PEO coating on Mg-Ag alloy:The incorporation and release of Ag species

In the present study,the distribution of Ag in the coating formed on Mg-Ag alloy by plasma electrolytic oxidation(PEO)and its ionic release kinetics when exposed to a 0.9 wt.%Na Cl solution at 37℃have been investigated.Both metallic Ag and Ag oxide particles with~5 to~40 nm in diameters were observed in the PEO coating.Further,an Ag-enriched layer of~20 nm in thickness at the substrate/coating interface was also observed.The PEO coating on the Mg-Ag alloy not only increases its corrosion resistance with the corrosion current density decreasing by up to 3 orders of magnitude from 8.04×10^(-3)to 4.03×10^(-6)A/cm^(2),but also controls the release of Ag+to the level that is sufficient for anti-infective efficacy without causing cytotoxicity to mammal cells.

Structural shift of gut microbiota during chemopreventive effects of epigallocatechin gallate on colorectal carcinogenesis in mice

AIM To investigate the effect of epigallocatechin gallate(EGCG) on structural changes of gut microbiota in colorectal carcinogenesis.METHODS An azoxymethane(AOM)/dextran sodium sulfate(DSS)-induced colitis mouse model was established. Fortytwo female FVB/N mice were randomly divided into the following three groups: group 1(10 mice, negative control) was treated with vehicle, group 2(16 mice, positive control) was treated with AOM plus vehicle, and group 3(16 mice, EG) was treated with AOM plus EGCG. For aberrant crypt foci(ACF) evaluation, the colons were rapidly took out after sacrifice, rinsed with saline, opened longitudinally, laid flat on a polystyrene board, and fixed with 10% buffered formaldehyde solution before being stained with 0.2% methylene blue in saline. For tumor evaluation, the colon was macroscopically inspected and photographed, then the total number of tumors was enumerated and tumor size measured. For histological examination, the fixed tissues were paraffin-embedded and sectioned at 5 mm thickness. Microbial genomic DNA was extracted from fecal and intestinal content samples using a commercial kit. The V4 hypervariable regions of 16 S r RNA were PCR-amplified with the barcoded fusion primers. Using the best hit classification option, the sequences from each sample were aligned to the RDP 16 S r RNA training set to classify the taxonomic abundance in QIIME. Statistical analyses were then performed.RESULTS Treatment of mice with 1% EGCG caused a significant decrease in the mean number of ACF per mouse, when compared with the model mice treated with AOM/DSS(5.38 ± 4.24 vs 13.13 ± 3.02, P < 0.01). Compared with the positive control group, 1% EGCG treatment dependently decreased tumor load per mouse by 85%(33.96 ± 6.10 vs 2.96 ± 2.86, respectively, P < 0.01). All revealed that EGCG could inhibit colon carcinogenesis by decreasing the number of precancerous lesions as well as solid tumors, with reduced tumor load and delayed histological progression of CRC. During the cancerization, the diversity of gut microbiota increased, potential carcinogenic bacteria such as Bacteroides were enriched, and the abundance of butyrate-producing bacteria(Clostridiaceae, Ruminococcus, etc.) decreased continuously. In contrast, the structure of gut microbiota was relatively stable during the intervention of EGCG on colon carcinogenesis. Enrichment of probiotics(Bifidobacterium, Lactobacillu, etc.) might be a potential mechanism for EGCG's effects on tumor suppression. Via bioinformatics analysis, principal coordinate analysis and cluster analysis of the tumor formation process, we found that the diversity of gut microbiota increased in the tumor model group while that in the EGCG interfered group(EG) remained relatively stable.CONCLUSION Gut microbiota imbalance might be a potential mechanism for the prevention of malignant transformation by EGCG, which is significant for diagnosis, treatment, prognosis evaluation, and prevention of colorectal cancer.

