Porous TiFe_(2) intermetallic compound fabricated via elemental powder reactive synthesis

Porous intermetallics show potential in the field of filtration and separation as well as in the field of catalysis.Herein,porous Ti Fe2intermetallics were fabricated by the reactive synthesis of elemental powders.The phase transformation and pore formation of porous TiFe2intermetallics were investigated,and its corrosion behavior and hydrogen evolution reaction(HER)performance in alkali solution were studied.Porous TiFe2intermetallics with porosity in the range of 34.4%-56.4%were synthesized by the diffusion reaction of Ti and Fe elements,and the pore formation of porous TiFe2intermetallic compound is the result of a combination of the bridging effect and the Kirkendall effect.The porous TiFe2samples exhibit better corrosion resistance compared with porous 316L stainless steel,which is related to the formation of uniform nanosheets on the surface that hinder further corrosion,and porous TiFe2electrode shows the overpotential of 220.6 and 295.6 mV at 10 and 100 mA·cm-2,suggesting a good catalytic performance.The synthesized porous Fe-based intermetallic has a controllable pore structure as well as excellent corrosion resistance,showing its potential in the field of filtration and separation.

HEAT TREATMENT BEHAVIOR OF CAN-FORGED TITANIUM ALUMINIDE ALLOY IN (α+γ) REGION

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Grain Refiner for TiAl Intermetallic Compounds

The effect of BN addition on the grain size and rnechanical properties of Ti-34.1 wt-%Al alloy was investigated. It has been found that BN is an effective grain refiner for TiAl base alloys, The addition of a small arnount of BN to TiAl can change the coarse columnar grains of as-cast rnicrostructure into the fine equiaxed grains. It has been also determined that Ti-34.1 wt-%Al-1.0 wt-%BN alloy has better mechanical properties and microstructure

Boosting wheat functional genomics via an indexed EMS mutant library of KN9204

A better understanding of wheat functional genomics can improve targeted breeding for better agronomic traits and environmental adaptation.However,the lack of gene-indexed mutants and the low transformation efficiency of wheat limit in-depth gene functional studies and genetic manipulation for breeding.In this study,we created a library for KN9204,a popular wheat variety in northern China,with a reference genome,transcriptome,and epigenome of different tissues,using ethyl methyl sulfonate(EMS)mutagenesis.This library contains a vast developmental diversity of critical tissues and transition stages.Exome capture sequencing of 2090 mutant lines using KN9204 genome-designed probes revealed that 98.79%of coding genes had mutations,and each line had an average of 1383 EMS-type SNPs.We identified new allelic variations for crucial agronomic trait-related genes such as Rht-D1,Q,TaTB1,and WFZP.We tested 100 lines with severemutations in 80 NAC transcription factors(TFs)under drought and salinity stress and identified 13 lines with altered sensitivity.Further analysis of three lines using transcriptome and chromatin accessibility data revealed hundreds of direct NAC targets with altered transcription patterns under salt or drought stress,including SNAC1,DREB2B,CML16,and ZFP182,factors known to respond to abiotic stress.Thus,we have generated and indexed a KN9204 EMS mutant library that can facilitate functional genomics research and offer resources for genetic manipulation of wheat.

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing

Densification behavior of high Nb containing TiAl alloys through reactive hot pressing was investigated. The results showed that the density of the sample hot pressed at 1400°C could reach a near full density of 98.37%. However, the densification abnormality was observed at 1500°C. The diffusion of elemental Nb during microstructural evolution is an important aspect affecting densification, which will form pore nests. With the increase of hot pressing temperature, the diffusion of Nb becomes more adequate. HIP （Hot isostatic pressing） treatment can only decrease porosity to some extent, but cannot eliminate it completely.

