To elucidate the genetic characterization and molecular epidemiological features of Echovirus 19 (El9) isolates collected from an outbreak associated with hand, foot and mouth disease (HFMD) in Tai'an city of Sha...To elucidate the genetic characterization and molecular epidemiological features of Echovirus 19 (El9) isolates collected from an outbreak associated with hand, foot and mouth disease (HFMD) in Tai'an city of Shandong Province of China from July to September, 2003. Methods Thirty seven Echovirus 19 isolates were isolated from stool specimens and throat swabs collected during the outbreak, then major capsid (VP1) genomic sequence was determined, and phylogenetic tree was done based on the VP1 sequences among these 37 and other El9 viruses deposited in the Genbank. Also a representative strain named CHN-SD03-TN12 was selected for sequencing of 5′-untranslated regions (5′-UTR). Results The identity rate was about 98.9%-100% among all these 37 El9 viruses. The genetic relationships between these 37 El9 isolates and other strains reported were also depicted. The identity rate was about 78.4%-78.9% compared with El9 reference strain Burke. The substitutions in the sequence of 5′-UTR resulted in changes in the conjectural properties of 5′-UTR of El9 viruses. Condusion The genetic features of El9 viruses isolated during the outbreak in Shandong Province in 2003 may be associated with a genetic and antigenic drift that changes the virulence of the Shandong isolates, but the molecular changes in Shandong El9 viruses contributing to their phenotype remain to be further illuminated. However, the sequences described in this paper substantiate the changes taken place in capsid VPI and 5′UTR regions. These substitutions may contribute to their tropism and virulence, and play a significant role in pathogenesis and clinical manifestations of the disease.展开更多
AIM:To investigate the correlation between interleukin-18(IL-18) gene polymorphisms and the risk of developing Crohn's disease(CD).METHODS:The PubMed,CISCOM,CINAHL,Web of Science,EBSCO,Cochrane Library,MEDLINE,EMB...AIM:To investigate the correlation between interleukin-18(IL-18) gene polymorphisms and the risk of developing Crohn's disease(CD).METHODS:The PubMed,CISCOM,CINAHL,Web of Science,EBSCO,Cochrane Library,MEDLINE,EMBASE and CBM databases were searched without any language restrictions using combinations of keywords relating to CD and IL-18 for relevant articles published before November 1st,2013.Screening of the published studies retrieved from searches was based on our stringent inclusion and exclusion criteria and resulted in seven eligible studies for meta-analysis.A metaanalysis was conducted using a random-effects model with STATA 12.0 software.Crude odds ratios(ORs) with95%confidence intervals(95%CI) were calculated.RESULTS:Seven case-control studies,with a total of1930 CD cases and 1930 healthy subjects,met our inclusion criteria.The results of our meta-analysis indicated that the IL-18 rs1946518 A>C and rs187238G>C polymorphisms may correlate with an increased risk of CD under five genetic models(all P < 0.05).Furthermore,we observed positive associations between the IL-18 rs360718 A>C polymorphism and CD risk under three genetic models(C allele vs A allele:OR = 2.03,95%CI:1.20-3.43,P = 0.008;CC vs AA+AC:OR = 2.39,95%CI:1.2-4.43,P = 0.006;CC vs AC:OR = 2.31,95%CI:1.22-4.38,P = 0.010).However,such associations were not found for the IL-18 rs917997 C>T,codon 35 A>C and rs1946519G>T polymorphisms(all P> 0.05).A subgroup analysis was conducted to investigate the effect of ethnicity on an individual's susceptibility to CD.Our results revealed positive correlations between IL-18 genetic polymorphisms and an increased risk of CD among Asians and Africans(all P < 0.05),but not among Caucasians(all P> 0.05).CONCLUSION:This meta-analysis indicated that the IL-18 rs1946518 A> C,rs187238 G>C and rs360718A>C polymorphisms may contribute to susceptibility to CD,especially among Asians and Africans.These polymorphisms are known to reduce IL-18 mRNA and protein levels.展开更多
