Poly(sodium-p-styrenesulfonate)-enhanced fluorescent silver nanoclusters for the assay of two food flavors and silicic acid.

A water-soluble, long-term stable, poly(sodium-p-styrenesulfonate)-enhanced and d-penicillamine stabilized argentum nanoclusters (PSS-DPA-AgNCs) was synthesized by a one-step ultraviolet radiation combined with microwave heating method. The effects of different types of polyelectrolytes and energy suppliers on the AgNCs photo-luminescence performance were investigated in detail. The prepared AgNCs are exhibited to be viable fluorescent method for 2-Mercapto-3-butanol (2-M-3-B), 3-Mercapto-2-butanone (3-M-2-B) and silicate (SiO32-) determinations. The fluorescence (FL) of PSS-DPA-AgNCs is quenched with the addition of 2-M-3-B/3-M-2-B/SiO32- mainly originating from a static quenching process. The method can monitor 2-M-3-B/3-M-2-B by fluorometry with a linear response in the range of 0.33-90.0/0.33-80.0 µM and a 74/250 nM detection limit (at 3σ/slope). For the SiO32- assay, corresponding data are 3.33-100.0 µM and 278 nM. Moreover, the proposed method was successfully used for the assays of two food flavors in the steamed bread and soda drinks, and silicate in the mineral water samples respectively.

Preparing diopside nanoparticle scaffolds via space holder method: Simulation of the compressive strength and porosity.

In the present study, diopside nanopowders were prepared via mechanical milling with eggshell as the calcium source. The space holder method (compaction of ceramic powder and spacer) as one of the most important methods to produce ceramic/metal scaffolds was used to produce diopside scaffolds. For the first time, the effect of the spacer size on mechanical properties and porosity of the obtained scaffolds was experimentally discussed. According to the results obtained, the NaCl particles (as the spacer) with the size of 400-600µm maintained their original spherical shape during the compaction and sintering processes. As a new work, the most important parameters including the spacer type, spacer concentration, spacer size, and applied pressure were considered, and their effects on mechanical properties and porosity of diopside scaffolds were simulated. Gene Expression Programming (GEP), as one of the most branches of the artificial intelligence, was used for simulation process. By using the GEP, two equations were introduced to predict the compressive strength and porosity of the obtained scaffolds with the lowest error values. The 3D diagrams extracted from the model were used to evaluate the combined effect of the process parameters on the compressive strength and porosity of the scaffolds. The GEP model presented in this work has a very low level of error and a high level of the squared regression for predicting the compressive strength and porosity of diopside scaffolds.

Biodegradable mesoporous delivery system for biomineralization precursors.

Scaffold supplements such as nanoparticles, components of the extracellular matrix, or growth factors have been incorporated in conventional scaffold materials to produce smart scaffolds for tissue engineering of damaged hard tissues. Due to increasing concerns on the clinical side effects of using large doses of recombinant bone-morphogenetic protein-2 in bone surgery, it is desirable to develop an alternative nanoscale scaffold supplement that is not only osteoinductive, but is also multifunctional in that it can perform other significant bone regenerative roles apart from stimulation of osteogenic differentiation. Because both amorphous calcium phosphate (ACP) and silica are osteoinductive, a biodegradable, nonfunctionalized, expanded-pore mesoporous silica nanoparticle carrier was developed for loading, storage, and sustained release of a novel, biosilicification-inspired, polyamine-stabilized liquid precursor phase of ACP for collagen biomineralization and for release of orthosilicic acid, both of which are conducive to bone growth. Positively charged poly(allylamine)-stabilized ACP (PAH-ACP) could be effectively loaded and released from nonfunctionalized expanded-pore mesoporous silica nanoparticles (pMSN). The PAH-ACP released from loaded pMSN still retained its ability to infiltrate and mineralize collagen fibrils. Complete degradation of pMSN occurred following unloading of their PAH-ACP cargo. Because PAH-ACP loaded pMSN possesses relatively low cytotoxicity to human bone marrow-derived mesenchymal stem cells, these nanoparticles may be blended with any osteoconductive scaffold with macro- and microporosities as a versatile scaffold supplement to enhance bone regeneration.

Initiation and Development of a Toxic and Persistent Pseudo-nitzschia Bloom off the Oregon Coast in Spring/2015.

