Assimilation Of Silicon Research Articles

Silicon efficacy for the remediation of metal contaminated soil.

In the course of past two decade anthropogenic activities have reinforced, begetting soil and water defilement. A plethora of heavy metals alters and limits plant growth and yield, with opposing effect on agricultural productivity. Silicon often perceived as plant alimentary 'nonentity'. A suite of determinants associated with silicon have been lately discerned, concerning plant physiology, chemistry, gene regulation/expression and interaction with different organisms. Exogenous supplementation of silicon renders resistance against heavy-metal stress. Predominantly, plants having significant amount of silicon in root and shoot thus are barely prone to pest onset and manifest greater endurance against abiotic stresses including heavy-metal toxicity. Silicon-mediated stress management involves abatement of metal ions within soil, co-precipitation of metal ions, gene modulation associated with metal transport, chelation, activation of antioxidants (enzymatic and non-enzymatic), metal ion compartmentation and structural metamorphosis in plants. Silicon supplementation also stimulates expression of stress-resistant genes under heavy-metal toxicity to provide plant tolerance under stress conditions. Ergo, to boost metal tolerance within crops, immanent genetic potential for silicon assimilation should be enhanced. Current study, addresses the potential role and mechanistic interpretation of silicon induced mitigation of heavy-metal stress in plants.

Peculiarities of the Dynamics of Some Elements of Hydrochemical Regime in Small Water Bodies of Urban Territories: Nutrients and Organic Matter

Results of the study of spatial and temporal dynamics of inorganic forms of nitrogen (NH4+, NO2-, and NO3-), phosphorus, silicon, and dissolved organic matter in the water of the system of Opechen lakes are given in the paper. It has been found that the concentration of dissolved oxygen essentially influences relationship between inorganic forms of nitrogen. The coefficient of correlation between oxygen content and the contribution of ammonium, nitrite, and nitrate accounted for respectively -0.79, 0.60, and 0.78 (at the level of significance of 0.01). At the concentration of dissolved oxygen of ≤ 4 mg/L, the contribution of NH4+, NO2-, and NO3- accounted for respectively ≥ 80, ≤ 6, and ≥ 14% Ninorg, at the concentration of oxygen of 4-8 mg/L - 60-80, 6-12, and 14-28% Ninorg, whereas at a further increase in oxygen content up to 16 mg/L their contribution was 18, 24, and 58% Ninorg. In wintertime during the period of reverse temperature stratification, the difference between the content of inorganic nitrogen and its different forms, and also between the content of inorganic phosphorus, in the surface and near-bottom layers of water was insignificant, or it was not more than 2.5 times. During the period of the formation of direct temperature stratification from spring until autumn, the difference between the concentration of the above-mentioned forms of nitrogen and inorganic phosphorus in these layers was rather significant. The concentration of NH4+ and Pinorg significantly increased in the layer located below thermocline. The upper three lakes (Minske, Lugove, and Ptashyne) proved to be most contaminated by the compounds of inorganic nitrogen and phosphorus. A decrease in their concentration in the surface layer of water was conditioned by the assimilation of these substances by the biota, whereas the increase in the concentration of the above mentioned compounds in the near-bottom layer of water - by their influx from bottom sediments under conditions of oxygen deficiency accompanied by the formation of anaerobic conditions. Based on the averaged indices, N : P molar ratio decreased from winter until autumn within the range between 16.0 and 5.7, which is indicative of the increase in the concentration of phosphorus relative to nitrogen, and also of the formation of favorable conditions to the development of blue-green algae. The concentration of dissolved silicon in the water of the lakes varied from 0.03 to 6.4 mg/L. A decrease in its content in the surface layer of water in spring was conditioned by silicon assimilation by diatoms. The total content of dissolved organic matter and its individual groups changed from season to season and in space. The contribution of readily oxidized organic compounds in the water of the upper three lakes accounted for 15.8-55.3%, whereas in the water of the lower three lakes - 29.1-81.6% of the total content of dissolved organic matter. The maximum indices were registered in summertime. The upper three lakes proved to be most contaminated by organic matter. The concentration of natural groups of dissolved organic matter, including humic substances, carbohydrates, and protein-like substances, in the water of the lakes accounted for 4.6-8.0, 0.66-5.43, and 0.26-1.09 mg/L. Their contribution to the total balance was 37.6-55.5%. The rest was made up by other groups of dissolved organic matter (probably of anthropogenic origin).

