酶预处理结合研磨法对桉树纸浆纤维微/纳纤丝微观形貌的影响

【目的】探究酶用量、酶解时间及研磨时间对制备的桉树纸浆纤维微/纳纤丝微观形貌及性能的影响。【方法】以桉树纸浆为原料,经不同的酶用量(20,40,60和80ECU/g)和酶解时间(2,4,6和8h)预处理后,用研磨法制备纤维素微/纳纤丝,利用扫描电镜、X射线衍射仪对制备的微/纳纤丝进行表征。【结果】在酶解时间为6h的条件下,当酶用量由20ECU/g增加至80ECU/g时,研磨制备的微/纳纤丝直径由143.89nm减小至52.21nm;在酶用量为60ECU/g的条件下,当酶解时间由2h增加至8h时,研磨制备的微/纳纤丝直径由131.23nm减小至43.73nm。酶处理后的纤维及研磨处理后的纤维均保持了天然纤维的Ⅰ型结构,结晶度分别比纸浆纤维(59.21%)提高11.68%和8.31%,所制备的微/纳纤丝的结晶度为67.52%。【结论】酶预处理可以有效降低微/纳纤丝的制备时间,减少能耗;随着酶用量及酶解时间的增加,微/纳纤丝直径逐渐减小;纤维素酶可降解纤维素部分非结晶区并使纤维润胀。     

腐植酸负载纳米零价铁对镉污染农田水稻籽粒代谢的影响

为探究腐植酸负载纳米零价铁(nZVI@HA)对镉(Cd)污染修复过程中水稻籽粒营养物质合成过程的影响,本研究采用吸附络合-液相还原法制备了一种nZVI@HA材料,同时开展水稻盆栽实验,利用电感耦合等离子体质谱及超高效液相色谱质谱技术,比较研究了nZVI@HA、纳米零价铁(nZVI)、腐植酸(HA)及nZVI与HA联合处理对Cd污染修复过程中水稻产量、籽粒中Cd含量及籽粒代谢物质组成的影响。结果表明：3组含Fe0处理均可提升水稻产量、降低水稻籽粒Cd的赋存水平。尤其是在nZVI@HA作用下,水稻产量显著提升至空白组的188%、籽粒Cd含量降至0.155 mg·kg^-1,低于我国大米Cd限量标准(0.2 mg·kg^-1,GB 2762—2022)。代谢组学分析显示,各含Fe0处理均可显著促进水稻籽粒倍他林生物合成及精氨酸和脯氨酸代谢(P<0.05且VIP>1);同时Cd污染修复过程中,水稻籽粒还可通过丙氨酸、天冬氨酸和谷氨酸代谢,核苷酸代谢,甘氨酸、丝氨酸和苏氨酸代谢,及甘油磷脂代谢特异性响应nZVI@HA处理。研究表明,nZVI@H...     

改性纳米SiO2−壳聚糖乳液的制备及性质研究

为了解壳聚糖所形成天然乳液的稳定性及纳米SiO₂添加量对其性质的影响,研究以纳米SiO₂改性壳聚糖（CS）为水相、山茶油为油相构建CS−纳米SiO₂复合乳液。通过测定乳化活性、乳化稳定性、离心稳定性、平均粒径和流变学性能分析纳米SiO₂添加量（质量分数 1.00%、3.00%、5.00%、7.00% 和 9.00%）对CS−纳米SiO₂复合乳液的理化性质的影响;同时将粒径分布与电镜、光学显微镜相结合进行微观结构和表面形态分析。结果表明,与CS乳液相比,复合乳液理化性质得到改善,表现出更高的稳定性。纳米SiO₂添加量为5.00%时,乳液的综合性能最好。乳化活性从9.29 m²/g升高为10.36 m²/g,增加了10.37%;乳化稳定性由484 min升至541 min,升高10.53%;离心稳定系数显著（P<0.05）降低54.56%,粒径为12.98 μm,粒径分布窄峰值高。乳液黏度、储能模量、损耗模量增加,乳液呈现凝胶状。扫描电子显微镜和光学显微镜观察结果表明,乳液分布均匀、外观均一。     

