Paraffin section observation of flower bud differentiation of Chimonanthus praecox in Kunming and comparison of the differentiation processes in different regions,China

Chimonanthus praecox is an important ornamental plant and cut flower material in China.It blooms in the freezing winter and its flower emits charming fragrance.However,in different region the flowering time is variable.In order to understand the flowering mechanism of Ch.praecox in the winter,we studied the flower bud differentiation in Spring City-Kunming using paraffin sectioning method in the present study.Meanwhile we compared the differentiation process difference from different regions.It was found that the temperature is the key factor for its flower bud differentiation and blossom of Ch.praecox.In the process of bud differentiation,the temperature 20℃was the optimum for inducing changes from vegetative axillary buds to reproductive buds and subsequent morphological differentiation in Ch.praecox.Furthermore in the first three differentiation periods—tepal primordial stage,staminal primordial stage and pistil primordial stage,Kunming took the shortest time to finish the process due to very rapid temperature rise to 20℃,whereas,in Zhengzhou the time for these differentiations was the longest,which may be caused by the slow temperature rise.After May,the high temperature stress forced the flower buds into the first long dormant period in all regions except Kunming.In Kunming,the average temperature was only 20–25℃,so the flower bud continued to differentiate.In all regions,Kunming is the first to complete whole flower bud differentiation even on the early August,and started the second dormancy very early but very long.In the other regions,the plants went through a shorter dormancy and the low temperature broke the dormancy rapidly.Contrarily the plants of Kunming spent a longer period for the low temperature.Thus,the low temperature less than 10℃is a key factor to breaking the second dormancy.Surely the regular effects of temperature on flower bud differentiation and blossom is very helpful for florescence regulation of Ch.praecox.

Modeling of hydrogen diffusion process at a blunt notch in zirconium

The two-dimensional diffusion of interstitial hydrogen atoms in zirconium in a non-uniform stress field was simulated using the phase-field method. The interaction between hydrogen interstitials and the stress field was described by Khachaturyan＇s elastic theory. The Cahn-Hilliard diffusion equation was then solved by an explicit finite difference method. The result shows that hydrogen atoms diffuse to the high-tensile hydrostatic region near the tip of the notch. The content of hydrogen near the tip of the notch increases by 13%, while the stress distribution caused by hydrogen interstitials around the notch is modified by only 0.7%.

La_(0.67)Sr_(0.33)MnO_(3)薄膜相图的轨道弹性调控

过渡金属氧化物具有丰富的功能性,但其错综复杂的内部自由度对相图绘制和结构设计提出了挑战.本文中,我们引入了描述相图物理起源的轨道能级序(ELO),并通过对La_(0.67)Sr_(0.33)MnO_(3)(LSMO)氧化物的研究证明了其在相图预测中的有效性.结合DFT计算和实验,我们构建了氧含量和应变关联的LSMO相图,结果表明LSMO结构稳定性与ELO密切相关.据此发现了一种由ELO演化而产生的四倍氧有序相.最后,我们提出了描述轨道分裂程度的轨道弹性定律,阐明了ELO演化的起源,助力功能氧化物的设计.这项研究拓宽了材料科学领域的性能调控手段,并为从轨道角度预测相图提供了思路.

Tungsten-potassium:a promising plasma-facing material

Tungsten-potassium(potassium-doped tungsten or WK),initially known from the electric filament industry,is a promising plasma-facing material(PFM)in future fusion facilities like International Thermonuclear Experimental Reactor(ITER).However,the brittle nature of W and irradiation-induced defects of WK materials may result in a risk of deuterium-tritium reaction failure in fusion reactors.Previous studies revealed that advanced W with ultrafine grains and nanostructures might be able to address these problems.However,K-doped W,a rapidly developed material for PFMs,lacks a systematical sum-mary.In this review,we firstly describe the powder metallurgy and plastic deformation for the preparation of WK.Then,the mechanical properties of WK and thermal shock resistance results are reviewed.Important issues such as irradiation damages from neutron,heavy ion,and plasma(H isotope or He)irradiation are also discussed.Hitherto,WK under irradia-tions shows comparable or even better performances compared with other counterparts such as ITER grade pure tungsten.This review could be benefitial to the future efforts of improving the ductility and irradiation tolerance of WK materials.

Optimized thyroid transcription factor-1 core promoter-driven microRNA-7 expression effectively inhibits the growth of human non-small-cell lung cancer cells

Targeted gene therapy has become a promising approach for lung cancer treatment.In our previous work,we reported that the targeted expression of microRNA-7(miR-7)operated by thyroid transcription factor-1(TTF-1)promoter inhibited the growth of human lung cancer cells in vitro and in vivo;however,the intervention efficiency needed to be further improved.In this study,we identified the core promoter of TTF-1(from-1299 bp to-871 bp)by 5’deletion assay and screened out the putative transcription factors nuclear factor-1(NF-1)and activator protein-1(AP-1).Further analysis revealed that the expression level of NF-1,but not AP-1,was positively connected with the activation of TTF-1 core promoter in human non-small-cell lung cancer(NSCLC)cells.Moreover,the silencing of NF-1 could reduce the expression level of miR-7 operated by TTF-1 core promoter.Of note,we optimized four distinct sequences to form additional NF-1-binding sites(TGGCA)in the sequence of TTF-1 core promoter(termed asTTF-1 promoter),and verified the binding efficiency of NF-1 on theTTF-1 promoter by electrophoretic mobility shift assay(EMSA).As expected,theTTF-1 promoter could more effectively drive miR-7 expression and inhibit the growth of human NSCLC cells in vitro,accompanied by a reduced transduction of NADH dehydrogenase(ubiquinone)1αsubcomplex 4(NDUFA4)/protein kinase B(Akt)pathway.Consistently,TTF-1 promoter-driven miR-7expression could also effectively abrogate the growth and metastasis of tumor cells in a murine xenograft model of human NSCLC.Finally,no significant changes were detected in the biological indicators or the histology of some important tissues and organs,including heart,liver,and spleen.On the whole,our study revealed that the optimized TTF-1 promoter could more effectively operate miR-7 to influence the growth of human NSCLC cells,providing a new basis for the development of microRNA-based targeting gene therapy against clinical lung cancer.