Biochemical markers of bone tissue metabolism in broiler chickens

The article presents the results of studies to identify possible intravital markers of bone metabolism in fast-growing meat crosses. As a result of the research it was determined that the introduction of mineral components containing calcium, phosphorus, magnesium and silicon into the feed of broiler chickens on the background of the diet balanced in biologically active substances helps to activate the processes of biological synthesis in bone tissue, normalize its mineral component with a high degree of silicon assimilation and also increases the stability of the bones of the lower limbs of broiler chickens. It has been proved that in order to monitor the prevention and treatment of dyschondroplasia in meat poultry, it is necessary to use in vivo biochemical markers of bone tissue metabolism, which allow carrying out early and accurate diagnosis of bone diseases in poultry.

The Probable Mechanism for Silicon Capture by Diatom Algae: Assimilation of Polycarbonic Acids with Diatoms-Is Endocytosis a Key Stage in Building of Siliceous Frustules?

Many organisms including unicellular (diatoms, radiolaria, and chrysophytes), higher plants (rice and horsetail) and animals (sponges) use silica as a main part of skeletons. The bioavailable form of silicon is silicic acid and the mechanism of silicic acid penetration into living cells is still an enigma. Macropinocytosis was assumed as a key stage of the silicon capture by diatoms but assimilation of monomeric silicic acid by this way requires enormous amounts of water to be passed through the cell. We hypothesized that silicon can be captured by diatoms via endocytosis in the form of partially condensed silicic acid (oligosilicates) whose formation on the diatom surface was supposed. Oligosilicates are negatively charged nanoparticles and similar to coils of poly(acrylic acid) (PAA). We have synthesized fluorescent tagged PAA as well as several neutral and positively charged polymers. Cultivation of the diatom Ulnaria ferefusiformis in the presence of these polymers showed that only PAA is able to penetrate into siliceous frustules. The presence of PAA in the frustules was confirmed with chromatography and PAA causes various aberrations of the valve morphology. Growth of U. ferefusiformis and two other diatoms in the presence of tri- and tetracarbonic fluorescent tagged acids points to the ability of diatoms to recognize substances that bear four acidic groups and to include them into siliceous frustules. Thus, partial condensation of silicic acid is a plausible first stage of silicon assimilation.

Interaction of SiFe Nanoparticles with Epithelial and Lymphoid Cells

Silicon and silicon-based nanoparticles (SiNP) attract scientific attention due to the biocompatibility and assimilation of silicon by body tissues. Iron-doped SiNP (SiFeNP) allow the use of ferromagnetic properties of iron for NP detection and the possibility of therapeutic application of SiFeNP. The purpose of this work was to analyze the interaction of SiFeNP with epithelial cells (EC) COLO357 and SW620 and human peripheral blood lymphocytes (PBL). SiFeNP were obtained by laser ablation and divided into the NP1 and NP2 fractions of 100 and 150 nm size, respectively. Cytotoxicity, apoptosis induction, reactive oxygen species (ROS) production, and lysosome metabolism were analyzed using in vitro methods. EC were found to efficiently incytosed both types of NPs, which resulted in the increase in the granularity of cells. NP did not cause apoptosis or EC necrosis, but accumulated in lysosomes, which led to a decrease in the membrane potential of lysosomes. In turn, a decrease in the level of EC metabolism led to a gradual (24 h) increase in ROS production by 10–15%. NP1 caused more ROS than NP2, and accumulated more in the EC, which may be the result of a difference in the particle size. SiFeNP did not interact with PBL. Thus, the total cytotoxicity of SiFeNP did not exceed 20%, which is associated with a decrease in lysosome metabolism and insignificant ROS production.

