WorldWideScience

Sample records for crystalline silica exposure

  1. Exposure to crystalline silica in abrasive blasting operations where silica and non-silica abrasives are used.

    Science.gov (United States)

    Radnoff, Diane L; Kutz, Michelle K

    2014-01-01

    Exposure to respirable crystalline silica is a hazard common to many industries in Alberta but particularly so in abrasive blasting. Alberta occupational health and safety legislation requires the consideration of silica substitutes when conducting abrasive blasting, where reasonably practicable. In this study, exposure to crystalline silica during abrasive blasting was evaluated when both silica and non-silica products were used. The crystalline silica content of non-silica abrasives was also measured. The facilities evaluated were preparing metal products for the application of coatings, so the substrate should not have had a significant contribution to worker exposure to crystalline silica. The occupational sampling results indicate that two-thirds of the workers assessed were potentially over-exposed to respirable crystalline silica. About one-third of the measurements over the exposure limit were at the work sites using silica substitutes at the time of the assessment. The use of the silica substitute, by itself, did not appear to have a large effect on the mean airborne exposure levels. There are a number of factors that may contribute to over-exposures, including the isolation of the blasting area, housekeeping, and inappropriate use of respiratory protective equipment. However, the non-silica abrasives themselves also contain silica. Bulk analysis results for non-silica abrasives commercially available in Alberta indicate that many contain crystalline silica above the legislated disclosure limit of 0.1% weight of silica per weight of product (w/w) and this information may not be accurately disclosed on the material safety data sheet for the product. The employer may still have to evaluate the potential for exposure to crystalline silica at their work site, even when silica substitutes are used. Limited tests on recycled non-silica abrasive indicated that the silica content had increased. Further study is required to evaluate the impact of product recycling

  2. Exposure to respirable crystalline silica in South African farm workers

    Energy Technology Data Exchange (ETDEWEB)

    Swanepoel, Andrew; Rees, David [University of the Witwatersrand, School of Public Health, Johannesburg (South Africa); Renton, Kevin [National Institute for Occupational Health, Johannesburg (South Africa); Kromhout, Hans, E-mail: andrew.swanepoel@wits.ac.z [Environmental Epidemiology Division, Institute for Risk Assessment Sciences, University of Utrecht (Netherlands)

    2009-02-01

    Although listed in some publications as an activity associated with silica (quartz) exposure, agriculture is not widely recognized as an industry with a potential for silica associated diseases. Because so many people work in agriculture; and because silica exposure and silicosis are associated with serious diseases such as tuberculosis (TB), particular in those immunological compromised by the Human immunodeficiency virus (HIV), silica exposure in agriculture is potentially very important. But in South Africa (SA) very little is known about silica exposure in this industry. The objectives of this project are: (a) to measure inhalable and respirable dust and its quartz content on two typical sandy soil farms in the Free State province of SA for all major tasks done on the farms; and (b) to characterise the mineralogy soil type of these farms. Two typical farms in the sandy soil region of the Free State province were studied. The potential health effects faced by these farm workers from exposure to respirable crystalline silica are discussed.

  3. Crystalline Silica Primer

    Science.gov (United States)

    ,

    1992-01-01

    Crystalline silica is the scientific name for a group of minerals composed of silicon and oxygen. The term crystalline refers to the fact that the oxygen and silicon atoms are arranged in a threedimensional repeating pattern. This group of minerals has shaped human history since the beginning of civilization. From the sand used for making glass to the piezoelectric quartz crystals used in advanced communication systems, crystalline silica has been a part of our technological development. Crystalline silica's pervasiveness in our technology is matched only by its abundance in nature. It's found in samples from every geologic era and from every location around the globe. Scientists have known for decades that prolonged and excessive exposure to crystalline silica dust in mining environments can cause silicosis, a noncancerous lung disease. During the 1980's, studies were conducted that suggested that crystalline silica also was a carcinogen. As a result of these findings, crystalline silica has been regulated under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS). Under HCS, OSHAregulated businesses that use materials containing 0.1% or more crystalline silica must follow Federal guidelines concerning hazard communication and worker training. Although the HCS does not require that samples be analyzed for crystalline silica, mineral suppliers or OSHAregulated

  4. Field evaluation of an engineering control for respirable crystalline silica exposures during mortar removal.

    Science.gov (United States)

    Collingwood, Scott; Heitbrink, William A

    2007-11-01

    During mortar removal with a right angle grinder, a building renovation process known as "tuck pointing," worker exposures to respirable crystalline silica can be as high as 5 mg/m(3), 100 times the recommended exposure limit developed by the National Institute for Occupational Safety and Health. To reduce the risk of silicosis among these workers, a vacuum cleaner can be used to exhaust 80 ft(3)/min (2.26 m(3)/min) from a hood mounted on the grinder. Field trials examined the ability of vacuum cleaners to maintain adequate exhaust ventilation rates and measure exposure outcomes when using this engineering control. These field trials involved task-based exposure measurement of respirable dust and crystalline silica exposures during mortar removal. These measurements were compared with published exposure data. Vacuum cleaner airflows were obtained by measuring and digitally logging vacuum cleaner static pressure at the inlet to the vacuum cleaner motor. Static pressures were converted to airflows based on experimentally determined fan curves. In two cases, video exposure monitoring was conducted to study the relationship between worker activities and dust exposure. Worker activities were video taped concurrent with aerosol photometer measurement of dust exposure and vacuum cleaner static pressure as a measure of airflow. During these field trials, respirable crystalline silica exposures for 22 samples had a geometric mean of 0.06 mg/m(3) and a range of less than 0.01 to 0.86 mg/m(3). For three other studies, respirable crystalline silica exposures during mortar removal have a geometric means of 1.1 to 0.35. Although this field study documented noticeably less exposure to crystalline silica, video exposure monitoring found that the local exhaust ventilation provided incomplete dust control due to low exhaust flow rates, certain work practices, and missing mortar. Vacuum cleaner airflow decrease had a range of 3 to 0.4 ft(3)/min (0.08 to 0.01 m(3)/sec(2)) over a range

  5. Occupational exposure to crystalline silica and gastric cancer: a systematic review and meta-analysis.

    Science.gov (United States)

    Lee, Wanhyung; Ahn, Yeon-Soon; Lee, Seunghyun; Song, Bo Mi; Hong, Seri; Yoon, Jin-Ha

    2016-11-01

    Crystalline silica is a widely used industrial material that is readily available worldwide, and is one of the most common types of particulate mineral pollutants. It has been classified as a group 1 human carcinogen of the respiratory system; however, whether it is linked to gastric cancer remains uncertain. We conducted a systemic review and meta-analyses to search for evidence of the relationship between gastric cancer and occupational exposure to crystalline silica. We searched for articles on occupations involving silica exposure and gastric cancer studies up to December 2014. Pooled-risk estimates of the association between occupational crystalline silica exposure and risk of gastric cancer were calculated by a random effects model. Metaregression analyses of industry type and histological confirmation status, study design and industrial subgroup analyses were performed. 29 articles, including 9 case-control and 20 cohort studies, were analysed. The overall summary effects size was 1.25 (95% CI 1.18 to 1.34) for the association of occupational silica exposure with gastric cancer. Both heterogeneity and publication bias were partially attenuated after subgroup analyses. Heterogeneity of studies was attenuated after metaregression by industry. Higher overall effects were observed in the mining and foundry industries. We found a significant relationship between occupational crystalline silica exposure and gastric cancer. Our results were strengthened by various subgroup analyses and, considering the biological plausibility of our premise, further studies are required to better understand this association. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  6. Assessment of Occupational Exposure to Dust and Crystalline Silica in Foundries

    OpenAIRE

    Ali OMIDIANIDOST; Mehdi GHASEMKHANI; Azari, Mansour R.; Golbabaei,Farideh

    2015-01-01

    Background: The term “crystalline silica” refers to crystallized form of SiO2 and quartz, as the most abundant compound on the earth’s crust; it is capable of causing silicosis and lung cancer upon inhaling large doses in the course of occupational exposure. The aim of this study was to assess occupational exposure to dust and crystalline silica in foundries in Pakdasht, Iran. Materials and Methods: In this study, airborne dust samples were collected on PVC filters (37 mm diameter, 0.8 mm por...

  7. Quantitative crystalline silica exposure assessment for a historical cohort epidemiologic study in the German porcelain industry.

    Science.gov (United States)

    Birk, Thomas; Guldner, Karlheinz; Mundt, Kenneth A; Dahmann, Dirk; Adams, Robert C; Parsons, William

    2010-09-01

    A time-dependent quantitative exposure assessment of silica exposure among nearly 18,000 German porcelain workers was conducted. Results will be used to evaluate exposure-response disease risks. Over 8000 historical industrial hygiene (IH) measurements with original sampling and analysis protocols from 1954-2006 were obtained from the German Berufs- genossenschaft der keramischen-und Glas-Industrie (BGGK) and used to construct a job exposure matrix (JEM). Early measurements from different devices were converted to modern gravimetric equivalent values. Conversion factors were derived from parallel historical measurements and new side-by-side measurements using historical and modern devices in laboratory dust tunnels and active workplace locations. Exposure values were summarized and smoothed using LOESS regression; estimates for early years were derived using backward extrapolation techniques. Employee work histories were merged with JEM values to determine cumulative crystalline silica exposures for cohort members. Average silica concentrations were derived for six primary similar exposure groups (SEGs) for 1938-2006. Over 40% of the cohort accumulated 1 mg/m(3)-years. Nearly 5000 workers had cumulative crystalline silica estimates >1.5 mg/m(3)-years. Similar numbers of men and women fell into each cumulative exposure category, except for 1113 women and 1567 men in the highest category. Over half of those hired before 1960 accumulated >3 mg/m(3)-years crystalline silica compared with 4.9% of those hired after 1960. Among those ever working in the materials preparation area, half accumulated >3 mg/m(3)-year compared with 12% of those never working in this area. Quantitative respirable silica exposures were estimated for each member of this cohort, including employment periods for which sampling used now obsolete technologies. Although individual cumulative exposure estimates ranged from background to about 40 mg/m(3)-years, many of these estimates reflect long

  8. Silicosis mortality trends and new exposures to respirable crystalline silica - United States, 2001-2010.

    Science.gov (United States)

    Bang, Ki Moon; Mazurek, Jacek M; Wood, John M; White, Gretchen E; Hendricks, Scott A; Weston, Ainsley

    2015-02-13

    Silicosis is a preventable occupational lung disease caused by the inhalation of respirable crystalline silica dust and can progress to respiratory failure and death. No effective specific treatment for silicosis is available; patients are provided supportive care, and some patients may be considered for lung transplantation. Chronic silicosis can develop or progress even after occupational exposure has ceased. The number of deaths from silicosis declined from 1,065 in 1968 to 165 in 2004. Hazardous occupational exposures to silica dust have long been known to occur in a variety of industrial operations, including mining, quarrying, sandblasting, rock drilling, road construction, pottery making, stone masonry, and tunneling operations. Recently, hazardous silica exposures have been newly documented during hydraulic fracturing of gas and oil wells and during fabrication and installation of engineered stone countertops. To describe temporal trends in silicosis mortality in the United States, CDC analyzed annual multiple cause-of-death data for 2001-2010 for decedents aged ≥15 years. During 2001-2010, a total of 1,437 decedents had silicosis coded as an underlying or contributing cause of death. The annual number of silicosis deaths declined from 164 (death rate† = 0.74 per 1 million population) in 2001 to 101 (0.39 per 1 million) in 2010 (p = 0.002). Because of new operations and tasks placing workers at risk for silicosis, efforts to limit workplace exposure to crystalline silica need to be maintained.

  9. Respirable crystalline silica exposures during asphalt pavement milling at eleven highway construction sites.

    Science.gov (United States)

    Hammond, Duane R; Shulman, Stanley A; Echt, Alan S

    2016-07-01

    Asphalt pavement milling machines use a rotating cutter drum to remove the deteriorated road surface for recycling. The removal of the road surface has the potential to release respirable crystalline silica, to which workers can be exposed. This article describes an evaluation of respirable crystalline silica exposures to the operator and ground worker from two different half-lane and larger asphalt pavement milling machines that had ventilation dust controls and water-sprays designed and installed by the manufacturers. Manufacturer A completed milling for 11 days at 4 highway construction sites in Wisconsin, and Manufacturer B completed milling for 10 days at 7 highway construction sites in Indiana. To evaluate the dust controls, full-shift personal breathing zone air samples were collected from an operator and ground worker during the course of normal employee work activities of asphalt pavement milling at 11 different sites. Forty-two personal breathing zone air samples were collected over 21 days (sampling on an operator and ground worker each day). All samples were below 50 µg/m(3) for respirable crystalline silica, the National Institute for Occupational Safety and Health recommended exposure limit. The geometric mean personal breathing zone air sample was 6.2 µg/m(3) for the operator and 6.1 µg/m(3) for the ground worker for the Manufacturer A milling machine. The geometric mean personal breathing zone air sample was 4.2 µg/m(3) for the operator and 9.0 µg/m(3) for the ground worker for the Manufacturer B milling machine. In addition, upper 95% confidence limits for the mean exposure for each occupation were well below 50 µg/m(3) for both studies. The silica content in the bulk asphalt material being milled ranged from 7-23% silica for roads milled by Manufacturer A and from 5-12% silica for roads milled by Manufacturer B. The results indicate that engineering controls consisting of ventilation controls in combination with water-sprays are

  10. Development of an exposure matrix for respirable crystalline silica in the British pottery industry.

    Science.gov (United States)

    Burgess, G L

    1998-04-01

    Processes associated with occupational exposure to respirable crystalline silica in the British pottery industry were investigated to develop estimates of worker exposures from 1930 to 1995. Information was derived from more than 1300 air samples, published literature and unpublished reports of dust control innovations and process changes. A matrix was developed specifically to support a mortality study of 5115 pottery workers in North Staffordshire, UK. Matrix values range from 2 micrograms/m3 for pottery support activities performed in the 1990s to 800 micrograms/m3 for firing activities in the 1930s. Although exposure estimates within decade varied, median concentrations for all process categories displayed an overall trend towards progressive reduction in exposure during the 65 year span. Potential methods to validate the matrix as well as sources of error are discussed.

  11. Bioreactivity of the crystalline silica polymorphs, quartz and cristobalite, and implications for occupational exposure limits (OELs).

    Science.gov (United States)

    Mossman, Brooke T; Glenn, Robert E

    2013-09-01

    Silica or silicon dioxides (SiO₂) are naturally occurring substances that comprise the vast majority of the earth's crust. Because of their prevalence and commercial applications, they have been widely studied for their potential to induce pulmonary fibrosis and other disorders. Historically, the focus in the workplace has been on the development of inflammation and fibrotic lung disease, the basis for promulgating workplace standards to protect workers. Crystalline silica (CS) polymorphs, predominantly quartz and cristobalite, are used in industry but are different in their mineralogy, chemistry, surface features, size dimensions and association with other elements naturally and during industrial applications. Epidemiologic, clinical and experimental studies in the literature historically have predominantly focused on quartz polymorphs. Thus, in this review, we summarize past scientific evaluations and recent peer-reviewed literature with an emphasis on cristobalite, in an attempt to determine whether quartz and cristobalite polymorphs differ in their health effects, toxicity and other properties that may dictate the need for various standards of protection in the workplace. In addition to current epidemiological and clinical reports, we review in vivo studies in rodents as well as cell culture studies that shed light on mechanisms intrinsic to the toxicity, altered cell responses and protective or defense mechanisms in response to these minerals. The medical and scientific literature indicates that the mechanisms of injury and potential causation of inflammation and fibrotic lung disease are similar for quartz and cristobalite. Our analysis of these data suggests similar occupational exposure limits (OELs) for these minerals in the workplace.

  12. Exposure to respirable dust and crystalline silica in bricklaying education at Dutch vocational training centers.

    NARCIS (Netherlands)

    Huizer, D.; Spee, T.; Lumens, M.E.G.L.; Kromhout, H.

    2010-01-01

    BACKGROUND: Construction workers are educated at vocational training centers before they begin their working lives. Future bricklayers and their instructors are exposed to respirable dust and possibly to hazardous respirable crystalline silica from trial mortar. METHODS: Thirty-six personal air samp

  13. Quantitative exposure matrix for asphalt fume, total particulate matter, and respirable crystalline silica among roofing and asphalt manufacturing workers.

    Science.gov (United States)

    Fayerweather, William E; Trumbore, David C; Johnson, Kathleen A; Niebo, Ronald W; Maxim, L Daniel

    2011-09-01

    This paper summarizes available data on worker exposures to asphalt fume (soluble fraction), total particulate matter, and respirable crystalline silica (quartz) [hereinafter RCS] over a 30-year period in Owens Corning's asphalt production and roofing manufacturing plants. For the period 1977 through 2006, the air-monitoring database contains more than 1,400 personal samples for asphalt fume (soluble fraction), 2,400 personal samples for total particulate, and 1,300 personal samples for RCS. Unique process-job categories were identified for the asphalt production and roofing shingle manufacturing plants. Quantitative exposures were tabulated by agent, process-job, and calendar period to form an exposure matrix for use in subsequent epidemiologic studies of the respiratory health of these workers. Analysis of time trends in exposure data shows substantial and statistically significant exposure reductions for asphalt fume (soluble fraction), total particulate matter, and respirable crystalline silica at Owens Corning plants. Cumulative distribution plots for the most recent sampling period (2001-2006) show that 95% of the asphalt fume (soluble fraction) measurements were less than 0.25 mg/m3; 95% of the total particulate measurements were less than 2.2 mg/m3; and 95% of the RCS measurements were less than 0.05 mg/m3. Several recommendations are offered to improve the design of future monitoring efforts.

  14. Will the Occupational Safety and Health Administration's Proposed Standards for Occupational Exposure to Respirable Crystalline Silica Reduce Workplace Risk?

    Science.gov (United States)

    Dudley, Susan E; Morriss, Andrew P

    2015-07-01

    The Occupational Safety and Health Administration (OSHA) is developing regulations to amend existing standards for occupational exposure to respirable crystalline silica by establishing a new permissible exposure limit as well as a series of ancillary provisions for controlling exposure. This article briefly reviews OSHA's proposed regulatory approach and the statutory authority on which it is based. It then evaluates OSHA's preliminary determination of significant risk and its analysis of the risk reduction achievable by its proposed controls. It recognizes that OSHA faces multiple challenges in devising a regulatory approach that reduces exposures and health risks and meets its statutory goal. However, the greatest challenge to reducing risks associated with silica exposure is not the lack of incentives (for either employers or employees) but rather lack of information, particularly information on the relative toxicity of different forms of silica. The article finds that OSHA's proposed rule would contribute little in the way of new information, particularly since it is largely based on information that is at least a decade old--a significant deficiency, given the rapidly changing conditions observed over the last 45 years. The article concludes with recommendations for alternative approaches that would be more likely to generate information needed to improve worker health outcomes.

  15. Effectiveness of dust control methods for crystalline silica and respirable suspended particulate matter exposure during manual concrete surface grinding.

    Science.gov (United States)

    Akbar-Khanzadeh, Farhang; Milz, Sheryl A; Wagner, Cynthia D; Bisesi, Michael S; Ames, April L; Khuder, Sadik; Susi, Pam; Akbar-Khanzadeh, Mahboubeh

    2010-12-01

    Concrete grinding exposes workers to unacceptable levels of crystalline silica dust, known to cause diseases such as silicosis and possibly lung cancer. This study examined the influence of major factors of exposure and effectiveness of existing dust control methods by simulating field concrete grinding in an enclosed workplace laboratory. Air was monitored during 201 concrete grinding sessions while using a variety of grinders, accessories, and existing dust control methods, including general ventilation (GV), local exhaust ventilation (LEV), and wet grinding. Task-specific geometric mean (GM) of respirable crystalline silica dust concentrations (mg/m³ for LEV:HEPA-, LEV:Shop-vac-, wet-, and uncontrolled-grinding, while GV was off/on, were 0.17/0.09, 0.57/0.13, 1.11/0.44, and 23.1/6.80, respectively. Silica dust concentrations (mg/m³ using 100-125 mm (4-5 inch) and 180 mm (7 inch) grinding cups were 0.53/0.22 and 2.43/0.56, respectively. GM concentrations of silica dust were significantly lower for (1) GV on (66.0%) vs. off, and (2) LEV:HEPA- (99.0%), LEV:Shop-vac- (98.1%) or wet- (94.4%) vs. uncontrolled-grinding. Task-specific GM of respirable suspended particulate matter (RSP) concentrations (mg/m³ for LEV:HEPA-, LEV:Shop-vac-, wet-, and uncontrolled grinding, while GV was off/on, were 1.58/0.63, 7.20/1.15, 9.52/4.13, and 152/47.8, respectively. GM concentrations of RSP using 100-125 mm and 180 mm grinding cups were 4.78/1.62 and 22.2/5.06, respectively. GM concentrations of RSP were significantly lower for (1) GV on (70.2%) vs. off, and (2) LEV:HEPA- (98.9%), LEV:Shop-vac- (96.9%) or wet- (92.6%) vs. uncontrolled grinding. Silica dust and RSP were not significantly affected by (1) orientation of grinding surfaces (vertical vs. inclined); (2) water flow rates for wet grinding; (3) length of task-specific sampling time; or, (4) among cup sizes of 100, 115 or 125 mm. No combination of factors or control methods reduced an 8-hr exposure level to below the

  16. Silica exposure and systemic vasculitis.

    OpenAIRE

    Mulloy, Karen B

    2003-01-01

    Work in Department of Energy (DOE) facilities has exposed workers to multiple toxic agents leading to acute and chronic diseases. Many exposures were common to numerous work sites. Exposure to crystalline silica was primarily restricted to a few facilities. I present the case of a 63-year-old male who worked in DOE facilities for 30 years as a weapons testing technician. In addition to silica, other workplace exposures included beryllium, various solvents and heavy metals, depleted uranium, a...

  17. Evaluation of Respirable Crystalline Silica in High School Ceramics Classrooms

    Directory of Open Access Journals (Sweden)

    Matthew Fechser

    2014-01-01

    Full Text Available Air concentrations of respirable crystalline silica were measured in eleven (11 high school ceramics classrooms located in Salt Lake County, UT, USA. Respirable dust was collected on PVC filters using precision flow pumps and cyclone samplers (n = 44. Filters were subsequently analyzed for respirable dust and percent crystalline silica content. The geometric mean of the silica concentrations was 0.009 mg/m3 near the teacher’s work station and 0.008 mg/m3 near the kilns. The number of students in the classroom was correlated to the silica concentration in the ceramics classroom, but no correlation was found between the silica concentrations and either the size of the classroom or the age of the building. Results from this study indicate that ceramics teachers may be at an increased risk of exposure to crystalline silica based on the ACGIH TLV of 0.025 mg/m3, with an exceedance of 21%.

  18. Evaluation of Respirable Crystalline Silica in High School Ceramics Classrooms

    Science.gov (United States)

    Fechser, Matthew; Alaves, Victor; Larson, Rodney; Sleeth, Darrah

    2014-01-01

    Air concentrations of respirable crystalline silica were measured in eleven (11) high school ceramics classrooms located in Salt Lake County, UT, USA. Respirable dust was collected on PVC filters using precision flow pumps and cyclone samplers (n = 44). Filters were subsequently analyzed for respirable dust and percent crystalline silica content. The geometric mean of the silica concentrations was 0.009 mg/m3 near the teacher’s work station and 0.008 mg/m3 near the kilns. The number of students in the classroom was correlated to the silica concentration in the ceramics classroom, but no correlation was found between the silica concentrations and either the size of the classroom or the age of the building. Results from this study indicate that ceramics teachers may be at an increased risk of exposure to crystalline silica based on the ACGIH TLV of 0.025 mg/m3, with an exceedance of 21%. PMID:24464235

  19. Silica exposure and systemic vasculitis.

    Science.gov (United States)

    Mulloy, Karen B

    2003-12-01

    Work in Department of Energy (DOE) facilities has exposed workers to multiple toxic agents leading to acute and chronic diseases. Many exposures were common to numerous work sites. Exposure to crystalline silica was primarily restricted to a few facilities. I present the case of a 63-year-old male who worked in DOE facilities for 30 years as a weapons testing technician. In addition to silica, other workplace exposures included beryllium, various solvents and heavy metals, depleted uranium, and ionizing radiation. In 1989 a painful macular skin lesion was biopsied and diagnosed as leukocytoclastic vasculitis. By 1992 he developed gross hematuria and dyspnea. Blood laboratory results revealed a serum creatinine concentration of 2.1 mg/dL, ethrythrocyte sedimentation rate of 61 mm/hr, negative cANCA (antineutrophil cytoplasmic antibody cytoplasmic pattern), positive pANCA (ANCA perinuclear pattern), and antiglomerular basement membrane negative. Renal biopsy showed proliferative (crescentric) and necrotizing glomerulonephritis. The patient's diagnoses included microscopic polyangiitis, systemic necrotizing vasculitis, leukocytoclastic vasculitis, and glomerulonephritis. Environmental triggers are thought to play a role in the development of an idiopathic expression of systemic autoimmune disease. Crystalline silica exposure has been linked to rheumatoid arthritis, scleroderma, systemic lupus erythematosus, rapidly progressive glomerulonephritis and some of the small vessel vasculitides. DOE workers are currently able to apply for compensation under the federal Energy Employees Occupational Illness Compensation Program (EEOICP). However, the only diseases covered by EEOICP are cancers related to radiation exposure, chronic beryllium disease, and chronic silicosis.

  20. Risk evaluation and exposure control of mineral dust containing free crystalline silica: a study case at a quarry in the Recife Metropolitan Area.

    Science.gov (United States)

    Lira, Mario; Kohlman Rabbani, E; Barkokébas Junior, Beda; Lago, Eliane

    2012-01-01

    During the production of aggregates at quarry sites, elevated quantities of micro-particulate mineral dust are produced in all stages of the process. This dust contains appreciable amounts of free crystalline silica in a variety of forms which, if maintained suspended in the air in the work environment, expose the workers to the risk of developing occupational silicosis, which causes reduced ability to work and potential shortening of lifespan. This study was conducted to qualitatively and quantitatively evaluate workers' exposure to mineral dust containing free crystalline silica at a midsized quarry in the Recife metropolitan area, in the State of Pernambuco. It involved evaluation of the industrial process, collection and analysis of representative dust samples, and interviews with the management team of the company with the intent to assess the compliance of the company with Regulatory Standard (NR) 22--Occupational safety and health in mining. In order to assist the company in managing risks related to dust exposure, three protocols were developed, implemented and made available, the first based on NR 22, from which the company was also given an economic safety indicator, the second based on the recommendations and requirements of Fundacentro to implement a Respiratory Protection Program and, finally, an assessment protocol with respect to the guidelines of the International Labor Organization to implement a health and safety management system. This study also showed the inadequacy of the formula for calculating tolerance limits in Brazilian legislation when compared with the more strict internationally accepted control parameters. From the laboratory results, unhealthy conditions at the quarry site were confirmed and technical and administrative measures were suggested to reduce and control dust exposure at acceptable levels, such as the implementation of an occupational health and safety management system, integrated with other management systems. From these

  1. Pre-exposure of Mycobacterium tuberculosis-infected macrophages to crystalline silica impairs control of bacterial growth by deregulating the balance between apoptosis and necrosis.

    Directory of Open Access Journals (Sweden)

    Leslie Chávez-Galán

    Full Text Available Inhalation of crystalline silica (CS particles increases the risk of pulmonary tuberculosis; however, the precise mechanism through which CS exposure facilitates Mycobacterium tuberculosis (Mtb infection is unclear. We speculate that macrophage exposure to CS deregulates the cell death pathways that could explain, at least in part, the association observed between exposure to CS and pulmonary tuberculosis. We therefore established an in vitro model in which macrophages were exposed to CS and then infected with Mtb. Expression of surface markers was analyzed by flow cytometry, JNK1/2, ASK1, caspase 9, P-p38, Bcl-2 and Mcl-1 were analyzed by Western blot, and cytokines by ELISA. Our results show that exposure to CS limits macrophage ability to control Mtb growth. Moreover, this exposure reduced the expression of TLR2, Bcl-2 and Mcl-1, but increased that of JNK1 and ASK1 molecules in the macrophages. Finally, when the pre-exposed macrophages were infected with Mtb, the concentrations of TNFα, IL-1β and caspase-9 expression increased. This pro-inflammatory profile of the macrophage unbalanced the apoptosis/necrosis pathway. Taken together, these data suggest that macrophages exposed to CS are sensitized to cell death by MAPK kinase-dependent signaling pathway. Secretion of TNF-α and IL-1β by Mtb-infected macrophages promotes necrosis, and this deregulation of cell death pathways may favor the release of viable bacilli, thus leading to the progression of tuberculosis.

  2. Respirable crystalline silica - a failure to control exposureexclamation

    Energy Technology Data Exchange (ETDEWEB)

    Cain, J R, E-mail: john.cain@hse.gsi.gov.u [HM Regional Specialist Inspector (Occupational Hygiene), Health and Safety Executive, Marshalls Mill, Marshall Street, Leeds LS11 9YJ (United Kingdom)

    2009-02-01

    Several sites were visited to monitor stonemason exposure to respirable crystalline silica (RCS), inhalable dust and respirable dust. At all sites, exposure to RCS exceeded the Workplace Exposure Limit of 0.1 mg/m{sup 3} 8-hour TWA. There was therefore a continuing high risk of workers developing silicosis unless the appropriate measures were instigated to prevent or control exposure. Exposure control was ineffective at all sites e.g. water wall extraction systems were not well designed. There was evidence that foreign workers were at a greater exposure risk. But even with appropriate controls to mitigate exposure to RCS it may not be possible to sustain exposure to below 0.1 mg/m{sup 3} 8-hour TWA without on-going HSE intervention.

  3. How reliable are crystalline silica dust concentration measurements?

    Science.gov (United States)

    Cox, L A; Van Orden, D R; Lee, R J; Arlauckas, S M; Kautz, R A; Warzel, A L; Bailey, K F; Ranpuria, A K

    2015-10-01

    To determine how reliably commercial laboratories measure crystalline silica concentrations corresponding to OSHA's proposed limits, 105 filters were prepared with known masses of 20, 40, and 80 μg of respirable quartz corresponding to airborne silica concentrations of 25, 50, and 100 μg/m(3) and were submitted, in a blind test, to qualified commercial laboratories over a nine month period. Under these test conditions, the reported results indicated a lack of accuracy and precision needed to reliably inform regulatory compliance decisions. This was true even for filters containing only silica, without an interfering matrix. For 36 filters loaded with 20 or more micrograms of silica, the laboratories reported non-detected levels of silica. Inter-laboratory variability in this performance test program was so high that the reported results could not be used to reliably discriminate among filters prepared to reflect 8-h exposures to respirable quartz concentrations of 25, 50 and 100 μg/m(3). Moreover, even in intra-laboratory performance, there was so much variability in the reported results that 2-fold variations in exposure concentrations could not be reliably distinguished. Part of the variability and underreporting may result from the sample preparation process. The results of this study suggest that current laboratory methods and practices cannot necessarily be depended on, with high confidence, to support proposed regulatory standards with reliable data.

  4. Blocking the 4-1BB Pathway Ameliorates Crystalline Silica-induced Lung Inflammation and Fibrosis in Mice.

    Science.gov (United States)

    Li, Chao; Du, Sitong; Lu, Yiping; Lu, Xiaowei; Liu, Fangwei; Chen, Ying; Weng, Dong; Chen, Jie

    2016-01-01

    Long term pulmonary exposure to crystalline silica leads to silicosis that manifests progressive interstitial fibrosis, eventually leading to respiratory failure and death. Despite efforts to eliminate silicosis, clinical cases continue to occur in both developing and developed countries. The exact mechanisms of crystalline silica-induced pulmonary fibrosis remain elusive. Herein, we find that 4-1BB is induced in response to crystalline silica injury in lungs and that it is highly expressed during development of experimental silicosis. Therefore, we explore the role of 4-1BB pathway during crystalline silica-induced lung injury and find that a specific inhibitor blocking the pathway could effectively alleviate crystalline silica-induced lung inflammation and subsequent pulmonary fibrosis in vivo. Compared to controls, the treated mice exhibited reduced Th1 and Th17 responses. The concentrations of pro-inflammatory cytokines in bronchoalveolar lavage fluid (BALF), including tumor necrosis factor (TNF)-α, interferon (IFN)-γ and interleukin (IL)-17A following crystalline silica challenge were also reduced in inhibitor-treated mice. Although there was no significant alteration in Th2 cytokines of IL-4 and IL-13, another type of pro-fibrogenic cell, regulatory T cell (Treg) was significantly affected. In addition, one of the major participants in fibrogenesis, fibrocyte recruited less due to the blockade. Furthermore, we demonstrated the decreased fibrocyte recruitment was associated with chemokine reductions in lung. Our study discovers the 4-1BB pathway signaling enhances inflammatory response and promotes pulmonary fibrosis induced by crystalline silica. The findings here provide novel insights into the molecular events that control crystalline silica-induced lung inflammation and fibrosis through regulating Th responses and the recruitment of fibrocytes in crystalline silica-exposed lung.

  5. Comparison of non-crystalline silica nanoparticles in IL-1β release from macrophages

    Directory of Open Access Journals (Sweden)

    Sandberg Wiggo J

    2012-08-01

    Full Text Available Abstract Background Respirable crystalline silica (silicon dioxide; SiO2, quartz particles are known to induce chronic inflammation and lung disease upon long-term inhalation, whereas non-crystalline (amorphous SiO2 particles in the submicrometre range are regarded as less harmful. Several reports have demonstrated that crystalline, but also non-crystalline silica particles induce IL-1β release from macrophages via the NALP3-inflammasome complex (caspase-1, ASC and NALP3 in the presence of lipopolysaccharide (LPS from bacteria. Our aim was to study the potential of different non-crystalline SiO2 particles from the nano- to submicro-sized range to activate IL-1β responses in LPS-primed RAW264.7 macrophages and primary rat lung macrophages. The role of the NALP3-inflammasome and up-stream mechanisms was further explored in RAW264.7 cells. Results In the present study, we have shown that 6 h exposure to non-crystalline SiO2 particles in nano- (SiNPs, 5–20 nm, 50 nm and submicro-sizes induced strong IL-1β responses in LPS-primed mouse macrophages (RAW264.7 and primary rat lung macrophages. The primary lung macrophages were more sensitive to Si-exposure than the RAW-macrophages, and responded more strongly. In the lung macrophages, crystalline silica (MinUsil 5 induced IL-1β release more potently than the non-crystalline Si50 and Si500, when adjusted to surface area. This difference was much less pronounced versus fumed SiNPs. The caspase-1 inhibitor zYVAD and RNA silencing of the NALP3 receptor reduced the particle-induced IL-1β release in the RAW264.7 macrophages. Furthermore, inhibitors of phagocytosis, endosomal acidification, and cathepsin B activity reduced the IL-1β responses to the different particles to a similar extent. Conclusions In conclusion, non-crystalline silica particles in the nano- and submicro-size ranges seemed to induce IL-1β release from LPS-primed RAW264.7 macrophages via similar mechanisms as crystalline

  6. Crystalline silica in heated man-made vitreous fibres: a review.

    Science.gov (United States)

    Brown, Terry P; Harrison, Paul T C

    2014-02-01

    Refractory ceramic fibres (RCF) and alkaline earth silicate (AES) wools are types of man-made vitreous fibre (MMVF) that are used in demanding high-temperature industrial applications, generally above 900 °C and up to 1400 °C. When exposed to prolonged high temperatures, MMVF can devitrify with the formation of cristobalite and other crystalline silica species, which is of potential concern because crystalline silica (CS) is classified as carcinogenic. This article reviews the chemico-physical processes and morphological consequences of fibre devitrification, the forms and micro-location of CS produced, and the toxicity of devitrified fibres and the CS species formed in this way. It also examines scenarios for worker exposure to the products of fibre devitrification in industries using RCF and/or AES wools. We identify gaps in knowledge and make recommendations for future research.

  7. State-of-the-science review of the occupational health hazards of crystalline silica in abrasive blasting operations and related requirements for respiratory protection.

    Science.gov (United States)

    Madl, Amy K; Donovan, Ellen P; Gaffney, Shannon H; McKinley, Meg A; Moody, Emily C; Henshaw, John L; Paustenbach, Dennis J

    2008-08-01

    Excessive exposures to airborne crystalline silica have been known for over 100 years to pose a serious health hazard. Work practices and regulatory standards advanced as the knowledge of the hazards of crystalline silica evolved. This article presents a comprehensive historical examination of the literature on exposure, health effects, and personal protective equipment related to silica and abrasive blasting operations over the last century. In the early 1900s, increased death rates and prevalence of pulmonary disease were observed in industries that involved dusty operations. Studies of these occupational cohorts served as the basis for the first occupational exposure limits in the 1930s. Early exposure studies in foundries revealed that abrasive blasting operations were particularly hazardous and provided the basis for many of the engineering control and respiratory protection requirements that are still in place today. Studies involving abrasive blasters over the years revealed that engineering controls were often not completely effective at reducing airborne silica concentrations to a safe level; consequently, respiratory protection has always been an important component of protecting workers. During the last 15-20 yr, quantitative exposure-response modeling, experimental animal studies, and in vitro methods were used to better understand the relationship between exposure to silica and disease in the workplace. In light of Occupational Safety and Health Administration efforts to reexamine the protectiveness of the current permissible exposure limit (PEL) for crystalline silica and its focus on protecting workers who are known to still be exposed to silica in the workplace (including abrasive blasters), this state-of-the-science review of one of the most hazardous operations involving crystalline silica should provide useful background to employers, researchers, and regulators interested in the historical evolution of the recognized occupational health hazards

  8. Crystalline silica is a negative modifier of pulmonary cytochrome P-4501A1 induction

    Energy Technology Data Exchange (ETDEWEB)

    Battelli, L.A.; Ghanem, M.M.; Kashon, M.L.; Barger, M.; Ma, J.Y.C.; Simoskevitz, R.L.; Miles, P.R.; Hubbs, A.F. [NIOSH, Morgantown, WV (United States). Health Effects Laboratory Division

    2008-07-01

    Polycyclic aromatic hydrocarbons (PAHs) are products of incomplete combustion that are commonly inhaled by workers in the dusty trades. Many PAHs are metabolized by cytochrome P-4501A1 (CYP1A1), which may facilitate excretion but may activate pulmonary carcinogens. PAHs also stimulate their own metabolism by inducing CYP1A1. Recent studies suggest that respirable coal dust exposure inhibits induction of pulmonary CYP1A1 using the model PAH {beta}-naphthoflavone. The effect of the occupational particulate respirable crystalline silica was investigated on PAH-dependent pulmonary CYP1A1 induction. Male Sprague-Dawley rats were exposed to intratracheal silica or vehicle and then intraperitoneal {beta}-naphthoflavone, a CYP1A1 inducer, and/or phenobarbital, an inducer of hepatic CYP2B1, or vehicle. {beta}-Naphthoflavone induced pulmonary CYP1A1, but silica attenuated this {beta}-naphthoflavone-induced CYP1A1 activity and also suppressed the activity of CYP2B1, the major constituitive CYP in rat lung. The magnitude of CYP activity suppression was similar regardless of silica exposure dose within a range of 5 to 20 mg/rat. Phenobarbital and beta-naphthoflavone had no effect on pulmonary CYP2B1 activity. Both enzymatic immunohistochemistry and immunofluorescent staining for CYP1A1 indicated that sites of CYP1A1 induction were nonciliated airway epithelial cells, endothelial cells, and the alveolar septum. Our findings suggest that in PAH-exposed rat lung, silica is a negative modifier of CYP1A1 induction and CYP2B1 activity.

  9. Pulmonary inflammation and crystalline silica in respirable coal mine dust: dose-response

    Indian Academy of Sciences (India)

    E D Kuempel; M D Attfield; V Vallyathan; N L Lapp; J M Hale; R J Smith; V Castranova

    2003-02-01

    This study describes the quantitative relationships between early pulmonary responses and the estimated lungburden or cumulative exposure of respirable-quartz or coal mine dust. Data from a previous bronchoalveolar lavage (BAL) study in coal miners ( = 20) and nonminers ( = 16) were used including cell counts of alveolar macrophages (AMs) and polymorphonuclear leukocytes (PMNs), and the antioxidant superoxide dismutase (SOD) levels. Miners’ individual working lifetime particulate exposures were estimated from work histories and mine air sampling data, and quartz lung-burdens were estimated using a lung dosimetry model. Results show that quartz, as either cumulative exposure or estimated lung-burden, was a highly statistically significant predictor of PMN response ( < 0.0001); however cumulative coal dust exposure did not significantly add to the prediction of PMNs ( = 0.2) above that predicted by cumulative quartz exposure ( < 0.0001). Despite the small study size, radiographic category was also significantly related to increasing levels of both PMNs and quartz lung burden (-values < 0.04). SOD in BAL fluid rose linearly with quartz lung burden ( < 0.01), but AM count in BAL fluid did not ( > 0.4). This study demonstrates dose-response relationships between respirable crystalline silica in coal mine dust and pulmonary inflammation, antioxidant production, and radiographic small opacities.

  10. Engineering controls for selected silica and dust exposures in the construction industry--a review.

    Science.gov (United States)

    Flynn, Michael R; Susi, Pam

    2003-04-01

    This literature review summarizes engineering control technology research for dust and silica exposures associated with selected tasks in the construction industry. Exposure to crystalline silica can cause silicosis and lung fibrosis, and evidence now links it with lung cancer. Of over 30 references identified and reviewed, 16 were particularly significant in providing data and analyses capable of documenting the efficacy of various engineering controls. These reports include information on generation rates and worker exposures to silica and dust during four different tasks: cutting brick and concrete block, grinding mortar from between bricks, drilling, and grinding concrete surfaces. The major controls are wet methods and local exhaust ventilation. The studies suggest that while the methods provide substantial exposure reductions, they may not reduce levels below the current ACGIH threshold limit value (TLV) of 0.05 mg/m(3) for respirable quartz. Although further research on controls for these operations is indicated, it is clear that effective methods exist for significant exposure reduction.

  11. Silica dust exposures during selected construction activities.

    Science.gov (United States)

    Flanagan, Mary Ellen; Seixas, Noah; Majar, Maria; Camp, Janice; Morgan, Michael

    2003-01-01

    This study characterized exposure for dust-producing construction tasks. Eight common construction tasks were evaluated for quartz and respirable dust exposure by collecting 113 personal task period samples for cleanup; demolition with handheld tools; concrete cutting; concrete mixing; tuck-point grinding; surface grinding; sacking and patching concrete; and concrete floor sanding using both time-integrating filter samples and direct-reading respirable dust monitors. The geometric mean quartz concentration was 0.10 mg/m(3) (geometric standard deviation [GSD]=4.88) for all run time samples, with 71% exceeding the threshold limit value. Activities with the highest exposures were surface grinding, tuck-point grinding, and concrete demolition (GM[GSD] of 0.63[4.12], 0.22[1.94], and 0.10[2.60], respectively). Factors recorded each minute were task, tool, work area, respiratory protection and controls used, estimated cross draft, and whether anyone nearby was making dust. Factors important to exposure included tool used, work area configuration, controls employed, cross draft, and in some cases nearby dust. More protective respirators were employed as quartz concentration increased, although respiratory protection was found to be inadequate for 42% of exposures. Controls were employed for only 12% of samples. Exposures were reduced with three controls: box fan for surface grinding and floor sanding, and vacuum/shroud for surface grinding, with reductions of 57, 50, and 71%, respectively. Exposures were higher for sweeping compound, box fan for cleanup, ducted fan dilution, and wetted substrate. Construction masons and laborers are frequently overexposed to silica. The usual protection method, respirators, was not always adequate, and engineering control use was infrequent and often ineffective.

  12. Eu3+ DOPED SILICA FILM AS LUMINESCENT DOWN-SHIFTING LAYER FOR CRYSTALLINE Si SOLAR CELLS

    OpenAIRE

    ZUJUN CHENG; LIKUN PAN; FENFANG SU; MEILING CAO; ZHUO SUN

    2009-01-01

    Eu3+ doped silica films have been prepared by sol–gel method and employed as luminescent down-shifting layer on the front side of a crystalline Si solar cell to improve their conversion efficiency. Measurements under standard test conditions (AM1.5, 100 mW/cm2) show the conversion efficiency of Si solar cell with silica film containing Eu3+ is improved 9.5% maximally as compared to the Si solar cell with pure silica film. However, high Eu3+ concentration is not encouraged because concentratio...

  13. Differences in gene expression and cytokine production by crystalline vs. amorphous silica in human lung epithelial cells

    Directory of Open Access Journals (Sweden)

    Perkins Timothy N

    2012-02-01

    Full Text Available Abstract Background Exposure to respirable crystalline silica particles, as opposed to amorphous silica, is associated with lung inflammation, pulmonary fibrosis (silicosis, and potentially with lung cancer. We used Affymetrix/GeneSifter microarray analysis to determine whether gene expression profiles differed in a human bronchial epithelial cell line (BEAS 2B exposed to cristobalite vs. amorphous silica particles at non-toxic and equal surface areas (75 and 150 × 106μm2/cm2. Bio-Plex analysis was also used to determine profiles of secreted cytokines and chemokines in response to both particles. Finally, primary human bronchial epithelial cells (NHBE were used to comparatively assess silica particle-induced alterations in gene expression. Results Microarray analysis at 24 hours in BEAS 2B revealed 333 and 631 significant alterations in gene expression induced by cristobalite at low (75 and high (150 × 106μm2/cm2 amounts, respectively (p 6μm2/cm2 induced 108 significant gene changes. Bio-Plex analysis of 27 human cytokines and chemokines revealed 9 secreted mediators (p FOS, ATF3, IL6 and IL8 early and over time (2, 4, 8, and 24 h. Patterns of gene expression in NHBE cells were similar overall to BEAS 2B cells. At 75 × 106μm2/cm2, there were 339 significant alterations in gene expression induced by cristobalite and 42 by amorphous silica. Comparison of genes in response to cristobalite (75 × 106μm2/cm2 revealed 60 common, significant gene alterations in NHBE and BEAS 2B cells. Conclusions Cristobalite silica, as compared to synthetic amorphous silica particles at equal surface area concentrations, had comparable effects on the viability of human bronchial epithelial cells. However, effects on gene expression, as well as secretion of cytokines and chemokines, drastically differed, as the crystalline silica induced more intense responses. Our studies indicate that toxicological testing of particulates by surveying viability and

  14. How accurately and consistently do laboratories measure workplace concentrations of respirable crystalline silica?

    Science.gov (United States)

    Cox, Louis Anthony Tony

    2016-11-01

    Permissible exposure limits (PELs) for respirable crystalline silica (RCS) have recently been reduced from 0.10 to 0.05 mg/m(3). This raises an important question: do current laboratory practices and standards for assessing RCS concentrations permit reliable discrimination between workplaces that are in compliance and workplaces that are not? To find out, this paper examines recent laboratory performance in quantifying RCS amounts on filters sent to them to assess their proficiency. A key finding is that accredited laboratories do not reliably (e.g., with 95% confidence) estimate RCS quantities to within a factor of 2. Thus, laboratory findings indicating that RCS levels are above or below a PEL provide little confidence that this is true. The current accreditation standard only requires laboratories to achieve estimates within three standard deviations of the correct (reference) value at least two thirds of the time, rather than a more usual standard such as within 25% of the correct value at least 95% of the time. Laboratory practices may improve as the new PEL is implemented, but they are presently essentially powerless to discriminate among RCS levels over most of the range of values that have been tested, leaving employers and regulators without a reliable means to ascertain when workplace RCS levels are above or below the PEL.

  15. Tailoring crystallinity and configuration of silica nanotubes by electron irradiation

    Science.gov (United States)

    Taguchi, Tomitsugu; Yamaguchi, Kenji

    2015-05-01

    SiO2 nanotubes show potential in applications such as nanoscale electronic and optical devices, bioseparation, biocatalysis, and nanomedicine. As-grown SiO2 nanotubes in the previous studies always have an amorphous wall, and here we demonstrate the successful synthesis of single-crystal nanotubes for the first time by the heat treatment of SiC nanotubes at 1300 °C for 10 h under low-vacuum conditions. According to TEM observations, the single-crystal SiO2 was α-cristobalite. We also demonstrate that single-crystal SiO2 nanotubes can be transformed into amorphous SiO2 nanotubes by electron beam irradiation. Moreover, we synthesized a crystalline/amorphous SiO2 composite nanotube, in which crystalline and amorphous SiO2 coexisted in different localized regions. In addition, for biomedical applications such as drug delivery systems, controlling the configuration of the open end, the diameter, and capsulation of SiO2 nanotubes is crucial. We can also obturate, capsulate, and cut a SiO2 nanotube, as well as modify the inner diameter of the nanotube at a specific, nanometer-sized region using the focused electron beam irradiation technique.

  16. On the mechanical quality factors of cryogenic test masses from fused silica and crystalline quartz

    CERN Document Server

    Schroeter, Anja; Schnabel, Roman; Reid, Stuart; Martin, Iain; Rowan, Sheila; Schwarz, Christian; Koettig, Torsten; Neubert, Ralf; Thürk, Matthias; Vodel, Wolfgang; Tünnermann, Andreas; Danzmann, Karsten; Seidel, Paul

    2007-01-01

    Current interferometric gravitational wave detectors (IGWDs) are operated at room temperature with test masses made from fused silica. Fused silica shows very low absorption at the laser wavelength of 1064 nm. It is also well suited to realize low thermal noise floors in the detector signal band since it offers low mechanical loss, i. e. high quality factors (Q factors) at room temperature. However, for a further reduction of thermal noise, cooling the test masses to cryogenic temperatures may prove an interesting technique. Here we compare the results of Q factor measurements at cryogenic temperatures of acoustic eigenmodes of test masses from fused silica and its crystalline counterpart. Our results show that the mechanical loss of fused silica increases with lower temperature and reaches a maximum at 30 K for frequencies of slightly above 10 kHz. The losses of crystalline quartz generally show lower values and even fall below the room temperature values of fused silica below 10 K. Our results show that in ...

  17. Evaluation of Occupational Exposure and Biological Monitoring of Sand Washing Workers Exposed to Silica Dusts

    Directory of Open Access Journals (Sweden)

    Gholamreza Parsaseresht

    2017-01-01

    Full Text Available Background and Objectives:The health of sand washing workers could be threatened by the crystalline silica dust exposure. The aim of this study was the evaluation of occupational and biological monitoring with crystalline silica dusts in the sand washing workers. Materials and Methods: This was an analytical and cross-sectional study of 44 sand washing workers exposed to crystalline silica and also 63 municipality gardeners as a control group in the city of Dorood. Occupational exposure monitoring to respirable total dust and silica dust was performed according to the National Institute for Occupational Safety and Health (NIOSH methods 0600 and 7602-respectively. Biological monitoring of workers' was carried out according to the Karatas method for the analysis of Malondialdehyde in the blood serum of exposed and control subjects. The informed consents were taken for obtaining blood samples of workers, according to the Helsinki Declaration. Statistical analysis of data was done using SPSS version 16. The statistical test of Pearson, t-tests and linear regression was applied. Results: The occupational exposure of 54.55% was exceeded the occupational exposure limit of Iran at the level of 3 mg/m3. The mean exposure of sand miners and control group to respirable silica dust was evaluated at 0.219 ± 0.177 and 0.010 ± 0.002 as mg/m3respectively. Occupational exposure of all sand washing workers was higher than the occupational exposure limit of Iran at the level of 0.025 mg/m3.The concentration of serum Malondialdehyde (MDA exposed group and the control group were 36.64 ± 10.75 and 19.40 ± 4.68 as µM respectively. Conclusion: Due to the positive correlation between exposure of sand washing workers to silica dust sand serum MDA among exposed group(P-value<0.0001, r=0.881, periodical biological monitoring along with effective control measures of workers are recommended for the health promotion of these workers.

  18. Tailoring crystallinity and configuration of silica nanotubes by electron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Taguchi, Tomitsugu, E-mail: taguchi.tomitsugu@jaea.go.jp; Yamaguchi, Kenji

    2015-05-01

    Highlights: •Single-crystal SiO{sub 2} nanotubes were successfully synthesized for the first time. •The single-crystal SiO{sub 2} was α-crystobalite. •Desired area of single-crystal nanotube can be changed to amorphous by electron irradiation. •The configuration of nanotube can be controlled using the focused electron irradiation technique. -- Abstract: SiO{sub 2} nanotubes show potential in applications such as nanoscale electronic and optical devices, bioseparation, biocatalysis, and nanomedicine. As-grown SiO{sub 2} nanotubes in the previous studies always have an amorphous wall, and here we demonstrate the successful synthesis of single-crystal nanotubes for the first time by the heat treatment of SiC nanotubes at 1300 °C for 10 h under low-vacuum conditions. According to TEM observations, the single-crystal SiO{sub 2} was α-cristobalite. We also demonstrate that single-crystal SiO{sub 2} nanotubes can be transformed into amorphous SiO{sub 2} nanotubes by electron beam irradiation. Moreover, we synthesized a crystalline/amorphous SiO{sub 2} composite nanotube, in which crystalline and amorphous SiO{sub 2} coexisted in different localized regions. In addition, for biomedical applications such as drug delivery systems, controlling the configuration of the open end, the diameter, and capsulation of SiO{sub 2} nanotubes is crucial. We can also obturate, capsulate, and cut a SiO{sub 2} nanotube, as well as modify the inner diameter of the nanotube at a specific, nanometer-sized region using the focused electron beam irradiation technique.

  19. Laboratory evaluation to reduce respirable crystalline silica dust when cutting concrete roofing tiles using a masonry saw.

