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121.
作物产量构成因素通径分析方法的再商榷 总被引:3,自引:0,他引:3
本文讨论了作物产量构成因素通径分析的方法。提出按因果关系将各因素对产量的效应剖分为多个路段,并进而计算与比较其效应总和及总决定程度。在各因素的变异较大时,对数转换后再进行通径分析才合理。 相似文献
122.
Mayerhoff Zea D. V. L. Roberto Inês C. Franco Telma T. 《Applied biochemistry and biotechnology》2001,91(1-9):729-737
Xylose reductase (XR) activity was evaluated in extracts of Candida mogii grown in media containing different concentrations of rice straw hydrolysate. Results of X Ractivity were compared to xylitol
production and a similar behavior was observed for these parameters. Highest values of specific production and productivity
were found for xylose reductase (35 U/g of cell and 0.97 U/[g of cell·h], respectively) and for xylitol (5.63 g/g of cell
and 0.13 g/[g of cell·h]) in fermentation conducted in medium containing 49.2 g of xylose/L. The maximum value of XR:XD ratio
(1.82) was also calculated under this initial xylose concentration with 60 h of fermentation. 相似文献
123.
磺化水热碳催化乙酰丙酸酯化生成戊酮酸乙酯(英文) 总被引:2,自引:0,他引:2
The synthesis of carbon-based, heterogeneous sulphonic catalysts for the production of levulinate esters. Hydrothermal treatment at moderated temperatures was employed to generate highly functional carbonaceous materials, referred to as hydrothermal carbons (HTCs), from both glucose, cellulose and rye straw. The products were sulfonated to generate solid acid-catalysts. Characterisation of the as-synthesised materials as well as catalyst activity tests were performed. SEM images indicate the micrometre-sized particles present in both HTCs were largely unaffected by sulfonation, although cellulose-derived HTC displayed signs of inadequate hydrolysis. FT-IR spectroscopy and elemental analysis confirmed successful incorporation of sulphonic groups. 13C solid state NMR, in addition to TGA, elucidated the carbons’ structural composition and supported the common-ly-proposed hydrothermal carbonisation mechanism. Finally, the catalysts were tested via levulinic acid-ethanol esterification and gave high conversion and ester-selectivities ( 90%). 相似文献
124.
采用高浓度的玉米秸秆(60g·L-1)作为产氢底物,研究了在氢发酵过程中几个关键过程参数对发酵产氢的影响,以期在秸秆废弃物的清洁氢能转化过程中减少发酵废水的生成总量.结果表明,在酸化秸秆浓度为60g·L-1,碳酸氢铵添加量为1.2g·L-1,十六烷基三甲基溴化铵添加量为30mg·L-1,菌株Bacillus sp.FS2011添加量为10%(质量分数),以及初始pH=7.5±0.5、发酵温度(37±1)℃条件下,最大产氢量和产氢速率分别为(79.8±1.5)mL·g-1和3.78mL·g-1·h-1.与使用低浓度秸秆(≤20g·L-1)底物时相比,生成的氢发酵废水总体积减小了约67%. 相似文献
125.
Francesco Zimbardi Donato Viggiano Francesco Nanna Mario Demichele Daniela Cuna Giovanni Cardinale 《Applied biochemistry and biotechnology》1999,77(1-3):117-125
The effects of the steam-explosion treatment on aqueous fractionation and bioconversion of wheat straw have been investigated.
The treatments have been carried out in batch and continuous reactors with capacity of 0.5 Kg/cycle and 150 Kg/h, respectively.
The exploded materials have been sequentially extracted with water at 65°C and sodium hydroxide 1.5%. Analytical determinations
of liquid fractions and solid residues haveled to the fractionation pattern of the carbohydrates as, monomers, oligomers,
and polymers. Evaluations of total acidity, ash content, and lignin recovery have improved understanding of the process. This
part of the work has allowed us to derive: the empiric relationship between the batch and the continuous reactors and the
yield and availability of pentoses and hexoses in various phases. Selected samples have been tested in enzymatic-hydrolysis
experiments, pointing out the effect of treatment severity and reactor used on the saccharification yield. 相似文献
126.
The reactions of wheat-straw (Triticum aestivum) cellulose, hemicellulose, and lignin with a mixture of nitric and trifluoroacetic acids and certain properties of the nitration
products were studied for straw directly and for structural components isolated from it. The nitration products could be separated
into nitrates of structural polysaccharides and nitrolignin by treatment with hot bases.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 477–479, September–October, 2006. 相似文献
127.