To produce the monoclonal antibodies (mAbs) against hygromycin B phosphotransferase (HPT) and to develop immunoassay based on mAbs for biosafety assessment of HPT in genetically modified rice (GM rice). Methods ...To produce the monoclonal antibodies (mAbs) against hygromycin B phosphotransferase (HPT) and to develop immunoassay based on mAbs for biosafety assessment of HPT in genetically modified rice (GM rice). Methods BALB/c mice were immunized with purified recombinant 6His. HPT protein, and the conventional hybridoma technology was used to generate the monoclonal hybridoma cells. ELISA and Western blot were used to analyze the specificity of mAbs recognizing HPT and the cross reaction with other proteins. A double-Ab sandwich ELISA method was established to detect HPT expression level in the sck gene-modified rice plants. Results Four hybridomas, named F1,D4-2, D4-4, and D4-5, producing the mAbs against HPT were successfully obtained with the titer of ascetic mAbs ranging from 10×10^-4 to10×10^-5. Identification of subclass showed that all the produced mAbs belonged to IgG1. Western blot showed specific binding reaction between the mAbs to the HPT proteins expressed in the GM rice. A double sandwich ELISA coated with anti-HPT polyclonal antibody was established with mAbs as sandwich antibody, which showed a sensitivity of 30ng/mL and did not crossreact with other proteins. The expression level of HPT in the leaves of sck-transformed lines was detected (80-150ng/mL). But HPT protein in the grain and seed of GM rice could not be detected using this ELISA assay, Conclusion Anti-HPT mAbs prepared herein have a high specificity and can be used for rapid assay of HPT antigen. The expression level of HPT in the GM rice grain and seed is lower than our ELISA detection limit.展开更多
AIM:To detect the expression of huCdc7 in colorectal cancer.METHODS:The mRNA and protein expression of huCdc7 in 39 colorectal cancer tissue specimens and matched tumor-adjacent normal colorectal tissue specimens was ...AIM:To detect the expression of huCdc7 in colorectal cancer.METHODS:The mRNA and protein expression of huCdc7 in 39 colorectal cancer tissue specimens and matched tumor-adjacent normal colorectal tissue specimens was detected by reverse transcription-polymerase chain reaction and immunohistochemistry,respectively.RESULTS:The relative expression level of huCdc7 mRNA in colorectal cancer was significantly higher than that in tumor-adjacent normal colorectal tissues(0.03675 ± 1.00 vs 0.01199 ± 0.44,P < 0.05).huCdc7-positive cells displayed brown granules in the nucleus.Tumor tissues contained many huCdc7-positive cells,whereas normal colorectal tissues contained very few positive cells.CONCLUSION:huCdc7 may play an important role in the development and progression of colorectal cancer.展开更多
To detect the presence of endothelial injury in patients with severe acute respiratory syndrome (SARS) via enhanced levels of tissue-type plasminogen activator (t-PA) and soluble thrombomodulin (sTM). Methods Ca...To detect the presence of endothelial injury in patients with severe acute respiratory syndrome (SARS) via enhanced levels of tissue-type plasminogen activator (t-PA) and soluble thrombomodulin (sTM). Methods Case patients were from Xuanwu Hospital (Capital University of Medical Sciences, Beijing, China), and all of them met clinical criteria for SARS. Healthy controls were some of the hospital employees. Endothelial injury bio-markers tPA and sTM were detected by commercial ELISA-methods. Results Classic plasma markers of endothelial injury, tPA and sTM significantly elevated in SARS patients in comparison to controls [t-PA: 1.48±0.16 nmol/L versus 0.25±0.03 nmol/L (P〈0.0001), and sTM: 0.26±0.06 nmol/L versus 0.14±0.02 nmol/L (P〈0.05)]. The only patient who died had extremely high levels of these endothelial injury markers (t-PA: 2.77 nmol/L and sTM: 1.01 nmol/L). The likelihood ratio analysis indicated the excellent discriminating power for SARS at the optimal cut-point of 0.49 nmol/L for tPA and 0.20 nmol/L for sTM, respectively. Significant numerical correlations were found among these endothelial injury markers in SARS patients. The numerical coefficient of correlation Pearson r between t-PA and sTM was 0.5867 (P〈0.05). Conclusion Increased plasma concentrations of tPA and sTM in patients with SARS suggest the possibility of endothelial injury. SARS patients might need anticoagulant therapy or fibrinolytic therapy in order to reverse intraalveolar coagulation, microthrombi formation, alveolar and interstitial fibrin deposition. It may not only provide a useful treatment and prognostic index but also allow a further understanding of the pathological condition of the disease.展开更多