    Science.gov (United States)

    Carlo, Rebecca V; Sheehy, John; Feng, H Amy; Sieber, William K

    2010-04-01

    Respirable crystalline silica dust exposure in residential roofers is a recognized hazard resulting from cutting concrete roofing tiles. Roofers cutting tiles using masonry saws can be exposed to high concentrations of respirable dust. Silica exposures remain a serious threat for nearly two million U.S. construction workers. Although it is well established that respiratory diseases associated with exposure to silica dust are preventable, they continue to occur and cause disability or death. The effectiveness of both a commercially available local exhaust ventilation (LEV) system and a water suppression system in reducing silica dust was evaluated separately. The LEV system exhausted 0.24, 0.13, or 0.12 m(3)/sec of dust laden air, while the water suppression system supplied 0.13, 0.06, 0.03, or 0.02 L/sec of water to the saw blade. Using a randomized block design, implemented under laboratory conditions, the aforementioned conditions were evaluated independently on two types of concrete roofing tiles (s-shape and flat) using the same saw and blade. Each engineering control (LEV or water suppression) was replicated eight times, or four times for each type of tile. Analysis of variance was performed by comparing the mean airborne respirable dust concentrations generated during each run and engineering control treatment. The use of water controls and ventilation controls compared with the "no control" treatment resulted in a statistically significant (p capture velocity, additional weight of the saw with the LEV system, electricity connections, and cost of air handling unit.

  20. Evolution of Morphology and Crystallinity of Silica Minerals Under Hydrothermal Conditions

    Science.gov (United States)

    Isobe, H.

    2011-12-01

    Silica minerals are quite common mineral species in surface environment of the terrestrial planets. They are good indicator of terrestrial processes including hydrothermal alteration, diagenesis and soil formation. Hydrothermal quartz, metastable low temperature cristobalite and amorphous silica show characteristic morphology and crystallinity depending on their formation processes and kinetics under wide range of temperature, pressure, acidity and thermal history. In this study, silica minerals produced by acidic hydrothermal alteration related to volcanic activities and hydrothermal crystallization experiments from diatom sediment are examined with crystallographic analysis and morphologic observations. Low temperature form of cistobalite is a metastable phase and a common alteration product occured in highly acidic hydrothermal environment around fumaroles in geothermal / volcanic areas. XRD analysis revealed that the alteration degree of whole rock is represented by abundance of cristobalite. Detailed powder XRD analysis show that the primary diffraction peak of cristobalite composed with two or three phases with different d-spacing and FWHM by peak profile fitting analysis. Shorter d-spacing and narrower FWHM cristobalite crystallize from precursor materials with less-crystallized, longer d-spacing and wider FWHM cristobalite. Textures of hydrothermal cristobalite in altered rock shows remnant of porphylitic texture of the host rock, pyroxene-amphibole andesite. Diatom has amorphous silica shell and makes diatomite sediment. Diatomite found in less diagenetic Quarternary formation keeps amorphous silica diatom shells. Hydrothermal alteration experiments of amorphous silica diatomite sediment are carried out from 300 °C to 550 °C. Mineral composition of run products shows crystallization of cristobalite and quartz progress depending on temperature and run durations. Initial crystallization product, cristobalite grains occur as characteristic lepispheres and

  1. The structure of volcanic cristobalite in relation to its toxicity; relevance for the variable crystalline silica hazard

    Directory of Open Access Journals (Sweden)

    Horwell Claire J

    2012-11-01

    Full Text Available Abstract Background Respirable crystalline silica (RCS continues to pose a risk to human health worldwide. Its variable toxicity depends on inherent characteristics and external factors which influence surface chemistry. Significant population exposure to RCS occurs during volcanic eruptions, where ashfall may cover hundreds of square km and exposure may last years. Occupational exposure also occurs through mining of volcanic deposits. The primary source of RCS from volcanoes is through collapse and fragmentation of lava domes within which cristobalite is mass produced. After 30 years of research, it is still not clear if volcanic ash is a chronic respiratory health hazard. Toxicological assays have shown that cristobalite-rich ash is less toxic than expected. We investigate the reasons for this by determining the physicochemical/structural characteristics which may modify the pathogenicity of volcanic RCS. Four theories are considered: 1 the reactivity of particle surfaces is reduced due to co-substitutions of Al and Na for Si in the cristobalite structure; 2 particles consist of aggregates of cristobalite and other phases, restricting the surface area of cristobalite available for reactions in the lung; 3 the cristobalite surface is occluded by an annealed rim; 4 dissolution of other volcanic particles affects the surfaces of RCS in the lung. Methods The composition of volcanic cristobalite crystals was quantified by electron microprobe and differences in composition assessed by Welch’s two sample t-test. Sections of dome-rock and ash particles were imaged by scanning and transmission electron microscopy, and elemental compositions of rims determined by energy dispersive X-ray spectroscopy. Results Volcanic cristobalite contains up to 4 wt. % combined Al2O3 and Na2O. Most cristobalite-bearing ash particles contain adhered materials such as feldspar and glass. No annealed rims were observed. Conclusions The composition of volcanic

  2. Particle size distribution and particle size-related crystalline silica content in granite quarry dust.

    Science.gov (United States)

    Sirianni, Greg; Hosgood, Howard Dean; Slade, Martin D; Borak, Jonathan

    2008-05-01

    Previous studies indicate that the relationship between empirically derived particle counts, particle mass determinations, and particle size-related silica content are not constant within mines or across mine work tasks. To better understand the variability of particle size distributions and variations in silica content by particle size in a granite quarry, exposure surveys were conducted with side-by-side arrays of four closed face cassettes, four cyclones, four personal environmental monitors, and a real-time particle counter. In general, the proportion of silica increased as collected particulate size increased, but samples varied in an inconstant way. Significant differences in particle size distributions were seen depending on the extent of ventilation and the nature and activity of work performed. Such variability raises concerns about the adequacy of silica exposure assessments based on only limited numbers of samples or short-term samples.

  3. Excessive exposure to silica in the US construction industry.

    Science.gov (United States)

    Rappaport, S M; Goldberg, Mark; Susi, Pam; Herrick, Robert F

    2003-03-01

    Exposures to respirable dust and silica were investigated among 36 construction sites in the USA. Personal measurements (n = 151) were analyzed from 80 workers in four trades, namely bricklayers, painters (while abrasive blasting), operating engineers and laborers. Painters had the highest exposures (median values for respirable dust and silica: 13.5 and 1.28 mg/m(3), respectively), followed by laborers (2.46 and 0.350 mg/m(3)), bricklayers (2.13 and 3.20 mg/m(3)) and operating engineers (0.720 and 0.075 mg/m(3)). Mixed models were fitted to the log-transformed air levels to estimate the means and within- and between-worker variance components of the distributions in each trade. We refer to the likelihood that a typical worker from a given trade would be exposed, on average, above the occupational exposure limit (OEL) as the probability of overexposure. Given US OELs of 0.05 mg/m(3) for respirable silica and 3 mg/m(3) for respirable dust, we estimated probabilities of overexposure as between 64.5 and 100% for silica and between 8.2 and 89.2% for dust; in no instance could it be inferred with certainty that this probability was construction industry. While engineering and administrative interventions are needed to reduce overall air levels, the heterogeneous exposures among members of each trade suggest that controls should focus, in part, upon the individual sites, activities and equipment involved. The effects of current controls and workplace characteristics upon silica exposures were investigated among operating engineers and laborers. Silica exposures were significantly reduced by wet dust suppression (approximately 3-fold for laborers) and use of ventilated cabs (approximately 6-fold for operating engineers) and were significantly increased indoors (about 4-fold for laborers). It is concluded that urgent action is required to reduce silica exposures in the US construction industry.

  4. Levels of crystalline silica dust in dental laboratorium of Dental Health Technology Study Program of Vocational Faculty, Universitas Airlangga

    Directory of Open Access Journals (Sweden)

    Eny Inayati

    2015-12-01

    Full Text Available Background: Silicosis is an occupational lung disease caused by inhaling particles of crystalline silica in a long time. The disease then results in inflammation and defects in lung tissue. Prosthesis construction is usually conducted in dental laboratory using a lot of materials containing crystalline silica, such as gypsum, ceramics, planting material, sandblast and others. Purpose: This research aims to determine levels of crystalline silica dust in the dental laboratory of Dental Health Technology Diploma Study Program, Vocational Faculty, Universitas Airlangga. Method: Three measurement points was determined, namely point 1, point 2 and point 3 in each dental laboratory space (I and II. Suctioning dust was performed at those points using Low Volume Dust Sampler (LVDS. Samples taken were divided into two groups, namely X and Y. Taking dust samples were carried out for 30 minutes. Elements of crystalline silica contained in the dust were quantitatively measured using XR Defractometry tool, while size and morphology of silica were measured using SEM EDX tool. Data obtained were statistically analyzed by paired t test. Result: The results showed significant differences in the levels of the total dust measured and crystalline silica in the form of quartz and cristobalite among those two dental laboratory spaces. Conclusion: It can be concluded that the levels of the total dust and silica quartz dust in the dental laboratory spaces I and II were greater than the Threshold Limit Value (TLV determined.

  5. A Significant Amount of Crystalline Silica in Returned Cometary Samples: Bridging the Gap between Astrophysical and Meteoritical Observations

    Science.gov (United States)

    Roskosz, Mathieu; Leroux, Hugues

    2015-03-01

    Crystalline silica (SiO2) is recurrently identified at the percent level in the infrared spectra of protoplanetary disks. By contrast, reports of crystalline silica in primitive meteorites are very unusual. This dichotomy illustrates the typical gap existing between astrophysical observations and meteoritical records of the first solids formed around young stars. The cometary samples returned by the Stardust mission in 2006 offer an opportunity to have a closer look at a silicate dust that experienced a very limited reprocessing since the accretion of the dust. Here, we provide the first extended study of silica materials in a large range of Stardust samples. We show that cristobalite is the dominant form. It was detected in 5 out of 25 samples. Crystalline silica is thus a common minor phase in Stardust samples. Furthermore, olivine is generally associated with this cristobalite, which put constraints on possible formation mechanisms. A low-temperature subsolidus solid-solid transformation of an amorphous precursor is most likely. This crystallization route favors the formation of olivine (at the expense of pyroxenes), and crystalline silica is the natural byproduct of this transformation. Conversely, direct condensation and partial melting are not expected to produce the observed mineral assemblages. Silica is preserved in cometary materials because they were less affected by thermal and aqueous alterations than their chondritic counterparts. The common occurrence of crystalline silica therefore makes the cometary material an important bridge between the IR-based mineralogy of distant protoplanetary disks and the mineralogy of the early solar system.

  6. A SIGNIFICANT AMOUNT OF CRYSTALLINE SILICA IN RETURNED COMETARY SAMPLES: BRIDGING THE GAP BETWEEN ASTROPHYSICAL AND METEORITICAL OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Roskosz, Mathieu; Leroux, Hugues [Unité Matériaux et Transformations, Université Lille 1, CNRS, UMR 8207, F-59655 Villeneuve d’Ascq (France)

    2015-03-01

    Crystalline silica (SiO{sub 2}) is recurrently identified at the percent level in the infrared spectra of protoplanetary disks. By contrast, reports of crystalline silica in primitive meteorites are very unusual. This dichotomy illustrates the typical gap existing between astrophysical observations and meteoritical records of the first solids formed around young stars. The cometary samples returned by the Stardust mission in 2006 offer an opportunity to have a closer look at a silicate dust that experienced a very limited reprocessing since the accretion of the dust. Here, we provide the first extended study of silica materials in a large range of Stardust samples. We show that cristobalite is the dominant form. It was detected in 5 out of 25 samples. Crystalline silica is thus a common minor phase in Stardust samples. Furthermore, olivine is generally associated with this cristobalite, which put constraints on possible formation mechanisms. A low-temperature subsolidus solid–solid transformation of an amorphous precursor is most likely. This crystallization route favors the formation of olivine (at the expense of pyroxenes), and crystalline silica is the natural byproduct of this transformation. Conversely, direct condensation and partial melting are not expected to produce the observed mineral assemblages. Silica is preserved in cometary materials because they were less affected by thermal and aqueous alterations than their chondritic counterparts. The common occurrence of crystalline silica therefore makes the cometary material an important bridge between the IR-based mineralogy of distant protoplanetary disks and the mineralogy of the early solar system.

  7. Evaluation of occupational exposure to free silica in Alberta foundries.

    Science.gov (United States)

    Ayalp, A; Myroniuk, D

    1982-11-01

    The Occupational Hygiene Branch of Alberta Workers' Health, Safety and Compensation conducted a comprehensive study of the foundry industry in Alberta. The surveys assessed both the degree of health hazards present and the effectiveness of existing control systems for airborne contaminants. All nine of Alberta's ferrous foundries were surveyed in the course of the project. The foundries varied from those which were small with limited mechanization to those which were large and highly automated. The concentrations of free silica in the work environment are correlated to the different attempts to control silica using substitution and various ventilation systems. The particular foundry processes evaluated for airborne free silica were sand preparation, shakeout, dry sand transport and sand molding. Workers' exposure to free airborne silica was evaluated by personal and area samples. The free silica content of the samples was determined by infra-red spectrophotometry. The results indicated most control systems were inadequate. Effective control methods are described to reduce the health hazard.

  8. Validation of the analysis of respirable crystalline silica (quartz) in foams used with CIP 10-R samplers.

    Science.gov (United States)

    Eypert-Blaison, Céline; Moulut, Jean-Claude; Lecaque, Thierry; Marc, Florian; Kauffer, Edmond

    2011-05-01

    Sampling the respirable fraction to measure exposure to crystalline silica is most often carried out using cyclones. However, low flow rates (quartz sampled on foams, known amounts of quartz associated with a matrix have been injected into foams. The results obtained show that the proposed protocol, with prior acid attack and ashing of the foams, satisfies the recommendations of EN 482 Standard [CEN. (2006) Workplace atmospheres-general requirements for the performance of procedures for the measurements of chemical agents. Brussels, Belgium: EN 482 Comité Européen de normalization (CEN).], namely an expanded uncertainty of quartz weights between 0.1 and 0.5 times the 8-h exposure limit value and quartz weights between 0.5 and 2 times the 8-h exposure limit value, assuming an exposure limit value equal to 0.1 mg m(-3). Results obtained show that the 101 reflection line allows a quartz quantity of the order of 25 μg to be satisfactorily measured, which corresponds to a 10th of the exposure limit value, assuming an exposure limit value of 0.05 mg m(-3). In this case, the 100 and 112 reflection lines with expanded uncertainties of ~50% would also probably lead to satisfactory quantification. Particular recommendations are also proposed for the preparation of calibration curves to improve the method.

  9. Respirable Crystalline Silica (RCS) emissions from industrial plants - Results from measurement programmes in Germany

    Science.gov (United States)

    Ehrlich, C.; Noll, G.; Wusterhausen, E.; Kalkoff, W.-D.; Remus, R.; Lehmann, C.

    2013-04-01

    Numerous research articles dealing with Respirable Crystalline Silica (RCS) in occupational health because epidemiological studies reveal an association between RCS-dust and the development of silicosis as well as an increased probability of developing lung cancer. Research activities about RCS in ambient air are known from US-measurements. However there is a lack of knowledge regarding RCS-emissions in several industrial sectors. Industrial sources of crystalline silica include construction, foundries, glass manufacturing, abrasive blasting or any industrial or commercial use of silica sand, and mining and rock crushing operations. This paper describes a RCS-emission measurement method for stack gases and report results from the German RCS-emission measurement programmes which were used to identify installations and types of industries with the highest concentration levels of RCS in stack gases. A two-stage cascade impactor was used for the measurements which separate particles into the following size fractions: >10 μm, 10-4 μm und plants are located in different German states such as Bavaria, North Rhine Westphalia, Baden-Wuerttemberg, Rhineland-Palatinate and Saxony-Anhalt. The results of the measurements show that most of the investigated plants can achieve compliance with the newly developed German emission limit value (ELV) of 1 mg m-3. The ELV is expressed as the concentration of RCS in stack emissions. According to the German emission minimising principle and the precautionary principle it is assumed that by complying with the RCS-ELV there is no ambient air health risk for people living these plants. In the case of increased total dust concentration in the stack gas (more than 20 mg m-3) combined with increased percentage of crystalline silica in PM4 dust, a violation of the above mentioned ELV is more likely. This applies mostly to installations in the silica sand processing industry. To comply with the ELV of 1 mg m-3, efficient emission control

  10. Bench-scale synthesis of zeolite A from subbituminous coal ashes with high crystalline silica content

    Energy Technology Data Exchange (ETDEWEB)

    Chareonpanich, M.; Jullaphan, O.; Tang, C. [Kasetsart University, Bangkok (Thailand). Dept. of Chemical Engineering

    2011-01-15

    In this present work, fly ash and bottom ash with high crystalline silica content were obtained from the coal-fired boilers within the paper industries in Thailand. These coal ashes were used as the basic raw materials for synthetic zeolite production. The crystal type and crystallinity, specific surface area and pore size, and textural properties of zeolite products were characterized by using X-ray diffraction spectroscopy (XRD), N{sub 2} sorption analysis, and Scanning Electron Microscopy (SEM), respectively. It was found that sodalite octahydrate was selectively formed via the direct conventional (one-step) synthesis, whereas through a two-step, sodium silicate preparation and consecutive zeolite A synthesis process, 94 and 72 wt.% zeolite A products could be produced from the fly ash and bottom ash, respectively. The cation-exchange capacity (CEC) of fly ash and bottom ash-derived zeolite A products were closely similar to that of the commercial grade zeolite A.

  11. Designing, construction, assessment, and efficiency of local exhaust ventilation in controlling crystalline silica dust and particles, and formaldehyde in a foundry industry plant.

    Science.gov (United States)

    Morteza, Mortezavi Mehrizi; Hossein, Kakooi; Amirhossein, Matin; Naser, Hasheminegad; Gholamhossein, Halvani; Hossein, Fallah

    2013-01-01

    The purpose of the present study was to design and assess the efficiency of a local exhaust ventilation system used in a foundry operation to control inhalable dust and particles, microcrystal particles, and noxious gases and vapours affecting workers during the foundry process. It was designed based on recommendations from the American Conference of Governmental Industrial Hygiene. After designing a local exhaust ventilation system (LEV), we prepared and submitted the implementation plan to the manufacturer. High concentrations of crystalline silica dust and formaldehyde, which are common toxic air pollutants in foundries, were ultimately measured as an indicator for studying the efficiency of this system in controlling inhalable dust and particles as well as other air pollutants. The level of occupational exposure to silica and formaldehyde as major air pollutants was assessed in two modes: first, when the LEV was on, and second, when it was off. Air samples from the exposure area were obtained using a personal sampling pump and analysed using the No. 7601 method for crystal silica and the No. 2541 method for formaldehyde of the National Institute for Occupational Safety and Health (NIOSH). Silica and formaldehyde concentrations were determined by visible absorption spectrophotometry and gas chromatography. The results showed that local exhaust ventilation was successful in preserving the crystal silica particles in the work environment at a level below the NIOSH maximum allowed concentration (0.05 mg m-3). In contrast, formaldehyde exceeded the NIOSH limit (1 ppm or 1.228 mg m-3).

  12. [Exposure to silica dust in the Polish construction industry].

    Science.gov (United States)

    Szadkowska-Stańczyk, Irena; Stroszejn-Mrowca, Grazyna; Mikołajczyk, Urszula; Maciejewska, Aleksandra

    2006-01-01

    In the construction industry, free crystalline silica (FCS), mostly in the form of quartz, is in a very common use. Construction, especially repair and demolition works, are associated with emission of considerable amounts of FCS-containing dusts. Studies concerning the work environment, carried out recently in other countries, indicate that exposure to quartz frequently exceeds hygiene standards, i.e. safety limits for workers' health. The aim of this study was to assess dust exposure of workers employed at selected workposts in the construction industry in Poland. The Polish study was performed in a group of workers employed in large and small enterprises and involved in establishing new constructions and demolishing old buildings. The group comprised 43 workers, employed at 9 workposts, who underwent 107 measurements of dust concentrations, of which 78 measurements were included in the analysis. At each workpost, concentrations of inhalable and respirable dusts were measured with the filtration and gravimetric method. Individual dust dosimeters were used to collect air samples and infrared spectrometry to determine concentrations of FCS dusts in samples of inhalable and respirable dusts. An identification analysis of dust samples was performed with use of X-ray diffraction. The results of the study show that geometric means of inhalable dust concentrations fell within a wide range from 2.1 (concrete mixer operator, plasterer) to 66.0 mg/m3 (laborer engaged in hand demolition), and those of respirable dust at the same workposts ranged from 0.4 to 16.2 mg/m3, respectively. Quartz was present in the majority of construction materials applied, and its concentration in inhalable dusts ranged from 7 to 13 mg/m3. It was found that dust concentrations exceeded hygiene standards at most of the workposts. Particularly high concentrations were observed at the workposts of surface abrasive grinders-coat finishers and workers engaged in drilling and hammering wholes. In

  13. Effect of Alkali Ions on the Amorphous to Crystalline Phase Transition of Silica

    Science.gov (United States)

    Venezia, A. M.; La Parola, V.; Longo, A.; Martorana, A.

    2001-11-01

    The effect of the addition of alkali ions to commercial amorphous silica, generally used as support for heterogeneous catalysts, has been investigated from the point of view of morphological and structural changes. Samples of alkali-doped silica were prepared by impregnation and subsequent calcination at various temperatures. The structural effect of Li, Na, K, and Cs was determined by use of techniques such as wide-angle (WAXS) and small-angle X-ray scattering (SAXS). The WAXS diffractograms, analyzed with the Rietveld method using the GSAS program, allowed qualitative and quantitative identification of the fraction of the different silica polymorphs like quartz, tridymite, and cristobalite. SAXS measurements, using the classical method based on Porod's law, yielded the total surface area of the systems. The calculated areas were compared with the surface areas determined by the nitrogen adsorption technique using the analytical method of Brunauer-Emmett-Teller. The results are explained in terms of sizes of the alkali ions and cell volume of the different crystalline phases.

  14. 78 FR 56273 - Occupational Exposure to Respirable Crystalline Silica

    Science.gov (United States)

    2013-09-12

    ... basis for setting OSHA health standards.\\1\\ \\1\\ Am. Textile Mfrs. Inst., Inc. v. Nat'l Cotton Council of... controls would be at odds with this framework for evaluating the technological feasibility of a PEL...

  15. Respirable crystalline silica: Analysis methodologies; Silice cristalina respirable: Metodologias de analisis

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Tena, M. P.; Zumaquero, E.; Ibanez, M. J.; Machi, C.; Escric, A.

    2012-07-01

    This paper describes different analysis methodologies in occupational environments and raw materials. A review is presented of the existing methodologies, the approximations made, some of the constraints involved, as well as the best measurement options for the different raw materials. In addition, the different factors that might affect the precision and accuracy of the results are examined. With regard to the methodologies used for the quantitative analysis of any of the polymorph s, particularly of quartz, the study centres particularly on the analytical X-ray diffraction method. Simplified methods of calculation and experimental separation are evaluated for the estimation of this fraction in the raw materials, such as separation methods by centrifugation, sedimentation, and dust generation in controlled environments. In addition, a review is presented of the methodologies used for the collection of respirable crystalline silica in environmental dust. (Author)

  16. Gasification slag rheology and crystalline phase formation in titanium-calcium-alumina-silica-rich glass

    Energy Technology Data Exchange (ETDEWEB)

    Brooker, D.D. [Texaco, Inc., Beacon, NY (United States); Oh, M.S. [Hongik Univ., Seoul (Korea, Republic of)

    1996-10-01

    The Texaco Gasification Process employs a high temperature and pressure slagging gasifier, in which the viscosity of the slag plays a key role in determining operating conditions. The empirical models available in the literature as well as laboratory testing have concentrated on low titanium feeds. During the gasification of waste material, titanium oxide will become an important element in controlling the ash and slag behavior. Slag viscosity was measured at temperatures in the range of 1150-1500{degrees}C under reducing atmosphere with 0-30% titanium in combination with calcium-alumina-silica rich feeds to gain a better understanding of the slag theology. The slag viscosities with most titanium-rich slags showed the behavior of a crystalline slag with T{sub cv} of 1250{degrees}C. Crystalline phase analyses of the slag samples revealed that titanium oxide crystal will nucleate, but the glass phase is dominated by calcium-titanium-silicate and calcium-alumina-silicate glasses which have low melting points.

  17. Silica dust exposure: Effect of filter size to compliance determination

    Science.gov (United States)

    Amran, Suhaily; Latif, Mohd Talib; Khan, Md Firoz; Leman, Abdul Mutalib; Goh, Eric; Jaafar, Shoffian Amin

    2016-11-01

    Monitoring of respirable dust was performed using a set of integrated sampling system consisting of sampling pump attached with filter media and separating device such as cyclone or special cassette. Based on selected method, filter sizes are either 25 mm or 37 mm poly vinyl chloride (PVC) filter. The aim of this study was to compare performance of two types of filter during personal respirable dust sampling for silica dust under field condition. The comparison strategy focused on the final compliance judgment based on both dataset. Eight hour parallel sampling of personal respirable dust exposure was performed among 30 crusher operators at six quarries. Each crusher operator was attached with parallel set of integrated sampling train containing either 25 mm or 37 mm PVC filter. Each set consisted of standard flow SKC sampler, attached with SKC GS3 cyclone and 2 pieces cassette loaded with 5.0 µm of PVC filter. Samples were analyzed by gravimetric technique. Personal respirable dust exposure between the two types of filters indicated significant positive correlation (p arithmetic mean(AM) and geometric mean(GM). In overall we concluded that personal respirable dust exposure either based on 25mm or 37mm PVC filter will give similar compliance determination. Both filters are reliable to be used in respirable dust monitoring for silica dust related exposure.

  18. Electrolyte-promoted demineralization of biogenic, vitreous, and crystalline silica: A density functional investigation

    Science.gov (United States)

    Dove, P. M.; Wallace, A. F.; Gibbs, G. V.

    2007-12-01

    The dissolution of amorphous and crystalline varieties of SiO2 is an integral part of the global biogeochemical cycle of silicon. Nanoparticulate biogenic silica produced by marine phytoplankton and terrestrial plants are of particular interest because their enhanced reactivity and abundance make them important sources and sinks of dissolved silicon in natural environments. Recent experimental results on (100) surfaces of quartz show that the dominant dissolution mechanism in simple H2O solutions is by retreat of Q2 groups along step edges. In the presence of electrolytes, rates are accelerated by up to 100X in the presence by a crossover in the dominant dissolution mechanism to nucleation of vacancy islands at Q3 terminated species (Dove et al., PNAS, 2005). While the control of surface coordination in reactivity is clear, the molecular pathway by which electrolytes induce dissolution by a nucleated process remains poorly understood. The results of previous ab initio investigations of Si-O bond hydrolysis by water have demonstrated that the reaction proceeds through the dissociative adsorption of H2O at the silica surface, resulting in the formation of a pentacoordinated Si transition state, followed by the transfer of one of the water bound hydrogen atoms to a bridging oxygen in the SiO2 bonded network, and breakage of the Si-O bond. Assuming a similar reaction path, the specific effects of hydrated group II metal cations (Mg2+, Ca2+, Sr2+, Ba2+) on the energetics of Si-O bond hydrolysis have been investigated with density functional methods (B3LYP) and a relatively large neutral silica cluster (H8Si6O16). Reactant, product, and transition states for Q3 to Q2 hydrolysis in the presence and absence of the afore-mentioned cations have been determined with all electron (6-31G(d)) and effective core potential (SDDALL) Gaussian basis sets. The free energy of activation for Q3 to Q2 Si-O bond hydrolysis was determined to be approximately 5 kJ/mol lower for Ca2+ than Mg

  19. Crystalline silica dust and respirable particulate matter during indoor concrete grinding - wet grinding and ventilated grinding compared with uncontrolled conventional grinding.

    Science.gov (United States)

    Akbar-Khanzadeh, Farhang; Milz, Sheryl; Ames, April; Susi, Pamela P; Bisesi, Michael; Khuder, Sadik A; Akbar-Khanzadeh, Mahboubeh

    2007-10-01

    The effectiveness of wet grinding (wet dust reduction method) and ventilated grinding (local exhaust ventilation method, LEV) in reducing the levels of respirable crystalline silica dust (quartz) and respirable suspended particulate matter (RSP) were compared with that of uncontrolled (no dust reduction method) conventional grinding. A field laboratory was set up to simulate concrete surface grinding using hand-held angle grinders in an enclosed workplace. A total of 34 personal samples (16 pairs side-by-side and 2 singles) and 5 background air samples were collected during 18 concrete grinding sessions ranging from 15-93 min. General ventilation had no statistically significant effect on operator's exposure to dust. Overall, the arithmetic mean concentrations of respirable crystalline silica dust and RSP in personal air samples during: (i) five sessions of uncontrolled conventional grinding were respectively 61.7 and 611 mg/m(3) (ii) seven sessions of wet grinding were 0.896 and 11.9 mg/m(3) and (iii) six sessions of LEV grinding were 0.155 and 1.99 mg/m(3). Uncontrolled conventional grinding generated relatively high levels of respirable silica dust and proportionally high levels of RSP. Wet grinding was effective in reducing the geometric mean concentrations of respirable silica dust 98.2% and RSP 97.6%. LEV grinding was even more effective and reduced the geometric mean concentrations of respirable silica dust 99.7% and RSP 99.6%. Nevertheless, the average level of respirable silica dust (i) during wet grinding was 0.959 mg/m(3) (38 times the American Conference of Governmental Industrial Hygienists [ACGIH] threshold limit value [TLV] of 0.025 mg/m(3)) and (ii) during LEV grinding was 0.155 mg/m(3) (6 times the ACGIH TLV). Further studies are needed to examine the effectiveness of a greater variety of models, types, and sizes of grinders on different types of cement in different positions and also to test the simulated field lab experimentation in the field.

  20. Differentiating between long and short range disorder in infra-red spectra: on the meaning of "crystallinity" in silica.

    Science.gov (United States)

    Asscher, Yotam; Dal Sasso, Gregorio; Nodari, Luca; Angelini, Ivana; Boffa Ballaran, Tiziana; Artioli, Gilberto

    2017-08-16

    Local atomic disorder and crystallinity are structural properties that influence greatly the resulting chemical and mechanical properties of inorganic solids, and are used as indicators for different pathways of material formation. Here, these structural properties are assessed in the crystals of quartz based on particle-size-related scattering processes in transmission infra-red spectroscopy. Independent determinations of particle size distributions in the range 2-100 μm of a single crystal of quartz and defective quartz with highly anisotropic micro-crystallites show that particle sizes below the employed wavelength (approx 10 μm) exhibit asymmetric narrowing of absorption peak widths, due to scattering processes that depend on the intra-particle structural defects and long range crystallinity. In particular, we observe that the 1079 cm(-1) peak could be used to assess crystallinity, because it shows an asymmetric peak shape shift toward a higher wavelength, depending on the crystallite size. We observe that the 694 cm(-1) peak could be used to assess local atomic disorder as it does not show scattering and peak shape changes when absorption effects dominate, below 2 μm. We propose coupling particle size assessments with infra-red peak shape analysis as a method to characterize crystallinity and short range order for studying recrystallization in natural silica, as well as defectivity in many different types of silicas used for industrial and technological applications.

  1. Dental composite resins containing silica-fused ceramic single-crystalline whiskers with various filler levels.

    Science.gov (United States)

    Xu, H H

    1999-07-01

    Currently available direct-filling composite resins are susceptible to fracture and hence are not recommended for use in large stress-bearing posterior restorations involving cusps. The glass fillers in composites provide only limited reinforcement because of the brittleness and low strength of glass. The aim of the present study was to use ceramic single-crystalline whiskers as fillers to reinforce composites, and to investigate the effect of whisker filler level on composite properties. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whiskers, thereby improving retention in the matrix. The composite flexural strength, elastic modulus, hardness, and degree of polymerization conversion were measured as a function of whisker filler mass fraction, which ranged from 0% to 70%. Selected composites were polished simulating clinical procedures, and the surface roughness was measured with profilometry. The whisker composite with a filler mass fraction of 55% had a flexural strength (mean +/- SD; n = 6) of 196+/-10 MPa, significantly higher than 83+/-14 MPa of a microfill and 120+/-16 MPa of a hybrid composite control (family confidence coefficient = 0.95; Tukey's multiple comparison). The composite modulus and hardness increased monotonically with filler level. The flexural strength first increased, then plateaued with increasing filler level. The degree of conversion decreased with increasing filler level. The whisker composite had a polished surface roughness similar to that of a conventional hybrid composite (p>0.1; Student's t). To conclude, ceramic whisker reinforcement can significantly improve the mechanical properties of composite resins; the whisker filler level plays a key role in determining composite properties; and the reinforcement mechanisms appear to be crack pinning by whiskers and friction from whisker pullout resisting crack propagation.

  2. Immunomodulation and oxidative stress in denim sandblasting workers: changes caused by silica exposure.

    Science.gov (United States)

    Palabiyik, Saziye Sezin; Girgin, Gözde; Tutkun, Engin; Yilmaz, Omer Hinc; Baydar, Terken

    2013-09-01

    Workers in denim sandblasting are at a high risk of developing silicosis, an occupational lung disease caused by inhaling crystalline silica dust. The development and progress of silicosis is associated with the activation of the immune system and oxidative stress. In the former, interferon-gamma induces both neopterin release and the enzyme indoleamine [2, 3]-dioxygenase (IDO) in various cells. The determination of the kynurenine-to-tryptophan ratio and neopterin concentration has proven to be an efficient method to monitor the activation status of IDO and cellular immunity. The present study aimed to investigate whether occupational silica exposure leads to any alterations in neopterin levels, tryptophan degradation, and activities of superoxide dismutase (SOD) and catalase (CAT), agents in the antioxidant defense system. Fifty-five male denim sandblasting workers and twenty-two healthy men as controls were included. Mean neopterin and kynurenine levels, kynurenine-to-tryptophan ratio, and SOD activity were higher in subjects with silicosis compared to non-exposed controls (all, pindicator of cellular immune response.

  3. [Silica-associated systemic sclerosis occurring after an occupational exposure to arc welding].

    Science.gov (United States)

    Alaya, Zeineb; Kalboussi, Houda; Osman, Walid; Naouar, Nader; Zeglaoui, Héla; Bouajina, Elyès

    2016-01-01

    Crystalline silica-associated systemic sclerosis can occur in people operating arc welding. Diffuse scleroderma was diagnosed in a 57-year old plumber-welder suffering from inflammatory polyarthralgias, Raynaud's phenomenon, sclerodactyly, diffuse cutaneous scleroderma, telangiectasias, esophageal damage, pulmonary arterial hypertension and pulmonary fibrosis associated with the presence of anti-nucleosome antibodies. During his professional activity the patient was frequently exposed to high atmospheric concentrations of crystalline silica generated by arc-welding. The diagnosis of Erasmus syndrome associated with systemic sclerosis and pulmonary silicosis was retained. A report of work-related illness (table 17 in Tunisia) was made.

  4. Centrifugation-assisted Assembly of Colloidal Silica into Crack-Free and Transferrable Films with Tunable Crystalline Structures.

    Science.gov (United States)

    Fan, Wen; Chen, Min; Yang, Shu; Wu, Limin

    2015-07-10

    Self-assembly of colloidal particles into colloidal films has many actual and potential applications. While various strategies have been developed to direct the assembly of colloidal particles, fabrication of crack-free and transferrable colloidal film with controllable crystal structures still remains a major challenge. Here we show a centrifugation-assisted assembly of colloidal silica spheres into free-standing colloidal film by using the liquid/liquid interfaces of three immiscible phases. Through independent control of centrifugal force and interparticle electrostatic repulsion, polycrystalline, single-crystalline and quasi-amorphous structures can be readily obtained. More importantly, by dehydration of silica particles during centrifugation, the spontaneous formation of capillary water bridges between particles enables the binding and pre-shrinkage of the assembled array at the fluid interface. Thus the assembled colloidal films are not only crack-free, but also robust and flexible enough to be easily transferred on various planar and curved substrates.

  5. Silica Exposure and Serum Angiotensin Converting Enzyme Activity

    Directory of Open Access Journals (Sweden)

    YK Sharma

    2010-01-01

    Full Text Available Background: Silicosis is known in industrial workers for centuries. Till recently, the mainstay of its diagnosis and progress was clinical examination of the respiratory system, pulmonary function test and chest radiography. Several biomarkers such as serum angiotensin converting enzyme (ACE activity have been examined to determine the extent of silicosis. Objective: To elucidate the effect of age, gender, duration of exposure to silica dust, smoking habit, and pulmonary function status on the serum ACE activity among quartz stone workers without disease.Methods: A cross-sectional study was carried out on 134 (111 men and 14 women workers of quartz stone crushing units were studied. Standard diagnostic criteria were used for diagnosing silicosis and tuberculosis. Pulmonary functions of the participants were also assessed.Results: The mean±SD age for participants was 26.1±6.3 years (26.6±6.3 for men and 21.9±4.3 for women. The mean±SD duration of exposure was 1.1±1.9 years. In the present study, only one case of silicosis and eight cases of tuberculosis were found. The mean±SD serum ACE levels for those with and without respiratory disease were 68.44±11.61, and 66.9±14.4 IU/L, respectively (p>0.05.Conclusion: We could not observe any association between serum ACE activity and age, gender, duration of exposure, smoking habits and pulmonary function status. However, elevated levels of serum ACE was found in a solitary case of silicosis.

  6. Occupational exposure to silica and lung cancer risk in the Netherlands

    NARCIS (Netherlands)

    Preller, L.; Bosch, L.M.C. van den; Brandt, P.A. van den; Kauppinen, T.; Goldbohm, R.A.

    2010-01-01

    Objectives: The lung cancer carcinogenicity of crystalline silica dust remains the subject of discussion. Epidemiological evidence is based on occupational cohort studies and population-based case-control studies. The aim of this study was to assess associations between male lung cancer risk and sil

  7. Worker exposure to silica dust in South African non-mining industries in Gauteng: An exploratory study

    CSIR Research Space (South Africa)

    Khoza, NN

    2012-06-01

    Full Text Available /m?, respectively. Of the occupations measured, 53% were exposed to silica dust at above the RSA-OEL. 18 The clay worker and dispatch clerk occupations were exposed to silica dust where mean, median and maximum levels exceeded the RSA-OEL of silica dust. Only 2... of silica dust exposure, as this is the one of the major industries reported in literature. 4.5 Ceramics/potteries Handling clay or sand that contains silica is the main source of worker exposure to respirable silica in the ceramics/pottery working...

  8. Autophagy deficiency in macrophages enhances NLRP3 inflammasome activity and chronic lung disease following silica exposure.

    Science.gov (United States)

    Jessop, Forrest; Hamilton, Raymond F; Rhoderick, Joseph F; Shaw, Pamela K; Holian, Andrij

    2016-10-15

    Autophagy is an important metabolic mechanism that can promote cellular survival following injury. The specific contribution of autophagy to silica-induced inflammation and disease is not known. The objective of these studies was to determine the effects of silica exposure on the autophagic pathway in macrophages, as well as the general contribution of autophagy in macrophages to inflammation and disease. Silica exposure enhanced autophagic activity in vitro in Bone Marrow derived Macrophages and in vivo in Alveolar Macrophages isolated from silica-exposed mice. Impairment of autophagy in myeloid cells in vivo using Atg5(fl/fl)LysM-Cre(+) mice resulted in enhanced cytotoxicity and inflammation after silica exposure compared to littermate controls, including elevated IL-18 and the alarmin HMGB1 in the whole lavage fluid. Autophagy deficiency caused some spontaneous inflammation and disease. Greater silica-induced acute inflammation in Atg5(fl/fl)LysM-Cre(+) mice correlated with increased fibrosis and chronic lung disease. These studies demonstrate a critical role for autophagy in suppressing silica-induced cytotoxicity and inflammation in disease development. Furthermore, this data highlights the importance of basal autophagy in macrophages and other myeloid cells in maintaining lung homeostasis.

  9. Silica exposure and lung cancer in ceramic workers: a case-control study.

    Science.gov (United States)

    Meijers, J M; Swaen, G M; Volovics, A; Slangen, J J; Van Vliet, K

    1990-03-01

    The results are presented from a case-control study, concerning the possible relation between silica exposure in the Dutch fine ceramic industry and lung cancer. For this purpose 381 male, age-matched pairs of primary lung cancer cases and controls were selected from the pathology department of the University Hospital in the region, where two large ceramic companies are located. Information about employment in the ceramic industry was obtained from the personnel and financial administration departments of the two companies. On the basis of job titles a panel of occupational hygiene experts reached consensus about the qualitative exposures of each individual worker. Twenty one per cent of the cases were employed in the ceramic industry, compared with 19% of the controls (odds ratio 1.11; 95% Cl: 0.77-1.61). Although the average employment period of cases and their relative silica exposure surpassed those of controls, odds ratios for long duration of employment and considerable exposure to respirable silica dust did not reach statistical significance. After constructing a qualitative exposure index, based on the amount and duration of exposure, a tendency towards a positive correlation with lung cancer emerged. No relation between specific histological tumour cell types and working in the ceramic industry emerged. Although the study does not suggest a consistent cause-effect relation between silica exposure in the regional, Dutch fine ceramic industry and lung cancer, an increased risk for the high exposure group in the past can not be totally excluded.

  10. Cellular effects and gene expression after exposure to amorphous silica nanoparticles in vitro

    DEFF Research Database (Denmark)

    Foldbjerg, Rasmus; Beer, Christiane; Wang, Jing

    ). Accordingly, the present study focused on the cytotoxicity of amorphous silica NPs in six different cell lines selected to explore the significance of tissue type and species. The cells were selected as three pairs of human/mouse cell lines derived from lung epithelium (A549 and ASB-XIV), colon epithelium (Ca...... lung cell line, A549, to investigate the mechanism of action. A concentration-dependent increase of cellular reactive oxygen species was demonstrated in silica NP exposed A549 cells. However, induction of oxidative stress related pathways was not found after silica NP exposure in gene array studies...

  11. Nanoscale confinement and interfacial effects on the dynamics and glass transition/crystallinity of thin adsorbed films on silica nanoparticles

    Science.gov (United States)

    Madathingal, Rajesh Raman

    hydrogen bonded to the silanols, and was independent of particle morphology. For methylated silica, (CH3) 3-SiO2, the adsorption isotherms were identical for colloidal and fumed silica, but Tg was depressed for the former, and comparable to the bulk value for the latter. The increased Tg of PMMA adsorbed onto fumed (CH3)3-SiO2 was attributed to the larger loops formed by the bridging PMMA chains between the silica aggregates. For nanocomposites the interphase region becomes more important as the surface/volume ratio of the nanoparticles increases. Polymers have chain dimensions (characterized by the radius of gyration, Rg) similar to the nanoparticles (Rnanoparticle) themselves, so that chain conformation, mobility and crystallinity can be affected by Rg/Rnanoparticle. Here, both the glass transition temperature (Tg) and degree of crystallinity (Xc) of polyethylene oxide (PEO) on individual SiO 2 nanoparticles of nominal 15, 50 and 100 nm diameter (2 RSiO2 ) , in which Rg (PEO) was greater, equal to or less than RSiO2 was investigated. Plateau adsorption of PEO on SiO2 nanoparticles (PEO-SiO2) increased in the order PEO-SiO 2 (100 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (15 nm). At plateau adsorption after melting and solidification, the samples were completely amorphous. The Tg of the adsorbed PEO increased in the order PEO-SiO 2 (100 nm) > PEO-SiO2 (50 nm) > PEO-SiO2 (15 nm); since the Tgs were above 25°C in all cases, the PEO behaved more like a brittle solid than an elastomer. For comparable amounts of PEO that were adsorbed from solution but not melted, the melt endotherm increased in the order PEO-SiO2 (15 nm) > PEO-SiO2 (50 nm) > PEO-SiO 2 (100 nm). These trends were interpreted as due to an increase in loop/tail lengths and thus flexibility, with a concomitant ability to crystallize, as Rg (PEO)/RSiO2 decreased and which was the result of less hydrogen bond formation between the oxygens of PEO and the silanols (SiOH) of the SiO 2 as the nanoparticle size decreased. This

  12. Elevated bulk-silica exposures and evidence for multiple aqueous alteration episodes in Nili Fossae, Mars

    Science.gov (United States)

    Amador, Elena S.; Bandfield, Joshua L.

    2016-09-01

    The Nili Fossae region of Mars contains some of the most mineralogically diverse bedrock on the planet. Previous studies have established three main stratigraphic units in the region: a phyllosilicate-bearing basement rock, a variably altered olivine-rich basalt, and a capping rock. Here, we present evidence for the localized alteration of the northeast Nili Fossae capping unit, previously considered to be unaltered. Both near-infrared and thermal-infrared spectral datasets were analyzed, including the application of a method for determining the relative abundance of bulk-silica (SiO2) over surfaces using thermal emission imaging system (THEMIS) images. Elevated bulk-silica exposures are present on surfaces previously defined as unaltered capping rock. Given the lack of spectral evidence for phyllosilicate, hydrated silica, or quartz phases coincident with the newly detected exposures-the elevated bulk-silica may have formed under a number of aqueous scenarios, including as a product of the carbonation of the underlying olivine-rich basalt under moderate water: rock scenarios and temperatures. Regardless of formation mechanism, the detection of elevated bulk-silica exposures in the Nili Fossae capping unit extends the history of aqueous activity in the region to include all three of the main stratigraphic units.

  13. Evaluation of workers' exposure to total, respirable and silica dust and the related health symptoms in Senjedak stone quarry, Iran.

    Science.gov (United States)

    Golbabaei, Farideh; Barghi, Mohammad-Ali; Sakhaei, Manouchehr

    2004-01-01

    The present research was conducted in a stone quarry of marble located in northeast of Iran. Time weighted average of total dust, respirable dust, and crystalline silica (alpha-quartz) concentration in workers' breathing zone were monitored by using both gravimetric and XRD methods. The results showed that the employees working in hammer drill process had the highest exposure to the total and respirable dust: 107.9 +/- 8.0 mg/m3, 11.2 +/- 0.77 mg/m3 respectively, while the cutting machine workers had the lowest exposure (9.3 +/- 3.0 mg/m3, 1.8 +/- 0.82 mg/m3). The maximum concentration of a-quartz in total and respirable dust were detected equal to 0.670 +/- 8.49 x 10(-2) and 5.7 x 10(-2) +/- 1.6 x 10(-2) mg/m3 respectively, which belonged to the exposure of the workers of hammer drill process. The prevalence of skin and respiratory symptoms were higher in hammer drill workers, however, respiratory symptoms showed no significant prevalence. Regarding the average age of workers (31.6 +/- 1.9 yr) and average of their work history (3.8 +/- 1.0 yr), these results were predictable.

  14. Health hazards due to the inhalation of amorphous silica.

    Science.gov (United States)

    Merget, R; Bauer, T; Küpper, H U; Philippou, S; Bauer, H D; Breitstadt, R; Bruening, T

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic ("thermal" or "fumed") silica, and (3) chemically or physically modified silica. According to the different physicochemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no study

  15. A Case with Systemic Sclerosis Following Exposure To Silica and Vibration

    Directory of Open Access Journals (Sweden)

    Aslı Ürkmez

    2012-06-01

    Full Text Available Systemic sclerosis is an autoimmune disease characterized by inflammatory, vascular and sclerotic changes in the internal organs. Although the etiology is not known with certainty; silica dust, which is one of the environmental risk factors, can lead to scleroderma by some immunological changes. In this case, a mine worker, who worked in a mercury mine during a 15-year period, developed systemic sclerosis due to exposure to chronic silica and vibration, is presented. (Turk J Dermatol 2012; 6: 45-7

  16. Worker exposure to silica dust in the non-mining sectors: literature review.

    CSIR Research Space (South Africa)

    Khoza, N

    2009-08-01

    Full Text Available of silicosis in the non-mining industry in South Africa, including a breakdown by industries. 10/2009 4 Statistics on the incidence of silicosis in the non-mining industry in South Africa, with a breakdown by industries. 10/2009 5 Statistics on the annual... of the literature review To present the major literature review findings on occupational silica dust exposure of workers in the non-mining industries/sectors Slide 5 in South Africa ? CSIR 2009 www.csir.co.za Silica overview...

  17. Respirable dust and silica exposure among World Trade Center cleanup workers.

    Science.gov (United States)

    Pavilonis, Brian T; Mirer, Franklin E

    2017-03-01

    The cleanup effort following the destruction of the World Trade Center (WTC) was unprecedented and involved removal of 1.8 million tons of rubble over a nine-month period. Work at the site occurred 24 hr a day, 7 days a week and involved thousands of workers during the process. The Occupational Safety and Health Administration (OSHA) conducted personal and area exposure sampling during the cleanup of the site. Secondary data analysis was performed on OSHA air sampling data for respirable dust and silica from September 2001 to June 2002 at the WTC recovery site to characterize workers' exposure. Results for silica and respirable particulate were stratified by area and personal samples as well as job task for analysis. Of 1108 samples included in the analysis, 693 were personal and 415 were area. The mean result for personal silica samples was 42 μg/m(3) (Range: 4.2-1800 μg/m(3)). Workers identified as drillers had the highest mean silica exposure (72 μg/m(3); range: 5.8-800 μg/m(3)) followed by workers identified as dock builders (67 μg/m(3); range: 5.8-670 μg/m(3)). The mean result for personal samples for respirable particulate was 0.44 mg/m(3) (range: 0.00010-13 mg/m(3)). There were no discernable trends in personal respirable dust and silica concentrations with date.

  18. Diseases associated with exposure to silica and nonfibrous silicate minerals. Silicosis and Silicate Disease Committee

    Energy Technology Data Exchange (ETDEWEB)

    1988-07-01

    Silicosis, a disease of historical importance, continues to occur cryptically today. Its pathogenesis is under ongoing study as new concepts of pathobiology evolve. In this article, the gross and microscopic features of the disease in the lungs and the lesions in lymph nodes and other viscera are described. These tissue changes are then discussed in the context of clinical disease and other possible or established complications of silica exposure (ie, scleroderma and rheumatoid arthritis, glomerulonephritis, and bronchogenic carcinoma). Silicates are members of a large family of common minerals, some of which have commercial importance. Silicates are less fibrogenic than silica when inhaled into the lungs, but cause characteristic lesions after heavy prolonged exposure. The features of these disease conditions are described herein. Various aspects of the mineralogy and tissue diagnosis of silicosis and lung disease due to silicates are reviewed. An overview of contemporary regulatory considerations is provided.204 references.

  19. Central Heat and Power Plant Coal Dust and Silica Risk Management, Eielson Air Force Base, Alaska

    Science.gov (United States)

    2014-12-11

    autoimmune diseases and in death from other nonmalignant respiratory diseases , including chronic obstructive pulmonary disease . There are some... Occupational Safety and Health Administration Occupational Exposure to Respirable Crystalline Silica; Proposed Rule. This consultative letter is in...strategies, occupational and environmental exposure limits, and air sampling methods as they apply to CHPP operations. 15. SUBJECT TERMS Silica

  20. Acute exposure to silica nanoparticles aggravate airway inflammation: different effects according to surface characteristics

    OpenAIRE

    Park, Hye Jung; Sohn, Jung-Ho; Kim, Yoon-Ju; Park, Yoon Hee; Han, Heejae; Park, Kyung Hee; Lee, Kangtaek; Choi, Hoon; Um, Kiju; Choi,In-Hong; Park, Jung-Won; Lee, Jae-Hyun

    2015-01-01

    Silica nanoparticles (SNPs) are widely used in many scientific and industrial fields despite the lack of proper evaluation of their potential toxicity. This study examined the effects of acute exposure to SNPs, either alone or in conjunction with ovalbumin (OVA), by studying the respiratory systems in exposed mouse models. Three types of SNPs were used: spherical SNPs (S-SNPs), mesoporous SNPs (M-SNPs), and PEGylated SNPs (P-SNPs). In the acute SNP exposure model performed, 6-week-old BALB/c ...

  1. Silica Supported Ceria Nanoparticles: A Hybrid Nanostructure To Increase Stability And Surface Reactivity Of Nano-crystalline Ceria

    Energy Technology Data Exchange (ETDEWEB)

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Varga, Tamas; Thevuthasan, Suntharampillai

    2014-01-21

    The mixed oxidation state (3+/4+) of ceria nanoparticles of smaller sizes make them attractive materials for their catalytic antioxidant biological properties. However the unmodified smaller ceria nanoparticles are limited in their use due to particles agglomeration and reduced surface chemical reactivity in the solutions used to disperse the nanoparticles. This work describes an effort to stabilize small ceria nanoparticles, retaining their desired activity, on a larger stable silica support. The ceria nanoparticles attached to silica was synthesized by a solution synthesis technique in which the surface functional groups of silica nanoparticles were found to be essential for the formation of smaller ceria nanoparticles. The surface chemical and vibrational spectroscopy analysis revealed cerium–silicate (Ce-O-Si) covalent bond linkage between silica and cerium oxide nanoparticles. The colloidal properties (agglomerate particle size and suspension stability) of ceria attached to silica was significantly improved due to inherent physico-chemical characteristics of silica against random collision and gravitation settling as opposed to unmodified ceria nanoparticles in solution. The bio-catalytic activity of ceria nanoparticles in the 3+ oxidation state was not found to be limited by attachment to the silica support as measured by free radical scavenging activity in different biological media conditions.

  2. Silica-sol-based spin-coating barrier layer against phosphorous diffusion for crystalline silicon solar cells.

    Science.gov (United States)

    Uzum, Abdullah; Fukatsu, Ken; Kanda, Hiroyuki; Kimura, Yutaka; Tanimoto, Kenji; Yoshinaga, Seiya; Jiang, Yunjian; Ishikawa, Yasuaki; Uraoka, Yukiharu; Ito, Seigo

    2014-01-01

    The phosphorus barrier layers at the doping procedure of silicon wafers were fabricated using a spin-coating method with a mixture of silica-sol and tetramethylammonium hydroxide, which can be formed at the rear surface prior to the front phosphorus spin-on-demand (SOD) diffusion and directly annealed simultaneously with the front phosphorus layer. The optimization of coating thickness was obtained by changing the applied spin-coating speed; from 2,000 to 8,000 rpm. The CZ-Si p-type silicon solar cells were fabricated with/without using the rear silica-sol layer after taking the sheet resistance measurements, SIMS analysis, and SEM measurements of the silica-sol material evaluations into consideration. For the fabrication of solar cells, a spin-coating phosphorus source was used to form the n(+) emitter and was then diffused at 930°C for 35 min. The out-gas diffusion of phosphorus could be completely prevented by spin-coated silica-sol film placed on the rear side of the wafers coated prior to the diffusion process. A roughly 2% improvement in the conversion efficiency was observed when silica-sol was utilized during the phosphorus diffusion step. These results can suggest that the silica-sol material can be an attractive candidate for low-cost and easily applicable spin-coating barrier for any masking purpose involving phosphorus diffusion.

