根据国际温度咨询委员会辐射测温工作组(CCT-WG5)对世界各国计量机构开展Co-C共晶点研制工作的相关要求,设计并搭建了Co-C共晶点灌注系统,采用直接共晶法成功灌注了满足复现实验要求的Co-C共晶点坩埚。针对直接共晶灌注法效率低、坩埚...根据国际温度咨询委员会辐射测温工作组(CCT-WG5)对世界各国计量机构开展Co-C共晶点研制工作的相关要求,设计并搭建了Co-C共晶点灌注系统,采用直接共晶法成功灌注了满足复现实验要求的Co-C共晶点坩埚。针对直接共晶灌注法效率低、坩埚破裂风险大的缺陷,提出了对灌注方法的改进方案,并依据该方案成功灌注了2个Co-C共晶点坩埚。对灌注的Co-C-2#共晶点进行了复现试验,结果显示:拐点温度的不确定度为5. 3 m K,满足小于10 m K的CCT要求;短期重复性为9. 6 m K,满足小于20 m K的CCT要求。展开更多
Wheat(Triticum aestivum L.) is one of the three major global food crops. Hightemperature stress can affect its yield and quality. Studies of the effect of hightemperature stress on wheat kernel development are importa...Wheat(Triticum aestivum L.) is one of the three major global food crops. Hightemperature stress can affect its yield and quality. Studies of the effect of hightemperature stress on wheat kernel development are important because they can reveal the stability of wheat quality and lead to the genetic improvement of wheat quality traits. In this study, the isobaric tags for relative and absolute quantitation(iTRAQ)method was adopted to analyze changes in the protein expression profile of wheat cultivars under high temperature stress. The protein content of wheat grain increased under heat stress, while the SDS-sedimentation value and starch content decreased.Grain filling was deficient under high temperature stress, which reduced thousandkernel weight but did not affect wheat kernel length. The 207 differentially expressed proteins identified in Gaocheng 8901 under heat stress were associated with energy metabolism, growth and development, and stress response. Gene Ontology enrichment analysis showed that the annotated proteins that were differentially expressed in Gaocheng 8901 under heat stress were involved mainly in stimulus response, abiotic stress response, stress response, and plasma membrane. A set of 78 differentially expressed proteins were assigned to 83 KEGG signaling/metabolic pathways. KEGG pathway enrichment analysis showed that this set of proteins was significantly enriched in members of 51 pathways, and the proteins participated mainly in protein synthesis in the endoplasmic reticulum, starch and sucrose metabolism, and reaction on ribosomes. Five differentially expressed proteins were involved in protein–protein interaction networks that may greatly influence the yield and quality of wheat grain. In wheat, high-temperature stress leads to a variety of effects on protein expression and may ultimately cause changes in yield and quality.展开更多
Observing GeV gamma-rays is an important goal of the DArk Matter Particle Explorer(DAMPE)for indirect dark matter searching and high energy astrophysics. In this work, we present a set of accurate instrument response ...Observing GeV gamma-rays is an important goal of the DArk Matter Particle Explorer(DAMPE)for indirect dark matter searching and high energy astrophysics. In this work, we present a set of accurate instrument response functions for DAMPE(DmpIRFs) including the effective area, point-spread function and energy dispersion, which are crucial for gamma-ray data analysis based on statistics from simulation data. A dedicated software named DmpST is developed to facilitate the scientific analyses of DAMPE gamma-ray data. Considering the limited number of photons and angular resolution of DAMPE, the maximum likelihood method is adopted in DmpST to better disentangle different source components. The basic mathematics and framework regarding this software are also introduced in this paper.展开更多
The DArk Matter Particle Explorer（DAMPE）,also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals o...The DArk Matter Particle Explorer（DAMPE）,also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.展开更多
