A numerical model based on measured fictive temperature distributions is explored to evaluate the residual stress fields of CO_(2)laser-annealed mitigated fused silica damage sites.The proposed model extracts the resi...A numerical model based on measured fictive temperature distributions is explored to evaluate the residual stress fields of CO_(2)laser-annealed mitigated fused silica damage sites.The proposed model extracts the residual strain from the differences in thermoelastic contraction of fused silica with different fictive temperatures from the initial frozen-in temperatures to ambient temperature.The residual stress fields of mitigated damage sites for the CO_(2)laser-annealed case are obtained by a finite element analysis of equilibrium equations and constitutive equations.The simulated results indicate that the proposed model can accurately evaluate the residual stress fields of laser-annealed mitigated damage sites with a complex thermal history.The calculated maximum hoop stress is in good agreement with the reported experimental result.The estimated optical retardance profiles from the calculated radial and hoop stress fields are consistent with the photoelastic measurements.These results provide sufficient evidence to demonstrate the suitability of the proposed model for describing the residual stresses of mitigated fused silica damage sites after CO_(2)laser annealing.展开更多
质子交换膜燃料电池(PEMFCs)因其高能量密度、低操作温度和环保等特性,被视为极具潜力的能量转换系统.目前,碳载铂颗粒(Pt/C)是PEMFCs阴极氧还原反应(ORR)中使用最广泛的催化剂.然而,Pt与碳载体间的电子结构差异导致Pt纳米颗粒(Pt NPs)...质子交换膜燃料电池(PEMFCs)因其高能量密度、低操作温度和环保等特性,被视为极具潜力的能量转换系统.目前,碳载铂颗粒(Pt/C)是PEMFCs阴极氧还原反应(ORR)中使用最广泛的催化剂.然而,Pt与碳载体间的电子结构差异导致Pt纳米颗粒(Pt NPs)易从碳载体上脱落,严重降低了ORR的催化活性.此外,Pt的高成本和稀缺性也限制了其广泛应用.相比之下,Pt纳米枝晶(NDs)因具有高利用率的表面活性位点而备受关注.然而,Pt NDs的合成通常需要严格控制反应条件,且其与碳基底间的弱相互作用易导致活性位点损失和性能下降.因此,开发具有强金属载体相互作用的Pt复合碳催化剂对PEMFCs的实际应用至关重要.本文通过原位Cl-介导的生长策略,结合碳本征空位工程,成功制备了分散在富含碳本征空位的中空氮掺杂碳基底上的Pt NDs催化剂(Pt@HNC-V-800).拉曼光谱和电子顺磁共振光谱结果表明,碳本征空位的形成机制源于碳基底结构中氮原子的耗散,该过程引起碳原子的重新排列,进而产生了丰富的本征缺陷位点.X射线吸收光谱和X射线光电子能谱结果表明,与无碳空位的Pt@HNC催化剂相比,富含本征碳空位的样品(Pt@HNC-V-800)表现出较低的Pt-Pt键配位数(8.64)和更强的给电子效应.得益于Pt NDs丰富的活性位点及其与本征碳空位基底之间的强电子效应,Pt@HNC-V-800的ORR半波电位高达0.947 V,质量活性和比表面活性分别为1.55 A mg^(-1) Pt和1.85 mA cm^(-2),是商用Pt/C的8.2和6.8倍(0.191 A mg^(-1)Pt和0.27 mA cm^(-2)).加速耐久性测试结果表明,经20000次电势循环后,Pt@HNC-V-800的活性无明显变化,其活性损失远低于无碳本征空位的Pt@HNC材料和商业Pt/C催化剂.因此,与无碳本征空位的Pt@HNC材料相比,Pt@HNC-V-800的ORR活性和稳定性都有较大提升,进一步证实了碳本征空位工程协同Pt NDs策略的优越性.此外,密度泛函理论计算结果表明,Pt@HNC-V的丰富�展开更多
A thinner cortex has higher potential for binding GABA receptor A which is associated with larger amplitudes of intrinsic brain activity(i BA). However, the relationship between cortical thickness and i BA is unknown ...A thinner cortex has higher potential for binding GABA receptor A which is associated with larger amplitudes of intrinsic brain activity(i BA). However, the relationship between cortical thickness and i BA is unknown in intact and epileptic brains. To this end, we investigated the relationship between cortical thickness measured by highresolution MRI and surface-based i BA derived from resting-state functional MRI in normal controls(n = 82) andpatients with generalized tonic–clonic seizures(GTCS)only(n = 82). We demonstrated that the spatial distribution of cortical thickness negatively correlated with surface-based i BA amplitude at both whole-brain and within independent brain functional networks. In GTCS patients,spatial coupling between thickness and i BA amplitude decreased in the default mode, dorsal attention, and somatomotor networks. In addition, the vertex-wise acrosssubject thickness–i BA amplitude correspondence altered in the frontal and temporal lobes as well as in the precuneus in GTCS patients. The relationship between these two modalities can serve as a brain-based marker for detecting epileptogenic changes.展开更多
