Penta-twinned Ag nanowires（pt-AgNWs） have recently attracted much attention due to their interesting mechanical and physical properties. Here we perform largescale atomistic simulations to investigate the influence ...Penta-twinned Ag nanowires（pt-AgNWs） have recently attracted much attention due to their interesting mechanical and physical properties. Here we perform largescale atomistic simulations to investigate the influence of sample size and strain rate on the tensile strength of pt-AgNWs. The simulation results show an apparent size effect in that the nanowire strength（defined as the critical stress for dislocation nucleation） increases with decreasing wire diameter. To account for such size effect, a theoretical model involving the interaction between an emerging dislocation and the twin boundary has been developed for the surface nucleation of dislocations. It is shown that the model predictions are in quantitative agreement with the results from atomistic simulations and previous experimental studies in the literatures. The simulations also reveal that nanowire strength is strain-rate dependent, which predicts an activation volume for dislocation nucleation in the range of 1–10b^3,where b is the magnitude of the Burgers vector for a full dislocation.展开更多
Most of traditional linear poly(ethylene terephthalate)(PET)resins of relatively low molecular mass and narrow molecular mass distribution have low melt strength at foaming temperatures,which are not enough to support...Most of traditional linear poly(ethylene terephthalate)(PET)resins of relatively low molecular mass and narrow molecular mass distribution have low melt strength at foaming temperatures,which are not enough to support and keep cells.An in-situ polymerization-modification process with esterification and polycondensation stages was performed in a 2 L batch stirred reactor using pyromellitic dianhydride(PMDA)or pentaerythritol(PENTA)as modifying monomers to obtain PETs with high melt strength.The influence of amounts of modifying monomers on the properties of modified PET was investigated.It was found that the selected modifying monomers could effectively introduce branched structures into the modified PETs and improve their melt strength.With increasing the amount of the modifying monomer,the melt strength of the modified PET increased.But when the amount of PENTA reached 0.35%or PMDA reached 0.9%,crosslinking phenomenon was observed in the modified PET.Supercritical carbon dioxide(ScCO2)was employed as physical foaming agent to evaluate the foaming ability of modified PETs.The modified PETs had good foaming properties at 14 MPa of CO2pressure with foaming temperature ranging from 265°C to 280°C.SEM micrographs demonstrated that both modified PET foams had homogeneous cellular structures,with cell diameter ranging from 35μm to 49μm for PENTA modified PETs and38μm to 57μm for PMDA modified ones.Correspondingly,the cell density had a range of 3.5×107cells·cm 3to 7×106cells·cm 3for the former and 2.8×107cells·cm 3to 5.8×106cells·cm 3for the latter.展开更多
