核酸酶基因LoENDONUCLEASE1在东方百合花朵衰老过程中的功能分析

为明确百合(Lilium spp.)花朵衰老发生的分子机制,在东方百合‘西伯利亚’(Lilium oriental hybrid‘Siberia’)花被片中克隆了一个衰老相关基因LoENDONUCLEASE 1(SAG10),利用qRT-PCR进行基因表达分析,并通过农杆菌介导的拟南芥稳定表达系统和百合花被片瞬时表达体系验证LoENDONUCLEASE 1基因功能。结果显示,LoENDONUCLEASE 1基因开放阅读框(ORF)为921 bp,编码306个氨基酸;LoENDONU⁃CLEASE 1在百合花朵和叶片的衰老过程中特异表达,且受到脱落酸和水杨酸的诱导;拟南芥过表达LoENDO⁃NUCLEASE 1株系中叶片叶绿素含量显著低于对照株系,百合花被片中瞬时过表达LoENDONUCLEASE 1基因加速了百合花被片的衰老,且过表达花被片中丙二醛和离子渗透率含量显著高于对照。结果表明,LoEN⁃DONUCLEASE 1具有促进花朵和叶片衰老的功能。

A review of ultra-high temperature heat-resistant energetic materials

Heat-resistant energetic materials refer to a type of energetic materials that possess a high melting point,high stability and operational safety. By studying the structures of these energetic materials has showed that the thermal stability can be enhanced by introducing amino groups to form intra/inter-molecular hydrogen bonds, constructing conjugate systems and designing symmetrical structures. This article aims to review the physical and chemical properties of ultra-high temperature heat-resistant energetic compounds and provide valuable theoretical insights for the preparation of ultra-high temperature heatresistant energetic materials. We also analyze the selected 20 heat-resistant energetic materials with decomposition temperatures higher than 350℃, serving as templates for the synthesis of various highperformance heat-resistant energetic materials.

Microstructures and mechanical properties of Mg-Al-Sm series heat-resistant magnesium alloys

The microstructures and phase compositions of the as-cast and die-cast Mg-6.02Al-1.03 Sm, Mg-6.05Al-0.98Sm-0.56 Bi and Mg-5.95Al-1.01Sm-0.57 Zn alloys were investigated. Meanwhile, the tensile mechanical and flow properties were tested. The results show that the as-cast microstructure of Mg-6.02Al-1.03 Sm alloy is composed of δ-Mg matrix, discontinuous δ-Mg17Al12 phase and small block Al2 Sm phase with high thermal stability. Rod Mg3Bi2 phase precipitates when Bi is added, while the added metal Zn dissolves into δ-Mg matrix and δ-Mg17Al12 phase. The as-cast alloys exhibit the excellent tensile mechanical property. The tensile strength（δb） and elongation（δ） can reach 205-235 MPa and 8.5%-16.0% at ambient temperature, respectively. Meanwhile, they can also exceed 160 MPa and 14.0% at 423 K, respectively. The die-cast microstructures are refined obviously, and meanwhile the broken second phases distribute dispersedly. The die-cast alloys exhibit better tensile mechanical properties with the values of δb and δ of 240-285 MPa and 8.5%-16.5% at ambient temperature, respectively, and excellent flow property with the flow length of 1870-2420 mm. The die-cast tensile fractures at ambient temperature exhibit a typical character of ductile fracture.

Detection of Phaeocystis globosa using sandwich hybridization integrated with nuclease protection assay(NPA-SH)

Phaeocystis globosa Scherffel is one of the common harmful algae species in coastal waters of the southeastern China.In this study,sandwich hybridization integrated with nuclease protection assay(NPA-SH)was used to qualitatively and quantitatively detect P. globosa.Results showed that this method had good applicability and validity in analyzing the samples from laboratory cultures and from fields.The linear regression equation for P.globosa was obtained,and the lowest detection number of cells was 1.8×104 c...