Control of the Transition to Flowering by Chromatin Modifications

The timing of floral transition is critical to reproductive success in angiosperms and is genetically controlled by a network of flowering genes. In Arabidopsis, expression of certain flowering genes is regulated by various chromatin modifications, among which are two central regulators of flowering, namely FLOWERING LOCUS C （FLC） and FLOWERING LOCUS T（FT）. Recent studies have revealed that a number of chromatin-modifying components are involved in activation or repression of FLC expression. Activation of FLC expression is associated with various ＇active＇ chromatln modifications including acetylation of core histone tails, histone H3 lysine-4 （H3K4） methylation, H2B monoubiquitination, H3 lysine-36 （H3K36） di- and tri-methylation and deposition of the histone variant H2A.Z, whereas various ＇repressive＇ histone mod- ifications are associated with FLC repression, including histone deacetylation, H3K4 demethylation, histone H3 lysine-9 （H3K9） and H3 lysine-27 （H3K27） methylation, and histone arginine methylation. In addition, recent studies have revealed that Polycomb group gene-mediated transcriptional-silencing mechanism not only represses FLC expression, but also directly represses FTexpression. Regulation of FLC expression provides a paradigm for control of the expression of other developmental genes in plants through chromatin mechanisms.

Brassinosteroid Signaling Recruits Histone 3 Lysine-27 Demethylation Activity to FLOWERING LOCUS C Chromatin to Inhibit the Floral Transition in Arabidopsis

The steroid hormone brassinosteroid （BR） plays a broad role in plant growth and development. As the retarded growth in BR-insensitive and BR-deficient mutants causes a strong delay in days to flowering, BR signaling has been thought to promote the floral transition inArabidopsis. In this study, using a developmental measure of flowering time, we show that BR signaling inhibits the floral transition and promotes vegetative growth in the Arabidopsis accessions Columbia and Enkheim-2. We found that BR signaling promotes the expression of the potent floral repressor FLOWERING LOCUS C （FLC） and three FLC homologs to inhibit flow- ering. In the presence of BR, the transcription factor BRASSINAZOLE-RESISTANT1 （BZR1）, together with BES1 -INTERACTING MYC-like proteins （BIMs）, specifically binds a BR- responsive element in the first intron of FLC and further recruits a histone 3 lysine 27 （H3K27） demethylase to downregulate levels of the repressive H3K27 trimethylation mark and thus antagonize Polycomb silencing at FLC, leading to its activation. Taken together, our findings demonstrate that BR signaling inhibits the floral transition inArabidopsis by a novel molecular mechanism in which BR signals are transduced into FLC activation and consequent floral repression.

Recent progress in porous intermetallics:Synthesis mechanism,pore structure,and material properties

Intermetallic compounds have the characteristics of long-range ordered structure and combination of metallic and covalent bonds,showing intrinsic brittleness and outstanding performance stability.The synthesis mechanism,pore structure characterization and material properties of powder metallurgy porous intermetallics are reviewed in this paper.Compared with traditional porous materials,porous intermetallics have good thermal impact resistance,machinability,thermal and electrical conductivity similar to metals,as well as good chemical corrosion resistance,rigidity and high-temperature property similar to ceramics.The mechanisms of preparation and pore formation of porous intermetallics mainly include four aspects:(1)the physical process based on the interstitial space between the initial particles and its evolution in the subsequent procedures;(2)the chemical combustion process based on the violent reaction between the initial powder components;(3)the reaction kinetics process based on the difference between the diffusion rates of elements;(4)the phase transition process based on the difference between the phase densities.The characterization parameters to the pore structure description for porous intermetallics include mainly overall porosity,open porosity,permeability,maximum pore size,pore size distribution and tortuosity factor.In terms of microstructure characterization of porous intermetallics,three-dimensional pore morphology scanning technology has the potential to reveal the internal characteristics of pore structures.The research on material properties of porous intermetallics mainly focuses on electrochemical catalytic activity,generalized oxidation resistivity at high temperature,resistance against chemical corrosion and mechanical properties,which have obvious advantages over traditional porous materials.In the field of the development of porous intermetallics,it is expected to expand their applications by further reducing the pore size to the nanoscale level to improve the filtration accuracy or increase the specific surface area,as well as introducing the high entropy design on the composition to improve the brittleness and enhance their material performance.

Genetic and Epigenetic Understanding of the Seasonal Timing of Flowering

The developmental transition to flowering in many plants is timed by changing seasons,which enables plants to flower at a season that is favorable for seed production.Many plants grown at high latitudes perceive the seasonal cues of changing day length and/or winter cold(prolonged cold exposure),to regulate the expression of flowering-regulatory genes through the photoperiod pathway and/or vernalization pathway,and thus align flowering with a particular season.Recent studies in the model flowering plant Arabidopsis thaliana have revealed that diverse transcription factors engage various chromatin modifiers to regulate several key flowering-regulatory genes including FLOWERING LOCUS C(FLC)and FLOWERING LOCUS T(FT)in response to seasonal signals.Here,we summarize the current understanding of molecular and chromatin-regulatory or epigenetic mechanisms underlying the vernalization response and photoperiodic control of flowering in Arabidopsis.Moreover,the conservation and divergence of regulatory mechanisms for seasonal flowering in crops and other plants are briefly discussed.