In continuous speech, the pitch contour of the same syllable may vary much due to its contextual information. The Parallel Encoding and Target Approximation （PENTA） model is applied here to Mandarin speech synthesis...In continuous speech, the pitch contour of the same syllable may vary much due to its contextual information. The Parallel Encoding and Target Approximation （PENTA） model is applied here to Mandarin speech synthesis with a method to predict pitch contours for Chinese syllables with different contexts by combining the Classification And Regression Tree （CART） with the PENTA model to improve its prediction accuracy. CART was first used to cluster the syllables＇ normalized pitch contours according to the syllables contextual information and the distances between pitch contours. The average pitch contour was used to train the PENTA model with the average contour for each cluster. The initial pitch is required with the PENTA model to predict a continuous pitch contour. A Pitch Discontinuity Model （PDM） was used to predict the initial pitches at positions with voiceless consonants and prosodic boundaries. Initial tests on a Chinese four-syllable word corpus containing 2048 words were extended to tests with a continuous speech corpus containing 5445 sentences. The results are satisfactory in terms of the Root Mean Square Error （RMSE） comparing the predicted pitch contour with the original contour. This method can model pitch contours for Mandarin sentences with any text for speech synthesis.展开更多
目的:研究天津汉族群体21号染色体上D21S11、D21S1440和Penta D 3个短串联重复序列(STR)基因座遗传多态性,为唐氏综合征(DS)基因诊断和产前基因诊断提供实验依据。方法:收集天津无亲缘关系的汉族个体332例,定量荧光PCR(QF-PCR)扩增STR...目的:研究天津汉族群体21号染色体上D21S11、D21S1440和Penta D 3个短串联重复序列(STR)基因座遗传多态性,为唐氏综合征(DS)基因诊断和产前基因诊断提供实验依据。方法:收集天津无亲缘关系的汉族个体332例,定量荧光PCR(QF-PCR)扩增STR基因座,ABIPRISM 377测序仪检测PCR扩增产物。根据3个STR基因座的基因型分布进行Hardy-Weinberg平衡检验。计算3个STR基因座的基因型频率、观察杂合度(Ho)、多态信息量(PIC)、个体识别率(DP)、非父排除率(PE)等群体遗传学数据。结果:D21S11、D21S1440和Penta D 3个STR基因座分别检出6、4、8个等位基因,基因型分布均符合Hardy-Weinberg平衡定律。3个基因座的Ho分别为0.617、0.705、0.867,PIC分别为0.755、0.596、0.795,DP分别为0.916、0.794、0.931,PE分别为0.312、0.436、0.730。结论:D21S11、D21S1440和Penta D STR基因座在天津汉族群体杂合度高,是21号染色体良好的遗传标记,对DS的基因诊断有指导意义。展开更多
INTRODUCTION Pentatrichomonas hominis,an anaerobic flagellated protozoan that inhabits the large intestines of mammals and belongs to the Trichomonadidae family(Wenrich 1944;Kim et al.2010;Li et al.2014b,2016,2018a,20...INTRODUCTION Pentatrichomonas hominis,an anaerobic flagellated protozoan that inhabits the large intestines of mammals and belongs to the Trichomonadidae family(Wenrich 1944;Kim et al.2010;Li et al.2014b,2016,2018a,2020;Maritz et al.2014;Zhang et al.2019),is mainly transmitted through the fecal-oral route.It was originally presumed to be a commensal protozoan(Tolbert et al.2012)but was found to cause gastrointestinal symptoms.展开更多
基金supported by the National Natural Science Foundation of China (Grants 11372152 and 51420105001)the National Natural Science Foundation of United States (Grant CMMI-1161749)
文摘Penta-twinned Ag nanowires（pt-AgNWs） have recently attracted much attention due to their interesting mechanical and physical properties. Here we perform largescale atomistic simulations to investigate the influence of sample size and strain rate on the tensile strength of pt-AgNWs. The simulation results show an apparent size effect in that the nanowire strength（defined as the critical stress for dislocation nucleation） increases with decreasing wire diameter. To account for such size effect, a theoretical model involving the interaction between an emerging dislocation and the twin boundary has been developed for the surface nucleation of dislocations. It is shown that the model predictions are in quantitative agreement with the results from atomistic simulations and previous experimental studies in the literatures. The simulations also reveal that nanowire strength is strain-rate dependent, which predicts an activation volume for dislocation nucleation in the range of 1–10b^3,where b is the magnitude of the Burgers vector for a full dislocation.