Two-dimensional(2D)semiconductors isoelectronic to phosphorene have been drawing much attention recently due to their promising applications for next-generation(opt)electronics.This family of 2D materials contains mor...Two-dimensional(2D)semiconductors isoelectronic to phosphorene have been drawing much attention recently due to their promising applications for next-generation(opt)electronics.This family of 2D materials contains more than 400members,including(a)elemental group-V materials,(b)binary III–VII and IV–VI compounds,(c)ternary III–VI–VII and IV–V–VII compounds,making materials design with targeted functionality unprecedentedly rich and extremely challenging.To shed light on rational functionality design with this family of materials,we systemically explore their fundamental band gaps and alignments using hybrid density functional theory(DFT)in combination with machine learning.First,calculations are performed using both the Perdew–Burke–Ernzerhof exchange–correlation functional within the generalgradient-density approximation(GGA-PBE)and Heyd–Scuseria–Ernzerhof hybrid functional(HSE)as a reference.We find this family of materials share similar crystalline structures,but possess largely distributed band-gap values ranging approximately from 0 eV to 8 eV.Then,we apply machine learning methods,including linear regression(LR),random forest regression(RFR),and support vector machine regression(SVR),to build models for the prediction of electronic properties.Among these models,SVR is found to have the best performance,yielding the root mean square error(RMSE)less than 0.15 eV for the predicted band gaps,valence-band maximums(VBMs),and conduction-band minimums(CBMs)when both PBE results and elemental information are used as features.Thus,we demonstrate that the machine learning models are universally suitable for screening 2D isoelectronic systems with targeted functionality,and especially valuable for the design of alloys and heterogeneous systems.展开更多
YbMnBi2 is a recently discovered time-reversal-symmetry breaking type-Ⅱ Weyl semimetal.However, as a representation of the new category of topological matters, the scanning tunneling microcopy(STM) results on such im...YbMnBi2 is a recently discovered time-reversal-symmetry breaking type-Ⅱ Weyl semimetal.However, as a representation of the new category of topological matters, the scanning tunneling microcopy(STM) results on such important material are still absent.Here, we report the STM investigations on the morphology of vacuum cleaved single crystalline YbMnBi2 samples.A hill and valley type of topography is observed on the YbMnBi2 surface, which is consistent with the non-layer nature of its crystal structure.Analysis of STM images yields the information of the index of the vicinal surface.Our results here lay a playground of future atomic scale research on YbMnBi2.展开更多
Isotopic fractionation is the basis of tracing the water cycle using hydrogen and oxygen isotopes. Isotopic fractionation factors in water evaporating from free water bodies are mainly affected by temperature and rela...Isotopic fractionation is the basis of tracing the water cycle using hydrogen and oxygen isotopes. Isotopic fractionation factors in water evaporating from free water bodies are mainly affected by temperature and relative humidity, and vary significantly with these atmospheric factors over the course of a day. The evaporation rate (E) can reveal the effects of atmospheric factors. Therefore, there should be a certain functional relationship between isotopic fractionation factors and E. An average isotopic fractionation factor ( t~* ) was defined to describe isotopic differences between vapor and liquid phases in evaporation with time intervals of days. The relationship between or* and E based on the isotopic mass balance was investigated through an evaporation pan experiment with no inflow. The experimental results showed that the isotopic compositions of residual water were more enriched with time; tr* was affected by air temperature, relative humidity, and other atmospheric factors, and had a strong functional relation with E. The values of 0~* can be easily calculated with the known values of E, the initial volume of water in the pan, and isotopic compositions of residual water.展开更多
Using ab initio density functional theory calculations, we explore the three most stable structural phases, namely, α,β, and cubic(c) phases, of two-dimensional(2D) antimonene, as well as its isoelectronic counterpa...Using ab initio density functional theory calculations, we explore the three most stable structural phases, namely, α,β, and cubic(c) phases, of two-dimensional(2D) antimonene, as well as its isoelectronic counterparts SnTe and InI. We find that the band gap increases monotonically from Sb to SnTe to InI along with an increase in ionicity, independent of the structural phases. The band gaps of this material family cover the entire visible-light energy spectrum, ranging from 0.26 eV to 3.37 eV, rendering them promising candidates for optoelectronic applications. Meanwhile, band-edge positions of these materials are explored and all three types of band alignments can be achieved through properly combining antimonene with its isoelectronic counterparts to form heterostructures. The richness in electronic properties for this isoelectronic material family sheds light on possibilities to tailor the fundamental band gap of antimonene via lateral alloying or forming vertical heterostructures.展开更多
