Volcanic production of polyphosphates and its relevance to prebiotic evolution

Phosphates would probably have been essential compounds for prebiotic evolution on the primitive Earth. In this context, there have been several studies of condensation of water-soluble phosphates to polyphosphates and phosphorylation and condensation or polymerization of biomolecules with polyphosphates. But most of the phosphorus on the early Earth would have been in the form of water-insoluble apatite, and the origin of the water-soluble polyphosphates required for prebiotic evolution has therefore been a mystery. Here we show, both from experiments that simulate magmatic conditions and from analysis of volatile condensates in volcanic gas, that volcanic activity can produce water-soluble polyphosphates through partial hydrolysis of P4O10. This mechanism seems to be the only viable route identified so far for the production of these species on the primitive Earth.     

肝内钙化灶超声误诊分析

对２２例Ｂ超诊断为肝内胆管结石,经手术证实为肝内钙化灶的病例进行了分析。误诊原因：（１）缺乏区别肝内强回声灶的经验;（２）未注意肝内强回声灶与胆管的关系;（３）未行逆行胰胆管造影和经皮肝胆管造影。认为,仔细进行检查是减少误诊和提高诊断精度的关键     

巧用多种媒体优化课堂教学

课堂教学中对多种媒体综合协调,合理运用,能促使学生积极主动、自主探索地学习,从而促进学生的发展和教学质量的提高。结合多年数学教学经验,就数学课堂中多种教学媒体的综合运用,谈了几点看法。     

新型高聚合度聚磷酸铵阻燃材料的合成

对高聚合度聚磷酸铵的聚合条件进行了优化实验,制备了平均聚合度为600的聚磷酸铵．研究了磷酸铵、组分配比、反应温度、反应气氛、反应时间和处理温度、处理时间、处理气氛对平均聚合度的影响．结果表明高聚合度APP的生产工艺条件为：1：1：0．3（摩尔比）的（NH4）2HPO4,P2O5和尿素混合均匀后,于干燥氨气氛下280-300℃充分搅拌进行聚合反应,聚合反应时间为20min以上,聚合反应完全后于同样气氛下,250-280℃热处理100～120min,即得粉末状的APP聚合物,通过端基滴定法测定聚合度,其平均聚合度大于600．     

Trifluoromethylation of arenes and heteroarenes by means of photoredox catalysis

Modern drug discovery relies on the continual development of synthetic methodology to address the many challenges associated with the design of new pharmaceutical agents. One such challenge arises from the enzymatic metabolism of drugs in vivo by cytochrome P450 oxidases, which use single-electron oxidative mechanisms to rapidly modify small molecules to facilitate their excretion. A commonly used synthetic strategy to protect against in vivo metabolism involves the incorporation of electron-withdrawing functionality, such as the trifluoromethyl (CF(3)) group, into drug candidates. The CF(3) group enjoys a privileged role in the realm of medicinal chemistry because its incorporation into small molecules often enhances efficacy by promoting electrostatic interactions with targets, improving cellular membrane permeability, and increasing robustness towards oxidative metabolism of the drug. Although common pharmacophores often bear CF(3) motifs in an aromatic system, access to such analogues typically requires the incorporation of the CF(3) group, or a surrogate moiety, at the start of a multi-step synthetic sequence. Here we report a mild, operationally simple strategy for the direct trifluoromethylation of unactivated arenes and heteroarenes through a radical-mediated mechanism using commercial photocatalysts and a household light bulb. We demonstrate the broad utility of this transformation through addition of CF(3) to a number of heteroaromatic and aromatic systems. The benefit to medicinal chemistry and applicability to late-stage drug development is also shown through examples of the direct trifluoromethylation of widely prescribed pharmaceutical agents.     

苯甲醛及其类似物对酪氨酸酶抑制作用的研究

酪氨酸酶是一种金属铜蛋白,广泛存在于自然界中,在生物体合成黑色素过程中起着关键作用。分别以多巴和以邻苯二酚作为酪氨酸酶催化底物,对苯甲醛及其类似物对酪氨酸酶抑制作用机理进行了详细的研究,并利用CD(圆二色谱)研究了苯甲醛类化合物对酪氨酸酶的构象影响,提出苯甲醛及其同系物与酶分子相互作用的可能机理。     

用物化法建立甲基吡啶类缓蚀剂的缓蚀模型及其方程

本文提出一个在盐酸液中的吡啶及甲基吡啶对铁的缓蚀模型,按此模型利用自由能最小原理和单分子层吸附模型,以及各种缓蚀粒子的有效吸附直径等推导出缓蚀率E的方程为:lnE=AlnC+BpK_b+D.根据8种缓蚀剂各自4种浓度（C）下的E的实验值和相应的pK_b值,用多元回归法求得此方程的A=0.5617;B=-0.0464;D=0.6087;相关系数r=0.998;F值为3845。按R=1/（1-E）式,求得缓蚀效果R的方程为:R=1/[1-exp（0.5617lnC-0.0464pK_b+0.6087）]。用此方程所得的32个R计算值与其实验值很符合,其平均相对误差为3.6%。     

清水回流提高硝化和反硝化速率

目前大多数城市污水处理工艺主要还是以活性污泥法为主.为了提高水处理时总氮(N)的去除效率,缺氧/好氧(A/O)工艺被普遍采用.但在该工艺中,缺氧池(A池)和好氧池(O池)通常均没有独立的沉降过程,因此两池之间的回流都是连泥带水一起回流.基于专利技术"垂直折流式生物反应器"(VBBR)可以轻易实现泥水分离,做到清水回流,因此研究采用对比的方法探讨了清水回流是否可以提高硝化和反硝化速率.实验结果表明:若采用清水回流,相比传统的泥水回流,其硝化速率可以提高12%,反硝化速率则可以提高2.5倍.该实验结果为今后城市污水处理过程中高效脱氮打下了良好的理论和实践基础.     

通过光催化氧化提高吡啶的可生化性

难以生物降解的吡啶经过光催化氧化之后,其结构发生变化,由不能被重铬酸钾氧化变为可以被氧化,表现为其COD随着光催化氧化而升高.将吡啶作为有机碳源进行反硝化实验,结果表明:吡啶经过光催化氧化之后,相比未经过光催化氧化的吡啶,可使硝酸盐的去除率提高3.2倍.将经过30 min光催化氧化的吡啶作为有机碳源进行3h的反硝化,硝酸盐的去除率相当于加入150mg/L葡萄糖的效果.说明光催化氧化后吡啶的可生化性明显提高,同时还可实现吡啶和硝酸盐同步去除的效果.     

大麻纤维机械-生物酶联合脱胶技术

为了克服化学法脱胶对环境污染严重和单一的生物酶脱胶率低的缺点,研究了大麻纤维机械-生物酶联合脱胶技术,讨论了机械处理的次数与残胶率的关系及通过正交试验确定了酶脱胶的最优工艺参数.即果胶酶浓度8%(o.w.f.)、脱胶时间6 h、脱胶温度50℃、常压、pH=5,浴比1:15、JFC 2%.用扫描电镜(SEM)对大麻纤维机械-酶脱胶前后的表面形态进行表征.实验结果表明机械-生物酶联合脱胶比单独的酶脱胶效果要好,脱胶后大麻纤维的残胶率为20.4%,比单独酶脱胶下降了8%左右.     

还原法制备超细银粉

文章用还原法制备单质银,研究分散剂及还原剂的不同用量对银粒粒径,粒度分布及产率的影响.