Physiological Differences Between Yellow-Seeded and Black-Seeded Rapeseeds (Brassica napus L.) with Different Testa Characteristics During Artificial Ageing

Yellow-seeded rapeseed (Brassica napus L.) is a new kind of breeding resources with yellow color, increased oil and protein content and less unwanted crude fiber content due to the thinner and transparent testa compared with traditional black or brown-seeded rapeseed. To analyze the longevity of the yellow-seeded rapeseed during storage, the physiological differences between the yellow and black-seeded near-isogenic lines were studied by artificial ageing method. The testa rate, anthocyanin content and melanin content of yellow-seeded rapeseeds decreased by 20.1, 25.2, and 80.4% respectively than black-seeded rapeseed. During artificial ageing, the yellow-seeded rapeseed showed significantly different effect of ageing compared with the black-seeded, as demonstrated by faster deterioration with lower germination percentage, seed vigour index, reducing sugar and soluble protein contents than the black-seeded, as well as a drastic increase in electrical conductivity, malnodialdehyde (MDA) content and a rapid decrease in activities of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). The results suggested that the transparent testa of the yellow-seeded rapeseed lost some abilities to protect the embryo against adverse environmental conditions and thus led to a poor storability.

Effects of Artificial Aging on Physiological Characteristics and Seed Vigor of Medicago ruthenica Seeds

As shown by the changes in physiological characteristics and seed vigor of three Medicago ruthenica samples during artificial aging process, the germination potential, germination rate, germination index, vigor index and simple vigor index declined with the extension of aging time on the whole. After artificial aging for 6 min, the vigor was higher than that of the control. The conductivity, malondialdehyde content and soluble polysaccharide content of seed leachate increased with the aging time and negatively correlated （ P 〈 0.05） with the seed vigor indicators. The physiological indicators were very significantly correlated （P 〈 0.01 ） with the vigor indicators in the Medicago ruthenica sample from Dorbod Qi, UIanqab City（China）.

A new experimental way for the monitoring of the real/equivalent inservice- time of double base rocket propellant by coupling VST and PCA

The assessment of the real in-service-time(RIST)and the equivalent in-service-time(EIST)of double base rocket propellants(DBRPs)is of utmost importance for the safe storage and use of weapon systems as well as the efficiency of the accelerated aging plans.In this work,four DBRPs with similar chemical composition and different natural aging have been artificially aged at T?338.65 K for 4 months with sampling every 30 days.The unaged and artificially aged samples have been investigated by vacuum stability test(VST)at five isothermal temperatures(T?333.15 K,343.15 K,353.15 K,363.15 K,and 373.15 K).The volume of the evolved gases in VST was found to decrease with natural/artificial aging.Furthermore,the VST data were treated and subjected to principal component analysis(PCA).The results showed excellent discrimination of the DBRP samples according to their stability thermal properties.Most of the variance was described by the first principal component(PC1)whose scores were linearly correlated with the natural aging durations when PCA is applied on VST data obtained at T?363.15 K.In light of the obtained results,a new experimental way for the estimation of the real/equivalent IST was proposed,which takes into account the impact of the natural aging of the sample.The approach predicts successfully the RIST of two similar DBRPs with a relative deviation of less than 2%.At the specific heating temperature T?338.65 K,the developed model provides more conceivable EIST values,with asymptotic behavior against artificial aging duration evolution,thus overcoming some shortcomings of the common generalized van’t Hoff formula(GvH).

Negative Association between Seed Dormancy and Seed Longevity in Bread Wheat

Many organisms have dormant stages with an extension of their life span to increase longevity, and deeper dormancy is usually related to greater longevity. In cereal crops, seed dormancy is significantly associated with pre-harvest sprouting tolerance during seed development, as seed longevity is a valuable trait for seed banks and providing reliable crop seeds to farmers. In this study, we evaluated both seed dormancy and longevity in bread wheat based on germination and artificial aging tests. According to phenotypic clustering analysis, relative germination rate/potential and relative seedling vigor index were more effective to indicate seed longevity than relative electrical conductivity in wheat, while all the four investigated phenotypes of relative germination potential, relative germination rate, germination index and degree of seed dormancy fit well as a reflex of wheat seed dormancy. In the correlation analysis, the germination level of newly harvested grain negatively reflected its degree of seed dormancy, while the germination ability of grain after artificial aging reflected its seed longevity. However, in contrast to the current opinion in plant, seed dormancy was significantly negatively correlated to seed longevity in our study, and it was not an accidental phenomenon, for that the majority of accessions with high degree of seed dormancy had short seed longevity. To our knowledge, this is the first to report the negative association between seed dormancy and longevity in cereal crops. It would lead to further concerns about how to breed wheat with both prolonged seed longevity and deep dormancy to avoid pre-harvest sprouting.

