河流输送硅通量降低的机制及生态效应

从筑坝成库、硅藻吸收和固定、渔业发展、水体富营养化、水文结构变化几方面对河流输送硅通量降低的影响机制进行了归纳分析,综述了河流输送硅通量降低对河流、河口和近海产生的生态效应。研究表明,河流输送硅通量降低对硅的地球化学循环平衡产生了巨大影响,并造成了一系列的生态变迁。其中,硅藻是河流输送硅通量降低的主要因素,大量繁殖的硅藻将水库水体溶解性硅(DSi)吸收后转化成自身的生物硅(BSi),死亡后沉积到水库底部贮存起来,导致下游河流和海洋缺乏DSi,从而产生对人类具有重大影响的生态效应。     

植物硅营养的研究进展

阐述了植物吸收硅的机理、硅与其它营养元素的关系及其对非胁迫和胁迫条件下植物生长发育的有益作用 .植物吸收硅的机制目前尚不是很清楚 ,不同植物吸收硅的方式不同 .硅可影响植物中其它营养元素的含量 .在非胁迫条件下 ,硅可促进植物的生长 ;硅也参与了植物抗病、抗虫等生物胁迫 ,以及抗金属毒害、盐害、温度胁迫、干旱、抗倒伏等非生物胁迫的反应 .目前 ,应从多种植物上深入研究硅的吸收方式与机理 ;同时 ,应该改变硅在细胞壁的沉积仅仅起增强组织机械强度作用的观点 ,而应从生理代谢调控的角度进行硅作用机制的研究 ,为生产实践中硅肥的应用奠定理论基础     

Optical properties of porphyrin molecules immobilized in nano-porous silicon

The paper aims at studying optical properties of porous silicon powders and thin films which were impregnated with different porphyrin molecules. It has been shown that introducing porphyrins into porous silicon matrix results in quenching of luminescence from porous silicon, while luminescence of porphyrins survives, though its structure changes. At the same time, porphyrins in porous silicon matrix which was preliminarily oxidized does not alter luminescence from porphyrins. Generation of singlet oxygen by illuminated porphyrin/porous silicon composite is confirmed by additional oxidation of porous silicon and by the observation of characteristic 1270 nm luminescence band.     

硅对PCR过程的抑制作用研究

探讨不同氧化程度的硅材料对PCR扩增的抑制作用及其机理。将不同氧化程度的硅纳米颗粒加入PCR反应液中,使其与Taq酶、模板等充分接触,通过离心将硅纳米颗粒沉降在管壁上,取出上清或保留硅纳米颗粒上机扩增,扩增产物采用凝胶电泳法检测。结果表明,随着硅材料表面面积与PCR反应液体积之比的增大,核酸扩增效率将明显下降,并且在所研究的范围内,氧化程度高的硅材料对PCR过程抑制作用更强;通过对抑制作用机理进行初步的实验研究,表明硅材料对PCR反应液中的Taq酶的吸附是导致抑制现象产生的主要原因,而对模板的吸附影响较小;并且,反应管内是否保留硅材料对核酸扩增影响较小,硅材料没有明显的直接化学抑制作用。     

Characterization of the silicon uptake system and molecular mapping of the silicon transporter gene in rice

Rice (Oryza sativa L. cv Oochikara) is a typical silicon-accumulating plant, but the mechanism responsible for the high silicon uptake by the roots is poorly understood. We characterized the silicon uptake system in rice roots by using a low-silicon rice mutant (lsi1) and wild-type rice. A kinetic study showed that the concentration of silicon in the root symplastic solution increased with increasing silicon concentrations in the external solution but saturated at a higher concentration in both lines. There were no differences in the silicon concentration of the symplastic solution between the wild-type rice and the mutant. The form of soluble silicon in the root, xylem, and leaf identified by (29)Si-NMR was also the same in the two lines. However, the concentration of silicon in the xylem sap was much higher in the wild type than in the mutant. These results indicate that at least two transporters are involved in silicon transport from the external solution to the xylem and that the low-silicon rice mutant is defective in loading silicon into xylem rather than silicon uptake from external solution to cortical cells. To map the responsible gene, we performed a bulked segregant analysis by using both microsatellite and expressed sequence tag-based PCR markers. As a result, the gene was mapped to chromosome 2, flanked by microsatellite marker RM5303 and expressed sequence tag-based PCR marker E60168.     

