C. Duan, P. Chen, Y. Wu, Y. Sun, H. Luo, Y. Wang, and P. Leng
Influence of different maturity stages and treatments of ethephon, exogenous ABA, and fluridone on the ripening and hormone level of ‘Zhonghuashoutao’ peach during development and post-harvest storage were investigated. The accumulation of endogenous ABA appeared at the onset of ripening and peaked at two weeks before harvest. Fruit firmness decreased, while ethylene release and SSC/TA increased sharply after a maximum peak of ABA, which have triggered the initiation of the fruit ripening. The fruits, harvested at 170 d when fruits have ripened and stored at 20 °C, showed an ethylene climacteric peak, and the pulp started softening normally, and the SSC/TA value increased. Compared with them, the immature green fruits harvested at other dates, could not mature normally due to the lack of normal reciprocity between ABA and ethylene. The ethylene release was promoted by the treatment of exogenous ABA and ethephon during ripening until the endogenous ABA reached a maximum value. However, fluridone treatment showed an inhibitory effect. The above-mentioned changes occurred again in the peach fruits after harvest. The results indicated that both ABA and ethylene play important roles in peach ripening, and their action depended on the ripening stage of peach.
Authors:S.F. Dai, X.F. Xue, Y.F. Wang, Y.L. Xie, Z.P. Song, D.Y. Xu, Z.J. Wen, and Z.H. Yan
New high-molecular-weight glutenin (HMW glutenin) sequences isolated from six Psathyrostachys juncea accessions by thermal asymmetric interlaced PCR differ from previous sequences from this species. They showed novel modifications in all of the structural domains, with unique C-terminal residues, and their N-terminal lengths were the longest among the HMW glutenins reported to date. In their repetitive domains, there were three repeatable motif units: 13-residue [GYWH(/I/Y)YT(/Q)S(/T)VTSPQQ], hexapeptide (PGQGQQ), and tetrapeptide (ITVS). The 13-residue repeats were restricted to the current sequences, while the tetrapeptides were only shared by D-hordein and the current sequences. However, these sequences were not expressed as normal HMW glutenin proteins because an in-frame stop codon located in the C-termini interrupted the intact open reading frames. A phylogenetic analysis supported different origins of the P. juncea HMW glutenin sequences than that revealed by a previous study. The current sequences showed a close relationship with D-hordein but appeared to be more primitive.