Can climate-driven change influence silicon assimilation by cereals and hence the distribution of lepidopteran stem borers in East Africa?

In East Africa, lepidopteran stemborers such as Chilo partellus and Busseola fusca are major constraints to production of maize, which is the main staple food crop in the region. Cereals depend on silicon (Si)-based defences to fight off herbivores. Using altitudinal ranges in the East African highlands as ecological surrogates for inferring climate change, it was shown that Si concentrations in soil and maize decreased with altitude. This was attributed, in part, to low temperatures at high altitudes, which negatively affected Si assimilation by maize. Experiments showed that B. fusca was more susceptible to Si than C. partellus. Hence the predominance of B. fusca in the highlands and of C. partellus in the lowlands could be partly explained by altitudinal differences in Si concentrations in maize plants. Therefore, a rise in temperature due to climate change should enhance the plants’ Si assimilation and as a result C. partellus might move into the higher altitudes and increasingly displace B. fusca.

Theoretical and experimental substantiation of treatment of aluminum-based melts by pulsed magnetic fields

Factors causing the solid-phase dispersion of the particles of alloying elements in the aluminum melt depending on their nature are considered. It is shown that the particles can be fragmented under the effect of uniform tensile stresses appearing due to heating the particles. The reasonability of using additional external effects (for example, magnetic-pulsed treatment of the foundry-alloy melt) in order to intensify the assimilation of silicon in liquid aluminum and provision of microcrystalline structure of the foundry alloy is substantiated theoretically and confirmed experimentally by the example of the Al–20wt%Si foundry alloy.

Theoretical and experimental substantiation of treatment of aluminum-based melts by pulsed magnetic fields

Factors causing the solid-phase dispersal of particles of alloying elements in the aluminum melt depending on their nature are considered. It is shown that the particles can be fragmented under the effect of uniform tensile stresses appearing due to the particles heating. The reasonability of using additional external effects (for example, magnetic-pulsed treatment of the foundry-alloy melt) to intensify the assimilation of silicon in liquid aluminum and provide the microcrystalline structure of the foundry alloy is substantiated theoretically and confirmed experimentally by the example of the Al–20 wt % Si foundry alloy.

Manufacture, Study, and USE of Briquetted Ferroalloys for Steel Deoxidation

A method is developed for manufacturing briquettes based on fine ferroalloy screenings providing sufficient mechanical strength and suitability for transportation. A batch of briquettes is manufactured from ferroalloy screenings for steel deoxidation. Ferroalloy briquette composition is studied in a scanning electron microscope. It is shown that a briquette consists of fine ferroalloy particles and pure silicon bonded by sodium silicate with various additives. Ferroalloy briquettes are tested for medium-carbon steel deoxidation in a steel-pouring ladle. Silicon assimilation from ferroalloy briquettes is 65% on average.

Fluorescent Amines as a New Tool for Study of Siliceous Sponges

Siliceous sponges (Hexactinellida and Demospongiae classes) are aquatic invertebrates which are important both for marine and freshwater ecology and also as the source of biologically active compounds. The sponge skeleton consists of spicules - needle-like or branched composite structures based on silicon dioxide. Mechanisms of silicon assimilation and synthesis of high-ordered glass-like structures at ambient temperatures by sponges are intriguing for biologists, chemists and nanotechnologists. Fluorescent amines are in-vivo dyes that stain growing siliceous frustules of diatom algae so the use of these agents for the sponge study was attempted. We found that cultivation of the Lubomirskia baicalensis (Pallas, 1773) sponge in the presence of fluorescent tracers of biosilica - N1,N3,N3-trimethyl-N1-(7-nitro-2,1,3- benzoxadiazol-4-yl)propane-1,3-diamine and N1,N3-dime thyl-N1-[3-(dimethylamino)propyl]-N3-(7-nitro-2,1,3-benz oxadiazo-4yl)propane-1,3-diamine results in the staining of growing siliceous spicules. This finding shows that amine dyes accompany silicon from the environment to sponges spicules which opens a new way to study of silicon assimilation by sponges. Fluorescent staining of the growing spicules following with the confocal microscopy can be a powerful tool for morphological studies, revealing information about the dynamics of spiculogenesis and for bio-fabrication of new fluorescent materials.

