Isomeric Carborane Neuromuscular Blocking Agents

We synthesized a family of neuromuscular blocking agents (NMB) based on decamethonium, but containing a carborane cluster in the methylene chain between the two quaternary ammonium groups. The carborane cluster isomers o-NMB, m-NMB, and p-NMB were tested in animals for neuromuscular block and compared with agents used clinically: rocuronium and decamethonium. All three isomers caused reversible muscle weakness in mice as determined by grip strength and inverted screen tests, with a potency rank of p-NMB > rocuronium > decamethonium > m-NMB > o-NMB. The mechanism of action of the compounds was determined by using the in vitro rat phrenic nerve hemi-diaphragm preparation and electrophysiologic measurements in cells. Neostigmine reversed hemi-diaphragm weakness caused by the three isomers and rocuronium, but not succinylcholine. In electrophysiologic recordings of currents through acetylcholine receptor channels, the carborane compounds did not activate channel activity but did inhibit channel activation by acetylcholine. These results demonstrate that the carborane neuromuscular blocking agents are non-depolarizers in contrast to the depolarizing action of the parent compound.     

An economic and environment friendly way of recycling boron carbide waste to prepare B4C/Al composite ceramic

Recently, with the rapid growth of sapphire wafer applications, boron carbide as abrasive, has shown an increasing demand. Great amounts of boron carbide waste (low purity and small grain size with D₅₀ ≈ 1 μm) are therefore produced during the production of boron carbide abrasives and barely recovered and utilized. This paper is aimed at developing an economic and environment friendly process to recycle the boron carbide waste through adding a certain amount of Al powder to prepare B₄C/Al composite ceramic. Prior to the sintering process, samples were firstly mixed with different Al powder and then pelleted and dehydrated. The effects of the pelletizing factors on performances of the pellets and the ceramics were optimized as binder hydroxypropyl methylcellulose addition 0.4%, pelleting pressure 30 MPa, Al addition 9 wt%, sintering time 90 minutes. Under these conditions, the apparent porosity, bulk density, compressive strength and flexural strength of the sintered B₄C/Al are 19.08%, 1.84 g/cm³, 246.88 MPa and 71.10 MPa respectively. Al addition can not only attribute to the low-temperature liquid sintering and densification of the product, but also generation of some stable phases including AlB₁₂, AlB₁₂C₂ and Al₃BC, which in turn increase the performance of the ceramic composite.     

Heat propagation in thermally conductive polymers of PA6 and hexagonal boron nitride

Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant.     

Influence of h-BN as additive on microstructure and oxidation mechanism of C/C-SiC composite

Due to the favorable self-healing performance, hexagonal boron nitride (h-BN) as additive in the matrix can significantly influence the oxidation behavior and the kinetic characteristics of C/C-SiC composites. In this work, C/C-SiC composites modified by h-BN (C/C-BN-SiC) were prepared by low-temperature compression molding (LTCM), pyrolysis and liquid silicon infiltration (LSI). Microstructure, oxidation behavior and kinetic characteristics of the C/C-BN-SiC composites were investigated compared with the C/C-SiC composite. Because h-BN is non-wetted by liquid silicon, the h-BN flakes in the matrix can obstruct and prolong the flow path of silicon, and protect the carbon fibers from corrosion to a certain extent. The oxidation kinetics of composites occur in low and high temperature domains, with different oxidation-controlling mechanisms, and the addition of h-BN can hinder the inward diffusion and lead to the decline of carbon recession and apparent activation energy.     

以紫茎泽兰沼渣制作腐殖酸肥料的实验研究

以制作农残降解剂后紫茎泽兰的残渣残叶为原料,通过对其进行不同TS浓度的发酵实验,探究其适用于发酵的最佳浓度;并对发酵后沼渣的氮、磷、钾、腐殖酸等成分进行测定。结果表明,TS浓度为11.25%时产气较多;残渣腐殖酸含量与市场腐殖酸复合肥相近,但氮、钾元素相比含量较少。该实验可以为资源化利用紫茎泽兰、制作新型腐殖酸肥料提供参考依据。     

塔式熔体复合肥造粒工艺物料泵送方案设想和探讨

阐述塔式熔体复合肥造粒工艺在塔顶完成的制浆和造粒工序所存在的问题.设想并介绍采用塔下制浆,然后用液下泵通过管道输送至塔上进行喷淋造粒的方案.     

三卤化硼分子中的离域键对其性质的影响

从杂化轨道理论出发,探讨了三卤化硼分子（BX3,X=F,Cl,Br,I）中的σ共价键和离域大π键的形成,并用离域大π键解释了缺电子化合物三卤化硼的稳定性。用卤素的电负性及其三卤化硼的离域大π键这两个因素讨论了三卤化硼的Lewis酸性强弱顺序、水解及形成配合物的难易程度。     

钾长石制钾肥的化学释放法研究

介绍了几种利用钾长石生产钾肥及其他高附加值化工产品的技术,经比较发现,NSN法较其他方法更可行,不仅能耗低,而且实现了钾长石的综合利用,具有良好的经济效益和社会效益.     

碳化硼微粉的低温合成

以聚乙烯醇和硼酸为原料,首先合成聚乙烯醇硼酸酯前驱物凝胶,然后将前驱物热解及碳热还原制备碳化硼粉末。考察了聚乙烯醇与硼酸的物质的量比,前驱物热解温度,碳热还原温度以及还原时间等因素对碳化硼合成的影响。采用IR、化学分析、XRD、离心粒度分析、SEM等方法对中间物及产物进行了表征,确定了中间物及产物的组成、物相、粒度分布及形貌。研究结果表明：前驱物合成的适宜原料配比是n(聚乙烯醇)∶n(硼酸)=4∶1;前驱物在600 ℃下热解2 h,在1 300 ℃下碳热还原2 h,得到粒径为10 μm左右的碳化硼微粉。     

生物有机肥在果树上的应用效果研究

为提高果实品质,改良果园土壤,本试验研制开发了一种生物有机肥,在苹果、李、桃、葡萄上进行了田间对比试验。结果表明：生物有机肥与生产上习惯施用的有机肥相比,均有促进树体生长发育、提高产量、提高果实品质的作用。它表现在果树叶片浓绿、肥大,果实风味变浓、适口,着色艳丽;生物有机肥还对树体养分含量有调节作用,抑制由树体营养过剩...