  3. 78 FR 65242 - Occupational Exposure to Crystalline Silica; Extension of Comment Period; Extension of Period To...

    Science.gov (United States)

    2013-10-31

    ... at (202) 693- 1648. Mail, hand delivery, express mail, messenger, or courier service: You may submit... (877) 889-5627). Deliveries (hand, express mail, messenger, or courier service) are accepted during the... delivery, hand delivery, and messenger and courier service: Submit your materials to the OSHA Docket......

  4. Deformation Studies and Elasticity Measurements of Hydrophobic Silica Aerogels using Double Exposure Holographic Interferometry

    Science.gov (United States)

    Chikode, Prashant; Sabale, Sandip; Chavan, Sugam

    2017-01-01

    Holographic interferometry is mainly used for the non-destructive testing of various materials and metals in industry, engineering and technological fields. This technique may used to study the elastic properties of materials. We have used the double exposure holographic interferometry (DEHI) to study the surface deformation and elastic constant such as Young's modulus of mechanically stressed aerogel samples. Efforts have been made in the past to use non-destructive techniques like sound velocity measurements through aerogels. Hydrophobic Silica aerogels were prepared by the sol-gel process followed by supercritical methanol drying. The molar ratio of tetramethoxysilane: methyltrimethoxysilane: H2O constant at 1.2:0.8:6 while the methanol / tetramethoxysilane molar ratio (M) was varied systematically from 14 to 20 to obtain hydrophobic silica aerogels. After applying the weights on the sample in grams, double exposure holograms of aerogel samples have been successfully recorded. Double exposure causes localization of interference fringes on the aerogel surface and these fringes are used to determine the surface deformation and elastic modulus of the aerogels and they are in good agreement with the experiments performed by using four point bending. University Grants Commission for Minor Research Project and Department of Science and Technology for FIST Program.

  5. Microscopic polyangiitis accompanied by pleuritis as the only pulmonary manifestation of occupational silica exposure.

    Science.gov (United States)

    Shibuya, Hideki; Sano, Hiroko; Osamura, Kou; Kujime, Kosei; Hara, Kei; Hisada, Tetsuya

    2010-01-01

    A 68-year-old man, who had worked for processing quartz-containing stones for more than 50 years, complained of low-grade fever and arthralgia. Mediastinal lymph nodes were markedly swollen on chest computed tomography. Pathological findings of the lymph node were compatible with silicosis, with a high titer of myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA). During follow-up with prednisolone treatment, pleuritis and uveitis developed as manifestations of vasculitis. Thus, he was diagnosed with MPO-ANCA-associated vasculitis with occupational silica exposure, possibly microscopic polyangiitis (MPA). This case is rare, because pleuritis was the only pulmonary manifestation, without interstitial pneumonia, alveolar hemorrhage or glomerulonephritis.

  6. Comparison of nanoparticle exposures between fumed and sol-gel nano-silica manufacturing facilities.

    Science.gov (United States)

    Oh, Sewan; Kim, Boowook; Kim, Hyunwook

    2014-01-01

    Silica nanoparticles (SNPs) are widely used all around the world and it is necessary to evaluate appropriate risk management measures. An initial step in this process is to assess worker exposures in their current situation. The objective of this study was to compare concentrations and morphologic characteristics of fumed (FS) and sol-gel silica nanoparticles (SS) in two manufacturing facilities. The number concentration (NC) and particle size were measured by a real-time instrument. Airborne nanoparticles were subsequently analyzed using a TEM/EDS. SNPs were discharged into the air only during the packing process, which was the last manufacturing step in both the manufacturing facilities studied. In the FS packing process, the geometric mean (GM) NC in the personal samples was 57,000 particles/cm(3). The geometric mean diameter (GMD) measured by the SMPS was 64 nm. Due to the high-temperature formation process, the particles exhibited a sintering coagulation. In the SS packing process that includes a manual jet mill operation, the GM NC was calculated to be 72,000 particles/cm(3) with an assumption of 1,000,000 particles/cm(3) when the upper limit is exceeded (5% of total measure). The particles from SS process had a spherical-shaped morphology with GMD measured by SMPS of 94 nm.

  7. Exposure and compositional factors that influence polarization induced birefringence in silica glass

    Science.gov (United States)

    Allan, Douglas C.; Mlejnek, Michal; Neukirch, Ulrich; Smith, Charlene M.; Smith, Frances M.

    2007-03-01

    Silica glass exhibits a permanent anisotropic response, referred to as polarization induced birefringence (PIB), when exposed to short wavelength, polarized light. The magnitude of the PIB has been empirically correlated with the OH content of the glass. Our recent studies pertaining to PIB have focused on careful characterization of PIB, with particular emphasis on understanding all of the contributions to the measured birefringence signal and finally extracting only that signal associated with birefringence arising from exposure to a polarized light beam. We will demonstrate that a critical contributor to the total birefringence signal is birefringence that comes from exposure beam inhomogeneities. After subtracting beam profile effects we are able to show that PIB is proportional to the OH content of the glass. Polarized infrared (IR) measurements were performed on glasses that developed PIB as a consequence of exposure to polarized 157-nm light. These studies reveal that there is preferential bleaching of a specific hydroxyl (OH) species in the glass with OH aligned parallel to the incident polarization undergoing more bleaching than those perpendicular. Further, we observe a very strong correlation between the measured PIB of these samples and the anisotropic bleaching. From these studies we propose a mechanism that can explain the role of hydroxyl in PIB.

  8. Role of size and surface area for pro-inflammatory responses to silica nanoparticles in epithelial lung cells: importance of exposure conditions.

    Science.gov (United States)

    Skuland, T; Ovrevik, J; Låg, M; Refsnes, M

    2014-03-01

    The present study compared non-crystalline silica particles of nano (50nm)- and submicro (500nm)-size (Si50 and Si500) for the potential to induce cytokine responses in bronchial epithelial lung cells (BEAS-2B). The cell cultures were exposed to equal mass and surface area concentrations of the two particles in different exposure media; LHC-9 and DMEM:F12. The state of agglomeration was different in the two media; with marked agglomeration in LHC-9 and nearly no agglomeration in DMEM:F12. On a mass basis, Si50 was more potent than Si500 in inducing cytokine responses in both exposure media. In contrast, upon exposure to similar surface area concentrations, Si500 was more potent than Si50 in DMEM:F12. This might be due to different agglomeration/sedimentation properties of Si50 versus Si500 in the two media. However, influence of differences in particle reactivity or particle uptake cannot be excluded. The data indicated no qualitative changes in the cytokine gene-expression patterns induced by the two particles, suggesting effects through similar mechanisms. These aspects might be of importance for interpretation of in vitro studies of nanomaterials. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Biocompatibility of crystalline opal nanoparticles

    Directory of Open Access Journals (Sweden)

    Hernández-Ortiz Marlen

    2012-10-01

    Full Text Available Abstract Background Silica nanoparticles are being developed as a host of biomedical and biotechnological applications. For this reason, there are more studies about biocompatibility of silica with amorphous and crystalline structure. Except hydrated silica (opal, despite is presents directly and indirectly in humans. Two sizes of crystalline opal nanoparticles were investigated in this work under criteria of toxicology. Methods In particular, cytotoxic and genotoxic effects caused by opal nanoparticles (80 and 120 nm were evaluated in cultured mouse cells via a set of bioassays, methylthiazolyldiphenyl-tetrazolium-bromide (MTT and 5-bromo-2′-deoxyuridine (BrdU. Results 3T3-NIH cells were incubated for 24 and 72 h in contact with nanocrystalline opal particles, not presented significant statistically difference in the results of cytotoxicity. Genotoxicity tests of crystalline opal nanoparticles were performed by the BrdU assay on the same cultured cells for 24 h incubation. The reduction of BrdU-incorporated cells indicates that nanocrystalline opal exposure did not caused unrepairable damage DNA. Conclusions There is no relationship between that particles size and MTT reduction, as well as BrdU incorporation, such that the opal particles did not induce cytotoxic effect and genotoxicity in cultured mouse cells.

  10. A comprehensive assessment of exposures to respirable dust and silica in the taconite mining industry.

    Science.gov (United States)

    Hwang, Jooyeon; Ramachandran, Gurumurthy; Raynor, Peter C; Alexander, Bruce H; Mandel, Jeffrey H

    2017-05-01

    This study assessed the present-day levels (year 2010-2011) of exposure to respirable dust (RD) and respirable silica (RS) in taconite mines and evaluated how the mining process influences exposure concentrations. Personal samples (n = 679) were collected to assess exposure levels of workers to RD and RS at six mines in the Mesabi Iron Range of Minnesota. The RD and RS concentrations were measured using the National Institute for Occupational Safety and Health (NIOSH) 0600 and NIOSH 7500, respectively. Between-mine, between-SEG (similar exposure groups), within-SEG, and within-worker components of variability for RD and RS exposures were estimated using a two- or three-way nested random-effects ANOVA model. The majority of RD concentrations across all mines were below the Mine Safety and Health Administration (MSHA) Permissible Exposure Limit (PEL). The highest concentrations of RD were often observed in either the Pelletizing or Crushing departments, which are inherently dusty operations. With a few exceptions, the concentrations of RS in the crushing and concentrating processes were higher than those in the other mining processes, as well as higher than the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV) for RS. The magnetic separation and flotation processes in the concentrating department reduced the levels of RS significantly, and lowered the percentage of quartz in RD in the pelletizing department. There was little variability among the six mines or between the two mineralogically distinct zones for either RD or RS exposures. The between-SEG variability for RS did not differ substantially across most of the mines and was a major component of exposure variance. The within-SEG (or between-worker) variance component was typically the smallest because in many instances one worker from a SEG within a mine was monitored multiple times. Some of these findings were affected by the degree of censoring in each SEG and mine

  11. Health hazards due to the inhalation of amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Merget, R.; Bruening, T. [Research Institute for Occupational Medicine (BGFA), Bochum (Germany); Bauer, T. [Bergmannsheil, University Hospital, Department of Internal Medicine, Division of Pneumonology, Allergology and Sleep Medicine, Bochum (Germany); Kuepper, H.U.; Breitstadt, R. [Degussa-Huels Corp., Wesseling (Germany); Philippou, S. [Department of Pathology, Augusta Krankenanstalten, Bochum (Germany); Bauer, H.D. [Research Institute for Hazardous Substances (IGF), Bochum (Germany)

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic (''thermal'' or ''fumed'') silica, and (3) chemically or physically modified silica. According to the different physico-chemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or

  12. High resolution characterization of modifications in fused silica after exposure to low fluence 355 nm laser at different repetition frequencies.

    Science.gov (United States)

    Li, C H; Ju, X; Jiang, X D; Huang, J; Zhou, X D; Zheng, Z; Wu, W D; Zheng, W G; Li, Z X; Wang, B Y; Yu, X H

    2011-03-28

    We report on the characterization of modifications in fused silica after exposure to low fluence (2 J/cm2) 355 nm laser at repetition frequencies of 1 Hz, 5 Hz and 10 Hz. Synchrotron based XRF spectroscopy is employed to study concentration variation of metal inclusions in the surface layer. Positron annihilation lifetime spectroscopy is used to probe atomic size defects variation in bulk silica. FT-IR is used to characterize changes of bond length and angle of Si-O-Si covalent bond of irradiated silica. Compared to the basic frequency, the big loss of cerium and iron concentration, the size enlargement of vacancy cluster and the decrease of Si-O-Si covalent bond length after 10 Hz laser irradiation are illustrated by our data. These tiny modifications provide important data to investigate laser damage mechanism.

  13. Exposure assessment to dust and free silica for workers of Sangan iron ore mine in Khaf, Iran.

    Science.gov (United States)

    Naghizadeh, Ali; Mahvi, Amir Hossein; Jabbari, Hossein; Derakhshani, Elham; Amini, Hassan

    2011-11-01

    We aimed to conduct an exposure assessment to dust and free silica for workers of Sangan iron ore mine in Khaf, Iran. The maximum concentrations of total dust and free silica were measured in crusher machine station at 801 ± 155 and 26 ± 7 mg/m(3), respectively. Meanwhile, the minimum concentrations were measured in official and safeguarding station at 8.3 ± 2 and 0.012 ± 0.002 mg/m(3), respectively. Also, the maximum concentrations of respirable dust and free silica were measured in Tappeh Ghermez drilling no. 1 at 66 ± 13 and 1.5 ± 0.4 mg/m(3), respectively, while the minimum concentrations were measured in pneumatic hammer at 5.26 ± 3 and 0.01 ± 0.005 mg/m(3), respectively. Considerate to Iranian standard for respirable dust concentrations (0.11 mg/m(3)) and international standards (ACGIH = 0.1 and NIOSH = 0.05 mg/m(3)), it was found that dust and free silica amounts were much higher than national and international standard levels in this mine.

  14. Silica Nephropathy

    Directory of Open Access Journals (Sweden)

    N Ghahramani

    2010-06-01

    Full Text Available Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2 is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600–7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents.

  15. Silica in Protoplanetary Disks

    CERN Document Server

    Sargent, B A; Tayrien, C; McClure, M K; Li, A; Basu, A R; Manoj, P; Watson, D M; Bohac, C J; Furlan, E; Kim, K H; Green, J D; Sloan, G C

    2008-01-01

    Mid-infrared spectra of a few T Tauri stars (TTS) taken with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope show prominent narrow emission features indicating silica (crystalline silicon dioxide). Silica is not a major constituent of the interstellar medium; therefore, any silica present in the circumstellar protoplanetary disks of TTS must be largely the result of processing of primitive dust material in the disks surrouding these stars. We model the silica emission features in our spectra using the opacities of various polymorphs of silica and their amorphous versions computed from earth-based laboratory measurements. This modeling indicates that the two polymorphs of silica, tridymite and cristobalite, which form at successively higher temperatures and low pressures, are the dominant forms of silica in the TTS of our sample. These high temperature, low pressure polymorphs of silica present in protoplanetary disks are consistent with a grain composed mostly of tridymite named Ada found...

  16. Deformation of Ordered Mesoporous Silica Structures on Exposure to High Temperatures

    Directory of Open Access Journals (Sweden)

    John B. Lowe

    2014-01-01

    Full Text Available Ordered mesoporous silica materials are of interest for a wide range of applications. In many of these, elevated temperatures are used either in the preparation of the material or during its use. Therefore, an understanding of the effect of high temperature treatments on these materials is desirable. In this work, a detailed structural study is performed on silicas with three representative pore structures: a 2-D hexagonal pore arrangement (SBA-15, a continuous 3D cubic bimodal pore structure (KIT-6, and a 3D large cage pore structure (FDU-12. Each silica is studied as prepared and after treatment at a series of temperatures between 300 and 900°C. Pore structures are imaged using Transmission Electron Microscopy. This technique is used in conjunction with Small-Angle X-ray Diffraction, gas physisorption, and 29Si solid state Nuclear Magnetic Resonance. Using these techniques, the pore size distributions, the unit cell dimensions of the mesoporous structures, and the relative occupancy of the distinct chemical environments of Si within them are cross correlated for the three silicas and their evolution with treatment temperature is elucidated. The physical and chemical properties before, during, and after collapse of these structures at high temperatures are described as are the differences in behavior between the three silica structures.

  17. Assessment of side-effects by Ludox TMA silica nanoparticles following a dietary exposure on the bumblebee Bombus terrestris.

    Science.gov (United States)

    Mommaerts, Veerle; Jodko, Katarzyna; Thomassen, Leen C J; Martens, Johan A; Kirsch-Volders, Micheline; Smagghe, Guy

    2012-08-01

    We assessed lethal and sublethal side-effects of Ludox TMA silica nanoparticles on a terrestrial pollinator, Bombus terrestris (Linnaeus), via a dietary exposure. Dynamic light scattering analysis confirmed that silica Ludox TMA nanoparticles remained in suspension in the drinking sugar water. Exposure of bumblebee microcolonies during 7 weeks to the different nanoparticle concentrations (high: 34, 170 and 340 mg/l and low: 34 and 340 μg/l) did not cause worker mortality compared to the controls. Also no effect on the worker foraging behavior was observed after exposure to nanoparticles concentrations up to 340 μg/l. In contrast, the high concentrations (≥34 mg/l) resulted in a total loss of reproduction. Using histological analysis we confirmed severe midgut epithelial injury in intoxicated workers (≥34 mg/l). Despite the fact that these concentrations are much higher than the predicted environmental concentrations, precaution is still needed as information regarding their fate in the terrestrial environment and their potency to bioaccumulate and biomagnificate is lacking.

  18. Long-Term Exposure to Silica Dust and Risk of Total and Cause-Specific Mortality in Chinese Workers: A Cohort Study

    Science.gov (United States)

    Chen, Weihong; Liu, Yuewei; Wang, Haijiao; Hnizdo, Eva; Sun, Yi; Su, Liangping; Zhang, Xiaokang; Weng, Shaofan; Bochmann, Frank; Hearl, Frank J.; Chen, Jingqiong; Wu, Tangchun

    2012-01-01

    Background Human exposure to silica dust is very common in both working and living environments. However, the potential long-term health effects have not been well established across different exposure situations. Methods and Findings We studied 74,040 workers who worked at 29 metal mines and pottery factories in China for 1 y or more between January 1, 1960, and December 31, 1974, with follow-up until December 31, 2003 (median follow-up of 33 y). We estimated the cumulative silica dust exposure (CDE) for each worker by linking work history to a job–exposure matrix. We calculated standardized mortality ratios for underlying causes of death based on Chinese national mortality rates. Hazard ratios (HRs) for selected causes of death associated with CDE were estimated using the Cox proportional hazards model. The population attributable risks were estimated based on the prevalence of workers with silica dust exposure and HRs. The number of deaths attributable to silica dust exposure among Chinese workers was then calculated using the population attributable risk and the national mortality rate. We observed 19,516 deaths during 2,306,428 person-years of follow-up. Mortality from all causes was higher among workers exposed to silica dust than among non-exposed workers (993 versus 551 per 100,000 person-years). We observed significant positive exposure–response relationships between CDE (measured in milligrams/cubic meter–years, i.e., the sum of silica dust concentrations multiplied by the years of silica exposure) and mortality from all causes (HR 1.026, 95% confidence interval 1.023–1.029), respiratory diseases (1.069, 1.064–1.074), respiratory tuberculosis (1.065, 1.059–1.071), and cardiovascular disease (1.031, 1.025–1.036). Significantly elevated standardized mortality ratios were observed for all causes (1.06, 95% confidence interval 1.01–1.11), ischemic heart disease (1.65, 1.35–1.99), and pneumoconiosis (11.01, 7.67–14.95) among workers exposed

  19. In vitro comet and micronucleus assays do not predict morphological transforming effects of silica particles in Syrian Hamster Embryo cells.

    Science.gov (United States)

    Darne, Christian; Coulais, Catherine; Terzetti, Francine; Fontana, Caroline; Binet, Stéphane; Gaté, Laurent; Guichard, Yves

    2016-01-15

    Crystalline silica particles and asbestos have both been classified as carcinogenic by the International Agency for Research on Cancer (IARC). However, because of the limited data available, amorphous silica was not classifiable. In vitro, the carcinogenic potential of natural crystalline and amorphous silica particles has been revealed by the Syrian Hamster Embryo (SHE) cell transformation assay. On the other hand, the genotoxic potential of those substances has not been investigated in SHE cells. And yet, genotoxicity assays are commonly used for hazard evaluation and they are often used as in vitro assays of reference to predict a possible carcinogenic potential. The main objective of this study was to compare the genotoxic potential and the carcinogenic potential of different crystalline and amorphous silica particles in SHE cells. Three silica samples of different crystallinity were used: natural amorphous silica, partially crystallized silica and quartz silica particles. Their genotoxicity were tested through the in vitro micronucleus assay and the comet assay in SHE, and their carcinogenic potential through the SHE transformation assay. In addition, silica samples were also tested with the same genotoxicity assays in V79 hamster-lung cells, a common in vitro model for particle exposure. Results obtained in the micronucleus and the comet assays show that none of the silica was capable of inducing genotoxic effects in SHE cells and only the amorphous silica induced genotoxic effects in V79 cells. However in the SHE cell transformation assays, the partially crystallized and quartz silica were able to induce morphological cell transformation. Together, these data suggest that, in vitro, the short-term genotoxic assays alone are not sufficient to predict the hazard and the carcinogenic potential of this type of particles; SHE transformation assay appears a more reliable tool for this purpose and should be included in the "in vitro battery assays" for hazard

  20. Change of Exposure Response over Time and Long-Term Risk of Silicosis among a Cohort of Chinese Pottery Workers

    Directory of Open Access Journals (Sweden)

    Yuewei Liu

    2011-07-01

    Full Text Available An analysis was conducted on a cohort of Chinese pottery workers to estimate the exposure-response relationship between respirable crystalline silica dust exposure and the incidence of radiographically diagnosed silicosis, and to estimate the long-term risk of developing silicosis until the age of 65. The cohort comprised 3,250 employees with a median follow-up duration of around 37 years. Incident cases of silicosis were identified via silicosis registries (Chinese X-ray stage I, similar to International Labor Organisation classification scheme profusion category 1/1. Individual exposure to respirable crystalline silica dust was estimated based on over 100,000 historical dust measurements. The association between dust exposure, incidence and long-time risk of silicosis was quantified by Poisson regression analysis adjusted for age and smoking. The risk of silicosis depended not only on the cumulative respirable crystalline silica dust exposures, but also on the time-dependent respirable crystalline silica dust exposure pattern (long-term average concentration, highest annual concentration ever experienced and time since first exposure. A long-term “excess” risk of silicosis of approximately 1.5/1,000 was estimated among workers with all annual respirable crystalline silica dust concentration estimates less than 0.1 mg/m3, using the German measurement strategy. This study indicates the importance of proper consideration of exposure information in risk quantification in epidemiological studies.

  1. Bleaching of optical activity induced by UV Laser exposure in natural silica

    OpenAIRE

    Cannas, M.; Messina, F.

    2004-01-01

    We report experimental data on two types of natural silica, differing for their OH content, irradiated with UV photons (4.66 eV) from a pulsed Nd:YAG laser. Irradiation induces a reduction of the absorption band at 5.12eV and of the associated emissions at 3.14eV and 4.28eV, ascribed to twofold coordinated Ge (=Ge'') centers pre-existing in our samples. The bleaching is mainly due to the post-irradiation conversion of =Ge'' into the paramagnetic H(II) center via trapping of a H atom. Comparis...

  2. Thickness and morphology of polyelectrolyte coatings on silica surfaces before and after protein exposure studied by atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Haselberg, Rob, E-mail: r.haselberg@vu.nl [Biomolecular Analysis, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht (Netherlands); AIMMS Division of BioMolecular Analysis, VU University Amsterdam, de Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Flesch, Frits M. [Biomolecular Analysis, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht (Netherlands); Boerke, Arjan [Department of Biochemistry and Cell Biology, Utrecht University, Yalelaan 2, 3508 TD Utrecht (Netherlands); Somsen, Govert W. [Biomolecular Analysis, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht (Netherlands); AIMMS Division of BioMolecular Analysis, VU University Amsterdam, de Boelelaan 1083, 1081 HV Amsterdam (Netherlands)

    2013-05-24

    Graphical abstract: -- Highlights: •Atomic force microscopy is used to characterize polyelectrolyte coatings. •Coating procedure leads to nm-thick layers on a silica surface. •Polyelectrolyte coatings effectively prevent protein adsorption. •AFM provides the high resolution to investigate these thin films. •AFM results support earlier findings obtained with capillary electrophoresis. -- Abstract: Analyte–wall interaction is a significant problem in capillary electrophoresis (CE) as it may compromise separation efficiencies and migration time repeatability. In CE, self-assembled polyelectrolyte multilayer films of Polybrene (PB) and dextran sulfate (DS) or poly(vinylsulfonic acid) (PVS) have been used to coat the capillary inner wall and thereby prevent analyte adsorption. In this study, atomic force microscopy (AFM) was employed to investigate the layer thickness and surface morphology of monolayer (PB), bilayer, (PB-DS and PB-PVS), and trilayer (PB-DS-PB and PB-PVS-PB) coatings on glass surfaces. AFM nanoshaving experiments providing height distributions demonstrated that the coating procedures led to average layer thicknesses between 1 nm (PB) and 5 nm (PB-DS-PB), suggesting the individual polyelectrolytes adhere flat on the silica surface. Investigation of the surface morphology of the different coatings by AFM revealed that the PB coating does not completely cover the silica surface, whereas full coverage was observed for the trilayer coatings. The DS-containing coatings appeared on average 1 nm thicker than the corresponding PVS-containing coatings, which could be attributed to the molecular structure of the anionic polymers applied. Upon exposure to the basic protein cytochrome c, AFM measurements showed an increase of the layer thickness for bare (3.1 nm) and PB-DS-coated (4.6 nm) silica, indicating substantial protein adsorption. In contrast, a very small or no increase of the layer thickness was observed for the PB and PB-DS-PB coatings

  3. Biological effects induced by BSA-stabilized silica nanoparticles in mammalian cell lines.

    Science.gov (United States)

    Foldbjerg, Rasmus; Wang, Jing; Beer, Christiane; Thorsen, Kasper; Sutherland, Duncan S; Autrup, Herman

    2013-06-25

    Much of the concerns regarding engineered nanoparticle (NP) toxicity are based on knowledge from previous studies on particles in ambient air or occupational situations. E.g., the effects of exposure to silica dust particles have been studied intensely due to the carcinogenicity of crystalline silica. However, the increasing usage of engineered amorphous silica NPs has emphasized the need for further mechanistic insight to predict the consequences of exposure to the amorphous type of silica NPs. The present study focused on the in vitro biological effects following exposure to well-dispersed, BSA-stabilized, amorphous silica NPs whereas unmodified silica NPs where included for reasons of comparison. The cytotoxicity of the silica NPs was investigated in six different cell lines (A549, THP-1, CaCo-2, ASB-XIV, J-774A.1, and Colon-26) selected to explore the significance of organ and species sensitivity in vitro. Viability data demonstrated that macrophages were most sensitive to silica NP and interestingly, murine cell lines were generally found to be more sensitive than comparable human cell lines. Further studies were conducted in the human epithelial lung cell line, A549, to explore the molecular mechanism of silica toxicity. Generation of reactive oxygen species, one of the proposed toxicological mechanisms of NPs, was investigated in A549 cells by the dichlorofluorescin (DCF) assay to be significantly induced at NP concentrations above 113 μg/mL. However, induction of oxidative stress related pathways was not found after silica NP exposure for 24 h in gene array studies conducted in A549 cells at a relatively low NP concentration (EC20). Up-regulated genes (more than 2-fold) were primarily related to lipid metabolism and biosynthesis whereas down-regulated genes included several processes such as transcription, cell junction, extra cellular matrix (ECM)-receptor interaction and others. Thus, gene expression data proposes that several cellular processes other

  4. Nucleation and growth of AlN: Self-limiting reactions and the regeneration of active sites using sequential exposures of trimethylaluminum and ammonia on silica at 600 K

    Energy Technology Data Exchange (ETDEWEB)

    Bartram, M.E.; Michalske, T.A.; Rogers, J.W. Jr. (Sandia National Laboratory, Albuquerque, NM (United States)); Paine, R.T. (Univ. of New Mexico, Albuquerque, NM (United States))

    1993-10-01

    The sequential reactions of trimethylaluminum (TMA) and ammonia have been studied in the 1-Torr pressure regime at 600 K with FTIR (Fourier transform infrared spectroscopy) and XPS (X-ray photoelectron spectroscopy). Transmission FTIR spectra acquired through a silica substrate reveal that extended ammonia exposure can overcome the desporption of ammonia from the methylaluminum:ammonia surface adduct identified previously. This increases the number of reactions between methyl groups and ammonia on adjacent adducts and thereby maximizes the population of bridging amino groups on the surface (Al-NH[sub 2]-Al). The resulting NH[sub 2] species can then react with TMA from an additional exposure to produce a new layer of methylaluminum species. Repetitions of these sequencial reactions demonstrate that the respective TMA and ammonia reactions are self-limiting, regenerating active sites suitable for promoting chemisorption of the next precursor for the layer-by-layer growth of aluminum nitride. These studies suggest that in addition to providing transport for the source elements, functional groups that remain chemisorbed on the surface may also be used to enhance the uptake of the next precursor and influence bond directionality during film growth at low temperatures. Although the crystallinity of the aluminim nitride film is expected to be limited by the amorphous nature of the silica substrate, the results from a simple conformational analysis suggest a general rule that can be applied to any substrate; if a concerted reaction between dissimilar functional groups is the only mechanism available for growth, then this mechanism will ultimately limit long-range order in the resulting film. 35 refs., 8 figs.

  5. Crystalline mesoporous metal oxide

    Institute of Scientific and Technical Information of China (English)

    Wenbo Yue; Wuzong Zhou

    2008-01-01

    Since the discovery of many types of mesoporous silicas, such as SBA-15, KIT-6, FDU-12 and SBA-16, porous crystalline transition metal oxides, such as Cr2O3, Co3O4, In2O3, NiO, CeO2, WO3, Fe2O3 and MnO2, have been synthesized using the mesoporous silicas as hard templates. Several synthetic methods have been developed. These new porous materials have high potential applications in catalysis, Li-ion rechargeable batteries and gas sensors. This article gives a brief review of the research of porous crystals of metal oxides in the last four years.

  6. Checklist Model to Improve Work Practices in Small-Scale Demolition Operations with Silica Dust Exposures

    Directory of Open Access Journals (Sweden)

    Paul Succop

    2012-01-01

    Full Text Available A systematic approach was developed to review, revise and adapt existing exposure control guidance used in developed countries for use in developing countries. One-page employee and multiple-page supervisor guidance sheets were adapted from existing documents using a logic framework and workers were trained to use the information to improve work practices. Interactive, hands-on training was delivered to 26 workers at five small-scale demolition projects in Maputo City, Mozambique, and evaluated. A pre-and-post walkthrough survey used by trained observers documented work practice changes. Worker feedback indicated that the training was effective and useful. Workers acquired knowledge (84% increase, p < 0.01 and applied the work practice guidance. The difference of proportions between use of work practice components before and after the intervention was statistically significant (p < 0.05. Changes in work practices following training included preplanning, use of wet methods and natural ventilation and end-of-task review. Respirable dust measurements indicated a reduction in exposure following training. Consistency in observer ratings and observations support the reliability and validity of the instruments. This approach demonstrated the short-term benefit of training in changing work practices; follow-up is required to determine the long-term impact on changes in work practices, and to evaluate the need for refresher training.

  7. Apoptosis induction and histological changes in rat kidney following Cd-doped silica nanoparticle exposure: evidence of persisting effects.

    Science.gov (United States)

    Coccini, Teresa; Barni, Sergio; Manzo, Luigi; Roda, Elisa

    2013-10-01

    Abstract Histological and immunocytochemical methods were used to examine rat's renal responses to intratracheal (i.t.) instillation of model cadmium-containing silica nanoparticles (Cd-SiNPs) and also exploring whether these potential modifications would be associated with toxicogenomic changes. Renal effects of Cd-SiNPs (1 mg/rat), CdCl2 (400 µg/rat), SiNPs (600 µg/rat) or 0.1 ml saline (control), assessed 7 and 30 d post-i.t., included (i) induction of apoptosis, (ii) cell proliferation and (iii) the overall toxic response evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, proliferating cell nuclear antigen (PCNA) immunohistochemistry as well as Periodic acid Schiff and Hematoxylin & Eosin, respectively. Area-specific apoptosis was observed in all treatment groups, the cortex and inner medulla being the most affected regions: the apoptotic changes were apparent seven days post-exposure in both areas and were still observable in inner medulla at day 30. Apoptotic frequency increase was more pronounced in Cd-SiNP-treated animals compared to either CdCl2 or SiNPs groups. At day 7, the observed parallel increased number of PCNA immunopositive cells may be associated with an enhanced cell proliferation aimed at replacing the damaged cells. Histopathological findings demonstrated comparable morphological changes of the renal structure (at glomerular and tubular levels) occurring after all treatments at both time-points and more markedly 30 d after instillation. Both morphological and toxicogenomic evaluations confirmed long-lasting renal effects of Cd-SiNPs on apoptosis and regulatory processes. Bare SiNPs i.t. administration caused morphological and apoptotic changes but did not modify gene expression profile in kidney. These findings substantiate the notion that multiple assays and an integrated testing strategy should be recommended to characterize toxicological responses to nanoparticles in mammalian systems.

  8. Respirable silica dust exposure amongst foundry workers in Gauteng, South Africa: A task-based risk assessment

    CSIR Research Space (South Africa)

    Khoza, NN

    2012-09-01

    Full Text Available Centre for Mining Innovation’s Laboratory SANAS accreditation (ISO 17025) for both x-ray powder diffraction (XRD) and particle size analysis methods. The overall TWA mean and median respirable silica dust concentration was 0.184 mg/m³ and 0.167 mg...

  9. Inflammatory response and blood hypercoagulable state induced by low level co-exposure with silica nanoparticles and benzo[a]pyrene in zebrafish (Danio rerio) embryos.

    Science.gov (United States)

    Duan, Junchao; Yu, Yang; Li, Yang; Wang, Yapei; Sun, Zhiwei

    2016-05-01

    Given the severe situation of world-wide particulate matter air pollution, it is urgent to explore the combined effects of particulate matter components on cardiovascular system. Using zebrafish model, this study was aimed to determine whether the low level co-exposure to silica nanoparticles (SiNPs) and benzo[a]pyrene (B[a]P) had a pronounced cardiovascular toxicity than the single exposure to either SiNPs or B[a]P alone. The FTIR and TGA analysis showed that the co-exposure system possessed of high absorption and thermal stability. Embryos exposed to SiNPs or B[a]P alone did not show cardiac toxicity phenotype at the NOAEL level. However, embryos co-exposed to SiNPs and B[a]P exhibited pericardial edema and bradycardia. While ROS generation remained unaffected, the co-exposure induced significant neutrophil-mediated inflammation and caused erythrocyte aggregation in caudal vein of embryos. Microarray analysis and STC analysis were performed to screen the cardiovascular-related differential expression genes and the expression trend of genes in each group. The co-exposure of SiNPs and B[a]P significantly enhanced the expression of proinflammatory and procoagulant genes. Moreover, the co-exposure markedly increased the phosphorylated AP-1/c-Jun and induced TF expression, but not NF-κB p65. This study for the first time demonstrated the inflammatory response and blood hypercoagulable state were triggered by the combination of SiNPs and B[a]P at low level exposure.

  10. Hydrothermal stability of microporous silica and niobia-silica membranes

    NARCIS (Netherlands)

    Boffa, V.; Blank, David H.A.; ten Elshof, Johan E.

    2008-01-01

    The hydrothermal stability of microporous niobia–silica membranes was investigated and compared with silica membranes. The membranes were exposed to hydrothermal conditions at 150 and 200 °C for 70 h. The change of pore structure before and after exposure to steam was probed by single-gas permeation

  11. Fungus-mediated biotransformation of amorphous silica in rice husk to nanocrystalline silica.

    Science.gov (United States)

    Bansal, Vipul; Ahmad, Absar; Sastry, Murali

    2006-11-01

    Rice husk is a cheap agro-based waste material, which harbors a substantial amount of silica in the form of amorphous hydrated silica grains. However, there have been no attempts at harnessing the enormous amount of amorphous silica present in rice husk and its room-temperature biotransformation into crystalline silica nanoparticles. In this study, we address this issue and describe how naturally deposited amorphous biosilica in rice husk can be bioleached and simultaneously biotransformed into high value crystalline silica nanoparticles. We show here that the fungus Fusarium oxysporum rapidly biotransforms the naturally occurring amorphous plant biosilica into crystalline silica and leach out silica extracellularly at room temperature in the form of 2-6 nm quasi-spherical, highly crystalline silica nanoparticles capped by stabilizing proteins; that the nanoparticles are released into solution is an advantage of this process with significant application and commercial potential. Calcination of the silica nanoparticles leads to loss of occluded protein and to an apparently porous structure often of cubic morphology. The room-temperature synthesis of oxide nanomaterials using microorganisms starting from potential cheap agro-industrial waste materials is an exciting possibility and could lead to an energy-conserving and economically viable green approach toward the large-scale synthesis of oxide nanomaterials.

  12. NMR-based metabonomics study of sub-acute hepatotoxicity induced by silica nanoparticles in rats after intranasal exposure.

    Science.gov (United States)

    Parveen, A; Rizvi, S H M; Gupta, A; Singh, R; Ahmad, I; Mahdi, F; Mahdi, A A

    2012-12-22

    Silica nanoparticles (SiO(2) NPs) are widely used commercially; however, their potential toxicity on human health has attracted particular attention. In the present study, the intranasal toxicological effect of 10nm and 80nm SiO(2) NPs (dosed at 150μg for 90 days) on rats was investigated using conventional approaches and metabonomics analysis of serum. Oxidative stress was measured by assessing Lipid peroxide (LPO) levels and enzymatic activities of Superoxide dismutase (SOD), Catalase (CAT), and Glutathione (GSH) levels in liver tissue homogenate. These biochemical observations were supplemented by histological examination of liver sections. SiO(2) NPs enhanced lipid peroxidation with concomitant reduction in SOD, CAT, and GSH content. In addition, SiO(2) NPs also produced alterations in hepatic histopathology. We also evaluated the effect of SiO(2) NPs on the activities of hepatic enzymes such as aminotransferases (ALT/AST) and alkaline phosphatase (ALP) which revealed significant increase in their activity when compared with control. Metabonomic profile of 90 days SiO(2) NPs treated rat sera exhibited significant increase in lactate, alanine, acetate, creatine and choline coupled with a considerable decrease in glucose level. These perturbations, on the whole, implicate impairment in tricarboxylic acid cycle and liver metabolism, which suggests that silica nanoparticles may have a potential to induce hepatotoxicity in rats.

  13. Silica nanoparticles are less toxic to human lung cells when deposited at the air–liquid interface compared to conventional submerged exposure

    Directory of Open Access Journals (Sweden)

    Alicja Panas

    2014-09-01

    analyses. Surprisingly, cells exposed at the ALI were less sensitive to silica NPs as evidenced by reduced cytotoxicity and inflammatory responses.Conclusion: Amorphous silica NPs induced qualitatively similar cellular responses under submerged conditions and at the ALI. However, submerged exposure to NPs triggers stronger effects at much lower cellular doses. Hence, more studies are warranted to decipher whether cells at the ALI are in general less vulnerable to NPs or specific NPs show different activities dependent on the exposure method.

  14. Lung cancer and exposure to quartz and diesel exhaust in Swedish iron ore miners with concurrent exposure to radon.

    Science.gov (United States)

    Bergdahl, Ingvar A; Jonsson, Håkan; Eriksson, Kåre; Damber, Lena; Järvholm, Bengt

    2010-08-01

    Studies of underground miners have documented an increased risk of lung cancer mainly linked to radon exposure but possibly influenced by other concurrent exposures. A cohort study was carried out in 8321 iron ore miners with low exposure to radon, employed in 1923-1998 and followed up for lung cancer in 1958-2000. Historical exposures to radon, crystalline silica and diesel exhaust were assessed. Data including exposure to radon, quartz and diesel exhaust from another mine with higher exposure to radon were reanalysed. Miners had increased risk for lung cancer (SIR 1.48 (95% CI 1.22 to 1.78), based on 112 cases during 227,000 person-years). The increased risk could not be explained by exposure to radon or diesel exhaust but was associated with exposure to crystalline silica: SIR 0.96 (0.53 to 1.62), 1.45 (1.10 to 1.87), 1.99 (1.31 to 2.90) and 1.77 (0.92 to 3.10) in groups with exposure to 0, 0-2, 2-5 and >5 mg years/m3, respectively. Reanalysis of data from the other mine indicated that quartz was a possible confounder in the analysis of relationship between radon and lung cancer. In the highest radon exposed group, the point estimate for the RR decreased from 5.65 to 3.90 when adjusting for concurrent exposure to quartz. Crystalline silica, a known carcinogen, probably affects lung cancer risk in iron ore miners. The main implication of the results is for interpretation of the dose-response curve for radon and lung cancer in underground iron ore miners. Since exposure to radon and quartz is often correlated, quartz exposure can be an important confounder.

  15. [Compared with colloidal silica and porous silica as baicalin solid dispersion carrier].

    Science.gov (United States)

    Yan, Hong-Mei; Ding, Dong-Mei; Wang, Jing; Sun, E; Jia, Xiao-Bin; Zhang, Zhen-Hai

    2014-07-01

    To compare the dissolution characteristics of colloidal silica and porous silica as the solid dispersion carrier, with baicalin as the model drug. The baicalin solid dispersion was prepared by the solvent method, with colloidal silica and porous silica as the carriers. In the in vitro dissolution experiment, the solid dispersion was identified by scanning electron microscopy, differential scanning and X-ray diffraction. The solid dispersion carriers prepared with both colloidal silica and porous silica could achieve the purpose of rapid release. Along with the increase in the proportion of the carriers, the dissolution rate is accelerated to more than 80% within 60 min. Baicalin existed in the solid dispersion carriers in the non-crystalline form. The release behaviors of the baicalin solid dispersion prepared with two types of carrier were different. Among the two solid dispersion carriers, porous silica dissolved slowly than colloidal silica within 60 min, and they showed similar dissolutions after 60 min.

  16. Use of Fly Ash in the Mitigation of Alkali-Silica Reaction in Concrete

    Science.gov (United States)

    2010-11-12

    crystallinity of the silica and its solubility. Common reactive minerals susceptible to ASR include strained quartz, cristobalite , opal, obsidian, chert, and...residues, whereas alkali-silica reactive components include opal, cristobalite , tridymite, siliceous and some intermediate volcanic glass, chert

  17. Diesel and silica monitoring at two sites following hurricane sandy.

    Science.gov (United States)

    Freund, Alice; Zuckerman, Norman; Luo, Honghong; Hsu, Hsiao-Hsien; Lucchini, Roberto

    2014-01-01

    Following Hurricane Sandy, which hit New York City and New Jersey in October 2012, industrial hygienists from the Mount Sinai and Belleview/New York University occupational medicine clinics conducted monitoring for diesel exhaust and silica in lower Manhattan and Rockaway Peninsula. Average daytime elemental carbon levels at three stations in lower Manhattan on December 4, 2012, ranged from 9 to18 μg/m(3). Sub-micron particle counts at various times on the same day were over 200,000 particles per cubic centimeter on many streets in lower Manhattan. In Rockaway Peninsula on December 12, 2012, all average daytime elemental carbon levels were below a detection limit of approximately 7 μg/m(3). The average daytime crystalline silica dust concentration was below detection at two sites on Rockaway Peninsula, and was 0.015 mg/m(3) quartz where sand was being replaced on the beach. The daily average levels of elemental carbon and airborne particulates that we measured are in the range of levels that have been found to cause respiratory effects in sensitive subpopulations like asthmatic patients after 2 hr of exposure. Control of exposure to diesel exhaust must be considered following natural disasters where diesel-powered equipment is used in cleanup and recovery. Although peak silica exposures were not likely captured in this study, but were reported by a government agency to have exceeded recommended guidelines for at least one cleanup worker, we recommend further study of silica exposures when debris removal operations or traffic create visible levels of suspended dust from soil or sand.

  18. Importance of agglomeration state and exposure conditions for uptake and pro-inflammatory responses to amorphous silica nanoparticles in bronchial epithelial cells.

    Science.gov (United States)

    Gualtieri, Maurizio; Skuland, Tonje; Iversen, Tore-Geir; Låg, Marit; Schwarze, Per; Bilaničová, Dagmar; Pojana, Giulio; Refsnes, Magne

    2012-11-01

    Amorphous silica nanoparticles (SiNPs, 30 and 50 nm) and rhodamine-coated SiNPs (50 nm) were examined for their ability to induce pro-inflammatory responses and cytotoxicity in BEAS-2B cells under different experimental conditions. The SiNPs formed micrometre-sized agglomerates in the absence of bovine serum albumin (BSA) in the culture medium, whereas with BSA (0.1%) they were much less agglomerated. All the SiNPs induced IL-6 and IL-8 responses, as measured by ELISA and real-time PCR. The responses were more marked without BSA and higher for the rhodamine SiNPs than the plain ones. Rhodamine SiNPs were not taken up by cells during a 3-h exposure, even though cytokine mRNAs were up-regulated. In conclusion, agglomerated SiNPs induced more potent cytokine responses than the non-agglomerated ones; either due to the agglomeration state per se or more conceivably to a change in surface reactivity against cellular targets due to BSA. Furthermore, cytokine expression was up-regulated independently of SiNP uptake.

  19. Structural changes of silica mesocellular foam supported amine-functionalized CO2 adsorbents upon exposure to steam.

    Science.gov (United States)

    Li, Wen; Bollini, Praveen; Didas, Stephanie A; Choi, Sunho; Drese, Jeffrey H; Jones, Christopher W

    2010-11-01

    Three classes of amine-functionalized mesocellular foam (MCF) materials are prepared and evaluated as CO(2) adsorbents. The stability of the adsorbents under steam/air and steam/nitrogen conditions is investigated using a Parr autoclave reactor to simulate, in an accelerated manner, the exposure that such adsorbents will see under steam stripping regeneration conditions at various temperatures. The CO(2) capacity and organic content of all adsorbents decrease after steam treatment under both steam/air and steam/nitrogen conditions, primarily due to structural collapse of the MCF framework, but with additional contributions likely associated with amine degradation during treatment under harsh conditions. Treatment with steam/air is found to have stronger effect on the CO(2) capacity of the adsorbents compared to steam/nitrogen.

  20. Structural Changes of Silica Mesocellular Foam Supported Amine-Functionalized CO 2 Adsorbents Upon Exposure to Steam

    KAUST Repository

    Li, Wen

    2010-11-24

    Three classes of amine-functionalized mesocellular foam (MCF) materials are prepared and evaluated as CO2 adsorbents. The stability of the adsorbents under steam/air and steam/nitrogen conditions is investigated using a Parr autoclave reactor to simulate, in an accelerated manner, the exposure that such adsorbents will see under steam stripping regeneration conditions at various temperatures. The CO2 capacity and organic content of all adsorbents decrease after steam treatment under both steam/air and steam/nitrogen conditions, primarily due to structural collapse of the MCF framework, but with additional contributions likely associated with amine degradation during treatment under harsh conditions. Treatment with steam/air is found to have stronger effect on the CO2 capacity of the adsorbents compared to steam/nitrogen. © 2010 American Chemical Society.

  1. Bietti's Crystalline Dystrophy

    Science.gov (United States)

    ... Dystrophy > Facts About Bietti's Crystalline Dystrophy Facts About Bietti's Crystalline Dystrophy This information was developed by the ... is the best person to answer specific questions. Bietti’s Crystalline Dystrophy Defined What is Bietti’s Crystalline Dystrophy? ...

  2. Geology of quartz and hydrated silica-bearing deposits near Antoniadi Crater, Mars

    Science.gov (United States)

    Smith, Matthew R.; Bandfield, Joshua L.

    2012-06-01

    The only area on Mars where crystalline quartz has been identified from orbit is near Antoniadi Crater, on the northern edge of the Syrtis Major shield volcano. However, the method of quartz formation has remained unknown. In this study, we use high-resolution satellite imagery as well as thermal and near-infrared spectroscopy to construct a geologic history of these deposits and their local context. We find that the quartz-bearing deposits are consistently co-located with hydrated silica. This spatial coherence suggests that the quartz formed as a diagenetic product of amorphous silica, rather than as a primary igneous mineral. Diagenetic quartz is a mature alteration product of hydrated amorphous silica, and indicates more persistent water and/or higher temperatures at this site. Beneath the silica-bearing rocks, we also find spectral evidence for smectites in the lowermost exposed Noachian-aged breccia. A similar stratigraphic sequence — smectite-bearing breccias beneath deposits containing minerals suggesting a greater degree of alteration — has also been found at nearby exposures at Nili Fossae and Toro Crater, suggesting a widespread sequence of alteration. By merging the mineral detections of thermal infrared (quartz, feldspar) and near-infrared spectroscopy (hydrated silica, smectite clays) we are able to construct a more complete geologic history from orbit.

  3. Autoimmunity and Asbestos Exposure

    Directory of Open Access Journals (Sweden)

    Jean C. Pfau

    2014-01-01

    Full Text Available Despite a body of evidence supporting an association between asbestos exposure and autoantibodies indicative of systemic autoimmunity, such as antinuclear antibodies (ANA, a strong epidemiological link has never been made to specific autoimmune diseases. This is in contrast with another silicate dust, crystalline silica, for which there is considerable evidence linking exposure to diseases such as systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Instead, the asbestos literature is heavily focused on cancer, including mesothelioma and pulmonary carcinoma. Possible contributing factors to the absence of a stronger epidemiological association between asbestos and autoimmune disease include (a a lack of statistical power due to relatively small or diffuse exposure cohorts, (b exposure misclassification, (c latency of clinical disease, (d mild or subclinical entities that remain undetected or masked by other pathologies, or (e effects that are specific to certain fiber types, so that analyses on mixed exposures do not reach statistical significance. This review summarizes epidemiological, animal model, and in vitro data related to asbestos exposures and autoimmunity. These combined data help build toward a better understanding of the fiber-associated factors contributing to immune dysfunction that may raise the risk of autoimmunity and the possible contribution to asbestos-related pulmonary disease.

  4. A review of engineering control technology for exposures generated during abrasive blasting operations.

    Science.gov (United States)

    Flynn, Michael R; Susi, Pam

    2004-10-01

    This literature review presents information on measures for controlling worker exposure to toxic airborne contaminants generated during abrasive blasting operations occurring primarily in the construction industry. The exposures of concern include respirable crystalline silica, lead, chromates, and other toxic metals. Unfortunately, silica sand continues to be widely used in the United States as an abrasive blasting medium, resulting in high exposures to operators and surrounding personnel. Recently, several alternative abrasives have emerged as potential substitutes for sand, but they seem to be underused Some of these abrasives may pose additional metal exposure hazards. In addition, several new and improved technologies offer promise for reducing or eliminating exposures; these include wet abrasive blasting, high-pressure water jetting, vacuum blasting, and automated/robotic systems. More research, particularly field studies, is needed to evaluate control interventions in this important and hazardous operation.

  5. Vapour-phase crystallisation of silica from SiF4-bearing volcanic gases

    Directory of Open Access Journals (Sweden)

    M. H. G. Jacobs

    2005-06-01

    Full Text Available Thermodynamic modelling of magmatic gases shows that SiF4 may be an important F-bearing species at the high pressures typical of magma reservoirs. Upon decompression during degassing, SiF4 will react with water vapour to form HF and silica. Common magmatic gases of high-T fumaroles seem to contain too little SiF4 to be a significant source of silica, except if extremely large amounts of gas percolate through a small volume of rock, as is the case in lava domes. Only if fluorine contents of the gases exceed 1 mol% detectable amounts of silica may be formed, but such high fluorine contents have not yet been observed in natural gases. Alternatively, silica may be formed by heating of cool SiF4-rich gases circulating in cooling lava bodies. We suggest that these mechanisms may be responsible for the deposition of crystalline silica, most probably cristobalite, observed in vesicles in lavas from Lewotolo volcano (Eastern Sunda Arc, Indonesia. Silica occurs as vapour-crystallised patches in vesicles, and is sometimes associated with F-phlogopite, which further supports F-rich conditions during deposition. Because of the connection between F-rich conditions and high-K volcanism, we propose that late-stage gaseous transport and deposition of silica may be more widespread in K-rich volcanoes than elsewhere, and long-term exposure to ash from eruptions of such volcanoes could therefore carry an increased risk for respiratory diseases. The dependence of SiF4/HF on temperature reported here differs from the current calibration used for temperature measurements of fumarolic gases by remote sensing techniques, and we suggest an updated calibration.

  6. Crystalline Confinement

    CERN Document Server

    Banerjee, D; Jiang, F -J; Wiese, U -J

    2013-01-01

    We show that exotic phases arise in generalized lattice gauge theories known as quantum link models in which classical gauge fields are replaced by quantum operators. While these quantum models with discrete variables have a finite-dimensional Hilbert space per link, the continuous gauge symmetry is still exact. An efficient cluster algorithm is used to study these exotic phases. The $(2+1)$-d system is confining at zero temperature with a spontaneously broken translation symmetry. A crystalline phase exhibits confinement via multi-stranded strings between charge-anti-charge pairs. A phase transition between two distinct confined phases is weakly first order and has an emergent spontaneously broken approximate $SO(2)$ global symmetry. The low-energy physics is described by a $(2+1)$-d $\\mathbb{R}P(1)$ effective field theory, perturbed by a dangerously irrelevant $SO(2)$ breaking operator, which prevents the interpretation of the emergent pseudo-Goldstone boson as a dual photon. This model is an ideal candidat...

  7. Supra-amphiphilic transparent mesoporous silica coating

    Institute of Scientific and Technical Information of China (English)

    MA Jin; YANG Zhenglong; QU Xiaozhong; YANG Zhenzhong

    2006-01-01

    Transparent mesoporous silica coatings were achieved by conventional sol-gel process. The obtained coatings display permanent supraamphiphilicity, transparent appearance and good wetting property with very fast spread rate. Incorporation of functional materials such as crystalline titania nanoparticles into the coatings was also carried out without affecting the transparency and supraamphiphilicity.