Suppression of colorectal tumorigenesis by recombinant Bacteroides fragilis enterotoxin-2 in vivo

AIM To evaluate the impact of recombinant Bacteroides fragilis enterotoxin-2 (BFT-2, or Fragilysin) on colorectal tumorigenesis in mice induced by azoxymethane/dextran sulfate sodium (AOM/DSS). METHODS Recombinant proBFT-2 was expressed in Escherichia coli strain Rosetta (DE3) and BFT-2 was obtained and tested for its biological activity via colorectal adenocarcinoma cell strains SW-480. Seventy C57BL/6J mice were randomly divided into a blank (BC; n = 10), model (AD; n = 20), model + low-dose toxin (ADLT; n = 20, 10 mu g), and a model + high-dose toxin (ADHT; n = 20, 20 mu g) group. Mice weight, tumor formation and pathology were analyzed. Immunohistochemistry determined Ki-67 and Caspase-3 expression in normal and tumor tissues of colorectal mucosa. RESULTS Recombinant BFT-2 was successfully obtained, along with its biological activity. The most obvious weight loss occurred in the AD group compared with the ADLT group (21.82 +/- 0.68 vs 23.23 +/- 0.91, P < 0.05) and the ADHT group (21.82 +/- 0.68 vs 23.57 +/- 1.06, P < 0.05). More tumors were found in the AD group than in the ADLT and ADHT groups (19.75 +/- 3.30 vs 6.50 +/- 1.73, P < 0.05; 19.75 +/- 3.30 vs 6.00 +/- 2.16, P < 0.05). Pathology showed that 12 mice had adenocarcinoma and 6 cases had adenoma in the AD group. Five mice had adenocarcinoma and 15 had adenoma in the ADLT group. Four mice had adenocarcinoma and 16 had adenoma in the ADHT group. The incidence of colorectal adenocarcinoma in both the ADHT group and the ADHT group was reduced compared to that in the AD group (P < 0.05, P < 0.05). The positive rate of Ki-67 in the ADLT group and the ADHT group was 50% and 40%, respectively, both of which were lower than that found in the AD group (94.44%, P < 0.05, P < 0.05). Caspase-3 expression in the ADLT group and the ADHT group was 45% and 55%, both of which were higher than that found in the BC group (16.67%, P < 0.05, P < 0.05). CONCLUSION Oral administration with lower-dose biologically active recombinant BFT-2 inhibited colorectal tumorigenesis in mice.

The Simultaneous Three-channel Multicolor CCD Photometric System of the 1.2 m Telescope at Jilin Astronomical Observatory

We will introduce the construction and design of a new simultaneous three-channel multicolor CCD photometer.This photometer has been mounted on the 1.2 m telescope at Jilin Astronomical Observatory,and is applied to study space debris,gamma-ray burst afterglows,asteroids and other rapidly variable objects.As one of the ground follow-up telescopes of the Chinese-French Space-based multi-band astronomical Variable Objects Monitor(SVOM)mission,it appears very essential to evaluate the performance of the photometry system of this photometer,which can achieve simultaneous imaging within a field of view of 21’.5×21’.5,21’.5×21’.5 and21’.3×21’.3 in the Sloan Digital Sky Survey(SDSS)g’,r’,i’bands,respectively.Photometric calibrations were carried out by using plenty of SDSS standard stars,and the relationship between the photometric system and the Johnson-Bessel filter system was also studied.The results of the performance evaluation from observing open cluster M67 are presented.

Altering polythiophene derivative substrates to explore the mechanism of heterogeneous lithium nucleation for dendrite-free lithium metal anodes