Construction of Electrocatalytic and Heat-Resistant Self-Supporting Electrodes for High-Performance Lithium–Sulfur Batteries

Boosting the utilization efficiency of sulfur electrodes and suppressing the“shuttle effect”of intermediate polysulfides remain the critical challenge for high-performance lithium-sulfur batteries(LSBs).However,most of reported sulfur electrodes are not competent to realize the fast conversion of polysulfides into insoluble lithium sulfides when applied with high sulfur loading,as well as to mitigate the more serious shuttle effect of polysulfides,especially when worked at an elevated temperature.Herein,we reported a unique structural engineering strategy of crafting a unique hierarchical multifunctional electrode architecture constructed by rooting MOF-derived CoS2/carbon nanoleaf arrays(CoS2-CNA)into a nitrogen-rich 3D conductive scaffold(CTNF@CoS2-CNA)for LSBs.An accelerated electrocatalytic effect and improved polysulfide redox kinetics arising from CoS2-CNA were investigated.Besides,the strong capillarity effect and chemisorption of CTNF@CoS2-CNA to polysulfides enable high loading and efficient utilization of sulfur,thus leading to high-performance LIBs performed not only at room temperature but also up to an elevated temperature(55°C).Even with the ultrahigh sulfur loading of 7.19 mg cm?2,the CTNF@CoS2-CNA/S cathode still exhibits high rate capacity at 55°C.

Effect of RE addition on solidification process and high-temperature strength of Al-12%Si-4%Cu-1.6%Mn heat-resistant alloy

The effect of RE addition on solidification process and high-temperature strength of Al-12%Si-4%Cu-1.6%Mn(in wt.%)heat-resistant alloy was investigated by microstructure observation and tensile test.A great number of fine needle-like RE-rich phases are observed in the alloys with RE addition. Solutionizing treatment does not change their morphologies and sizes, indicating that they have good thermal stability. The addition of RE totally alters the solidification process of eutectic CruAl2 phase, from network-like phase in the form of segregation at the final eutectic grain boundaries to discretely blocky phase growing on the hair-filamentous RE-rich needles. In the alloys with Ce addition, blocky CuAl2, particulate Al15Mn3Si2 and needle-like RE-rich needle phases grow together, but they did not occur in the alloy with only La addition. The addition of RE does not considerably improve the strength of the alloy at high temperatures. The formation of RE-rich phases also does not significantly alter the originating and propagating of micro-cracks in the alloy during tensile test.

Detection of Prorocentrum donghaiense using sandwich hybridization integrated with nuclease protection assay

Prorocentrum donghaiense is an important harmful algae bloom （HAB） causing creature in China＇s seas, and the conventional visual detection can not cope with long-term monitoring and highthroughput sampling projects. An assay for P. donghaiense with sandwich hybridization integrated with nuclease protection assay （NPA-SH） was established. Tests with mixed samples and spiked field ones confirmed its good specificity and sensitivity. The cell number of P. donghaiense correlated well with the optical density, and the regression equation is y=4× 10^- 6x＋ 0.694 9, in which x is the cell number, and y is the optical density, with r2=0.953 5. These results show that the NPA-SH method has good feasibility in the detection of P. donghaiense. Results of NPA-SH and microscopy are excellent for each sample. The NPA-SH method was a simple way in quantitative detection of P. donghaiense, and the whole process could be finished in about six hours, which provided a new approach in high-throughput sampling and long-term monitoring of P. donghaiense.

Preparation of human decellularized peripheral nerve allograft using amphoteric detergent and nuclease

Animal studies have shown that amphoteric detergent and nuclease(DNase I and ribonuclease A) is the most reliable decellularization method of the peripheral nerve. However, the optimal combination of chemical reagents for decellularization of human nerve allograft needs further investigation. To find the optimal protocol to remove the immunogenic cellular components of the nerve tissue and preserve the basal lamina and extracellular matrix and whether the optimal protocol can be applied to larger-diameter human peripheral nerves, in this study, we decellularized the median and sural nerves from the cadavers with two different methods: nonionic and anionic detergents(Triton X-100 and sodium deoxycholate) and amphoteric detergent and nuclease(3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate(CHAPS), deoxyribonuclease I, and ribonuclease A). All cellular components were successfully removed from the median and sural nerves by amphoteric detergent and nuclease. Not all cellular components were removed from the median nerve by nonionic and anionic detergent. Both median and sural nerves treated with amphoteric detergent and nuclease maintained a completely intact extracellular matrix. Treatment with nonionic and anionic detergent decreased collagen content in both median and sural nerves, while the amphoteric detergent and nuclease treatment did not reduce collagen content. In addition, a contact cytotoxicity assay revealed that the nerves decellularized by amphoteric detergent and nuclease was biocompatible. Strength failure testing demonstrated that the biomechanical properties of nerves decellularized with amphoteric detergent and nuclease were comparable to those of fresh controls. Decellularization with amphoteric detergent and nuclease better remove cellular components and better preserve extracellular matrix than decellularization with nonionic and anionic detergents, even in large-diameter human peripheral nerves. In Korea, cadaveric studies are not yet legally subject to Institutional Review Board review.