  8. Índice de exposição à sílica na atividade de mineração de ouro Silica exposure index in gold mining

    Directory of Open Access Journals (Sweden)

    Ana Paula Scalia Carneiro

    2006-02-01

    Full Text Available OBJETIVO: Propor um índice que sintetize a exposição cumulativa à sílica, incluindo intensidade, duração e época da exposição e testá-lo em relação à presença e gravidade de silicose. MÉTODOS: Estudo transversal realizado com 140 ex-mineiros de ouro, residentes em duas localidades do Estado de Minas Gerais, examinados entre 11/1997 e 12/1999. Foram analisadas informações sobre história clínica e ocupacional, radiografia de tórax e espirometria. Casos borderline de silicose pela radiografia foram submetidos à tomografia computadorizada de alta resolução. O índice representa a soma dos escores extraídos da transformação logarítmica das taxas de concentração de sílica respirável nas diversas funções, minas e períodos trabalhados. Foram aplicados testes paramétricos para comparação das médias entre os grupos de interesse. RESULTADOS: O índice proposto apresentou-se discriminativo em relação ao desfecho principal (silicose e aos desfechos secundários (enfisema e tuberculose pulmonar no grupo total, incluindo os diversos estágios da doença, com valores p: 0,008, 0,016 e OBJECTIVE: To develop a cumulative silica exposure index, including time period, duration and intensity of exposure, and to test this index as for occurrence and severity of silicosis. METHODS: A cross-sectional study was carried out comprising 140 former gold miners from two localities in Southeastern Brazil between November 1997 and December 1999. Complete data on occupational and medical histories, chest x-rays and spirometry were analyzed. Borderline cases on the x-rays were also submitted to high-resolution chest computed tomography. The exposure index was the sum of scores obtained by logarithmic transformation of respirable silica concentration related to job tasks, mines and work time. Parametric tests were used for comparing averages between the groups of interest. RESULTS: The silica exposure index was able to discriminate the

  9. Dysregulation of autoimmunity caused by silica exposure and alteration of Fas-mediated apoptosis in T lymphocytes derived from silicosis patients.

    Science.gov (United States)

    Otsuki, T; Hayashi, H; Nishimura, Y; Hyodo, F; Maeda, M; Kumagai, N; Miura, Y; Kusaka, M; Uragami, K

    2011-01-01

    Silicosis patients suffer from pulmonary fibrosis caused by silica inhalation, as well as autoimmune diseases known as the adjuvant effects of silica. Caplan syndrome complicated with rheumatoid arthritis (RA) is well known epidemiologically, and the incidence of complicated systemic sclerosis (SSc), systemic lupus erythematosus (SLE) and antineutrophilic cytoplasmic antibody (ANCA)-related nephritis have been reported frequently in silicosis patients. To explore the detailed mechanisms of silica-induced dysregulation of autoimmunity, we had focused on Fas/CD95 and Fas-mediated apoptosis because Fas is one of the most important molecules regarding apoptosis of lymphocytes and its alteration makes some T cells survive longer. Additionally, if the long-survived T cells include the self-recognizing T-cell clones, it is easily thought that autoimmune diseases will appear in this situation. Furthermore, regulatory T cells (Treg) showing CD4+25+ and forkhead box P3 (FoxP3)-positive have been a central player in regulating activation of self- and foreign-antigen recognizing T cells, and it has been reported that activation of Treg causes its higher expression of Fas/CD95. Thus, in this review, we introduce the alteration of Fas and related molecules as found in silicosis and also present the Treg function of the CD4+25+ fraction in peripheral blood mononuclear cells derived from silicosis patients.

  10. Crystalline and Crystalline International Disposal Activities

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, Hari S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffrey De' Haven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-12-21

    This report presents the results of work conducted between September 2014 and July 2015 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program.

  11. The influence of glass composition on crystalline phase stability in glass-ceramic wasteforms

    Energy Technology Data Exchange (ETDEWEB)

    Maddrell, Ewan, E-mail: ewan.r.maddrell@nnl.co.uk [National Nuclear Laboratory, Sellafield, Seascale, Cumbria CA20 1PG (United Kingdom); Thornber, Stephanie; Hyatt, Neil C. [Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom)

    2015-01-15

    Highlights: • Crystalline phase formation shown to depend on glass matrix composition. • Zirconolite forms as the sole crystalline phase only for most aluminous glasses. • Thermodynamics indicate that low silica activity glasses stabilise zirconolite. - Abstract: Zirconolite glass-ceramic wasteforms were prepared using a suite of Na{sub 2}O–Al{sub 2}O{sub 3}–B{sub 2}O{sub 3}–SiO{sub 2} glass matrices with variable Al:B ratios. Zirconolite was the dominant crystalline phase only for the most alumina rich glass compositions. As the Al:B ratio decreased zirconolite was replaced by sphene, zircon and rutile. Thermodynamic data were used to calculate a silica activity in the glass melt below which zirconolite is the favoured crystalline phase. The concept of the crystalline reference state of glass melts is then utilised to provide a physical basis for why silica activity varies with the Al:B ratio.

  12. Aerosol-Assisted Synthesis of Monodisperse Single-Crystalline α-Cristobalite Nanospheres

    OpenAIRE

    Jiang, Xingmao; Bao, Lihong; Cheng, Yung-Sung; Dunphy, Darren R.; Li, Xiaodong; Brinker, C. Jeffrey

    2011-01-01

    Monodisperse single-crystalline α-cristobalite nanospheres have been synthesized by hydrocarbon-pyrolysis-induced carbon deposition on amorphous silica aerosol nanoparticles, devitrification of the coated silica at high temperature, and subsequent carbon removal by oxidation. The nanosphere size can be well controlled by tuning the size of the colloidal silica precursor. Uniform, high-purity nanocrystalline α-cristobalite is important for catalysis, nanocomposites, advanced polishing, and und...

  13. Silica and glomerulonephritis: case report and review of the literature

    Energy Technology Data Exchange (ETDEWEB)

    Osorio, A.M.; Thun, M.J.; Novak, R.F.; Van Cura, E.J.; Avner, E.D.

    1987-03-01

    A 54-year-old foundry worker with extensive silica exposure, but no pulmonary disease, developed the nephrotic syndrome and renal failure over a 3-month period. Renal biopsy demonstrated a proliferative glomerulonephritis; energy dispersive x-ray analysis detected silicon within the renal tubules. Measurements of respirable silica at the foundry revealed levels up to 2.5 times the current occupational standard. Similar glomerular disease has been reported in silica-exposed animals and workers with silicosis. This case suggests that clinicians should include silica exposure in the differential diagnosis of unexplained diffuse proliferative glomerulonephritis, renal disease may occur without clinically evident pulmonary disease in silica exposure, and silica-induced glomerulonephritis warrants further clinical and epidemiologic research.

  14. Exposure characterization for highway construction. Part I: Cut and cover and tunnel finish stages.

    Science.gov (United States)

    Blute, N A; Woskie, S R; Greenspan, C A

    1999-09-01

    The purpose of this study was to characterize respirable dust, crystalline silica, diesel, and noise exposures to construction workers on a large highway construction project in Boston, Massachusetts. The study primarily focused on operating engineers and laborers, and to a lesser extent on ironworkers and carpenters during the tunnel finish and cut and cover stages. Full and partial shift noise dosimeter measurements were collected. Eighty percent of the 40 noise measurements were at or above 85 dBA, with the operating engineers averaging 91 dBA. Sample collection for respirable dust, crystalline silica, and diesel particulates measured as elemental carbon was done using cyclones and personal cascade impactors. Exposure to respirable dust ranged from 0.06 to 21.77 mg/m3 for the 77 workers sampled, with the laborers having the highest mean concentration of 2.85 mg/m3. The respirable quartz measurements for the 32 samples collected ranged from the detection limit of 0.008 mg/m3 to 1.64 mg/m3, with the highest mean concentration of 0.31 mg/m3 attributed to the laborers. The use of drills, when compared to other machine types, produced the highest exposures to respirable quartz. The levels for elemental carbon ranged from 4 to 178 micrograms/m3 (mean of 41 micrograms/m3) inside enclosed work spaces, compared with 0.5 to 53 micrograms/m3 (mean of 10 micrograms/m3) for samples collected in unenclosed work sites. Statistical modeling of the factors influencing the elemental carbon exposures showed that machine type, worker distance from the diesel source, the number of other diesel sources in the work area, and site enclosure were all significant exposure determinants. The results indicate that high exposures to noise, respirable dust, and crystalline silica are common in the highway construction industry.

  15. Biomimetic silica encapsultation of living cells

    Science.gov (United States)

    Jaroch, David Benjamin

    Living cells perform complex chemical processes on size and time scales that artificial systems cannot match. Cells respond dynamically to their environment, acting as biological sensors, factories, and drug delivery devices. To facilitate the use of living systems in engineered constructs, we have developed several new approaches to create stable protective microenvironments by forming bioinspired cell-membrane-specific silica-based encapsulants. These include vapor phase deposition of silica gels, use of endogenous membrane proteins and polysaccharides as a site for silica nucleation and polycondensation in a saturated environment, and protein templated ordered silica shell formation. We demonstrate silica layer formation at the surface of pluripotent stem-like cells, bacterial biofilms, and primary murine and human pancreatic islets. Materials are characterized by AFM, SEM and EDS. Viability assays confirm cell survival, and metabolite flux measurements demonstrate normal function and no major diffusion limitations. Real time PCR mRNA analysis indicates encapsulated islets express normal levels of genetic markers for β-cells and insulin production. The silica glass encapsulant produces a secondary bone like calcium phosphate mineral layer upon exposure to media. Such bioactive materials can improve device integration with surrounding tissue upon implantation. Given the favorable insulin response, bioactivity, and long-term viability observed in silica-coated islets, we are currently testing the encapsulant's ability to prevent immune system recognition of foreign transplants for the treatment of diabetes. Such hybrid silica-cellular constructs have a wide range of industrial, environmental, and medical applications.

  16. Novel Crystalline SiO2 Nanoparticles via Annelids Bioprocessing of Agro-Industrial Wastes

    Science.gov (United States)

    Espíndola-Gonzalez, A.; Martínez-Hernández, A. L.; Angeles-Chávez, C.; Castaño, V. M.; Velasco-Santos, C.

    2010-09-01

    The synthesis of nanoparticles silica oxide from rice husk, sugar cane bagasse and coffee husk, by employing vermicompost with annelids ( Eisenia foetida) is reported. The product ( humus) is calcinated and extracted to recover the crystalline nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS) show that the biotransformation allows creating specific crystalline phases, since equivalent particles synthesized without biotransformation are bigger and with different crystalline structure.

  17. Novel Crystalline SiO2 Nanoparticles via Annelids Bioprocessing of Agro-Industrial Wastes

    Directory of Open Access Journals (Sweden)

    Angeles-Chávez C

    2010-01-01

    Full Text Available Abstract The synthesis of nanoparticles silica oxide from rice husk, sugar cane bagasse and coffee husk, by employing vermicompost with annelids (Eisenia foetida is reported. The product (humus is calcinated and extracted to recover the crystalline nanoparticles. X-ray diffraction (XRD, transmission electron microscopy (TEM, high-resolution transmission electron microscopy (HRTEM and dynamic light scattering (DLS show that the biotransformation allows creating specific crystalline phases, since equivalent particles synthesized without biotransformation are bigger and with different crystalline structure.

  18. Structure/Property Relationships of Poly(L-lactic Acid/Mesoporous Silica Nanocomposites

    Directory of Open Access Journals (Sweden)

    Javier Gudiño-Rivera

    2013-01-01

    Full Text Available Biodegradable poly(L-lactic acid (PLLA/mesoporous silica nanocomposites were prepared by grafting L-lactic acid oligomer onto silanol groups at the surface of mesoporous silica (SBA-15. The infrared results showed that the lactic acid oligomer was grafted onto the mesoporous silica. Surface characterization of mesoporous silica proved that the grafted oligomer blocked the entry of nitrogen into the mesopores. Thermal analysis measurements showed evidence that, once mixed with PLLA, SBA-15 not only nucleated the PLLA but also increased the total amount of crystallinity. Neat PLLA and its nanocomposites crystallized in the same crystal habit and, as expected, PLLA had a defined periodicity compared with the nanocomposites. This was because the grafted macromolecules on silica tended to cover the lamellar crystalline order. The g-SBA-15 nanoparticles improved the tensile moduli, increasing also the tensile strength of the resultant nanocomposites. Overall, the silica concentration tended to form a brittle material.

  19. Electron-beam irradiation effects on luminescence properties in subsurface regions of single-crystalline sapphires treated with and without hydrogen plasma exposures

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bo-Hyun [Department of Electrical Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)]. E-mail: bhlee@daiyan.eei.eng.osaka-u.ac.jp; Ito, Toshimichi [Department of Electrical Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)

    2007-10-15

    Electron irradiation effects on various insulating sapphires treated with and without hydrogen plasma have been investigated mainly by means of cathodoluminescence (CL) measurements. The samples examined included Be-diffusion-treated natural sapphire (BNS) and two types of synthetic sapphires grown by Verneuil and Czochralski methods. For all the samples examined, on one hand, their CL intensities of the F{sup +}-center-related emission peaked at {approx}3.8 eV rapidly increased with increasing the fluences of keV electrons, and were represented roughly by exponentially saturating curves. There occurred slight blue-shifts of the F{sup +}-center luminescence other than the intensity increases for some of the electron-irradiated specimens, suggesting possible presence of two components for the F{sup +}-center luminescence. On the other hand, a hydrogen plasma exposure to these sapphires resulted in sample-dependent changes in the optical property and in the beam-irradiation effect on the F{sup +}-center CL emission. Such variations were induced most strongly in the BNS sample, whose color changed from orange to pink due to substantial decreases in the absorbance after the hydrogen plasma treatment. Furthermore, the energy positions of both the Cr{sup 3+}-center luminescence peaked at {approx}1.8 eV and its satellite peaks were found to slightly shift for the untreated and H-plasma-treated BNS samples after the electron beam irradiations. Possible origins of these observations are discussed.

  20. Field Evaluation Of A Novel Exposure Assessment Strategy Using Respirable Coal Dust Exposures During Heat Plant Coal Receiving Operations

    Science.gov (United States)

    2009-03-01

    percentages of the three most common forms of crystalline silica to include quartz, cristobalite and tridymite. ®) threshold limit value (TLV®) booklet...0.025 mg/m3 (note that between 2005 and 2006 ACGIH® withdrew tridymite and tripoli, while combining quartz and cristobalite into one TLV®, i.e. Silica...carcinogen (ACGIH, 2008). In 2006, the ACGIH® combined quartz and cristobalite into a single TLV® TWA under the heading crystalline silica. As part of

  1. Crystalline and Crystalline International Disposal Activities

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, Hari S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, Timothy M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, Jeffrey De' Haven [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, Satish [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, Nataliia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-06

    This report presents the results of work conducted between September 2015 and July 2016 at Los Alamos National Laboratory in the crystalline disposal and crystalline international disposal work packages of the Used Fuel Disposition Campaign (UFDC) for DOE-NE’s Fuel Cycle Research and Development program. Los Alamos focused on two main activities during this period: Discrete fracture network (DFN) modeling to describe flow and radionuclide transport in complex fracture networks that are typical of crystalline rock environments, and a comprehensive interpretation of three different colloid-facilitated radionuclide transport experiments conducted in a fractured granodiorite at the Grimsel Test Site in Switzerland between 2002 and 2013. Chapter 1 presents the results of the DFN work and is divided into three main sections: (1) we show results of our recent study on the correlation between fracture size and fracture transmissivity (2) we present an analysis and visualization prototype using the concept of a flow topology graph for characterization of discrete fracture networks, and (3) we describe the Crystalline International work in support of the Swedish Task Force. Chapter 2 presents interpretation of the colloidfacilitated radionuclide transport experiments in the crystalline rock at the Grimsel Test Site.

  2. Multifunctional mesoporous silica catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Victor Shang-Yi; Tsai, Chih-Hsiang; Chen, Hung-Ting; Pruski, Marek; Kobayashi, Takeshi

    2015-03-31

    The present invention provides bifunctional silica mesoporous materials, including mesoporous silica nanoparticles ("MSN"), having pores modified with diarylammonium triflate and perfluoroaryl moieties, that are useful for the acid-catalyzed esterification of organic acids with organic alcohols.

  3. Iron(III)-doped, silica nanoshells: a biodegradable form of silica.

    Science.gov (United States)

    Pohaku Mitchell, Kristina K; Liberman, Alexander; Kummel, Andrew C; Trogler, William C

    2012-08-29

    Silica nanoparticles are being investigated for a number of medical applications; however, their use in vivo has been questioned because of the potential for bioaccumulation. To obviate this problem, silica nanoshells were tested for enhanced biodegradability by doping iron(III) into the nanoshells. Exposure of the doped silica to small molecule chelators and mammalian serum was explored to test whether the removal of iron(III) from the silica nanoshell structure would facilitate its degradation. Iron chelators, such as EDTA, desferrioxamine, and deferiprone, were found to cause the nanoshells to degrade on the removal of iron(III) within several days at 80 °C. When the iron(III)-doped, silica nanoshells were submerged in fetal bovine and human serums at physiological temperature, they also degrade via removal of the iron by serum proteins, such as transferrin, over a period of several weeks.

  4. Silica extraction from geothermal water

    Science.gov (United States)

    Bourcier, William L; Bruton, Carol J

    2014-09-23

    A method of producing silica from geothermal fluid containing low concentration of the silica of less than 275 ppm includes the steps of treating the geothermal fluid containing the silica by reverse osmosis treatment thereby producing a concentrated fluid containing the silica, seasoning the concentrated fluid thereby producing a slurry having precipitated colloids containing the silica, and separating the silica from the slurry.

  5. Silica, silicosis and cancer in Finland.

    Science.gov (United States)

    Partanen, T; Jaakkola, J; Tossavainen, A

    1995-01-01

    Approximately 100 000 Finnish workers are currently employed in jobs and tasks that may involve exposure to airborne silica dust. The major industries involved are mining and quarrying; production of glass, ceramics, bricks and other building materials; metal industry, particularly iron and steel founding; and construction. Over 1500 cases of silicosis have occurred in Finland since 1935. Tuberculosis has been a frequent complication of silicosis. Results of studies from several countries strongly suggest that silica dust also causes lung cancer. The results of the relevant Finnish epidemiologic and industrial hygiene studies addressing cancer risk and exposure to quartz dust are summarized.

  6. Crystalline boron nitride aerogels

    Science.gov (United States)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  7. Crystalline boron nitride aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  8. Silica-titania composite aerogel photocatalysts by chemical liquid deposition of titania onto nanoporous silica scaffolds.

    Science.gov (United States)

    Zu, Guoqing; Shen, Jun; Wang, Wenqin; Zou, Liping; Lian, Ya; Zhang, Zhihua

    2015-03-11

    Silica-titania composite aerogels were synthesized by chemical liquid deposition of titania onto nanoporous silica scaffolds. This novel deposition process was based on chemisorption of partially hydrolyzed titanium alkoxides from solution onto silica nanoparticle surfaces and subsequent hydrolysis and condensation to afford titania nanoparticles on the silica surface. The titania is homogeneously distributed in the silica-titania composite aerogels, and the titania content can be effectively controlled by regulating the deposition cycles. The resultant composite aerogel with 15 deposition cycles possessed a high specific surface area (SSA) of 425 m(2)/g, a small particle size of 5-14 nm, and a large pore volume and pore size of 2.41 cm(3)/g and 18.1 nm, respectively, after heat treatment at 600 °C and showed high photocatalytic activity in the photodegradation of methylene blue under UV-light irradiation. Its photocatalytic activity highly depends on the deposition cycles and heat treatment. The combination of small particle size, high SSA, and enhanced crystallinity after heat treatment at 600 °C contributes to the excellent photocatalytic property of the silica-titania composite aerogel. The higher SSAs compared to those of the reported titania aerogels (aerogels promising candidates as photocatalysts.

  9. Respiratory health effects in relation to crystalline silica

    CSIR Research Space (South Africa)

    Hnizdo, E

    1998-11-01

    Full Text Available The objective of the present study was to establish the feasibility of conducting such a prospective study of respiratory health effect in gold miners. In particular, the objectives were: (1) to establish whether routinely collected lung function...

  10. Mesoporous silica and organosilica films templated by nanocrystalline chitin.

    Science.gov (United States)

    Nguyen, Thanh-Dinh; Shopsowitz, Kevin E; MacLachlan, Mark J

    2013-11-04

    Liquid crystalline phases can be used to impart order into inorganic solids, creating materials that mimic natural architectures. Herein, mesoporous silica and organosilica films with layered structures and high surface areas have been templated by nanocrystalline chitin. Aqueous suspensions of spindle-shaped chitin nanocrystals were prepared by sequential deacetylation and hydrolysis of chitin fibrils isolated from king crab shells. The nanocrystalline chitin self-assembles into a nematic liquid-crystalline phase that has been used to template silica and organosilica composites. Removal of the chitin template by either calcination or sulfuric-acid-catalyzed hydrolysis gave mesoporous silica and ethylene-bridged organosilica films. The large, crack-free mesoporous films have layered structures with features that originate from the nematic organization of the nanocrystalline chitin.

  11. SILICA SURFACED CARBON FIBERS.

    Science.gov (United States)

    carbon fibers . Several economical and simple processes were developed for obtaining research quantities of silica surfaced carbon filaments. Vat dipping processes were utilized to deposit an oxide such as silica onto the surface and into the micropores of available carbon or graphite base fibers. High performance composite materials were prepared with the surface treated carbon fibers and various resin matrices. The ablative characteristics of these composites were very promising and exhibited fewer limitations than either silica or...treated

  12. SYNTHESIS OF ZEOLITE SOCONY MOBIL FROM BLUE SILICA GEL AND RICE HUSK ASH AS CATALYSTS FOR HYDROTHERMAL LIQUEFACTION

    OpenAIRE

    SUYITNO; SANURYA PUTRI PURBANINGRUM; DOMINICUS DANARDONO; ALFAITORY EMHEMED SALEM; FATHI A. MANSUR

    2015-01-01

    Renewable biofuels produced by the hydrothermal liquefaction of rice husks have received much attention because of rapid increases in fuel consumption and corresponding declines in fossil fuel resources. To increase biofuel yields, template-free syntheses of Zeolite Socony Mobil (ZSM) catalysts based on blue silica gel and rice husk ash as silica sources were studied. After ZSM synthesis in a closed reactor at 170°C, the crystallinity and crystalline diameters of the products were determined ...

  13. Silica in higher plants.

    Science.gov (United States)

    Sangster, A G; Hodson, M J

    1986-01-01

    Opaline silica deposits are formed by many vascular (higher) plants. The capacity of these plants for silica absorption varies considerably according to genotype and environment. Plant communities exchange silica between soil and vegetation, especially in warmer climates. Silica deposition in epidermal cell walls offers mechanical and protective advantages. Biogenic silica particles from plants are also implicated in the causation of cancer. Recent techniques are reviewed which may aid in the identification of plant pathways for soluble silica movement to deposition sites and in the determination of ionic environments. Botanical investigations have focused on silicification of cell walls in relation to plant development, using scanning and transmission electron microscopy combined with X-ray microanalysis. Silica deposition in macrohair walls of the lemma of canary grass (Phalaris) begins at inflorescence emergence and closely follows wall thickening. The structure of the deposited silica may be determined by specific organic polymers present at successive stages of wall development. Lowering of transpiration by enclosure of Phalaris inflorescences in plastic bags reduced silica deposition in macrohairs. Preliminary freeze-substitution studies have located silicon, as well as potassium and chloride, in the cell vacuole and wall deposition sites during initial silicification.

  14. The human crystallin gene families

    Directory of Open Access Journals (Sweden)

    Wistow Graeme

    2012-12-01

    Full Text Available Abstract Crystallins are the abundant, long-lived proteins of the eye lens. The major human crystallins belong to two different superfamilies: the small heat-shock proteins (α-crystallins and the βγ-crystallins. During evolution, other proteins have sometimes been recruited as crystallins to modify the properties of the lens. In the developing human lens, the enzyme betaine-homocysteine methyltransferase serves such a role. Evolutionary modification has also resulted in loss of expression of some human crystallin genes or of specific splice forms. Crystallin organization is essential for lens transparency and mutations; even minor changes to surface residues can cause cataract and loss of vision.

  15. Functionalization effects of single-walled carbon nanotubes as templates for the synthesis of silica nanorods and study of growing mechanism of silica.

    Science.gov (United States)

    Lee, Kyoung G; Wi, Rinbok; Imran, Muhammad; Park, Tae Jung; Lee, Jaebeom; Lee, Sang Yup; Kim, Do Hyun

    2010-07-27

    Silica nanorods were successfully prepared through a sol-gel process in the presence of carboxylic-functionalized single-walled carbon nanotubes (C-SWCNTs). The effect of chemical functionalization of single-walled carbon nanotubes (SWCNTs) on the growth of the silica layer was investigated using pristine SWCNTs (P-SWCNTs) and C-SWCNTS. The C-SWCNTs served as a unique template to fabricate silica hybrid composite materials. The crystalline formation and growing mechanism of the silica layer on C-SWCNTs were explained by the hydrolysis and chemical bonding between silica precursors and carboxylated SWCNTs. The C-SWCNTs, as templates, were successfully encapsulated using silica, and used templates were removed by oxidation at high temperature. Finally, silica nanorods/nanowires were synthesized in forms of mold, and this silica fabrication mechanism could be applied for large-scale production of silica nanomaterials and highly flexible nanocomposites. The sequence of a silica encapsulation process of C-SWCNTs and removed C-SWCNTs was characterized using SEM, TEM, EDX, FT-IR and Raman spectroscopy, XRD, and electrical analysis.

  16. Silica Refractory Bricks

    Institute of Scientific and Technical Information of China (English)

    Yu Lingyan; Peng Xigao

    2011-01-01

    @@ 1.Scope This standard specifies the classification,technical requirements,test methods,quality appraisal procedures,packing,marking,transportation,storage,and quality certificate of silica refractory bricks.This standard is applicable to silica refractory bricks with single weight≤40 kg.

  17. Preparation of spherical ceria coated silica nanoparticle abrasives for CMP application

    Energy Technology Data Exchange (ETDEWEB)

    Peedikakkandy, Lekha [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Powai, Mumbai 400076 (India); Kalita, Laksheswar [Advanced Technology Group, Applied Materials India Pvt. Ltd., Department of Electrical Engineering, IIT Bombay, Powai, Mumbai 400076 (India); Kavle, Pravin [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Powai, Mumbai 400076 (India); Kadam, Ankur; Gujar, Vikas; Arcot, Mahesh [Advanced Technology Group, Applied Materials India Pvt. Ltd., Department of Electrical Engineering, IIT Bombay, Powai, Mumbai 400076 (India); Bhargava, Parag, E-mail: pbhargava@iitb.ac.in [Department of Metallurgical Engineering and Materials Science, IIT Bombay, Powai, Mumbai 400076 (India)

    2015-12-01

    Highlights: • Nano-layer coating of ceria over silica nanoparticles. • Study effect of reaction pH and temperature on ceria coating over silica nanoparticles. • CMP application of ceria coated silica nanoparticles over SiO{sub 2} and SiN films. - Abstract: This paper describes synthesis of spherical and highly mono-dispersed ceria coated silica nanoparticles of size ∼70–80 nm for application as abrasive particles in Chemical Mechanical Planarization (CMP) process. Core silica nanoparticles were initially synthesized using micro-emulsion method. Ceria coating on these ultrafine and spherical silica nanoparticles was achieved using controlled chemical precipitation method. Study of various parameters influencing the formation of ceria coated silica nanoparticles of size less than 100 nm has been undertaken and reported. Ceria coating over silica nanoparticles was varied by controlling the reaction temperature, pH and precursor concentrations. Characterization studies using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Energy Dispersive X-ray analysis show formation of crystalline CeO{sub 2} coating of ∼10 nm thickness over silica with spherical morphology and particle size <100 nm. Aqueous slurry of ceria coated silica abrasive was prepared and employed for polishing of oxide and nitride films on silicon substrates. Polished films were studied using ellipsometry and an improvement in SiO{sub 2}:SiN selective removal rates up to 12 was observed using 1 wt% ceria coated silica nanoparticles slurry.

  18. Thermodynamics of Crystalline States

    CERN Document Server

    Fujimoto, Minoru

    2010-01-01

    Thermodynamics is a well-established discipline of physics for properties of matter in thermal equilibrium surroundings. Applying to crystals, however, the laws encounter undefined properties of crystal lattices, which therefore need to be determined for a clear and well-defined description of crystalline states. Thermodynamics of Crystalline States explores the roles played by order variables and dynamic lattices in crystals in a wholly new way. This book is divided into three parts. The book begins by clarifying basic concepts for stable crystals. Next, binary phase transitions are discussed to study collective motion of order variables, as described mostly as classical phenomena. In the third part, the multi-electron system is discussed theoretically, as a quantum-mechanical example, for the superconducting state in metallic crystals. Throughout the book, the role played by the lattice is emphasized and examined in-depth. Thermodynamics of Crystalline States is an introductory treatise and textbook on meso...

  19. Pulmonary toxicity of polyvinyl chloride particles after a single intratracheal instillation in rats. Time course and comparison with silica.

    Science.gov (United States)

    Xu, Haiyan; Verbeken, Erik; Vanhooren, Hadewijch M; Nemery, Benoit; Hoet, Peter H M

    2004-01-15

    Our previous in vitro studies indicated that emulsion polyvinyl chloride (PVC) particles (PVC-E3), with a mean diameter of 2 microm, exhibited a moderate toxicity in different pulmonary cell cultures. The in vitro cytotoxicity and pro-inflammatory potential of PVC-E3 particles were reduced when the additives had been "washed off" (PVC-W3), indicating that PVC-particle associated toxicity is probably related to the residual additives. In the present study, male Wistar rats (230 +/- 18 g) received a single intratracheal instillation of vehicle, crystalline silica particles [Min-U-Sil, 10 mg/kg body weight (BW)], PVC-E3 (10 or 50 mg/kg BW), or PVC-W3 (10 or 50 mg/kg BW). After 2, 7, 28, or 90 days, the rats were sacrificed (n = 6) and pulmonary injury and inflammation were determined by measuring lung weight, lactate dehydrogenase (LDH) activity and protein concentrations in bronchoalveolar lavage fluid (BALF), differential BALF cell count, and histopathology. Silica exposure resulted in pulmonary inflammation and damage at all time points with a progressive deterioration. Exposure to high concentrations of PVC particles caused pulmonary inflammation and damage, which were similar to the silica-exposed group at 2 days, but at 90 days, most parameters had returned to the control level, except for minor histopathological lesions. PVC-E3 did not induce more damage than PVC-W3. Two days after exposure, PVC-W3 caused less neutrophil but more eosinophil influx than PVC-E3. Although the pulmonary toxicity of both PVC-E3 and PVC-W3 appeared limited, this in vivo study has not confirmed the conclusion from the in vitro toxicity tests that removal of residual additives reduces the toxicity of PVC-E3 particles.

  20. Effect of silica forms in rice husk ash on the properties of concrete

    Science.gov (United States)

    Bui, Le Anh-Tuan; Chen, Chun-Tsun; Hwang, Chao-Lung; Wu, Wei-Sheng

    2012-03-01

    The strength and durability properties of concrete with or without three types of rice husk ash (RHA), namely, amorphous, partial crystalline, and crystalline RHA, were investigates. The three types of RHA were added into concrete at a 20% replacement level. Consequently, the pozzolanic reactivity of amorphous RHA was higher than that of partial crystalline and crystalline RHA. Concrete added with amorphous RHA showed excellent characteristics in its mechanical and durability properties. The results showed that the higher the amount of crystalline silica in RHA, the lower the concrete resistivity value became. When compared with each other, concretes with 20% of the cement replaced with these types of RHA achieved similar ultrasonic pulse velocity values, but all were lower than that of the control concrete. The incorporation of these kinds of RHA significantly reduced chloride penetration. The results not only encourage the use of amorphous materials, they also support the application of crystalline or partial crystalline RHA as mineral and pozzolanic admixtures for cement.

  1. Liquid crystalline dihydroazulene photoswitches

    DEFF Research Database (Denmark)

    Petersen, Anne Ugleholdt; Jevric, Martyn; Mandle, Richard J.

    2015-01-01

    A large selection of photochromic dihydroazulene (DHA) molecules incorporating various substituents at position 2 of the DHA core was prepared and investigated for their ability to form liquid crystalline phases. Incorporation of an octyloxy-substituted biphenyl substituent resulted in nematic...

  2. Dissolution-rate enhancement of fenofibrate by adsorption onto silica using supercritical carbon dioxide.

    Science.gov (United States)

    Sanganwar, Ganesh P; Gupta, Ram B

    2008-08-06

    Dissolution rate of a poorly water-soluble drug, fenofibrate, is increased by adsorbing the drug onto silica. The adsorption is achieved by first dissolving the drug in supercritical carbon dioxide and then depressurizing the solution onto silica. Loadings of up to 27.5 wt.% drug onto silica are obtained. Since solvents are not used in the loading process, the fenofibrate/silica formulation is free of any residual solvent, and carbon dioxide is freely removed upon depressurization. The formulation is characterized using infrared spectroscopy, ultraviolet spectroscopy, X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. Based on in vitro dissolution study, a significant increase in the dissolution rate (approximately 80% drug release in 20 min) of drug-silica formulation is observed as compared to micronized fenofibrate (approximately 20% drug release in 20 min), which can be attributed to increase in the surface area and decrease in the crystallinity of drug after adsorption onto silica. Two different formulations are compared: (A) amorphous fenofibrate/silica and (B) slightly crystalline fenofibrate/silica. The second formulation is found to be more stable on storage.

  3. Enhancement of Li+ ion conductivity in solid polymer electrolytes using surface tailored porous silica nanofillers

    Science.gov (United States)

    Mohanta, Jagdeep; Singh, Udai P.; Panda, Subhendu K.; Si, Satyabrata

    2016-09-01

    The current study represents the design and synthesis of polyethylene oxide (PEO)-based solid polymer electrolytes by solvent casting approach using surface tailored porous silica as nanofillers. The surface tailoring of porous silica nanostructure is achieved through silanization chemistry using 3-glycidyloxypropyl trimethoxysilane in which silane part get anchored to the silica surface whereas epoxy group get stellated from the silica surface. Surface tailoring of silica with epoxy group increases the room temperature electrochemical performances of the resulting polymer electrolytes. Ammonical hydrolysis of organosilicate precursor is used for both silica preparation and their surface tailoring. The composite solid polymer electrolyte films are prepared by solution mixing of PEO with lithium salt in presence of silica nanofillers and cast into film by solvent drying, which are then characterized by impedance measurement for conductivity study and wide angle x-ray diffraction for change in polymer crystallinity. Room temperature impedance measurement reveals Li+ ion conductivity in the order of 10-4 S cm-1, which is correlated to the decrease in PEO crystallinity. The enhancement of conductivity is further observed to be dependent on the amount of silica as well as on their surface characteristics.

  4. Synthesis, spectroscopy and catalysis of [Cr(acac)3] complexes grafted onto MCM-41 materials: formation of polyethylene nanofibres within mesoporous crystalline aluminosilicates

    NARCIS (Netherlands)

    Weckhuysen, B.M.; Ramachandra Rao, R.; Bodart, P.; Debras, G.; Collart, O.; Voort, P. van der; Schoonheydt, R.A.; Vansant, E.F.

    2000-01-01

    Chromium acetyl acetonate [Cr(acac)3] complexes have been grafted onto the surface of two mesoporous crystalline materials; pure silica MCM-41 (SiMCM-41) and Al-containing silica MCM-41 with an Si:Al ratio of 27 (AlMCM-41). The materials were characterized with X-ray diffraction, N2 adsorption, ther

  5. A new parameter-free soft-core potential for silica and its application to simulation of silica anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Izvekov, Sergei, E-mail: sergiy.izvyekov.civ@mail.mil; Rice, Betsy M. [Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

    2015-12-28

    A core-softening of the effective interaction between oxygen atoms in water and silica systems and its role in developing anomalous thermodynamic, transport, and structural properties have been extensively debated. For silica, the progress with addressing these issues has been hampered by a lack of effective interaction models with explicit core-softening. In this work, we present an extension of a two-body soft-core interatomic force field for silica recently reported by us [S. Izvekov and B. M. Rice, J. Chem. Phys. 136(13), 134508 (2012)] to include three-body forces. Similar to two-body interaction terms, the three-body terms are derived using parameter-free force-matching of the interactions from ab initio MD simulations of liquid silica. The derived shape of the O–Si–O three-body potential term affirms the existence of repulsion softening between oxygen atoms at short separations. The new model shows a good performance in simulating liquid, amorphous, and crystalline silica. By comparing the soft-core model and a similar model with the soft-core suppressed, we demonstrate that the topology reorganization within the local tetrahedral network and the O–O core-softening are two competitive mechanisms responsible for anomalous thermodynamic and kinetic behaviors observed in liquid and amorphous silica. The studied anomalies include the temperature of density maximum locus and anomalous diffusivity in liquid silica, and irreversible densification of amorphous silica. We show that the O–O core-softened interaction enhances the observed anomalies primarily through two mechanisms: facilitating the defect driven structural rearrangements of the silica tetrahedral network and modifying the tetrahedral ordering induced interactions toward multiple characteristic scales, the feature which underlies the thermodynamic anomalies.

  6. Silica Triggers Inflammation and Ectopic Lymphoid Neogenesis in the Lungs in Parallel with Accelerated Onset of Systemic Autoimmunity and Glomerulonephritis in the Lupus-Prone NZBWF1 Mouse

    Science.gov (United States)

    Bates, Melissa A.; Brandenberger, Christina; Langohr, Ingeborg; Kumagai, Kazuyoshi; Harkema, Jack R.; Holian, Andrij; Pestka, James J.

    2015-01-01

    Genetic predisposition and environmental factors influence the development of human autoimmune disease. Occupational exposure to crystalline silica (cSiO2) has been etiologically linked to increased incidence of autoimmunity, including systemic lupus erythematosus (SLE), but the underlying mechanisms are poorly understood. The purpose of this study was to test the hypothesis that early repeated short-term cSiO2 exposure will modulate both latency and severity of autoimmunity in the lupus-prone female NZBWF1 mouse. Weekly intranasal exposure to cSiO2 (0.25 and 1.0 mg) for 4 wk beginning at 9 wk of age both reduced latency and increased intensity of glomerulonephritis. cSiO2 elicited robust inflammatory responses in the lungs as evidenced by extensive perivascular and peribronchial lymphoplasmacytic infiltration consisting of IgG-producing plasma cells, and CD45R+ and CD3+ lymphocytes that were highly suggestive of ectopic lymphoid tissue (ELT). In addition, there were elevated concentrations of immunoglobulins and the cytokines MCP-1, TNF-α and IL-6 in bronchoalveolar lavage fluid. cSiO2-associated kidney and lung effects paralleled dose-dependent elevations of autoantibodies and proinflammatory cytokines in plasma. Taken together, cSiO2-induced pulmonary inflammation and ectopic lymphoid neogenesis in the NZBWF1 mouse corresponded closely to systemic inflammatory and autoimmune responses as well as the early initiation of pathological outcomes in the kidney. These findings suggest that following airway exposure to crystalline silica, in mice genetically prone to SLE, the lung serves as a platform for triggering systemic autoimmunity and glomerulonephritis. PMID:25978333

  7. Silica Triggers Inflammation and Ectopic Lymphoid Neogenesis in the Lungs in Parallel with Accelerated Onset of Systemic Autoimmunity and Glomerulonephritis in the Lupus-Prone NZBWF1 Mouse.

    Directory of Open Access Journals (Sweden)

    Melissa A Bates

    Full Text Available Genetic predisposition and environmental factors influence the development of human autoimmune disease. Occupational exposure to crystalline silica (cSiO2 has been etiologically linked to increased incidence of autoimmunity, including systemic lupus erythematosus (SLE, but the underlying mechanisms are poorly understood. The purpose of this study was to test the hypothesis that early repeated short-term cSiO2 exposure will modulate both latency and severity of autoimmunity in the lupus-prone female NZBWF1 mouse. Weekly intranasal exposure to cSiO2 (0.25 and 1.0 mg for 4 wk beginning at 9 wk of age both reduced latency and increased intensity of glomerulonephritis. cSiO2 elicited robust inflammatory responses in the lungs as evidenced by extensive perivascular and peribronchial lymphoplasmacytic infiltration consisting of IgG-producing plasma cells, and CD45R+ and CD3+ lymphocytes that were highly suggestive of ectopic lymphoid tissue (ELT. In addition, there were elevated concentrations of immunoglobulins and the cytokines MCP-1, TNF-α and IL-6 in bronchoalveolar lavage fluid. cSiO2-associated kidney and lung effects paralleled dose-dependent elevations of autoantibodies and proinflammatory cytokines in plasma. Taken together, cSiO2-induced pulmonary inflammation and ectopic lymphoid neogenesis in the NZBWF1 mouse corresponded closely to systemic inflammatory and autoimmune responses as well as the early initiation of pathological outcomes in the kidney. These findings suggest that following airway exposure to crystalline silica, in mice genetically prone to SLE, the lung serves as a platform for triggering systemic autoimmunity and glomerulonephritis.

  8. Plackett-Burman experimental design for bacterial cellulose-silica composites synthesis.

    Science.gov (United States)

    Guzun, Anicuta Stoica; Stroescu, Marta; Jinga, Sorin Ion; Voicu, Georgeta; Grumezescu, Alexandru Mihai; Holban, Alina Maria

    2014-09-01

    Bacterial cellulose-silica hybrid composites were prepared starting from wet bacterial cellulose (BC) membranes using Stöber reaction. The structure and surface morphology of hybrid composites were examined by FTIR and SEM. The SEM pictures revealed that the silica particles are attached to BC fibrils and are well dispersed in the BC matrix. The influence of silica particles upon BC crystallinity was studied using XRD analysis. Thermogravimetric (TG) analysis showed that the composites are stable up to 300°C. A Plackett-Burman design was applied in order to investigate the influence of process parameters upon silica particle sizes and silica content of BC-silica composites. The statistical model predicted that it is possible for silica particles size to vary the synthesis parameters in order to obtain silica particles deposed on BC membranes in the range from 34.5 to 500 nm, the significant parameters being ammonia concentration, reaction time and temperature. The silica content also varies depending on process parameters, the statistical model predicting that the most influential parameters are water-tetraethoxysilane (TEOS) ratio and reaction temperature. The antimicrobial behavior on Staphylococcus aureus of BC-silica composites functionalized with usnic acid (UA) was also studied, in order to create improved surfaces with antiadherence and anti-biofilm properties.

  9. Crystalline systems. [Book chapter

    Energy Technology Data Exchange (ETDEWEB)

    Kispert, L.D.

    The use of two double resonance methods, electron-nuclear double resonance (ENDOR) and electron-electron double resonance (ELDOR) in the study of free radicals in solids is reviewed. Included are descriptions of how crystalline-phase ENDOR is used to determine small hyperfine splittings, quadrupoly couplings, and reaction mechanisms or radical formation and how crystalline phase ELDOR is used to determine large hyperfine splittings, to identify radicals with large quadrupole moments and to study spin exchange processes. The complementary role played by the ENDOR and ELDOR spectroscopy in the separation of overlapping EPR spectra, in the study of proton-deuterium exchange, in the study of methyl groups undergoing tunneling rotation, and in the determination of the rates of intermolecular motion are dealt with. 13 figures, 1 table. (DP)

  10. Thermodynamics of Crystalline States

    CERN Document Server

    Fujimoto, Minoru

    2013-01-01

    Thermodynamics is a well-established discipline of physics for properties of matter in thermal equilibrium with the surroundings. Applying to crystals, however, the laws encounter undefined properties of crystal lattice, which therefore need to be determined for a clear and well-defined description of crystalline states. Thermodynamics of Crystalline States explores the roles played by order variables and dynamic lattices in crystals in a wholly new way. The book begins by clarifying basic concepts for stable crystals. Next, binary phase transitions are discussed to study collective motion of order variables, as described mostly as classical phenomena. New to this edition is the examination of magnetic crystals, where magnetic symmetry is essential for magnetic phase transitions. The multi-electron system is also discussed  theoretically, as a quantum-mechanical example, for superconductivity in metallic crystals. Throughout the book, the role played by the lattice is emphasized and studied in-depth. Thermod...

  11. Effect of Cristobalite on the Mechanical Properties of Silica RSI Materials

    Science.gov (United States)

    Khandelwal, P. K.; Scott, W. D.

    1973-01-01

    The strength of various silica surface insulation materials was measured after high temperature heat treatment to develop substantial crystalline phases, and after low temperature thermal cycling through the alpha-beta cristobalite transformation. It appears that the presence of cristobalite in the structural elements (the fibers) is highly detrimental to tensile strength. When crystallization does not occur in silica material, the strength improves with heat treatment.

  12. Polymer Morphology and Crystallinity close to Inorganic Surfaces

    Science.gov (United States)

    Chrissopoulou, Kiriaki; Papananou, Hellen; Anastasiadis, Spiros H.; Andrikopoulos, Konstantinos S.; Voyiatzis, George A.

    2015-03-01

    Polymer behavior close to surfaces or when restricted in space can be very different from that in the bulk. In this work, we investigate the morphology, crystallization and chain conformation of a hydrophilic, semi-crystalline polymer, poly(ethylene oxide), PEO, when mixed with silica, SiO2, nanoparticles in a broad range of compositions. The good dispersion of the nanoparticles was verified by Transmission Electron Microscopy (TEM), whereas the morphology and crystallization behaviour of the hybrids were investigated with, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). A gradual decrease of polymer crystallinity with increasing nanoparticles content is observed; nevertheless, polymer crystallization exists for all silica loadings. Moreover, DSC showed two melting and crystallization transitions in hybrids with polymer content lower than 50wt%, indicating that the polymer crystallizes differently than the bulk when it is in a thin interfacial layer near the silica surface. The existence of the two transitions are also evident in the IR and Raman spectra. Partially sponsored by EU (COST Action MP0902) and by the Greek GSRT (Research Funding Program: ARISTEIA II (SMART-SURF, project No. 3393, 2013SE01380048).

  13. Kinetics of silica polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Weres, O.; Yee, A.; Tsao, L.

    1980-05-01

    The polymerization of silicic acid in geothermal brine-like aqueous solutions to produce amorphous silica in colloidal form has been studied experimentally and theoretically. A large amount of high quality experimental data has been generated over the temperature rang 23 to 100{sup 0}C. Wide ranges of dissolved silica concentration, pH, and sodium chloride concentration were covered. The catalytic effects of fluoride and the reaction inhibiting effects of aluminum and boron were studied also. Two basic processes have been separately studied: the formation of new colloidal particles by the homogeneous nucleation process and the deposition of dissolved silica on pre-existing colloidal particles. A rigorous theory of the formation of colloidal particles of amorphous silica by homogeneous nucleation was developed. This theory employs the Lothe-Pound formalism, and is embodied in the computer code SILNUC which quantitatively models the homogeneous nucleation and growth of colloidal silica particles in more than enough detail for practical application. The theory and code were extensively used in planning the experimental work and analyzing the data produced. The code is now complete and running in its final form. It is capable of reproducing most of the experimental results to within experimental error. It is also capable of extrapolation to experimentally inaccessible conditions, i.e., high temperatures, rapidly varying temperature and pH, etc.

  14. Oxygen plasma etching-induced crystalline lattice transformation of colloidal photonic crystals.

    Science.gov (United States)

    Ding, Tao; Wang, Fei; Song, Kai; Yang, Guoqiang; Tung, Chen-Ho

    2010-12-15

    This communication describes the transformation of a colloidal crystalline lattice that was realized via oxygen plasma etching of colloidal crystals made of SiO2@PMMA core-shell microspheres. The plasma etching of the colloidal crystals proceeded nonuniformly from the top to the bottom of the colloidal crystals. The PMMA shell was etched away by the oxygen plasma in a layer-by-layer manner, and the silica core was drawn into the pit formed by the neighboring spheres in the layer below. Consequently, the crystalline lattice was transformed while the order was maintained. Scanning electron microscopy images and reflection spectra further confirmed the change in the crystalline structures. Colloidal crystals with sc and bcc lattices can be fabricated if the ratio of the polymer shell thickness to the silica core diameter is equal to certain values. More importantly, this approach may be applicable to the fabrication of various assembly structures with different inorganic particles.

  15. Characterisation of silica derived from rice husk (Muar, Johor, Malaysia) decomposition at different temperatures

    Science.gov (United States)

    Azmi, M. A.; Ismail, N. A. A.; Rizamarhaiza, M.; W. M. Hasif. A. A., K.; Taib, H.

    2016-07-01

    Rice husk was thermally decomposed to yield powder composed of silica (SiO2). Temperatures of 700°C and 1000°C were chosen as the decomposition temperatures. X-Ray Diffraction (XRD), X-Ray Florescence (XRF), Fourier Transform Infrared (FTIR), and Field Emission Scanning Electron Microscope (FESEM) analyses were conducted on a synthetic silica powder (SS-SiO2) and the rice husk ash as for the comparative characterisation study. XRD analyses clearly indicated that the decomposed rice husk yielded silica of different nature which are Crystalline Rice Husk Silica (C-RHSiO2) and Amorphous Rice Husk Silica (A-RHSiO2). Moreover, it was found that SS-SiO2 was of Quartz phase, C-RHSiO2 was of Trydimite and Cristobalite. Through XRF detection, the highest SiO2 purity was detected in SS-SiO2 followed by C-RHSiO2 and A-RHSiO2 with purity percentages of 99.60%, 82.30% and 86.30% respectively. FTIR results clearly indicated silica (SiO2) bonding 1056, 1064, 1047, 777, 790 and 798 cm-1) increased as the crystallinity silica increased. The Cristobalite phase was detected in C-RH SiO2 at the wavelength of 620 cm-1. Morphological features as observed by FESEM analyses confirmed that, SS-SiO2 and C-RH SiO2 showed prominent coarse granular morphology.

  16. Hydrophobic silica nanoparticles as reinforcing filler for poly (lactic acid polymer matrix

    Directory of Open Access Journals (Sweden)

    Pilić Branka M.

    2016-01-01

    Full Text Available Properties of poly (lactic acid (PLA and its nanocomposites, with silica nanoparticles (SiO2, as filler were investigated. Neat PLA films and PLA films with different percentage of hydrophobic fumed silica nanoparticles (0.2, 0.5, 1, 2, 3 and 5 wt. % were prepared by solution casting method. Several tools were used to characterize the influence of different silica content on crystalline behavior, and thermal, mechanical and barrier properties of PLA/SiO2 nanocomposites. Results from scanning electron microscope (SEM showed that the nanocomposite preparation and selection of specific hydrophobic spherical nano filler provide a good dispersion of the silica nanoparticles in the PLA matrix. Addition of silica nanoparticles improved mechanical properties, the most significant improvement being observed for lowest silica content (0.2wt.%. Barrier properties were improved for all measured gases at all loadings of silica nanoparticles. The degree of crystallinity for PLA slightly increased by adding 0.2 and 0.5 wt. % of nano filler. [Projekat Ministarstva nauke Republike Srbije, br. III46001

  17. Fractals of Silica Aggregates

    Institute of Scientific and Technical Information of China (English)

    ZhinhongLi; DongWu; Yuhansun; JunWang; YiLiu; BaozhongDong; Zhinhong

    2001-01-01

    Silica aggregates were prepared by base-catalyzed hydrolysis and condensation of alkoxides in alcohol.Polyethylene glycol(PEG) was used as organic modifier.The sols were characterized using Small Angle X-ray Scattering (SAXS) with synchrotron radiation as X-ray source.The structure evolution during the sol-gel process was determined and described in terms of the fractal geometry.As-produced silica aggregates were found to be mass fractals.The fractl dimensions spanned the regime 2.1-2.6 corresponding to more branched and compact structures.Both RLCA and Eden models dominated the kinetic growth under base-catalyzed condition.

  18. Silica reinforced triblock copolymer gels

    DEFF Research Database (Denmark)

    Theunissen, E.; Overbergh, N.; Reynaers, H.

    2004-01-01

    The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order...... a viscoclastic rubber to a plastic fluid and from a plastic fluid to a viscoelastic liquid are shifted to more elevated temperatures when silica is added to the triblock copolymer gel. (C) 2004 Elsevier Ltd. All rights reserved....

  19. Development of ultrafine and pure amorphous and crystalline new materials and their fabrication process

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Myung Seung; Kim, Y. E.; Kim, J. G.; Gu, J. H. [Korea Atomic Energy Research Inst., Taejon (Korea, Republic of); Yoon, N. K.; Seong, S. Y. [Myongseong Ceramics Co., Taejon (Korea, Republic of); Ryu, S. E. [Paichai Univ., Taejon (Korea, Republic of); Lee, J. C. [Myongji Univ., Taejon (Korea, Republic of)

    1996-07-01

    Based on an estimation of annual rice production of 5.2 Million tons, rice husks by-production reaches to 1.17 Million tons per year in Korea. distinguished to other corns, rice contains a lot of Si; 10 {approx} 20 % by weight in rice husks calculated as silica. The aim of this research project is to develop technologies for ceramic powders and materials utilizing the silica in rice husks called phytoliths. In this researches of the following subjects were performed; decomposition of the organic components, acid treatments, extraction of the organic matter, effect of gamma-ray irradiation on the acid treatment, plasma treatment, crystallization of silica powder, dispersion of amorphous silica powder, fabrication of ultrafine crystalline fibrous materials.. (author). 18 refs., 5 tabs., 55 figs.