To obtain HPT protein (Hygromycin B Phosphotransferase), a kind of plant selective maker gene product expressed from E.coli and to prepare the polyclonal antibody (pAbs) against it. Methods HPT cDNA fragment was ob...To obtain HPT protein (Hygromycin B Phosphotransferase), a kind of plant selective maker gene product expressed from E.coli and to prepare the polyclonal antibody (pAbs) against it. Methods HPT cDNA fragment was obtained by PCR and was inserted into the prokaryotic expressing vector pBV222. Then the constructed recombinant plasmid pBV222-HPT was transfered into E.coli DH5?for HPT expression. The recombinant expressing system was confirmed by restriction endonuclease digestion, DNA sequencing and protein expression. E.coli cells were lysed by sonication and detergent dissolution. After cell membrane was extracted, the inclusion bodies were denatured by 8 mol/L Urea and purified with metal chelate affinity chromatography on Ni-NTA agarose under denaturing condition. The purified 6His-HPT was characterized by SDS-PAGE, and used to immunize rabbit. The titer and specificity of antisera were detected by ELISA and Western blot respecitively. Results Analysis of DNA sequence and restricted enzymes showed that the sequence of PBV222-HPT plasmid was correct. The amount of recombinant HPT expressed in E.coli accounted for 30% of total cellular proteins. From 1 liter of fermentative bacteria about 22 milligrams of pure recombinant HPT was isolated with purity above 95%. The recombinant HPT protein could produce high titer antiserum in rabbits and show good immunity activity. Western blot showed specific binding reaction between the antiserum to the purified 6His-HPT protein and their expressed products (plants protein and bacterial protein). Conclusion HPT protein can be expressed and purified from E.coli by a relatively simple method, which has high immunity activity.展开更多
Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2(0001)are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic(fee)str...Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2(0001)are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic(fee)structure of Sn surface is obtained.Superconductivity is also detected on the fcc-Sn(111)surface,and the size of superconducting gap on the Sn surface is nearly the same as that on the superconducting substrate.Furthermore,phase transition occurs from fcc-Sn(111)toβ-Sn(001)by keeping the sample at room temperature for a certain time.Due to the strain relaxation on theβ-Sn islands,both the in-plane unit cell and out-of-plane structures distort,and the height of surface atoms varies periodically to form a universal ripple structure.展开更多
Introduction:A retrospective study based on sentinel surveillance was conducted in 10 provinciallevel administrative divisions(PLADs)in China to enhance the understanding of the epidemiological characteristics of huma...Introduction:A retrospective study based on sentinel surveillance was conducted in 10 provinciallevel administrative divisions(PLADs)in China to enhance the understanding of the epidemiological characteristics of human parainfluenza viruses(HPIVs).Methods:From January 2019 to June 2023,respiratory specimens were collected from individuals with acute respiratory infections(ARIs)and screened for four HPIVs serotypes and other common respiratory viruses using multiplex real-time polymerase chain reaction(PCR).This study analyzed the association of HPIVs infections with seasonal patterns,geographical distribution,demographic profiles,clinical features,and co-infection status.Results:During the study period,a total of 12,866 ARIs were included.The overall detection rate of HPIVs was 6.15%,varying from 5.04%in 2022 to 9.70%in 2020.The median age of HPIVs-infected patients was 3 years.HPIV2 was more prevalent among individuals aged 5–17 years(42.57%),while HPIV4 was more common in those over 65 years(12.24%).HPIV3(54.16%)and HPIV1(27.18%)were the predominant serotypes,and their prevalence exhibited significant seasonal fluctuations postcoronavirus disease 2019(COVID-19)pandemic.The peak of HPIV3 shifted three months later in 2020 compared to 2019 and returned to a summer peak thereafter.Two peaks of HPIV1 were observed in 2021 following the peak of HPIV3.Additionally,coinfections were frequent in HPIVs cases(overall rate:22.12%),with human rhinovirus being the most common co-infecting virus.Conclusions:The prevalence of HPIVs in China was predominantly due to HPIV3 and HPIV1,and their seasonal patterns were altered by pandemic restrictions.Hence,continuous surveillance of HPIVs is essential.展开更多
基金This work was supported by Chinese Center for Disease Control and Prevention and Ministry of Health,China.
