Swelling-Based Chemical Sensing With Unmodified Optical Fibers

We use distributed fiber optic strain sensing to examine swelling of the fiber's polymer coating.The distributed sensing technique that uses unmodified low-cost...     

基于加权支持向量回归的网络流量预测

网络流量预测对于网络的安全和可用性至关重要,但是,传统的网络流量预测方法使用平均时间加权的方法进行预测,缺泛化能力导致预测精度低。基于每一个网络流量历史数据到预测点的时间间隔计算其时间权重,使用带时间权重的加权支持向量回归模型w-SVR预测网络流量。该模型因为其泛化能力和为每个训练数据设置单独的权重而提高了网络流量预测的准确性。模拟实验显示w-SVR模型相对于ANN和AR模型,预测错误率分别降低了37.4%和65.6%,而标准误差降低了46.2%和53.3%。     

ZrC改性C/C-SiC复合材料的力学和抗烧蚀性能

采用碳纤维针刺预制体, 用前驱体浸渍裂解(PIP)法分别制备了C/C-SiC和C/C-SiC-ZrC陶瓷基复合材料, 并对材料的微观结构、力学和烧蚀性能进行了分析对比。结果表明:利用该方法可制备出陶瓷相填充充分且分布均匀的复合材料。C/C-SiC-ZrC的面内弯曲强度、厚度方向的压缩强度、层间剪切强度均低于对应的C/C-SiC的。2 200 ℃、600 s氧化烧蚀后, C/C-SiC-ZrC的抗烧蚀性能显著优于C/C-SiC, 其线烧蚀率下降43.8%, 质量烧蚀率下降25%。在超高温阶段, C/C-SiC-ZrC复合材料基体的ZrC氧化生成的ZrO₂溶于SiC氧化生成的SiO₂中, 形成黏稠的二元玻璃态混合物, 有效阻止了氧化性气氛进入基体内部。      

Silicon-enhanced resistance to cadmium toxicity in Brassica chinensis L. is attributed to Si-suppressed cadmium uptake and transport and Si-enhanced antioxidant defense capacity

A series of hydroponics experiments were performed to investigate roles of silicon (Si) in enhancing cadmium (Cd) tolerance in two pakchoi (Brassica chinensis L.) cultivars: i.e. cv. Shanghaiqing, a Cd-sensitive cultivar, and cv. Hangyoudong, a Cd-tolerant cultivar. Plants were grown under 0.5 and 5 mg Cd L⁻¹ Cd stress without or with 1.5 mM Si. Plant growth of the Cd-tolerant cultivar was stimulated at the lower Cd level, but was decreased at the higher Cd level when plants were treated with Cd for one week. However, Plant growth was severely inhibited at both Cd levels as stress duration lasted for up to three weeks. Plant growth of the Cd-sensitive cultivar was severely inhibited at both Cd levels irrespective of Cd stress duration. Addition of Si increased shoot and root biomass of both cultivars at both Cd levels and decreased Cd uptake and root-to-shoot transport. Superoxide dismutase, catalase and ascorbate peroxidase activities decreased, but malondialdehyde and H₂O₂ concentrations increased at the higher Cd level, which were counteracted by Si added. Ascorbic acid, glutathione and non-protein thiols concentrations increased at the higher Cd level, which were further intensified by addition of Si. The effects of Si and Cd on the antioxidant enzyme activity were further verified by isoenzyme analysis. Silicon was more effective in enhancing Cd tolerance in the Cd-tolerant cultivar than in the Cd-sensitive cultivar. It can be concluded that Si-enhanced Cd tolerance in B. chinensis is attributed mainly to Si-suppressed Cd uptake and root-to-shoot Cd transport and Si-enhanced antioxidant defense activity.     

Predatory bird species show different patterns of hydroxylated polychlorinated biphenyls (HO-PCBs) and polychlorinated biphenyls (PCBs)

Hydroxylated metabolites of polychlorinated biphenyls (HO-PCBs) have previously been associated with endocrine disrupting effects. Since metabolic capacity may differ among species, we investigated the levels and profiles of HO-PCBs and PCBs in livers of four predatory bird species from Belgium. Maximum concentrations for sum HO-PCBs were found in the common buzzard (Buteo buteo) up to 13 700 pg/g wet weight (ww). The most prominent HO-PCB congener in all bird species was 4-HO-CB 187 (up to 6420 pg/g ww in buzzard liver), followed by 4-HO-CB148 in the buzzard (up to 1820 pg/g ww), sparrowhawk (Accipiter nisus), and grey heron (Ardea cinerea), and by 3'-HO-CB138 in long eared owl (Asio otus) and in one grey heron (up to 985 pg/g ww and 3450 pg/g ww, respectively). The mean profile of the grey heron differed from the other species with 3'-HO-CB138 and 4-HO-CB163 contributing more to the sum HO-PCBs. This indicates that aquatic and terrestrial predatory bird species may show differences in their HO-PCBs profiles. Variation in the diet and species-specific accumulation and metabolism of PCBs are probably the most important causes for these differences. Correlations between HO-PCBs and their parent PCBs were only found significant for buzzards.     