  20. Confinement Effects for Lithium Borohydride: Comparing Silica and Carbon Scaffolds.

    Science.gov (United States)

    Suwarno; Ngene, Peter; Nale, Angeloclaudio; Eggenhuisen, Tamara M; Oschatz, Martin; Embs, Jan Peter; Remhof, Arndt; de Jongh, Petra E

    2017-03-02

    LiBH4 is a promising material for hydrogen storage and as a solid-state electrolyte for Li ion batteries. Confining LiBH4 in porous scaffolds improves its hydrogen desorption kinetics, reversibility, and Li(+) conductivity, but little is known about the influence of the chemical nature of the scaffold. Here, quasielastic neutron scattering and calorimetric measurements were used to study support effects for LiBH4 confined in nanoporous silica and carbon scaffolds. Pore radii were varied from 8 Å to 20 nm, with increasing confinement effects observed with decreasing pore size. For similar pore sizes, the confinement effects were more pronounced for silica than for carbon scaffolds. The shift in the solid-solid phase transition temperature is much larger in silica than in carbon scaffolds with similar pore sizes. A LiBH4 layer near the pore walls shows profoundly different phase behavior than crystalline LiBH4. This layer thickness was 1.94 ± 0.13 nm for the silica and 1.41 ± 0.16 nm for the carbon scaffolds. Quasi-elastic neutron scattering confirmed that the fraction of LiBH4 with high hydrogen mobility is larger for the silica than for the carbon nanoscaffold. These results clearly show that in addition to the pore size the chemical nature of the scaffold also plays a significant role in determining the hydrogen mobility and interfacial layer thickness in nanoconfined metal hydrides.

  1. Confinement Effects for Lithium Borohydride: Comparing Silica and Carbon Scaffolds

    Science.gov (United States)

    2017-01-01

    LiBH4 is a promising material for hydrogen storage and as a solid-state electrolyte for Li ion batteries. Confining LiBH4 in porous scaffolds improves its hydrogen desorption kinetics, reversibility, and Li+ conductivity, but little is known about the influence of the chemical nature of the scaffold. Here, quasielastic neutron scattering and calorimetric measurements were used to study support effects for LiBH4 confined in nanoporous silica and carbon scaffolds. Pore radii were varied from 8 Å to 20 nm, with increasing confinement effects observed with decreasing pore size. For similar pore sizes, the confinement effects were more pronounced for silica than for carbon scaffolds. The shift in the solid–solid phase transition temperature is much larger in silica than in carbon scaffolds with similar pore sizes. A LiBH4 layer near the pore walls shows profoundly different phase behavior than crystalline LiBH4. This layer thickness was 1.94 ± 0.13 nm for the silica and 1.41 ± 0.16 nm for the carbon scaffolds. Quasi-elastic neutron scattering confirmed that the fraction of LiBH4 with high hydrogen mobility is larger for the silica than for the carbon nanoscaffold. These results clearly show that in addition to the pore size the chemical nature of the scaffold also plays a significant role in determining the hydrogen mobility and interfacial layer thickness in nanoconfined metal hydrides. PMID:28286596

  2. Liquid crystalline order in polymers

    CERN Document Server

    Blumstein, Alexandre

    1978-01-01

    Liquid Crystalline Order in Polymers examines the topic of liquid crystalline order in systems containing rigid synthetic macromolecular chains. Each chapter of the book provides a review of one important area of the field. Chapter 1 discusses scattering in polymer systems with liquid crystalline order. It also introduces the field of liquid crystals. Chapter 2 treats the origin of liquid crystalline order in macromolecules by describing the in-depth study of conformation of such macromolecules in their unassociated state. The chapters that follow describe successively the liquid crystalli

  3. Exposure Assessment Suggests Exposure to Lung Cancer Carcinogens in a Painter Working in an Automobile Bumper Shop

    Directory of Open Access Journals (Sweden)

    Boowook Kim

    2013-12-01

    Full Text Available A 46-year-old man who had worked as a bumper spray painter in an automobile body shop for 15 years developed lung cancer. The patient was a nonsmoker with no family history of lung cancer. To determine whether the cancer was related to his work environment, we assessed the level of exposure to carcinogens during spray painting, sanding, and heat treatment. The results showed that spray painting with yellow paint increased the concentration of hexavalent chromium in the air to as much as 118.33 μg/m3. Analysis of the paint bulk materials showed that hexavalent chromium was mostly found in the form of lead chromate. Interestingly, strontium chromate was also detected, and the concentration of strontium chromate increased in line with the brightness of the yellow color. Some paints contained about 1% crystalline silica in the form of quartz.

  4. Thin supported silica membranes

    NARCIS (Netherlands)

    Zivkovic, Tijana

    2007-01-01

    This thesis discusses several transport-related aspects relevant for the application of thin supported silica membranes for gas separation and nanofiltration. The influence of support geometry on overall membrane performance is investigated. Planar (i.e., flat plate), tubular, and multichannel suppo

  5. [Silicosis hazard of silica dusts in diamond mining industry (experimental study)].

    Science.gov (United States)

    Mironova, G E; Bezrukavnikova, L M; Kuz'mina, L P

    2001-01-01

    Slow progressing experimental coniosis was induced by exposure to two samples of silica dust that was obtained from diamond openwork in "Mir" quarry of Yakutia. Moderate fibrogenicity of the dusts studied results from relatively low portions of silica and from metals oxides admixtures.

  6. Novel Crystalline SiO2 Nanoparticles via Annelids Bioprocessing of Agro-Industrial Wastes

    OpenAIRE

    Angeles-Chávez C; Martínez-Hernández AL; Velasco-Santos C.; Espíndola-Gonzalez A; Castaño VM

    2010-01-01

    Abstract The synthesis of nanoparticles silica oxide from rice husk, sugar cane bagasse and coffee husk, by employing vermicompost with annelids (Eisenia foetida) is reported. The product (humus) is calcinated and extracted to recover the crystalline nanoparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS) show that the biotransformation allows creating specific crystalline phase...

  7. Silica-induced NLRP3 inflammasome activation in vitro and in rat lungs

    NARCIS (Netherlands)

    Peeters, P.M.; Eurlings, I.M.J.; Perkins, T.N.; Wouters, E.F.; Schins, R.P.F.; Borm, P.J.A.; Drommer, W.; Reynaert, N.L.; Albrecht, C.

    2014-01-01

    RationaleMineral particles in the lung cause inflammation and silicosis. In myeloid and bronchial epithelial cells the inflammasome plays a role in responses to crystalline silica. Thioredoxin (TRX) and its inhibitory protein TRX-interacting protein link oxidative stress with inflammasome activation

  8. Artificial microfossils - Experimental studies of permineralization of blue-green algae in silica.

    Science.gov (United States)

    Oehler, J. H.; Schopf, J. W.

    1971-01-01

    A technique has been developed to artificially fossilize microscopic algae in crystalline silica under conditions of moderately elevated temperature and pressure. The technique is designed to simulate geochemical processes thought to have resulted in the preservation of organic microfossils in Precambrian bedded cherts. In degree of preservation and mineralogic setting, the artificially permineralized microorganisms are comparable to naturally occurring fossil algae.

  9. Perylene-labeled silica nanoparticles: synthesis and characterization of three novel silica nanoparticle species for live-cell imaging.

    Science.gov (United States)

    Blechinger, Julia; Herrmann, Rudolf; Kiener, Daniel; García-García, F Javier; Scheu, Christina; Reller, Armin; Bräuchle, Christoph

    2010-11-05

    The increasing exposure of humans to nanoscaled particles requires well-defined systems that enable the investigation of the toxicity of nanoparticles on the cellular level. To facilitate this, surface-labeled silica nanoparticles, nanoparticles with a labeled core and a silica shell, and a labeled nanoparticle network-all designed for live-cell imaging-are synthesized. The nanoparticles are functionalized with perylene derivatives. For this purpose, two different perylene species containing one or two reactive silica functionalities are prepared. The nanoparticles are studied by transmission electron microscopy, widefield and confocal fluorescence microscopy, as well as by fluorescence spectroscopy in combination with fluorescence anisotropy, in order to characterize the size and morphology of the nanoparticles and to prove the success and homogeneity of the labeling. Using spinning-disc confocal measurements, silica nanoparticles are demonstrated to be taken up by HeLa cells, and they are clearly detectable inside the cytoplasm of the cells.

  10. Total and respirable dust exposures among carpenters and demolition workers during indoor work in Denmark

    DEFF Research Database (Denmark)

    Kirkeskov, Lilli; Hanskov, Dorte Jessing Agerby; Brauer, Charlotte

    2016-01-01

    or the variation between the different work tasks. The purpose of this study was therefore to assess if there were differences in dust exposure between carpenters and demolition workers who were expected to have low and high dust exposure, respectively. METHODS: Through interviews of key persons...... out for carpenters and 20 measurements of total dust, 11 of respirable dust and 11 of respirable crystalline silica dust on four different works tasks for demolition workers. Dust measurements were tested for differences using linear regression, t-test and one-way ANOVA. RESULTS: For carpenters...... deviation 11.6) and the respirable dust was 1.06 mg/m(3) (geometric standard deviation 5.64). The mean difference between total dust for demolition workers and carpenters was 11.4 (95 % confidence interval 3.46-37.1) mg/m(3). The mean difference between respirable dust for demolition workers and carpenters...

  11. Liquid Crystalline Compositions as Gas Sensors

    Science.gov (United States)

    Shibaev, Petr; Murray, John; Tantillo, Anthony; Wenzlick, Madison; Howard-Jennings, Jordan

    2015-03-01

    Droplets and films of nematic and cholesteric liquid crystalline mixtures were studied as promising detectors of volatile organic compounds (VOCs) in the air. Under increasing concentration of VOC in the air the detection may rely on each of the following effects sequentially observed one after the other due to the diffusion of VOC inside liquid crystalline matrix: i. slight changes in orientation and order parameter of liquid crystal, ii. formation of bubbles on the top of the liquid crystalline droplet due to the mass transfer between the areas with different order parameter, iii. complete isotropisation of the liquid crystal. All three stages can be easily monitored by optical microscopy and photo camera. Detection limits corresponding to the first stage are typically lower by a factor of 3-6 than detection limits corresponding to the beginning of mass transfer and isotropisation. The prototype of a compact sensor sensitive to the presence of organic solvents in the air is described in detail. The detection limits of the sensor is significantly lower than VOC exposure standards. The qualitative model is presented to account for the observed changes related to the diffusion, changes of order parameter and isotropisation.

  12. COLD DRAWING IN CRYSTALLINE POLYMERS

    Science.gov (United States)

    alcohols, phenol) in Nylon 6 produced changes in the crystalline structure as well as plasticizer action; these two effects must therefore be carefully...distinguished. Changes in the crystalline structure were followed by changes in the infrared spectrum. Dynamic mechanical and thermogravimetric analysis

  13. Formation of silica iron oxide glasses

    Science.gov (United States)

    Al-Bawab, Abeer F.

    The microemulsion-gel method was developed as an alternative process in the production of room temperature glasses. This method is based on the formation of a microemulsion, to which is added a metal alkoxide that undergoes hydrolysis and condensation to form an oxide network, which is dried into glass. The goal of this work is to understand the sol-gel process upon addition of hydrate metal salts. The thermal transitions of the silica containing ferric nitrate hydrate were examined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Using infrared (IR) spectroscopy and X-ray diffraction (XRD). The glasses with a less than 30 mol % iron nitrate were amorphous, while those higher concentration were crystalline. Based on XRD the thermal transitions did not alter the crystallinity. The IR spectra indicated the existence of Si-O-Fe bonds. Thermal analysis indicated similar transitions as exhibited by pure iron nitrate with minor modifications due to interactions with the silica. The reaction between tetraethoxysilane and chloral hydrate in ethanol was followed by NMR of the sp{29}Si nucleus at two different pHs. The sp{29}Si NMR spectra were similar to those reported for the reactions in alcohol between tetraethoxysilane and water of low pH, and for the reactions in the presence of inorganic hydrate. At pH 4, monomene silicon species were detected where at pH 2 the reaction was sufficiently rapid that multi hydroxy monomers were not detected as expected from the catalysts. The reaction proceeded without adding water. The reaction between aluminum chloride and methoxydimethyloctylsilane was investigated at room temperature using NMR and IR spectroscopy in addition to a molecular weight determination from the freezing point reduction in benzene. The structure as deduced from the experimental results was found to be a dimer containing two silicon atoms and two aluminum atoms of which the latter were tetrahedrally coordinated.

  14. Crystalline Bioceramic Materials

    Directory of Open Access Journals (Sweden)

    de Aza, P. N.

    2005-06-01

    Full Text Available A strong interest in the use of ceramics for biomedical engineering applications developed in the late 1960´s. Used initially as alternatives to metallic materials in order to increase the biocompatibility of implants, bioceramics have become a diverse class of biomaterials, presently including three basic types: relatively bioinert ceramics; bioactive or surface reactive bioceramics and bioresorbable ceramics. This review will only refer to bioceramics “sensus stricto”, it is to say, those ceramic materials constituted for nonmetallic inorganic compounds, crystallines and consolidated by thermal treatments of powders to high temperatures. Leaving bioglasses, glass-ceramics and biocements apart, since, although all of them are obtained by thermal treatments to high temperatures, the first are amorphous, the second are obtained by desvitrification of a glass and in them vitreous phase normally prevails on the crystalline phases and the third are consolidated by means of a hydraulic or chemical reaction to room temperature. A review of the composition, physiochemical properties and biological behaviour of the principal types of crystalline bioceramics is given, based on the literature data and on the own experience of the authors.

    A finales de los años sesenta se despertó un gran interés por el uso de los materiales cerámicos para aplicaciones biomédicas. Inicialmente utilizados como una alternativa a los materiales metálicos, con el propósito de incrementar la biocompatibilidad de los implantes, las biocerámicas se han convertido en una clase diversa de biomateriales, incluyendo actualmente tres tipos: cerámicas cuasi inertes; cerámicas bioactivas o reactivas superficialmente y cerámicas reabsorbibles o biodegradables. En la presente revisión se hace referencia a las biocerámicas en sentido estricto, es decir, a aquellos materiales constitutitos por compuestos inorgánicos no metálicos, cristalinos y consolidados

  15. Oxidative cracking of n-butane over various silica packings; Kakushu shirika sonzaika deno n-butan no sanka bunkai hanno

    Energy Technology Data Exchange (ETDEWEB)

    Wakui, K.; Sato, K.; Sawada, G.; Shiozawa, K.; Matano, K. [Japan chemical Industry Association, Tokyo (Japan); Suzuki, K.; Hayakawa, T.; Murata, K.; Yoshimura, Y.; Mizukami, F. [National Institute of Materials and Chemical Research, Ibaraki (Japan)

    2000-07-01

    In order to study the difference between catalytic and non-catalytic oxidative cracking of n-butane, the oxidative cracking over carious silica was investigated in the temperature range of 600-700 degree C. The reactions were conducted with molecular oxygen, nitrogen, and n-butane using a fixed bed reactor loaded with various silica packings. Homogeneous radical reaction in the gas phase proceeded farther in an empty silica tube reactor and the highest conversion of n-butane was attained. With the loading of various silica packings, the conversion of n-butane was lowered; however, the conversion obtained using amorphous silica was quite different from that obtained using crystalline silica such as quartz sand or silicalite. The radical reaction was not suppressed so much by amorphous silica packing as by crystalline silica packing, and the n-butane conversion was as high as that in the empty tube reactor without silica packing. It was considered that the surface OH groups on the amorphous silica are involved in the radical chain reactions of the oxidative cracking. Ethylene, propylene, and butanes were obtained as major products and the selectivity of light olefins was high (700 degree C, about 75 % at 45 % conversion) compared with that obtained using other oxides. (author)

  16. Development of empirical potentials for amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Carre, A.

    2007-09-15

    potential shows a better agreement with the CP data than the BKS ones: pair correlation functions, angular distribution functions, structure factors, density of states and pressure/density were improved. At low temperature, the diffusion coefficients appear to be three times higher than those predicted by the BKS model, however showing a similar temperature dependence. Calculations have also been carried out on crystalline samples in order to check the transferability of the potential. The equilibrium geometry as well as the elastic constants of {alpha}-quartz at 0 K are well described by our new potential although the crystalline phases have not been considered for the parameterization. We have developed a new potential for silica which represents an improvement over the pair potentials class proposed so far. Furthermore, the fitting methodology that has been developed in this work can be applied to other network forming systems such as germania as well as mixtures of SiO{sub 2} with other oxides (e.g. Al{sub 2}O{sub 3}, K{sub 2}O, Na{sub 2}O). (orig.)

  17. Trimming Behavior of H_2-Loaded Silica Fiber Modeled by Rate Equations

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Photosensitivity behavior of H2-loaded silica fiber was modeled by rate equations for activated particles. The theoretical deductions give a close explanation to experimental phenomena on post-exposure growth in fiber gratings.

  18. ELASTIC PROPERTIES OF SILICA POLYMORPHS – A REVIEW

    Directory of Open Access Journals (Sweden)

    Pabst W.

    2013-09-01

    Full Text Available The elastic properties of silica phases are reviewed. Available monocrystal data for crystalline SiO2 polymorphs (low-quartz, high-quartz, low-cristobalite, high-cristobalite, stishovite are collected from the literature, and effective elastic constants (Young’s moduli, shear moduli, bulk moduli and Poisson ratios are calculated from these using Voigt-Reuss-Hill averaging. Both experimental data and simulation results are taken into account. A table of room temperature elastic constants for crystalline silica polymorphs and silica glass is given that lists the recommended current “state-of-the-art“ values. All data are consistent with the well-known auxetic behavior of cristobalite at room temperature, and high-temperature simulation data published for cristobalite confirm auxetic behavior for all temperatures from room temperature up to more than 1500°C. The calculations of this paper show that also quartz can be auxetic, but only in a very limited temperature range around the low-to-high-quartz transition temperature (420 – 577°C. Experimental measurements of elastic properties of tridymite and cristobalite, including high-temperature measurements, are identified as a desideratum of future research.

  19. Aniline incorporated silica nanobubbles

    Indian Academy of Sciences (India)

    M J Rosemary; V Suryanarayanan; Ian Maclaren; T Pradeep

    2006-09-01

    We report the synthesis of stearate functionalized nanobubbles of SiO2 with a few aniline molecules inside, represented as C6H5NH2@SiO2@stearate, exhibiting fluorescence with red-shifted emission. Stearic acid functionalization allows the materials to be handled just as free molecules, for dissolution, precipitation, storage etc. The methodology adopted involves adsorption of aniline on the surface of gold nanoparticles with subsequent growth of a silica shell through monolayers, followed by the selective removal of the metal core either using sodium cyanide or by a new reaction involving halocarbons. The material is stable and can be stored for extended periods without loss of fluorescence. Spectroscopic and voltammetric properties of the system were studied in order to understand the interaction of aniline with the shell as well as the monolayer, whilst transmission electron microscopy has been used to study the silica shell.

  20. Size dependent photoresponse characteristics of crystalline Ge quantum dots based photodetectors

    Science.gov (United States)

    Bar, Rajshekhar; Manna, Santanu; Ray, Samit K.

    2016-10-01

    We report on the size dependent photoresponse behaviour of crystalline Ge quantum dots (QDs) dispersed within the silica matrix. Our findings demonstrate an increasing nature of EQE with increase in QDs size, which could be attributed to the combined effect of Coulomb interaction of photogenerated carriers, QD/silica interface defects and electric field driven carrier separation and tunneling through the oxide barriers. In this regard, the bias dependent nonlinear response of the photocurrent has been explained on the basis of cold field emission (CFE) model. Besides, the EQE is extended (>100%) for larger sized QDs, suggesting the trapping of slower holes in Ge QDs creating a charge neutrality issue.

  1. Synthesis and Characterization of ZSM-5/β Co-Crystalline Zeolite

    Institute of Scientific and Technical Information of China (English)

    Tianbo Zhao; Huiying Zhang; Fengyan Li; Chao Yang; Baoning Zong

    2005-01-01

    ZSM-5/β co-crystalline zeolites with different content of ZSM-5 have been synthesized by adding different amount of ZSM-5 to the synthetic system ofβ zeolite with NaAlO2, silica sol as the source of aluminum and silica, respectively, and TEA+ as the template under controlled condition of the synthesis. The ZSM-5/β co-crystalline zeolite was studied by XRD, SEM, BET and NH3-TPD. The reaction activity of toluene alkylation was investigated with a mixture of toluene-methanol as the feedstock in a pulse micro-reactor over the ZSM-5/β co-crystalline zeolite. It is found that ZSM-5/β co-crystalline zeolite has two kinds of zeolite structure including ZSM-5 and β zeolite, not in the form of a physical mixture. The pore structure of ZSM-5/β co-crystalline zeolites is different from that forβ zeolite, ZSM-5and their physical mixture. In addition, the peaks of both high and low temperature desorption of ammonia over the ZSM-5/β co-crystalline zeolite shift 23 ℃ to lower temperatures and the acid amount of its strong acid is 3% more than the physical mixture. So the ZSM-5/β co-crystalline zeolite produces the highest content of xylene, which is 10.4% higher than the physical mixture. And the ZSM-5/β co-crystalline zeolite has better selectivity for toluene alkylation and weaker de-methylation than β zeolite, ZSM-5 and their physical mixture.

  2. Genetics Home Reference: Bietti crystalline dystrophy

    Science.gov (United States)

    ... Understand Genetics Home Health Conditions Bietti crystalline dystrophy Bietti crystalline dystrophy Enable Javascript to view the expand/ ... boxes. Download PDF Open All Close All Description Bietti crystalline dystrophy is a disorder in which numerous ...

  3. Terahertz Spectroscopy of Crystalline and Non-Crystalline Solids

    DEFF Research Database (Denmark)

    Parrott, Edward P. J.; Fischer, Bernd M.; Gladden, Lynn F.

    2013-01-01

    Terahertz spectroscopy of crystalline and non-crystalline solids is probably one of the most active research fields within the terahertz community. Many potential applications, amongst which spectral recognition is probably one of the most prominent, have significantly stimulated the development...... selected examples, the potential the technique holds for various different applications. A particular focus will be given to data analysis and, in particular, how we may account for effects resulting from non-ideal sample preparation....

  4. Biphenyl liquid crystalline epoxy resin as a low-shrinkage resin-based dental restorative nanocomposite.

    Science.gov (United States)

    Hsu, Sheng-Hao; Chen, Rung-Shu; Chang, Yuan-Ling; Chen, Min-Huey; Cheng, Kuo-Chung; Su, Wei-Fang

    2012-11-01

    Low-shrinkage resin-based photocurable liquid crystalline epoxy nanocomposite has been investigated with regard to its application as a dental restoration material. The nanocomposite consists of an organic matrix and an inorganic reinforcing filler. The organic matrix is made of liquid crystalline biphenyl epoxy resin (BP), an epoxy resin consisting of cyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ECH), the photoinitiator 4-octylphenyl phenyliodonium hexafluoroantimonate and the photosensitizer champhorquinone. The inorganic filler is silica nanoparticles (∼70-100 nm). The nanoparticles were modified by an epoxy silane of γ-glycidoxypropyltrimethoxysilane to be compatible with the organic matrix and to chemically bond with the organic matrix after photo curing. By incorporating the BP liquid crystalline (LC) epoxy resin into conventional ECH epoxy resin, the nanocomposite has improved hardness, flexural modulus, water absorption and coefficient of thermal expansion. Although the incorporation of silica filler may dilute the reinforcing effect of crystalline BP, a high silica filler content (∼42 vol.%) was found to increase the physical and chemical properties of the nanocomposite due to the formation of unique microstructures. The microstructure of nanoparticle embedded layers was observed in the nanocomposite using scanning and transmission electron microscopy. This unique microstructure indicates that the crystalline BP and nanoparticles support each other and result in outstanding mechanical properties. The crystalline BP in the LC epoxy resin-based nanocomposite was partially melted during exothermic photopolymerization, and the resin expanded via an order-to-disorder transition. Thus, the post-gelation shrinkage of the LC epoxy resin-based nanocomposite is greatly reduced, ∼50.6% less than in commercialized methacrylate resin-based composites. This LC epoxy nanocomposite demonstrates good physical and chemical properties and good biocompatibility

  5. THE STRUCTURE AND PROPERTIES OF CHITOSAN/PPLYETHYLENE GLYCOL/SILICA TERNARY HYBRID ORGANIC-NORGANIC FILMS

    Institute of Scientific and Technical Information of China (English)

    Rui Song; Rui Xue; Ling-hao He; Ying Liu; Qiao-ling Xiao

    2008-01-01

    The ternary hybrid films consisting of chitosan(CS),polyethylene glycol(PEG)and nano-sized silica which was surface-modified by amino groups(RNSA)were prepared.The structures of the blend membranes were characterized by attenuation total reflection-infrared spectroscopy(ATR-IR),X-ray diffraction(XRD),optical microscopy(OM)and differential scanning calorimetry (DSC).The results showed that the addition of silica affected not only the distribution and crystallinity of PEG on the sample surface.but also the phase coarseness and the crystalline structure of chitosan in the blend system.Moreover,PEG changed the crystalline structure of chitosan.Upon annealing(at 100℃ for 1 h),the blends would show the altered crystalline structure of chitosan,the reinforced phase coarseness.as well as the decreased miscibility and interaction between chitosan and PEG.

  6. Two-dimensional silica: Structural, mechanical properties, and strain-induced band gap tuning

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Enlai; Xie, Bo [Applied Mechanics Laboratory, Department of Engineering Mechanics, and Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084 (China); Xu, Zhiping, E-mail: xuzp@tsinghua.edu.cn [Applied Mechanics Laboratory, Department of Engineering Mechanics, and Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084 (China); State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)

    2016-01-07

    Two-dimensional silica is of rising interests not only for its practical applications as insulating layers in nanoelectronics, but also as a model material to understand crystals and glasses. In this study, we examine structural and electronic properties of hexagonal and haeckelite phases of silica bilayers by performing first-principles calculations. We find that the corner-sharing SiO{sub 4} tetrahedrons in these two phases are locally similar. The robustness and resilience of these tetrahedrons under mechanical perturbation allow effective strain engineering of the electronic structures with band gaps covering a very wide range, from of that for insulators, to wide-, and even narrow-gap semiconductors. These findings suggest that the flexible 2D silica holds great promises in developing nanoelectronic devices with strain-tunable performance, and lay the ground for the understanding of crystalline and vitreous phases in 2D, where bilayer silica provides an ideal test-bed.

  7. Effects of Silica Nanostructures in Poly(ethylene oxide)-Based Composite Polymer Electrolytes.

    Science.gov (United States)

    Mohanta, Jagdeep; Anwar, Shahid; Si, Satyabrata

    2016-06-01

    The present work describes the synthesis of some poly(ethylene oxide)-based nanocomposite polymer electrolyte films using various silica nanostructures as the inorganic filler by simple solution mixing technique, in which the nature of the silica nanostructures play a vital role in modulating their electrochemical performances at room temperature. The silica nanostructures are prepared by ammonical hydrolysis of tetraethyl orthosilicate following the modified St6ber method. The resulting films are characterized by X-ray diffraction and differential scanning calorimeter to study their crystallinity. Room temperature AC impedance spectroscopy is utilized to determine the Li+ ion conductivity of the resulting films. The observed conductivity values of various NCPE films depend on the nature of silica filling as well as on their surface characteristics and also on the varying PEO-Li+ ratio, which is observed to be in the order of 10(-7)-10(-6) S cm(-1).

  8. Amorphization of Crystalline Water Ice

    CERN Document Server

    Zheng, Weijun; Kaiser, Ralf I

    2008-01-01

    We conducted a systematic experimental study to investigate the amorphization of crystalline ice by irradiation in the 10-50 K temperature range with 5 keV electrons at a dose of ~140 eV per molecule. We found that crystalline water ice can be converted partially to amorphous ice by electron irradiation. Our experiments showed that some of the 1.65-micrometer band survived the irradiation, to a degree that depends on the temperature, demonstrating that there is a balance between thermal recrystallization and irradiation-induced amorphization, with thermal recrystallizaton dominant at higher temperatures. At 50 K, recrystallization due to thermal effects is strong, and most of the crystalline ice survived. Temperatures of most known objects in the solar system, including Jovian satellites, Saturnian satellites, and Kuiper belt objects, are equal to or above 50 K, this might explain why water ice detected on those objects is mostly crystalline.

  9. Liquid-crystalline lanthanide complexes

    OpenAIRE

    Binnemans, Koen

    1999-01-01

    The paper describes the recent developments in the field of liquid-crystalline lanthanide complexes. The role of trivalent lanthanide ions as the central metal ion in metallomesogens is considered. An outlook for the future is given.

  10. Diffusion in porous crystalline materials

    NARCIS (Netherlands)

    Krishna, R.

    2012-01-01

    The design and development of many separation and catalytic process technologies require a proper quantitative description of diffusion of mixtures of guest molecules within porous crystalline materials. This tutorial review presents a unified, phenomenological description of diffusion inside meso-

  11. Study of interaction in silica glass via model potential approach

    Science.gov (United States)

    Mann, Sarita; Rani, Pooja

    2016-05-01

    Silica is one of the most commonly encountered substances in daily life and in electronics industry. Crystalline SiO2 (in several forms: quartz, cristobalite, tridymite) is an important constituent of many minerals and gemstones, both in pure form and mixed with related oxides. Cohesive energy of amorphous SiO2 has been investigated via intermolecular potentials i.e weak Van der Waals interaction and Morse type short-range interaction. We suggest a simple atom-atom based Van der Waals as well as Morse potential to find cohesive energy of glass. It has been found that the study of silica structure using two different model potentials is significantly different. Van der Waals potential is too weak (P.E =0.142eV/molecule) to describe the interaction between silica molecules. Morse potential is a strong potential, earlier given for intramolecular bonding, but if applied for intermolecular bonding, it gives a value of P.E (=-21.92eV/molecule) to appropriately describe the structure of silica.

  12. Femtosecond laser-induced periodic surface structures on silica

    Energy Technology Data Exchange (ETDEWEB)

    Hoehm, S.; Rosenfeld, A. [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Strasse 2A, D-12489 Berlin (Germany); Krueger, J.; Bonse, J. [BAM Bundesanstalt fuer Materialforschung und-pruefung, Unter den Eichen 87, D-12205 Berlin (Germany)

    2012-07-01

    The formation of laser-induced periodic surface structures (LIPSS) on two different silica polymorphs (single-crystalline synthetic quartz and commercial fused silica glass) upon irradiation in air with multiple linearly polarized single- and double-fs-laser pulse sequences ({tau} = 150 fs pulse duration, {lambda} = 800 nm center wavelength, temporal pulse separation {Delta}t < 40 ps) is studied experimentally and theoretically. Two distinct types of fs-LIPSS [so-called low-spatial-frequency LIPSS (LSFL) and high-spatial-frequency LIPSS (HSFL)] with different spatial periods and orientations were identified. Their appearance was characterized with respect to the experimental parameters peak laser fluence and number of laser pulses per spot. Additionally, the 'dynamics' of the LIPSS formation was addressed in complementary double-fs-pulse experiments with varying delays, revealing a characteristic change of the LSFL periods. The experimental results are interpreted on the basis of a Sipe-Drude model considering the carrier dependence of the optical properties of fs-laser excited silica. This new approach provides an explanation of the LSFL orientation parallel to the laser beam polarisation in silica - as opposed to the behaviour of most other materials.

  13. Solvent free amorphisation for pediatric formulations (minitablets) using mesoporous silica

    DEFF Research Database (Denmark)

    Monsuur, Fred; Choudhari, Yogesh; Reddy, Upendra

    2016-01-01

    silica gel is densely crowded with silanol groups, which can provide hydrogen-bonding possibilities with a drug, potentially resulting in amorphisation. Purpose: Amorphous drugs provide an advantage in solubility; however, their low physical stability always remained concern. Additional there was a need......Introduction: Most silica based amorphisation strategies are using organic solvent loading methods. Towards pediatric formulations this is creating concerns. With this in mind the development of a dry amorphisation strategy was the focus of this study. The high internal surface area of mesoporous...... does not involve organic solvents and is thereby acceptable for pediatric formulations, cost effective and time saving while increasing oral bioavailability of crystalline & poorly water soluble drugs....

  14. Amorphous and nanostructured silica and aluminosilicate spray-dried microspheres

    Science.gov (United States)

    Todea, M.; Turcu, R. V. F.; Frentiu, B.; Tamasan, M.; Mocuta, H.; Ponta, O.; Simon, S.

    2011-08-01

    Amorphous silica and aluminosilicate microspheres with diameters in the 0.1-20 μm range were produced by spray drying method. SEM, TEM and AFM images showed the spherical shape of the obtained particles. Based on thermal analysis data, several heat treatments have been applied on the as-prepared samples in order to check the amorphous state stability of the microspheres and to develop nanosized crystalline phases. As-prepared microspheres remain amorphous up to 1400 °C. By calcination at 1400 °C, cristobalite type nanocrystals are developed on silica sample, while in aluminosilicate sample first are developed mullite type nanocrystals and only after prolonged treatment are developed also cristobalite type nanocrystals. 29Si and 27Al MAS NMR results show that the local order around aluminum and silicon atoms strongly depend on the thermal history of the microspheres.

  15. Fabrication of thin silica layer-coated magnetite clusters (nFe{sub 3}O{sub 4}/silica) as anode materials for improved Li-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Hang-Deok; Lee, Sang-Wha, E-mail: Lswha@gachon.ac.kr

    2013-11-01

    Thin silica layer-coated magnetite clusters (nFe{sub 3}O{sub 4}/silica) were prepared as active anode materials for Li-ion batteries. First, citrate-capped magnetites (C-Fe{sub 3}O{sub 4}) were synthesized by the co-precipitation method. Then, 3-aminopropyl trimethoxysilane (APTMS)-linked magnetite clusters (A-nFe{sub 3}O{sub 4}) were formed via electrostatic interactions between carboxylate groups of C-Fe{sub 3}O{sub 4} and amine groups of APTMS, and the resulting A-nFe{sub 3}O{sub 4} were heat-treated under N{sub 2} flow for 2 h. The calcined A-nFe{sub 3}O{sub 4} at 500 °C exhibited the X-ray diffraction (XRD) patterns mostly attributed to fcc crystalline phases of Fe{sub 3}O{sub 4}, whereas the calcined C-Fe{sub 3}O{sub 4} at 500 °C exhibited the XRD patterns attributed to the mixture of fcc crystalline phases of Fe{sub 3}O{sub 4} and hexagonal crystalline phases of α-Fe{sub 2}O{sub 3}. The calcined A-nFe{sub 3}O{sub 4} (i.e., nFe{sub 3}O{sub 4}/silica) exhibited the improved retention capacity by more than ca. 50% after 50 cycles as compared to the pristine iron oxides. The improved retention capacity of nFe{sub 3}O{sub 4}/silica was attributed to the enhanced chemical stability and large surface area of the thin silica layer-coated iron oxide clusters. - Highlights: • Thin silica layer-coated iron oxides (nFe{sub 3}O{sub 4}/silica) were facilely prepared. • The nFe{sub 3}O{sub 4}/silica exhibited the improved capacity retention by more than 50%. • Inert silica layer minimized the pulverization of iron oxide clusters.

  16. Silica Micro Encapsulation

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, P.; Whitbread-Jordan, M. [KEECO (United Kingdom)

    2001-04-01

    The article explains how Silica Micro Encapsulation (SME) water treatment technology may be transferred from metal mining to coal mining operations. KEECO has been developing a unique solution for treating acid rock drainage in the metal sulphide mining sector and following trials in metal mining operations (described in the article), is preparing to transfer the technology to the coal industry. SME technology comprises metal precipitation and encapsulation accomplished with proprietary chemical, KB-1, and a group of patented chemical dosing systems, the K-series, to dose KB-1 into contaminated liquid wastes as a dry powder. 4 figs., 4 tabs.

  17. ZBLAN, Silica Fiber Comparison

    Science.gov (United States)

    1998-01-01

    This graph depicts the increased signal quality possible with optical fibers made from ZBLAN, a family of heavy-metal fluoride glasses (fluorine combined zirconium, barium, lanthanum, aluminum, and sodium) as compared to silica fibers. NASA is conducting research on pulling ZBLAN fibers in the low-g environment of space to prevent crystallization that limits ZBLAN's usefulness in optical fiber-based communications. In the graph, a line closer to the black theoretical maximum line is better. Photo credit: NASA/Marshall Space Flight Center

  18. Regenerated silica gel as stationary phase on vacuum column chromatography to purify temulawak’s extracts

    Energy Technology Data Exchange (ETDEWEB)

    Cahyono, Bambang; Maduwu, Ratna Dewi; Widayat,; Suzery, Meiny [Organic Chemistry Laboratory, Departement of Chemistry, Diponegoro University Jln Prof. Soedharto SH, Tembalang, Semarang 50275, Indonesia Tel / Fax: (024) 7460058 (Indonesia)

    2015-12-29

    Commercial silica gel only used once by many researchers and affected high cost for purification process, also less support the green chemistry program. This research focused in regeneration silica gel that used purification of temulawak’s extracts (Curcuma xanthorrhiza Roxb) by vacuum column chromatography. Sample extracts (contains 10.1195±0.5971% of curcuminoids) was purified by vacuum column chromatography (pressure: 45 kPa, column: 100mm on length and 16mm on diameter). Ethanol 96% and acetone were compared as eluent. The amount of solvent and yield of curcuminoids used as indicator purification. The silica gel was regenerated with heating in 600°C for 8 hours The silica gels were analyzed by IR spectroscopy and X-ray diffraction. Furthermore, regenerated silica gel was used as the stationary phase in vacuum column chromatography under the same conditions with the previous purification. All the purification experiments were performed in three repetitions. Based on regression equation, y=0.132x+0.0011 (r{sup 2}=0.9997) the yield of curcuminoids on purified products using ethanol as the eluent was improved 4.26% (to 14.3724±0.5749%) and by acetone was improved 3,03% (to 13.1450 ±0.6318%). The IR spectrum of both silica gel showed the same vibration profile and also there were three crystallinity peaks missing on its X-ray diffraction. Regenerated silica gel has the same performance with new silica gel in purification of temulawak’s extract: by ethanol has increased 4.08% (14.1947±0.7415%) and 2.93% (13.0447±0.4822) by acetone. In addition, all purification products showed similar TLC profiles. Purification using regenerated silica gel as the adsorbent on vacuum column chromatography has exactly same potential with the new silica gel.

  19. Porous Silica-Supported Solid Lipid Particles for Enhanced Solubilization of Poorly Soluble Drugs.

    Science.gov (United States)

    Yasmin, Rokhsana; Rao, Shasha; Bremmell, Kristen E; Prestidge, Clive A

    2016-07-01

    Low dissolution of drugs in the intestinal fluid can limit their effectiveness in oral therapies. Here, a novel porous silica-supported solid lipid system was developed to optimize the oral delivery of drugs with limited aqueous solubility. Using lovastatin (LOV) as the model poorly water-soluble drug, two porous silica-supported solid lipid systems (SSL-A and SSL-S) were fabricated from solid lipid (glyceryl monostearate, GMS) and nanoporous silica particles Aerosil 380 (silica-A) and Syloid 244FP (silica-S) via immersion/solvent evaporation. SSL particles demonstrated significantly higher rate and extent of lipolysis in comparison with the pure solid lipid, depending on the lipid loading levels and the morphology. The highest lipid digestion was observed when silica-S was loaded with 34% (w/w) solid lipid, and differential scanning calorimeter (DSC) analysis confirmed the encapsulation of up to 2% (w/w) non-crystalline LOV in this optimal SSL-S formulation. Drug dissolution under non-digesting intestinal conditions revealed a three- to sixfold increase in dissolution efficiencies when compared to the unformulated drug and a LOV-lipid suspension. Furthermore, the SSL-S provided superior drug solubilization under simulated intestinal digesting condition in comparison with the drug-lipid suspension and drug-loaded silica. Therefore, solid lipid and nanoporous silica provides a synergistic effect on optimizing the solubilization of poorly water-soluble compound and the solid lipid-based porous carrier system provides a promising delivery approach to overcome the oral delivery challenges of poorly water-soluble drugs.

  20. Regenerated silica gel as stationary phase on vacuum column chromatography to purify temulawak's extracts

    Science.gov (United States)

    Cahyono, Bambang; Maduwu, Ratna Dewi; Widayat, Suzery, Meiny

    2015-12-01

    Commercial silica gel only used once by many researchers and affected high cost for purification process, also less support the green chemistry program. This research focused in regeneration silica gel that used purification of temulawak's extracts (Curcuma xanthorrhiza Roxb) by vacuum column chromatography. Sample extracts (contains 10.1195±0.5971% of curcuminoids) was purified by vacuum column chromatography (pressure: 45 kPa, column: 100mm on length and 16mm on diameter). Ethanol 96% and acetone were compared as eluent. The amount of solvent and yield of curcuminoids used as indicator purification. The silica gel was regenerated with heating in 600°C for 8 hours The silica gels were analyzed by IR spectroscopy and X-ray diffraction. Furthermore, regenerated silica gel was used as the stationary phase in vacuum column chromatography under the same conditions with the previous purification. All the purification experiments were performed in three repetitions. Based on regression equation, y=0.132x+0.0011 (r2=0.9997) the yield of curcuminoids on purified products using ethanol as the eluent was improved 4.26% (to 14.3724±0.5749%) and by acetone was improved 3,03% (to 13.1450 ±0.6318%). The IR spectrum of both silica gel showed the same vibration profile and also there were three crystallinity peaks missing on its X-ray diffraction. Regenerated silica gel has the same performance with new silica gel in purification of temulawak's extract: by ethanol has increased 4.08% (14.1947±0.7415%) and 2.93% (13.0447±0.4822) by acetone. In addition, all purification products showed similar TLC profiles. Purification using regenerated silica gel as the adsorbent on vacuum column chromatography has exactly same potential with the new silica gel.

  1. Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.

    Science.gov (United States)

    Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen

    2015-12-15

    Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.

  2. DSPC/DLPC mixed films supported on silica: a QCM-D and friction force study.

    Science.gov (United States)

    Oguchi, Takakuni; Sakai, Kenichi; Sakai, Hideki; Abe, Masahiko

    2011-01-01

    The membrane properties of phospholipid mixtures supported on silica were studied by means of a quartz crystal microbalance with dissipation monitoring (QCM-D) technique, in situ soft-contact atomic force microscopy (AFM), and friction force microscopy (FFM). The phospholipids used in this study were di-stearoylphosphatidylcholine (DSPC) and dilauroylphosphatidylcholine (DLPC). The phospholipid films were prepared by a vesicle-fusion method, in which DSPC/DLPC mixed liposomes dispersed in an aqueous medium are adsorbed on silica and their structure is transformed into a bilayer on the substrate. The changes in QCM-D (frequency and dissipation) and friction responses of DSPC single systems (gel state at 25°C) are relatively large compared with those of DLPC single systems (liquid-crystalline state at 25°C) and those of mixed DSPC/DLPC systems. This suggests that (i) the gel-state DSPC liposomes are somewhat flattened on the silica, by keeping their solid-like molecular rigidity, whereas (ii) both the liquid-crystalline DLPC and mixed liposomes experience instantaneous structural transformation at the silica/water interface and form a normally flattened bilayer on the substrate. The friction force response is dependent on the phase state of the phospholipids, and the liquid-crystalline DLPC has a more significant impact on the overall membrane properties (i.e., the degree of swelling and the friction response on the surface) than does the gel-state DSPC.

  3. Computational molecular basis for improved silica surface complexation models

    Energy Technology Data Exchange (ETDEWEB)

    Sahai, Nita; Rosso, Kevin M.

    2006-06-06

    The acidity and reactivity of surface sites on amorphous and crystalline polymorphs of silica and other oxides control their thermodynamic stability and kinetic reactivity towards reactants in surface-controlled processes of environmental, industrial, biomedical and technological relevance. Recent advances in computational methodologies such as CPMD and increasing computer power combined with spectroscopic measurements are now making it possible to link, with an impressive degree of accuracy, the molecular-level description of these processes to phenomenological, surface complexation models The future challenge now lies in linking mesoscale properties at the nanometer scale to phenomenological models that will afford a more intuitive understanding of the systems under consideration.

  4. Workshop on hydrology of crystalline basement rocks

    Energy Technology Data Exchange (ETDEWEB)

    Davis, S.N. (comp.)

    1981-08-01

    This workshop covered the following subjects: measurements in relatively shallow boreholes; measurement and interpretation of data from deep boreholes; hydrologic properties of crystalline rocks as interpreted by geophysics and field geology; rock mechanics related to hydrology of crystalline rocks; the possible contributions of modeling to the understanding of the hydrology of crystalline rocks; and geochemical interpretations of the hydrology of crystalline rocks. (MHR)

  5. Nanostructures having crystalline and amorphous phases

    Science.gov (United States)

    Mao, Samuel S; Chen, Xiaobo

    2015-04-28

    The present invention includes a nanostructure, a method of making thereof, and a method of photocatalysis. In one embodiment, the nanostructure includes a crystalline phase and an amorphous phase in contact with the crystalline phase. Each of the crystalline and amorphous phases has at least one dimension on a nanometer scale. In another embodiment, the nanostructure includes a nanoparticle comprising a crystalline phase and an amorphous phase. The amorphous phase is in a selected amount. In another embodiment, the nanostructure includes crystalline titanium dioxide and amorphous titanium dioxide in contact with the crystalline titanium dioxide. Each of the crystalline and amorphous titanium dioxide has at least one dimension on a nanometer scale.

  6. Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation

    Directory of Open Access Journals (Sweden)

    Carolin C. Lechner

    2015-08-01

    Full Text Available Biomineralization processes leading to complex solid structures of inorganic material in biological systems are constantly gaining attention in biotechnology and biomedical research. An outstanding example for biomineral morphogenesis is the formation of highly elaborate, nano-patterned silica shells by diatoms. Among the organic macromolecules that have been closely linked to the tightly controlled precipitation of silica in diatoms, silaffins play an extraordinary role. These peptides typically occur as complex posttranslationally modified variants and are directly involved in the silica deposition process in diatoms. However, even in vitro silaffin-based peptides alone, with and without posttranslational modifications, can efficiently mediate biomimetic silica precipitation leading to silica material with different properties as well as with encapsulated cargo molecules of a large size range. In this review, the biomineralization process of silica in diatoms is summarized with a specific focus on silaffins and their in vitro silica precipitation properties. Applications in the area of bio- and nanotechnology as well as in diagnostics and therapy are discussed.

  7. Crystalline 'Genes' in Metallic Liquids

    CERN Document Server

    Sun, Yang; Ye, Zhuo; Fang, Xiaowei; Ding, Zejun; Wang, Cai-Zhuang; Mendelev, Mikhail I; Ott, Ryan T; Kramer, M J; Ho, Kai-Ming

    2014-01-01

    The underlying structural order that transcends the liquid, glass and crystalline states is identified using an efficient genetic algorithm (GA). GA identifies the most common energetically favorable packing motif in crystalline structures close to the alloy's Al-10 at.% Sm composition. These motifs are in turn compared to the observed packing motifs in the actual liquid structures using a cluster-alignment method which reveals the average topology. Conventional descriptions of the short-range order, such as Voronoi tessellation, are too rigid in their analysis of the configurational poly-types when describing the chemical and topological ordering during transition from undercooled metallic liquids to crystalline phases or glass. Our approach here brings new insight into describing mesoscopic order-disorder transitions in condensed matter physics.

  8. The Influence of Silica on the Reactivity of Iron Towards Chlorinated Hydrocarbons

    Science.gov (United States)

    Kohn, T.; Himmelheber, D. W.; Vikesland, P. J.; Fairbrother, D.; Roberts, A.

    2001-12-01

    depressed reaction rates relative to silica-free controls, even after silica was removed from the feed. We attribute this permanent reactivity loss to the partially irreversible buildup of a silica layer. Surface studies were conducted using iron coupons that had been exposed to solutions containing various amounts of sodium metasilicate for different periods of time. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), and Auger Electron Spectroscopy (AES) were used to determine the relative amounts of and distribution of silica on the iron surface. Surface analyses of the iron coupons exposed to 100 mg/L silica solution indicated that the concentration of adsorbed silica continuously grew with increasing exposure time. After two weeks, scanning AES showed that silica completely covers the surface of the iron. Below a silica concentration of 50 mg/L, the amount of silica sorbed by the iron surface was observed to be a linear function of the silica concentration. Above 50 mg/L, however, silica uptake was unchanged with increasing silica loading. This corresponds well to the reactivity loss pattern observed in batch experiments.

  9. Positronium diffusion in crystalline polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Serna, J. (Dept. de Fisica de Materiales, Univ. Complutense, Madrid (Spain))

    1990-12-16

    The analysis in four components of the positron lifetime spectra of nine different and structurally well characterised lamellar polyethylene samples has allowed to associate the two longest-lived components to positronium annihilation in the crystalline and amorphous phases. Further assumption on positronium tunneling through the interface between both phases, and a simple geometrical model, led to a value for the positronium diffusion coefficient in the crystalline phase of the order of 10{sup -4} cm{sup 2}/s. Interfaces have thicknesses around 1.5 nm and are shallow traps for positronium. (orig.).

  10. Single crystalline mesoporous silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Hochbaum, A.I.; Gargas, Daniel; Jeong Hwang, Yun; Yang, Peidong

    2009-08-04

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  11. Single crystalline mesoporous silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Hochbaum, Allon; Dargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-08-18

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. The photoluminescence of these nanowires suggest they are composed of crystalline silicon with small enough dimensions such that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices. A better understanding of this electroless route to mesoporous silicon could lead to facile and general syntheses of different narrow bandgap semiconductor nanostructures for various applications.

  12. Biogenic nanostructured silica

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Silicon is by far the most abundant element in the earth crust and also is an essential element for higher plants, yet its biology and mechanisms in plant tolerance of biotic and abiotic stresses are poorly understood. Based on the molecular mechanisms of the biosilicification in marine organisms such as diatoms and sponges, the cell wall template-mediated self-assembly of nanostructured silica in marine organisms and higher plants as well as the related organic molecules are discussed. Understanding of the templating and structure-directed effects of silicon-processing organic molecules not only offers the clue for synthesizing silicon-based materials, but also helps to recognize the anomaly of silicon in plant biology.

  13. 21 CFR 582.1711 - Silica aerogel.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam...

  14. 21 CFR 182.1711 - Silica aerogel.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Silica aerogel. 182.1711 Section 182.1711 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam...

  15. 21 CFR 584.700 - Hydrophobic silicas.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRINKING WATER OF ANIMALS Listing of Specific Substances Affirmed as GRAS § 584.700 Hydrophobic silicas. (a) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No....

  16. THE HYDROTHERMAL REACTIONS OF MONOSODIUM TITANATE, CRYSTALLINE SILICOTITANATE AND SLUDGE IN THE MODULAR SALT PROCESS: A LITERATURE SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Fondeur, F.; Pennebaker, F.; Fink, S.

    2010-11-11

    The use of crystalline silicotitanate (CST) is proposed for an at-tank process to treat High Level Waste at the Savannah River Site. The proposed configuration includes deployment of ion exchange columns suspended in the risers of existing tanks to process salt waste without building a new facility. The CST is available in an engineered form, designated as IE-911-CW, from UOP. Prior data indicates CST has a proclivity to agglomerate from deposits of silica rich compounds present in the alkaline waste solutions. This report documents the prior literature and provides guidance for the design and operations that include CST to mitigate that risk. The proposed operation will also add monosodium titanate (MST) to the supernate of the tank prior to the ion exchange operation to remove strontium and select alpha-emitting actinides. The cesium loaded CST is ground and then passed forward to the sludge washing tank as feed to the Defense Waste Processing Facility (DWPF). Similarly, the MST will be transferred to the sludge washing tank. Sludge processing includes the potential to leach aluminum from the solids at elevated temperature (e.g., 65 C) using concentrated (3M) sodium hydroxide solutions. Prior literature indicates that both CST and MST will agglomerate and form higher yield stress slurries with exposure to elevated temperatures. This report assessed that data and provides guidance on minimizing the impact of CST and MST on sludge transfer and aluminum leaching sludge.

  17. Crystalline polarity of ZnO thin films deposited under dc external bias on various substrates

    Science.gov (United States)

    Ohsawa, Takeo; Tsunoda, Kei; Dierre, Benjamin; Zellhofer, Caroline; Grachev, Sergey; Montigaud, Hervé; Ishigaki, Takamasa; Ohashi, Naoki

    2017-04-01

    Effects of the nature of substrates, either crystalline or non-crystalline, on the structure and properties of ZnO films deposited by sputtering were investigated. This study focuses mainly on the role of the external electric bias applied to substrates during magnetron sputtering deposition in controlling crystalline polarity, i.e., Zn-face or O-face, and the resulting film properties. It was found that polarity control was achieved on silica and silicon substrates but not on sapphire substrates. The substrate bias did influence the lattice parameters in the structural formation; however, the selection of the substrate type had a significant influence on the defect structures and the film properties.

  18. Preparation of silica coatings heavily doped with spiropyran using perhydropolysilazane as the silica source and their photochromic properties.

    Science.gov (United States)

    Yamano, Akihiro; Kozuka, Hiromitsu

    2009-04-30

    Silica coatings doped with spiropyran (SP) were prepared using xylene solutions of perhydropolysilazane (PHPS) as the silica source, where the SP-doped PHPS coatings were prepared by spin-coating and the PHPS-to-silica conversion was achieved by exposing the coatings to the vapor from aqueous ammonia at room temperature. The films could be heavily doped with SP at SP/(SP + PHPS) mass ratio as high as 0.2. The as-deposited SP-doped PHPS films were transparent and light-yellow, which turned to red as the PHPS-to-silica conversion proceeded, where the absorbance at 500 nm increased. When the films were stored in air in the dark for 73 h after the exposure treatment, the absorbance at 500 nm further increased, where the film turned from red to dark red. The SP-doped silica coatings thus obtained showed reversible photochromic reaction, where the absorbance at 500 nm decreased and increased when the films were irradiated with visible and ultraviolet light, respectively. The pencil hardness of the films was higher than 9H at a load of 1 kg, while significant amount of SP was leached out when the films were soaked in xylene.

  19. Fabrication of a submicrometer crystalline structure by thermoplastic holography.

    Science.gov (United States)

    Wang, X; Su, H; Zhang, L; He, Y; Zheng, X; Wang, H

    2001-11-01

    We report what we believe to be a novel method for fabrication of permanent submicrometer periodic structures by interference laser fields. The new method is holographic lithography combined with laser-induced thermoplastification. The crystalline structures that result from this new method not only can be maintained permanently after the optical field is evacuated but also can be rewritten by exposure of an inteference laser field for the second time. The process of fabrication is rapid, convenient, and effective.