文摘To elucidate the genetic characterization and molecular epidemiological features of Echovirus 19 (El9) isolates collected from an outbreak associated with hand, foot and mouth disease (HFMD) in Tai'an city of Shandong Province of China from July to September, 2003. Methods Thirty seven Echovirus 19 isolates were isolated from stool specimens and throat swabs collected during the outbreak, then major capsid (VP1) genomic sequence was determined, and phylogenetic tree was done based on the VP1 sequences among these 37 and other El9 viruses deposited in the Genbank. Also a representative strain named CHN-SD03-TN12 was selected for sequencing of 5′-untranslated regions (5′-UTR). Results The identity rate was about 98.9%-100% among all these 37 El9 viruses. The genetic relationships between these 37 El9 isolates and other strains reported were also depicted. The identity rate was about 78.4%-78.9% compared with El9 reference strain Burke. The substitutions in the sequence of 5′-UTR resulted in changes in the conjectural properties of 5′-UTR of El9 viruses. Condusion The genetic features of El9 viruses isolated during the outbreak in Shandong Province in 2003 may be associated with a genetic and antigenic drift that changes the virulence of the Shandong isolates, but the molecular changes in Shandong El9 viruses contributing to their phenotype remain to be further illuminated. However, the sequences described in this paper substantiate the changes taken place in capsid VPI and 5′UTR regions. These substitutions may contribute to their tropism and virulence, and play a significant role in pathogenesis and clinical manifestations of the disease.
文摘AIM:To investigate the correlation between interleukin-18(IL-18) gene polymorphisms and the risk of developing Crohn's disease(CD).METHODS:The PubMed,CISCOM,CINAHL,Web of Science,EBSCO,Cochrane Library,MEDLINE,EMBASE and CBM databases were searched without any language restrictions using combinations of keywords relating to CD and IL-18 for relevant articles published before November 1st,2013.Screening of the published studies retrieved from searches was based on our stringent inclusion and exclusion criteria and resulted in seven eligible studies for meta-analysis.A metaanalysis was conducted using a random-effects model with STATA 12.0 software.Crude odds ratios(ORs) with95%confidence intervals(95%CI) were calculated.RESULTS:Seven case-control studies,with a total of1930 CD cases and 1930 healthy subjects,met our inclusion criteria.The results of our meta-analysis indicated that the IL-18 rs1946518 A>C and rs187238G>C polymorphisms may correlate with an increased risk of CD under five genetic models(all P < 0.05).Furthermore,we observed positive associations between the IL-18 rs360718 A>C polymorphism and CD risk under three genetic models(C allele vs A allele:OR = 2.03,95%CI:1.20-3.43,P = 0.008;CC vs AA+AC:OR = 2.39,95%CI:1.2-4.43,P = 0.006;CC vs AC:OR = 2.31,95%CI:1.22-4.38,P = 0.010).However,such associations were not found for the IL-18 rs917997 C>T,codon 35 A>C and rs1946519G>T polymorphisms(all P> 0.05).A subgroup analysis was conducted to investigate the effect of ethnicity on an individual's susceptibility to CD.Our results revealed positive correlations between IL-18 genetic polymorphisms and an increased risk of CD among Asians and Africans(all P < 0.05),but not among Caucasians(all P> 0.05).CONCLUSION:This meta-analysis indicated that the IL-18 rs1946518 A> C,rs187238 G>C and rs360718A>C polymorphisms may contribute to susceptibility to CD,especially among Asians and Africans.These polymorphisms are known to reduce IL-18 mRNA and protein levels.
基金This work was supported by 973 National Fundamental Science Program Funds (2001CB109007 and 2001CB10901)and 863 National High-Tech Program Funds (2004AA212221 and 2002AA212041).
