黄土高原植物根系提高土壤抗冲性机制初步研究

本文首次定量描述了乔灌草根系影响土壤水力学及物理性质的效应及其与根系提高土壤抗冲性作用的关系,探讨了根系提高土壤抗冲性的主导因素,建立了根系提高土壤抗冲性的数学模型,该模型的建立不仅对于阐明根系提高土壤抗冲性机制具有重要理论意义,而且用它估算林草地根系提高土壤抗冲性的作用具有很高精度,计算值与实测值平均最大偏差不超过1.417s/g。     

化学教学中加强学生元认知能力的实验研究

学生元认知能力的高低进接影响其学习的质量和效率.教学实验表明在高中化学教学中应用元认知教学能提高学生的元认知能力、有效地控制学习分化、提高学生的化学学业成绩.实验说明,在教学中提高学生的元认知能力,对中等生、学困生的学习成绩的提高,效果特别显著.     

碳纤维的抗氧化处理

用硼化合物对碳纤维进行抗氧化处理,提高了纤维的高温抗氧化性能。用热分析、电子显显微镜、表面电子能谱和X射线衍射等进行了研究,结果表明:碳纤维经过硼化合物处理后,氧化活化能提高123.4%,热氧化分解点提高268℃,高温使用寿命提高许多倍,但物理机械性能变化不大。     

西藏将提高51个藏药品种标准

近日,国家食品药品监督管理局在拉萨召开藏药标准第二次协调会。会议的主要任务是建立藏药标准提高协调机制,统一思想、统一标准、查找问题,坚持继承、发展与创新相结合,不断提高和完善藏药标准整体水平。会议确定了今年完成114个藏药品种（药材、成药）标准提高工作,其中西藏自治区承担51个藏药品种的标准提高工作,并将成立5省（区）藏药标准协调委员会,委员会由西藏自治区食品药品监督管理局牵头,办公室设在西藏自治区食品药品监督管理局。西藏承担51个品种标准的提高     

提高化学课堂教学实效性的有效途径——良好教学策略的应用

在新课程的背景下,如何更加有效地组织教学,如何提高课堂教学的实效性,如何让每一个学生在化学的课堂上学有所成,提高学生的综合素质。从指导学生有效的学习方法,自主式、探究式学习,关注、关爱每一个学生,优化课堂教学结构等方面进行了一些探讨,以形成积极教学策略来帮助学生,提高化学课堂教学质量,提高课堂教学的实效性。     

基于课堂无线应答系统的有机化学互动教学模式探索

探索无线应答系统在有机化学课堂教学中的应用。这种课堂教学模式能提高学生对有机化学课堂教学的兴趣,促进学生主动学习,提高教师的工作效率;还可以用于了解学生的学习状况,跟踪学习进程,提高有机化学课堂教学质量。     

生物活性稀土微肥对红地球葡萄产量与品质的影响

通过田间试验,研究了生物活性稀土微肥对红地球植株性状、光合作用、葡萄产量和产品品质的影响.结果表明,一定浓度的生物活性稀土微肥可以使红地球葡萄的叶片干物质积累增加,叶片生长发育得到加强,生长状况得到改善;提高叶绿素含量和光合速率;提高红地球葡萄的单粒重、果穗重,提高红地球葡萄的产量,增产效果达到显著水平;红地球葡萄果实含糖量与Vc含量也有显著提高,改善了果品质量.     

开缝石英管原子化技术的改进

近年来,为提高火焰原子吸收光谱法的灵敏度,先后研究过水冷石英管和开缝石英管(简称缝管)原子化技术.前者使灵敏度提高1～2个数量级^[1～3],后者只提高几倍^[4～6].缝管技术比水冷石英管技术的装置简单,操作方便快速,但因其灵敏度不高,应用受到限制.本文以镉为例,探讨了提高缝管技术灵敏度的途径.     