The distribution of radioactive pollutants, such as ~(222)Rn, U, Th and ~(226)Ra in the air, sur-face waters, soils and crops around the Lincang uranium mine, Yunnan Province, China, is studiedThe mechanical, geochemical and biogeochemical processes responsible for the transport andfate of the radioactive elements are discussed based on the monitoring data. The pollutants con-centrations of effluents from the mine tunnels were dependent on pH and SO_4~(2-) which were con-trolled by biochemical oxidation of sulfide in the ore/host rocks. Radon anomalies in air reached 4km from the tailings pile depending on radon release from the site, topography and climate. ~(238)Uand ~(226)Ra abnormities in stream sediments and soil were 40-90 cm deep and 790-800 m awaydownstream. Anomalies of radioactive contaminants of surface watercourses extended 7.5-13km from the discharge of effluents of the site mainly depending on mechanical and chemical proc-esses. There were about 2.86 ha rice fields and 1.59 km stream sediments contaminated. Erosionof tailings and mining debris with little or no containment or control accelerated the contaminationprocesses. 相似文献
128.
《Arabian Journal of Chemistry》2019,12(7):1186-1196
Silica (SiO2) nanoparticles and silica/calcium carbonate (SiO2/CaCO3) core–shell nanocomposites were prepared by sol–gel technique as fillers for papermaking application. Semi-burned rice straw ash (SBRSA), as waste material, was used to prepare the targeted fillers. Preparation of SiO2 nanoparticles and SiO2/CaCO3 nanocomposites was carried out using Na2SiO3 solution that was prepared from SBRSA and CaCO3 nanoparticles of 30–70 nm. The targeted SiO2/CaCO3 nanocomposites were prepared with different molar ratio of SiO2:CaCO3 1:15, 1:10 and 1:5. The percentage of silica increased from 62.5% to 82.9% by thermal treatment of SBRSA at 800 °C for 2 h. The prepared SiO2 nanoparticles and SiO2/CaCO3 nanocomposites were characterized by using XRD, XRF, TEM, FT-IR and Zeta potential. The results indicate that a pure semi-crystalline SiO2 nanoparticle and semi-crystalline shell of SiO2 coated CaCO3 core particles were produced. The work extended also to investigate the effect of the prepared fillers on physical, mechanical and optical properties of paper.Application of the prepared SiO2 nanoparticles and SiO2/CaCO3 nanocomposites improved the optical properties of paper (brightness, whiteness and opacity) but it slightly reduced the mechanical properties when compared to commercial precipitated CaCO3 (PCC) filler.The results showed that the retention of SiO2 nano-particles was highly increased. The retention of the prepared nanocomposites increased along with increasing of SiO2:CaCO3 molar ratio. 相似文献
129.
土壤环境生态对重金属元素迁移影响分析 总被引:7,自引:1,他引:7
程金沐 《广东微量元素科学》2005,12(6):12-15
作物中重金属元素主要来自土壤,其含量与作物种类和土壤环境有关。土壤中重金属元素含量、土壤pH值、Eh值、土壤化学组成、土壤质地等环境因素都影响作物中重金属元素含量。土壤pH值和Eh值影响重金属元素的活动性。重金属元素的水溶态容易被作物吸收,而难溶态和被土壤胶体固定的重金属元素,不能被作物吸收。同种作物重金属元素含量的差异主要取决于土壤环境。 相似文献
130.
Treatment of the dewaxed wheat straw with acetic acid-H2O (65/35, v/v), acetic acid-H2O (80/20), acetic acid-H2O (90/10), formic acid-acetic acid-H2O (20/60/20), formic acid-acetic acid-H2O (30/60/10), methanol-H2O (60/40), and ethanol-H2O (60/40) using 0.1% HCl as a catalyst at 85 °C for 4 h degraded 42.4, 58.7, 70.0, 65.1, 76.5, 14.2, and 22.2% of the original hemicelluloses and 78.2, 80.0, 88.2, 89.4, 94.1, 23.5, and 37.4% of the original lignin, respectively. It was found that substantial hemicelluloses and lignin were degraded during the treatment with organic acids. The optimum condition for degradation of hemicelluloses was found to use a mixture of formic acid-acetic acid-H2O (30/60/10), which yielded 76.5% of the original hemicelluloses from wheat straw. Xylose was a major constituent in all the degraded hemicellulosic preparations. Glucose and arabinose appeared in noticeable amounts. Uronic acids, principally 4-O-methyl-d-glucuronic acid occurred in a small amount. Galactose, mannose, and rhamnose were present as minor components. In comparison, the five degraded hemicellulosic preparations isolated during the treatment with organic acids were more linear and partially acetylated, whereas the two acidic alcohol-degradable hemicelluloses were more branched. The FT-IR and liquid-state 13C NMR analyses revealed that the organosolv treatments under the acidic conditions substantially degraded the hemicellulosic polymers as shown by their lower molecular weights ranging between 8480 and 18,940 g mol−1. The thermal stability of the hemicellulosic preparations, degraded during the aqueous organic acids, was lower than that of the hemicellulosic preparations, degraded during the aqueous alcohols. 相似文献