羟磷灰石/SDBS丝网印刷碳电极快速测定茶叶痕量铅

摘要:为改善快速测定铅电化学传感器的稳定性、灵敏度和安全性,本研究利用SDBS(十二烷基苯磺酸钠)分散羟磷灰石替代惯用的有毒汞修饰丝网印刷碳电极,并滴加Nafion膜增加稳定性,构建了一种快速测定痕量铅的新型电化学传感器.采用方波溶出伏安法,支持电解质为0.1 mol/L HAc-NaAc,在优化的羟磷灰石量、测试底液pH、富集时间等工作条件下,得到2～300μg/L线性范围内的铅标准曲线,检测限为0.46 μg/L(S/N=3);其重复性好,连续5次测定后的相对标准偏差为4.59％;本方法与ICP-MS法对茶叶样本的测定结果相近.研究出的快速检测铅的新型电化学传感器具有较好的稳定性、灵敏度和     

杉木木材/蒙脱土纳米复合材料的结构和表征

该文预先合成水溶性酚醛树脂作为中间介质,通过加压浸渍处理制备了杉木木材/蒙脱土纳米复合材料(WMNC),采用XRD、SEM、FTIR、TG-DTA等分析手段对WMNC的结构特性进行了表征.结果表明:①由于部分蒙脱土剥离片层进入了杉木木材细胞壁,WMNC中杉木木材的结晶度降低.②由于蒙脱土改性、树脂分子对蒙脱土的插层以及木材浸渍处理过程等的差异,蒙脱土在WMNC中的大小、形态和分布具多样性.蒙脱土填充的不均匀性,与杉木木材本身的渗透变异性相关.WMNC中的蒙脱土,部分填充于木材细胞腔等大孔隙,部分附着在木材细胞腔内壁,部分进入了细胞壁.③WMNC的缔合羟基增多,醚键大量增多,蒙脱土与杉木木材可能存在氢键或化学键结合.④WMNC的热分解历程改变,热性能提高,起始分解温度降低,高温区的热解失重显著减少,在一定程度上体现了无机复合组分蒙脱土纳米片层的纳米复合效应.      

Dietary nano‐selenium enhances antioxidant capacity and hypoxia tolerance of grass carp Ctenopharyngodon idella fed with high‐fat diet

To evaluate the effects of dietary nano‐selenium (Nano‐Se) on antioxidant capacity and hypoxia tolerance of grass carp fed with high‐fat diet, experimental fishes were fed Nano‐Se supplemented diets at doses of 0 (Control), 0.3, 0.6, 0.9 and 1.2 mg/kg for 10 weeks. After feeding trial, a part of the fishes were exposed to hypoxia stress. Results showed that the survival ratio of grass carp significantly increased in 0.6 and 0.9 mg/kg Nano‐Se group, and the content of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) significantly decreased in 0.6–1.2 mg/kg Nano‐Se groups compared with the control group. In addition, dietary Nano‐Se significantly enhanced glutathione peroxidase (GPX) activity and reduced the malondialdehyde (MDA) content in fishes fed diets with 0.3 and 0.6 mg/kg Nano‐Se. Dietary Nano‐Se significantly elevated mRNA expression of GPX1 and catalase (CAT) by promoting the mRNA expression of NF‐E2‐related nuclear factor 2 (Nrf2) in the hepatopancreas. After hypoxia stress, the GPX and superoxide dismutase (SOD) activities were significantly enhanced, and the MDA content and mortality rate consequently decreased in fishes fed diets with 0.3 and 0.6 mg/kg Nano‐Se. In summary, these results suggested that optimal Nano‐Se in diet enhanced the antioxidant capacity and hypoxia tolerance of grass carp.     

食盐添加对乌鳢鱼头汤熬煮过程营养物质溶出与微纳米颗粒稳定性的影响

在鱼头汤熬制过程中,食盐添加后会与汤中物质发生相互作用,进而影响产品品质。本文研究了NaCl添加时机对乌鳢(Channa argus)鱼头汤中营养物质迁移以及微纳米颗粒(micro and nano particles, MNPs)稳定性的影响。结果表明,鱼头汤加盐前的熬煮时间和加盐后Na+、Cl–与各组分间的相互作用对物质的迁移具有重要影响,同时还会影响体系中微纳米颗粒形成,并最终影响体系的稳定性。在熬煮至60 min时加盐时机最佳。此条件下制得的汤中营养物质和呈味物质的溶出和迁移达到最大程度,所形成的微纳米颗粒为大小均匀的双层球状小颗粒,甘油三酯自组装形成球形颗粒,蛋白质分子分散在其周围或与之结合附着在表面,体系呈现出良好的稳定性。研究结果可以为乌鳢鱼头汤制品的生产提供参考。     