空心玻璃微珠复合聚酰亚胺泡沫的泡孔结构与性能

通过填充空心玻璃微珠,采用预聚法制备了空心玻璃微珠复合聚酰亚胺泡沫,研究了空心玻璃微珠填充量对复合聚酰亚胺泡沫的泡孔结构、热性能和压缩性能的影响规律。结果表明,随着空心玻璃微珠填充量的增加,聚酰亚胺泡沫泡孔结构变得精细,并且热稳定性、玻璃化转变温度和压缩性能都随之提高。当填充量(空心玻璃微珠与均苯四甲酸酐的质量比)达到20%时,泡沫5%热失重温度提高了13.9℃,玻璃化转变温度提高了8.1℃,压缩强度提高了约21%,压缩模量提高了约12%。     

中学化学人文教育的实验

新一轮课程改革把学科中的人文教育作为重要的目标提了出来,随着对化学人文教育的深入研究,文章提出了围绕人文读物的自主阅读综合实践的形式来开展中学化学人文教育,学生人文教育的成效通过读书报告来进行交流和评价.通过实验,中学化学人文教育在提高学生对化学认识、提高学生的化学成绩、提高学生的化学专业选择率及提高学生的综合能力等方面发挥了积极作用.     

水溶性硅油对超临界CO_2介质中丙烯酸聚合反应的影响

：通过对水溶性硅油浓度的改变，研究其对超临界CO2介质中丙烯酸聚合反应的影响。研究表明水溶性硅油可起到分子量调节剂的作用。随着硅油的加入，产物分子量降低，但当硅油浓度过大时，由于硅油在超临界CO2中溶解度的限制，夹带单体聚沉在反应釜底部形成富单体相，分子量有所上升。此外，扫描电镜照片（SEM）显示不同浓度的水溶性硅油对聚丙烯酸分子形态的影响不同，硅油含量越大，聚丙烯酸分子粒径越小，分子量分布越均匀。     

Fabric phase sorptive extraction: An innovative sample preparation approach applied to the analysis of specific migration from food packaging

Additives added to food packaging materials can migrate to food in contact with them during storage and shelf life. A novel simple, fast and sensitive analyte extraction method based on fabric phase sorptive extraction (FPSE), followed by analysis using ultra-high performance liquid chromatography and mass spectrometry detection (UPLC-MS) was applied to the analysis of 18 common non-volatile plastic additives. Three FPSE media coated with different sol-gel sorbents characterized with different polarities including sol-gel poly(dimethylsiloxane), sol-gel poly(ethylene glycol) and sol-gel poly(tetrahydrofuran) were studied. All three FPSE media showed very satisfactory results. In general, compounds with low logP values seemed to have higher enrichment factors (EFs), especially with poly(tetrahydrofuran) and poly(ethylene glycol) media. For compounds with high logP values, the use of sol-gel poly(dimethylsiloxane) improved the enrichment capacity. Sample preparation time was optimized at 20 min for sample extraction and 10 min for solvent desorption. Acetonitrile was selected as desorption solvent since recoveries were over 70% for 13 out of 18 selected compounds in all FPSE media. The best extraction recovery values were obtained when compounds were dissolved in aqueous acetic acid solution (3%), where 17 out of 18 compounds showed improvement in their signal intensity after FPSE extraction and 10 obtained enrichment factors above 3 for all the tested FPSE media. When FPSE extracts were concentrated under nitrogen, 11 out of 18 compounds reached EFs values above 100.     

