利用^(15)NO_3^-标记法研究土壤微生物量氮的化学及生物有效性

采用加入含15N的硝态氮培养方法标记了土壤微生物量氮 ,然后利用碱解扩散法测定了标记土壤有效氮含量 ,温室培养法评价了小麦对标记的土壤微生物量氮的吸收情况。结果表明 ,碱解扩散法对土壤微生物量固持的15N的提取比率 (即提取液中15N原子百分超 /土壤15N原子百分超 )在 1 47～ 2 83之间(平均 2 0 1 ) ,碱解氮中约有 3 0 1 %～ 61 6% (平均 42 9% )来自土壤微生物固持氮。植物体15N丰度在0 749%～ 1 1 62 %之间 ,明显高于15N的自然丰度 ,表明土壤微生物固持的15N在小麦生长期间发生释放 ,为植物利用。土壤微生物固持氮对植物的有效性比率 (植物地上部分15N原子百分超 /土壤15N原子百分超 )在 3 7～ 7 1之间。可见 。

如何提高化学习题讲评课的有效性

化学习题讲评课是化学教学的一个重要环节,是加强教学的重要手段,是对教学进一步补充和完善的过程,也是使学生实现由认识→实践→再认识的思维深化、培养能力的过程。本人从三方面谈了如何切实地提高化学习题讲评课的有效性。

转变观念提高化学教学的有效性

如何优化化学课堂教学，提高化学教学的有效性，是化学教学改革的重要方向，也是素质教育的必然要求。教师在教学中要凸显学生的主体性和主动性，使教师和学生的角色发生质的改变。因此，本文对转变观念提高化学教学的有效性进行了分析研究。

浅谈初中化学有效性教学的思路和方法

寻求有效教学方法,提高初中化学的教学质量是我们每个教师教学活动的根本目标。通过多年的教学我们感到传统的教学观、学生观、教师角色和教学行为是影响教学有效性的主要原因。我们认为,在新课程理念指引下,教师的教学设计。

浅议农村化学实验教学的有效性

文章从农村学校的实验条件、农村学生的自身特点、农村教师对实验的认识几个方面阐述了促进农村化学实验教学有效性的几种措施。

核心素养背景下偏远山区学校提高化学课堂有效性的探讨

在核心素养背景下,如何提高化学课堂教学有效性是摆在山区学校化学教师面前必须要解决的首要问题。文章结合课堂教学活动中出现的问题和情况谈了一些看法。

促进化学教学有效性的核心要素“生活化、生成性、教学诊断”探究

本文从基于真实情境下的化学教学、基于生成性问题的化学教学、有效的教学诊断三个方面论述促进化学教学有效性的核心要素,结合案例进行具体说明,围绕学科教学核心要素,创设贴近生活的教学情境,利用好课堂生成性问题,并将其转化为生成性资源,对课堂教学进行有效的教学诊断,以促进学生成长,培养学生核心素养。

提高初中化学实验教学的有效性

化学作为中学阶段的一门基础性学科,在新课改的大背景下,越来越注重化学实验教学,化学实验是帮助学生们通过实验来理解抽象的概念,使学生在脑海里形成化学概念,并获得化学知识和实验技能的一种实践性课程,能培养学生的动手操作能力和思维能力,培养学生的观察力和思考力;新课改实施之后,化学实验的重视程度有了明显的提升,在课程安排、课程教学内容以及教与学的方式都有了明显的改进,只是因为新课程更注重学生的动手操作能力,对化学实验的要求也有大幅度的提高,更加注重通过实验来学习和探索化学知识。因此,为了适应教育的发展,就要尽可能多的开展化学实验教学,随着科学技术的不断进步,有资历的学校也在不断地完善化学实验设备,给学生提供好的实验设施,从各个方面来提高学生的化学素质,但是对于初中化学实验教学仍存在一些问题,本文就发现的化学实验教学的现状,提出一些合理的整改措施。

不同蓬松剂对城市污泥强制通风堆肥的影响

采用药渣和木花作为蓬松剂按体积比1∶3混合,在强制通风不足的情况下,结合每周的人工翻堆,污泥高温堆肥也可实现,高温阶段(>55℃)可维持4d。堆肥的高温使大肠杆菌数量降低4个数量级,达到国家高温堆肥卫生标准。在污泥堆制过程中,pH、VSS、有机质含量下降;但全N、P、K含量的变化与堆肥的系统条件有关。药渣堆肥在堆制35d后,种子发芽指数(GI)达50%以上,木花堆肥在堆制50d后GI达到51%。堆肥结束时,Cu、Zn、Cd在药渣堆肥中含量增加,在木花堆肥中含量减少;但其中Cu的化学有效性降低,而Zn、Cd的化学有效性提高。

