pH诱导两性离子配体修饰的金溶胶的浓缩与保存

研究了两性离子配体修饰的金纳米颗粒在酸性和碱性溶液中的稳定性和可逆聚集性. 测量了金溶胶在不同条件下的UV-Vis 吸收光谱, 通过光谱的变化揭示其稳定性和可逆聚集性. 结果表明: 经配体修饰的金纳米颗粒在酸性和碱性溶液中的稳定性有了很大的提高; 强酸性条件可诱导金溶胶失稳聚沉, 回调pH值又可使其重新分散. 利用这种pH依赖的可逆聚集特性, 可以将稀溶胶浓缩成浓溶胶或固体保存, 一旦需要又可加水恢复到分散的状态.     

纸质文献脱酸加固剂的开发及其应用研究

纸质文献在长期保存过程中会逐渐老化,并伴随纸张酸化和机械强度下降。为达到纸张脱酸的同时增强纸张机械强度的目的,本文对纸张脱酸加固剂的开发及其应用进行了研究。四硼酸钠(脱酸剂)和季铵型阳离子淀粉(加固剂)按一定比例进行配比,通过浸泡法对样品纸张进行处理。研究了脱酸剂、加固剂和脱酸加固剂对纸张表面pH值、机械强度、平整度与油墨、白度和表面显微结构的影响,同时也研究了加固剂的热稳定性。结果表明,用脱酸加固剂处理后纸张的pH值能维持在7.0~8.5范围内,纸张纤维缝隙得到填充,机械强度整体增强;纸张油墨无明显褪色现象,且纸张泛黄现象有所减轻;脱酸加固处理后的纸张经过压平后基本能恢复平整;加固剂的热稳定性良好,耐酸碱能力增强。结论:利用制备的四硼酸钠-季铵型阳离子淀粉脱酸加固剂对纸张进行处理,达到纸张脱酸的同时,也能增强纸张机械强度的目的。     

纸张与纸质文物脱酸材料近期研究与展望

纸张和纸质文物是书写和保存信息的主要载体,具有重要的价值.酸化降解是纸张目前面临的主要问题之一,脱酸处理是减缓纸张酸化降解速率和延长纸张保存寿命的有效手段.因此,安全有效脱酸材料的开发与使用已成为纸张脱酸研究必不可少的方面.通常,氨基/胺类化合物、镁/钙等的碱性化合物因其纸张相容性好、碱性适宜、成本低且安全低毒被认为是较为优良的纸张脱酸材料.本综述总结了近年来液相脱酸法中常用脱酸材料的研究进展,包括脱酸材料的分类、制备方法以及纸张脱酸效果与材料结构之间的关系.最后,讨论了脱酸材料面临的挑战与发展.     

纸张物证的分析检验方法

纸张是犯罪现场经常出现的物证。对纸张物证的分析检验在案件侦破中有着重要作用,因此,法庭科学工作者一直对纸张物证的检验方法进行深入研究。随着法庭科学实验室的发展,纸张的检验技术得到了长足的进步,由传统的单一仪器分析方法发展到现在多种分析技术的联合应用,从而建立了快速、有效、灵敏的检验方法,为涉及纸张物证的案件侦破做出了显著的贡献。本文对纸张物证的分析检验方法进行了介绍和讨论。     

纸张中烷基烯酮二聚体分析方法的研究进展

烷基烯酮二聚体是国内外广泛使用的造纸施胶剂,研究其分析方法对于鉴定纸张种类和推断纸张形成年代具有重要意义。基于此,介绍了纸张中烷基烯酮二聚体的研究现状,从溶剂提取、色谱法、光谱法、质谱法及其联用技术等方面综述了纸张中烷基烯酮二聚体分析方法的研究进展,并对其进行了展望,以期为法庭科学领域的纸张成分检验研究提供参考(引用文献28篇)。     

