Cellulose degradation in the Vasa: The role of acids and rust

Abstract

The oak timbers of the Swedish warship Vasa are deteriorating. High amounts of oxalic acid have been found along with a low pH and low molecular weight cellulose deep in the wood timbers. The iron-rich surface wood differs from the interior wood in that it displays higher pH and cellulose with higher molecular weight. The objective of this study was to determine why there is a difference in cellulose degradation, pH, and oxalic acid amount between the surface region and the interior of the Vasa timbers. Analysis of cellulose weight average molecular weight by size exclusion chromatography was performed, as well as quantification of oxalic acid and iron by high-performance anion exchange chromatography and atomic emission spectroscopy, respectively. It was found that a decrease in iron content coincides with an increase in oxalic acid concentration and a drop in pH at a certain depth from the wood surface. When iron-rich surface wood samples from the Vasa were mixed with an aqueous solution of oxalic acid, a fast increase of pH over time was observed. Neither interior wood poor in iron nor the fresh oak reference showed the same neutralizing effect during the time of measurement. This indicates that the presence of iron (rust) causes a neutralization of the wood, through the formation of iron(III) oxalato complexes, thus protecting the wood from oxalic acid hydrolysis. This effect was not observed to the same extent for other acids observed in Vasa wood (sulfuric, formic, glycolic, and acetic acids).     

河蚬蛋白酶法水解工艺的研究

以河蚬为原料,水解度和氮收率为指标,筛选出适合河蚬酶解的蛋白酶,利用二次回归正交旋转组合试验建立水解度与加酶量、酶解温度、酶解时间的数学回归模型,确定河蚬蛋白酶法水解的最佳工艺条件为：液固比3：1,混合酶（Neutrase／Alcalase）组合比例3：1,pH值7．O,加酶量1．3％。酶解温度53℃,酶解时间261rain,此时水解度为46．1％,氮收率81．2％．     

鸭蛋清酶水解及其水解物对免疫功能的影响

用碱性蛋白酶和动物蛋白水解复合酶水解经酒精酵母脱糖后的鸭蛋清,并用正交试验确定了动物蛋白水解复合酶的最佳水解条件.结果表明,鸭蛋清浓度5%,动物蛋白水解复合酶用量(E/S)0.7%,pH8.0,反应温度54℃,反应时间4 h时水解效果最佳,水解度达92.65%.其水解物无需脱苦、脱盐和脱色.动物试验表明蛋清水解物能显著提高小鼠红细胞C3b受体花环率.而其红细胞免疫复合物花环率没有显著变化.说明蛋清水解物能在一定程度上增强小鼠红细胞免疫功能.     

Phase Diagram of the System KCl-CsBr-CaBr_2

1 IntroductionWith the develOPment of the molten salt fuel cell,the use of the phase diagram becomes more and moreextensive. A great help will be gained by using acomputer to predict the relative Parts of the Phasediagram because it is quite difficult for many Phasediagrams tO be determined. The Phase diagram ofCsBr-CaBrZ was Predicted which is the complexcompoUnd-forming system[']. This comPOund has notbeen reported up tO now in lit~. The Phasediagrams of the q~ibinny system CsBr-Ca…     

弱酸弱碱盐溶液中氢离子浓度计算的探讨

导出了弱酸弱碱盐溶液中氢离子浓度应满足方程式[H ] 4 (C0 Ka KwKb) [H ] 3 (Kw×KaKb-Kw) [H ] 2 - (KaKw K2 wKb KwKaC0Kb) [H ] - K2 wKaKb=0利用Mathcad工具软件求得了NH4CN溶液中不同初始浓度时的氢离子浓度 .结果表明 ,Ka≈Kb 时 ,浓度的改变对氢离子浓度的影响不大 ,可用近似公式计算 :当Ka 和Kb 差别较大 ,C0 >0 .0 0 0 5mol·L- 1 时 ,可用近似公式求解氢离子浓度 ,溶液极稀时 (C0 <0 .0 0 0 5mol·L- 1 ) ,用近似公式求得的氢离子浓度与实际结果差别较大 ,近似公式不再适用     

非水溶剂和非水溶剂化学的特性及应用进展

非水溶剂具有水所没有的特性．在非水溶剂中可以得到与在水中不同的反应结果．许多不能够在水中发生的化学反应，在非水溶剂中却可以发生或者向相反的方向进行；非水溶剂在制备无水盐，制备某些异常氧化态的特殊配合物，改变某些反应的速度，改进工艺，提高产率等方面都具有重要的意义。     

植物耐盐性的信号传导途径及基因工程进展

就近几年来植物耐盐方面的研究热点如植物耐盐信号传导途径及植物耐盐基因工程进展等方面作了综述。     

植物金属硫蛋白及其在自由基清除中的作用

金属硫蛋白是一种诱导表达蛋白，是很好的羟自由基清除蛋白，其清除能力主要来源于蛋白中处于还原态的巯基．     

甲醛法测定铵盐中总氮含量的有关问题讨论

对用甲醛法测定铵盐中总氮含量的测定原理、含量计算、以及实验注意条件等进行讨论，确保实验成功，提高样品测定结果的准确度．     

深井冻结凿井冻结管断裂原因分析及防治技术

在冻结法凿井中,因局部冻结管断裂,造成盐水泄漏,会引起连锁断管反应,降低冻结壁强度,威胁冻结凿井安全,如何防止冻结管断裂或在局部断管后如何采取有效的补救措施避免事故的进一步扩大,是冻结法凿井施工中的技术难题;在冻结管断裂原因、防止冻结管断裂和处理冻结管断裂技术等方面进行了具体分析,供类似深井冻结法施工参考。