Melting of Grey Cast Iron Based on Steel Scrap Using Silicon Carbide

Abstract The paper presents the issue of synthetic cast iron production in the electric induction furnace exclusively on the steel scrap base. Silicon carbide and synthetic graphite were used as carburizers. The carburizers were introduced with solid charge or added on the liquid metal surface. The chemical analysis of the produced cast iron, the carburization efficiency and microstructure features were presented in the paper. It was stated that ferrosilicon can be replaced by silicon carbide during the synthetic cast iron melting process. However, due to its chemical composition (30% C and 70% Si) which causes significant silicon content in iron increase, the carbon deficit can be partly compensated by the carburizer introduction. Moreover it was shown that the best carbon and silicon assimilation rate is obtained where the silicon carbide is being introduced together with solid charge. When it is thrown onto liquid alloy surface the efficiency of the process is almost two times less and the melting process lasts dozen minutes long. The microstructure of the cast iron produced with the silicon carbide shows more bulky graphite flakes than inside the microstructure of cast iron produced on the pig iron base.

Putative silicon transport vesicles in the cytoplasm of the diatom Synedra acus during surge uptake of silicon

We studied the growth of the araphid pennate diatom Synedra acus subsp. radians (Kützing) Skabichevskii using a fluorescent dye N(1),N(3)-dimethyl-N(1)-(7-nitro-2,1,3-benzoxadiazol-4-yl)propane-1,3-diamine (NBD-N2), which stains growing siliceous frustules but does not stain other subcellular organelles. We used a clonal culture of S. acus that was synchronized by silicon starvation. Epifluorescence microscopy was performed in two different ways with cells stained by the addition of silicic acid and the dye. Individual cells immobilized on glass were observed during the first 15-20 min following the replenishment of silicic acid after silicon starvation. Alternatively, we examined cells of a batch culture at time intervals during 36 h after the replenishment of silicic acid using fluorescence and confocal microscopy. The addition of silicic acid and NBD-N2 resulted in the rapid (1-2 min) formation of several dozen green fluorescent submicrometer particles (GFSPs) in the cytoplasm, which was accompanied by the accumulation of fluorescent silica inside silica deposition vesicles (SDVs) along their full length. In 5-15 min, GFSPs disappeared from the cytoplasm. Mature siliceous valves were formed within the SDVs during the subsequent 14-16 h. In the next 8-10 h, GFSPs appeared again in the cytoplasm of daughter cells. The data obtained confirm observations about the two-stage mechanism of silicon assimilation, which includes rapid silicon uptake (surge uptake) followed by slow silica deposition. It is likely that the observed GFSPs are silicon transport vesicles, which were first proposed by Schmid and Schulz in (Protoplasma 100:267-288, 1979).

Statistical models of the assimilation of silicon and manganese in the ladle treatment of steel

The objectives of the study discussed in this article were to analyze production data and construct regression models that can describe the changes in the concentrations of manganese and silicon in reinforcement steel during its treatment outside the steelmaking furnace. The results that are obtained can be used to devise a new technological scheme for the ladle treatment of reinforcement steels at mini-mills.

Effect of nutrient amendments on the summer phytoplankton dynamics on the Bering Sea shelf under experimental conditions