In spring/summer 2015, a toxic bloom by the diatom Pseudo-nitzschia (PN) occurred along the west coast of the United States which led to closures of the harvest of razor clams and Dungeness crabs. Twice monthly observations of temperature, salinity, nutrients, chlorophyll and phytoplankton species composition allowed us to track oceanographic conditions preceding and during the development of the bloom. PN cells were first detected during late winter 2015. A PN bloom was initiated following the onset of coastal upwelling in mid-April; subsequent peaks in May and June were sustained by episodic upwelling events and reached magnitudes of 105 cells/L and 106 cells/L, 40% and 90% of the total diatom abundance, respectively. The bloom temporarily crashed in July due to a lack of upwelling, but PN cells increased again in August due to a resumption of upwelling, albeit with lower magnitude. Macronutrient conditions prior to this bloom likely played a critical role in triggering the bloom and its toxicity (particularly silicic acid limitation stress). Nutrient stress preceding the toxic bloom was related to two oceanographic events: an anomalously warm and thick water mass that occupied the northern North Pacific from September 2014 through 2015 leading to a highly-stratified water column, and the drawdown of nitrate and silicic acid during an unusually intense winter phytoplankton bloom in February and early March 2015.

Opinion of the Scientific Committee on Consumer Safety (SCCS) - Revision of the opinion on the safety of the use of Silica, Hydrated Silica, and Silica Surface Modified with Alkyl Silylates (nano form) in cosmetic products.

CONCLUSION OF THE OPINION: The SCCS has concluded that the evidence, both provided in the submission and that available in scientific literature, is inadequate and insufficient to allow drawing any firm conclusion either for or against the safety of any of the individual SAS material, or any of the SAS categories that are intended for use in cosmetic products. As the SCCS has not been able to conclude on the safety of the synthetic amorphous silica (SAS) materials included in the current submission, the Applicant is advised to follow the SCCS Guidance on Risk Assessment of Nanomaterials (SCCS/1484/12). A brief summary is provided to enable/facilitate future evaluation of the SAS materials in cosmetic products.

Implementation of a high-throughput ion chromatographic assay to assess glass degradation in drug product formulations.

UNLABELLED: The primary container for parenterals is usually composed of glass. Given the recent industry-wide spike in glass-related problems, assays capable of detecting glass degradation before glass-related particles are visible in solution have practical significance. A rapid, high-throughput ion chromatography method coupled with molybdate reaction is described here for detection and quantitation of silicic acid (soluble form of silica) in complex samples. The method involves ion exchange separation of the silicate anion at high pH followed by a post-column derivatization step with sodium molybdate reagent. The resulting molybdo-silicate complex is detected with high sensitivity in the visible wavelength range at 410 nm and correlates to the level of soluble silica in solution. This assay is high-throughput and amenable for implementation during the early phase of product development. The assay provides a direct measurement to assess potential incompatibility between the formulation and its glass container. The Si levels measured by this method showed a direct correlation to the vial surface morphology changes as monitored by differential interference contrast microscopy. LAY ABSTRACT: Recently, the pharmaceutical industry has been faced with glass quality challenges that have resulted in many products being recalled from the market. Monitoring levels of soluble silica in solution is critical because silica is the primary component of glass containers used in the pharmaceutical industry. Given this recent industry-wide increase in glass-related problems, assays capable of detecting glass degradation before glass-related particles are visible in solution have practical significance. A rapid assay to detect the soluble form of silica is presented here. The method presented will enable earlier detection of a formulation and container incompatibility instead of waiting until glass-related particles are visible in solution.

Spectrometric analysis of process etching solutions of the photovoltaic industry--determination of HNO3, HF, and H2SiF6 using high-resolution continuum source absorption spectrometry of diatomic molecules and atoms.