Lithium metal batteries(LMBs)possess outstanding theoretical energy density and have attracted widespread attention as the next generation of energy storage devices for various crucial applications.However,the commercialization of LMBs has to simultaneously overcome numerous challenges,such as inferior Coulombic efficiency and cycling performance,high self-discharge,and complicated interfacial reactions.It has traditionally been an enormous challenge about the uniform deposition of lithium on the surface of current collector to relieve the formation of lithium dendrites.In this study,a novel efficient strategy of plating uniform lithiophilic polythiophene derivatives substrates on Cu foils was developed and the nucleation mechanism of Li ions on polythiophene derivatives substrates was further explored.We first explored the interaction between polythiophene derivatives substrates and Li ions by firstprinciples calculations,and found shorter side chains of polythiophene derivatives can enhance the adsorption energy and promote the diffusion rate of Li ions.Polythiophene derivatives substrates have a large number of dispersive lipophilic sites and Li ions diffusion channels in the main chain,which can effectively regulate the nucleation and growth stages of Li ions deposition.We further found polythiophene derivatives with different side chains can induce the electrodeposition of Li ions with different morphology,while the polythiophene derivatives with the shortest side chains can contribute to the most excellent cycle efficiency,resulting in a uniform lithium deposition with less lithium dendritic growth experimentally.

Relation between Cardiac Injury and Elevated Levels of Inflammatory Biomarkers in Patients with Severe COVID-19

Background:Since early December 2019,coronavirus disease 2019(COVID-19)has emerged as a global pandemic and public health crisis.This study aims to explore the relationship between cardiac injury and infl ammatory biomarkers in patients with severe COVID-19.Methods:We collected data on 91 patients with a confi rmed diagnosis of severe COVID-19 from February 8 to March 31,2020.Demographic characteristics,clinical data,and in-hospital outcomes were compared.The relationship between cardiac injury and infl ammatory biomarkers was analyzed.Logistic regression was used to explore the independent risk factors for cardiac injury.Results:The mean age of all patients was 61 years±14 years.About half of the patients were male.Hypertension and coronary heart disease were more common in the cardiac injury group.The levels of infl ammatory biomarkers in patients who experienced cardiac injury were generally higher than the levels of those without cardiac injury,including interleukin-6,interleukin-2 receptor(IL-2R),procalcitonin,and high-sensitivity C-reactive protein.There were positive correlations between the levels of high-sensitivity troponin I and N-terminal prohormone of brain natriuretic peptide and the levels of infl ammatory biomarkers.Logistic regression shows that IL-2R(odds ratio 1.001,95%confi dence interval 1.000–1.002,P=0.045)and comorbidities(odds ratio 4.909,95%confi dence interval 1.231–19.579,P=0.024)are independent risk factors for cardiac injury in patients with severe COVID-19.Conclusion:High levels of infl ammatory biomarkers are associated with higher risk of cardiac injury in patients with severe COVID-19.IL-2R and comorbidities are predictors of cardiac injury.

Effect of Mn Addition and Heat Treatment on the Corrosion Behaviour of Mg-Ag-Mn Alloy

The high corrosion sensitivity and the potential bio-toxicity of Mg-Ag alloys limit their wide applications for the production of implanted devices. In the present work, Mn is added into the Mg-Ag alloy to optimize its corrosion behaviour. The corrosion behaviour of Mg-Ag-Mn alloys is investigated with the underlying microstructural factors examined. The Mg-Ag alloy with 2 wt% Mn exhibits the highest corrosion resistance after post-casting heat treatment at 440 ℃. The addition of Mn results in α-Mn phase with the incorporation of Fe, which suppresses the cathodic activity of impurity Fe. Further, heat treatment of the cast alloys homogenizes the distribution of Ag and promotes the precipitation of α-Mn phase. The former removes Ag segregations as potential cathodes;the latter promotes a more uniform distribution of cathodes and, therefore, prevents localized corrosion.

Induced transformation of antimony trioxide by Mn(II) oxidation and their co-transformed mechanism