作物养分的“征程”

养分从土壤中被作物根系吸收,一路要经过土壤、根系、茎秆等,最终到达叶片以生产光合产物。作物养分的“征程”通常分为3个阶段:从土壤到达根系表面;从根表移至根内;从根系转运到叶片、果实及其再利用。作物养分的“征程”能否顺利进行取决于以下条件:其一,可溶于水,呈离子态,即化学有效性;其二,能迁移到作物根系表面,即生物有效性。

Clinical usefulness of biochemical markers of liver fibrosis in patients with nonalcoholic fatty liver disease

AIM: Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease (NAFLD), and progresses to the end stage of liver disease. Biochemical markers of liver fibrosis are strongly associated with the degree of histological liver fibrosis in patients with chronic liver disease. However, data are few on the usefulness of markers in NAFLD patients. The aim of this study was to identify better noninvasive predictors of hepatic fibrosis, with special focus on markers of liver fibrosis, type VI collagen 7S domain and hyaluronic acid. METHODS: One hundred and twelve patients with histologically proven NAFLD were studied. RESULTS: The histological stage of NAFLD correlated with several clinical and biochemical variables, the extent of hepatic fibrosis and the markers of liver fibrosis were relatively strong associated. The best cutoff values to detect NASH were assessed by using receiver operating characteristic analysis: type VI collagen 75 domain ≥5.0 ng/mL, hyaluronic acid ≥43 ng/mL. Both markers had a high positive predictive value: type VI collagen 7S domain, 86% and hyaluronic acid, 92%. Diagnostic accuracies of these markers were evaluated to detect severe fibrosis. Both markers showed high negative predictive values: type VI collagen 7S domain (≥5.0 ng/mL), 84% and hyaluronic acid (≥50 ng/mL), 78%, and were significantly and independently associated with the presence of NASH or severe fibrosis by logistic regression analysis. CONCLUSION: Both markers of liver fibrosis are useful in discriminating NASH from fatty liver alone or patients with severe fibrosis from patients with non-severe fibrosis.

Fixation of Multiple Metals in Contaminated Soil by Different Passivators

The effects of 4 passivators, zeolite, lime, red mud and peanut shell biochar, on the fixation of Cd, Pb, Cu and Zn in acidic multi-metal contaminated soils were studied by passivator culture experiment in order to screen out the passivator with better fixation effects. The results showed that the soil pH values of zeolite, lime, red mud and peanut shell biochar increased significantly by 0.511.02, 0.821.29, 0.720.89 and 0.300.35 respectively. The effects of 4 passivators on the fixation of Cd and Zn in soil are lime>red mud>zeolite>peanut shell biochar. The order of effects on the fixation of Pb is red mud>lime>zeolite>peanut shell biochar. The order of the fixation effects of Cu is red mud>lime>peanut shell carbon>zeolite. The contents of Cd, Pb, Cu and Zn in the extractable state of CaCl2 decreased with the increase in the dosage of 4 passivators. Lime and red mud showed good fixation effects on Cd, Pb, Cu and Zn. The contents of Cd, Pb, Cu and Zn in the extractable state of CaCl2 at the low dosage(2.5 g/kg) of lime and red mud decreased by 41%, 84%, 76% and 83% respectively. Soil pH value was negatively correlated with CaCl2-Cd, Pb, Cu and Zn(P<0.01). Lime and red mud had significant fixation effects on Cd, Pb, Cu and Zn in acidic multi-metal contaminated soils at low application dosages.

Infrared thin layer drying of saffron(Crocus sativus L.) stigmas:Mass transfer parameters and quality assessment

Saffron is the most precious and expensive agricultural product. A dehydration treatment is necessary to convert Crocus sativus L. stigmas into saffron spice. To the best of our knowledge, no information on mass transfer parameters of saffron stigmas is available in the literature. This study aimed at investigating the moisture transfer parameters and quality attributes of saffron stigmas under infrared treatment at different temperatures（60,70, …, 110 ℃）. It was observed that the dehydration process of the samples occurred in a short accelerating rate period at the start followed by a falling rate period. The effective moisture diffusivity and convective mass transfer coefficient were determined by using the Dincer and Dost model. The diffusivity values varied from1.1103 × 10^-10m^2·s^-1to 4.1397 × 10^-10m^2·s^-1 and mass transfer coefficient varied in the range of 2.6433 × 10^-7–8.7203 × 10^-7m·s^-1. The activation energy was obtained to be 27.86 kJ·mol^-1. The quality assessment results showed that the total crocin content increased, when the temperature increased up to90 ℃ but, in higher temperatures, the amount of crocin decreased slightly. The total safranal content of the samples decreased slightly when drying temperature increased from 60 ℃ to 70 ℃ and then continuously increased up to 110 ℃. Also, the amount of picrocrocin increased from 83.1 to 93.3 as the drying temperature increased from 60 ℃ to 100 ℃.