Experiments on nutrient and iron amendments were performed with phytoplankton on the eastern shelf of the Bering Sea in June 2000 and August 2001. The nutrient amendments (NO3, NH4, SiO4, NO3 + SiO4, NH4 + SiO4, and Fe + NO3) increasing their initial concentrations by ∼20 μM were put into test bottles 10 l in volume each. With iron addition (Fe or Fe + NO3), its concentration increased by 5 nM. The experiments performed showed that the main nutrient that limited the phytoplankton development was nitrogen. Regardless of the composition of the dominant algae in the background community, the amendments caused massive development of diatoms. The intense growth was characteristic for diatoms of both the spring and spring-summer assemblages. At high abundances of Phaeocystis pouchetii or of the coccolithophore Emiliania huxleyi in the natural water, nitrogen-containing amendments caused an intense growth of these species, along with the massive development of diatoms. In the case of the diatom prevalence in the initial sample, the intensities of the utilization of NO3 and NH4 in combination with SiO4 in the course of the experiment were 1.7 and 3 times as high as their intensities with no silicon amendments. Likewise, NO3 + SiO4 and NH4 + SiO4 mixed amendments caused an increase in the silicon assimilation by a factor of 4–5 as compared to pure silicon amendments. During one of the experimental series in which both diatoms and Phaeocystis pouchetii actively developed, virtually complete nitrogen utilization (90–99.8%) in 4–5 days was observed for both the NO3 and NH4. The addition of silicon and iron only caused no significant growth of the phytoplankton abundance. It was assumed that the destruction of the seasonal thermocline and the supply of nutrients into the surface layer as a result of strong wind forcing might cause a phytoplankton bloom in the summer time and result in the much pronounced qualitative and quantitative spatial heterogeneity of the phytoplankton characteristic of the eastern shelf of the Bering Sea.

Silicon nutrition promotes root growth and tissue mechanical strength insymbiotic cowpea.

Application of metasilicic acid (0, 0.04, 0.08, 0.20, 0.40 or 0.80 g L-1) to hydroponically-grown, Bradyrhizobium-infected cowpea [Vigna unguiculata (L.) Walp.] plants showed an increased assimilation of silicon into roots and shoots, which triggered a significant (P<0.05) promotion of root growth, but not shoot growth. Root : shoot ratio therefore, increased markedly (P<0.05) with higher metasilicate application. Mechanical strength of stems and peduncles also increased significantly (P<0.05) with silicon nutrition compared with control plants receiving no metasilicate. But the mechanical strength of roots was not affected. Radioimmunoassay of lateral roots, free of nodules, from plants fed metasilicate revealed markedly (P<0.05) increased concentrations of endogenous ABA, a hormonal signal that stimulates root growth. In contrast, a decreasing concentration of the cytokinin zeatin ribose was obtained with increasing metasilicate supply. These data show that silicon nutrition in symbiotic cowpea promotes an increase in mechanical strength of stems, which bear the entire weight of shoots, and peduncles, which, in turn, support weighty reproductive structures including developing pods and seeds. The increased concentration of ABA in roots as a result of improved silicon nutrition suggests that this element might be an elicitor of ABA biosynthesis and / or its accumulation, which then affected lateral root growth in this study.

Macroexothermic phenomena in exothermic additions: mathematical and physical modelling