Antimony(Sb)is a toxic and carcinogenic element that often enters soil in the form of antimony trioxide(Sb_(2)O_(3))and coexists with manganese(Mn)in weakly alkaline conditions.Mn oxides such as birnessite have been found to promote the oxidative dissolution of Sb_(2)O_(3),but few researches concerned the co-transformations of Sb_(2)O_(3) and Mn(II)in environment.This study investigated themutual effect of abiotic oxidation of Mn(II)and the coupled oxidative dissolution of Sb_(2)O_(3).The influencing factors,such as Mn(II)concentrations,pH and oxygen were also discussed.Furthermore,their co-transformed mechanism was also explored based on the analysis of Mn(II)oxidation products with or without Sb_(2)O_(3) using XRD,SEM and XPS.The results showed that the oxidative dissolution of Sb_(2)O_(3) was enhanced under higher pH and higher Mn(II)loadings.With a lower Mn(II)concentration such as 0.01 mmol/L Mn(II)at pH 9.0,the improved dissolution of Sb_(2)O_(3) was attributed to the generation of dissolved intermediate Mn(III)species with strong oxidation capacity.However,under higher Mn(II)concentrations,both amorphous Mn(III)oxides and intermediate Mn(III)species were responsible for promoting the oxidative dissolution of Sb_(2)O_(3).Most released Sb(∼72%)was immobilized by Mn oxides and Sb(V)was dominant in the adsorbed and dissolved total Sb.Meanwhile,the presence of Sb_(2)O_(3) not only inhibited the removal of Mn(II)by reducing Mn(III)to Mn(II)but also affected the final products of Mn oxides.For example,amorphous Mn oxides were formed instead of crystalline Mn(III)oxides,such as MnOOH.Furthermore,rhodochrosite(MnCO_(3))was formed with the high Mn(II)/Sb_(2)O_(3) ratio,but without being observed in the low Mn(II)/Sb_(2)O_(3) ratio.The results of study could help provide more understanding about the fate of Sb in the environment and the redox transformation of Mn.

7株伦敦沙门菌药敏检测和分子分型分析

目的对7株疑似伦敦沙门菌进行病原学诊断、药物敏感性和PFGE分子分型检测,为贵州省伦敦沙门菌的病原学诊断和防控提供科学依据。方法对来自贵州省的7株疑似伦敦沙门菌进行分离培养和传统生化鉴定,对明确为沙门菌的菌株进行诊断血清分型,微量肉汤稀释法测定16种药物最小抑菌浓度,脉冲场凝胶电泳(Pulsed Field Gel Electrophoresis,PFGE)进行分子分型检测。结果 7株疑似伦敦沙门菌经系统生化鉴定为沙门菌,进一步诊断血清凝集明确为伦敦沙门菌;全部菌株对链霉素(Streptomycin,STR)耐药,对阿莫西林/克拉维酸(Amoxicillin/clavulanic acid,AMC)、头孢曲松(Ceftriaxone,CRO)、头孢吡肟(Cefepime,FEP)、萘啶酸(Nalidixic acid,NAL)、亚胺培南(Imipenem,IPM)敏感,对氨苄西林(Ampicillin,AMP)、庆大霉素(Gentamicin,GEN)、磺胺异噁唑(Sulfamethoxazole,SOX)、复方新诺明(Trimethoprim/sulfamethoxazole,SXT)、阿奇霉素(Azithromycin,AZM)和多西环素(Doxycycline,DOX)的耐药率均为85. 7%,多种药物MIC50和MIC90均为所测量范围的上限,85. 7%的菌株存在耐多药的情况,57. 1%的菌株耐药谱AMP+STR+SOX+TCY+CIP+SXT+DOX+GEN+AZM; 7株伦敦沙门菌经XbalⅠ酶切后分成3种PFGE型,5株菌株PFGE带型相似性为100%,其中4株菌株的PFGE带型和耐药谱一致。结论贵州省伦敦沙门菌多重耐药情况严重,耐药表型与PFGE分型具有相关性,应加强对沙门菌的耐药和分子分型监测。