植物的硅素营养研究综述

本文阐述了硅在植物中的形态、分布、吸收、积累、生理作用及其与其它元素的关系。研究表明：1．硅主要以二氧化硅胶(SiO2.nH2O)的无机物形态存在于植物表皮细胞和细胞壁。植物体内硅的含量在不同物种间差异很大。根据硅的含量,可将一般栽培植物分为三种类群;同时根据植物硅钙摩尔比值可将植物分为喜硅植物和非喜硅植物。硅在植物各部分分布不均匀,并且随着植株的生长发育,植株中的硅含量不断变化。植物中硅的积累受环境中多种因素的影响。2．植物主要以单硅酸形态吸收硅,不同植物吸收硅的能力不同。水稻具有主动吸硅能力,其吸收过程受体内代谢活动影响<请合法使用软件>其它大多数植物主要以被动方式吸收硅,但不排除具有选择性吸收硅的可能性。3．硅对植物的生长发育产生影响。硅是一些植物(如禾本科植物、甜菜、木贼属植物及某些硅藻)的必需元素。硅对其它很多植物具有有益作用。硅对植物的作用主要表现在对形态结构、生理过程和抗逆能力三方面的影响 上。在去硅条件下,多种植物表现出缺硅症状。4．硅对植物吸收利用对其它营养元素产生影响。硅对不同元素的影响方式和程度不同,同时随着植物的生长发育,对某种元素的作用常发生变化。     

The solvation study of carbon, silicon and their mixed nanotubes in water solution

Nanotubes are believed to open the road toward different modern fields, either technological or biological. However, the applications of nanotubes have been badly impeded for the poor solubility in water which is especially essential for studies in the presence of living cells. Therefore, water soluble samples are in demand. Herein, the outcomes of Monte Carlo simulations of different sets of multiwall nanotubes immersed in water are reported. A number of multi wall nanotube samples, comprised of pure carbon, pure silicon and several mixtures of carbon and silicon are the subjects of study. The simulations are carried out in an (N,V,T) ensemble. The purpose of this report is to look at the effects of nanotube size (diameter) and nanotube type (pure carbon, pure silicon or a mixture of carbon and silicon) variation on solubility of multiwall nanotubes in terms of number of water molecules in shell volume. It is found that the solubility of the multi wall carbon nanotube samples is size independent, whereas multi wall silicon nanotube samples solubility varies with diameter of the inner tube. The higher solubility of samples containing silicon can be attributed to the larger atomic size of silicon atom which provides more direct contact with the water molecules. The other affecting factor is the bigger inter space (the space between inner and outer tube) in the case of silicon samples. Carbon type multi wall nanotubes appeared as better candidates for transporting water molecules through a multi wall nanotube structure, while in the case of water adsorption problems it is better to use multi wall silicon nanotubes or a mixture of multi wall carbon/ silicon nanotubes.     

Features of the mechanical treatment of rice husk for the performance of the solid-phase reaction of silicon dioxide with polyphenols

The distinguishing features of rice husk are high strength properties, chemical stability, high ash content, and low nutritional value, which are determined by the composition and structure of this type of raw material. The goal of the study was to determine optimal methods of mechanical treatment for the performance of a solid-phase reaction of silicon dioxide from rice husk with polyphenol compounds. Different regimes of the treatment of plant raw material have been compared. It has been shown that, for the solid-phase reaction of silicon dioxide from plant raw material with polyphenol compounds to occur, both the destruction of the supramolecular complex of silicon dioxide with the lignocellulose matrix, which is accomplished by fine grinding, and the plastic deformation of the silicon dioxide phase with the formation of reaction centers are necessary. These operations can be brought about using grinders with the attrition and shear modes of operation, including roller mills. It is preferable that silicon dioxide is in the composition of plant raw material since the reaction between silicon dioxide and polyphenols with the formation of surface complexes requires the presence of silanol groups. If silicon dioxide is derived from rice husk by conventional methods, most hydroxyl groups are eliminated, which significantly decreases the reactivity.     