Poly(vinyl alcohol)(PVA)/reduced graphene oxide(rGO)nanocomposites is prepared by the immersion of PVA/graphene oxide(GO)nanocomposites in the reducing agent aqueous solution.The PVA/graphene nanocomposites can be use...Poly(vinyl alcohol)(PVA)/reduced graphene oxide(rGO)nanocomposites is prepared by the immersion of PVA/graphene oxide(GO)nanocomposites in the reducing agent aqueous solution.The PVA/graphene nanocomposites can be used as scaffold after treatment by chemical crosslinking agents.The surface hydrophilicity of the nanocomposite scaffolds decreased with the addition of GO or rGO by measuring the contact angles of scaffolds.The electrical conductivity of PVA/rGO nanocomposite scaffold increased with rGO content increased.The highest conductivity of PVA/rGO nanocomposite scaffolds with 10 wt%rGO could reach to 12.16×10^(−3)S/m.The NIH-3T3 fibroblasts attach and grow well on the surface of PVA/rGO nanocomposite scaffolds with increasing the content of rGO.The number of cells obviously increases on the PVA/rGO nanocomposite scaffolds,especially,at 5 wt%and 10 wt%rGO.Furthermore,a good level of conductivity and a variation in the surface property of the PVA/rGO nanocomposite scaffolds have affected NIH-3T3 fibroblasts grow.展开更多
The three major large-scale, diffuse γ-ray structures of the Milky Way are the Galactic disk,a bulge-like GeV excess towards the Galactic center, and the Fermi bubble. Whether such structures can also be present in o...The three major large-scale, diffuse γ-ray structures of the Milky Way are the Galactic disk,a bulge-like GeV excess towards the Galactic center, and the Fermi bubble. Whether such structures can also be present in other normal galaxies remains an open question. M31, as the nearest massive normal galaxy, holds promise for spatially-resolving the γ-ray emission. Based on more than 8 years of Fermi-LAT observations, we use(1) disk,(2) bulge, and(3) disk-plus-bulge templates to model the spatial distribution of the γ-ray emission from M31. Among these, the disk-plus-bulge template delivers the best-fit, in which the bulge component has a TS value 25.7 and a photon-index of 2.57 ± 0.17, providing strong evidence for a centrally-concentrated γ-ray emission from M31, that is analogous to the Galactic center excess. The total0.2–300 GeV γ-ray luminosity from this bulge component is(1.16 ± 0.14) × 1038 erg s-1, which would require ～ 1.5 × 105 millisecond pulsars, if they were the dominant source. We also search for a Fermi bubble-like structure in M31 using the full dataset(pass8), but no significant evidence has been found.In addition, a likelihood analysis using only photons with the most accurate reconstructed direction(i.e.,PSF3-only data) reveals a 4.8 σ point-like source located at ～10 kpc to the northwest of the M31 disk, with a luminosity of(0.97 ± 0.27) × 1038 erg s-1 and a pho@ton-$i·nd3 ex of 2.31 ± 0.18. Lacking a counterpart on the southeast side of the disk, the relation between this point-like source and a bubble-like structure remains elusive.展开更多
The frequent detection of binary mergers of^30 M⊙black holes(BHs)by the Laser Interferometer Gravitational-Wave Observatory(LIGO)rekindled researchers’interest in primordial BHs(PBHs)being dark matter(DM).In this wo...The frequent detection of binary mergers of^30 M⊙black holes(BHs)by the Laser Interferometer Gravitational-Wave Observatory(LIGO)rekindled researchers’interest in primordial BHs(PBHs)being dark matter(DM).In this work,we investigated PBHs distributed as DM with a monochromatic mass of 30 M⊙and examined the encounter-capture scenario of binary formation,where the densest central region of DM halo dominates.Thus,we paid special attention to the tidal effect by the supermassive black hole(SMBH)present.In doing so,we discovered a necessary tool called loss zone that complements the usage of loss cone.We found that the tidal effect is not prominent in affecting binary formation,which also turned out to be insufficient in explaining the totality of LIGO’s event rate estimation,especially due to a microlensing event constraining the DM fraction in PBH at the mass of interest from near unity to an order smaller.Meanwhile,an early-universe binary formation scenario proves so prevailing that the LIGO signal in turn constrains the PBH fraction below one percent.Thus,people should put more faith in alternative PBH windows and other DM candidates.展开更多