The surface of raw multicrystalline silicon wafers is treated with HF-HNO(3) mixtures in order to remove the saw damage and to obtain a well-like structured surface of low reflectivity, the so-called texture. The industrial production of solar cells requires a consistent level of texturization for tens of thousands of wafers. Therefore, knowing the actual composition of the etch bath is a key element in process control in order to maintain a certain etch rate through replenishment of the consumed acids. The present paper describes a novel approach to quantify nitric acid (HNO(3)), hydrofluoric acid (HF), and hexafluosilicic acid (H(2)SiF(6)) using a high-resolution continuum source graphite furnace absorption spectrometer. The concentrations of Si (via Si atom absorption at the wavelength 251.611 nm, m(0),(Si)=130 pg), of nitrate (via molecular absorption of NO at the wavelength 214.803 nm, [Formula: see text] ), and of total fluoride (via molecular absorption of AlF at the wavelength 227.46 nm, m(0,F)=13 pg) were measured against aqueous standard solutions. The concentrations of H(2)SiF(6) and HNO(3) are directly obtained from the measurements. The HF concentration is calculated from the difference between the total fluoride content, and the amount of fluoride bound as H(2)SiF(6). H(2)SiF(6) and HNO(3) can be determined with a relative uncertainty of less than 5% and recoveries of 97-103% and 96-105%, respectively. With regards to HF, acceptable results in terms of recovery and uncertainty are obtained for HF concentrations that are typical for the photovoltaic industry. The presented procedure has the unique advantage that the concentration of both, acids and metal impurities in etch solutions, can be routinely determined by a single analytical instrument.

Nutrient loads and their impacts on chlorophyll a in the Mae Klong River and estuarine ecosystem: an approach for nutrient criteria development.

Investigations on the water quality of the Mae Klong River and Estuary were conducted from April 2005 to February 2006 during periods of early-, mid-, and late-loading. Nutrient loads and transfer patterns were studied together with clarification of contaminated sites. The results indicated that NH4+, NO2- + NO3-, Si(OH)4 and PO4(3-) concentrations varied by season and were comparatively high in the mid-loading period. Analysis of DIN:P and Si:P molar ratios indicated that P04(3-) could possibly be a limiting nutrient. Highly contaminated sites were in the middle (Ratchaburi province) and lower (Samut Songkhram province) river zones in which anthropogenic wastewater discharges were significantly (p < 0.05) loaded. Analysis of the DIN and P transfer patterns showed that self-remediation efficiencies were rarely found. The highest DIN and P loads of 23.87 and 4.03 t/day, respectively, were found in Samut Songkhram province. Nutrients were found to contribute to the hypertrophic condition of the lower river and the estuary. The baseline level of chlorophyll a in the upper river was approximately 3.3 microg/L, while levels exceeded 10 microg/L in the estuarine zone. Such chlorophyll a levels were highly significant (p < 0.01) related to DIN and P (with correlation coefficients of 0.44 and 0.37, respectively). In order to maintain river conservation to an acceptable degree, levels of about 20 micromol/L DIN and 1 micromol/L P were suggested as the upper limits. To achieve such levels will require serious consideration with regard to the development of nutrient criteria for water resource conservation management and sustainable utilization purposes.

Fatal cases of acute suicidal sodium and accidental zinc fluorosilicate poisoning. Review of acute intoxications due to fluoride compounds.

Fluoride, of all inorganic substances, is among the least likely to be identified by a routine toxicological analysis. Acute poisonings with salts of hydrofluoric or fluorosilicic acid, however, although relatively uncommon, may occur. Some fluorosilicates, salts of fluorosilicic acid (e.g. Al, Zn, Pb, Mg) are used as stone consolidants, others (e.g. sodium fluorosilicate)--in the production of enamel and milk glass, or as insecticide. In this paper, two fatal cases of poisonings are presented: a suicide involving sodium fluorosilicate of a 39-year-old male who died in his flat, without hospitalization, and an accidental ingestion of zinc fluorosilicate solution (probably due to mistaking it for mineral water) by a 38-year-old male at his workplace (building), who died about 3h after ingestion of the liquid, in spite of intensive care at hospitals. Post-mortem samples were examined by the use of the spectrophotometric method with lanthanum nitrate and alizarin complexone for fluorine (after isolation of fluoride compounds by the microdiffusion method) and using a flame atomic absorption spectrometry method for zinc (after mineralization of biological material by sulfuric and nitric acids). In the first case, the results were: blood--130 µg F/ml, stomach--1150 µg F/g, small intestine content --19.6 µg F/g, kidney--56.0 µg F/g, and urine--1940 µg F/ml. In the second case, the contents of fluorine and zinc in blood and internal organs were the following: blood--6.03 µg F/ml, 23.8 µg Zn/ml; brain--1.39 µg F/g, 7.54 µg Zn/g; stomach--152 µg Zn/g; stomach content--293 µg F/g, 84.4 µg Zn/g; small intestine--37.5 µg Zn/g; small intestine content--63.4 µg F/g, 19.6 µg Zn/g; liver--9.49 µg F/g, 81.0 µg Zn/g; kidney--29.6 µg F/g, 39.2 µg Zn/g; and exceeded the normal levels of these elements in biological material many times. In addition, in stomach and liver large amounts of silica were detected. In the paper, a review of acute intoxications with various fluoride compounds (17 cases) is also presented.