Preparation of High Purity Crystalline Silicon by Electro-Catalytic Reduction of Sodium Hexafluorosilicate with Sodium below 180°C

The growing field of silicon solar cells requires a substantial reduction in the cost of semiconductor grade silicon, which has been mainly produced by the rod-based Siemens method. Because silicon can react with almost all of the elements and form a number of alloys at high temperatures, it is highly desired to obtain high purity crystalline silicon at relatively low temperatures through low cost process. Here we report a fast, complete and inexpensive reduction method for converting sodium hexafluorosilicate into silicon at a relatively low reaction temperature (∼200°C). This temperature could be further decreased to less than 180°C in combination with an electrochemical approach. The residue sodium fluoride is dissolved away by pure water and hydrochloric acid solution in later purifying processes below 15°C. High purity silicon in particle form can be obtained. The relative simplicity of this method might lead to a low cost process in producing high purity silicon.     

On the Effect of the Amorphous Silicon Microstructure on the Grain Size of Solid Phase Crystallized Polycrystalline Silicon

In this paper the effect of the microstructure of remote plasma‐deposited amorphous silicon films on the grain size development in polycrystalline silicon upon solid‐phase crystallization is reported. The hydrogenated amorphous silicon films are deposited at different microstructure parameter values R* (which represents the distribution of SiH_x bonds in amorphous silicon), at constant hydrogen content. Amorphous silicon films undergo a phase transformation during solid‐phase crystallization and the process results in fully (poly‐)crystallized films. An increase in amorphous film structural disorder (i.e., an increase in R*), leads to the development of larger grain sizes (in the range of 700–1100 nm). When the microstructure parameter is reduced, the grain size ranges between 100 and 450 nm. These results point to the microstructure parameter having a key role in controlling the grain size of the polycrystalline silicon films and thus the performance of polycrystalline silicon solar cells.     

Application of silicon sources increases silicon accumulation in perennial ryegrass turf on two soil types

This study investigated the ability of perennial ryegrass to accumulate silicon and the factors that may influence plant silicon accumulation. Plants were grown in the greenhouse in two soil types, peat:sand mix and Hagerstown-silt-loam, amended with two commercially available sources of silicon, calcium silicate slag and wollastonite at 0, 0.5, 1, 2, 5 and 10 t/ha. Shoot tissue of nine-week-old perennial ryegrass plants was analyzed for silicon content (%) and found to reach a dry matter concentration of up to 4% in this study. Silicon accumulation in perennial ryegrass was influenced by the soil type and source, and was higher in plants grown in low-silicon peat:sand mix compared to Hagerstown-silt-loam. Silicon content (%) in the plants consistently increased with increasing rates of silicon in all four soil and source combinations. Acetic acid (HAc) extractable silicon and Ca increased in both soil types when amended with either of the silicon sources. Effects of silicon sources on soil pH varied with soil type. This study indicates that soil type, source of silicon, and rate of silicon application are important factors influencing the uptake of silicon by perennial ryegrass which is a widely used turfgrass species in golf courses, sports fields, and residential lawns in the United States.     