贵州省2010-2015年细菌性痢疾流行病学特征分析

目的了解贵州省细菌性痢疾(菌痢)的发病特征及流行趋势,为制订防治策略提供科学依据。方法对贵州省2010-2015年菌痢疫情资料进行描述性流行病学分析。结果 2010-2015年贵州省共报告菌痢病例34 580例,6年报告平均发病率为16.28/10万。发病率较高的地区依次为黔南州、黔西南州和安顺市。5~9月为发病高峰。男女发病比为1.45∶1,其中0~4岁和15~20岁组发病最多(占病例总数的55.70%)。职业分布以农民(46.06%)、散居儿童(32.24%)和学生(9.30%)为主。病原菌型监测显示,志贺菌总的阳性检出率为2.57%(97/3 778),以宋内志贺菌菌株为主,占91.75%(89/97)。志贺菌株的耐药情况较为普遍,菌株对环丙沙星和庆大霉素等药物敏感。2010-2015年通过电话、网络等共报告菌痢突发事件41起,事件集中发生在5~10月,36起发生在学校,32起可能为水源性暴发,易引起菌痢暴发疫情的病原是福氏志贺菌。结论贵州省菌痢发病呈下降趋势但仍是危害群众身体健康的重要疾病之一。重点加强学校、农村的防控工作,切实落实综合性防控措施,减少菌痢的危害。

Structure and Properties of Gel-spun Ultra-high Molecular Weight Polyethylene Fibers with High Gel Solution Concentration

The gel-spun ultra-high molecular weight polyethylene （UHMWPE） fibers were prepared at the industrial production line with different gel solution concentrations of 15 wt%, 18 wt% and 24 wt%. The difference in ultimate structure and mechanical properties of UHMWPE fibers for different gel solution concentrations were analyzed by tensile testing, differential scanning calorimetry （DSC）, wide angle X-ray diffraction （WAXD） and small angle X-ray scattering （SAXS）. With the increase of gel solution concentration, the ultimate mechanical properties of UHMWPE fibers were decreased and the crystallization and orientation of UHMWPE fibers became inferior. Besides, both the average shish length （ （Lshsh） ） and shish misorientation （B0） of UHMWPE fibers were decreased with the increase of gel solution concentration. In addition, the appropriate increase of spinning temperature led to the further optimization of the ultimate structure and mechanical properties of UHMWPE fibers.

Multiple Endothermic Peaks Resulted from Different Crystal Structures in an Isomorphous Copolymer Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The multiple endothermic peaks of poly（3-hydroxybutyrate-co-3-hydroxyvalerate） （P（HB-co-HV）） in differential scanning calorimetry （DSC） results, as one representative phenomenon of polymer with unique cocrystallization behavior, were generally considered as the results of melting/recrystallization. In this study, wide angle X-ray diffraction （WAXD） and small angle X-ray scattering （SAXS） experiments were conducted to analyze the phenomena of multiple endothermic peaks in DSC results. The results of these analyses indicated that the multiple endotherms were mainly caused by different lamellae structures. For P（HB-co-HV） with lower HV content, it was comprised of two structures of HV total exclusion and HV partial inclusion in the crystal lamellae. For P（HB-co-HV） with higher HV content, it was also comprised of two structures of HV total inclusion and HV partial inclusion in the crystal lamellae. However, only structure with HV partial inclusion in the crystal lamellae remained existing after first melting peak for all samples.

Design, Synthesis, and Evaluation of Fungicidal Activity of Novel Pyrazole-Containing Strobilurin Derivatives

In searching for novel fungicidal leads,a series of pyrazole-containing strobilurins were rationally designed,synthesized and charac-terized.Bioassay indicated that compound 1-7 displayed excellent fungicidal activity against a broad spectrum of plant pathogens such as Gibberella zeae,Rhizoctonia cereolis,Sclerotinia sclerotiorum,Phytophthora infestans,Physolosporo piricola and Pellicularia sosakii with EC_(50) of 0.16,0.02,0.72,0.07,0.77 and 0.65μg/mL,respectively,which were 3-10 times more potent than the positive control azoxystrobin against the corresponding pathogens.Moreover,like azoxystrobin and kresoxim methyl,1-7,displayed excellent protec-tive activity against P.sorghi.Molecular docking validated that 1-7 and azoxystrobin would share a similar binding mode with cytochrome bc_(1) complex.This study demonstrates that 1-7 is a promising fungicidal candidate for further development.