Achieving a high-strength dissimilar joint of T91 heat-resistant steel to 316L stainless steel via friction stir welding

The reliable welding of T91 heat-resistant steel to 316L stainless steel is a considerable issue for ensuring the safety in service of ultrasupercritical power generation unit and nuclear fusion reactor,but the high-quality dissimilar joint of these two steels was difficult to be obtained by traditional fusion welding methods.Here we improved the structure-property synergy in a dissimilar joint of T91 steel to 316L steel via friction stir welding.A defect-free joint with a large bonding interface was produced using a small-sized tool under a relatively high welding speed.The bonding interface was involved in a mixing zone with both mechanical mixing and metallurgical bonding.No obvious material softening was detected in the joint except a negligible hardness decline of only HV~10 in the heat-affected zone of the T91 steel side due to the formation of ferrite phase.The welded joint exhibited an excellent ultimate tensile strength as high as that of the 316L parent metal and a greatly enhanced yield strength on account of the dependable bonding and material renovation in the weld zone.This work recommends a promising technique for producing high-strength weldments of dissimilar nuclear steels.

Influence of Creep Strength of Weld on Interfacial Creep Damage of Dissimilar Welded Joint between Martensitic and Bainitic Heat-Resistant Steel

The mechanical properties, creep rupture strength, creep damage and failure characteristics of dissimilar metal welded joint （DMWJ） between martensitic （SA213T91） and bainitic heat-resistant steel （12Cr2MoWVTiB（G102）） have been investigated by means of pulsed argon arc welding, high temperature accelerated simulation, mechanical and creep rupture test, and scanning electronic microscope （SEM）. The results show that there is a marked drop of mechanical properties of undermatching joint, and low ductility cracking along weld/G102 interface is induced due to creep damage. Creep rupture strength of overmatching joint is the least. The mechanical properties of medium matching joint are superior to those of overmatching and undermatching joint, and creep damage and failure tendency along the interface of weld/G102 are lower than those of overmatching and undermatching joint after accelerated simulation for 500 h, 1 000 h, 1 500 h, and the creep rupture strength of medium matching joint is the same as that of undermatching joint. Therefore, it is reasonable that the medium matching material is used for dissimilar welded joint between martensitic and bainitic steel.

Dissolution Behavior of Delta Ferrites in Martensitic Heat-resistant Steel for Ultra Supercritical Units Blades

The dissolution behavior of delta ferrites in martensitic heat-resistant steel was studied.And the reason why the dissolution rate of delta ferrites decreased with dissolution time was discussed.The experimental results show that the chemical compositions of delta ferrites negligibly change with dissolution time.The decrease of dissolution rate of delta ferrites with dissolution time should be attributed to the change of shape and distribution of delta ferrites.The shape of delta ferrites tends to transfer from polygon to sphere with dissolution time,causing the decrease of specific surface area of delta ferrites.The distribution position of delta ferrites tends to transfer from boundaries of austenite grains to interior of austenite grains with dissolution time,decreasing the diffusion coefficient of alloy atoms.Both them decrease the dissolution rate of delta ferrites.

Genome engineering and disease modeling via programmable nucleases for insulin gene therapy;promises of CRISPR/Cas9 technology

Targeted genome editing is a continually evolving technology employing programmable nucleases to specifically change,insert,or remove a genomic sequence of interest.These advanced molecular tools include meganucleases,zinc finger nucleases,transcription activator-like effector nucleases and RNA-guided engineered nucleases(RGENs),which create double-strand breaks at specific target sites in the genome,and repair DNA either by homologous recombination in the presence of donor DNA or via the error-prone non-homologous end-joining mechanism.A recently discovered group of RGENs known as CRISPR/Cas9 gene-editing systems allowed precise genome manipulation revealing a causal association between disease genotype and phenotype,without the need for the reengineering of the specific enzyme when targeting different sequences.CRISPR/Cas9 has been successfully employed as an ex vivo gene-editing tool in embryonic stem cells and patient-derived stem cells to understand pancreatic beta-cell development and function.RNA-guided nucleases also open the way for the generation of novel animal models for diabetes and allow testing the efficiency of various therapeutic approaches in diabetes,as summarized and exemplified in this manuscript.

