酸碱正负理论的发展——轨道酸碱     

赵世龙  赵在其 《雁北师范学院学报》1994,(2)

本文认为物质的低能空轨道在共价范围内有正电性是酸,高能电子占有轨道在共价范围内有负电性是碱.按此观点所有的化学反应都是酸碱反应,并向强酸与强碱反应生成盐的方向进行.盐又分成分子型盐和离子型盐,按酸轨道与碱轨道中和生成化学键,得到分子型盐的结构;离子型盐的晶体结构仍按半径比规则来确定.  相似文献   

Comparison of oil and egg tempera paint systems using time-of-flight secondary ion mass spectrometry     

Zachary E. Voras  Kristin deGhetaldi  Brian Baade  Eric Gordon  Glenn Gates  Thomas P. Beebe 《文物保护研究》2016,61(4):222-235

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is quickly becoming a critical tool in the field of art conservation. This technique provides high-resolution spatial maps of both inorganic and organic components located within cross-sectional samples collected from works of art. With recent advances in surface analysis, ToF-SIMS can now be used to identify specific amino acids present in protein-containing materials as well as fatty acids in drying oils. For example, the detection of the ion fragment associated with the amino acid hydroxyproline can be used to confirm the use of animal glue in a paint sample. As an analytical technique, ToF-SIMS avoids the need for derivatization/silylation reagents, with no interference by the presence of pigments. Furthermore, the layered systems that are often encountered in historical paint samples remain intact throughout the analytical procedure. This allows for the co-localization of organic and inorganic species in specific layers (e.g. egg yolk paint atop a glue ground). Because of this ability to localize the analytical signal to approximately 6?µm or less, the mass spectral information can be used to produce mass-resolved and spatially-resolve images which can be correlated to previous studies of the same samples. In this study, ToF-SIMS was used to analyze a paint cross section obtained from a painting attributed to Raphael, and another from a painting by the Sienese artist Matteo di Giovanni.  相似文献   

磺基水杨酸铜络离子稳定常数的测定     

陶果  曾琪 《四川职业技术学院学报》2006,16(4):118-119

本文采用pH电位滴定法测定磺基水杨酸铜络离子的稳定常数,得到了比较准确的结果(与文献值比较)。该法适用于弱酸根离子或弱碱分子作配位体的单核络合物稳定常数的测定。  相似文献   

浅析叙事性手法在青少年科教节目中的应用——以《酸雨》为例     

梁静 《现代教育技术》2011,21(4):66-71

青少年科教电视节目是青少年了解世界、学习知识的重要渠道,是对青少年进行科普教育的重要途径。运用案例研究法,以自制短片《酸雨》为例,研究叙事性手法在青少年科教电视节目中的应用,提出多样化创作思路,丰富同类电视节目创作的表现手法。  相似文献   

NaCl胁迫下水杨酸浸种对水稻幼苗生长的影响   总被引：1，自引：0，他引：1  

叶梅荣 《安徽科技学院学报》2002,16(4):44-46

本试验对稻种进行不同浓度的水杨酸浸泡处理,采用琼脂培养法,在50mmol/LNaCl胁迫下对水稻进行培养.水稻三叶一心期测量各项生理指标.结果表明:水杨酸浸种处理与空白对照相比较,水稻幼苗叶绿素含量增加,过氧化物酶活性提高,电导率降低,丙二醛含量降低.不同的水杨酸处理浓度相互比较,得出:0.1g/L的水杨酸处理浓度在50mmol/L NaCl胁迫下,能够最有效地提高水稻幼苗的抗性.  相似文献   

利用具有keggin结构硅钨酸还原Cr（Ⅵ）制备CrPO_4纳米粉体     

张宝成  沈玉华  谢安建 《宜春学院学报》2011,33(8)

以具有Keggin结构硅钨酸为光催化还原剂,用光致还原Cr2O72-的方法制备了磷酸铬纳米粉体,Cr2O72-的还原过程用紫外-可见光谱进行监测。通过红外光谱（FT-IR）、X射线衍射（XRD）、扫描电镜（SEM）和透射电镜（TEM）分析表明所制产物为无定形磷酸铬,具有较规则的球形结构,平均粒径约为500nm。其合成机理是：在紫外光的照射下,当存在有机化合物时,形成了还原态的硅钨酸,还原态的硅钨酸将Cr（VI）还原为Cr（Ⅲ）,与体系中的PO43-结合生成磷酸铬,由于硅钨酸与磷酸铬之间存在结合力,硅钨酸对磷酸铬纳米颗粒的形成又起到了模板的作用。  相似文献   

Excel在酸雨统计分析中的应用     

朱正勋 《黄冈职业技术学院学报》2011,13(6):96-99

将microsoft公司office系列软件Excel强大的计算、公式编辑、数据统计和绘图功能,应用在酸雨统计分析中,通过计算机自动运算和图表处理,方法简捷、快速、高效,便于从数据中分析出所需要的信息。  相似文献   