文摘To produce the monoclonal antibodies (mAbs) against hygromycin B phosphotransferase (HPT) and to develop immunoassay based on mAbs for biosafety assessment of HPT in genetically modified rice (GM rice). Methods BALB/c mice were immunized with purified recombinant 6His. HPT protein, and the conventional hybridoma technology was used to generate the monoclonal hybridoma cells. ELISA and Western blot were used to analyze the specificity of mAbs recognizing HPT and the cross reaction with other proteins. A double-Ab sandwich ELISA method was established to detect HPT expression level in the sck gene-modified rice plants. Results Four hybridomas, named F1,D4-2, D4-4, and D4-5, producing the mAbs against HPT were successfully obtained with the titer of ascetic mAbs ranging from 10×10^-4 to10×10^-5. Identification of subclass showed that all the produced mAbs belonged to IgG1. Western blot showed specific binding reaction between the mAbs to the HPT proteins expressed in the GM rice. A double sandwich ELISA coated with anti-HPT polyclonal antibody was established with mAbs as sandwich antibody, which showed a sensitivity of 30ng/mL and did not crossreact with other proteins. The expression level of HPT in the leaves of sck-transformed lines was detected (80-150ng/mL). But HPT protein in the grain and seed of GM rice could not be detected using this ELISA assay, Conclusion Anti-HPT mAbs prepared herein have a high specificity and can be used for rapid assay of HPT antigen. The expression level of HPT in the GM rice grain and seed is lower than our ELISA detection limit.
文摘AIM:To detect the expression of huCdc7 in colorectal cancer.METHODS:The mRNA and protein expression of huCdc7 in 39 colorectal cancer tissue specimens and matched tumor-adjacent normal colorectal tissue specimens was detected by reverse transcription-polymerase chain reaction and immunohistochemistry,respectively.RESULTS:The relative expression level of huCdc7 mRNA in colorectal cancer was significantly higher than that in tumor-adjacent normal colorectal tissues(0.03675 ± 1.00 vs 0.01199 ± 0.44,P < 0.05).huCdc7-positive cells displayed brown granules in the nucleus.Tumor tissues contained many huCdc7-positive cells,whereas normal colorectal tissues contained very few positive cells.CONCLUSION:huCdc7 may play an important role in the development and progression of colorectal cancer.
文摘To detect the presence of endothelial injury in patients with severe acute respiratory syndrome (SARS) via enhanced levels of tissue-type plasminogen activator (t-PA) and soluble thrombomodulin (sTM). Methods Case patients were from Xuanwu Hospital (Capital University of Medical Sciences, Beijing, China), and all of them met clinical criteria for SARS. Healthy controls were some of the hospital employees. Endothelial injury bio-markers tPA and sTM were detected by commercial ELISA-methods. Results Classic plasma markers of endothelial injury, tPA and sTM significantly elevated in SARS patients in comparison to controls [t-PA: 1.48±0.16 nmol/L versus 0.25±0.03 nmol/L (P〈0.0001), and sTM: 0.26±0.06 nmol/L versus 0.14±0.02 nmol/L (P〈0.05)]. The only patient who died had extremely high levels of these endothelial injury markers (t-PA: 2.77 nmol/L and sTM: 1.01 nmol/L). The likelihood ratio analysis indicated the excellent discriminating power for SARS at the optimal cut-point of 0.49 nmol/L for tPA and 0.20 nmol/L for sTM, respectively. Significant numerical correlations were found among these endothelial injury markers in SARS patients. The numerical coefficient of correlation Pearson r between t-PA and sTM was 0.5867 (P〈0.05). Conclusion Increased plasma concentrations of tPA and sTM in patients with SARS suggest the possibility of endothelial injury. SARS patients might need anticoagulant therapy or fibrinolytic therapy in order to reverse intraalveolar coagulation, microthrombi formation, alveolar and interstitial fibrin deposition. It may not only provide a useful treatment and prognostic index but also allow a further understanding of the pathological condition of the disease.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0206301)。
文摘Two-dimensional(2D)semiconductors isoelectronic to phosphorene have been drawing much attention recently due to their promising applications for next-generation(opt)electronics.This family of 2D materials contains more than 400members,including(a)elemental group-V materials,(b)binary III–VII and IV–VI compounds,(c)ternary III–VI–VII and IV–V–VII compounds,making materials design with targeted functionality unprecedentedly rich and extremely challenging.To shed light on rational functionality design with this family of materials,we systemically explore their fundamental band gaps and alignments using hybrid density functional theory(DFT)in combination with machine learning.First,calculations are performed using both the Perdew–Burke–Ernzerhof exchange–correlation functional within the generalgradient-density approximation(GGA-PBE)and Heyd–Scuseria–Ernzerhof hybrid functional(HSE)as a reference.We find this family of materials share similar crystalline structures,but possess largely distributed band-gap values ranging approximately from 0 eV to 8 eV.Then,we apply machine learning methods,including linear regression(LR),random forest regression(RFR),and support vector machine regression(SVR),to build models for the prediction of electronic properties.Among these models,SVR is found to have the best performance,yielding the root mean square error(RMSE)less than 0.15 eV for the predicted band gaps,valence-band maximums(VBMs),and conduction-band minimums(CBMs)when both PBE results and elemental information are used as features.Thus,we demonstrate that the machine learning models are universally suitable for screening 2D isoelectronic systems with targeted functionality,and especially valuable for the design of alloys and heterogeneous systems.