Objective： It is known that chronic hepatitis B virus （HBV） infection is a main risk factor for hepatocellular carcinoma （HCC）. To assess the effect of HBV infection and its interaction with other factors on the ...Objective： It is known that chronic hepatitis B virus （HBV） infection is a main risk factor for hepatocellular carcinoma （HCC）. To assess the effect of HBV infection and its interaction with other factors on the risk for HCC, a hospital-based case-control study was carried out in Northeast China. Methods： A total of 384 cases with hepatocellular carcinoma and 432 controls without evidence of liver diseases were enrolled in the study. Blood samples were collected to detect the serum markers of hepatitis B virus （HBV） and hepatitis C virus （HCV） and questionnaires about lifestyle and family tumor history were performed in all subjects. Results： The total infection rate of HBV in hepatocellular carcinoma cases was 70.8% and 10.0% in non-liver disease controls. There was a statistically significant difference （P〈0.0001） between cases and controls （OR= 22.0; 95%CI：15.0-32.3）. Interaction analysis indicated that in HBV chronic carriers with HCV infection or alcohol consumption or family HCC history, the risk for HCC increased （OR=41.1, 95%CI： 20.2-83.9, OR=125.0, 95%CI： 66.5-235.2; OR=56.9, 95%CI： 27.2-119.3 respectively）. In addition, hepatitis B history, HCV infection, hepatic cirrhosis and family history of HCC were also potential HCC independent risk factors. Conclusion： We confirmed that HBV is a chief risk factor for hepatocellular carcinoma and accounts for 67.7% of all hepatocellular carcinoma in Northeast China. HCV infection, alcohol intake and family history could enhance the risk for HCC in chronic HBV carriers.展开更多
文摘根据国际温度咨询委员会辐射测温工作组(CCT-WG5)对世界各国计量机构开展Co-C共晶点研制工作的相关要求,设计并搭建了Co-C共晶点灌注系统,采用直接共晶法成功灌注了满足复现实验要求的Co-C共晶点坩埚。针对直接共晶灌注法效率低、坩埚破裂风险大的缺陷,提出了对灌注方法的改进方案,并依据该方案成功灌注了2个Co-C共晶点坩埚。对灌注的Co-C-2#共晶点进行了复现试验,结果显示:拐点温度的不确定度为5. 3 m K,满足小于10 m K的CCT要求;短期重复性为9. 6 m K,满足小于20 m K的CCT要求。
基金supported by the National Key Research and Development Program of China(2016YFD0100502)
文摘Wheat(Triticum aestivum L.) is one of the three major global food crops. Hightemperature stress can affect its yield and quality. Studies of the effect of hightemperature stress on wheat kernel development are important because they can reveal the stability of wheat quality and lead to the genetic improvement of wheat quality traits. In this study, the isobaric tags for relative and absolute quantitation(iTRAQ)method was adopted to analyze changes in the protein expression profile of wheat cultivars under high temperature stress. The protein content of wheat grain increased under heat stress, while the SDS-sedimentation value and starch content decreased.Grain filling was deficient under high temperature stress, which reduced thousandkernel weight but did not affect wheat kernel length. The 207 differentially expressed proteins identified in Gaocheng 8901 under heat stress were associated with energy metabolism, growth and development, and stress response. Gene Ontology enrichment analysis showed that the annotated proteins that were differentially expressed in Gaocheng 8901 under heat stress were involved mainly in stimulus response, abiotic stress response, stress response, and plasma membrane. A set of 78 differentially expressed proteins were assigned to 83 KEGG signaling/metabolic pathways. KEGG pathway enrichment analysis showed that this set of proteins was significantly enriched in members of 51 pathways, and the proteins participated mainly in protein synthesis in the endoplasmic reticulum, starch and sucrose metabolism, and reaction on ribosomes. Five differentially expressed proteins were involved in protein–protein interaction networks that may greatly influence the yield and quality of wheat grain. In wheat, high-temperature stress leads to a variety of effects on protein expression and may ultimately cause changes in yield and quality.