The Influence of Chitin Nanocrystals on Structural Evolution of Ultra-high Molecular Weight Polyethylene/Chitin Nanocrystal Fibers in Hot-drawing Process

Ultra-high molecular weight polyethylene（UHMWPE）/chitin nanocrystal（CNC） fibers were prepared. Compared with the pure UHMWPE fibers, the ultimate tensile strength and Young＇s modulus of UHMWPE/CNC fibers are improved by 15.7% and 49.6%, respectively, with the addition of chitin nanocrystals（CNCs） of 1 wt%. The melting temperature（Tm） of UHMWPE/CNC fibers was higher than that of pure UHMWPE fibers. Pure UHMWPE fibers and UHMWPE/CNC fibers were characterized with respect to crystallinity, orientation and kebab structure by wide-angle X-ray diffraction（WAXD）, small-angle X-ray scattering（SAXS） and scanning electron microscopy（SEM）. It is found that the CNCs act as the shish structure in UHMWPE/CNC fibers and the kebab crystals are grown around the CNCs. There was almost no difference between pure UHMWPE fibers and UHMWPE/CNC fibers in orientation. But the degree of crystallinity of various stages of UHMWPE/CNC fibers was respectively higher than the corresponding stage of pure UHMWPE fibers. Moreover, the addition of 1 wt% CNCs improved the thickness of kebab crystals and accelerated the transformation of kebab to shish.

Characterization of Structural Knot Distributions in UHMWPE Fibers

Microbeam wide-angle X-ray diffraction（WAXD） experiments were carried out at different structural knot positions of SIOC and M4 fibers of ultra-high molecular weight polyethylene（UHMWPE）. The optical microscope images revealed that SIOC fiber had bamboo-like structural knots, and M4 fiber had chaotic distribution of structural knots. WAXD patterns showed the monoclinic unit cell in the whole M4 fiber, but different lamellar orientations in the bamboo joint of SIOC fiber. In addition, small-angle X-ray scattering（SAXS） patterns confirmed that the SIOC fiber contained uniform distribution of shish structures, and differential scanning calorimetry（DSC） measurements showed that its less branched and short chains benefited the orthorhombic-hexagonal phase transformation.

Single-molecule investigation of human telomeric G-quadruplex interactions with Thioflavin T

G-quadruplex ligands have been accepted as potential therapeutic agents for anticancer treatment. Thioflavin T （ThT）, a highly selective G-quadruplex ligand, can bind G-quadruplex with a fluorescent light-up signal change and high specificity against DNA duplex. However, there are still different opinions that ThT induces/stabilizes G-quadruplex foldings/topologies in human telomere sequence. Here, a sensitive single-molecule nanopore technology was utilized to analyze the interactions between human telomeric DNA （Tel DNA） and ThT. Both translocation time and current blockade were measured to investigate the translocation behaviors. Furthermore, the effects of metal ion （K~ and Na~） and pH on the translocation behaviors were studied. Based on the single-molecule level analysis, there are some conclusions： （1） In the electrolyte solution containing 50 mmol/L I（Cl and 450 mmol/L NaCl, ThT can bind strongly with Tel DNA but nearly does not change the G-quadruplex form; （2） in the presence of high concentration K~, the ThT binding induces the structural change of hybrid G-quadruplex into antiparallel topology with an enhanced structural stability; （3） In either alkaline or acidic buffer, G-quadruplex form will change in certain degree. All above conclusions are helpful to deeply understand the interaction behaviors between Tel DNA and ThT. This nanopore platform, investigating G-quadruplex ligands at the single-molecule level, has great potential for the design of new drugs and sensors.

Microstructure and Corrosion Resistance of Plasma Electrolytic Oxidized Recycled Mg Alloy

The wide application of Mg is hindered by its low corrosion resistance,especially for recycled Mg.In this work,a novel plasma electrolytic oxidation(PEO)process was conducted on a recycled Mg alloy with a high content of Al(~2.3 wt%),which results in a polycrystalline PEO coating.The PEO coating displays a three-layered structure with a uniform elemental distribution.Unlike the outer layer decorated by channels of micrometre scales,the middle layer mainly contains submicronsized pores associated with plasma discharges,whereas the fine pores originated from oxygen evolution were detected in the inner layer.The electrochemical measurements,hydrogen evolution tests and salt spray tests were conducted,indicating the superior corrosion resistance of PEO-coated recycled Mg alloy.Hence,the purposed PEO method could dramatically enhance the corrosion resistance of recycled Mg,which may broaden its application in the future.