Glacial silicic acid concentrations in the Southern Ocean.

Reconstruction of nutrient concentrations in the deep Southern Ocean has produced conflicting results. The cadmium/calcium (Cd/Ca) data set suggests little change in nutrient concentrations during the last glacial period, whereas the carbon isotope data set suggests that nutrient concentrations were higher. We determined the silicon isotope composition of sponge spicules from the Atlantic and Pacific sectors of the Southern Ocean and found higher silicic acid concentrations in the Pacific sector during the last glacial period. We propose that this increase results from changes in the stoichiometric uptake of silicic acid relative to nitrate and phosphate by diatoms, thus facilitating a redistribution of nutrients across the Pacific and Southern Oceans. Our results are consistent with the global Cd/Ca data set and support the silicic acid leakage hypothesis.

Recovery of high surface area mesoporous silica from waste hexafluorosilicic acid (H2SiF6) of fertilizer industry.

In this article we report recovery of mesoporous silica from the waste material (hexafluorosilicic acid) of phosphate fertilizer industry. The process involves the reaction of hexafluorosilicic acid (50 ml, 24 wt% H(2)SiF(6)) and 100ml, 0.297 M Na(2)CO(3) to generate the alkaline aqueous slurry. Silica was separated from the slurry by filtration and the sodium fluoride was extracted from the aqueous solution by evaporation method. The obtained mesoporous silica was characterized by N(2) absorption/desorption (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), and EDS. The results confirm that the separation of silica and NaF was successful and the final products have high purity. The silica product was found to have an average pore diameter of 4.14 nm and a high surface area (up to 800 m(2)/g). The process reported in this study may significantly reduce the release of hazardous materials into the environment and it might confer economic benefits to the responsible industries.

Mitigation of arsenic accumulation in rice with water management and silicon fertilization.

Rice represents a major route of As exposure in populations that depend on a rice diet. Practical measures are needed to mitigate the problem of excessive As accumulation in paddy rice. Two potential mitigation methods, management of the water regime and Si fertilization, were investigated under greenhouse conditions. Growing rice aerobically during the entire rice growth duration resulted in the leastAs accumulation. Maintaining aerobic conditions during either vegetative or reproductive stage of rice growth also decreased As accumulation in rice straw and grain significantly compared with rice grown under flooded conditions. The effect of water management regimes was consistent with the observed effect of flooding-induced arsenite mobilization in the soil solution. Aerobic treatments increased the percentage of inorganic As in grain, but the concentrations of inorganic As remained lower than in the flooded rice. Silicon fertilization decreased the total As concentration in straw and grain by 78 and 16%, respectively, even though Si addition increased As concentration in the soil solution. Silicon also significantly influenced As speciation in rice grain and husk by enhancing methylation. Silicon decreased the inorganic As concentration in grain by 59% while increasing the concentration of dimethylarsinic acid (DMA) by 33%. There were also significant differences between two rice genotypes in grain As speciation. This study demonstrated that water management Si fertilization, and selection of rice cultivars are effective measures that can be used to reduce As accumulation in rice.

Arsenic in rice (Oryza sativa L.) related to dynamics of arsenic and silicic acid in paddy soils.