Over 3 million tons of manures are produced annually in the United States and pose environmental and health risks if not remediated. Anaerobic digestion is an effective method in treating organic wastes to reduce envi...Over 3 million tons of manures are produced annually in the United States and pose environmental and health risks if not remediated. Anaerobic digestion is an effective method in treating organic wastes to reduce environmental impacts and produce methane as an alternative energy. Previous studies suggested that optimization of feed composition, hydraulic retention time, and other operational conditions can greatly improve total solids removal and increase methane productivity. These environmental factors improve functionality by altering the microbial community structure but explicit details of how the bacterial community shifts are poorly understood. Our investigations were conducted to investigate the relationship between environmental factors, microbial community structure and bioreactor efficiency by using metagenomic analysis of the microbial communities. Our results indicated that the bioreactor with the greatest methane production, digestion efficiency and reduced levels of E. coli/Shigella had a distinctive community structure at the genus level with unique and abundant uncultivated strains of Bacteroidetes. Moreover the same bioreactor was enriched in Aminomonas paucivorans and Clostridia populations that can utilize secondary metabolites produced during cellulose/hemicellulose degradation to generate hydrogen and acetate. Hence specific digestion conditions that enrich for these populations may provide a route to the optimization of co-digestion systems and control the variability in reactor performance.展开更多
【目的】从北海涠洲岛海域腐烂的马尾藻中分离得到的海洋弧菌(Vibrio X511)具有较强的利用褐藻胶能力,本文利用转录组测序的方法以研究弧菌X511的褐藻胶代谢途径。【方法】采用Illumina Hi Seq2500测序平台对菌株在褐藻胶及葡萄糖培养...【目的】从北海涠洲岛海域腐烂的马尾藻中分离得到的海洋弧菌(Vibrio X511)具有较强的利用褐藻胶能力,本文利用转录组测序的方法以研究弧菌X511的褐藻胶代谢途径。【方法】采用Illumina Hi Seq2500测序平台对菌株在褐藻胶及葡萄糖培养下的转录组进行测序;比较和分析差异转录本,利用荧光定量PCR验证测序结果;采用GO(Gene Ontology)和KEGG(Kyoto Encyclopedia of Genes and Genomes)对差异转录本进行功能和Pathway注释。【结果】经比较发现,菌株在褐藻胶培养下相对于葡萄糖的培养共有2024个差异表达基因,其中1066个基因上调,958个基因下调;某些普遍存在于代谢途径中的基因在不同培养条件下也存在差异表达;海洋弧菌X511中涉及褐藻胶利用的所有基因以及合成乙醇的关键基因其转录量均有一定程度的上调;此外,通过分析发现该菌株具有独特的褐藻胶利用方式,其中的一个代谢过程尚未在弧菌中被报道。【结论】成功解析了海洋弧菌X511的褐藻胶代谢途径,丰富了生物方法降解褐藻胶的研究,为大型海藻生物质能源的研究提供有价值的数据支持。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.62275235).
文摘A numerical model based on measured fictive temperature distributions is explored to evaluate the residual stress fields of CO_(2)laser-annealed mitigated fused silica damage sites.The proposed model extracts the residual strain from the differences in thermoelastic contraction of fused silica with different fictive temperatures from the initial frozen-in temperatures to ambient temperature.The residual stress fields of mitigated damage sites for the CO_(2)laser-annealed case are obtained by a finite element analysis of equilibrium equations and constitutive equations.The simulated results indicate that the proposed model can accurately evaluate the residual stress fields of laser-annealed mitigated damage sites with a complex thermal history.The calculated maximum hoop stress is in good agreement with the reported experimental result.The estimated optical retardance profiles from the calculated radial and hoop stress fields are consistent with the photoelastic measurements.These results provide sufficient evidence to demonstrate the suitability of the proposed model for describing the residual stresses of mitigated fused silica damage sites after CO_(2)laser annealing.