Molecular epigenetic mechanisms for the memory of temperature stresses in plants

The sessile plants encounter various stresses;some are prolonged,whereas some others are recurrent.Temperature is crucial for plant growth and development,and plants often encounter adverse high temperature fluctuations(heat stresses)as well as prolonged cold exposure such as seasonal temperature drops in winter when grown in temperate regions.Many plants can remember past temperature stresses to get adapted to adverse local temperature changes to ensure survival and/or reproductive success.Here,we summarize chromatin-based mechanisms underlying acquired thermotolerance or thermomemory in plants and review recent progresses on molecular epigenetic understanding of‘remembering of prolonged cold in winter’or vernalization,a process critical for various over-wintering plants to acquire competence to flower in the coming spring.In addition,perspectives on future study in temperature stress memories of economically-important crops are discussed.

Arabidopsis PEAPODs function with LIKE HETEROCHROMATIN PROTEIN1 to regulate lateral organ growth

In higher plants,lateral organs are usually of determinate growth.It remains largely elusive how the determinate growth is achieved and maintained.Previous reports have shown that Arabidopsis PEAPOD(PPD)proteins suppress proliferation of dispersed meristematic cells partly through a TOPLESS corepressor complex.Here,we identified a new PPD-interacting partner,LIKE HETEROCHROMATIN PROTEIN1(LHP1),using the yeast two-hybrid system,and their interaction is mediated by the chromo shadow domain and the Jas domain in LHP1 and PPD2,respectively.Our genetic data demonstrate that the phenotype of ppd2 lhp1 is more similar to lhp1 than to ppd2,indicating epistasis of lhp1 to ppd2.Microarray analysis reveals that PPD2 and LHP1 can regulate expression of a common set of genes directly or indirectly.Consistently,chromatin immunoprecipitation results confirm that PPD2 and LHP1 are coenriched at the promoter region of their targets such as D3-TYPE CYCLINS and HIGH MOBILITY GROUP A,which are upregulated in ppd2,lhp1 and ppd2 lhp1 mutants,and that PPDs mediate repressive histone 3 lysine-27 trimethylation at these loci.Taken together,our data provide evidence that PPD and LHP1 form a corepressor complex that regulates lateral organ growth.

Feedback Regulation of FLC by FLOWERING LOCUS T (FT) and FD through a 5’ FLC Promoter Region in Arabidopsis

Dear Editor, Recently, it was reported that the florigenic FT protein bound to a 3’ region of the potent floral repressor FLC (FLOWERING LOCUS C) to activate the expression of long noncoding antisense RNAs known as COOLAIR and consequently repress FLC expression to control flowering time and seed dormancy in Arabidopsis (Chen and Penfield, 2018). Here, we show that FT represses FLC expression through a 5' promoter region, but not COOLAIR.

Experiencing winter for spring flowering: A molecular epigenetic perspective on vernalization

Many over-wintering plants, through vernalization, overcome a block to flowering and thus acquire competence to flower in the following spring after experiencing prolonged cold exposure or winter cold. The vernalization pathways in different angiosperm lineages appear to have convergently evolved to adapt to temperate climates. Molecular and epigenetic mechanisms for vernalization regulation have been well studied in the crucifer model plant Arabidopsis thaliana.Here, we review recent progresses on the vernalization pathway in Arabidopsis. In addition, we summarize current molecular and genetic understandings of vernalization regulation in temperate grasses including wheat and Brachypodium, two monocots from Pooideae, followed by a brief discussion on divergence of the vernalization pathways between Brassicaceae and Pooideae.