Phase equilibria of poly(ɛ-caprolactone)-<Emphasis Type="Italic">co</Emphasis>-poly(acryl methacrylate)-methylene chloride systems and the phase structure of polymer binary mixtures

Isothermal cross sections of amorphous separation diagrams of the ternary systems poly(ɛ-caprolactone)-co-poly(acryl methacrylate) Eudragite RS-methylene chloride and poly(ɛ-caprolactone)-co-poly(acryl methacrylate) Eudragite E-methylene chloride are obtained via the experimental methods of turbidity points and analytical transmission electron microscopy and the calculation semi-empirical method of constructing boundary lines of phase diagrams. It is shown that the composition of copoly(acryl methacrylate) affects the length of the solubility region in the ternary phase diagram and the character of the anisotropy of films prepared via solvent evaporation. The determination of coordinates of figurative points corresponding to the completion of phase separation shows that the mechanism of phase separation for both systems is of the spinodal type. The specific orientation of polycaprolactone crystallites during film preparation from the poly(ɛ-caprolactone)-Eudragite RS mixture is determined by the morphology of the film formed during solvent evaporation and the phase composition.     

Poly(styrene‐co‐N‐methacryloyl‐l‐phenylalanine methyl ester)‐functionalized magnetic nanoparticles as sorbents for the analysis of sodium benzoate in beverages

In this study, poly(styrene‐co‐N‐methacryloyl‐l ‐phenylalanine methyl ester)‐functionalized magnetic nanoparticles were constructed and used as magnetic solid‐phase extraction sorbents for analysis of food preservatives in beverages. To prepare the poly(amino acid)‐based sorbents, N‐methacryloyl‐l ‐phenylalanine methyl ester, and styrene served as the functional monomers and modified onto the magnetic nanoparticles via free radical polymerization. Interestingly, compared with propylparaben and potassium sorbate, the proposed poly(amino acid)‐based sorbents showed a good selectivity to sodium benzoate. The adsorption capacity of the sorbents to sodium benzoate was 6.08 ± 0.31 mg/g. Moreover, the fast adsorption equilibrium could be reached within 5 min. Further, the resultant poly(amino acid)‐based sorbents were applied in the analysis of sodium benzoate in real beverage samples. The results proved that the proposed magnetic solid‐phase extraction sorbents have a great potential for the analysis of preservatives in food samples.     

Phytochemical analysis and Enzyme Inhibition Assay of Aerva javanica for Ulcer

ABSTRACT: BACKGROUND: Aerva javanica (Burm. f.) Juss. ex Schult. (Amaranthacea) is traditionally used for the treatment of wound healings, cough, diarrhoea, ulcer and hyperglycaemia. The current study was aimed to fractionate and isolate bioactive compounds and ultimately to evaluate their anti-ulcereogenic potential. RESULTS: In order to achieve these aims, the fractionation, purifications and then biological potential determination of the isolated compounds was carried out. For purification purpose, initially extraction of the plant material was done with aqueous MeOH in the order of increasing polarity by using solvent-solvent extraction method. Phytochemical analysis revealed the presence of three compounds, 3-hydroxy-4 methoxybenzaldehyde (1), ursolic acid (2) and (E)-N-(4-hydroxy-3-methoxyphenethyl)-3-(4-hydroxy-3-ethoxyphenyl) acryl amide (3). Inhibition of urease activity of various fractions revealed that ethyl acetate fraction showed significant activity (P <0.05) as compared to other fractions. (E)-N-(4-hydroxy-3- methoxyphenethyl)-3-(4-hydroxy-3-ethoxyphenyl) acryl amide (3) showed marked anti ulcer activity (P <0.05). CONCLUSION: These results suggested the mild potential of A. javanica against ulcer.     

Temperature-responsive stationary phase utilizing a polymer of proline derivative for hydrophobic interaction chromatography using an aqueous mobile phase

A new method of chromatography is proposed, utilizing a thermo-responsive polymer carrying an amino acid ester residue for the stationary phase of high-performance liquid chromatography (HPLC). We have been investigating the new concept of chromatography, a temperature-responsive chromatography, using temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm)-modified surface for HPLC with a constant aqueous media as the mobile phase. In this study, we designed and synthesized thermo-responsive poly(acryloyl-L-proline methyl ester) and its copolymer with N-isopropylacrylamide (NIPAAm). Homopolymers of acryloyl-L-proline methyl ester and copolymer were prepared by the reaction of radical telomerization. These polymers underwent a reversible phase transition from water-soluble forms into aggregates by changing the temperature, similar to PNIPAAm. The surface properties and functions of stationary phases modified with poly(acryloyl-L-proline methyl ester) were controlled by the external temperature. In the chromatographic system, we separated steroids and amino acids with a variety of hydrophobicities using a sole aqueous mobile phase. In contrast to a PNIPAAm-modified surface, a poly(acryloyl-L-proline methyl ester)-modified surface showed a greater affinity for hydrophobic amino acids.     