基金supported in part by the National Key Program for Research and Development (2016YFA0400200)the Strategic Priority Research Program of Chinese Academy of Sciences (XDB23040000)+3 种基金the 13th Five-year Informatization Plan of Chinese Academy of Sciences (XXH13506)the National Natural Science Foundation of China (Nos. U1631111, U1738123, U1738136 and U1738210)Youth Innovation Promotion Association of Chinese Academy of Sciencesthe Young Elite Scientists Sponsorship Program
文摘Observing GeV gamma-rays is an important goal of the DArk Matter Particle Explorer(DAMPE)for indirect dark matter searching and high energy astrophysics. In this work, we present a set of accurate instrument response functions for DAMPE(DmpIRFs) including the effective area, point-spread function and energy dispersion, which are crucial for gamma-ray data analysis based on statistics from simulation data. A dedicated software named DmpST is developed to facilitate the scientific analyses of DAMPE gamma-ray data. Considering the limited number of photons and angular resolution of DAMPE, the maximum likelihood method is adopted in DmpST to better disentangle different source components. The basic mathematics and framework regarding this software are also introduced in this paper.
基金founded by the strategic priority science and technology projects in space science of the Chinese Academy of Sciences (Nos.XDA04040000 and XDA04040400)supported in part by the National Key Research and Development Program of China (2016YFA0400200)+7 种基金the National Basic Research Program of China (No.2013CB837000)the Strategic Priority Research Program of the Chinese Academy of Sciences “Multi-Waveband Gravitational Wave Universe” (No.XDB23040000)Youth Innovation Promotion Association of CASthe National Natural Science Foundation of China (Nos.11525313,11673075,11773086,11303107,11303105,11773085,U1738123,U1738136,U1738207 and U1738210)the Young Elite Scientists Sponsorship program by CAST (No.YESS20160196)the 100 Talents Program of Chinese Academy of Sciencessupport by the Swiss National Science Foundation (SNSF)Switzerland and the National Institute for Nuclear Physics (INFN),Italy
文摘The DArk Matter Particle Explorer（DAMPE）,also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.
基金financially supported by the Wisconsin Institute for Discovery(WID)at the University of Wisconsin-Madison and the China Scholarship Council.
文摘Poly(vinyl alcohol)(PVA)/reduced graphene oxide(rGO)nanocomposites is prepared by the immersion of PVA/graphene oxide(GO)nanocomposites in the reducing agent aqueous solution.The PVA/graphene nanocomposites can be used as scaffold after treatment by chemical crosslinking agents.The surface hydrophilicity of the nanocomposite scaffolds decreased with the addition of GO or rGO by measuring the contact angles of scaffolds.The electrical conductivity of PVA/rGO nanocomposite scaffold increased with rGO content increased.The highest conductivity of PVA/rGO nanocomposite scaffolds with 10 wt%rGO could reach to 12.16×10^(−3)S/m.The NIH-3T3 fibroblasts attach and grow well on the surface of PVA/rGO nanocomposite scaffolds with increasing the content of rGO.The number of cells obviously increases on the PVA/rGO nanocomposite scaffolds,especially,at 5 wt%and 10 wt%rGO.Furthermore,a good level of conductivity and a variation in the surface property of the PVA/rGO nanocomposite scaffolds have affected NIH-3T3 fibroblasts grow.