EFFECT OF SILICON SUPPLY ON GROWTH,FERTILITY, AND MINERAL COMPOSITION OF AN ANNUAL BROME,BROMUS SECALINUS L. (GRAMINEAE)

A study of the effects of three levels of silicon nutrition, representing low, intermediate, and high levels, shows that silicon does not enhance the vegetative growth of Bromus secalinus (cheat), yet it increases the rate of seed development and the efficiency of seed set. Grasses supplied with silicon have a higher percent of viable seeds compared to those grown in very low levels of silicon. Silicon supply, however, is not an absolute requirement for cheat reproduction, since grasses growing in low silicon levels set flowers and seeds, and the average weight of individual seeds or the mean number of inflorescences per plant are not influenced by silicon nutrition. Concentrations of silicon in tissues of cheat increase over time and with higher levels of silicon supply. Considerable differences are found in the silicon content of various vegetative and reproductive parts of cheat. Among vegetative parts, levels of silicon are lowest in stems and highest in green and senescent leaf blades. Among reproductive parts, silicon is most highly concentrated in the husks (glumes, lemmas, and paleas) surrounding filled seeds and is almost nonexistent in the seed itself. Mechanisms influencing silicon deposition and the ecological significance of the present findings are discussed.     

土壤供Si能力及Si与N、P的相互作用

辽宁地区水田土壤有效Si含量和土壤pH值及粘粒含量呈正相关,和DTPA-Fe含量呈负相关.根据土壤有效Si含量及其有关因素判断土壤供Si能力强弱,发现供Si能力强的土壤主要分布在辽南稻作区及部分中部和辽北稻作区,供Si能力弱的土壤主要分布在东部山地稻作区和辽东稻作区.试验证明Si和N、Si和P之间有相互促进肥效的关系,在N、P、Si适当配比下稻谷产量最高,N、P、Si都影响谷草比,在三者相互作用下,稻谷最高产量出现在谷草比1.0-1.1范围内.     

施硅对抑制植物吸收重金属镉的效应研究进展

施用化学改良剂是控制土壤重金属污染的有效手段。研究施硅对抑制植物吸收重金属镉的影响及其作用机制,对促进利用硅肥作为改良剂治理重金属污染土壤技术的发展有重要意义。近年来,以硅肥作改良剂对重金属污染的土壤进行治理的研究大量涌现。本文从施硅对抑制植物吸收镉及镉在植物体内的分布、迁移的影响;从植物细胞膜透性、抗氧化物酶系和抗氧化剂等新陈代谢或生理过程及硅-金属复合物的结构组成等方面对植物抗镉胁迫的生理生化效应及其抑制植物吸收重金属镉的机制进行综述,并对今后有待进一步研究的问题提出了建议。     

Wetting characterisation of silicon (1,0,0) surface

Water droplets on bare silicon surfaces are studied to examine the wetting behaviour as a function of the surface energy and to parameterise water–silicon interactions in order to recover the hydrophobic behaviour measured by experiments. Two different wetting regimes characterised by a critical interaction strength value are observed. At a threshold value of the water–silicon interaction parameter, water molecules start penetrating into the first layer of silicon surface under thermally vibrating walls, resulting in two distinct wetting behaviours. Fixed (cold) silicon walls do not exhibit the two different wetting characteristics. Size effects are studied for nano-scale droplets, and line tension influence is observed depending on the surface wettability. Decrease in the droplet size increases the contact angle values for the low wetting cases, while contact angles decrease for smaller droplets on the high wetting surfaces. Considering the line tension effects and droplet size, ?_Si–O for water–silicon interactions to recover the hydrophobic behaviour of silicon surfaces is estimated to be 12.5% of the value predicted using the Lorentz–Berthelot mixing rule.     

Silicon metabolism in diatoms. I. Evidence for the role of reduced sulfur compounds in silicon utilization

1. Cells of the fresh water diatom Navicula pelliculosa may be grown in a mineral medium containing a low concentration of silicon. When transferred to a fresh silicate solution and incubated under non-growing conditions such deficient cells rapidly take up silicon from the medium. 2. The utilization of silicon is an aerobic process. 3. When deficient cells are washed with distilled water or saline, their ability to utilize silicon is impaired whereas respiration is unaffected. 4. The ability of washed cells to take up silicon can be partially restored with sulfate or ascorbic acid, and is completely restored by Na₂S, Na₂S₂O₃, glutathione, l-cysteine, dl-methionine, or ascorbic acid plus sulfate. 5. The sulfhydryl reagent, CdCl₂, inhibits silicon utilization of unwashed cells at concentrations which do not affect respiration. This inhibition similarly is reversed by glutathione or cysteine. 6. However, sodium iodoacetate or sodium arsenite inhibits respiration and silicon utilization at the same concentrations. 7. The silicon taken up by deficient cells is deposited at the cell surface as a thickening of the existing silica frustules. 8. Sulfhydryl groups in the cell membrane may be involved in silicon uptake by diatoms.     