  20. Generic Crystalline Disposal Reference Case

    Energy Technology Data Exchange (ETDEWEB)

    Painter, Scott Leroy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, Shaoping [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harp, Dylan Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Perry, Frank Vinton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wang, Yifeng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-02-20

    A generic reference case for disposal of spent nuclear fuel and high-level radioactive waste in crystalline rock is outlined. The generic cases are intended to support development of disposal system modeling capability by establishing relevant baseline conditions and parameters. Establishment of a generic reference case requires that the emplacement concept, waste inventory, waste form, waste package, backfill/buffer properties, EBS failure scenarios, host rock properties, and biosphere be specified. The focus in this report is on those elements that are unique to crystalline disposal, especially the geosphere representation. Three emplacement concepts are suggested for further analyses: a waste packages containing 4 PWR assemblies emplaced in boreholes in the floors of tunnels (KBS-3 concept), a 12-assembly waste package emplaced in tunnels, and a 32-assembly dual purpose canister emplaced in tunnels. In addition, three failure scenarios were suggested for future use: a nominal scenario involving corrosion of the waste package in the tunnel emplacement concepts, a manufacturing defect scenario applicable to the KBS-3 concept, and a disruptive glaciation scenario applicable to both emplacement concepts. The computational approaches required to analyze EBS failure and transport processes in a crystalline rock repository are similar to those of argillite/shale, with the most significant difference being that the EBS in a crystalline rock repository will likely experience highly heterogeneous flow rates, which should be represented in the model. The computational approaches required to analyze radionuclide transport in the natural system are very different because of the highly channelized nature of fracture flow. Computational workflows tailored to crystalline rock based on discrete transport pathways extracted from discrete fracture network models are recommended.

  1. Functionalized silica materials for electrocatalysis

    Indian Academy of Sciences (India)

    Vellaichamy Ganesan

    2015-02-01

    Electrocatalysis is an important phenomenon which is utilized in metal–air batteries, fuel cells, electrochemical sensors, etc. To increase the efficiency of the electrocatalytic process and to increase the electrochemical accessibility of the immobilized electrocatalysts, functionalized and non-functionalized mesoporous organo-silica (MCM41-type-materials) are used in this study. These materials possess several suitable properties to be durable catalysts and/or catalyst supports. Owing to the uniform dispersion of electrocatalysts (metal complex and/or metal nanoparticles (NPs)) on the functionalized and non-functionalized silica, an enormous increase in the redox current is observed. Long range channels of silica materials with pore diameter of 15–100 Å allowed metal NPs to accommodate in a specified manner in addition to other catalysts. The usefulness of MCM-41-type silica in increasing the efficiency of electrocatalysisis demonstrated by selecting oxygen, carbon dioxide and nitrite reduction reactions as examples

  2. Surface functionalization for tailoring the aggregation and magnetic behaviour of silica-coated iron oxide nanostructures

    Science.gov (United States)

    Roca, A. G.; Carmona, D.; Miguel-Sancho, N.; Bomatí-Miguel, O.; Balas, F.; Piquer, C.; Santamaría, J.

    2012-04-01

    We report here a detailed structural and magnetic study of different silica nanocapsules containing uniform and highly crystalline maghemite nanoparticles. The magnetic phase consists of 5 nm triethylene glycol (TREG)- or dimercaptosuccinic acid (DMSA)-coated maghemite particles. TREG-coated nanoparticles were synthesized by thermal decomposition. In a second step, TREG ligands were exchanged by DMSA. After the ligand exchange, the ζ potential of the particles changed from - 10 to - 40 mV, whereas the hydrodynamic size remained constant at around 15 nm. Particles coated by TREG and DMSA were encapsulated in silica following a sol-gel procedure. The encapsulation of TREG-coated nanoparticles led to large magnetic aggregates, which were embedded in coalesced silica structures. However, DMSA-coated nanoparticles led to small magnetic clusters inserted in silica spheres of around 100 nm. The final nanostructures can be described as the result of several competing factors at play. Magnetic measurements indicate that in the TREG-coated nanoparticles the interparticle magnetic interaction scenario has not dramatically changed after the silica encapsulation, whereas in the DMSA-coated nanoparticles, the magnetic interactions were screened due to the function of the silica template. Moreover, the analysis of the AC susceptibility suggests that our systems essentially behave as cluster spin glass systems.

  3. A Review for Characterization of Silica Fume and Its Effects on Concrete Properties

    Directory of Open Access Journals (Sweden)

    Mohammad Panjehpour

    2011-12-01

    Full Text Available Mineral additions which are also known as mineral admixtures have been used in Portland cement for many years. There are two types of additions which are commonly mixed into the Portland clinker or blended directly with cement these days. They are crystalline, also known as hydraulically inactive additions and pozzolanic, which are hydraulically active additions. Silica fume is very reactive pozzolan, while it is used in concrete because of its fine particles, large surface area and high SiO2 content. Silica fume is much fined separated silica obtained as a by-product in industry. It is used as an admixture in the concrete mix and it has significant effects on the properties of the resulting material. Simultaneously, silica fume can be also utilized in production of refectory and porcelain, to increase intensity and durability. In addition, it can improve the overall performance of the material as filler used in coating resin, paint, rubber and other high molecular materials. This review paper discusses the effects of silica fume on the concrete properties such as strength, modulus, ductility, permeability, chemical attack resistance, corrosion, freeze-thaw durability, creep rate. Characterisation of silica fume as well as its physical and chemical properties will also be reviewed in this paper.

  4. Impact of pore characteristics of silica materials on loading capacity and release behavior of ibuprofen

    Energy Technology Data Exchange (ETDEWEB)

    Numpilai, Thanapha [Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Muenmee, Suthaporn [Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Center for Advanced Studies in Nanotechnology and Its Applications in Chemical Food and Agricultural Industries, Kasetsart University, Bangkok 10900 (Thailand); Witoon, Thongthai, E-mail: fengttwi@ku.ac.th [Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Center for Advanced Studies in Nanotechnology and Its Applications in Chemical Food and Agricultural Industries, Kasetsart University, Bangkok 10900 (Thailand); NANOTEC-KU-Center of Excellence on Nanoscale Materials Design for Green Nanotechnology, Kasetsart University, Bangkok 10900 (Thailand)

    2016-02-01

    Impact of pore characteristics of porous silica supports on loading capacity and release behavior of ibuprofen was investigated. The porous silica materials and ibuprofen-loaded porous silica materials were thoroughly characterized by N{sub 2}-sorption, thermal gravimetric and derivative weight analyses (TG-DTW), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) to determine the physical properties of materials, amount of ibuprofen adsorbed and position of ibuprofen. The detailed characterization reveals that the ibuprofen molecules adsorbed inside the mesopores. Increasing the mesopore size from 5 nm to 10 nm increased the ibuprofen loading from 0.74 to 0.85 mmol/g, respectively. Incorporation of macropore into the structure of porous silica materials enhanced the ibuprofen loading capacity of 11.8–20.3%. The ibuprofen-loaded bimodal meso-macroporous silica materials exhibited the highest dissolution of 92 wt.% within an hour. The ibuprofen particles deposited on the external surface of the porous silica materials showed a lower dissolution rate than the ibuprofen adsorbed inside the mesopores due to the formation of ibuprofen crystalline. - Highlights: • Impacts of pore characteristics of supports on adsorption and release of ibuprofen • Increasing mesopore size increased the ibuprofen loading and dissolution rate. • Macropores reduced the diffusion pathway of ibuprofen and dissolution medium.

  5. Self-induced growth of vertical GaN nanowires on silica

    Science.gov (United States)

    Kumaresan, V.; Largeau, L.; Oehler, F.; Zhang, H.; Mauguin, O.; Glas, F.; Gogneau, N.; Tchernycheva, M.; Harmand, J.-C.

    2016-04-01

    We study the self-induced growth of GaN nanowires on silica. Although the amorphous structure of this substrate offers no possibility of an epitaxial relationship, the nanowires are remarkably aligned with the substrate normal whereas, as expected, their in-plane orientation is random. Their structural and optical characteristics are compared to those of GaN nanowires grown on standard crystalline Si (111) substrates. The polarity inversion domains are much less frequent, if not totally absent, in the nanowires grown on silica, which we find to be N-polar. This work demonstrates that high-quality vertical GaN nanowires can be elaborated without resorting to bulk crystalline substrates.

  6. Phase diagrams of binary crystalline-crystalline polymer blends.

    Science.gov (United States)

    Matkar, Rushikesh A; Kyu, Thein

    2006-08-17

    A thermodynamically self-consistent theory has been developed to establish binary phase diagrams for two-crystalline polymer blends by taking into consideration all interactions including amorphous-amorphous, crystal-amorphous, amorphous-crystal, and crystal-crystal interactions. The present theory basically involves combination of the Flory-Huggins free energy for amorphous-amorphous isotropic mixing and the Landau free energy of polymer solidification (e.g., crystallization) of the crystalline constituents. The self-consistent solution via minimization of the free energy of the mixture affords determination of eutectic, peritectic, and azeotrope phase diagrams involving various coexistence regions such as liquid-liquid, liquid-solid, and solid-solid coexistence regions bound by liquidus and solidus lines. To validate the present theory, the predicted eutectic phase diagrams have been compared with the reported experimental binary phase diagrams of blends such as polyethylene fractions as well as polycaprolactone/trioxane mixtures.

  7. Measurement of the zero-field magnetic dipole moment of magnetizable colloidal silica spheres

    Energy Technology Data Exchange (ETDEWEB)

    Claesson, E M; Erne, B H; Bakelaar, I A; Kuipers, B W M; Philipse, A P [Van' t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands)

    2007-01-24

    The magnetic properties of dispersions of magnetic silica microspheres have been investigated by measuring the magnetization curves and the complex magnetic susceptibility as a function of frequency and field amplitude. The silica spheres appear to have a net permanent magnetic dipole moment, even in zero field, which is increased significantly after a temporary exposure of the silica colloids to a saturating magnetic field. The magnetic properties of the microparticles in zero field are discussed in terms of the number and the orientations of the embedded nanoparticle dipoles along an easy axis of magnetization in the absence of an external field.

  8. Magnetic heating of silica-coated manganese ferrite nanoparticles

    Science.gov (United States)

    Iqbal, Yousaf; Bae, Hongsub; Rhee, Ilsu; Hong, Sungwook

    2016-07-01

    Manganese ferrite nanoparticles were synthesized using the reverse micelle method; these particles were then coated with silica. The silica-coated nanoparticles were spherical in shape, with an average diameter of 14 nm. The inverse spinel crystalline structure was observed through X-ray diffraction patterns. The coating status of silica on the surface of the nanoparticles was confirmed with a Fourier transform infrared spectrometer. The superparamagnetic properties were revealed by the zero coercive force in the hysteresis curve. Controllable heating at a fixed temperature of 42 °C was achieved by changing either the concentration of nanoparticles in the aqueous solution or the intensity of the alternating magnetic field. We found that at a fixed field strength of 5.5 kA/m, the 2.6 mg/ml sample showed a saturation temperature of 42 °C for magnetic hyperthermia. On the other hand, at a fixed concentration of 3.6 mg/ml, a field intensity of 4.57 kA/m satisfied the required temperature of 42 °C.

  9. Interstellar Silicate Dust in the z=0.89 Absorber Towards PKS 1830-211: Crystalline Silicates at High Redshift?

    CERN Document Server

    Aller, Monique C; York, Donald G; Vladilo, Giovanni; Welty, Daniel E; Som, Debopam

    2012-01-01

    We present evidence of a >10-sigma detection of the 10 micron silicate dust absorption feature in the spectrum of the gravitationally lensed quasar PKS 1830-211, produced by a foreground absorption system at redshift 0.886. We have examined more than 100 optical depth templates, derived from both observations of Galactic and extragalactic sources and laboratory measurements, in order to constrain the chemical structure of the silicate dust. We find that the best fit to the observed absorption profile is produced by laboratory crystalline olivine, with a corresponding peak optical depth of tau_10=0.27+/-0.05. The fit is slightly improved upon by including small contributions from additional materials such as silica, enstatite, or serpentine, which suggests that the dust composition may consist of a blend of crystalline silicates. Combining templates for amorphous and crystalline silicates, we find that the fraction of crystalline silicates needs to be at least 95%. Given the rarity of extragalactic sources wit...

  10. Factors Influencing Material Removal And Surface Finish Of The Polishing Of Silica Glasses

    Science.gov (United States)

    2006-01-01

    autoclave . The growth is typically in the z-direction, and the bars are lumbered to generate the appropriate crystal orientation blanks, although the...liquid state. Thus, it does not crystallize , and forms a material with no long range crystalline order. Glasses are generally considered supercooled...e.g. coesite, cristobalite , stishovite, and tridymite) and is optically uni-axial along the z-axis (growth axis) [15]. The silica tetrahedrons are

  11. In Vitro Toxicity of Naturally Occurring Silica Nanoparticles in C1 Coal 
in Bronchial Epithelial Cells

    Directory of Open Access Journals (Sweden)

    Guangjian LI

    2012-10-01

    Full Text Available Background and objective China’s Xuan Wei County in Yunnan Province have the world’s highest incidence of lung cancer in nonsmoking women-20 times higher than the rest of China. Previous studies showed, this high lung cancer incidence may be associated with the silica particles embedded in the production combustion from the C1 coal. The aim of this study is to separate the silica particles from production combustion from the C1 bituminous coal in Xuan Wei County of Yunnan Province, and study in vitro toxicity of naturally occurring silica particles on BEAS-2B. Methods ①Separating the silica particles from combustion products of C1 bituminous coal by physical method, observing the morphology by Scanning Electron Microscope, analysis elements by SEM-EDX, observed the single particle morphology by Transmission Electron Microscope, analyed its particle size distribution by Laser particle size analyzer, the surface area of silica particles were determined by BET nitrogen adsorption analysis; ②Cell viability of the experimental group (silica; naturally occurring, control group (silica; industrial produced and crystalline silica was detected by assay used the 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT method, and the reactive oxygen species (ROS, lactate dehydrogenase (LDH were determined after 24 h-72 h exposed to these particles. Results ①The physical method can separate silica particles from production combustion from the C1 bituminous coal, which have different size, and from 30 nm to 120 nm particles accounted for 86.8%, different morphology, irregular surface area and containing trace of aluminum, calcium and iron and other elements; ②Under the same concentration, the experiment group have higher toxicity on BEAS-2B than control groups. Conclusion ①Physical method can separate silica particles from production combustion from the C1 bituminous coal and not change the original morphology and containing trace;

  12. Silica research in Glasgow

    CERN Document Server

    Barr, B W; Casey, M M; Clubley, D; Crooks, D R M; Danzmann, K; Elliffe, E J; Gossler, S; Grant, A; Grote, H; Heptonstall, A; Hough, J; Jennrich, O; Lück, H B; McIntosh, S A; Newton, G P; Palmer, D A; Plissi, M V; Robertson, D I; Robertson, N A; Rowan, S; Skeldon, K D; Sneddon, P; Strain, K A; Torrie, C I; Ward, H; Willems, P A; Willke, B; Winkler, W

    2002-01-01

    The Glasgow group is involved in the construction of the GEO600 interferometer as well as in R and D activity on technology for advanced gravitational wave detectors. GEO600 will be the first GW detector using quasi-monolithic silica suspensions in order to decrease thermal noise significantly with respect to steel wire suspensions. The results concerning GEO600 suspension mounting and performance will be shown in the first section. Section 2 is devoted to the present results from the direct measurement of thermal noise in mirrors mounted in the 10 m interferometer in Glasgow which has a sensitivity limit of 4 x 10 sup - sup 1 sup 9 m Hz sup - sup 1 sup / sup 2 above 1 kHz. Section 3 presents results on the measurements of coating losses. R and D activity has been carried out to understand better how thermal noise in the suspensions affects the detector sensitivity, and in section 4 a discussion on the non-linear thermoelastic effect is presented.

  13. Insecticidal efficacy of silica nanoparticles against Rhyzopertha dominica F. and Tribolium confusum Jacquelin du Val

    Directory of Open Access Journals (Sweden)

    Ziaee Masumeh

    2016-07-01

    Full Text Available Bioassays were conducted to assess the effects of two silicon dioxide nanoparticles of Aerosil® and Nanosav against adults of Rhyzopertha dominica F. and Tribolium confusum Jacquelin du Val. Silica nanoparticles were applied at the rates of 50, 100, 200 and 300 mg · kg−1 on wheat and peeled barley. The mortality was counted after 1, 2, 3, and 7 days of exposure. Another experiment was carried out to evaluate the effect of food source on the survival of beetles after exposure to silica nanoparticles. Adults were exposed to silica nanoparticles at the rate of 0.2 mg · cm−2 for 1 and 2 days on filter paper inside plastic Petri dishes, respectively. After exposure, the initial mortality was counted and live individuals of both species were held for a week in empty glass vials or vials containing wheat and wheat flour, respectively. Silica nanoparticles have high toxicity on R. dominica and T. confusum adults. Rhyzopertha dominica was more susceptible than T. confusum. However, the mortality of both species increased with increasing concentrations and time exposed to each concentration. At low concentrations, Aerosil® was more effective than Nanosav. Silica nanoparticles were more effective in wheat grains than barley. Results indicated that the initial mortality was so high that the impact of food source on delay mortality was unclear in most cases. Silica nanoparticles were efficient against tested species and can be used effectively in a stored grain integrated pest management program.

  14. Radiation hardening in sol-gel derived Er{sup 3+}-doped silica glasses

    Energy Technology Data Exchange (ETDEWEB)

    Hari Babu, B., E-mail: hariphy2012@gmail.com, E-mail: matthieu.lancry@u-psud.fr; León Pichel, Mónica [Laboratoire des Solides Irradiés, UMR CEA-CNRS 7642, Ecole Polytechnique, Université Paris Saclay, 91128 Palaiseau (France); Institut de Chimie Moléculaire et des Matériaux d' Orsay, UMR CNRS-UPSud 8182, Université Paris Sud, 91405 Orsay (France); Ollier, Nadège [Laboratoire des Solides Irradiés, UMR CEA-CNRS 7642, Ecole Polytechnique, Université Paris Saclay, 91128 Palaiseau (France); El Hamzaoui, Hicham; Bigot, Laurent; Savelii, Inna; Bouazaoui, Mohamed [Laboratoire PhLAM (UMR CNRS 8523), IRCICA (USR CNRS 3380), CERLA - FR CNRS 2416, Université Lille 1, Villeneuve d' Ascq Cedex F-59655 (France); Poumellec, Bertrand; Lancry, Matthieu, E-mail: hariphy2012@gmail.com, E-mail: matthieu.lancry@u-psud.fr [Institut de Chimie Moléculaire et des Matériaux d' Orsay, UMR CNRS-UPSud 8182, Université Paris Sud, 91405 Orsay (France); Ibarra, Angel [National Fusion Laboratory, CIEMAT, Avda Complutense 40, 28040 Madrid (Spain)

    2015-09-28

    The aim of the present paper is to report the effect of radiation on the Er{sup 3+}-doped sol-gel silica glasses. A possible application of these sol-gel glasses could be their use in harsh radiation environments. The sol-gel glasses are fabricated by densification of erbium salt-soaked nanoporous silica xerogels through polymeric sol-gel technique. The radiation-induced attenuation of Er{sup 3+}-doped sol-gel silica is found to increase with erbium content. Electron paramagnetic resonance studies reveal the presence of E′{sub δ} point defects. This happens in the sol-gel aluminum-silica glass after an exposure to γ-rays (kGy) and in sol-gel silica glass after an exposure to electrons (MGy). The concentration levels of these point defects are much lower in γ-ray irradiated sol-gel silica glasses. When the samples are co-doped with Al, the exposure to γ-ray radiation causes a possible reduction of the erbium valence from Er{sup 3+} to Er{sup 2+} ions. This process occurs in association with the formation of aluminum oxygen hole centers and different intrinsic point defects.

  15. Photocontrollable liquid-crystalline actuators

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Haifeng [Top Runner Incubation Center for Academia-Industry Fusion and Department of Materials and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka 940-2188 (Japan); Ikeda, Tomiki [Chemical Resources Laboratory, Tokyo Institute of Technology, R1-11, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503 (Japan)

    2011-05-17

    Coupling photochromic molecules with liquid crystalline (LC) materials enables one to reversibly photocontrol unique LC features such as phase transition, photoalignment, and molecular cooperative motion. LC elastomers show photomechanical and photomobile properties, directly converting light energy into mechanical energy. In well-defined LC block copolymers, regular patternings of nanostructures in macroscopic scales are fabricated by photo-manipulation of LC actuators. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Liquid Crystalline Esters of Dibenzophenazines

    Directory of Open Access Journals (Sweden)

    Kevin John Anthony Bozek

    2015-01-01

    Full Text Available A series of esters of 2,3,6,7-tetrakis(hexyloxydibenzo[a,c]phenazine-11-carboxylic acid was prepared in order to probe the effects of the ester groups on the liquid crystalline behavior. These compounds exhibit columnar hexagonal phases over broad temperature ranges. Variations in chain length, branching, terminal groups, and the presence of cyclic groups were found to modify transition temperatures without substantially destabilizing the mesophase range.

  17. EXAFS studies of crystalline materials

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, G.S.; Georgopoulos, P.

    1982-01-01

    The application of extended x-ray absorption fine structure (EXAFS) technique to the study of crystalline materials is discussed, and previously published work on the subject is reviewed with 46 references being cited. The theory of EXAFS, methods of data analysis, and the experimental techniques, including those based on synchrotron and laboratory facilities are all discussed. Absorption and fluorescence methods of detecting EXAFS also receive attention. (BLM)

  18. Inelastic deformation in crystalline rocks

    Science.gov (United States)

    Rahmani, H.; Borja, R. I.

    2011-12-01

    The elasto-plastic behavior of crystalline rocks, such as evaporites, igneous rocks, or metamorphic rocks, is highly dependent on the behavior of their individual crystals. Previous studies indicate that crystal plasticity can be one of the dominant micro mechanisms in the plastic deformation of crystal aggregates. Deformation bands and pore collapse are examples of plastic deformation in crystalline rocks. In these cases twinning within the grains illustrate plastic deformation of crystal lattice. Crystal plasticity is governed by the plastic deformation along potential slip systems of crystals. Linear dependency of the crystal slip systems causes singularity in the system of equations solving for the plastic slip of each slip system. As a result, taking the micro-structure properties into account, while studying the overall behavior of crystalline materials, is quite challenging. To model the plastic deformation of single crystals we use the so called `ultimate algorithm' by Borja and Wren (1993) implemented in a 3D finite element framework to solve boundary value problems. The major advantage of this model is that it avoids the singularity problem by solving for the plastic slip explicitly in sub steps over which the stress strain relationship is linear. Comparing the results of the examples to available models such as Von Mises we show the significance of considering the micro-structure of crystals in modeling the overall elasto-plastic deformation of crystal aggregates.

  19. ADVANCES IN LIQUID CRYSTALLINE POLYESTERS

    Institute of Scientific and Technical Information of China (English)

    W. J. Jackson

    1992-01-01

    Advances have been made in understanding the interactions of composition, molecular weight,liquid crystallinity, orientation, and three-dimensional crystallinity on the properties of injection-molded and melt-spun liquid crystalline polyesters (LCP's). Two classes of potentially low-cost LCP's were compared : (1) semiflexible LCP's prepared from 1,6-hexanediol and the dimethyl ester of either trans-4, 4'-stilbenedicarboxylic acid or 4.4 ′-biphenyldicarboxylic acid and (2) all-aromatic LCP's prepared from terephthalic acid, 2, 6-naphthalenedicarboxylic acid, the diacetate of hydroquinone,and the acetate of p-hydroxybenzoic acid. The effects of composition on the plastic properties of the 4-component all-aromatic LCP's were determined with the aid of a 3 × 3 factorial statistically designed experiment, the generation of equations with a computer program, and the plotting of three-dimensional figures and contour diagrams. The effects of absolute molecular weight (Mw) on the tensile strengths of the semiflexible LCP's and one of the all-aromatic LCP's having an excellent balance of plastic properties were also compared, and it was observed that the semiflexible LCP's required Mw's about 4 times higher than the all-aromatic LCP to attain a given strength. Persistence lengths and molecular modeling were used to explain these differences.

  20. Ceramics manufacturing contributes to ambient silica air pollution and burden of lung disease.

    Science.gov (United States)

    Liao, Chung-Min; Wu, Bo-Chun; Cheng, Yi-Hsien; You, Shu-Han; Lin, Yi-Jun; Hsieh, Nan-Hung

    2015-10-01

    Inhalation of silica (SiO2) in occupational exposures can cause pulmonary fibrosis (silicosis), lung function deficits, pulmonary inflammation, and lung cancer. Current risk assessment models, however, cannot fully explain the magnitude of silica-induced pulmonary disease risk. The purpose of this study was to assess human health risk exposed to airborne silica dust in Taiwan ceramics manufacturing. We conducted measurements to characterize workplace-specific airborne silica dust in tile and commodity ceramic factories and used physiologically based alveolar exposure model to estimate exposure dose. We constructed dose-response models for describing relationships between exposure dose and inflammatory responses, by which health risks among workers can be assessed. We found that silica contents were 0.22-33.04 % with mean concentration ranges of 0.11-5.48 and 0.46-1763.30 μg m(-3), respectively, in commodity and tile ceramic factories. We showed that granulation workers in tile ceramic factory had the highest total SiO2 lung burden (∼1000 mg) with cumulative SiO2 lung burden of ∼4 × 10(4) mg-year. The threshold estimates with an effect on human lung inflammation and fibrosis are 407.31 ± 277.10 (mean ± sd) and 505.91 ± 231.69 mg, respectively. For granulation workers, long-term exposure to airborne silica dust for 30-45 years was likely to pose severe adverse health risks of inflammation and fibrosis. We provide integrated assessment algorithms required to implement the analyses and maintain resulting concentration of silica dust at safety threshold level in the hope that they will stimulate further analyses and interpretation. We suggest that decision-makers take action to implement platforms for effective risk management to prevent the related long-term occupational disease in ceramics manufacturing.

  1. Chemical interactions of aluminum with aqueous silica at 25 degrees Celsius

    Science.gov (United States)

    Hem, John David; Roberson, C.E.; Lind, Carol J.; Polxer, W.L.

    1973-01-01

    Solutions containing from 10 -5 to 10 -2 moles per liter of aluminum and dissolved silica in various ratios were aged at pH levels between 4 and 10 at 25?C. A colloidal amorphous product having the composition of halloysite was produced in most solutions. It had a consistent and reversible equilibrium solubility equivalent to a standard free energy of formation of -8974 ? 1.0 kcal per mole for the formula A12Si2O5(OH)4. Some aging times were longer than 4 years, but most solutions gave consistent solubilities after only a few months of aging. Where silica concentrations were below about 10 -4 molar, microcrystalline gibbsite was formed below pH 6.0 and crystalline bayerite above pH 7.0, but only after much longer aging than was required for crystallization in silica-free solutions. Electron micrographs and diffraction patterns of the synthesized material indicate some crystallinity in the aluminosilicate, but no X-ray diffraction patterns could be obtained even in the material aged 4 years. Solubility relationships for solutions containing fluoride as well as silica and aluminum are explainable by using cryolite stabilities determined in previous work. Aluminum contents of 51 samples of water analyzed for other purposes are in reasonable agreement with the assumption of equilibrium with amorphous clay mineral species similar to the material synthesized in this work. Solubility calculations are summarized graphically for solutions of ionic strength of 0.01 and 0.10.

  2. Environmentally-Friendly Geopolymeric Binders Made with Silica

    Science.gov (United States)

    Erdogan, S. T.

    2013-12-01

    Portland cement (PC) is the ubiquitous binding material for constructions works. It is a big contributor to global warming and climate change since its production is responsible for 5-10 % of all anthropogenic CO2 emissions. Half of this emission arises from the calcination of calcareous raw materials and half from kiln fuel burning and cement clinker grinding. Recently there have been efforts to develop alternative binders with lower greenhouse gas emissions. One such class of binders is geopolymers, formed by activating natural or waste materials with suitable alkaline or acidic solutions. These binders use natural or industrial waste raw materials with a very low CO2 footprint from grinding of the starting materials, and some from the production of the activating chemicals. The total CO2 emissions from carefully formulated mixtures can be as low as 1/10th - 1/5th of those of PC concrete mixtures with comparable properties. While use of industrial wastes as raw materials is environmentally preferable, the variability of their chemical compositions over time renders their use difficult. Use of natural materials depletes resources but can have more consistent properties and can be more easily accepted. Silica sand is a natural material containing very high amounts of quartz. Silica fume is a very fine waste from silicon metal production that is mostly non-crystalline silica. This study describes the use of sodium hydroxide and sodium silicate solutions to yield mortars with mechanical properties comparable to those of portland cement mortars and with better chemical and thermal durability. Strength gain is slower than with PC mixtures at room temperature but adequate ultimate strength can be achieved with curing at slightly elevated temperatures in less than 24 h. The consistency of the chemical compositions of these materials and their abundance in several large, developing countries makes silica attractive for producing sustainable concretes with reduced carbon

  3. Infrared spectra of silica polymorphs

    Science.gov (United States)

    Koike, C.; Noguchi, R.; Chihara, H.; Suto, H.; Ohtaka, O.; Imai, Y.; Matsumoto, T.; Tsuchiyama, A.

    The existence of silica within several debris disks has been suggested. We investigate the annealing conditions of α-cristobalite, and further prepare various types of silica, including α-cristobalite, α-quartz, coesite, stishovite, and fused quartz, which are natural, synthetic or commercial samples. We compare the results to previous studies and find that α-cristobalite synthesized at higher temperature than annealed silica. The interesting result of features similar to those of forsterite should be highlighted, where αcristobalite and coesite showed similar peaks at 16, 33, and 69 μm as forsterite. The 69 μm band for αcristobalite is especially very broad and strong, and shifts largely to a shorter wavelengths under cooling to low temperatures. The band for coesite, however, is very sharp, and shifts only a small amount to longer wavelengths under cooling to low temperatures. The peak positions of 16 and 69-μm band due to α-cristobalite can become index for temperature of silica dust. We discuss the possibility of silica detection around debris disks.

  4. A model for the effects of germanium on silica biomineralization in choanoflagellates

    Science.gov (United States)

    Chappell, Helen; Ratcliffe, Sarah; Goldstein, Raymond E.

    2016-01-01

    Silica biomineralization is a widespread phenomenon of major biotechnological interest. Modifying biosilica with substances like germanium (Ge) can confer useful new properties, although exposure to high levels of Ge disrupts normal biosilicification. No clear mechanism explains why this disruption occurs. Here, we study the effect of Ge on loricate choanoflagellates, a group of protists that construct a species-specific extracellular lorica from multiple siliceous costal strips. High Ge exposures were toxic, whereas lower Ge exposures produced cells with incomplete or absent loricae. These effects can be ameliorated by restoring the germanium : silicon ratio, as observed in other biosilicifying organisms. We developed simulations of how Ge interacts with polymerizing silica. In our models, Ge is readily incorporated at the ends of silica forming from silicic acid condensation, but this prevents further silica polymerization. Our ‘Ge-capping’ model is supported by observations from loricate choanoflagellates. Ge exposure terminates costal strip synthesis and lorica formation, resulting in disruption to cytokinesis and fatal build-up of silicic acid. Applying the Ge-capping model to other siliceous organisms explains the general toxicity of Ge and identifies potential protective responses in metalloid uptake and sensing. This can improve the design of new silica biomaterials, and further our understanding of silicon metabolism. PMID:27655668

  5. New application of crystalline cellulose in rubber composites

    Science.gov (United States)

    Bai, Wen

    Rubber without reinforcement has limited applications. The strength of reinforced rubber composites can be ten times stronger than that of unreinforced rubbers. Therefore, rubber composites are widely used in various applications ranging from automobile tires to seals, valves, and gaskets because of their excellent mechanical elastic properties. Silica and carbon black are the two most commonly used reinforcing materials in rubber tires. They are derived from non-renewable materials and are expensive. Silica also contributes to a large amount of ash when used tires are disposed of by incineration. There is a need for a new reinforcing filler that is inexpensive, renewable and easily disposable. Cellulose is the most abundant natural polymer. Native cellulose includes crystalline regions and amorphous regions. Crystalline cellulose can be obtained by removing the amorphous regions with the acid hydrolysis of cellulose because the amorphous cellulose can be hydrolyzed faster than crystalline cellulose. We recently discovered that the partial replacement of silica with microcrystalline cellulose (MCC) provided numerous benefits: (1) low energy consumption for compounding, (2) good processability, (3) strong tensile properties, (4) good heat resistance, and (5) potential for good fuel efficiency in the application of rubber tires. Strong bonding between fillers and a rubber matrix is essential for imparting rubber composites with the desired properties for many specific applications. The bonding between hydrophilic MCC and the hydrophobic rubber matrix is weak and can be improved by addition of a coupling agent or surface modifications of MCC. In this study, MCC was surface-modified with acryloyl chloride or alkenyl ketene dimer (AnKD) to form acrylated MCC (A-MCC) and AnKD-modified MCC (AnKD-MCC). The surface modifications of MCC did not change the integrity and mechanical properties of MCC, but provided functional groups that were able to form covalent linkages with

  6. An International comparison of the crystallinity of calibration materials for the analysis of respirable alpha-quartz using X-ray diffraction and a comparison with results from the infrared KBr disc method.

    Science.gov (United States)

    Stacey, Peter; Kauffer, Edmond; Moulut, Jean-Claude; Dion, Chantal; Beauparlant, Martin; Fernandez, Pablo; Key-Schwartz, Rosa; Friede, Bernd; Wake, Derrick

    2009-08-01

    It is important that analytical results, produced to demonstrate compliance with exposure limits are comparable, to ensure controls are monitored to similar standards. Correcting a measurement result of respirable alpha-quartz for the percentage of crystalline material in the calibration dust is good analytical practice and significant changes in the values assigned to calibration materials will affect the interpretation of results by an analyst or occupational hygiene professional. The reissue of the certification for the quartz reference material NIST 1878a in 2005 and differences in comparative values obtained by other work created uncertainty about the values of crystallinity assigned to national calibration dusts for alpha-quartz. Members of an International Organization for Standardization working group for silica measurement ISO/TC146/SC2/WG7 collaborated to investigate the comparability of results by X-ray diffraction (XRD) and to reach a consensus. This paper lists the values recommended by the working group for use with XRD analysis. The values for crystallinity obtained for some of the materials (NIST 1878, Min-U-Sil5 and A9950) were 6-7% lower than the original certification or estimates reported in other comparisons. Crystallinity values obtained by XRD gave a good correlation with BET surface area measurements (r2 = 0.91) but not with mean aerodynamic particle size (r2 = 0.31). Subsamples of two of the materials (A9950 Respirable and Quin 1 Respirable) with smaller particle size distribution than their parent material did not show any significant change in their values for crystallinity, suggesting that the area XRD measurement of these materials within the particle size range collected is more dependent on how the quartz is formed geologically or how it is processed for use. A comparison of results from laboratories using the infrared (IR) and KBr disc method showed that this method is more dependent than XRD on differences in the particle size

  7. MECHANISMS CONTROLLING Ca ION RELEASE FROM SOL-GEL DERIVED IN SITU APATITE-SILICA NANOCOMPOSITE POWDER

    Directory of Open Access Journals (Sweden)

    Seyed Mohsen Latifi

    2015-03-01

    Full Text Available Ca ion release from bioactive biomaterials could play an important role in their bioactivity and osteoconductivity properties. In order to improve hydroxyapatite (HA dissolution rate, in situ apatite-silica nanocomposite powders with various silica contents were synthesized via sol-gel method and mechanisms controlling the Ca ion release from them were investigated. Obtained powders were characterized by X-ray diffraction (XRD and transmission electron spectroscopy (TEM techniques, acid dissolution test, and spectroscopy by atomic absorption spectrometer (AAS. Results indicated the possible incorporation of (SiO44- into the HA structure and tendency of amorphous silica to cover the surface of HA particles. However, 20 wt. % silica was the lowest amount that fully covered HA particles. All of the nanocomposite powders showed more Ca ion release compared with pure HA, and HA - 10 wt. % silica had the highest Ca ion release. The crystallinity, the crystallite size, and the content of HA, along with the integrity, thickness, and ion diffusion possibility through the amorphous silica layer on the surface of HA, were factors that varied due to changes in the silica content and were affected the Ca ion release from nanocomposite powders.

  8. Multifunctional clickable and protein-repellent magnetic silica nanoparticles.

    Science.gov (United States)

    Estupiñán, Diego; Bannwarth, Markus B; Mylon, Steven E; Landfester, Katharina; Muñoz-Espí, Rafael; Crespy, Daniel

    2016-02-07

    Silica nanoparticles are versatile materials whose physicochemical surface properties can be precisely adjusted. Because it is possible to combine several functionalities in a single carrier, silica-based materials are excellent candidates for biomedical applications. However, the functionality of the nanoparticles can get lost upon exposure to biological media due to uncontrolled biomolecule adsorption. Therefore, it is important to develop strategies that reduce non-specific protein-particle interactions without losing the introduced surface functionality. Herein, organosilane chemistry is employed to produce magnetic silica nanoparticles bearing differing amounts of amino and alkene functional groups on their surface as orthogonally addressable chemical functionalities. Simultaneously, a short-chain zwitterion is added to decrease the non-specific adsorption of biomolecules on the nanoparticles surface. The multifunctional particles display reduced protein adsorption after incubation in undiluted fetal bovine serum as well as in single protein solutions (serum albumin and lysozyme). Besides, the particles retain their capacity to selectively react with biomolecules. Thus, they can be covalently bio-functionalized with an antibody by means of orthogonal click reactions. These features make the described multifunctional silica nanoparticles a promising system for the study of surface interactions with biomolecules, targeting, and bio-sensing.

  9. Silica Aerogel: Synthesis and Applications

    Directory of Open Access Journals (Sweden)

    Jyoti L. Gurav

    2010-01-01

    Full Text Available Silica aerogels have drawn a lot of interest both in science and technology because of their low bulk density (up to 95% of their volume is air, hydrophobicity, low thermal conductivity, high surface area, and optical transparency. Aerogels are synthesized from molecular precursors by sol-gel processing. Special drying techniques must be applied to replace the pore liquid with air while maintaining the solid network. Supercritical drying is most common; however, recently developed methods allow removal of the liquid at atmospheric pressure after chemical modification of the inner surface of the gels, leaving only a porous silica network filled with air. Therefore, by considering the surprising properties of aerogels, the present review addresses synthesis of silica aerogels by the sol-gel method, as well as drying techniques and applications in current industrial development and scientific research.

  10. INTEROCC case-control study: lack of association between glioma tumors and occupational exposure to selected combustion products, dusts and other chemical agents.

    Science.gov (United States)

    Lacourt, Aude; Cardis, Elisabeth; Pintos, Javier; Richardson, Lesley; Kincl, Laurel; Benke, Geza; Fleming, Sarah; Hours, Martine; Krewski, Daniel; McLean, Dave; Parent, Marie-Elise; Sadetzki, Siegal; Schlaefer, Klaus; Schlehofer, Brigitte; Lavoue, Jerome; van Tongeren, Martie; Siemiatycki, Jack

    2013-04-12

    The aim was to investigate possible associations between glioma (an aggressive type of brain cancer) and occupational exposure to selected agents: combustion products (diesel and gasoline exhaust emissions, benzo(a)pyrene), dusts (animal dust, asbestos, crystalline silica, wood dust) and some other chemical agents (formaldehyde, oil mist, sulphur dioxide). The INTEROCC study included cases diagnosed with glioma during 2000-2004 in sub-regions of seven countries. Population controls, selected from various sampling frames in different centers, were frequency or individually matched to cases by sex, age and center. Face-to-face interviews with the subject or a proxy respondent were conducted by trained interviewers. Detailed information was collected on socio-economic and lifestyle characteristics, medical history and work history. Occupational exposure to the 10 selected agents was assessed by a job exposure matrix (JEM) which provides estimates of the probability and level of exposure for different occupations. Using a 25% probability of exposure in a given occupation in the JEM as the threshold for considering a worker exposed, the lifetime prevalence of exposure varied from about 1% to about 15% for the different agents. Associations between glioma and each of the 10 agents were estimated by conditional logistic regression, and using three separate exposure indices: i) ever vs. never; ii) lifetime cumulative exposure; iii) total duration of exposure. The study sample consisted of 1,800 glioma cases and 5,160 controls. Most odds ratio estimates were close to the null value. None of the ten agents displayed a significantly increased odds ratio nor any indication of dose-response relationships with cumulative exposure or with duration of exposure. Thus, there was no evidence that these exposures influence risk of glioma.

  11. Synthesis and Characterization of Bimodal Mesoporous Silica

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiaofang; GUO Cuili; WANG Xiaoli; WU Yuanyuan

    2012-01-01

    Mesoporous silica with controllable bimodal pore size distribution was synthesized with cetyltrimethylammonium bromide (CTAB) as chemical template for small mesopores and silica gel as physical template for large mesopores.The structure of synthesized samples were characterized by Fourier transform infrared (FT-IR) spectroscopy,X-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscopy (TEM) and N2 adsorption-desorption measurements.The experimental results show that bimodal mesoporous silica consists of small mesopores of about 3 nm and large mesopores of about 45 nm.The small mesopores which were formed on the external surface and pore walls of the silica gel had similar characters with those of MCM-41,while large mesopores were inherited from parent silica gel material.The pore size distribution of the synthesized silica can be adjusted by changing the relative content of TEOS and silica gel or the feeding sequence of silica gel and NH4OH.

  12. Toxic effect of silica nanoparticles on endothelial cells through DNA damage response via Chk1-dependent G2/M checkpoint.

    Directory of Open Access Journals (Sweden)

    Junchao Duan

    Full Text Available Silica nanoparticles have become promising carriers for drug delivery or gene therapy. Endothelial cells could be directly exposed to silica nanoparticles by intravenous administration. However, the underlying toxic effect mechanisms of silica nanoparticles on endothelial cells are still poorly understood. In order to clarify the cytotoxicity of endothelial cells induced by silica nanoparticles and its mechanisms, cellular morphology, cell viability and lactate dehydrogenase (LDH release were observed in human umbilical vein endothelial cells (HUVECs as assessing cytotoxicity, resulted in a dose- and time- dependent manner. Silica nanoparticles-induced reactive oxygen species (ROS generation caused oxidative damage followed by the production of malondialdehyde (MDA as well as the inhibition of superoxide dismutase (SOD and glutathione peroxidase (GSH-Px. Both necrosis and apoptosis were increased significantly after 24 h exposure. The mitochondrial membrane potential (MMP decreased obviously in a dose-dependent manner. The degree of DNA damage including the percentage of tail DNA, tail length and Olive tail moment (OTM were markedly aggravated. Silica nanoparticles also induced G2/M arrest through the upregulation of Chk1 and the downregulation of Cdc25C, cyclin B1/Cdc2. In summary, our data indicated that the toxic effect mechanisms of silica nanoparticles on endothelial cells was through DNA damage response (DDR via Chk1-dependent G2/M checkpoint signaling pathway, suggesting that exposure to silica nanoparticles could be a potential hazards for the development of cardiovascular diseases.

  13. Low Temperature Coating of Anatase Thin Films on Silica Glass Fibers by Liquid Phase Deposition

    Institute of Scientific and Technical Information of China (English)

    LI Shun; LIU Jiachen; FENG Tiecheng

    2007-01-01

    Uniform crystalline TiO2 thin films were coated on silica glass fibers by liquid phase deposition from aqueous solution of ammonium hexafluorotitanate at low temperature. TiO2 thin films and nanopowders were prepared by adding H3BO3 into (NH4)2TiF6 solution supersaturated with anatase nano-crystalline TiO2 at 40 ℃. The effects of the deposition conditions on the surface morphology, section morphology, thickness of the deposited TiO2 thin films were investigated. The results indicate that the growth rate and particle size of the thin films were controlled by both the deposition conditions and the amount of anatase nano-crystalline TiO2.

  14. Optothermal nonlinearity of silica aerogel

    CERN Document Server

    Braidotti, Maria Chiara; Fleming, Adam; Samuels, Michiel C; Di Falco, Andrea; Conti, Claudio

    2016-01-01

    We report on the characterization of silica aerogel thermal optical nonlinearity, obtained by z-scan technique. The results show that typical silica aerogels have nonlinear optical coefficient similar to that of glass $(\\simeq 10^{-12} $m$^2/$W), with negligible optical nonlinear absorption. The non\\-li\\-near coefficient can be increased to values in the range of $10^{-10} $m$^2/$W by embedding an absorbing dye in the aerogel. This value is one order of magnitude higher than that observed in the pure dye and in typical highly nonlinear materials like liquid crystals.

  15. Bulk nano-crystalline alloys

    OpenAIRE

    T.-S. Chin; Lin, C. Y.; Lee, M.C.; R.T. Huang; S. M. Huang

    2009-01-01

    Bulk metallic glasses (BMGs) Fe–B–Y–Nb–Cu, 2 mm in diameter, were successfully annealed to become bulk nano-crystalline alloys (BNCAs) with α-Fe crystallite 11–13 nm in size. A ‘crystallization-and-stop’ model was proposed to explain this behavior. Following this model, alloy-design criteria were elucidated and confirmed successful on another Fe-based BMG Fe–B–Si–Nb–Cu, 1 mm in diameter, with crystallite sizes 10–40 nm. It was concluded that BNCAs can be designed in general by the proposed cr...

  16. [Silica induced α-SMA expression in HBE cell line by targeting the PI3K/Akt pathway].

    Science.gov (United States)

    Li, Ai-ping; Hou, Zhi-guo; Fan, Jing-jing; Ji, Xiao-ming; Wang, Ting; Ni, Chun-hui

    2012-12-01

    To explore the role of the phosphatidylinositol 3 kinase/protein kinase B (PI3K/Akt) pathway in silica-induced α-SMA (α smooth muscle actin) expression in HEB (human bronchial epithelial) cell. The cultured HBE cells were divided into 5 groups: control, silica, PI3K inhibitor (Ly294002), both PI3K inhibitor (Ly294002) and silica at the same time and the inhibitor 24 h ahead of silica. The final concentrations of PI3K inhibitor and silica were 10 µmol/L and 100 µg/ml, respectively. Western blots were used to detect protein expressions of Akt, p-Akt, TGF-β and α-SMA. The location and expression of α-SMA were measured by immunofluorescence assay. HBE cell line exposed to silica can induce Akt phosphorylation, in which expressions of p-Akt were up regulated 1 times at 48 and the highest at 72 h. The expressions of TGFβ increased remarkably at 12 h and the peak at 48 h after silica exposure, while the expressions of α-SMA increased at 24 h and the highest at 72 h. However, the PI3K inhibitor (Ly294002) significantly down regulated α-SMA expression. When the cell line exposed to the PI3K inhibitor ahead of silica 24 h, the expressions of p-Akt and α-SMA were more remarkably down regulated which were decreased 1.5 times and 7.6 times respectively compare to silica exposure group. But no significant changes were found for TGFβ expressions. The immunofluorescence assay showed that silica can induce α-SMA expression, which located in cytoplasma, and PI3K inhibitor can decrease the expression. Silica induced α-SMA expression in HBE cell line is by targeting the PI3K/Akt pathway and PI3K inhibitor can repress α-SMA expression.

  17. Niobia-silica and silica membranes for gas separation

    NARCIS (Netherlands)

    Boffa, Vittorio

    2008-01-01

    This thesis describes the development of ceramic membranes suitable for hydrogen separation and CO2 recovery from gaseous streams. The research work was focused on the three different parts of which gas selective ceramic membranes are composed, i.e., the microporous gas selective silica layer, the m

  18. Effect of Dust Deposition on the Performance of Multi-Crystalline Photovoltaic Modules Based on Experimental Measurements

    OpenAIRE

    Khatib, Tamer; Kazem, Hussian; K. Sopian; Buttinger, Frank; Elmenreich, Wilfried; Albusaidi, Ahmed Said

    2016-01-01

    This paper investigates the dust effect on the photovoltaic module (multi-crystalline) performance (the output voltage and generated power). The degradation of PV performance due to the deposition of different pollutant types, and accumulation has been investigated. Experiments concerning the effects of air pollutants (red soil, ash, sand, calcium carbonate, and silica) on the power generated are conducted and analyzed. The results show that the reduction in PV voltage and power is strongly d...

  19. Incorporation of Vanadium Oxide in Silica Nanofiber Mats via Electrospinning and Sol-Gel Synthesis

    Directory of Open Access Journals (Sweden)

    Jeanne E. Panels

    2006-01-01

    Full Text Available Submicron scale vanadia/silica hybrid nanofiber mats have been produced by electrospinning silica sol-gel precursor containing vanadium oxytriisopropoxide (VOTIP, followed by calcinations at high temperature. The properties of the resulting inorganic hybrid nanofiber mats are compared to those of electrospun pure silica nanofibers. SEM images show fibers are submicron in diameter and their morphology is maintained after calcination. Physisorption experiments reveal that silica nanofiber mats have a high specific surface area of 63 m2/g. FT-IR spectra exhibit Si—O vibrations and indicate the presence of V2O5 in the fibers. XPS studies reveal that the ratio of Si to O is close to 0.5 on the surface of fibers and the amount of vanadium on the surface of fibers increases with calcination. XRD diffraction patterns show that silica nanofibers are amorphous and orthorhombic V2O5 crystals have formed after calcination. EFTEM images demonstrate the growth of crystals on the surface of fibers containing vanadium after calcination. SEM images of fibers with high-vanadium content (50 mol% V: Si show that vanadia crystals are mostly aligned along the fiber axis. XPS shows an increase in vanadium contents at the surface, and XRD patterns exhibit an increase in the degree of crystallinity. A coaxial electrospinning scheme has successfully been employed to selectively place V2O5 in the skin layer.

  20. SYNTHESIS AND CHARACTERIZATION OF CELLULOSE-SILICA COMPOSITE FIBER IN ETHANOL/WATER MIXED SOLVENTS

    Directory of Open Access Journals (Sweden)

    Ning Jia

    2011-04-01

    Full Text Available Cellulose-silica composite fiber samples have been successfully synthesized using cellulose solution, tetraethoxysilane, and NH3•H2O in ethanol/water mixed solvents at room temperature for 24 h. The cellulose solution was previously prepared by the dissolution of microcrystalline cellulose in a solvent mixture of N,N-dimethylacetamide (DMAc/lithium chloride (LiCl. The effect of the tetraethoxysilane concentration on the product was investigated. The products were characterized by X-ray powder diffraction (XRD, thermogravimetric analysis (TG, differential scanning calorimetric analysis (DSC, scanning electron microscopy (SEM, Fourier transform infrared spectrometry (FT-IR, energy-dispersive X-ray spectrum (EDS, and cross polarization magic angle spinning (CP/MAS solid state 13C-NMR. The morphology of the cellulose-silica composite fiber was investigated by SEM, while their composition was established from EDS measurements combined with the results of FT-IR spectral analysis and XRD patterns. The XRD, FT-IR and EDS results indicated that the obtained product was cellulose-silica composite fiber. The SEM micrographs showed that the silica particles were homogeneously dispersed in the cellulose fiber. The CP/MAS solid state 13C-NMR results indicated that the silica concentration had an influence on the crystallinity of the cellulose. This method is simple for preparation of cellulose-based composites.

  1. Structural Characterization of Silica Particles Extracted from Grass Stenotaphrum secundatum: Biotransformation via Annelids

    Directory of Open Access Journals (Sweden)

    A. Espíndola-Gonzalez

    2014-01-01

    Full Text Available This study shows the structural characterization of silica particles extracted from Stenotaphrum secundatum (St. Augustine grass using an annelid-based biotransformation process. This bioprocess starts when St. Augustine grass is turned into humus by vermicompost, and then goes through calcination and acid treatment to obtain silica particles. To determine the effect of the bioprocess, silica particles without biotransformation were extracted directly from the sample of grass. The characterization of the silica particles was performed using Infrared (FTIR and Raman spectroscopy, Transmission Electron Microscopy (TEM, X-ray Diffraction (XRD, Dynamic Light Scattering (DLS, and Energy Dispersion Spectroscopy (EDS. Both types of particles showed differences in morphology and size. The particles without biotransformation were essentially amorphous while those obtained via annelids showed specific crystalline phases. The biological relationship between the metabolisms of worms and microorganisms and the organic-mineral matter causes changes to the particles' properties. The results of this study are important because they will allow synthesis of silica in cheaper and more ecofriendly ways.

  2. Densification and Devitrification of Fused Silica Induced by Ballistic Impact: A Computational Investigation

    Directory of Open Access Journals (Sweden)

    Mica Grujicic

    2015-01-01

    Full Text Available A molecular-level computational investigation is carried out to determine the dynamic response and material topology changes of fused silica subjected to ballistic impact by a hard projectile. The analysis was focused on the investigation of specific aspects of the dynamic response and of the topological changes such as the deformation of highly sheared and densified regions, and the conversion of amorphous fused silica to SiO2 crystalline polymorphs (in particular, α-quartz and stishovite. The topological changes in question were determined by carrying out a postprocessing atom-coordination procedure. This procedure suggested the formation of stishovite (and perhaps α-quartz within fused silica during ballistic impact. To rationalize the findings obtained, the all-atom molecular-level computational analysis is complemented by a series of quantum-mechanics density functional theory (DFT computations. The latter computations enable determination of the relative potential energies of the fused silica, α-quartz and stishovite, under ambient pressure (i.e., under their natural densities as well as under imposed (as high as 50 GPa pressures (i.e., under higher densities and shear strains. In addition, the transition states associated with various fused-silica devitrification processes were identified. The results obtained are found to be in good agreement with their respective experimental counterparts.