Paddy rice is a global staple food which in some circumstances can contain high levels of the toxic element arsenic (As). In order to elucidate factors influencing As dissolution in the soil solution during paddy rice cultivation, rice (Oryza sativa L. "Selenio") was cultivated to maturity in six paddy soils in the greenhouse in 2005 and 2006. Concentrations of Mn, Fe, As, P, and silicic acid in soil solution and As concentrations in rice straw and polished rice grain were determined. There was a close relationship between Fe and As concentrations in the soil solution, suggesting that the major part of dissolved As originated from reduced iron-(hydr)oxide. However, in addition to the factors causing As dissolution in the soil, other factors influenced the uptake of As by rice. The inhibitory effect of indigenous silicic acid in the soil solution on As uptake was clearly shown. This implied that soils with high plant available Si contents resulted in low plant As contents and that Si application to soils may decrease the As content of rice.

Chemical composition of Coscinodiscus wailesii and the implication for nutrient ratios in a coastal water, Seto Inland Sea, Japan.

Chemical compositions of Coscinodiscus wailesii were determined for four samples of natural cells. Results revealed that the cellular Si:N ratio of C. wailesii cell was 2.4:1.0-5.2:1.0. The impacts of C. wailesii on surrounding coastal water were evaluated from hydrographic observations, in which C. wailesii cell density, nutrients concentrations and temperature were monitored from November 2001 to February 2005 in Harima-Nada, the Seto Inland Sea, Japan. In low temperature periods, from October to December, two peaks of C. wailesii cell density were observed and nutrient concentrations were depleted. The draw-down ratio of Si(OH)(4) and DIN (Si(OH)(4):DIN ratio) in the water column were similar to the cellular Si:N ratio of C. wailesii cells, which have high Si contents. In addition the effects of different Si(OH)(4):DIN ratio were determined for in situ bottle incubation experiments. In the culture experiments, picoplankton (0.2-2.0 microm) which consisted of small flagellates became dominant under low Si(OH)(4):DIN ratios. These results suggested that the sizes distribution shifted to small size and the phytoplankton community was changed to small flagellates after the C. wailesii bloom. These changes would influence predators at higher trophic levels in its coastal ecosystem.

Seasonal dynamics of the endosymbiotic, nitrogen-fixing cyanobacterium Richelia intracellularis in the eastern Mediterranean Sea.

Biological nitrogen fixation has been suggested as an important source of nitrogen for the ultra-oligotrophic waters of the Levantine Basin of the Mediterranean Sea. In this study, we identify and characterize the spatial and temporal distribution of the N-fixing (diazotrophic) cyanobacterium Richelia intracellularis. R. intracellularis is usually found as an endosymbiont within diatoms such as Rhizosolenia spp and Hemiaulus spp. and is an important diazotroph in marine tropical oceans. In this study, two stations off the Mediterranean coast of Israel were sampled monthly during 2005-2007. R. intracellularis was identified by microscopy and by reverse transcribed-PCR which confirmed a 98.8% identity with known nifH sequences of R. intracellularis from around the world. The diatom-diazotroph associations were found throughout the year peaking during autumn (October-November) at both stations. Abundance of R. intracellularis ranged from 10 to 55 heterocysts l(-1) and correlated positively with the dissolved Si(OH)(4)/(NO(3)+NO(2)) ratio in surface waters. Although the rates of nitrogen fixation were very low, averaging approximately 1.1 nmol N l(-1) day(-1) for the R. intracellularis size fraction (>10 microm) from surface waters, they correlated positively with heterocyst counts during thermal stratification. The lack of large-scale diatom-diazotroph blooms and the low rates of nitrogen fixation by these diazotrophs may result from the P-starved conditions affecting the Levantine basin.

Recent comparability of oceanographic nutrients data: results of a 2003 intercomparison exercise using reference materials.

An intercomparison exercise was conducted using the recently developed Reference Material for Nutrients in Seawater (RMNS). Discrepancies of reported values among laboratories were greater than the homogeneity of RMNS samples and the reported analytical precision of nutrients. The variability of in-house standards of the participating laboratories might be the most likely source of interlaboratory discrepancies. Therefore, the use of common reference materials, i.e. certified RM, is essential to establish and improve the comparability of nutrient data of the world's oceans.

Mesoscale eddies drive increased silica export in the subtropical Pacific Ocean.

Mesoscale eddies may play a critical role in ocean biogeochemistry by increasing nutrient supply, primary production, and efficiency of the biological pump, that is, the ratio of carbon export to primary production in otherwise nutrient-deficient waters. We examined a diatom bloom within a cold-core cyclonic eddy off Hawaii. Eddy primary production, community biomass, and size composition were markedly enhanced but had little effect on the carbon export ratio. Instead, the system functioned as a selective silica pump. Strong trophic coupling and inefficient organic export may be general characteristics of community perturbation responses in the warm waters of the Pacific Ocean.