Microwave‐assisted preparation of poly(ionic liquids)‐modified magnetic nanoparticles for pesticide extraction

Novel poly(ionic liquids) were synthesized and immobilized on prepared magnetic nanoparticles, which were used to extract pesticides from fruit and vegetable samples by dispersive solid‐phase extraction prior to high‐performance liquid chromatography analysis. Compared with monomeric ionic liquids, poly(ionic liquids) have a larger effective contact area and higher viscosity, so they can achieve higher extraction efficiency and be used repeatedly without a decrease in analyte recovery. The immobilized poly(ionic liquids) were rapidly separated from the sample matrix, providing a simple approach for sample pretreatment. The nature and volume of the desorption solvent and amount of poly(ionic liquid)‐modified magnetic material were optimized for the extraction process. Under optimum conditions, calibration curves were linear (R² > 0.9988) for pesticide concentrations in the range of 0.100–10.000 μg/L. The relative standard deviations for repeated determinations of the four analytes were 2.29–3.31%. The limits of detection and quantification were 0.29–0.88 and 0.97–2.93 μg/L, respectively. Our results demonstrate that the developed poly(ionic liquid)‐modified material is an effective absorbent to extract pesticides from fruit and vegetable samples.     

Study of cryostructurization of polymer systems

Summary A possibility of obtaining insoluble gels with the help of freezing-thawing procedures was demonstrated on an example of aqueous solutions of a thiol-containing poly(acryl amide) derivative. The gel formation was proved to occur as a result of oxidation of free SH groups of polymer chains by water-dissolved air oxygen.     

Solid phase micro-extraction of metal ions

A fused silica fibre coated with poly(dimethylsiloxane) was modified to produce a micro probe with ion exchanging capability. The liquid ion exchanger, di-(2-ethylhexyl)phosphoric acid (HDEHP), was used for the modification. The probe was used for the extraction of bismuth(III) from aqueous nitric acid solution. The extracted Bi(III) was desorbed into an acidic potassium iodide solution. The yellow colored BiI₄ ^– complex formed was determined by spectrophotometry.     

Development of new polar monolithic coatings for stir bar sorptive extraction

Polar vinyl monomers have been used for the synthesis of several polymer monoliths, to serve as novel coatings for stir bar sorptive extraction; the monovinyl monomers 2‐hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) monomethacrylate) (PEGMA) were copolymerized with (apolar) divinylbenzene (DVB) and/or pentaerythritol triacrylate (PETRA), both of which are cross‐linking agents. After the optimization of the most important synthesis parameters, which included the ratio between total monomers and porogen, the nature of the porogen, and the monomer ratios, inter alia, three mechanically stable, polar monolithic coatings for stir bar sorptive extraction were obtained that were based on poly(HEMA‐co‐DVB), poly(HEMA‐co‐PETRA), and poly(PEGMA‐co‐PETRA). Thereafter, and in order to evaluate the hydrophilicity of the resulting monoliths, they were applied as materials in the stir bar sorptive extraction of a group of emerging pollutants with a wide range of polarities. The results showed that both the poly(HEMA‐co‐DVB) and poly(PEGMA‐co‐PETRA) materials could be used to extract both polar and nonpolar compounds by stir bar sorptive extraction, in an effective manner. Taking into account the desired chemical and morphological properties, as well as the extraction efficiencies, the poly(PEGMA‐co‐PETRA) material seemed to be a particularly promising monolith for application as a novel coating in stir bar sorptive extraction.