基金supported by the 973 Program (2017YFA0402600 and 2015CB857100)the National Natural Science Foundation of China (GrantNos. 11473010, 11133001, 11773014, 11633007 and11851305)
文摘The three major large-scale, diffuse γ-ray structures of the Milky Way are the Galactic disk,a bulge-like GeV excess towards the Galactic center, and the Fermi bubble. Whether such structures can also be present in other normal galaxies remains an open question. M31, as the nearest massive normal galaxy, holds promise for spatially-resolving the γ-ray emission. Based on more than 8 years of Fermi-LAT observations, we use(1) disk,(2) bulge, and(3) disk-plus-bulge templates to model the spatial distribution of the γ-ray emission from M31. Among these, the disk-plus-bulge template delivers the best-fit, in which the bulge component has a TS value 25.7 and a photon-index of 2.57 ± 0.17, providing strong evidence for a centrally-concentrated γ-ray emission from M31, that is analogous to the Galactic center excess. The total0.2–300 GeV γ-ray luminosity from this bulge component is(1.16 ± 0.14) × 1038 erg s-1, which would require ～ 1.5 × 105 millisecond pulsars, if they were the dominant source. We also search for a Fermi bubble-like structure in M31 using the full dataset(pass8), but no significant evidence has been found.In addition, a likelihood analysis using only photons with the most accurate reconstructed direction(i.e.,PSF3-only data) reveals a 4.8 σ point-like source located at ～10 kpc to the northwest of the M31 disk, with a luminosity of(0.97 ± 0.27) × 1038 erg s-1 and a pho@ton-$i·nd3 ex of 2.31 ± 0.18. Lacking a counterpart on the southeast side of the disk, the relation between this point-like source and a bubble-like structure remains elusive.
文摘The frequent detection of binary mergers of^30 M⊙black holes(BHs)by the Laser Interferometer Gravitational-Wave Observatory(LIGO)rekindled researchers’interest in primordial BHs(PBHs)being dark matter(DM).In this work,we investigated PBHs distributed as DM with a monochromatic mass of 30 M⊙and examined the encounter-capture scenario of binary formation,where the densest central region of DM halo dominates.Thus,we paid special attention to the tidal effect by the supermassive black hole(SMBH)present.In doing so,we discovered a necessary tool called loss zone that complements the usage of loss cone.We found that the tidal effect is not prominent in affecting binary formation,which also turned out to be insufficient in explaining the totality of LIGO’s event rate estimation,especially due to a microlensing event constraining the DM fraction in PBH at the mass of interest from near unity to an order smaller.Meanwhile,an early-universe binary formation scenario proves so prevailing that the LIGO signal in turn constrains the PBH fraction below one percent.Thus,people should put more faith in alternative PBH windows and other DM candidates.
基金supported by grant from Department of Education of LaoningProvincia1(No.2008S232)
文摘Objective： It is known that chronic hepatitis B virus （HBV） infection is a main risk factor for hepatocellular carcinoma （HCC）. To assess the effect of HBV infection and its interaction with other factors on the risk for HCC, a hospital-based case-control study was carried out in Northeast China. Methods： A total of 384 cases with hepatocellular carcinoma and 432 controls without evidence of liver diseases were enrolled in the study. Blood samples were collected to detect the serum markers of hepatitis B virus （HBV） and hepatitis C virus （HCV） and questionnaires about lifestyle and family tumor history were performed in all subjects. Results： The total infection rate of HBV in hepatocellular carcinoma cases was 70.8% and 10.0% in non-liver disease controls. There was a statistically significant difference （P〈0.0001） between cases and controls （OR= 22.0; 95%CI：15.0-32.3）. Interaction analysis indicated that in HBV chronic carriers with HCV infection or alcohol consumption or family HCC history, the risk for HCC increased （OR=41.1, 95%CI： 20.2-83.9, OR=125.0, 95%CI： 66.5-235.2; OR=56.9, 95%CI： 27.2-119.3 respectively）. In addition, hepatitis B history, HCV infection, hepatic cirrhosis and family history of HCC were also potential HCC independent risk factors. Conclusion： We confirmed that HBV is a chief risk factor for hepatocellular carcinoma and accounts for 67.7% of all hepatocellular carcinoma in Northeast China. HCV infection, alcohol intake and family history could enhance the risk for HCC in chronic HBV carriers.