A designed locked nucleic acid-based nanopore for discriminating ctDNA and its coexisting analogue ncDNA

Circulating tumor DNA(ctDNA),carrying tumor-specific sequence mutations,is a promising biomarker for classification,diagnosis and prognosis of cancers.However,there is still a great challenge in discriminating single-base difference between ctDNA and its coexisting analogue(normal circulating DNA,ncDNA)at a serum sample.A locked nucleic acid(LNA)probe combined with a-HL nanopore sensor was designed,which achieved a high signal-to-background ratio(SBR)of^8.34 × 10^3,as well as a significant discrimination capability(~12.3 times)of single-base diffe rence.The accurate discrimination strategy is label-free,convenient,selective and sensitive,which has great potential in the early diagnosis of diseases and biomedical research fields.

A Synchrotron in situ X-ray Study on the Multiple Melting Behaviors of Isomorphous Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(P(HB-co-HV))with Middle HV Content

The multiple endothermic peaks without observable recrystallization phenomenon of isomorphous poly(3-hydroxybutyrate-co-3-hydroxyvalerate)[P(HB-co-HV)]with the middle HV content of 19.4 mol%and 28.7 mol%were confirmed by differential scanning calorimetry(DSC),and the evolutions of crystal structure and lamellar morphology in the heating and melting process were tracked by in situ synchrotron wide angle X-ray diffraction(WAXD)and small angle X-ray scattering(SAXS)techniques.The emergence of asymmetric features of both the diffraction peaks and scattering curves indicates the coexistence of different lamellar crystals with varied unit cell parameters.Based on the in situ WAXD and SAXS measurements,we calculated the evolutions of the unit cell parameters a and b as well as the long period and lamellar thickness upon heating.The comparative analysis of WAXD and SAXS data confirms that the multiple endothermic peaks of P(HB-co-19.4%HV)and P(HB-co-28.7%HV)result from the melting of different lamellae rather than the melting/recrystallization.The thinner,unstable uniform lamellae with HV counits total inclusion melt first and the thicker,stable sandwich lamellae with HV counits partial inclusion melt last.In addition,the large second melting peak in P(H B-co-19.4%HV),differing from that of samples with HV content of 28.7 mol%and 36.2 mol%,is due to the unique state of HV content leading to a transition of sandwich lamellae to uniform lamellae.The present study establishes the relationship between the different lamellae structure and multiple melting behaviors of isomorphous copolymer.

Cross section measurement for the^(232)Th(n,f)reaction in the 4.50−5.40 MeV region using a time projection chamber

Accurate cross sections of neutron induced fission reactions are required in the design of advanced nuclear systems and the development of fission theory.Time projection chambers(TPCs),with their track reconstruction and particle identification capabilities,are considered the best detectors for high-precision fission cross section measurements.The TPC developed by the back-streaming white neutron source(Back-n)team of the China Spallation Neutron Source(CSNS)was used as the fission fragment detector in measurements.In this study,the cross sections of the ^(232)Th(n,f)reaction at five neutron energies in the 4.50−5.40 MeV region were measured.The fission fragments and α particles were well identified using our TPC,which led to a higher detection efficiency of the fission fragments and smaller uncertainty of the measured cross sections.Ours is the first measurement of the ^(232)Th(n,f)reaction using a TPC for the detection of fission fragments.With uncertainties less than 5%,our cross sections are consistent with the data in different evaluation libraries,including JENDL-4.0,ROSFOND-2010,CENDL-3.2,ENDF/B-VⅢ.0,and BROND-3.1,whose uncertainties can be reduced after future improvement of the measurement.