Chemical Availability of Cd, Pb and Zn in Anthropogenically Polluted Soil: Assessing the Geochemical Reactivity and Oral Bioaccessibility

The most recent in vitro tests used to determine metal bioaccessiblility are generally time-consuming and expensive. This study aimed at determining potential relationships between the concentrations of metals extracted using single-extraction methods and the concentrations of bioaccessible metals assessed by a harmonised in vitro test, the Unified BARGE Method （UBM）. A total number of 27 soil samples were collected from kitchen gardens and lawns with various physicochemical parameters and contamination levels. Significant relationships were obtained between Cd, Pb and Zn extracted in gastric and gastrointestinal phases and using single extractions. The best relationhips were established using acetic and citric acids for Cd, whereas for Pb, citric acid and ethylenedi- aminetetraacetic acid （EDTA） were identified as the best extractants. These relationships were improved by means of a linear multiple regression with a downward stepwise procedure involving agronomic parameters （soil cation exchange capacity and assimilated P）. This method highlighted the fact that the cation exchange capacity and P contents in soils were the two main parameters that controlled the human bioaccessibility of Cd, Pb and Zn in the gastric phase. Besides, the metal concentrations extracted with the acetic and citric acids correlated well with the metal concentrations in the gastric and gastrointestinal phases, suggesting that the bioaceessible metals were mainly in a soluble form, weakly bound to the organic matter and associated with the carbonates and the Fe and Mn oxides/hydroxides in soils.

Phosphorus Use Efficiency of Bio-Based Fertilizers:Bioavailability and Fractionation

Although to date some technologies producing bio-based phosphorus(P) fertilizers have been proposed and implemented, the efficient use of the recovered products is still limited due to legislative constraints and lack of insights in the P release with time and in the corresponding mechanisms. The aim of this work was to evaluate the fertilizer performance in terms of P release and use efficiency of recovered struvite, FePO_4-sludge, digestate, and animal manure as compared to fossil reserve-based mineral triple superphosphate(TSP). First, product physicochemical characteristics and P fractions in the context of European fertilizer legislation were assessed. Next, a controlled greenhouse experiment was set up to evaluate plant reactions as well as changes of P availability in a sandy soil with high P status and a Rheinsand soil with low P status. Soil P fractions were determined in the extracts with water, ammonium lactate and CaCl_2, and in soil solution sampled with Rhizon soil moisture samplers. Based on all results, it is worth conducting long-term field trials to evaluate the P release effect of struvite and digestate as compared to animal manure and TSP on different soil types with varying P status. These products showed promise as sustainable substitutes for conventional P fertilizers and could contribute to a more efficient use of P in agriculture. A refined classification of P application standards/recommendations in terms of soil P status, soil texture, and fertilizer characteristics, next to the crop P demand, is recommended. Moreover, the additional use of Rhizon samplers for determination of direct available P, including dissolved organic P, is proposed for better understanding and categorization of different P fertilizers in environmental and fertilizer legislations.

Theoretical studies and industrial applications of oxidative activation of inert C-H bond by metalloporphyrin-based biomimetic catalysis

High costs and low catalytic efficiency of metalloporphyrins, which are an analogue of cytochrome P450 enzyme, are the bot-tlenecks in the industrialization of biomimetic hydrocarbon oxidation reactions. The basic principle and research technique of physical organic chemistry were applied to the process of biomimetic oxidation of hydrocarbon catalyzed by metalloporphyrins. This biomimetic technology could be adapted to bulk chemicals production by developing the new methods for efficient scale-up synthesis of metalloporphyrins, new pathways for molecular oxygen activation on an industrial scale and new approaches to elevate the catalytic efficiency of metalloporphyrins. This review mainly focuses on research carried out in our group.

Unorthodox chemistry for an unorthodox challenge:Exploration of new chemical reactivities for a sustainable future

The sustainable development of our future represents an unorthodox challenge in sciences and technologies.The exploration of unconventional chemical reactivities that could potentially result in more sustainable chemical productions with efficient utilization of resource and inherent prevention of waste will provide the foundation for the synthetic chemistry of our future.As part of this endeavor,we have explored metal-mediated reactions in water to minimize protection-deprotection and the use of organic solvents,catalytic nucleophilic additions via C-H reactions to avoid generation and use of stoichiometric organic halides and metal in water,and Cross-Dehydrogenative-Coupling(CDC) reactions to minimize overall transformation steps.