基金Project supported by the “Shuguang Program” from Shanghai Education Development Foundation and Shanghai Municipal Education Commission,Ministry of Science and Technology of China(Grant Nos.2016YFA0301003 and 2016YFA0300403)the National Natural Science Foundation of China(Grant Nos.11521404,11634009,11874256,11574202,11874258,11790313,11674226,U1632102,11674222,and 11861161003)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)
文摘YbMnBi2 is a recently discovered time-reversal-symmetry breaking type-Ⅱ Weyl semimetal.However, as a representation of the new category of topological matters, the scanning tunneling microcopy(STM) results on such important material are still absent.Here, we report the STM investigations on the morphology of vacuum cleaved single crystalline YbMnBi2 samples.A hill and valley type of topography is observed on the YbMnBi2 surface, which is consistent with the non-layer nature of its crystal structure.Analysis of STM images yields the information of the index of the vicinal surface.Our results here lay a playground of future atomic scale research on YbMnBi2.
基金supported by the National Natural Science Foundation of China (Grants No.50679024,40901015,and 41001011)the Fundamental Research Funds for the Central Universities (Grants No.B1020072 and B1020062)+2 种基金the Ph. D. Programs Foundation of the Ministry of Education of China (Grant No.20090094120008)the Special Fund of the State Key Laboratory of China (Grant No.2009586412)the Science Foundation of the HydroChina Chengdu Engineering Corporation (Grant No.P058)
文摘Isotopic fractionation is the basis of tracing the water cycle using hydrogen and oxygen isotopes. Isotopic fractionation factors in water evaporating from free water bodies are mainly affected by temperature and relative humidity, and vary significantly with these atmospheric factors over the course of a day. The evaporation rate (E) can reveal the effects of atmospheric factors. Therefore, there should be a certain functional relationship between isotopic fractionation factors and E. An average isotopic fractionation factor ( t~* ) was defined to describe isotopic differences between vapor and liquid phases in evaporation with time intervals of days. The relationship between or* and E based on the isotopic mass balance was investigated through an evaporation pan experiment with no inflow. The experimental results showed that the isotopic compositions of residual water were more enriched with time; tr* was affected by air temperature, relative humidity, and other atmospheric factors, and had a strong functional relation with E. The values of 0~* can be easily calculated with the known values of E, the initial volume of water in the pan, and isotopic compositions of residual water.
基金Project supported by the National Natural Science Foundation of China(Grant No.51702146)the College Students’Innovation and Entrepreneurship Projects,China(Grant No.201710148000072)Liaoning Province Doctor Startup Fund,China(Grant No.201601325)。
文摘Using ab initio density functional theory calculations, we explore the three most stable structural phases, namely, α,β, and cubic(c) phases, of two-dimensional(2D) antimonene, as well as its isoelectronic counterparts SnTe and InI. We find that the band gap increases monotonically from Sb to SnTe to InI along with an increase in ionicity, independent of the structural phases. The band gaps of this material family cover the entire visible-light energy spectrum, ranging from 0.26 eV to 3.37 eV, rendering them promising candidates for optoelectronic applications. Meanwhile, band-edge positions of these materials are explored and all three types of band alignments can be achieved through properly combining antimonene with its isoelectronic counterparts to form heterostructures. The richness in electronic properties for this isoelectronic material family sheds light on possibilities to tailor the fundamental band gap of antimonene via lateral alloying or forming vertical heterostructures.