  3. A thermodynamic and kinetic model for paste–aggregate interactions and the alkali–silica reaction

    Energy Technology Data Exchange (ETDEWEB)

    Guthrie, George D., E-mail: geo@lanl.gov; Carey, J. William

    2015-10-15

    A new conceptual model is developed for ASR formation based on geochemical principles tied to aqueous speciation, silica solubility, kinetically controlled mineral dissolution, and diffusion. ASR development is driven largely by pH and silica gradients that establish geochemical microenvironments between paste and aggregate, with gradients the strongest within the aggregate adjacent to the paste boundary (i.e., where ASR initially forms). Super-saturation of magadiite and okenite (crystalline ASR surrogates) occurs in the zone defined by gradients in pH, dissolved silica, Na{sup +}, and Ca{sup 2} {sup +}. This model provides a thermodynamic rather than kinetic explanation of why quartz generally behaves differently from amorphous silica: quartz solubility does not produce sufficiently high concentrations of H{sub 4}SiO{sub 4} to super-saturate magadiite, whereas amorphous silica does. The model also explains why pozzolans do not generate ASR: their fine-grained character precludes formation of chemical gradients. Finally, these gradients have interesting implications beyond the development of ASR, creating unique biogeochemical environments.

  4. Genetics of Bietti Crystalline Dystrophy.

    Science.gov (United States)

    Ng, Danny S C; Lai, Timothy Y Y; Ng, Tsz Kin; Pang, Chi Pui

    2016-01-01

    Bietti crystalline dystrophy (BCD) is an inherited retinal degenerative disease characterized by crystalline deposits in the retina, followed by progressive atrophy of the retinal pigment epithelium (RPE), choriocapillaris, and photoreceptors. CYP4V2 has been identified as the causative gene for BCD. The CYP4V2 gene belongs to the cytochrome P450 superfamily and encodes for fatty acid ω-hydroxylase of both saturated and unsaturated fatty acids. The CYP4V2 protein is localized most abundantly within the endoplasmic reticulum in the RPE and is postulated to play a role in the physiological lipid recycling system between the RPE and photoreceptors to maintain visual function. Electroretinographic assessments have revealed progressive dysfunction of rod and cone photoreceptors in patients with BCD. Several genotypes have been associated with more severe phenotypes based on clinical and electrophysiological findings. With the advent of multimodal imaging with spectral domain optical coherence tomography, fundus autofluorescence, and adaptive optics scanning laser ophthalmoscopy, more precise delineation of BCD severity and progression is now possible, allowing for the potential future development of targets for gene therapy.

  5. Optical absorption of neutron-irradiated silica fibers

    Energy Technology Data Exchange (ETDEWEB)

    Cooke, D.W.; Farnum, E.H.; Bennett, B.L. [Los Alamos National Lab., NM (United States)

    1996-10-01

    Induced-loss spectra of silica-based optical fibers exposed to high (10{sup 23} n-m{sup {minus}2}) and low (10{sup 21} n-m{sup {minus}2}) fluences of neutrons at the Los Alamos Spallation Radiation Effects Facility (LASREF) have been measured. Two types of fibers consisting of a pure fused silica core with fluorine-doped ({approximately}4 mole %) cladding were obtained from Fiberguide Industries and used in the as-received condition. Anhydroguide{trademark} and superguide{trademark} fibers contained less than 1 ppm, and 600 to 800 ppm of OH, respectively. The data suggest that presently available silica fibers can be used in plasma diagnostics, but the choice and suitability depends upon the spectral region of interest. Low-OH content fibers can be used for diagnostic purposes in the interval {approximately}800 to 1400 mn if the exposure is to high-fluence neutrons. For low-fluence neutron exposures, the low-OH content fibers are best suited for use in the interval {approximately}800 to 2000 nm, and the high-OH content fibers are the choice for the interval {approximately}400 to 800 nm.

  6. Large-scale synthesis of ultralong single-crystalline SiC nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jianjun [Center of Materials Engineering, Zhejiang Sci-Tech University, Xiasha College Park, 310018 Hangzhou (China); The Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Zhejiang Sci-Tech University, Ministry of Education, 310018 Hangzhou (China); Shi, Qiang [The Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Zhejiang Sci-Tech University, Ministry of Education, 310018 Hangzhou (China); Gao, Linhui; Zhu, Hongliang [Center of Materials Engineering, Zhejiang Sci-Tech University, Xiasha College Park, 310018 Hangzhou (China)

    2010-11-15

    A large number of cotton-like ultralong {beta}-SiC nanowires (NWs) were successfully synthesized via a simple catalyst-free carbothermal reduction approach using a carbonaceous silica xerogel as raw materials. The length of the NWs is in the millimeter range and the diameter of the NWs is about 130 nm. The ultralong NWs are bamboo-like single-crystalline {beta}-SiC NWs. A vapor-solid mechanism was proposed to elucidate the growth process of the NWs, and the large length and high-yield of the SiC NWs may be ascribed to the stable release of SiO and CO gases form the carbonaceous silica xerogel. The simple method provides a promising candidate for industrial fabrication of {beta}-SiC NWs. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  7. Mineral dust exposure in young Indian adults: an effect on lung growth?

    Science.gov (United States)

    Green, D A; McAlpine, G; Semple, S; Cowie, H; Seaton, A

    2008-05-01

    Long-term occupational exposure to mineral dusts including quartz is known to cause pneumoconiosis but little is known about the effects of such exposure during the period of lung development in childhood. The objective of this study was to investigate the effects on young people of exposure to mineral dusts. We carried out a cross-sectional study of a group of 81 Indian stone crushers (average age 21) and a control group of 72 nearby slum dwellers (average age 21) in order to assess dust exposures, respiratory symptoms and lung function. Stone crushers' corrected 8-hour time weighted average concentrations of total inhalable dust, respirable dust and respirable crystalline silica were 143 mg/m(3), 39.7 mg/m(3) and 2.29 mg/m(3) respectively, which are 14, 10 and 23 times the UK workplace exposure limits, respectively. Both groups also had high exposures to outdoor and general domestic particulate matter. Compared to controls, stone crushers had significantly more symptoms, lower levels of forced vital capacity (FVC) and forced expiratory time (FET) and higher levels of forced expiratory volume in one second (FEV(1))/FVC ratio and mid-expiratory flow rate (MEF). There were no differences in FEV(1) levels. Symptoms and lung function were not associated with time lived on site or time spent in job. A selection of chest radiographs showed no silicosis by International Labour Office (ILO) criteria. Individuals exposed to mixed mineral dust in childhood and early adult life had excess symptoms and reduced vital capacity without airflow obstruction compared with control subjects. We interpret this as evidence of stunting of lung growth caused by exposure to respirable dust.

  8. Ringing phenomenon in silica microspheres

    Institute of Scientific and Technical Information of China (English)

    Chunhua Dong; Changling Zou; Jinming Cui; Yong Yang; Zhengfu Han; Guangcan Guo

    2009-01-01

    Whispering gallery modes in silica microspheres are excited by a tunable continuous-wave laser through the fiber taper. Ringing phenomenon can be observed with high frequency sweeping speed. The thermal nonlinearity in the microsphere can enhance this phenomenon. Our measurement results agree very well with the theoretical predictions by the dynamic equation.

  9. The comparative immunotoxicity of mesoporous silica nanoparticles and colloidal silica nanoparticles in mice

    Science.gov (United States)

    Lee, Soyoung; Kim, Mi-Sun; Lee, Dakeun; Kwon, Taeg Kyu; Khang, Dongwoo; Yun, Hui-Suk; Kim, Sang-Hyun

    2013-01-01

    Background Mesoporous silica (MPS) nanoparticles (NPs), which have a unique pore structure and extremely large surface area and pore volume, have received much attention because of their biomedical application potential. Using MPS NPs for biomedical devices requires the verification of their biocompatibility because the surface area of NPs is one of the most important determinants of toxicity, including the cellular uptake and immune response. We have previously reported that the cytotoxicity and inflammation potential of MPS NPs have been shown to be lower than those of general amorphous colloidal silica (Col) NPs in macrophages, but the low cytotoxicity does not guarantee high biocompatibility in vivo. In this study, we compared the in vivo immunotoxicity of MPS and Col NPs in the mouse model to define the effects of pore structural conditions of silica NPs. Materials and methods Both MPS and Col NPs (2, 20, and 50 mg/kg/day) were intraperitoneally administered in female BALB/c mice for 4 weeks, and clinical toxicity, lymphocyte population, serum IgG/IgM levels, and histological changes were examined. Results There was no overt sign of clinical toxicity in either MPS- or Col-treated mice. However, MPS NPs led to significant increases in liver and spleen weight and splenocyte proliferation. Mice treated with MPS NPs showed altered lymphocyte populations (CD3+, CD45+, CD4+, and CD8+) in the spleen, increased serum IgG and IgM levels, and histological changes. Despite slight changes in lymphocyte populations in the spleen, Col NPs did not alter other immunological factors. Conclusion The results indicate that in vivo exposure to MPS NPs caused more damage to systemic immunity than that of Col NPs through the dysregulation of the spleen. The results for in vivo data are inconsistent with those for in vitro data, which show lower cytotoxicity for MPS NPs. These results suggest the importance of verifying biocompatibility both in vitro and in vivo during the design of

  10. High-volume samplers for the assessment of respirable silica content in metal mine dust via direct-on-filter analysis

    CSIR Research Space (South Africa)

    Cauda, EG

    2014-08-01

    Full Text Available exposure to silica by two main factors: 1) variability of the silica percent in the mining dust and 2) lengthy off-site laboratory analysis of collected samples. The collection of samples for short periods of time during the workers' shift and subsequent on...

  11. Influence of polyols on the formation of nanocrystalline nickel ferrite inside silica matrices

    Science.gov (United States)

    Stoia, Marcela; Barvinschi, Paul; Barbu-Tudoran, Lucian; Bunoiu, Mădălin

    2017-01-01

    We have synthesized nickel ferrite/silica nanocomposites, using a modified sol-gel method that combines the sol-gel processing with the thermal decomposition of metal-organic precursors, leading to a homogenous dispersion of ferrite nanoparticles within the silica matrix and a narrow size distribution. We used as starting materials tetraethyl orthosilicate (TEOS) as source of silica, Fe(III) and Ni(II) nitrates as sources of metal cations, and polyols as reducing agent (polyvinyl alcohol, 1,4-butanediol and their mixture). TG/DTA coupled technique evidenced the redox interaction between the polyol and the mixture of metal nitrates during the heating of the gel, with formation of nickel ferrite precursors in the pores of the silica-gels. FT-IR spectroscopy confirmed the formation of metal carboxylates inside the silica-gels and the interaction of the polyols with the Si-OH groups of the polysiloxane network. X-ray diffractometry evidenced that in case of nanocomposites obtained by using a single polyol, nickel ferrite forms as single crystalline phase inside the amorphous silica matrix, while in case of using a mixture of polyols the nickel oxide appears as a secondary phase. TEM microscopy and elemental mapping evidenced the fine nature of the obtained nickel ferrite nanoparticles that are homogenously dispersed within the silica matrix. The obtained nanocomposites exhibit magnetic behavior very close to superparamagnetism slightly depending on the presence and nature of the organic compounds used in synthesis; the magnetization reached at 5 kOe magnetic field was 7 emu/g for all composites.

  12. High-aluminum-affinity silica is a nanoparticle that seeds secondary aluminosilicate formation.

    Directory of Open Access Journals (Sweden)

    Ravin Jugdaohsingh

    Full Text Available Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7 we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP. Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m(2 g(-1 and it competes effectively with transferrin for Al(III binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III species binding monomeric silica to form early phase, non-toxic aluminosilicates.

  13. Silica-Coated Liposomes for Insulin Delivery

    Directory of Open Access Journals (Sweden)

    Neelam Dwivedi

    2010-01-01

    Full Text Available Liposomes coated with silica were explored as protein delivery vehicles for their enhanced stability and improved encapsulation efficiency. Insulin was encapsulated within the fluidic phosphatidylcholine lipid vesicles by thin film hydration at pH 2.5, and layer of silica was formed above lipid bilayer by acid catalysis. The presence of silica coating and encapsulated insulin was identified using confocal and electron microscopy. The native state of insulin present in the formulation was evident from Confocal Micro-Raman spectroscopy. Silica coat enhances the stability of insulin-loaded delivery vehicles. In vivo study shows that these silica coated formulations were biologically active in reducing glucose levels.

  14. Optical patterning of photosensitive thin film silica mesophases

    Energy Technology Data Exchange (ETDEWEB)

    DOSHI,DHAVAL A.; HUESING,NICOLA K.; LU,MENGCHENG; FAN,HONGYOU; HURD,ALAN J.; BRINKER,C. JEFFREY

    2000-02-09

    Photosensitive films incorporating molecular photoacid generators compartmentalized within a silica-surfactant mesophase were prepared by an evaporation-induced self-assembly process. UV-exposure promoted localized acid-catalyzed siloxane condensation, enabling selective etching of unexposed regions, thereby serving as a resistless technique to prepare patterned mesoporous silica. The authors also demonstrated an optically-defined mesophase transformation (hexagonal {r_arrow} tetragonal) and patterning of refractive index and wetting behavior. Spatial control of structure and function on the macro- and mesoscales is of interest for sensor arrays, nano-reactors, photonic and fluidic devices, and low dielectric constant films. More importantly, it extends the capabilities of conventional lithography from spatially defining the presence or absence of film to spatial control of film structure and function.

  15. Writing silica structures in liquid with scanning transmission electron microscopy.

    Science.gov (United States)

    van de Put, Marcel W P; Carcouët, Camille C M C; Bomans, Paul H H; Friedrich, Heiner; de Jonge, Niels; Sommerdijk, Nico A J M

    2015-02-04

    Silica nanoparticles are imaged in solution with scanning transmission electron microscopy (STEM) using a liquid cell with silicon nitride (SiN) membrane windows. The STEM images reveal that silica structures are deposited in well-defined patches on the upper SiN membranes upon electron beam irradiation. The thickness of the deposits is linear with the applied electron dose. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) demonstrate that the deposited patches are a result of the merging of the original 20 nm-diameter nanoparticles, and that the related surface roughness depends on the electron dose rate used. Using this approach, sub-micrometer scale structures are written on the SiN in liquid by controlling the electron exposure as function of the lateral position.

  16. Thermal conductivity of pure silica MEL and MFI zeolite thin films

    Science.gov (United States)

    Coquil, Thomas; Lew, Christopher M.; Yan, Yushan; Pilon, Laurent

    2010-08-01

    This paper reports the room temperature cross-plane thermal conductivity of pure silica zeolite (PSZ) MEL and MFI thin films. PSZ MEL thin films were prepared by spin coating a suspension of MEL nanoparticles in 1-butanol solution onto silicon substrates followed by calcination and vapor-phase silylation with trimethylchlorosilane. The mass fraction of nanoparticles within the suspension varied from 16% to 55%. This was achieved by varying the crystallization time of the suspension. The thin films consisted of crystalline MEL nanoparticles embedded in a nonuniform and highly porous silica matrix. They featured porosity, relative crystallinity, and MEL nanoparticles size ranging from 40% to 59%, 23% to 47% and 55 nm to 80 nm, respectively. PSZ MFI thin films were made by in situ crystallization, were b-oriented, fully crystalline, and had a 33% porosity. Thermal conductivity of these PSZ thin films was measured at room temperature using the 3ω method. The cross-plane thermal conductivity of the MEL thin films remained nearly unchanged around 1.02±0.10 W m-1 K-1 despite increases in (i) relative crystallinity, (ii) MEL nanoparticle size, and (iii) yield caused by longer nanoparticle crystallization time. Indeed, the effects of these parameters on the thermal conductivity were compensated by the simultaneous increase in porosity. PSZ MFI thin films were found to have similar thermal conductivity as MEL thin films even though they had smaller porosity. Finally, the average thermal conductivity of the PSZ films was three to five times larger than that reported for amorphous sol-gel mesoporous silica thin films with similar porosity and dielectric constant.

  17. The Pozzolanic reaction of silica fume

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    2012-01-01

    Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone. In the ...... of activation of the pozzolanic reaction of silica fume is estimated. The results show that the pozzolanic reaction of silica fume has notable differences from Portland cement hydration.......Silica fume is a very important supplementary cementitious binder in High-Performance and Ultra High-Performance Concretes. Through its pozzolanic reaction the silica fume densifies the concrete micro-structure, in particular it strengthens the paste-aggregate interfacial transition zone....... In the present paper different aspects of the pozzolanic reaction of silica fume are investigated. These include chemical shrinkage, isothermal heat development and strength development. Key data for these are given and compared with theoretical calculations, and based on presented measurements the energy...

  18. Silica Pigments for Glossy Ink Jet Media

    Institute of Scientific and Technical Information of China (English)

    Sun Qi; Michael R. Sestrick; Yoshi Sugimoto; William A. Welsh

    2004-01-01

    Silica is a versatile pigment for ink jet media. Micronized silica gel is the worldwide standard for high performance matte ink jet media. For glossy ink jet media, several different forms of silica are widely used. Submicron silica gel dispersions, with either anionic or cationic surfaces, can be employed in either absorptive basecoat layers or in the glossy ink receptive top layer. Colloidal silica, with a variety of particle sizes and surface modifications, is utilized extensively in glossy top layers. It will show how various silica pigments can be utilized in glossy ink receptive coatings, both in cast based glossy media and RC based glossy media. Several novel silica pigments will be examined by relating the physical properties of the pigments and the formula variables to the print quality of the ink jet media.

  19. Vibrational Properties of a Two-Dimensional Silica Kagome Lattice.

    Science.gov (United States)

    Björkman, Torbjörn; Skakalova, Viera; Kurasch, Simon; Kaiser, Ute; Meyer, Jannik C; Smet, Jurgen H; Krasheninnikov, Arkady V

    2016-12-27

    Kagome lattices are structures possessing fascinating magnetic and vibrational properties, but in spite of a large body of theoretical work, experimental realizations and investigations of their dynamics are scarce. Using a combination of Raman spectroscopy and density functional theory calculations, we study the vibrational properties of two-dimensional silica (2D-SiO2), which has a kagome lattice structure. We identify the signatures of crystalline and amorphous 2D-SiO2 structures in Raman spectra and show that, at finite temperatures, the stability of 2D-SiO2 lattice is strongly influenced by phonon-phonon interaction. Our results not only provide insights into the vibrational properties of 2D-SiO2 and kagome lattices in general but also suggest a quick nondestructive method to detect 2D-SiO2.

  20. Surface analysis and anti-graffiti behavior of a weathered polyurethane-based coating embedded with hydrophobic nano silica

    Science.gov (United States)

    Rabea, A. Mohammad; Mohseni, M.; Mirabedini, S. M.; Tabatabaei, M. Hashemi

    2012-03-01

    In this study, a permanent anti-graffiti polyurethane coating was prepared using concomitant loading of an OH-functional silicone modified polyacrylate additive ranging from 2 to 15 mol% and hydrophobic silica nanoparticles from 1 to 5 wt%. UV-visible spectroscopy, contact angle measurement and dynamic mechanical thermal analysis (DMTA) analysis were conducted on selected samples to study the weathering performance of samples containing various amounts of silica nanoparticles before and after accelerated weathering conditions. The results showed that higher amounts of additive had inferior effects on the anti-graffiti performance of the coating samples after exposure. However, silica nanoparticles could positively affect the anti-graffiti performance against ageing cycles. This improvement was attributed to lower degradation of samples containing silica nanoparticles and barrier property of nanoparticles against graffiti penetration. The presence of silica nanoparticles did not have any significant effect on the surface free energy of the samples prior and after ageing.

  1. Probing Heterogeneity and Bonding at Silica Surfaces through Single-Molecule Investigation of Base-Mediated Linkage Failure.

    Science.gov (United States)

    Lupo, Katherine M; Hinton, Daniel A; Ng, James D; Padilla, Nicolas A; Goldsmith, Randall H

    2016-09-13

    The nature of silica surfaces is relevant to many chemical systems, including heterogeneous catalysis and chromatographies utilizing functionalized-silica stationary phases. Surface linkages must be robust to achieve wide and reliable applicability. However, silyl ether-silica support linkages are known to be susceptible to detachment when exposed to basic conditions. We use single-molecule spectroscopy to examine the rate of surface linkage failure upon exposure to base at a variety of deposition conditions. Kinetic analysis elucidates the role of thermal annealing and addition of blocking layers in increasing stability. Critically, it was found that successful surface modification strategies alter the rate at which base molecules approach the silica surface as opposed to reducing surface linkage reactivity. Our results also demonstrate that the innate structural diversity of the silica surface is likely the cause of observed heterogeneity in surface-linkage disruption kinetics.

  2. Birefringence Measurements on Crystalline Silicon

    CERN Document Server

    Krüger, Christoph; Khalaidovski, Alexander; Steinlechner, Jessica; Nawrodt, Ronny; Schnabel, Roman; Lück, Harald

    2015-01-01

    Crystalline silicon has been proposed as a new test mass material in third generation gravitational wave detectors such as the Einstein Telescope (ET). Birefringence can reduce the interferometric contrast and can produce dynamical disturbances in interferometers. In this work we use the method of polarisation-dependent resonance frequency analysis of Fabry-Perot-cavities containing silicon as a birefringent medium. Our measurements show a birefringence of silicon along the (111) axis of the order of $\\Delta\\, n \\approx 10^{-7}$ at a laser wavelength of 1550nm and room temperature. A model is presented that explains the results of different settings of our measurements as a superposition of elastic strains caused by external stresses in the sample and plastic strains possibly generated during the production process. An application of our theory on the proposed ET test mass geometry suggests no critical effect on birefringence due to elastic strains.

  3. Activation of NLRP3 inflammasome by crystalline structures via cell surface contact.

    Science.gov (United States)

    Hari, Aswin; Zhang, Yifei; Tu, Zhongyuan; Detampel, Pascal; Stenner, Melanie; Ganguly, Anutosh; Shi, Yan

    2014-12-02

    Crystalline structures activate the NLRP3 inflammasome, leading to the production of IL-1β, however, the molecular interactions responsible for NLRP3 activation are not fully understood. Cathepsin B release from the ruptured phagolysosome and potassium ion efflux have been suggested to be critical for this activation. Here, we report that Cathepsin B redistribution was not a crucial event in crystal-induced IL-1β production. Silica and monosodium urate crystal-treated macrophages with undisturbed lysosomes demonstrated strong co-localization of ASC and Caspase-1, indicative of NLRP3 inflammasome activation. Importantly, we provided evidence to suggest that macrophage cell membrane binding to immobilized crystals was sufficient to induce IL-1β release, and this activation of the NLRP3 inflammasome was inhibited by blocking potassium efflux. Therefore, this work reveals additional complexity in crystalline structure-mediated NLRP3 inflammasome regulations.

  4. Investigation of the nonlinear refractive index of single-crystalline thin gold films and plasmonic nanostructures

    Science.gov (United States)

    Goetz, Sebastian; Razinskas, Gary; Krauss, Enno; Dreher, Christian; Wurdack, Matthias; Geisler, Peter; Pawłowska, Monika; Hecht, Bert; Brixner, Tobias

    2016-04-01

    The nonlinear refractive index of plasmonic materials may be used to obtain nonlinear functionality, e.g., power-dependent switching. Here, we investigate the nonlinear refractive index of single-crystalline gold in thin layers and nanostructures on dielectric substrates. In a first step, we implement a z-scan setup to investigate ~100-µm-sized thin-film samples. We determine the nonlinear refractive index of fused silica, n 2(SiO2) = 2.9 × 10-20 m2/W, in agreement with literature values. Subsequent z-scan measurements of single-crystalline gold films reveal a damage threshold of 0.22 TW/cm2 and approximate upper limits of the real and imaginary parts of the nonlinear refractive index, | n 2'(Au)| film). An upper limit for the nonlinear power-dependent phase change between two propagating near-field modes is determined to Δ φ < 0.07 rad.

  5. Carbon in intimate contact with quartz reduces the biological activity of crystalline silica dusts.

    Science.gov (United States)

    Ghiazza, Mara; Tomatis, Maura; Doublier, Sophie; Grendene, Francesca; Gazzano, Elena; Ghigo, Dario; Fubini, Bice

    2013-01-18

    To evaluate the effect of carbonaceous materials on the pathogenic activity of quartz dusts, mixtures of carbon soot (1 and 10%) and quartz (Min-U-Sil) were prepared and then milled so to attain an intimate association of carbon and the quartz surface. Both cellular and cell-free tests show that carbon associated to quartz completely inhibits the typical free radical generation of quartz dusts (through Fenton activity and homolytic cleavage of a C-H bond) and suppresses the oxidative stress and inflammation induced by quartz alone on MH-S murine macrophage cells (lipid peroxidation, nitric oxide release, and tumor necrosis factor-α synthesis). The cytotoxic response to quartz is also largely reduced. An extremely pure quartz milled with 10% of soot showed inactivating effects on the adverse reactions to quartz similar to Min-U-Sil quartz. None of these effects takes place when the same experiments are carried out with mechanically mixed samples, which suggests that carbon acts not just as a radical quencher but because of its association to the quartz surface.

  6. Porous silicon nanocrystals in a silica aerogel matrix

    Science.gov (United States)

    Amonkosolpan, Jamaree; Wolverson, Daniel; Goller, Bernhard; Polisski, Sergej; Kovalev, Dmitry; Rollings, Matthew; Grogan, Michael D. W.; Birks, Timothy A.

    2012-07-01

    Silicon nanoparticles of three types (oxide-terminated silicon nanospheres, micron-sized hydrogen-terminated porous silicon grains and micron-size oxide-terminated porous silicon grains) were incorporated into silica aerogels at the gel preparation stage. Samples with a wide range of concentrations were prepared, resulting in aerogels that were translucent (but weakly coloured) through to completely opaque for visible light over sample thicknesses of several millimetres. The photoluminescence of these composite materials and of silica aerogel without silicon inclusions was studied in vacuum and in the presence of molecular oxygen in order to determine whether there is any evidence for non-radiative energy transfer from the silicon triplet exciton state to molecular oxygen adsorbed at the silicon surface. No sensitivity to oxygen was observed from the nanoparticles which had partially H-terminated surfaces before incorporation, and so we conclude that the silicon surface has become substantially oxidised. Finally, the FTIR and Raman scattering spectra of the composites were studied in order to establish the presence of crystalline silicon; by taking the ratio of intensities of the silicon and aerogel Raman bands, we were able to obtain a quantitative measure of the silicon nanoparticle concentration independent of the degree of optical attenuation.

  7. Nanoscale cellulose films with different crystallinities and mesostructures--their surface properties and interaction with water.

    Science.gov (United States)

    Aulin, Christian; Ahola, Susanna; Josefsson, Peter; Nishino, Takashi; Hirose, Yasuo; Osterberg, Monika; Wågberg, Lars

    2009-07-07

    A systematic study of the degree of molecular ordering and swelling of different nanocellulose model films has been conducted. Crystalline cellulose II surfaces were prepared by spin-coating of the precursor cellulose solutions onto oxidized silicon wafers before regeneration in water or by using the Langmuir-Schaefer (LS) technique. Amorphous cellulose films were also prepared by spin-coating of a precursor cellulose solution onto oxidized silicon wafers. Crystalline cellulose I surfaces were prepared by spin-coating wafers with aqueous suspensions of sulfate-stabilized cellulose I nanocrystals and low-charged microfibrillated cellulose (LC-MFC). In addition, a dispersion of high-charged MFC was used for the buildup of polyelectrolyte multilayers with polyetheyleneimine on silica with the aid of the layer-by-layer (LbL) technique. These preparation methods produced smooth thin films on the nanometer scale suitable for X-ray diffraction and swelling measurements. The surface morphology and thickness of the cellulose films were characterized in detail by atomic force microscopy (AFM) and ellipsometry measurements, respectively. To determine the surface energy of the cellulose surfaces, that is, their ability to engage in different interactions with different materials, they were characterized through contact angle measurements against water, glycerol, and methylene iodide. Small incidence angle X-ray diffraction revealed that the nanocrystal and MFC films exhibited a cellulose I crystal structure and that the films prepared from N-methylmorpholine-N-oxide (NMMO), LiCl/DMAc solutions, using the LS technique, possessed a cellulose II structure. The degree of crystalline ordering was highest in the nanocrystal films (approximately 87%), whereas the MFC, NMMO, and LS films exhibited a degree of crystallinity of about 60%. The N,N-dimethylacetamide (DMAc)/LiCl film possessed very low crystalline ordering (properties of the films, it was necessary to consider both the

  8. Quantum Monte Carlo computations of phase stability, equations of state, and elasticity of high-pressure silica.

    Science.gov (United States)

    Driver, K P; Cohen, R E; Wu, Zhigang; Militzer, B; Ríos, P López; Towler, M D; Needs, R J; Wilkins, J W

    2010-05-25

    Silica (SiO(2)) is an abundant component of the Earth whose crystalline polymorphs play key roles in its structure and dynamics. First principle density functional theory (DFT) methods have often been used to accurately predict properties of silicates, but fundamental failures occur. Such failures occur even in silica, the simplest silicate, and understanding pure silica is a prerequisite to understanding the rocky part of the Earth. Here, we study silica with quantum Monte Carlo (QMC), which until now was not computationally possible for such complex materials, and find that QMC overcomes the failures of DFT. QMC is a benchmark method that does not rely on density functionals but rather explicitly treats the electrons and their interactions via a stochastic solution of Schrödinger's equation. Using ground-state QMC plus phonons within the quasiharmonic approximation of density functional perturbation theory, we obtain the thermal pressure and equations of state of silica phases up to Earth's core-mantle boundary. Our results provide the best constrained equations of state and phase boundaries available for silica. QMC indicates a transition to the dense alpha-PbO(2) structure above the core-insulating D" layer, but the absence of a seismic signature suggests the transition does not contribute significantly to global seismic discontinuities in the lower mantle. However, the transition could still provide seismic signals from deeply subducted oceanic crust. We also find an accurate shear elastic constant for stishovite and its geophysically important softening with pressure.

  9. Bietti crystalline dystrophy and choroidal neovascularisation.

    Science.gov (United States)

    Gupta, B; Parvizi, S; Mohamed, M D

    2011-02-01

    Bietti crystalline dystrophy is a rare autosomal recessive condition characterised by the presence of crystals in the retina and is followed by retinal and choroidal degeneration. We present a novel finding of juxtafoveal choroidal neovascularisation in Bietti crystalline dystrophy and demonstrate a spectral domain optical coherence tomography image of this disorder.

  10. Ordered mesoporous silica: microwave synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Fantini, M.C.A. [IF-USP, CP 66318, 05315-970, Sao Paulo, SP (Brazil)]. E-mail: mfantini@if.usp.br; Matos, J.R. [IQ-USP, CP 26077, 05599-970, Sao Paulo, SP (Brazil); Silva, L.C. Cides da [IQ-USP, CP 26077, 05599-970, Sao Paulo, SP (Brazil); Mercuri, L.P. [IQSC-USP, CP 780, 13560-970, Sao Carlos, SP (Brazil); Chiereci, G.O. [IQSC-USP, CP 780, 13560-970, Sao Carlos, SP (Brazil); Celer, E.B. [Department of Chemistry, Kent State University, Kent, OH 44240 (United States); Jaroniec, M. [Department of Chemistry, Kent State University, Kent, OH 44240 (United States)

    2004-09-25

    Ordered mesoporous silicas, FDU-1, synthesized by using triblock copolymer, EO{sub 39}BO{sub 47}EO{sub 39}, as template were hydrothermally treated in a microwave oven at 373 K for different periods of time. The structural and morphological properties of these silicas were investigated by X-ray diffraction and nitrogen adsorption and compared with those for the FDU-1 samples prepared by conventional hydrothermal treatment at 373 K. All samples were calcined at 813 K in N{sub 2} and air. This procedure succeeded in producing ordered cage-like mesoporous structures even after 15 min of the microwave treatment. The best sample was obtained after 60 min of the microwave treatment, which is reflected by narrow pore size distribution, uniform pore size entrances and thick mesopore walls. Longer time of the microwave treatment increased nonuniformity of the pore entrance sizes as evidenced by changes in the hysteresis loops of nitrogen adsorption isotherms.

  11. Heavy ion irradiation of crystalline water ice

    CERN Document Server

    Dartois, E; Boduch, P; Brunetto, R; Chabot, M; Domaracka, A; Ding, J J; Kamalou, O; Lv, X Y; Rothard, H; da Silveira, E F; Thomas, J C

    2015-01-01

    Under cosmic irradiation, the interstellar water ice mantles evolve towards a compact amorphous state. Crystalline ice amorphisation was previously monitored mainly in the keV to hundreds of keV ion energies. We experimentally investigate heavy ion irradiation amorphisation of crystalline ice, at high energies closer to true cosmic rays, and explore the water-ice sputtering yield. We irradiated thin crystalline ice films with MeV to GeV swift ion beams, produced at the GANIL accelerator. The ice infrared spectral evolution as a function of fluence is monitored with in-situ infrared spectroscopy (induced amorphisation of the initial crystalline state into a compact amorphous phase). The crystalline ice amorphisation cross-section is measured in the high electronic stopping-power range for different temperatures. At large fluence, the ice sputtering is measured on the infrared spectra, and the fitted sputtering-yield dependence, combined with previous measurements, is quadratic over three decades of electronic ...

  12. Kinetic modeling of aldehyde adsorption rates on bare and aminopropylsilyl-modified silica gels by ultra-rapid-scanning fourier transform infrared spectrometry.

    Science.gov (United States)

    Yang, Husheng; Weinstock, Benjamin A; Hirsche, Blayne L; Griffiths, Peter R

    2005-04-26

    Enhancements of a model capable of precisely defining rates of adsorption in terms of a Langmuir isotherm and determined from infrared and pressure data collected in the millisecond time regime are described in detail. Rates of adsorption are determined for formaldehyde and acetaldehyde exposed to bare and aminopropylsilyl-derivatized silica gel. The model fits the collected data by varying the number of adsorption sites and the adsorption and desorption rate constants and determines the best fit based on the measured IR absorbance, partial pressure, exposure backpressure, number of adsorption sites, and time. The rate of adsorption onto irregular-shaped silica gel was faster than the rate onto the corresponding spherical silica gel. Formaldehyde was adsorbed more efficiently than acetaldehyde on APS silica gel than on bare silica gel, whereas acetaldehyde was adsorbed more efficiently than formaldehyde on underivatized silica, indicating the possibility that formaldehyde is adsorbed through the formation of a Schiff base.

  13. Rotational dynamics of magnetic silica spheres studied by measuring the complex magnetic susceptibility

    NARCIS (Netherlands)

    Claesson, E.M.; Erne, B.H.; Philipse, A.P.

    2007-01-01

    The weak permanent magnetic dipole moment of cobalt ferrite-doped colloidal silica spheres was increased by exposure to a saturating magnetic field. The resulting change of the rotational dynamics of the magnetic microspheres in a weak alternating field was measured from low to high volume fraction

  14. Shape Memory Properties of PBS-Silica Hybrids

    Directory of Open Access Journals (Sweden)

    Katia Paderni

    2014-01-01

    Full Text Available A series of novel Si–O–Si crosslinked organic/inorganic hybrid semi-crystalline polymers with shape memory properties was prepared from alkoxysilane-terminated poly(butylene succinate (PBS by water-induced silane crosslinking under organic solvent-free and catalyst-free conditions. The hydrolyzation and condensation of alkoxysilane end groups allowed for the generation of silica-like crosslinking points between the polymeric chains, acting not only as chemical net-points, but also as inorganic filler for a reinforcement effect. The resulting networks were characterized using differential scanning calorimetry (DSC, thermogravimetric analysis (TGA, dynamic-mechanical analysis (DMA and tensile and shape memory tests to gain insight into the relationship between the polymeric structure, the morphology and the properties. By controlling the molecular weight of the PBS precursor, a fine tuning of the crosslinking density and the inorganic content of the resulting network was possible, leading to different thermal, mechanical and shape memory properties. Thanks to their suitable morphology consisting of crystalline domains, which represent the molecular switches between the temporary and permanent shapes, and chemical net-points, which permit the shape recovery, the synthesized materials showed good shape memory characteristics, being able to fix a significant portion of the applied strain in a temporary shape and to restore their original shape above their melting temperature.

  15. Fabrication and characterization of bioactive glass-ceramic using soda–lime–silica waste glass

    Energy Technology Data Exchange (ETDEWEB)

    Abbasi, Mojtaba; Hashemi, Babak, E-mail: hashemib@shirazu.ac.ir

    2014-04-01

    Soda–lime–silica waste glass was used to synthesize a bioactive glass-ceramic through solid-state reactions. In comparison with the conventional route, that is, the melt-quenching and subsequent heat treatment, the present work is an economical technique. Structural and thermal properties of the samples were examined by X-ray diffraction (XRD) and differential thermal analysis (DTA). The in vitro test was utilized to assess the bioactivity level of the samples by Hanks' solution as simulated body fluid (SBF). Bioactivity assessment by atomic absorption spectroscopy (AAS) and scanning electron microscopy (SEM) was revealed that the samples with smaller amount of crystalline phase had a higher level of bioactivity. - Highlights: • A bioactive glass-ceramic was synthesized using soda–lime–silica waste glass. • Solid-state reaction method was used to synthesize bioactive glass-ceramic. • Ca{sub 2}Na{sub 2}Si{sub 3}O{sub 9} and CaNaPO{sub 4} were formed with a one-step thermal treatment condition. • The amounts of crystalline and amorphous phases influenced the bioactivity. • The sample with a smaller amount of the crystalline phase had a higher bioactivity.

  16. Diffusion in porous crystalline materials.

    Science.gov (United States)

    Krishna, Rajamani

    2012-04-21

    The design and development of many separation and catalytic process technologies require a proper quantitative description of diffusion of mixtures of guest molecules within porous crystalline materials. This tutorial review presents a unified, phenomenological description of diffusion inside meso- and micro-porous structures. In meso-porous materials, with pore sizes 2 nm < d(p) < 50 nm, there is a central core region where the influence of interactions of the molecules with the pore wall is either small or negligible; meso-pore diffusion is governed by a combination of molecule-molecule and molecule-pore wall interactions. Within micro-pores, with d(p) < 2 nm, the guest molecules are always under the influence of the force field exerted with the wall and we have to reckon with the motion of adsorbed molecules, and there is no "bulk" fluid region. The characteristics and physical significance of the self-, Maxwell-Stefan, and Fick diffusivities are explained with the aid of data obtained either from experiments or molecular dynamics simulations, for a wide variety of structures with different pore sizes and topology. The influence of adsorption thermodynamics, molecular clustering, and segregation on both magnitudes and concentration dependences of the diffusivities is highlighted. In mixture diffusion, correlations in molecular hops have the effect of slowing-down the more mobile species. The need for proper modeling of correlation effects using the Maxwell-Stefan formulation is stressed with the aid of examples of membrane separations and catalytic reactors.

  17. Silica Induced Early Fibrogenic Reaction in Lung of Mice Ameliorated by Nyctanthes arbortristis Extract

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Objective To investigate the pharmacological effect of Nyctanthes arbortristis (NAT) leaf extract in the prevention of lung injury induced by silica particles. Method Lung injury was induced in Swiss mice through inhalation exposure to silica particles (<5μ) using a Flow Past Nose Only Inhalation Chamber at the rate of -10 mg/m3 respirable mass for 5 h. Lung bronchoalveolar lavage (BAL) fluid collected between 48 and 72 h was subjected to protein profiling by electrophoresis and cytokine evaluation by solid phase sandwich ELISA. Lung histopathology was performed to evaluate lung injury. Results Inhalation of silica increased the level of tumor necrosis factor-α(TNF-α), and of the 66 and 63 kDa peptides in the BAL fluid in comparison to sham-treated control. Pre-treatment of silica exposed mice with NAT leaf extract significantly prevented the accumulation of TNF-α in the BAL fluid, but the 66 and 63 kDa peptides remained unchanged. The extract was also effective in the prevention of silica-induced early fibrogenic reactions like congestion, edema and infiltration of nucleated cells in the interstitial alveolar spaces, and thickening of alveolar septa in mouse lung. Conclusion NAT leaf extract helps in bypassing silica induced initial lung injury in mice.

  18. Preparation of polystyrene/silica nanocomposites by radical copolymerization of styrene with silica macromonomer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A two-stage process has been developed to generate the silica-based macromonomer through surface-modification of silica with polymerizable vinyl groups. The silica surfaces were treated with excess 2,4-toluene diisocynate (TDI), after which the residual isocyanate groups were converted into polymerizable vinyl groups by reaction with hydroxypropylacrylate (HPA). Thus, polystyrene/silica nanocomposites were prepared by conventional radical copolymerization of styrene with silica macromonomer. The main effecting factors, such as ratios of styrene to the macromonomer, together with polymerization time on the copolymerization were studied in detail. FTIR, DSC and TGA were utilized to characterize the nanocomposites. Experimental results revealed that the silica nanoparticles act as cross-linking points in the polystytene/silica nanocomposites, and the glass transition temperatures of the nanocomposites are higher than that of the corresponding pure polystyrene. The glass transition temperatures of nanocomposites increased with the increasing of silica contents, which were further ascertained by DSC.

  19. Preparation of polyamide 6/silica nanocomposites from silica surface initiated ring-opening anionic polymerization

    Directory of Open Access Journals (Sweden)

    2007-07-01

    Full Text Available Polyamide 6/silica nanocomposites were synthesized by in situ ring-opening anionic polymerization of ε-caprolactam in the presence of sodium caprolactamate as a catalyst and caprolactam-functionalized silica as an initiator. The initiator precursor, isocyanate-functionalized silica, was prepared by directly reacting commercial silica with excess toluene 2,4-diisocyanate. This polymerization was found to occur in a highly efficient manner at relatively low reaction temperature (170°C and short reaction times (6 h. FTIR spectroscopy was utilized to follow the introduction and consumption of isocyanate groups on the silica surface. Thermogravimetric analysis indicated that the polyamide 6 was successfully grown from the silica surface. Transmission electron microscopy was utilized to image polymer-functionalized silica, showing fine dispersion of silica particles and their size ranging from 20 to 40 nm.

  20. Insecticidal efficacy of silica gel with Juniperus oxycedrus ssp. oxycedrus (Pinales: Cupressaceae) essential oil against Sitophilus oryzae (Coleoptera: Curculionidae) and Tribolium confusum (Coleoptera: Tenebrionidae).

    Science.gov (United States)

    Athanassiou, Christos G; Kavallieratos, Nickolas C; Evergetis, Epameinondas; Katsoula, Anna-Maria; Haroutounian, Serkos A

    2013-08-01

    Laboratory bioassays were carried out to evaluate the effect of silica gel enhanced with the essential oil (EO) of Juniperus oxycedrus L. ssp. oxycedrus (Pinales: Cupressaceae) (derived from berry specimens from Greece) against adults of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae). For that purpose, a dry mixture consisting of 500 mg of silica gel that had absorbed 2.18 mg of EO (total weight: 502.18 mg) was tested at three doses; 0.125, 0.250, and 0.5 g/kg of wheat, corresponding to 125, 250, and 500 ppm, respectively, and silica gel alone at 0.5 g/kg of wheat corresponding to 500 ppm, at different exposure intervals (24 and 48 h and 7 and 14 d for S. oryzae; 24 and 48 h and 7, 14, and 21 d for T. confusum). The chemical content of the specific EO was determined by gas chromatography (GC)-mass spectrometry (MS) analyses indicating the presence of 31 constituents with myrcene and germacrene-D being the predominant compounds. The bioactivity results for S. oryzae indicated that 48 h of exposure in wheat resulted in an 82% mortality for treatment with 500 ppm of the enhanced silica gel. For 7 d of exposure, 100 and 98% of S. oryzae adults died when they were treated with 500 and 250 ppm of enhanced silica gel, respectively. At 14 d of exposure, all adults died both at 250 and 500 ppm of enhanced silica gel. At 48 h, 7 and 14 d of exposure significantly less S. oryzae adults died in wheat treated with silica gel alone than at 250 or 500 ppm of enhanced silica gel. In the case of T. confusum, at 7 d of exposure, mortality in wheat treated with silica gel only was significantly higher in comparison to the other treatments. At the 14 d of exposure mortality in wheat treated with 500 ppm of silica gel alone was significantly higher than 125 and 250 ppm of the enhanced silica gel. Similar trends were also noted at 21 d of exposure, indicating that there is no enhancement effect from the addition of

  1. Sealed silica pressure ampoules for crystal growth

    Science.gov (United States)

    Holland, L. R.

    1984-01-01

    The properties of vitreous silica and the mechanics of thick walled pressure vessels are reviewed with regard to the construction of sealed silica crucibles such as are used in the growth of mercury-cadmium telluride crystals. Data from destructive rupture tests are reported, failure modes discussed, and recommendations for design given. Ordinary commercial clear vitreous silica from flame fused quartz can withstand a surface stress of 20 MPa or more in this application.

  2. Mesoporous Silica: A Suitable Adsorbent for Amines

    Directory of Open Access Journals (Sweden)

    Abdollahzadeh-Ghom Sara

    2009-01-01

    Full Text Available Abstract Mesoporous silica with KIT-6 structure was investigated as a preconcentrating material in chromatographic systems for ammonia and trimethylamine. Its adsorption capacity was compared to that of existing commercial materials, showing its increased adsorption power. In addition, KIT-6 mesoporous silica efficiently adsorbs both gases, while none of the employed commercial adsorbents did. This means that KIT-6 Mesoporous silica may be a good choice for integrated chromatography/gas sensing micro-devices.

  3. Aging study of silica optical fibers under acid environment

    Science.gov (United States)

    Severin, I.; El Abdi, R.; Poulain, M.

    2005-05-01

    Optical fibers are key components in telecommunication technologies. Apart from optical specifications, optical fibers are expected to keep most of their physical properties for 10 to 20 years in current operating conditions. The reliability and the expected lifetime of optical links are closely related to the action of the chemical environment on the silica network. However, the coating also contributes largely to the mechanical properties of the fibers. The aim of this work was to study the strength and the mechanical behaviour of the silica optical fibers in an acid environment. A container with ammonium bifluoride acid salt was plunged into hot water at different temperatures (55° and 75°C). This emitted acid vapors which attacked the optical fibers for a period of 1 to 18 days. An aging study was performed on silica optical fibers with standard polyacrylate coating and with hermetic carbon coating. A dynamic two-point bending bench at different faceplate velocities (100, 200, 400 and 800 μm/s) was used. For comparison, the same dynamic measurements were also carried out on non-aged fibers. After acid vapor condensation, salt crystal deposits on the fibers were displayed using an electron scanning microscope. These crystals became visible to the naked eye from the 7th day post exposure.

  4. Probabilistic modeling of the flows and environmental risks of nano-silica

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yan; Kalinina, Anna; Sun, Tianyin; Nowack, Bernd, E-mail: nowack@empa.ch

    2016-03-01

    Nano-silica, the engineered nanomaterial with one of the largest production volumes, has a wide range of applications in consumer products and industry. This study aimed to quantify the exposure of nano-silica to the environment and to assess its risk to surface waters. Concentrations were calculated for four environmental (air, soil, surface water, sediments) and two technical compartments (wastewater, solid waste) for the EU and Switzerland using probabilistic material flow modeling. The corresponding median concentration in surface water is predicted to be 0.12 μg/l in the EU (0.053–3.3 μg/l, 15/85% quantiles). The concentrations in sediments in the complete sedimentation scenario were found to be the largest among all environmental compartments, with a median annual increase of 0.43 mg/kg·y in the EU (0.19–12 mg/kg·y, 15/85% quantiles). Moreover, probabilistic species sensitivity distributions (PSSD) were computed and the risk of nano-silica in surface waters was quantified by comparing the predicted environmental concentration (PEC) with the predicted no-effect concentration (PNEC) distribution, which was derived from the cumulative PSSD. This assessment suggests that nano-silica currently poses no risk to aquatic organisms in surface waters. Further investigations are needed to assess the risk of nano-silica in other environmental compartments, which is currently not possible due to a lack of ecotoxicological data. - Highlights: • We quantify the exposure of nano-silica to technical systems and the environment. • The median concentration in surface waters is predicted to be 0.12 μg/L in the EU. • Probabilistic species sensitivity distributions were computed for surface waters. • The risk assessment suggests that nano-silica poses no risk to aquatic organisms.

  5. MASS BALANCE OF SILICA IN STRAW FROM THE PERSPECTIVE OF SILICA REDUCTION IN STRAW PULP

    OpenAIRE

    Celil Atik; Saim Ates

    2012-01-01

    The high silica content of wheat straw is an important limiting factor for straw pulping. High silica content complicates processing and black liquor recovery, wears out factory installations, and lowers paper quality. Each section of wheat straw has different cells and chemical compositions and thus different silica content. In this work, the silica content of balled straw samples were examined according to their physical components, including internodes, nodes, leaves (sheath and blade), ra...

  6. INTERSTELLAR SILICATE DUST IN THE z = 0.89 ABSORBER TOWARD PKS 1830-211: CRYSTALLINE SILICATES AT HIGH REDSHIFT?

    Energy Technology Data Exchange (ETDEWEB)

    Aller, Monique C.; Kulkarni, Varsha P.; Som, Debopam [Department of Physics and Astronomy, University of South Carolina, 712 Main Street, Columbia, SC 29208 (United States); York, Donald G.; Welty, Daniel E. [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637 (United States); Vladilo, Giovanni, E-mail: ALLERM@mailbox.sc.edu [Osservatorio Astonomico di Trieste, Via Tiepolo 11, 34143 Trieste (Italy)

    2012-03-20

    We present evidence of a >10{sigma} detection of the 10 {mu}m silicate dust absorption feature in the spectrum of the gravitationally lensed quasar PKS 1830-211, produced by a foreground absorption system at redshift 0.886. We have examined more than 100 optical depth templates, derived from both observations of Galactic and extragalactic sources and laboratory measurements, in order to constrain the chemical structure of the silicate dust. We find that the best fit to the observed absorption profile is produced by laboratory crystalline olivine, with a corresponding peak optical depth of {tau}{sub 10} = 0.27 {+-} 0.05. The fit is slightly improved upon by including small contributions from additional materials, such as silica, enstatite, or serpentine, which suggests that the dust composition may consist of a blend of crystalline silicates. Combining templates for amorphous and crystalline silicates, we find that the fraction of crystalline silicates needs to be at least 95%. Given the rarity of extragalactic sources with such a high degree of silicate crystallinity, we also explore the possibility that the observed spectral features are produced by amorphous silicates in combination with other molecular or atomic transitions, or by foreground source contamination. While we cannot rule out these latter possibilities, they lead to much poorer profile fits than for the crystalline olivine templates. If the presence of crystalline interstellar silicates in this distant galaxy is real, it would be highly unusual, given that the Milky Way interstellar matter contains essentially only amorphous silicates. It is possible that the z = 0.886 absorber toward PKS 1830-211, well known for its high molecular content, has a unique star-forming environment that enables crystalline silicates to form and prevail.

  7. Silica deactivation of bead VOC catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Libanati, C.; Pereira, C.J. [Research Division, W. R. Grace and Co., Columbia, MD (United States); Ullenius, D.A. [Grace TEC Systems, De Pere, WI (United States)

    1998-01-15

    Catalytic oxidation is a key technology for controlling the emissions of Volatile Organic Compounds (VOCs) from industrial plants. The present paper examines the deactivation by silica of bead VOC catalysts in a flexographic printing application. Post mortem analyses of field-aged catalysts suggest that organosilicon compounds contained in the printing ink diffuse into the catalyst and deposit as silica particles in the micropores. Laboratory activity evaluation of aged catalysts suggests that silica deposition is non-selective and that silica masks the noble metal active site

  8. Cellular membrane trafficking of mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fang, I-Ju [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    This dissertation mainly focuses on the investigation of the cellular membrane trafficking of mesoporous silica nanoparticles. We are interested in the study of endocytosis and exocytosis behaviors of mesoporous silica nanoparticles with desired surface functionality. The relationship between mesoporous silica nanoparticles and membrane trafficking of cells, either cancerous cells or normal cells was examined. Since mesoporous silica nanoparticles were applied in many drug delivery cases, the endocytotic efficiency of mesoporous silica nanoparticles needs to be investigated in more details in order to design the cellular drug delivery system in the controlled way. It is well known that cells can engulf some molecules outside of the cells through a receptor-ligand associated endocytosis. We are interested to determine if those biomolecules binding to cell surface receptors can be utilized on mesoporous silica nanoparticle materials to improve the uptake efficiency or govern the mechanism of endocytosis of mesoporous silica nanoparticles. Arginine-glycine-aspartate (RGD) is a small peptide recognized by cell integrin receptors and it was reported that avidin internalization was highly promoted by tumor lectin. Both RGD and avidin were linked to the surface of mesoporous silica nanoparticle materials to investigate the effect of receptor-associated biomolecule on cellular endocytosis efficiency. The effect of ligand types, ligand conformation and ligand density were discussed in Chapter 2 and 3. Furthermore, the exocytosis of mesoporous silica nanoparticles is very attractive for biological applications. The cellular protein sequestration study of mesoporous silica nanoparticles was examined for further information of the intracellular pathway of endocytosed mesoporous silica nanoparticle materials. The surface functionality of mesoporous silica nanoparticle materials demonstrated selectivity among the materials and cancer and normal cell lines. We aimed to determine

  9. Practical Hydrogen Loading of Air Silica Fibres

    DEFF Research Database (Denmark)

    Sørensen, Henrik Rokkjær; Jensen, Jesper Bevensee; Jensen, Jesper Bo Damm

    2005-01-01

    A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown.......A method for hydrogen-loading air-silica optical fibres has been developed allowing out-diffusion times comparable to standard step-index fibres. Examples of the first grating written in Ge-doped air-silica fibres using a 266nm UV-laser are shown....

  10. Nanoporous silica membranes with high hydrothermal stability

    DEFF Research Database (Denmark)

    Boffa, Vittorio; Magnacca, Giualiana; Yue, Yuanzheng

    Despite the use of sol-gel derived nanoporous silica membranes in substitution of traditional separation processes is expected leading to vast energy savings, their intrinsic poor steam-stability hampers their application at an industrial level. Transition metal ions can be used as dopant...... to improve the stability of nanoporous silica structure. This work is a quantitative study on the impact of type and concentration of transition metal ions on the microporous structure and stability of amorphous silica-based membranes, which provides information on how to design chemical compositions...... and synthetic paths for the fabrication of silica-based membranes with a well accessible and highly stabile nanoporous structure...