文摘质子交换膜燃料电池(PEMFCs)因其高能量密度、低操作温度和环保等特性,被视为极具潜力的能量转换系统.目前,碳载铂颗粒(Pt/C)是PEMFCs阴极氧还原反应(ORR)中使用最广泛的催化剂.然而,Pt与碳载体间的电子结构差异导致Pt纳米颗粒(Pt NPs)易从碳载体上脱落,严重降低了ORR的催化活性.此外,Pt的高成本和稀缺性也限制了其广泛应用.相比之下,Pt纳米枝晶(NDs)因具有高利用率的表面活性位点而备受关注.然而,Pt NDs的合成通常需要严格控制反应条件,且其与碳基底间的弱相互作用易导致活性位点损失和性能下降.因此,开发具有强金属载体相互作用的Pt复合碳催化剂对PEMFCs的实际应用至关重要.本文通过原位Cl-介导的生长策略,结合碳本征空位工程,成功制备了分散在富含碳本征空位的中空氮掺杂碳基底上的Pt NDs催化剂(Pt@HNC-V-800).拉曼光谱和电子顺磁共振光谱结果表明,碳本征空位的形成机制源于碳基底结构中氮原子的耗散,该过程引起碳原子的重新排列,进而产生了丰富的本征缺陷位点.X射线吸收光谱和X射线光电子能谱结果表明,与无碳空位的Pt@HNC催化剂相比,富含本征碳空位的样品(Pt@HNC-V-800)表现出较低的Pt-Pt键配位数(8.64)和更强的给电子效应.得益于Pt NDs丰富的活性位点及其与本征碳空位基底之间的强电子效应,Pt@HNC-V-800的ORR半波电位高达0.947 V,质量活性和比表面活性分别为1.55 A mg^(-1) Pt和1.85 mA cm^(-2),是商用Pt/C的8.2和6.8倍(0.191 A mg^(-1)Pt和0.27 mA cm^(-2)).加速耐久性测试结果表明,经20000次电势循环后,Pt@HNC-V-800的活性无明显变化,其活性损失远低于无碳本征空位的Pt@HNC材料和商业Pt/C催化剂.因此,与无碳本征空位的Pt@HNC材料相比,Pt@HNC-V-800的ORR活性和稳定性都有较大提升,进一步证实了碳本征空位工程协同Pt NDs策略的优越性.此外,密度泛函理论计算结果表明,Pt@HNC-V的丰富�
基金supported by the National High Technology Research and Development Program of China(2015AA020505)the Natural Science Foundation of China(61533006,81201155,81301198,81471653,81401400,81271553,and 81422022)+1 种基金the Fundamental Research Funds for the Central Universities(ZYGX2013Z004)the China Postdoctoral Science Foundation(2013M532229)
文摘A thinner cortex has higher potential for binding GABA receptor A which is associated with larger amplitudes of intrinsic brain activity(i BA). However, the relationship between cortical thickness and i BA is unknown in intact and epileptic brains. To this end, we investigated the relationship between cortical thickness measured by highresolution MRI and surface-based i BA derived from resting-state functional MRI in normal controls(n = 82) andpatients with generalized tonic–clonic seizures(GTCS)only(n = 82). We demonstrated that the spatial distribution of cortical thickness negatively correlated with surface-based i BA amplitude at both whole-brain and within independent brain functional networks. In GTCS patients,spatial coupling between thickness and i BA amplitude decreased in the default mode, dorsal attention, and somatomotor networks. In addition, the vertex-wise acrosssubject thickness–i BA amplitude correspondence altered in the frontal and temporal lobes as well as in the precuneus in GTCS patients. The relationship between these two modalities can serve as a brain-based marker for detecting epileptogenic changes.
文摘Over 3 million tons of manures are produced annually in the United States and pose environmental and health risks if not remediated. Anaerobic digestion is an effective method in treating organic wastes to reduce environmental impacts and produce methane as an alternative energy. Previous studies suggested that optimization of feed composition, hydraulic retention time, and other operational conditions can greatly improve total solids removal and increase methane productivity. These environmental factors improve functionality by altering the microbial community structure but explicit details of how the bacterial community shifts are poorly understood. Our investigations were conducted to investigate the relationship between environmental factors, microbial community structure and bioreactor efficiency by using metagenomic analysis of the microbial communities. Our results indicated that the bioreactor with the greatest methane production, digestion efficiency and reduced levels of E. coli/Shigella had a distinctive community structure at the genus level with unique and abundant uncultivated strains of Bacteroidetes. Moreover the same bioreactor was enriched in Aminomonas paucivorans and Clostridia populations that can utilize secondary metabolites produced during cellulose/hemicellulose degradation to generate hydrogen and acetate. Hence specific digestion conditions that enrich for these populations may provide a route to the optimization of co-digestion systems and control the variability in reactor performance.
文摘【目的】从北海涠洲岛海域腐烂的马尾藻中分离得到的海洋弧菌(Vibrio X511)具有较强的利用褐藻胶能力,本文利用转录组测序的方法以研究弧菌X511的褐藻胶代谢途径。【方法】采用Illumina Hi Seq2500测序平台对菌株在褐藻胶及葡萄糖培养下的转录组进行测序;比较和分析差异转录本,利用荧光定量PCR验证测序结果;采用GO(Gene Ontology)和KEGG(Kyoto Encyclopedia of Genes and Genomes)对差异转录本进行功能和Pathway注释。【结果】经比较发现,菌株在褐藻胶培养下相对于葡萄糖的培养共有2024个差异表达基因,其中1066个基因上调,958个基因下调;某些普遍存在于代谢途径中的基因在不同培养条件下也存在差异表达;海洋弧菌X511中涉及褐藻胶利用的所有基因以及合成乙醇的关键基因其转录量均有一定程度的上调;此外,通过分析发现该菌株具有独特的褐藻胶利用方式,其中的一个代谢过程尚未在弧菌中被报道。【结论】成功解析了海洋弧菌X511的褐藻胶代谢途径,丰富了生物方法降解褐藻胶的研究,为大型海藻生物质能源的研究提供有价值的数据支持。