用荧光光谱双总体t检验法鉴别纸张

本文用荧光分光光度法对纸张的荧光特性进行了研究。根据其激发光谱、发射光谱和二阶导数光谱的特性,鉴别了部分外观相近不同种类的纸张。特别将数理统计中的“假设检验”理论对纸张的荧光强度进行ｔ检验处理,提出了分辨率,为纸张的进一步认定提供了科学依据。     

谷朊蛋白的改性及其作为纸张增强剂的性能

采用廉价可生物降解的小麦谷朊蛋白为原料,经过羟甲基化和阳离子化改性合成类似聚酰胺聚胺环氧氯丙烷(PPE)的纸张增强剂. 经改性后,谷朊蛋白带有氮杂环丁烷结构、表氯醇和环氧基团3种功能基团,可与纤维形成共价键,且能发生自身交联,在纤维周围形成三维交联网络结构,提高纸张干、湿强度. 通过单因素试验,研究了甲醛、甲酸、温度、反应时间和环氧氯丙烷5种反应因素对纸张强度的影响. 优化合成条件下制备改性谷朊蛋白可使纸张干抗张强度提高35%,湿强保留率达20%. 改性后谷朊蛋白显阳离子性,加入纸浆中,可使得浆料体系Zeta电位升高,改善浆料的留着率,明显提高纸张强度. 结果表明,经羟甲基化和环氧氯丙烷加成改性的谷朊蛋白可以作为纸张的干强剂和湿强剂.     

基于纳米尺寸低聚硅倍半氧烷潜香体的合成、表征及其香料醛分子缓释性能研究

在功能性香精与香料的应用中,香气怡人与留香持久是需要长期挑战的目标.为了达到该目标,通过形成可切断的共价键来实现香料的缓释留香是有效的途径之一.基于此,本文合成了一系列基于纳米尺寸的低聚硅倍半氧烷(POSS)基体、缩醛结构作为键链的纳米潜香体.该类潜香体在温和条件下能够缓慢地释放香料醛分子.模拟仿生的酸性环境条件,研究了pH对潜香体释放香料分子的影响,发现酸性强弱对香料分子的释放有着重要的关系, pH值也与缩醛键链接的化学键的断裂成正相关关系.在弱酸环境中,释放相对较慢,达到释放平衡的时间相对较长,具有优异缓释的效果.此外,利用该类新颖的潜香体对丝绸、纸张进行负载,并研究了仿生环境下的香料醛分子的释放,与单纯香料醛分子对照样进行了对比和讨论.     

薄层色谱-分光光度法测定纸张中单糖的研究

建立了薄层色谱-紫外可见分光光度法测定纸张样品水解液中单糖组成的方法。纸张样品水解后点样在以丙酮处理过的硅胶G薄层板上,以正丁醇∶乙酸乙酯∶异丙醇∶乙酸∶吡啶∶水=7∶20∶12∶7∶6∶5(体积比)为展开剂,以苯胺-草酸为显色剂,测定了单糖的Rf值。以1-萘酚为显色剂,测定了纸张样品水解液中的单糖含量,方法的线性关系较好,5种单糖的样品加标回收率为96.10%~98.18%。该方法分离效果好,操作简便,可用于纸张样品水解液中5种单糖的同时测定,从而为法庭科学中纸张的检验提供依据。     

手持式差分拉曼光谱对纸张物证的分类研究

为建立一种简单、快速、高效、无损的鉴别不同种类纸张物证的方法,利用手持式差分拉曼光谱对收集到的43个不同种类、不同用途的纸张物证进行检验。根据纸张物证中填料的拉曼特征峰对样品进行分类,并结合聚类分析对实验数据进行处理。结果表明:当组间距离为7时,样本可分为5类,分类效果较好。该方法简便快速,结果准确可靠,为公安实际工作中纸张物证的分类鉴别提供思路。     

Chromatographic analyses of tocopherols and tocotrienols in palm oil

Analyses of tocols (tocopherols and tocotrienols) in palm oil have been extensively reported in the past. However, due to the scarcity of individual tocotrienol standards, calibrations have mostly been carried out using only α-tocopherol as standard. Moreover, even if the individual tocotrienols are being used, their reliability is often questioned, because tocotrienols are highly susceptible to oxidation and deterioration. This paper reports on the study of the deterioration rate of individual tocotrienol standards upon storage as well as different calibration methods for the tocols in palm oil.     