基金?73"Programme Funds(2001CB109001 and 2001CB109007)"863"Programme Funds(2001AA212041,2001AA212291,and 2002AA212041).
文摘To obtain HPT protein (Hygromycin B Phosphotransferase), a kind of plant selective maker gene product expressed from E.coli and to prepare the polyclonal antibody (pAbs) against it. Methods HPT cDNA fragment was obtained by PCR and was inserted into the prokaryotic expressing vector pBV222. Then the constructed recombinant plasmid pBV222-HPT was transfered into E.coli DH5?for HPT expression. The recombinant expressing system was confirmed by restriction endonuclease digestion, DNA sequencing and protein expression. E.coli cells were lysed by sonication and detergent dissolution. After cell membrane was extracted, the inclusion bodies were denatured by 8 mol/L Urea and purified with metal chelate affinity chromatography on Ni-NTA agarose under denaturing condition. The purified 6His-HPT was characterized by SDS-PAGE, and used to immunize rabbit. The titer and specificity of antisera were detected by ELISA and Western blot respecitively. Results Analysis of DNA sequence and restricted enzymes showed that the sequence of PBV222-HPT plasmid was correct. The amount of recombinant HPT expressed in E.coli accounted for 30% of total cellular proteins. From 1 liter of fermentative bacteria about 22 milligrams of pure recombinant HPT was isolated with purity above 95%. The recombinant HPT protein could produce high titer antiserum in rabbits and show good immunity activity. Western blot showed specific binding reaction between the antiserum to the purified 6His-HPT protein and their expressed products (plants protein and bacterial protein). Conclusion HPT protein can be expressed and purified from E.coli by a relatively simple method, which has high immunity activity.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0301003 and 2016YFA0300403the National Natural Science Foundation of China under Grant Nos 11521404,11634009,U1632102,11504230,11674222,11574202,11674226,11574201 and U1632272
文摘Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2(0001)are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic(fee)structure of Sn surface is obtained.Superconductivity is also detected on the fcc-Sn(111)surface,and the size of superconducting gap on the Sn surface is nearly the same as that on the superconducting substrate.Furthermore,phase transition occurs from fcc-Sn(111)toβ-Sn(001)by keeping the sample at room temperature for a certain time.Due to the strain relaxation on theβ-Sn islands,both the in-plane unit cell and out-of-plane structures distort,and the height of surface atoms varies periodically to form a universal ripple structure.
基金Supported by the National Health Commission Major Public Health Project(ZDGW21-131031103000180005).
文摘Introduction:A retrospective study based on sentinel surveillance was conducted in 10 provinciallevel administrative divisions(PLADs)in China to enhance the understanding of the epidemiological characteristics of human parainfluenza viruses(HPIVs).Methods:From January 2019 to June 2023,respiratory specimens were collected from individuals with acute respiratory infections(ARIs)and screened for four HPIVs serotypes and other common respiratory viruses using multiplex real-time polymerase chain reaction(PCR).This study analyzed the association of HPIVs infections with seasonal patterns,geographical distribution,demographic profiles,clinical features,and co-infection status.Results:During the study period,a total of 12,866 ARIs were included.The overall detection rate of HPIVs was 6.15%,varying from 5.04%in 2022 to 9.70%in 2020.The median age of HPIVs-infected patients was 3 years.HPIV2 was more prevalent among individuals aged 5–17 years(42.57%),while HPIV4 was more common in those over 65 years(12.24%).HPIV3(54.16%)and HPIV1(27.18%)were the predominant serotypes,and their prevalence exhibited significant seasonal fluctuations postcoronavirus disease 2019(COVID-19)pandemic.The peak of HPIV3 shifted three months later in 2020 compared to 2019 and returned to a summer peak thereafter.Two peaks of HPIV1 were observed in 2021 following the peak of HPIV3.Additionally,coinfections were frequent in HPIVs cases(overall rate:22.12%),with human rhinovirus being the most common co-infecting virus.Conclusions:The prevalence of HPIVs in China was predominantly due to HPIV3 and HPIV1,and their seasonal patterns were altered by pandemic restrictions.Hence,continuous surveillance of HPIVs is essential.