无硫高膨胀体积膨胀石墨的制备

采用化学氧化法,以粒径为180 μm的天然鳞片石墨为原料,在混酸（乙酸酐-磷酸-高氯酸）混合固体助氧化剂（高锰酸钾-重铬酸钾）体系下制得无硫可膨胀石墨。确定最佳合成条件为：m（鳞片石墨）∶V（混酸）∶m（高锰酸钾）∶m（重铬酸钾）=1（g）∶4（mL）∶0.1（g）∶0.1（g）,50 ℃反应60 min,40 ℃干燥2 h。在此条件下得到初始膨胀温度为 200 ℃的无硫可膨胀石墨,在500 ℃下的最大膨胀体积高达665 mL/g。通过SEM、FT-IR、XRD及TGA测试对鳞片石墨、可膨胀石墨和膨胀石墨进行结构、形貌、官能团分析。结果表明：可膨胀石墨片层间距增大,成功插入高氯酸、磷酸、乙酸酐;且经膨化后,得到纯度较高、孔隙较发达且片层晶体结构未改变的无硫高膨胀体积膨胀石墨。     

Cellular and Molecular Mechanism of Pulmonary Fibrosis Post-COVID-19: Focus on Galectin-1, -3, -8, -9

Pulmonary fibrosis is a consequence of the pathological accumulation of extracellular matrix (ECM), which finally leads to lung scarring. Although the pulmonary fibrogenesis is almost known, the last two years of the COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its post effects added new particularities which need to be explored. Many questions remain about how pulmonary fibrotic changes occur within the lungs of COVID-19 patients, and whether the changes will persist long term or are capable of resolving. This review brings together existing knowledge on both COVID-19 and pulmonary fibrosis, starting with the main key players in promoting pulmonary fibrosis, such as alveolar and endothelial cells, fibroblasts, lipofibroblasts, and macrophages. Further, we provide an overview of the main molecular mechanisms driving the fibrotic process in connection with Galactin-1, -3, -8, and -9, together with the currently approved and newly proposed clinical therapeutic solutions given for the treatment of fibrosis, based on their inhibition. The work underlines the particular pathways and processes that may be implicated in pulmonary fibrosis pathogenesis post-SARS-CoV-2 viral infection. The recent data suggest that galectin-1, -3, -8, and -9 could become valuable biomarkers for the diagnosis and prognosis of lung fibrosis post-COVID-19 and promising molecular targets for the development of new and original therapeutic tools to treat the disease.     

Scandium Recovery from Aqueous Solution by Adsorption Processes in Low-Temperature-Activated Alumina Products

In this paper, we studied the scandium adsorption from aqueous solutions on the surface of low-temperature-activated alumina products (GDAH). The GDAH samples are industrially manufactured, coming from the Bayer production cycle of the Sierra Leone bauxite as aluminium hydroxide, and further, by drying, milling, classifying and thermally treating up to dehydroxilated alumina products at low temperature. All experiments related to hydroxide aluminium activation were conducted at temperature values of 260, 300 and 400 °C on samples having the following particle sizes: <10 µm, 20 µm, <45 µm and <150 µm, respectively. The low-temperature-activated alumina products were characterised, and the results were published in our previous papers. In this paper, we studied the scandium adsorption process on the above materials and related thermodynamic and kinetic studies.     

炭/炭复合材料CVI工艺研究进展

化学气相渗透(CVI)致密技术能够赋予炭/炭(C/C)复合材料更优异的综合性能,是制备高性能炭基及陶瓷基复合材料的主要技术手段。综述了C/C复合材料CVI工艺的研究进展,详细介绍了CVI工艺的沉积反应过程及热解炭(PyC)的生成机理,对PyC的微观结构和CVI工艺增密效率的影响因素进行了讨论,最后提出了未来C/C复合材料CVI工艺的发展趋势。