JASMONATE-ZIM DOMAIN proteins engage Polycomb chromatin modifiers to modulate Jasmonate signaling in Arabidopsis

Jasmonate(JA)regulates various aspects of plant growth and development and stress responses,with prominent roles in male reproductive development and defenses against herbivores and necrotrophic pathogens.JASMONATE-ZIM DOMAIN(JAZ)proteins are key regulators in the JA signaling pathway and function to repress the expression of JA-responsive genes.Here,we show that JAZ proteins directly interact with several chromatin-associated Polycomb proteins to mediate repressive chromatin modifications at JA-responsive genes and,thus,their transcriptional repression in Arabidopsis.Genetic analyses revealed that the developmental defects,including anther and pollen abnormalities,resulting from loss or block of JA signaling were partially rescued by loss of Polycomb protein-mediated chromatin silencing(Polycomb repression).We further found that JAZ-mediated transcriptional repression during anther and pollen development requires Polycomb proteins at four key Regulatory loci.Analysis of genome-wide occupancy of a Polycomb factor and transcriptome reprogramming in response to JA revealed that Polycomb repression is involved in the repression of various JA-responsive genes.Taken together,our study reveals an important chromatin-based mechanism for JAZ-mediated transcriptional repression and JA signaling in plants.

Molecular basis of CONSTANS oligomerization in FLOWERING LOCUS T activation

The transcription factor CONSTANS(CO)integrates day-length information to induce the expression of florigen FLOWERING LOCUS T(FT)in Arabidopsis.We recently reported that the C-terminal CCT domain of CO forms a complex with NUCLEAR FACTOR-YB/YC to recognize multiple cis-elements in the FT promoter,and the N-terminal tandem B-box domains form a homomultimeric assembly.However,the mechanism and biological function of CO multimerization remained unclear.Here,we report that CO takes on a head-to-tail oligomeric configuration via its B-boxes to mediate FT activation in long days.The crystal structure of B-boxesCOreveals a closely connected tandem B-box fold forming a continuous head-to-tail assembly through unique CDHH zinc fingers.Mutating the key residues involved in CO oligomerization resulted in a non-functional CO,as evidenced by the inability to rescue co mutants.By contrast,a transgene encoding a human p53-derived tetrameric peptide in place of the B-boxesCOrescued co mutant,emphasizing the essential role of BboxesCO-mediated oligomerization.Furthermore,we found that the four TGTG-bearing cis-elements in FT proximal promoter are required for FT activation in long days.Our results suggest that CO forms a multimer to bind to the four TGTG motifs in the FT promoter to mediate FT activation.

Rapid, automated, and reliable antimicrobial susceptibility test from positive blood culture by CAST‐R

Antimicrobial susceptibility tests(ASTs)are pivotal in combating multidrug resistant pathogens,yet they can be time‐consuming,labor‐intensive,and unstable.Using the AST of tigecycline for sepsis as the main model,here we establish an automated system of Clinical Antimicrobials Susceptibility Test Ramanometry(CAST‐R),based on D2O‐probed Raman microspectroscopy.Featuring a liquid robot for sample pretreatment and a machine learning‐based control scheme for data acquisition and quality control,the 3‐h,automated CAST‐R process accelerates AST by>10‐fold,processes 96 paralleled antibiotic‐exposure reactions,and produces high‐quality Raman spectra.The Expedited Minimal Inhibitory Concentration via Metabolic Activity is proposed as a quantitative and broadly applicable parameter for metabolism‐based AST,which shows 99%essential agreement and 93%categorical agreement with the broth microdilution method(BMD)when tested on 100 Acinetobacter baumannii isolates.Further tests on 26 clinically positive blood samples for eight antimicrobials,including tigecycline,meropenem,ceftazidime,ampicillin/sulbactam,oxacillin,clindamycin,vancomycin,and levofloxacin reveal 93%categorical agreement with BMD‐based results.The automation,speed,reliability,and general applicability of CAST‐R suggest its potential utility for guiding the clinical administration of antimicrobials.

Porous FeAl alloys via powder sintering:Phase transformation,microstructure and aqueous corrosion behavior

This study investigates the phase transformation and microstructure of porous Fe Al parts sintered from elemental powder mixtures using in-situ neutron diffraction and in-situ thermal dilatometry.A single B2 structured Fe Al phase was determined in the sintered Fe Al alloy.The combined effects of the Kirkendall porosity,transient liquid phase,and phase transformations associated with powder sintering all contribute to the swelling phenomenon of the final sintered part.The aqueous corrosion test indicates that the corrosion products include iron oxides in the porous Fe Al parts.The accumulation of corrosion products blocks the pore channel and decreases pore size and permeability over the soaking time.