A new method for nanomolar determination of silicic acid in seawater.

A novel method is proposed to determine concentrations of silicic acid in seawater in the nanomolar range of 3-500 nM. It preconcentrates silicic acid through a "Magnesium Induced Co-precipitation" (MAGIC) step before a classical spectrophotometric measurement. The detection limit (3+/-2 nM) is improved by a factor 10 in comparison to the conventional colorimetric methods. The best precision obtained to date is +/-2 nM for a natural sample of 69 nM Si. No interference of phosphate was observed by contrast to previous methods. This simple method offers a simple, sensitive and accurate tool for silicic acid determination in depleted seawater, where its availability remains unknown.

Partial prevention of long-term femoral bone loss in aged ovariectomized rats supplemented with choline-stabilized orthosilicic acid.

Silicon (Si) deficiency in animals results in bone defects. Choline-stabilized orthosilicic acid (ch-OSA) was found to have a high bioavailability compared to other Si supplements. The effect of ch-OSA supplementation was investigated on bone loss in aged ovariectomized (OVX) rats. Female Wistar rats (n = 58, age 9 months) were randomized in three groups. One group was sham-operated (sham, n = 21), and bilateral OVX was performed in the other two groups. OVX rats were supplemented orally with ch-OSA over 30 weeks (OVX1, n = 20; 1 mg Si/kg body weight daily) or used as controls (OVX0, n = 17). The serum Si concentration and the 24-hour urinary Si excretion of supplemented OVX rats was significantly higher compared to sham and OVX controls. Supplementation with ch-OSA significantly but partially reversed the decrease in Ca excretion, which was observed after OVX. The increase in bone turnover in OVX rats tended to be reduced by ch-OSA supplementation. ch-OSA supplementation increased significantly the femoral bone mineral content (BMC) in the distal region and total femoral BMC in OVX rats, whereas lumbar BMC was marginally increased. Femoral BMD was significantly increased at two sites in the distal region in OVX rats supplemented with ch-OSA compared to OVX controls. Total lumbar bone mineral density was marginally increased by ch-OSA supplementation. In conclusion, ch-OSA supplementation partially prevents femoral bone loss in the aged OVX rat model.

Dissolved trace element concentrations in the East River-Long Island Sound system: relative importance of autochthonous versus allochthonous sources.

Dissolved trace metal (Ag, Cd, Cu, Fe, Ni, Pb, and Zn), inorganic nutrient (NO3, NH4, PO4, H4SiO4), and DOC concentrations were measured at 43 stations during low (July 2000) and high (April 2001) river discharge conditions in surface waters of Long Island Sound (LIS). To evaluate the impact of fluvial sources to the total metal budget of the sound, samples were collected from major tributaries discharging into LIS (Thames, Quinnipiac, Housatonic, Connecticut, and East Rivers). To compare LIS with other coastal embayments, samples were also collected from five LIS coastal embayments (Manhassett Bay, Huntington Harbor, Oyster Bay, Hempstead Harbor, and Port Jefferson Harbor), which are monitored by the U.S. National Status and Trends Program. Metal and nutrient distributions identified two biogeochemical regimes within LIS: an area of relatively high nutrient and metal concentrations in the East River/Narrows region in western LIS and an area in the eastern region of the sound that had comparatively lower concentrations. Mass balance estimates indicated that, during low flow conditions, the East River was the dominant allochthonous source of most trace metals (Ag, Cd, Cu, Ni, Zn) and inorganic nutrients (NO3 and PO4); during high flow conditions, the most influential source of these constituents was the Connecticut River. Mass balance estimates also evidenced a large autochthonous source of Cu, Ni, and Zn, as their spatial distributions displayed elevated concentrations away from point sources such as the East River. Principal component analysis suggested that metal and nutrient distributions in the LIS system were influenced by different seasonal processes: remobilization from contaminated sediments, anthropogenic inputs from sewage discharges and phytoplankton scavenging during the spring freshet, and benthic remobilization during summer conditions.