Evaluation of acidic paper deterioration in library materials by pyrolysis-gas chromatography

Pyrolysis-gas chromatography (Py-GC) has been applied to the evaluation of the deteriorated acidic paper in old books. A tiny piece (ca. 0.25 mg) of deteriorated paper was subjected to Py-GC measurement at 300 °C pyrolysis temperature. Levoglucosan and its dehydrated form levoglucosenone were typical degradation products while a recent control paper gave rise mainly to levoglucosan. The relative yield of levoglucosenone was much higher for the paper sample taken at the heavily deteriorated marginal part than that in the center of the same page of the old book. Accordingly, levoglucosenone observed in the pyrogram can be used as a marker to evaluate the degree of the deterioration of the acidic paper. The formation of levoglucosenone can be attributed to the slow deterioration process of paper, in which dehydration reaction play an important roll accompanied by the chain scission of cellulose. The Py-GC method for paper evaluation was also applied to clarify the effect of storage conditions and chemical compositions of paper materials to their deterioration processes.     

Effect of selected natural dyes in reduction on colour changes of Egyptian linen textiles by fungi

Linen is the most historical Egyptian textile fibre liable to fungal deterioration. Fungal deterioration of dyed linen textiles may appear as undesirable different stains. In order to success in removing of fungal stains from biodeteriorated historical Egyptian dyed linen textiles, it is necessary to understand the nature and causes of these stains, hence their subsequent removal. So this paper aims to investigate the effect of fungi on dyed linen textiles. In this study linen textile samples were experimentally dyed by two different dyes, blue one as an example to vat dye and yellow one as an example to direct dye. This work is done on two of the most important dyes (Turmeric and indigo), which were popular in most of historical periods in Egypt. Dyed linen samples were experimentally biodegraded by thirty different fungal strains isolated previously from historical Egyptian linen samples. The produced change in colours of the biodeteriorated samples was detected visually. Also, the change in reflection spectra and colour differences produced to dyed linen textiles after fungal deterioration, were assessed and evaluated by using spectrophotometer. This study reported that most of tested fungi contribute to discoloration of all tested dyed linen samples. These results indicate that most of stains on historical Egyptian dyed linen textiles, may be fungal stains. The results confirm that undyed linen textiles more liable to fungal biodeterioration than dyed ones. Also the results show that yellow dyed linen textiles are more susceptible to fungal deterioration than blue dyed linen textiles. The obtained results show that Alternaria tenuissima, Chaetomium globosum, Chaetomium sp., Penicillium raistrickii, P. soppi, P. asperum, P. citrinum, Aspergillus carbonarius, A. fischeri, A. nidulans, A. terreus and A. niger, had showed the maximum colour changes of the deteriorated yellow dyed linen samples. The results also show that Alternaria tenuissima, Chaetomium sp., Penicillium asperum, P. citrinum, Aspergillus nidulans and A. spinulosus, had shown the maximum colour changes of the deteriorated blue dyed linen samples.     

Cotton Cellulose Ageing in Sealed Vessels. Kinetic Model of Autocatalytic Depolymerization

In this paper, we propose a new kinetic model that describes the depolymerization of pure cotton cellulose, applicable to ageing experiments in sealed vessels. By recording the pH of the salt solutions used for controlling the relative humidity inside the vessels, we demonstrate that volatile acidic species are produced during the ageing of pure cellulose. Based on the proposition that the acids produced must have an autocatalytic effect on the depolymerization of cellulose, we theoretically developed equations describing the time dependence of the percentage of the broken glycosidic bonds, the folding endurance, tensile strength, tensile energy absorption, stretch at break and the L* and b* coordinates of the CIEL*a*b* color system. The experimentally determined values of these pure cellulose paper properties were fit into the model equations by use of a computer statistical package. The very high values of the regression coefficients indicate that the model equations work quite well. The experimental data and the model equations indicate that for long ageing times (up to 150 days at 80 °C), the deterioration of the sample properties accelerates and finally brings about an abrupt breakdown of the samples. Under the light of these findings, we believe that the useful life of the historical paper stored in archives and libraries is less than predicted by the existing models, and steps for its preservation should be taken immediately. As an additional preservation measure, we propose the ventilation of the storage areas so that the volatile acidic products of paper deterioration that accelerate its ageing are removed.     