磁性HAP/Fe3O4材料去除水土环境中Cd的效果研究

为探究磁性羟基磷灰石/四氧化三铁(HAP/Fe₃O₄)纳米材料对水土环境中Cd的去除效果,以米糠为原料,采用水热法制备纳米材料,通过水中吸附实验和土壤培养实验对Cd去除效果进行研究。结果表明:pH为8时,HAP/Fe₃O₄对Cd的吸附更符合伪二阶动力学模型,吸附过程以化学吸附为主。溶液为酸性时,HAP/Fe₃O₄对Cd²⁺的吸附机制可能为表面吸附和生成沉淀,溶液为中碱性时,对Cd²⁺的去除以表面吸附以及离子交换为主。此外,HAP/Fe₃O₄在5次循环后吸附能力仍保持在较高水平,说明其作为吸附剂具有较高的可重复利用性。在土壤实验中,土壤pH随培养时间的延长和HAP/Fe₃O₄投加量的增加,总体呈上升趋势。与对照组相比,HAP/Fe₃O₄添加量为0.5%的处理显著降低了土壤CaCl₂提取态Cd含量,降幅为62%;浸出实验证明HAP/Fe₃O₄增强了土壤中重金属的滞留能力。HAP/Fe₃O₄纳米材料作为一种原料价格低廉且环境友好的吸附剂在处理水污染和修复土壤方面应用前景广阔。     

纳米ZnO改性蜂蜡处理缅甸花梨木材表面性能

为了提升传统烫蜡工艺处理后木材的表面性能,采用3种质量分数(0.5%、1.0%、2.0%)的纳米ZnO分别对烫蜡原料蜂蜡进行共混改性,并按照传统烫蜡工艺对缅甸花梨木试件进行表面改性蜂蜡烫蜡处理。采用扫描电子显微镜和能谱仪对处理材的微观形貌及纳米材料分散情况进行表征,通过分析处理材表面的耐紫外老化性、疏水性及抗菌性,探讨不同纳米ZnO含量对烫蜡后木材表面性能的影响。结果表明:经纳米ZnO改性蜂蜡烫蜡后的木材表面的颜色稳定性、疏水性和抗菌性均得到了明显改善。质量分数为1%的纳米ZnO改性蜂蜡处理材的表面性能最佳;96 h紫外老化后,其总色差较纯蜂蜡处理材降低了42%,接触角始终保持在102°以上;具备了显著的抗菌性,抑菌率可达65%。纳米 ZnO改性蜂蜡烫蜡后的木器颜色能够持久稳定,对于烫蜡木器使用范围的扩展具有重要意义。      

Chitosan composites for bone tissue engineering--an overview

Bone contains considerable amounts of minerals and proteins. Hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] is one of the most stable forms of calcium phosphate and it occurs in bones as major component (60 to 65%), along with other materials including collagen, chondroitin sulfate, keratin sulfate and lipids. In recent years, significant progress has been made in organ transplantation, surgical reconstruction and the use of artificial protheses to treat the loss or failure of an organ or bone tissue. Chitosan has played a major role in bone tissue engineering over the last two decades, being a natural polymer obtained from chitin, which forms a major component of crustacean exoskeleton. In recent years, considerable attention has been given to chitosan composite materials and their applications in the field of bone tissue engineering due to its minimal foreign body reactions, an intrinsic antibacterial nature, biocompatibility, biodegradability, and the ability to be molded into various geometries and forms such as porous structures, suitable for cell ingrowth and osteoconduction. The composite of chitosan including hydroxyapatite is very popular because of the biodegradability and biocompatibility in nature. Recently, grafted chitosan natural polymer with carbon nanotubes has been incorporated to increase the mechanical strength of these composites. Chitosan composites are thus emerging as potential materials for artificial bone and bone regeneration in tissue engineering. Herein, the preparation, mechanical properties, chemical interactions and in vitro activity of chitosan composites for bone tissue engineering will be discussed.