Sintering behaviors and properties of porous ceramics derived from artificially cultured diatom frustules

Bimodal porous ceramics with high strength have been fabricated by conventional powder metallurgy utilizing artificially cultured diatom frustules (DFs). The effect of sintering temperature on thermal behaviors, phase transition, and pore structures features of DFs-based porous ceramics is investigated between 800 and 1200°C. The phase evolution of DFs powders is investigated with thermal analysis (DIL and DSC-TG). Phase transition behaviors analyzed with XRD, Raman, and FT-IR spectra confirm the transformation of quartz into cristobalite phases occurs under 1050°C. Sintering under 950°C could bind DFs powders tightly into high strength porous ceramics while maintain the multilayer pore structures simultaneously, having porosity of 56.4%, compressive strength of 15.0 MPa and surface area of 50.9 m²/g, respectively. Slit-shaped microstructures and mesopores (2-50 nm) are observed in DFs-based porous ceramics sintered under 1050°C. Collapse and blockage of pore structures as well as partial fusion of DFs particles happened at the temperature of 1100°C, indicating the presence of diminished multilayers and particle agglomeration.     

几种非金属矿物在建筑涂料改性中的应用

介绍了几种非金属矿——膨润土、硅藻土、高岭土以及累托石的基本性能及其在建筑涂料中的应用。     

升温速率对活体硅藻壳提纯的影响

选用一种舟形藻作为实验材料,研究了不同升温速率下硅藻壳的形态和成分变化。首先,对从该种硅藻得到的细胞壳进行酸洗处理,以去除金属离子和其它无机盐;之后,分别以1,3,5 和7℃/min的速率将硅藻壳升温至600℃,并保温2 h。然后,使用扫描电子显微镜、能量色散X射线分析和傅里叶变换红外分析3种手段对不同阶段和不同处理条件下的硅藻壳进行分析表征。实验显示：生物SiO₂的含量随着升温速率的降低而升高,以1℃/min升温到600℃并保温2 h的硅藻壳的SiO₂含量最高,其质量分数可达到90%,并且该硅藻壳能保持完整的原始形态。结果表明：由于硅藻的生物SiO₂结构具有较好的隔热性,热传导速度慢,故较快的升温速率很难使生物有机质充分分解,而过高的温度或保温时间又会对硅藻壳形态造成新的威胁。所以,较为缓慢的升温速率有益于有机质的充分去除和保证硅藻壳外观的完整性。     

高温热胁对Achnanthes sp.光系统的影响

本文以 A chnanthes sp.为例，通过测定其光系统II的量子产率的变化，间接分析高温热胁对其生长与消亡的影响。结果表明，光量子产率对高温胁迫有较强的响应，整个电子传递步骤的影响可以通过其变化反映出来。 A chnanthes sp.的最适温度范围为15℃～35℃，适温范围比较广，自然条件下温度对其光合活性影响较小。故而自然条件下高温不是其消亡的主要原因。     

我国天然活性水泥混合材的开发利用

对我国已经开发利用的１３种天然活性水泥混合材的应用效果作了比较全面的评述，并列举了应用实例。     

Hydrogen production by the thermophilic eubacterium Thermotoga neapolitana from storage polysaccharides of the CO2-fixing diatom Thalassiosira weissflogii

Planktic diatoms are the largest primary producers in marine and freshwater habitats. Their dry biomass accumulates up to 50% of lipids and contains water-soluble β-1,3-glucans as major storage products. Because of the world-wide abundance of these photosynthetic protists, β-1,3-glucans may rival cellulose as the polysaccharide with the highest annual production on Earth. Here we show the feasibility of a simple and efficient process leading to bio-hydrogen by dark fermentation of microalgal biomass with the thermophilic bacterium Thermotoga neapolitana. Production of the biogas on minimum medium supplemented only with the extract of the diatom Thalassiosira weissflogii proved that algal biomass per se can serve as substrate for sustaining the biotechnological process with no requirement of any pretreatment and external integration of other nutrients. At the same time, lipids unused for the anaerobic production of the biogas, can be employed for production of bio-diesel, thus considerably increasing the economic potential of these renewable feedstocks.     

不同光照下梅尼小环藻对昼夜温差变化的生理响应

为探讨硅藻在不同环境中对昼夜温差变化的响应机制,以梅尼小环藻为代表,研究了在高光照与低光照两种条件下,3种不同昼夜温差对梅尼小环藻生物量、光合活性、营养盐吸收利用的影响.试验结果表明:在5～10℃范围内,昼夜温差的减小能促进梅尼小环藻细胞密度与叶绿素a的增长,使其比生长速率增加;在高光照下,各组梅尼小环藻的最大量子产量...     

融合多尺度多头自注意力和在线难例挖掘的小样本硅藻检测

硅藻训练样本量较少时,检测精度偏低,为此在小样本目标检测模型TFA（Two-stage Fine-tuning Approach）的基础上提出一种融合多尺度多头自注意力（MMS）和在线难例挖掘（OHEM）的小样本硅藻检测模型（MMSOFDD）。首先,结合ResNet-101与多头自注意力机制构造一个基于Transformer的特征提取网络BoTNet-101,以充分利用硅藻图像的局部和全局信息;然后,改进多头自注意力为MMS,消除了原始多头自注意力的处理目标尺度单一的局限性;最后,引入OHEM到模型预测器中,并对硅藻进行识别与定位。把所提模型与其他小样本目标检测模型在自建硅藻数据集上进行消融及对比实验。实验结果表明：与TFA相比,MMSOFDD的平均精度均值（mAP）为69.60%,TFA为63.71%,MMSOFDD提高了5.89个百分点;与小样本目标检测模型Meta R-CNN和FSIW相比,Meta R-CNN和FSIW的mAP分别为61.60%和60.90%,所提模型的mAP分别提高了8.00个百分点和8.70个百分点。而且,MMSOFDD在硅藻训练样本量少的条件下能够有效地提高检测模型对硅藻的检测精度。     

A two-species marine algal bioassay for detecting aquatic toxicity of chemical pollutants

A simple, rapid and sensitive two-species marine algal bioassay for determining the toxicity of chemical pollutants was developed. The bioassay employs the marine diatoms Phaeodactylum tricornutum (clone Phaeo) and Cyclotella cryptica (clone 03A), which were selected after screening 40 clones of 32 species for an optimum pair of organisms. These algae are easily grown in the laboratory, and the cells can be differentiated and counted with an electronic particle counter. Alteration of species ratio and/or total biomass were used to determine toxicity. Polychlorinated biphenyls (PCB, Aroclor 1254) at 10 parts per thousand million (10⁹; ptm) significantly altered species ratio in favor of Phaeo, and 10 ptm of DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) and 20 ptm of dieldrin produced a significant species alteration opposite to that produced by PCB.