Retrogression characteristics of a novel Al-Cu-Li-X alloy

Retrogression characteristics of a novel Al-Cu-Li-X alloy of 2A97 were studied by hardness testing, transmission electron microscopy （TEM）, and differential scanning calorimetry （DSC）. The retrogression treatments of aging at 155°C for 12 h followed by aging at 220 and 240°C were chosen by determining the peak temperature of δ＇ precipitation at 230°C by DSC. The retrogression treatment at a lower temperature of 220°C causes the precipitation and coarsening of δ＇ and θ＇ phases in the matrix, resulting in an increase in hardness. Retrogression at a higher temperature of 240°C causes the dissolution and coarsening of δ＇ and θ＇ precipitates in the matrix and on the grain boundaries, resulting in a decrease in hardness. Microstructural changes upon retrogression including the appearance of equilibrium precipitates such as T1, T2, δ＇, and θ are confirmed by the selected area electron diffraction and the bright and dark field image analysis.

SUPERPLASTIC DEFORMATION BEHAVIOR OF SUPERHARD Al ALLOY LC4

The superplasticity of high strength superhard A1 alloy LC4 was improved to a great extent by modified thermomechanical treatment.Its maximum elongation may be up to 2100% un- der deformation at initial strain rate of 8.33×10^(-4) S^(-1) at 510℃.Observations of the microstructure changes revealed that with the increase of the deformation,the grain grows and the alloy exhibits strain hardening.The excellent elongation of the alloy seems due to the in- crease of grain stability under deformation.

Accelerated Ageing Tests for Evaluations of a Durability Performance of Glass-fiber Reinforcement Polyester Composites

The paper presented accelerated ageing test results of a durability study on ortho-phthalic anhydride-type unsaturated polyester resin （191#） and its glass-fiber reinforcement polyester composites （GFRPC）. The samples were exposed in an artificial xenon arc lamp ageing cell or a thermo-oxidative ageing cell. Morphology and gloss of the specimens were investigated by using a microscope and a gloss-meter, respectively. The tensile strength, bending strength and inter-laminar shear strength （ILSS） of GFRPC were tested before and after exposure, and were considered to evaluate the durability performance of this material. The polyester resin was analyzed by fourier transform infrared （FT-IR） spectroscopy. The results showed that the glossiness of the specimens got worse and some cracks appeared on their surface during the course of ageing, the tensile strength and bending strengths of the specimens first increased and then decreased. The ILSS of the composites decreased after they were aged in the xenon arc lamp cell, but increased while they were aged in the thermo-oxidative cell. The changes of these trends become more obvious during ageing in the xenon arc lamp cell, so the main influencing factor leading to the failure of this material is UV irradiation.

Influence of heat treatment on microstructure and mechanical properties of Al/Al-Cu graded materials

Five-layered Al/Al-Cu functionally graded material （FGM） was prepared by powder metallurgy technology, and the subsequent heat treatment was carried out for the graded material. The microstructures and distribution of Cu element under pressure sintering （F）, solution treatment （T4） and artificial aging treatment （T6） were investigated, and the Vickers hardness and flexural properties of different states were tested. The results showed that sintered compact with dense structure and compositional continuous change was obtained. The second-phase CuAl 2 was dispersively distributed along grain boundary of Al matrix. After solution treatment at 503 C for 3 h, CuAl 2 phase obviously decreased and dissolved into the Al matrix, and the flexural strength was thereupon enhanced to 228.5 MPa. With the subsequent aging treatment at 150 C for 15 h, the majority of flake shaped precipitates θ phases were uniformly distributed in the matrix. And the distribution of Cu element became gradual continuous compared to sintered compact. Meanwhile, the flexural strength increased further, which accompanied with the decline of plasticity.