耐力运动对高脂膳食诱导的脂肪肝小鼠UCP2与Mn-SOD表达及与脂肪肝关系的研究   总被引：1，自引：0，他引：1  

马国栋  高颀 《北京体育大学学报》2007,30(12):1645-1648

目的:研究耐力运动对高脂膳食诱导的C57BL/6J脂肪肝小鼠肝脏UCP2及Mn-SOD表达与脂肪肝的关系.方法:以高脂膳食诱导的脂肪肝小鼠为模型,分析耐力运动20周后肝脏UCP2及Mn-SOD表达变化与肝脏脂肪变的关系.结果:肝脏UCP2与Mn-SOD在高脂膳食组(HS组)均显著升高;恢复正常膳食结合耐力运动20周组(RE组),Mn-SOD表达进一步升高,而UCP2表达显著降低.HS组形成明显的脂肪肝,恢复正常膳食加20周不运动组与恢复正常膳食结合20周耐力运动组脂肪肝得到明显改善,但RE组改善更为明显.结论:耐力运动可能以上调Mn-SOD表达而下调UCP2表达,达到既清除活性氧又减少肝脏线粒体ATP合成降低目的,从而保护肝脏免受过多活性氧和ATP耗尽的损伤.  相似文献   

Re-treatment of whale bones – How to extract degraded fats from weakened bones?     

《Journal of Cultural Heritage》2014,15(2):128-135

Many whale (baleen whale or toothed whale) skeletons still contain residual lipids even after an initial osteological preparation. This paper examines the different possibilities of re-treatment. Before a conservation intervention, it was necessary to determine the materials of which bones are made up. The samples were analyzed by Raman spectroscopy. Different compounds were identified: a mineral part (apatite), an organic part (collagen) and lipids. Chromatography analysis yielded a detailed composition of the lipids. It was in fact degraded fat with saturated and unsaturated fatty acids. To remove these lipids, several techniques were identified and tested: enzymatic treatments, supercritical CO₂, and green or organic solvents. Esterification catalyzed by lipases could be suitable for a degreasing treatment since the solubility of esters is higher than that of the corresponding fatty acids. The enzymatic treatment acted only on the surface and did not appear to be very efficient. The use of supercritical CO₂ was even less effective. Some green solvents can partially extract lipids but prove difficult to eliminate after treatment. The best results for degreasing were achieved using organic solvents. Different solutions were evaluated at hot or ambient temperature and in simple immersion or with agitation (Soxhlet or pulsed pressure): hexane, heptane, a mixture of hexane/isopropanol, or an azeotropic mixture of methanol/chloroform. Only the mixture of methanol/chloroform succeeded in extracting the overall fat content, but this treatment degraded the organic part of the bones. The other organic solvents extracted mainly colored fat, which generally corresponded to a weight loss of 20 to 50%. The majority of fat was extracted during the first bath. Thus the treatment selected is that of immersion in heptane at ambient temperature. The degreasing of whole bones is less effective because of the film of sticky degraded fat on the bone's surface. A pre-cleaning is necessary to eliminate this film.  相似文献   

Effect of low-dose omega-3 fatty acids substitution on blood pressure, hyperinsulinemia and dyslipidemia in Indians with essential hypertension: A pilot study     

A. Bhise  P. V. Krishnan  R. Aggarwal  M. Gaiha  J. Bhattacharjee 《Indian journal of clinical biochemistry : IJCB》2005,20(2):4-9

The present study comprised 100 patients of essential hypertension who were screened for fasting hyperinsulinemia, which was detected in 77% cases. Twenty such hyperinsulinemic cases were subjected to 4 weeks of dietary control phase followed by 6 weeks of omega-3 fatty acids substitution [either 0.6 g/d (group 1) or 1.2 g/d (group 2)]. The mean basal fasting plasma insulin levels were significantly higher (p<0.001) in patients of hypertension when compared to normal controls (126.51±80.36 and 19.35±12.61 μU/ml respectively). At the end of 4 weeks of diet control only, no significant change was observed in any parameter. After substitution of omega-3 fatty acid, a significant reduction of fasting plasma insulin levels in both group 1 (29%) and group 2 (22.8%) was observed (p<0.001). Significant reduction of systolic and diastolic blood pressure (16.4% and 25% respectively), serum cholesterol, triglycerides and low density lipoprotein was also noted in both groups (p<0.001), while high density lipoprotein increased by ∼8 mg% in both groups. Thus omega-3 fatty acid substituion in low dose along-with curtailment of dietary omega-6 fatty acid may be used as an adjunctive measure in the management of essential hypertension.  相似文献