The significance of water chemistry in wet plant operation

The use of cobalt radiation sources in a wet storage environment requires care in the control of thet environment to avoid the potential for deterioration of the steel. This paper describes the factors which are important and recommends a set of water quality conditions. It also describes the measures which PURIDEC has taken to monitor the performance of product in service and outlines some of the results from that surveillance programme.     

Development of a multi-sample micro UV irradiator for accelerated deterioration of polymers

The authors previously developed a pyrolysis-gas chromatograph/mass spectrometry (Py-GC/MS) system incorporating a micro ultraviolet (UV) irradiator which allowed more rapid deterioration of polymeric materials compared to outdoor exposure tests and various accelerated weathering test methods such as weather meters. The micro UV irradiator, however, could handle only a single sample at a time. To achieve multi-sample deterioration in a short time, herein a new UV irradiator was developed by which up to 18 samples on a rotatable sample cup holder can be simultaneously deteriorated at a desired temperature under UV irradiation. The basic performance of the irradiator is evaluated in terms of the rate and reproducibility of accelerated deterioration by using high impact polystyrene (HIPS) as the test sample. The HIPS samples before and after deterioration are subjected to evolved gas analysis-mass spectrometry (EGA-MS) focusing on the changes in the peak width observed in the thermograms. High precision in the peak width measurements among the samples irradiated at various positions on the rotatable sample cup holder is observed with RSD values less than 4.3%. The newly developed irradiator for multi-samples requires a six times longer period to accomplish a comparable deterioration level than the previously developed irradiator. This lengthening can be attributed to the difference in the light intensities of both irradiators at the sample position. However, the relationship between the peak width and the irradiation time has similar profiles for both irradiators. This similarity indicates a good correlation of data measured by both irradiators.     

An application of hypergeometric distribution theory to competitive processes at deteriorating electrode surfaces

The hypergeometric distribution of probability theory is employed to predict the effect of surface deterioration on electrode behaviour in the presence of two competitive processes. The approach, carrying numerical illustrations, assumes that only the total number of deteriorating active centre clusters is known, but not their fractions supporting individual processes. The temporal variation of the computed probability of process-prevalence, independent of the deterioration mechanism, maps the history of surface efficiency, if the kinetics of deterioration is known.     

化学计量学中的稳健估计方法

稳健统计学是八十年未才基本定型的统计学分支，它是针对实际情况中假设模型常常只是对实际数据的一种近似而导致传统统计学推断失误而发展起来的。稳健统计学构造一些新的具有稳健性的方法，使得在假设模型满足时，稳健方法具有接近最优的性能；在实际数据与假设模型有差别时，其性能仍为次优的；而在实际数据与假设模型差别大时，统计方法的性能也不会变得过差。本文介绍了稳健估计的一般概念。综述了化学计量学中的稳健估计方法，     

The discovery of free radicals in ancient silk textiles

Protection of ancient silk textiles from further deterioration is of vital importance to the investigation and preservation of ancient Chinese culture. Ancient silk textiles from several different ages (more than 2000 years ago) and regions were studied by means of Raman and electron paramagnetic resonance (EPR) spectroscopy in an attempt to unveil the deterioration mechanism of silk. The Raman spectra showed two peaks (D and G), which are indicative of carbonization. The EPR spectra of the ancient samples showed a characteristic sharp absorption centered at g∼2.0037 without a hyperfine structure, and have been identified as those of carbon radicals. These free radicals had not been discovered in ancient silk fabrics before, and the discovery may shed light on the deterioration mechanisms of ancient silk textiles.