High-temperature oxidation behavior of 9Cr‒5Si‒3Al ferritic heat-resistant steel

To improve the oxidation properties of ferritic heat-resistant steels,an Al-bearing 9Cr‒5Si‒3Al ferritic heat-resistant steel was designed.We then conducted cyclic oxidation tests to investigate the high-temperature oxidation behavior of 9Cr‒5Si and 9Cr‒5Si‒3Al ferritic heat-resistant steels at 900 and 1000℃.The characteristics of the oxide layer were analyzed by X-ray diffraction,scanning electron microscopy,and energy dispersive spectroscopy.The results show that the oxidation kinetics curves of the two tested steels follow the parabolic law,with the parabolic rate constant kp of 9Cr‒5Si‒3Al steel being much lower than that of 9Cr‒5Si steel at both 900 and 1000℃.The oxide film on the surface of the 9Cr‒5Si alloy exhibits Cr2MnO4 and Cr2O3 phases in the outer layer after oxidation at 900 and 1000℃.However,at oxidation temperatures of 900 and 1000℃,the oxide film of the 9Cr‒5Si‒3Al alloy consists only of Al2O3 and its oxide layer is thinner than that of the 9Cr‒5Si alloy.These results indicate that the addition of Al to the 9Cr‒5Si steel can improve its high-temperature oxidation resistance,which can be attributed to the formation of a continuous and compact Al2O3 film on the surface of the steel.

Microstructure and mechanical properties of a cast heat-resistant rare-earth magnesium alloy

Microstructure,mechanical properties and phase transformation of a heat-resistant rare-earth(RE)Mg-16.1Gd-3.5Nd-0.38Zn-0.26Zr-0.15Y(wt.%)alloy were investigated.The as-cast alloy is composed of equiaxedα-Mg matrix,net-shaped Mg5RE and Zr-rich phases.According to aging hardening curves and tensile properties variation,the optimized condition of solution treatment at 520℃for 8 h and subsequent aging at 204℃for 12 h was selected.The continuous secondary Mg5RE phase predominantly formed at grain boundaries during solidification transforms to residual discontinuousβ-Mg5RE phase and fine cuboid REH2particles after heat treatment.The annealed alloy exhibits good comprehensive tensile property at 350℃,with ultimate tensile strength of 153 MPa and elongation to fracture of 6.9%.Segregation of RE elements and eventually RE-rich precipitation at grain boundaries are responsible for the high strength at elevated temperature.

Microstructure and Corrosion Resistance of CrN and CrN/TiN Coated Heat-Resistant Steels in Molten Aluminum Alloy

The components of the equipment for processing the Al melts into the molded parts can be markedly corroded by the molten Al. In this study, a 4 μm CrN coating or CrN/TiN multilayer coating for providing the physical and chemical barriers between the molten reactive Al and the steel substrate were deposited by Cathodic Arc Evaporation onto 10 mm-thick heat-resistant steel plates. The dipping tests were conducted in a 700℃ A356 melt for 1 to 21 h at intervals of 3 h. The damage of the coated steel was eva...

E2EM’s prediction of LaB_(6) as nucleation substrate for primary Mn-rich phase in Al-Si-Cu-Mn heat-resistant alloy and its refining effect

Edge-to-edge matching(E2EM)model was used to predict the potency of LaB_(6) as the heterogeneous nucleation substrate for primary Al_(13)Mn_(4)Si_(8) phase formed during the solidification of Al−Si−Cu−Mn heat-resistant alloy.There are five pairs of orientation relationships(ORs)between LaB_(6) and Al_(13)Mn_(4)Si_(8) phases which meet the criteria of E2EM model.One pair of plane ORs((110)LaB_(6)//(110)Al_(13)Mn_(4)Si_(8))are demonstrated by TEM observation.This strongly indicates that the LaB_(6) phase can act as the heterogeneous nucleation substrate for the primary Al_(13)Mn_(4)Si_(8) phase.1.0 wt.%of Al−2La−1B master alloy was also added into Al−12Si−4Cu−2Mn alloy to evaluate the refining effect by microstructure observation and tensile test.Experimental results show that addition of Al−2La−1B master alloy can significantly refine the primary Al_(13)Mn_(4)Si_(8) phase,supporting the prediction accuracy of E2EM model.However,such refinement of primary Al_(13)Mn_(4)Si_(8) phase does not lead to an improvement in strength.This is due to the larger difference in elastic modulus between the finally formed Al_(13)Mn_(4)Si_(8) phase and aluminum matrix than that of Al_(15)Mn_(3)Si_(2) phase.