Continuous selective extraction of secondary metabolites from Catharanthus roseus hairy roots with silicon oil in a two-liquid-phase bioreactor

A two-liquid-phase bioreactor was designed to extract indole alkaloids from Catharanthus roseus hairy roots with silicon oil. Partition studies between silicon oil and culture medium showed that the silicon oil did not alter the availability of nutrients. The affinity of tabersonine and l?chnericine for silicon oil is nine times higher than for the aqueous phase. Cultures were elicited with 25 mg/L of jasmonic acid. The growth of the hairy roots was not significantly modified by the presence of silicon oil. The overall specific yields of tabersonine and l?chnericine were increased by 100-400% and 14-200%, respectively, with the use of silicon oil in nonelicited control cultures. In elicited cultures, these values were 10-55% for tabersonine and 20-65% for l?chnericine. Serpentine was never found in the silicon oil. All measured alkaloids' specific yields were higher using silicon oil and elicitation, suggesting that the silicon oil, while acting as a metabolic sink for tabersonine and l?chnericine, was efficient in increasing metabolic fluxes of the secondary metabolism pathways.     

An interaction between dietary silicon and arginine affects immune function indicated by con-A-induced DNA synthesis of rat splenic T-lymphocytes

Sporadic reports have appeared that suggest silicon plays a functional role in immune function by affecting lymphocyte proliferation. In addition, there is also considerable interest in supplemental arginine as a modulator of immune function. Therefore, the purpose of this animal experiment was to determine the effect of supplemental compared to adequate arginine on immune function as measured by splenic T-lymphocyte proliferation in the presence of adequate or inadequate dietary silicon. The independent variables were, per gram of fresh diet, silicon supplements of 0 or 35 μg and arginine supplements of 0 or 5 mg. The basal diet contained 2.3 μg silicon/g and 7.82 mg l-arginine/g. After feeding the male rats (nine per treatment group) for 8 wk, spleen lymphoid cells were isolated and cultured with methyl-³[H]thymidine. Supplemental arginine significantly decreased Con-A-induced DNA synthesis of splenic T-lymphocytes, but the response to arginine was influenced by dietary silicon. The decreased DNA synthesis was more marked when rats were fed adequate silicon than when fed inadequate silicon. Also, when arginine was not supplemented, DNA synthesis was higher in lymphocytes from rats fed an adequate silicon diet than rats fed the inadequate silicon diet. These findings support the hypothesis that an interaction between silicon and arginine affects immune function and that inadequate dietary silicon impairs splenic lymphocyte proliferation in response to an immune challenge. The U.S. Department of Agriculture, Agricultural Research Service, Northern Plains Area is an equal opportunity/affirmative action employer, and all agency services are available without discrimination. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.     

森林生态系统硅素循环研究进展

硅是植物生长发育的有益元素,其在生态系统内的迁移转化是维持生态系统结构与功能的决定性因素之一。近年来,陆地生态系统硅循环特别森林生态系统硅循环在全球生物地球化学循环中的重要性,受到越来越多的关注。该文总结了国内外森林生态系统硅循环研究的成果,在综述了硅在森林生态系统中的存在形态、分布、循环过程的基础上,总结了森林生态系统硅循环的特点、作用及其影响因素,并指出典型森林生态系统类型中硅循环规律的研究、森林生态系统与其它生态系统硅循环的比较研究、森林生态系统硅循环对全球气候变化的影响和响应研究和人类干扰对森林生态系统硅循环的影响的研究将是今后开展森林生态系统硅循环研究的重点。