基金Supported by the National Natural Science Foundation of China（21176070） the National High Technology Research and Development Program of China（2012AA040211）+2 种基金 the Joint Research Project of Yangtze River Delta（12195810900） the Specialized Research Fund for the Doctoral Program of Higher Education（20120074120019） the Fundamental Research Funds for the Central Universities
文摘Most of traditional linear poly(ethylene terephthalate)(PET)resins of relatively low molecular mass and narrow molecular mass distribution have low melt strength at foaming temperatures,which are not enough to support and keep cells.An in-situ polymerization-modification process with esterification and polycondensation stages was performed in a 2 L batch stirred reactor using pyromellitic dianhydride(PMDA)or pentaerythritol(PENTA)as modifying monomers to obtain PETs with high melt strength.The influence of amounts of modifying monomers on the properties of modified PET was investigated.It was found that the selected modifying monomers could effectively introduce branched structures into the modified PETs and improve their melt strength.With increasing the amount of the modifying monomer,the melt strength of the modified PET increased.But when the amount of PENTA reached 0.35%or PMDA reached 0.9%,crosslinking phenomenon was observed in the modified PET.Supercritical carbon dioxide(ScCO2)was employed as physical foaming agent to evaluate the foaming ability of modified PETs.The modified PETs had good foaming properties at 14 MPa of CO2pressure with foaming temperature ranging from 265°C to 280°C.SEM micrographs demonstrated that both modified PET foams had homogeneous cellular structures,with cell diameter ranging from 35μm to 49μm for PENTA modified PETs and38μm to 57μm for PMDA modified ones.Correspondingly,the cell density had a range of 3.5×107cells·cm 3to 7×106cells·cm 3for the former and 2.8×107cells·cm 3to 5.8×106cells·cm 3for the latter.
基金Supported by the National Natural Science Foundation of China (Nos.60805008,60928005,and 61003094)the Ph.D.Programs Foundation of the Ministry of Education of China (No.200800031015)
文摘In continuous speech, the pitch contour of the same syllable may vary much due to its contextual information. The Parallel Encoding and Target Approximation （PENTA） model is applied here to Mandarin speech synthesis with a method to predict pitch contours for Chinese syllables with different contexts by combining the Classification And Regression Tree （CART） with the PENTA model to improve its prediction accuracy. CART was first used to cluster the syllables＇ normalized pitch contours according to the syllables contextual information and the distances between pitch contours. The average pitch contour was used to train the PENTA model with the average contour for each cluster. The initial pitch is required with the PENTA model to predict a continuous pitch contour. A Pitch Discontinuity Model （PDM） was used to predict the initial pitches at positions with voiceless consonants and prosodic boundaries. Initial tests on a Chinese four-syllable word corpus containing 2048 words were extended to tests with a continuous speech corpus containing 5445 sentences. The results are satisfactory in terms of the Root Mean Square Error （RMSE） comparing the predicted pitch contour with the original contour. This method can model pitch contours for Mandarin sentences with any text for speech synthesis.
文摘目的:研究天津汉族群体21号染色体上D21S11、D21S1440和Penta D 3个短串联重复序列(STR)基因座遗传多态性,为唐氏综合征(DS)基因诊断和产前基因诊断提供实验依据。方法:收集天津无亲缘关系的汉族个体332例,定量荧光PCR(QF-PCR)扩增STR基因座,ABIPRISM 377测序仪检测PCR扩增产物。根据3个STR基因座的基因型分布进行Hardy-Weinberg平衡检验。计算3个STR基因座的基因型频率、观察杂合度(Ho)、多态信息量(PIC)、个体识别率(DP)、非父排除率(PE)等群体遗传学数据。结果:D21S11、D21S1440和Penta D 3个STR基因座分别检出6、4、8个等位基因,基因型分布均符合Hardy-Weinberg平衡定律。3个基因座的Ho分别为0.617、0.705、0.867,PIC分别为0.755、0.596、0.795,DP分别为0.916、0.794、0.931,PE分别为0.312、0.436、0.730。结论:D21S11、D21S1440和Penta D STR基因座在天津汉族群体杂合度高,是21号染色体良好的遗传标记,对DS的基因诊断有指导意义。
基金This work was supported by the grants from the National Natural Science Foundation of China(No.32102696)the National Key Research and Development Program of China(No.2021YFF0702900).
文摘INTRODUCTION Pentatrichomonas hominis,an anaerobic flagellated protozoan that inhabits the large intestines of mammals and belongs to the Trichomonadidae family(Wenrich 1944;Kim et al.2010;Li et al.2014b,2016,2018a,2020;Maritz et al.2014;Zhang et al.2019),is mainly transmitted through the fecal-oral route.It was originally presumed to be a commensal protozoan(Tolbert et al.2012)but was found to cause gastrointestinal symptoms.