In this paper a mathematical model is presented to predict the macroexothermic phenomena occurring when exothermic additions in lump form are assimilated in ferrous metals. The macroexothermic phenomena take place during the free assimilation period of exothermic additions in ferrous metals. These phenomena are characterized by unique coupled heat, mass and momentum transport phenomena. The presence of a moving boundary complicates further these phenomena. The model uses the Simpler algorithm to solve numerically the pertinent partial differential equations. The extensive verification of the model was carried out in two contexts. The first was, in a low temperature physical model consisting of ice immersion in different sulfuric acid solutions. The melting of ice in these solutions is extremely exothermic. In this physical model, both temperature and velocity measurements were carried out. The model results were compared with experimental measurements and they were found to be in excellent agreement. The second context employed high temperatures, involving the assimilation of silicon in high carbon liquid iron. The model was also applied to predict the position of the moving boundary for these high temperature experiments and a good agreement was obtained. In addition new dimensionless convective heat transfer correlations that quantify these complex phenomena are presented. Die vorliegende Arbeit stellt ein mathematisches Modell zur Vorhersage makroexothermer Phänomene, die auftreten, wenn exotherm reagierende Zusätze in stückiger Form in eisenhaltigen Metallen assimilieren, vor. Die makroexothermen Phänomene treten während der freien Aufnahme von exotherm reagierenden Zusätzen in eisenhaltigen Metallen auf und sind durch außergewöhnliche Kopplungswärme, Stoff- und Momententransportphänomene charakterisiert. Das Vorhandensein wandernder Grenzen trägt weiterhin dazu bei, diese Phänomene zu verkomplizieren. Das Modell benutzt den Simpler-Algorithmus zur numerischen Lösung der entsprechenden partiellen Differentialgleichungen. Die umfassende Überprüfung des Modells geschah für zwei Geltungsbereiche: Der erste bestand in einem physikalischen Modell für tiefe Temperaturen, bei dem Eis in verschiedene schwefelsaure Lösungen eingetaucht wird. Das Aufschmelzen von Eis in diesen Lösungen ist ein extrem exothermer Vorgang. In diesem physikalischen Modell werden sowohl die Temperatur als auch die Geschwindigkeit gemessen. Die Ergebnisse des Modells werden mit experimentellen Ergebnissen verglichen; die Übereinstimmung ist mehr als gut. Die zweite Variante für hohe Temperaturen bezieht auch die Aufnahme von Silicium in hochgekohlten Eisenschmelzen mit ein. Das Modell wurde auch auf die Vorhersage der Position wandernder Grenzen bei diesen hohen Temperaturen angewendet; auch hier wurde gute Übereinstimmung erzielt. Zusätzlich werden neue Korrelationen für dimensionslosen konvektiven Wärmeübergang präsentiert, die diese komplexen Phänomene quantifizieren.

Use of slag ferromanganese to deoxidize low-carbon rimming steel

The Karaganda Metallurgical Combine has developed and introduced a technology for deoxidizing low-carbon rimming steel (including steel for use in tinplate production) which employs slag ferromanganese. The technology includes refining of the steel in 300-ton converters from phosphorus pig iron (1-1.3% P) by the double-slag process and deoxidation in the ladle during tapping with high-carbon ferromanganese containing up to 1.5% Si. Aluminum in amounts up to 100-150 kg/ton steel is added to the ladle, the exact amount depending on the carbon content of the metal prior to tapping. If necessary to keep the manganese content of the finished steel in the range 0.320.38%, ferromanganese is also added during blowing of the metal with inert gas on the finishing unit. The steel is teemed through a 60-ram-diameter nozzle into ingots weighing 16.3 tons. When the metal is deoxidized in the ladle, assimilation of silicon from the ferromanganese averages about 15%. As a result, the silicon content of the steel increases to 0.008-0.12%. Shown below are processing and quality indices of heats of steel 08kp deoxidized with ferromanganese containing different amounts of silicon:

Silicon depletions in some Norfolk rivers

SummaryWater samples collected weekly from the rivers Yare, Tud, Wensum and Tas in Norfolk, England, displayed marked depletions in the spring and summer of the concentration of dissolved silicon. These were unconnected with any hydrological event and were assumed to be due to the assimilation of silicon by diatoms. Equilibrium concentrations were maintained in the Yare and Tud during the weeks prior to and following the spring bloom. It was estimated that 35 Mg (51%) of the predicted load were removed from the Yare during the 11 weeks of this depletion and 6‐0 Mg (45%) from the Tud. The lowest observed concentration (0‐4 mg/l) occurred during the first week in May when over 90% of the silicon had been removed. However, the maximum amount of removal and hence maximum diatom productivity occurred earlier at a time of higher water discharge. A similar pattern was observed in the Yare during the spring of 1971. Two small blooms occurred later in the summer of 1970 in the Yare and Tud. It was estimated that 15% ofthe Yare's dissolved silicon load of 263 Mg was in the assimilated form and 12‐5%of the Tud's output of 56‐6 Mg. The weathering of silicate minerals was probably the source of almost all the silicon and the outputs represented a silicon erosion rate of 1‐15 Mg/km2/year for the Yare and 0‐77 Mg/kmVyear for the Tud.