Ultrafast solvation dynamics at internal sites of staphylococcal nuclease investigated by site-directed mutagenesis

Internal solvation of protein was studied by site-directed mutagenesis, with which an intrinsically fluorescent probe,tryptophan, is inserted into the desired position inside a protein molecule for ultrafast spectroscopic study. Here we review this unique method for protein dynamics research. We first introduce the frontiers of protein solvation, site-directed mutagenesis, protein stability and characteristics, and the spectroscopic methods. Then we present time-resolved spectroscopic dynamics of solvation dynamics inside cavities of active sites. The studies are carried out on a globular protein, staphylococcal nuclease. The solvation at sites inside the protein molecule＇s cavities clearly reveals characteristics of the local environment. These solvation behaviors are directly correlated to enzyme activity.

The Distribution and Substrate Specificity of Extracellular Nuclease Activity in Marine Fungi

The distribution and specificity of extracellular nucleases produced by marine fungi belonging to eleven genera, namely: Alternaria, Aspergillus, Aureobasidium, Chaetomium, Fusarium, Gliomastix, Humicola, Penicillium, Scopulariopsis, Wardomyces, Periconia, have implied its important function in the organic phosphorus and nitrogen circle in the Ocean. The fungal nucleases of 64 isolates tested were more or less specific for single-stranded DNA with a high preferential specificity towards poly-U substrate with forming of 5’-phosphate mononucleotides. A couple of the nucleases were capable of RNA digesting. The highest level of extracellular nucleolytic ability was observed in Penicillium spp. isolates. The tight correlation found between extracellular nuclease activity and the rate of thymidine uptake by actively growing and sporulating marine fungus Penicillium melinii suggests that this nuclease is required for fulfilling the nucleotide pool of precursors of DNA biosynthesis during transformation of hyphae into the aerial mycelium and conidia in stressful environmental conditions.

HEAT-RESISTANT COMPOSITES CURED BY ELECTRON BEAM

Electron beam (EB) curing of composites has many advantages. Heat-resistant EB-curing composites could substitute polyimide composites used in aeronautical engines. In this paper, the effects of catalyst and dose on the cured resin were investigated. The heat-resistance of the resin cured by EB was evaluated by dynamic mechanical analysis (DMA). The experimental results show that the mechanical properties of the composites cured by EB could meet the specifications of aeronautical engines at 250 degreesC.

The skeleton of 5,7-fused bicyclic imidazole-diazepine for heat-resistant energetic materials

In light of the low yields and complex reaction routes of some well-known 5,5-fused and 5,6-fused bicyclic compounds,a series of 5,7-fused bicyclic imidazole-diazepine compounds were developed with high yields by only two efficient steps.Significantly,the seven-membered heterocyclic ring has a stable energetic skeleton with multiple modifiable sites.However,the 5,7-fused bicyclic energetic compounds were rarely reported in the area of energetic materials.Three neutral compounds 1,2 and 4 were synthesized in this work.To improve the detonation performances of the 5,7-fused neutral compounds,corresponding perchlorate 1a and 2a were further developed.The physicochemical and energetic performances of all newly developed compounds were experimentally determined.All newly prepared energetic compounds exhibit high decomposition temperatures(Td:243.8-336℃)and low mechanical sensitivities(IS:>15 J,FS:>280 N).Among them,the velocities performances of 1a(Dv=7651 m/s)and 4(Dv=7600 m/s)are comparable to that of typical heat-resistant energetic material HNS(Dv=7612 m/s).Meanwhile,the high decomposition temperature and low mechanical sensitivities(Td=336℃;IS=32 J;FS>353 N)of 4 are superior to that of HNS(Td=318℃;IS=5 J;FS=250 N).Hence,the 5,7-fused bicyclic compounds with high thermostability,low sensitivities and adjustable detonation performance have a clear tendency to open up a new space for the development of heat-resistant energetic materials.