  11. Heterogeneous Catalysis in Zeolites, Mesoporous Silica, and Metal-Organic Frameworks.

    Science.gov (United States)

    Liang, Jie; Liang, Zibin; Zou, Ruqiang; Zhao, Yanli

    2017-08-01

    Crystalline porous materials are important in the development of catalytic systems with high scientific and industrial impact. Zeolites, ordered mesoporous silica, and metal-organic frameworks (MOFs) are three types of porous materials that can be used as heterogeneous catalysts. This review focuses on a comparison of the catalytic activities of zeolites, mesoporous silica, and MOFs. In the first part of the review, the distinctive properties of these porous materials relevant to catalysis are discussed, and the corresponding catalytic reactions are highlighted. In the second part, the catalytic behaviors of zeolites, mesoporous silica, and MOFs in four types of general organic reactions (acid, base, oxidation, and hydrogenation) are compared. The advantages and disadvantages of each porous material for catalytic reactions are summarized. Conclusions and prospects for future development of these porous materials in this field are provided in the last section. This review aims to highlight recent research advancements in zeolites, ordered mesoporous silica, and MOFs for heterogeneous catalysis, and inspire further studies in this rapidly developing field. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Pure Silica Zeolite Beta Membrane: A Potential Low Dielectric Constant Material For Microprocessor Application

    Science.gov (United States)

    Fong, Yeong Yin; Bhatia, Subhash

    The semiconductor industry needs low dielectric constant (low k-value) materials for more advance microprocessor and chips by reducing the size of the device features. In fabricating these contents, a new material with lower k-value than conventional silica (k = 3.9-4.2) is needed in order to improve the circuit performance. The choice of the inorganic zeolite membrane is an attractive option for low k material and suitable for microprocessor applications. A pure silica zeolite beta membrane was synthesized and coated on non-porous stainless steel support using insitu crystallization in the presence of tetraethylammonium hydroxide, TEA (OH), as structure directing agent, fumed silica, HF and deionized water at pH value of 9. The crystallization was carried out for the duration of 14 days under hydrothermal conditions at 130°C. The membrane was characterized by thermogravimetric analysis (TGA), nitrogen adsorption and Scanning Electron Microscope (SEM). SEM results show a highly crystalline; with a truncated square bipyramidal morphology of pure silica zeolite beta membrane strongly adhered on the non-porous stainless steel support. In the present work, the k-value of the membrane was measured as 2.64 which make it suitable for the microprocessor applications.

  13. Studying the Effects of Adding Silica Sand Nanoparticles on Epoxy Based Composites

    Directory of Open Access Journals (Sweden)

    Tahir Ahmad

    2013-01-01

    Full Text Available The research about the preparation of submicron inorganic particles, once conducted in the past decade, is now leading to prepare polymer matrix composite (PMC reinforced with nanofillers. The objective of present research is to study the modified effects of reinforcement dispersion of nanoparticle silica in epoxy resin on the physical properties, mechanical and thermal behaviour, and the microstructure of resultant composites. Stirrer mixing associated with manual mixing of silica sand nanoparticles (developed in our earlier research (Ahmad and Mamat, 2012 into epoxy was followed by curing being the adopted technique to develop the subject nanocomposites. Experimental values showed that 15 wt.% addition of silica sand nanoparticles improves Young’s modulus of the composites; however, a reduction in tensile strength was also observed. Number of holes and cavities produced due to improper mixing turn out to be the main cause of effected mechanical properties. Addition of silica sand nanoparticles causes a reduction in degree of crystallinity of the nanocomposites as being observed in differential scanning calorimetry (DSC analysis.

  14. Concentration quenching and photostability in Eu(dbm){sub 3}phen embedded in mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Moretti, Elisa, E-mail: elisa.moretti@unive.it [Department of Molecular Sciences and Nanosystems, Università Ca' Foscari Venezia, Via Torino 155/B, 30172 Mestre Venezia (Italy); Talon, Aldo; Storaro, Loretta [Department of Molecular Sciences and Nanosystems, Università Ca' Foscari Venezia, Via Torino 155/B, 30172 Mestre Venezia (Italy); Le Donne, Alessia; Binetti, Simona [Department of Materials Science and Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 53, 20125 Milano (Italy); Benedetti, Alvise; Polizzi, Stefano [Department of Molecular Sciences and Nanosystems, Università Ca' Foscari Venezia, Via Torino 155/B, 30172 Mestre Venezia (Italy)

    2014-02-15

    Ordered mesoporous silica nanoparticles (MSNs) were impregnated with different loadings of the luminescent complex tris(dibenzoylmethane) mono(1,10-phenanthroline)europium(III) (Eu(dbm){sub 3}phen), with the aim of increasing the luminescence by avoiding concentration quenching and having mainly in mind the application as spectral converter for multi-crystalline silicon solar cells. The morphological, structural and luminescence properties of the impregnated silica nanoparticles were characterized by N{sub 2} physisorption, X-ray diffraction, transmission electron microscopy, infrared spectroscopy, UV–visible spectroscopy and photoluminescence excitation and emission measurements. Photostability was tested under 1 sun (1000 W/m{sup 2}) illumination for 24 h and the related effects were inspected by UV–visible and photoluminescence spectroscopies. Impregnation of the complex into 50–70 nm MSNs with pore size tailored around 2.9 nm depressed concentration quenching and allowed the use of complex loadings as high as 23 wt%. Sunlight irradiation caused a marked increase in the luminescence intensity. -- Highlights: • Mesoporous silica nanoparticles tailored to the size of Eu{sup 3+}(dbm){sub 3}phen molecules. • Concentration quenching avoided up to 23 wt% of Eu{sup 3+}(dbm){sub 3}phen/silica. • Sun irradiation increased luminescence intensity by two order of magnitudes.

  15. Preparation of Metalloporphyrin-Bound Superparamagnetic Silica Particles via "Click" Reaction.

    Science.gov (United States)

    Hollingsworth, Javoris V; Bhupathiraju, N V S Dinesh K; Sun, Jirun; Lochner, Eric; Vicente, M Graça H; Russo, Paul S

    2016-01-13

    A facile approach using click chemistry is demonstrated for immobilization of metalloporphyrins onto the surface of silica-coated iron oxide particles. Oleic-acid stabilized iron oxide nanocrystals were prepared by thermal decomposition of iron(III) acetylacetonate. Their crystallinity, morphology, and superparamagnetism were determined using X-ray diffraction, transmission electron microscopy, and a superconducting quantum interference device. Monodisperse core-shell particles were produced in the silica-coating of iron oxide via microemulsion synthesis. Surface modification of these particles was performed in two steps, which included the reaction of silica-coated iron oxide particles with 3-bromopropyltrichlorosilane, followed by azido-functionalization with sodium azide. Monoalkylated porphyrins were prepared using the Williamson ether synthesis of commercially available tetra(4-hydroxyphenyl) porphyrin with propargyl bromide in the presence of a base. (1)H NMR and matrix-assisted laser desorption ionization confirmed the identity of the compounds. The prepared monoalkyne porphyrins were zinc-metalated prior to their introduction to azide-functionalized, silica-coated iron oxide particles in the click reaction. X-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy were used to characterize the surface chemistry after each step in the reaction. In addition, particle size was determined using dynamic light scattering and microscopy. The presented methodology is versatile and can be extended to other photoreactive systems, such as phthalocyanines and boron-dipyrromethane, which may lead to new materials for optical, photonic, and biological applications.

  16. History of crystalline organic conductor

    Science.gov (United States)

    Murata, Keizo

    2017-05-01

    A brief view of crystalline organic conductor is presented. Since the discovery of TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane) in the mid 1970’s, pressure has been an indispensable tool to develop the physics of this field. From the aspect of charge transfer salt, TTF-TCNQ and its family was specified with partial charge transfer, two chain one-dimensional (1D) system, charge density wave (CDW) and commensurability. On the other hand, in (TMTSF)2X family (TMTSF: tetramethyltetraselenafulvalene, X: electron acceptor such as PF6, ClO4), complete charge transfer, one chain system, spin density wave (SDW), field-induced SDW, quantum Hall effect, superconductivity were discussed. Further, together with pressure itself, cooling rate was noticed to be important for low temperature properties. Recently, coming back to TTF-TCNQ family, i.e., HMTSF-TCNQ, whether or not field-induced CDW, instead of field-induced SDW, and quantum Hall effect is present was discussed (HMTSF: hexamethylene-tetraselenafulvalene). Whether or not the Fermiology in (TMTTF)2X under pressure is similar to that of (TMTSF)2X is discussed as well. In (BEDT-TTF)2X, new aspect of macroscopic polarization of α-(BEDT-TTF)2I3 related to charge order is described. At the end, in contrast to the charge transfer salts, non-charge transfer salt, that is, single component conductor is presented as a new possible example of Dirac cone, which was deeply studied by many researchers in α-(BEDT-TTF)2I3, together with the theoretical calculation of its magnetic susceptibility (BEDT-TTF: bisethylenedithia-tetrathiafulvalene).

  17. Determination the Level of Dust ond Free Silica in Air of Khaf Iron Stone Quarries

    Directory of Open Access Journals (Sweden)

    A Dadpour4

    2008-09-01

    Full Text Available Background and Objectives: Silica is an inorganic material that found in the nature in various forms. The hazards of crystal of silica or α-quartz (free silica is greater than other forms. Exposure to dust that contains free silica result to pulmonary injury and result to silicosis and death finally. The present research was conducted in order to evaluate the level of workers exposure to free silica in air of Khaf Iron stone quarries."nMaterials and methods: The exposure level to total and respiratory dust measured based on personal and environmental sampling methods and concentration of dust determined based on gravimetric method. For determination of amounts of free silica, dust samples analyses based on X-ray diffraction (XRD method, and results compared with standard levels."nResults: The maximum amount of total dust and free silica measured in stone breaking station (800±155mg/m3 and 26.11±6.7 mg/m3 and minimum of them measured in official and safeguarding station (8.28±2.2 mg/m3 and 0.012±0.0019 mg/m3. The maximum amount of respiratory dust and free silica measured in red mound digging number 1 (66.14±13.45 mg/m3 and 1.48±0.39 mg/m3 and minimum of them measured in air hammer machine station (5.26±2.62 mg/m3 and 0.01±0.005 mg/m3."nConclusion: Amount of total dust only in official and safeguarding station was lower than standard levels of Iran. Amount of respiratory dust in all stations was greater than Iran standard levels. Furthermore the level of respiratory free silica only in airy hammer machine station was lower than standard level of Iran. Regarding to this amounts it is so essential to that with applying different methods generation and emission of dust protected.

  18. The origin of the compressibility anomaly in amorphous silica: a molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Andrew M [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Sullivan, Lucy A [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Trachenko, Kostya [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Bruin, Richard P [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); White, Toby O H [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Dove, Martin T [Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ (United Kingdom); Tyer, Richard P [CCLRC Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Todorov, Ilian T [CCLRC Daresbury Laboratory, Daresbury, Warrington, Cheshire WA4 4AD (United Kingdom); Wells, Stephen A [Center for Biological Physics, Arizona State University, Bateman Physical Sciences Building, Tempe, AZ 85287-1504 (United States)

    2007-07-11

    We propose an explanation for the anomalous compressibility maximum in amorphous silica based on rigidity arguments. The model considers the fact that a network structure will be rigidly compressed in the high-pressure limit, and rigidly taut in the negative pressure limit, but flexible and hence softer at intermediate pressures. We validate the plausibility of this explanation by the analysis of molecular dynamics simulations. In fact this model is quite general, and will apply to any network solid, crystalline or amorphous; there are experimental indications that support this prediction. In contrast to other ideas concerning the compressibility maximum in amorphous silica, the model presented here does not invoke the existence of polyamorphic phase transitions in the glass phase.

  19. EFFECTS OF LIGHTWEIGHT MULLITE-SILICA RICH GLASS COMPOSITE AGGREGATES ON PROPERTIES OF CASTABLES

    Directory of Open Access Journals (Sweden)

    Li Y.

    2013-09-01

    Full Text Available Mullite-silica rich glass (MSRG composite is a material which is more efficient than chamotte for refractory utilization of clay. The effects of lightweight MSRG composite aggregate on the properties of refractory castables were studied by XRD, SEM and EDS, etc. Comparing with a common lightweight chamotte aggregate, it was found that the hot modulus of rupture, refractoriness under load and thermal shock resistance of the castable with lightweight MSRG aggregate were higher than those of the castable with a common lightweight chamotte aggregate because MSRG did not contain silica crystalline phases and contained a liquid phase with very high viscosity at high temperature. The castables with lightweight chamotte aggregate have higher thermal expansion because of existence of cristobalite and quartz, and have lower thermal conductivity because of higher porosity.

  20. Light-Induced Phosphorylation of Crystallins in the Retinal Pigment Epithelium

    Science.gov (United States)

    Lee, Hyunju; Chung, Hyewon; Lee, Sung Haeng; Jahng, Wan Jin

    2017-01-01

    Protein phosphorylations have essential regulatory roles in visual signaling. Previously, we found that phosphorylation of several proteins in the retina and the retinal pigment epithelium (RPE) is involved in anti-apoptotic signaling under oxidative stress conditions, including light exposure. In this study, we used a phosphoprotein enrichment strategy to evaluate the light-induced phosphoproteome of primary bovine RPE cells. Phosphoprotein-enriched extracts from bovine RPE cells exposed to light or dark conditions for 1 hour were separated by 2D SDS-PAGE. Serine and tyrosine phosphorylation were visualized by 2D phospho western blotting and specific phosphorylation sites were analyzed by tandem mass spectrometry. Light induced a marked increase in tyrosine phosphorylation of beta crystallin A3 and A4. The most abundant light-induced up-regulated phosphoproteins were crystallins of 15–25-kDa, including beta crystallin S and zeta crystallin. Phosphorylation of beta crystallin suggests an anti-apoptotic chaperone function in the RPE. Other chaperones, cytoskeletal proteins, and proteins involved in energy balance were expressed at higher levels in the dark. A detailed analysis of RPE phosphoproteins provides a molecular basis for understanding light-induced signal transduction and anti-apoptosis mechanisms. Our data indicates that phosphorylation of crystallins likely represents an important mechanism for RPE shielding from physiological and pathophysiological light-induced oxidative injury. PMID:21094180

  1. Dust exposure in Finnish foundries.

    Science.gov (United States)

    Siltanen, E; Koponen, M; Kokko, A; Engström, B; Reponen, J

    1976-01-01

    Dust measurements were made in 51 iron, 9 steel, and 8 nonferrous foundries, at which 4,316 foundrymen were working. The sampling lasted at least two entire shifts or work days continuously during various operations in each foundry. The dust samples were collected at fixed sites or in the breathing zones of the workers. The mass concentration was determined by weighing and the respirable dust fraction was separated by liquid sedimentation. The free silica content was determined by X-ray diffraction. In the study a total of 3,188 samples were collected in the foundries and 6,505 determinations were made in the laboratory. The results indicated a definite difference in the dust exposure during various operations. The highest dust exposures were found during furnace, cupola, and pouring ladle repair. During cleaning work, sand mixing, and shake-out operations excessive silica dust concentrations were also measured. The lowest dust concentrations were measured during melting and pouring operations. Moderate dust concentrations were measured during coremaking and molding operations. The results obtained during the same operations of iron and steel foundries were similar. The distribution of the workers into various exposure categories, the content of respirable dust and quartz, the correlation between respirable dust and total dust, and the correlation between respirable silica and total dust concentrations are discussed. Observations concerning dust suppression and control methods are briefly considered.

  2. Effects of prolonged inhalation of silica and olivine dusts on immune functions in the mouse. [Escherichia coli; Staphylococcus

    Energy Technology Data Exchange (ETDEWEB)

    Scheuchenzuber, W.J.; Eskew, M.L.; Zarkower, A.

    1985-12-01

    Immunologic responses determined in Balb/c mice following intermittent silica or olivine inhalations for 150, 300, or 570 days. Animals dust-exposed for 570 days were tested immediately postexposure, while those exposed for 150 or 300 days were tested immediately or were rested for 30 or 150 days as a measure of possible recovery from effects of the dust inhalations. Silica inhalation suppressed the number of specific plaque-forming cells (PFC) in the spleen produced in response to aerosolized Escherichia coli bacteria. When tested after 570 days, silica inhalation also reduced the ability of alveolar marcophages to phagocytize Staphylococcus auerus in vitro. Olivine inhalation also suppressed splenic PFCs and alveolar macrophage phagocytosis, but to a lesser degree than silica. In animals tested after 570 days of dust exposure, it was determined that the ability to lyse allogeneic tumor cells in vitro was impaired by olivine slightly more than by silica, while antibody-dependent cell-mediated cytotoxic and mitogenic responses by splenic lymphocytes were unchanged by inhalation of either dust. The effects of increased exposure periods, and of recovery periods after exposure, were confounded by age-related immunologic changes which were present after the longer exposures.

  3. Optical waveguides in hard crystalline materials

    NARCIS (Netherlands)

    Pollnau, M.

    2005-01-01

    The recent results of our research group and collaborators in the field of fabrication, characterization, and applications of optical waveguides in hard crystalline materials, specifically in sapphire and Ti:sapphire, are reviewed.

  4. Co-localization of iron binding on silica with p62/sequestosome1 (SQSTM1) in lung granulomas of mice with acute silicosis

    Science.gov (United States)

    Shimizu, Yasuo; Dobashi, Kunio; Nagase, Hiroyuki; Ohta, Ken; Sano, Takaaki; Matsuzaki, Shinichi; Ishii, Yoshiki; Satoh, Takahiro; Koka, Masashi; Yokoyama, Akihito; Ohkubo, Takeru; Ishii, Yasuyuki; Kamiya, Tomihiro

    2015-01-01

    The cellular mechanisms involved in the development of silicosis have not been fully elucidated. This study aimed to examine influence of silica-induced lung injury on autophagy. Suspensions of crystalline silica particles were administered transnasally to C57BL/6j mice. Immunohistochemical examination for Fas and p62 protein expression was performed using lung tissue specimens. Two-dimensional and quantitative analysis of silica deposits in the lungs were performed in situ using lung tissue sections by an in-air microparticle induced X-ray emission (in-air micro-PIXE) analysis system, which was based on irrradiation of specimens with a proton ion microbeam. Quantitative analysis showed a significant increase of iron levels on silica particles (assessed as the ratio of Fe relative to Si) on day 56 compared with day 7 (p<0.05). Fas and p62 were expressed by histiocytes in granulomas on day 7, and the expressions persisted for day 56. Fas- and p62-expressing histiocytes were co-localized in granulomas with silica particles that showed an increase of iron levels on silica particles in mouse lungs. Iron complexed with silica induces apoptosis, and may lead to dysregulations of autophagy in histiocytes of granulomas, and these mechanisms may contribute to granuloma development and progression in silicosis. PMID:25834305

  5. Self-arrangement of nanoparticles toward crystalline metal oxides with high surface areas and tunable 3D mesopores

    Science.gov (United States)

    Lee, Hyung Ik; Lee, Yoon Yun; Kang, Dong-Uk; Lee, Kirim; Kwon, Young-Uk; Kim, Ji Man

    2016-02-01

    We demonstrate a new design concept where the interaction between silica nanoparticles (about 1.5 nm in diameter) with titania nanoparticles (anatase, about 4 nm or 6 nm in diameter) guides a successful formation of mesoporous titania with crystalline walls and controllable porosity. At an appropriate solution pH (~1.5, depending on the deprotonation tendencies of two types of nanoparticles), the smaller silica nanoparticles, which attach to the surface of the larger titania nanoparticles and provide a portion of inactive surface and reactive surface of titania nanoparticles, dictate the direction and the degree of condensation of the titania nanoparticles, resulting in a porous 3D framework. Further crystallization by a hydrothermal treatment and subsequent removal of silica nanoparticles result in a mesoporous titania with highly crystalline walls and tunable mesopore sizes. A simple control of the Si/Ti ratio verified the versatility of the present method through the successful control of mean pore diameter in the range of 2-35 nm and specific surface area in the ranges of 180-250 m2 g-1. The present synthesis method is successfully extended to other metal oxides, their mixed oxides and analogues with different particle sizes, regarding as a general method for mesoporous metal (or mixed metal) oxides.

  6. In vivo human crystalline lens topography

    OpenAIRE

    Ortiz, Sergio; Pérez Merino, Pablo; Gambra, Enrique; Castro, Alberto; Marcos, Susana

    2012-01-01

    Custom high-resolution high-speed anterior segment spectral domain optical coherence tomography (OCT) was used to characterize three-dimensionally (3-D) the human crystalline lens in vivo. The system was provided with custom algorithms for denoising and segmentation of the images, as well as for fan (scanning) and optical (refraction) distortion correction, to provide fully quantitative images of the anterior and posterior crystalline lens surfaces. The method was tested on an artificial eye ...

  7. Revealing crystalline domains in a mollusc shell single-crystalline prism

    Science.gov (United States)

    Mastropietro, F.; Godard, P.; Burghammer, M.; Chevallard, C.; Daillant, J.; Duboisset, J.; Allain, M.; Guenoun, P.; Nouet, J.; Chamard, V.

    2017-09-01

    Biomineralization integrates complex processes leading to an extraordinary diversity of calcareous biomineral crystalline architectures, in intriguing contrast with the consistent presence of a sub-micrometric granular structure. Hence, gaining access to the crystalline architecture at the mesoscale, that is, over a few granules, is key to building realistic biomineralization scenarios. Here we provide the nanoscale spatial arrangement of the crystalline structure within the `single-crystalline' prisms of the prismatic layer of a Pinctada margaritifera shell, exploiting three-dimensional X-ray Bragg ptychography microscopy. We reveal the details of the mesocrystalline organization, evidencing a crystalline coherence extending over a few granules. We additionally prove the existence of larger iso-oriented crystalline domains, slightly misoriented with respect to each other, around one unique rotation axis, and whose shapes are correlated with iso-strain domains. The highlighted mesocrystalline properties support recent biomineralization models involving partial fusion of oriented nanoparticle assembly and/or liquid droplet precursors.

  8. Closed-system behaviour of the intra-crystalline fraction of amino acids in mollusc shells.

    Science.gov (United States)

    Penkman, K E H; Kaufman, D S; Maddy, D; Collins, M J

    2008-02-01

    When mollusc shells are analysed conventionally for amino acid geochronology, the entire population of amino acids is included, both inter- and intra-crystalline. This study investigates the utility of removing the amino acids that are most susceptible to environmental effects by isolating the fraction of amino acids encapsulated within mineral crystals of mollusc shells (intra-crystalline fraction). Bleaching, heating and leaching (diffusive loss) experiments were undertaken on modern and fossil Corbicula fluminalis, Margaritifera falcata, Bithynia tentaculata and Valvata piscinalis shells. Exposure of powdered mollusc shells to concentrated NaOCl for 48 h effectively reduced the amino acid content of the four taxa to a residual level, assumed to represent the intra-crystalline fraction. When heated in water at 140 degrees C for 24 h, only 1% of amino acids were leached from the intra-crystalline fraction of modern shells compared with 40% from whole shell. Free amino acids were more effectively retained in the intra-crystalline fraction, comprising 55% (compared with 18%) of the whole shell after 24 h at 140 degrees C. For fossil gastropods, the inter-shell variability in D/L values for the intra-crystalline fraction of a single-age population was reduced by 50% compared with conventionally analysed shells. In contrast, analysis of the intra-crystalline fraction of C. fluminalis does not appear to improve the results for this taxon, possibly due to variability in shell ultrastructure. Nonetheless, the intra-crystalline fraction in gastropods approximates a closed system of amino acids and appears to provide a superior subset of amino acids for geochronological applications.

  9. Facile transformation of superhydrophobicity to hydrophilicity by silica/poly(ɛ-caprolactone) composite film

    Science.gov (United States)

    Gao, Zhengxin; Zhai, Xianglin; Wang, Chengyu

    2015-12-01

    A smart surface with thermo-responsive wettability was fabricated on the cross section of wood with simple bench chemistry. The surface showed fast response between superhydrophobic and hydrophilic under different temperatures. The reversible wettability from superhydrophobicity to hydrophilicity can be easily achieved by adjusting the temperature between 25 and 60 °C. This reversible wettability is resulted from the synergistic effect of the crystallinity transition of the polymer coated on the surface and the optimized roughness controlled by the silica particles with different sizes. Furthermore, the modified wood surface showed an excellent chemical stability to corrosive liquids under ambient conditions.

  10. Synthesis of SiO2 nanopowders containing quartz and cristobalite phases from silica sands

    OpenAIRE

    Munasir; Triwikantoro .; Zainuri Mochamad; Darminto

    2015-01-01

    In this study, extraction and synthesis of SiO2 nanoparticles from silica sands have been conducted by means of two different methods, i.e. dry method (method 1) and hydrothermal process (method 2). The basic difference between the two methods is in the extraction step. The two methods were compared in terms of being more efficient, economical, and superior in obtaining SiO2 nanoparticles. The SiO2 nanoparticles were characterized in terms of phase purity, crystallinity, Si-O functional bondi...

  11. Crystalline Silicon Dielectrics for Superconducting Qubit Circuits

    Science.gov (United States)

    Hover, David; Peng, Weina; Sendelbach, Steven; Eriksson, Mark; McDermott, Robert

    2009-03-01

    Superconducting qubit energy relaxation times are limited by microwave loss induced by a continuum of two-level state (TLS) defects in the dielectric materials of the circuit. State-of-the-art phase qubit circuits employ a micron-scale Josephson junction shunted by an external capacitor. In this case, the qubit T1 time is directly proportional to the quality factor (Q) of the capacitor dielectric. The amorphous capacitor dielectrics that have been used to date display intrinsic Q of order 10^3 to 10^4. Shunt capacitors with a Q of 10^6 are required to extend qubit T1 times well into the microsecond range. Crystalline dielectric materials are an attractive candidate for qubit capacitor dielectrics, due to the extremely low density of TLS defects. However, the robust integration of crystalline dielectrics with superconducting qubit circuits remains a challenge. Here we describe a novel approach to the realization of high-Q crystalline capacitor dielectrics for superconducting qubit circuits. The capacitor dielectric is a crystalline silicon nanomembrane. We discuss characterization of crystalline silicon capacitors with low-power microwave transport measurements at millikelvin temperatures. In addition, we report progress on integrating the crystalline capacitor process with Josephson qubit fabrication.

  12. Active and passive silica waveguide integration

    DEFF Research Database (Denmark)

    Hübner, Jörg; Guldberg-Kjær, Søren Andreas

    2001-01-01

    in existing and future networks without affecting the power budget of the system. Silica on silicon technology offers a unique possibility to selectively dope sections of the integrated circuit with erbium where amplification is desired. Some techniques for active/passive integration are reviewed and a silica...

  13. Chemical immobilisation of humic acid on silica

    NARCIS (Netherlands)

    Koopal, L.K.; Yang, Y.; Minnaard, A.J.; Theunissen, P.L.M.; Riemsdijk, W.H. van

    1998-01-01

    Immobilisation of purified Aldrich humic acid (PAHA) on aminopropyl silica and glutaraldehyde-activated aminopropyl silica has been investigated. In general the humic acid is bound to the solid by both physical and chemical bonds. The physically adsorbed HA can be released to a large extent at high

  14. Magnetic core-shell silica particles

    NARCIS (Netherlands)

    Claesson, E.M.

    2007-01-01

    This thesis deals with magnetic silica core-shell colloids and related functionalized silica structures. Synthesis routes have been developed and optimized. The physical properties of these colloids have been investigated, such as the magnetic dipole moment, dipolar structure formation and

  15. Chemical immobilisation of humic acid on silica

    NARCIS (Netherlands)

    Koopal, L.K.; Yang, Y.; Minnaard, A.J.; Theunissen, P.L.M.; Riemsdijk, W.H. van

    1998-01-01

    Immobilisation of purified Aldrich humic acid (PAHA) on aminopropyl silica and glutaraldehyde-activated aminopropyl silica has been investigated. In general the humic acid is bound to the solid by both physical and chemical bonds. The physically adsorbed HA can be released to a large extent at high

  16. Silica-Immobilized Enzyme Reactors (Postprint)

    Science.gov (United States)

    2007-09-01

    Non-solubilized UDPGT from rat liver microsomes was covalently immobilized to a func- tionalized silica support by Schiff base chemistry and a number...activity within a day. GADPH isolated from rabbit was covalently immobilized to a wide-pore silica support by glutaraldehyde activation and Schiff - base chemistry

  17. Magnetic core-shell silica particles

    NARCIS (Netherlands)

    Claesson, E.M.

    2007-01-01

    This thesis deals with magnetic silica core-shell colloids and related functionalized silica structures. Synthesis routes have been developed and optimized. The physical properties of these colloids have been investigated, such as the magnetic dipole moment, dipolar structure formation and rotationa

  18. Photo-directed organization of silver nanoparticles in mesostructured silica and titania films

    Energy Technology Data Exchange (ETDEWEB)

    Destouches, N., E-mail: nathalie.destouches@univ-st-etienne.fr [Universite de Lyon (France); Battie, Y. [Universite de Lorraine, Laboratoire de Chimie Physique-Approche Multiechelle de Milieux Complexes (LCP-A2MC, EA4632) (France); Crespo-Monteiro, N. [Universite de Lyon (France); Chassagneux, F.; Bois, L. [Universite de Lyon, Laboratoire Multimateriaux et Interfaces (France); Bakhti, S.; Vocanson, F. [Universite de Lyon (France); Toulhoat, N.; Moncoffre, N. [Universite Lyon, IPNL, CNRS/IN2P3 (France); Epicier, T. [Materiaux, Ingenierie et Sciences (MATEIS), UMR 5510 CNRS, Universite de Lyon, INSA-Lyon (France)

    2013-01-15

    This paper quantifies the migration of silver contained within mesostructured hybrid silica films and mesoporous titania films under exposure to modulated light. This quantization allows to demonstrate that all of the initial silver salt can be concentrated and reduced in domains accumulating the higher photonic energy. Entirely reduced in the form of nanoparticles of few nanometers size embedded in the silica matrix, silver is then quite stable even under subsequent homogeneous exposures. It is also shown that thanks to the relatively slow nanoparticle growth, successive multiple exposures can be used to create complex 3D microstructures within silica films using a simple dual beam interferometer. In mesoporous titania films, the UV photo-growth of silver nanoparticles remains limited to the vicinity of the film interface because of the matrix absorption and cannot provide deep 3D patterns of silver nanoparticles. However, 2D refractive index patterns can be obtained under UV exposure, erased with visible light and updated thanks to a reversible photochromic behavior. In such films, opposite migration flows of silver species are proven under UV intensity gradient and homogeneous visible exposure.

  19. FABRICATION AND CHARACTERATION OF NANOPOROUS SILICA FILM

    Institute of Scientific and Technical Information of China (English)

    殷明志; 张良莹; 姚熹

    2003-01-01

    Colloidal silica sol is formed by a novel hydrolyzing procedure of tetraethyl-orthosilicate(TEOS) catalyzing with NH3*H2O in aqueous mediums. Glycerol, combining with the hydrolyzed intermediates of TEOS, controls growing of the silica particles; poly(vinyl-vinyl alcohol makes the colloidal silica sol with polymeric structure and spinning, thermal strain makes the gel silica film changed into a nanoporous structure with diameter ranging 50-150 nm. Morphologies of the nanoporous silica film have been characterized; the porosities (%) is 32-64; the average dielectric constant at 1MHz region is 2.0 and 2.1; the thermal conductivity is less than 0.8. Chemical mechanism of the sol-gel process is discussed.

  20. Stability and cytotoxicity of crystallin amyloid nanofibrils

    Science.gov (United States)

    Kaur, Manmeet; Healy, Jackie; Vasudevamurthy, Madhusudan; Lassé, Moritz; Puskar, Ljiljana; Tobin, Mark J.; Valery, Celine; Gerrard, Juliet A.; Sasso, Luigi

    2014-10-01

    Previous work has identified crystallin proteins extracted from fish eye lenses as a cheap and readily available source for the self-assembly of amyloid nanofibrils. However, before exploring potential applications, the biophysical aspects and safety of this bionanomaterial need to be assessed so as to ensure that it can be effectively and safely used. In this study, crude crystallin amyloid fibrils are shown to be stable across a wide pH range, in a number of industrially relevant solvents, at both low and high temperatures, and in the presence of proteases. Crystallin nanofibrils were compared to well characterised insulin and whey protein fibrils using Thioflavin T assays and TEM imaging. Cell cytotoxicity assays suggest no adverse impact of both mature and fragmented crystallin fibrils on cell viability of Hec-1a endometrial cells. An IR microspectroscopy study supports long-term structural integrity of crystallin nanofibrils.Previous work has identified crystallin proteins extracted from fish eye lenses as a cheap and readily available source for the self-assembly of amyloid nanofibrils. However, before exploring potential applications, the biophysical aspects and safety of this bionanomaterial need to be assessed so as to ensure that it can be effectively and safely used. In this study, crude crystallin amyloid fibrils are shown to be stable across a wide pH range, in a number of industrially relevant solvents, at both low and high temperatures, and in the presence of proteases. Crystallin nanofibrils were compared to well characterised insulin and whey protein fibrils using Thioflavin T assays and TEM imaging. Cell cytotoxicity assays suggest no adverse impact of both mature and fragmented crystallin fibrils on cell viability of Hec-1a endometrial cells. An IR microspectroscopy study supports long-term structural integrity of crystallin nanofibrils. Electronic supplementary information (ESI) available: ThT fluorescence graphs of buffers and solvents used for

  1. Precise size control over ultrafine rutile titania nanocrystallites in hierarchical nanotubular silica/titania hybrids with efficient photocatalytic activity.

    Science.gov (United States)

    Gu, Yuanqing; Huang, Jianguo

    2013-08-12

    Hierarchical-structured nanotubular silica/titania hybrids incorporated with particle-size-controllable ultrafine rutile titania nanocrystallites were realized by deposition of ultrathin titania sandwiched silica gel films onto each nanofiber of natural cellulose substances (e.g., common commercial filter paper) and subsequent flame burning in air. The rapid flame burning transforms the initially amorphous titania into rutile phase titania, and the silica gel films suppress the crystallite growth of rutile titania, thereby achieving nano-precise size regulation of ultrafine rutile titania nanocrystallites densely embedded in the silica films of the nanotubes. The average diameters of these nanocrystallites are adjustable in a range of approximately 3.3-16.0 nm by a crystallite size increment rate of about 2.4 nm per titania deposition cycle. The silica films transfer the electrons activated by crystalline titania and generate catalytic reactive species at the outer surface. The size-tuned ultrafine rutile titania nanocrystallites distributed in the unique hierarchical networks significantly improve the photocatalytic performance of the rutile phase titania, thereby enabling a highly efficient photocatalytic degradation of the methylene blue dye under ultraviolet light irradiation, which is even superior to the pure anatase-titania-based materials. The facile stepwise size control of the rutile titania crystallites described here opens an effective pathway for the design and preparation of fine-nanostructured rutile phase titania materials to explore potential applications.

  2. Large-Scale Synthesis and Systematic Photoluminescence Properties of Monolayer MoS2 on Fused Silica.

    Science.gov (United States)

    Wan, Yi; Zhang, Hui; Zhang, Kun; Wang, Yilun; Sheng, Bowen; Wang, Xinqiang; Dai, Lun

    2016-07-20

    Monolayer MoS2, with fascinating mechanical, electrical, and optical properties, has generated enormous scientific curiosity and industrial interest. Controllable and scalable synthesis of monolayer MoS2 on various desired substrates has significant meaning in both basic scientific research and device application. Recent years have witnessed many advances in the direct synthesis of single-crystalline MoS2 flakes or their polycrystalline aggregates on numerous diverse substrates, such as SiO2-Si, mica, sapphire, h-BN, and SrTiO3, etc. In this work, we used the dual-temperature-zone atmospheric-pressure chemical vapor deposition method to directly synthesize large-scale monolayer MoS2 on fused silica, the most ordinary transparent insulating material in daily life. We systematically investigated the photoluminescence (PL) properties of monolayer MoS2 on fused silica and SiO2-Si substrates, which have different thermal conductivity coefficients and thermal expansion coefficients. We found that there exists a stronger strain on monolayer MoS2 grown on fused silica, and the strain becomes more obvious as temperature decreases. Moreover, the monolayer MoS2 grown on fused silica exhibits the unique trait of a fractal shape with tortuous edges and has stronger adsorbability. The monolayer MoS2 grown on fused silica may find application in sensing, energy storage, and transparent optoelectronics, etc.

  3. Testing Silica Fume-Based Concrete Composites under Chemical and Microbiological Sulfate Attacks

    Directory of Open Access Journals (Sweden)

    Adriana Estokova

    2016-04-01

    Full Text Available Current design practices based on descriptive approaches to concrete specification may not be appropriate for the management of aggressive environments. In this study, the durability of cement-based materials with and without the addition of silica fume, subjected to conditions that leach calcium and silicon, were investigated. Chemical corrosion was simulated by employing various H2SO4 and MgSO4 solutions, and biological corrosion was simulated using Acidithiobacillus sp. bacterial inoculation, leading to disrupted and damaged surfaces; the samples’ mass changes were studied following both chemical and biological attacks. Different leaching trends were observed via X-ray fluorescence when comparing chemical with biological leaching. Lower leaching rates were found for concrete samples fortified with silica fume than those without silica fume. X-ray diffraction and scanning electron microscopy confirmed a massive sulfate precipitate formation on the concrete surface due to bacterial exposure.

  4. D. C. plasma-sprayed coatings of nano-structured alumina-titania-silica

    CERN Document Server

    Jiang Xian Liang

    2002-01-01

    nano-crystalline powders of omega(Al sub 2 O sub 3) = 95%, omega(TiO sub 2) = 3%, and omega(SiO sub 2) = 2%, were reprocessed into agglomerated particles for plasma spraying, by using consecutive steps of ball milling, slurry forming, spray drying, and heat treatment. D.C. plasma was used to spray the agglomerated nano-crystalline powders, and resultant coatings were deposited on the substrate of stainless steel. Scanning electron microscopy (SEM) was used to examine the morphology of the agglomerated powders and the cross section of the alumina-titania-silica coatings. Experimental results show that the agglomerated nano-crystalline particles are spherical, with a size from (10-90) mu m. The flow ability of the nano-crystalline powders is greatly improved after the reprocessing. The coatings deposited by the plasma spraying are mainly of nano-structure. Unlike conventional plasma-sprayed coatings, no laminar layer could be found in the nano-structured coatings. Although the nano-structured coatings have a lo...

  5. Silica sol-gel encapsulated methylotrophic yeast as filling of biofilters for the removal of methanol from industrial wastewater.

    Science.gov (United States)

    Kamanina, Olga A; Lavrova, Daria G; Arlyapov, Viacheslav A; Alferov, Valeriy A; Ponamoreva, Olga N

    2016-10-01

    This research suggests the use of new hybrid biomaterials based on methylotrophic yeast cells covered by an alkyl-modified silica shell as biocatalysts. The hybrid biomaterials are produced by sol-gel chemistry from silane precursors. The shell protects microbial cells from harmful effects of acidic environment. Potential use of the hybrid biomaterials based on methylotrophic yeast Ogataea polymorpha VKM Y-2559 encapsulated into alkyl-modified silica matrix for biofilters is represented for the first time. Organo-silica shells covering yeast cells effectively protect them from exposure to harmful factors, including extreme values of pH. The biofilter based on the organic silica matrix encapsulated in the methylotrophic yeast Ogataea polymorpha BKM Y-2559 has an oxidizing power of 3 times more than the capacity of the aeration tanks used at the chemical plants during methyl alcohol production. This may lead to the development of new and effective industrial wastewater treatment technologies.

  6. Increase in DNA damage in lymphocytes and micronucleus frequency in buccal cells in silica-exposed workers

    Directory of Open Access Journals (Sweden)

    Ajanta Halder

    2012-01-01

    Full Text Available The alkaline single cell gel electrophoresis (comet assay was applied to study the genotoxic properties of silica in human peripheral blood lymphocytes (PBL. The study was designed to evaluate the DNA damage of lymphocytes and the end points like micronuclei from buccal smears in a group of 45 workers, occupationally exposed to silica, from small mines and stone quarries. The results were compared to 20 sex and age matched normal individuals. There was a statistically significant difference in the damage levels between the exposed group and the control groups. The types of damages (type I -type 1V were used to measure the DNA damage. The numbers of micronuclei were higher in the silica-exposed population. The present study suggests that the silica exposure can induce lymphocyte DNA damage and produces significant variation of micronuclei in buccal smear.

  7. Thermal, structural and morphological properties of High Density Polyethylene matrix composites reinforced with submicron agro silica particles and Titania particles

    Directory of Open Access Journals (Sweden)

    Oluyemi O. Daramola

    2017-07-01

    Full Text Available HDPE—based composites samples filled with 2, 4, 6, 8 and 10 wt.% submicron agro-waste silica particles extracted from rice husk ash (RHA at constant 0.3 wt.% Titania loading were prepared using rapra single screw extruder at temperature of 200–230 °C. The extrudates were compressed with a laboratory carver press at a temperature of 230 °C for 10 min under applied pressure of 0.2 kPa and water cooled at 20 °C min−1. Thermal, structural and morphological properties of the composites were studied. The results of the thermogravimetric analysis (TGA revealed that the composites with 10 wt.% SiO2 have the best maximum thermal degradation temperature of 438.73 °C. The crystal structure of neat HDPE, and the siliceous composites developed revealed two obvious diffractive peaks of about 21.3° and 23.7° corresponding to typical crystal plane (1 1 0 and (2 0 0 of orthorhombic phase respectively. The diffractive peaks do not shift with the addition of silica particles; this clearly indicates that the addition of silica particles did not exert much effect on the crystalline structure of HDPE. There is no much difference in the interplanar distance (d-value. Lamellar thickness (L of HDPE increases with the addition of silica particles, which implies that silica particles aid the formation of more perfect crystals. Scanning electron microscopy studies indicated that there were chains inter diffusion and entanglement between HDPE matrix and the silica particles at lower weight fraction (2–4 wt.% of submicron silica particles which resulted into homogeneous dispersion of the particles within the matrix.

  8. A novel route for immobilization of oligonucleotides onto modified silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Kota Sreenivasa [Institute of Scientific and Industrial Research, Sanken, Osaka University, Osaka (Japan)]. E-mail: kotas_1999@yahoo.com; Rani, Sikhakolli Usha [Institute of Scientific and Industrial Research, Sanken, Osaka University, Osaka (Japan); Charyulu, Devarayapalli Kamakshaiah [Institute of Advanced Energy, Kyoto University, Gokasho, Uji (Japan); Kumar, Kamisetty Nagendra [Institute of Advanced Energy, Kyoto University, Gokasho, Uji (Japan); Lee, Bong-Kuk [Institute of Scientific and Industrial Research, Sanken, Osaka University, Osaka (Japan); Lee, Hea-Yeon [Institute of Scientific and Industrial Research, Sanken, Osaka University, Osaka (Japan); Kawai, Tomoji [Institute of Scientific and Industrial Research, Sanken, Osaka University, Osaka (Japan)

    2006-08-25

    A novel approach for immobilization of probe oligonucleotides that uses zirconium phosphate modified silica nanoparticles is proposed. The surface modification of nanoparticles was carried out in two stages. Initially binding of Zr{sup 4+} to the surface of silica nanoparticles and later treated with phosphoric acid for terminal phosphate groups. Oligonucleotide probes modified with amine group at 5'-end were strongly binds to the phosphate terminated silica nanoparticles with imidazole in presence of 0.1 mol L{sup -1} EDC [N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide], as phosphate groups are more reactive towards amine group. Various studies, i.e., synthesis of silica nanoparticles, their surface modification, probe immobilization, measurement of hybridization and effect of bovine serum albumin (BSA) were carried out during optimization of reaction conditions. The significant reduction in the background signal was observed by treating the probe modified silica nanoparticles with bovine serum albumin prior to hybridization. The probe modified silica nanoparticles were retained their properties and the hybridization was induced by exposure of single-stranded DNA (ssDNA) containing silica nanoparticles to the complementary DNA in solution. The decrease in the fluorescence signal for one mismatch and three mismatch was observed upon hybridization of probe with target DNAs, while there was no response for the random target ssDNA under the same experimental conditions. The intensity of fluorescence signal was linear to the concentration of target DNA ranging from 3.9 x 10{sup -9} to 3.0 x 10{sup -6} mol L{sup -1}. A detection limit of 1.22 x 10{sup -9} mol L{sup -1} of oligonucleotides can be estimated. The proposed hybridization assay is simple and possesses good analytical characteristics and it can provide an effective and efficient route in the development of DNA biosensors and biochips.

  9. Inhibitions by hydrogen-occluding silica microcluster to melanogenesis in human pigment cells and tyrosinase reaction.

    Science.gov (United States)

    Kato, Shinya; Saitoh, Yasukazu; Miwa, Nobuhiko

    2013-01-01

    We investigated the anti-melanogenetic efficacy of hydrogen-occluding silica microcluster (H2-Silica), which is a silsesquioxane-based compound with hydrogen interstitially embedded in a matrix of caged silica, against melanogenesis in HMV-II human melanoma cells and L-DOPA-tyrosinase reaction [EC1.14.18.1]. HMV-II cells were subjected to oxidative stress by ultraviolet ray-A (UVA) exposure of 3-times of 0.65 J/cm2 summed up to 1.95 J/cm2. After UVA irradiation, HMV-II cells were stimulated to produce melanin by 2.72-fold more abundantly than unirradiated control. When HMV-II cells were treated with H2-Silica of 20 ppm or kojic acid of 28.4 ppm before and after UVA-irradiation, the amount of melanin was repressed to 12.2% or 14.5% as compared to that of UVA-irradiated control, respectively. That is, H2-Silica exhibited a comparable efficacy to the whitening agent kojic acid. The H2-Silica could prevent melanogenesis in HMV-II cells by low-level doses at 1-10 ppm, and cell viability and apoptosis event did not change even by high-level doses at 100-1000 ppm. On the contrary, kojic acid was cytotoxic at the concentration of 14-28 ppm or more. By microscopic observation, H2-Silica suppressed such properties indicative of melanin-rich cells as cellular hypertrophy, cell process formation, and melanogenesis around the outside of nuclei. The enzymatic assay using L-DOPA and mushroom tyrosinase demonstrated that H2-Silica restrained UVA-mediated melanin formation owing to down-regulation of tyrosinase activity, which could be attributed to scavenging of free radicals and inhibition of L-DOPA-to-dopachrome oxidation by hydrogen released from H2-Silica. Thus H2-Silica has a potential to prevent melanin production against UVA and serves as a skin-lightening ingredient for supplements or cosmetics.

  10. Peak exposures to main components of ash and gaseous diesel exhausts in closed and open ash loading stations at biomass-fuelled power plants.

    Science.gov (United States)

    Laitinen, Juha; Koponen, Hanna; Sippula, Olli; Korpijärvi, Kirsi; Jumpponen, Mika; Laitinen, Sirpa; Aatamila, Marjaleena; Tissari, Jarkko; Karhunen, Tommi; Ojanen, Kari; Jokiniemi, Jorma; Korpinen, Leena

    2017-10-01

    Fly and bottom ashes are collected at power plants to reduce the environmental effects of energy production. However, handling the ashes causes health problems for operators, maintenance workers and truck drivers at the power plants. Hence, we evaluated ash loaders' peak inhalation exposures to the chemical components of ash and diesel exhausts in open and closed ash loading stations at biomass-fuelled combined heat and power plants. We also carried out chemical and morphological analyses of the ashes to evaluate their health hazard potential in order to find practical technical measures to reduce workers' exposure. On the basis of X-ray diffraction analyses, the main respirable crystalline ash compounds were SiO2, CaSO4, CaO, Ca2Al2SiO7, NaCl and Ca3Al2O6 in the fly ashes and SiO2, KAlSi3O8, NaAlSi3O8 and Ca2Al2SiO7 in the bottom ashes. The short-term exposure levels of respirable crystalline silica, inhalable inorganic dust, Cr, Mn, Ni and nitric oxide exceeded their Finnish eight hours occupational exposure limit values in the closed ash loading station. According to our observations, more attention should be paid to the ash-moistening process, the use of tank trucks instead of open cassette flatbed trucks, and the sealing of the loading line from the silo to the truck which would prevent spreading the ash into the air. The idling time of diesel trucks should also be limited, and ash loading stations should be equipped with exhaust gas ventilators. If working conditions make it impossible to keep to the OEL values, workers must use respirators and protect their eyes and skin. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Biomimetic synthesized chiral mesoporous silica: Structures and controlled release functions as drug carrier

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jing; Xu, Lu, E-mail: xl2013109@163.com; Yang, Baixue; Bao, Zhihong; Pan, Weisan; Li, Sanming, E-mail: li_sanming2013@163.com

    2015-10-01

    This work initially illustrated the formation mechanism of chiral mesoporous silica (CMS) in a brand new insight named biomimetic synthesis. Three kinds of biomimetic synthesized CMS (B-CMS, including B-CMS1, B-CMS2 and B-CMS3) were prepared using different pH or stirring rate condition, and their characteristics were tested with transmission electron microscope and small angle X-ray diffraction. The model drug indomethacin was loaded into B-CMS and drug loading content was measured using ultraviolet spectroscopy. The result suggested that pH condition influenced energetics of self-assembly process, mainly packing energetics of the surfactant, while stirring rate was the more dominant factor to determine particle length. In application, indomethacin loading content was measured to be 35.3%, 34.8% and 35.1% for indomethacin loaded B-CMS1, indomethacin loaded B-CMS2 and indomethacin loaded B-CMS3. After loading indomethacin into B-CMS carriers, surface area, pore volume and pore diameter of B-CMS carriers were reduced. B-CMS converted crystalline state of indomethacin to amorphous state, leading to the improved indomethacin dissolution. B-CMS1 controlled drug release without burst-release, while B-CMS2 and B-CMS3 released indomethacin faster than B-CMS1, demonstrating that the particle length, the ordered lever of multiple helixes, the curvature degree of helical channels and pore diameter greatly contributed to the release behavior of indomethacin loaded B-CMS. - Highlights: • Chiral mesoporous silica was synthesized using biomimetic method. • pH influenced energetics of self-assembly process of chiral mesoporous silica. • Stirring rate determined the particle length of chiral mesoporous silica. • Controlled release behaviors of chiral mesoporous silica varied based on structures.

  12. Dosimetric response for crystalline and nanostructured aluminium oxide to a high-current pulse electron beam.

    Science.gov (United States)

    Nikiforov, S V; Kortov, V S

    2014-11-01

    The main thermoluminescent (TL) and dosimetric properties of the detectors based on anion-defective crystalline and nanostructured aluminium oxide after exposure to a high-current pulse electron beam are studied. TL peaks associated with deep-trapping centres are registered. It is shown that the use of deep-trap TL at 200-600°С allows registering absorbed doses up to 750 kGy for single-crystalline detectors and those up to 6 kGy for nanostructured ones. A wide range of the doses registered, high reproducibility of the TL signal and low fading contribute to a possibility of using single-crystalline and nanostructured aluminium oxide for the dosimetry of high-current pulse electron beams.

  13. Improved Josephson Qubits incorporating Crystalline Silicon Dielectrics

    Science.gov (United States)

    Gao, Yuanfeng; Maurer, Leon; Hover, David; Patel, Umeshkumar; McDermott, Robert

    2010-03-01

    Josephson junction phase quibts are a leading candidate for scalable quantum computing in the solid state. Their energy relaxation times are currently limited by microwave loss induced by a high density of two-level state (TLS) defects in the amorphous dielectric films of the circuit. It is expected that the integration of crystalline, defect-free dielectrics into the circuits will yield substantial improvements in qubit energy relaxation times. However, the epitaxial growth of a crystalline dielectric on a metal underlayer is a daunting challenge. Here we describe a novel approach in which the crystalline silicon nanomembrane of a Silicon-on-Insulator (SOI) wafer is used to form the junction shunt capacitor. The SOI wafer is thermocompression bonded to the device wafer. The handle and buried oxide layers of the SOI are then etched away, leaving the crystalline silicon layer for subsequent processing. We discuss device fabrication issues and present microwave transport data on lumped-element superconducting resonators incorporating the crystalline silicon.

  14. A quantitative method for silica flux evaluation

    Science.gov (United States)

    Schonewille, R. H.; O'Connell, G. J.; Toguri, J. M.

    1993-02-01

    In the smelting of copper and copper/nickel concentrates, the role of silica flux is to aid in the removal of iron by forming a slag phase. Alternatively, the role of flux may be regarded as a means of controlling the formation of magnetite, which can severely hinder the operation of a furnace. To adequately control the magnetite level, the flux must react rapidly with all of the FeO within the bath. In the present study, a rapid method for silica flux evaluation that can be used directly in the smelter has been developed. Samples of flux are mixed with iron sulfide and magnetite and then smelted at a temperature of 1250 °C. Argon was swept over the reaction mixture and analyzed continuously for sulfur dioxide. The sulfur dioxide concentration with time was found to contain two peaks, the first one being independent of the flux content of the sample. A flux quality parameter has been defined as the height-to-time ratio of the second peak. The value of this parameter for pure silica is 5100 ppm/min. The effects of silica content, silica particle size, and silicate mineralogy were investigated. It was found that a limiting flux quality is achieved for particle sizes less than 0.1 mm in diameter and that fluxes containing feldspar are generally of a poorer quality. The relative importance of free silica and melting point was also studied using synthetic flux mixtures, with free silica displaying the strongest effect.

  15. Metal-silica sol-gel materials

    Science.gov (United States)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  16. Light-Induced Surface Patterning of Silica.

    Science.gov (United States)

    Kang, Hong Suk; Lee, Seungwoo; Choi, Jaeho; Lee, Hongkyung; Park, Jung-Ki; Kim, Hee-Tak

    2015-10-27

    Manipulating the size and shape of silica precursor patterns using simple far-field light irradiation and transforming such reconfigured structures into inorganic silica patterns by pyrolytic conversion are demonstrated. The key concept of our work is the use of an azobenzene incorporated silica precursor (herein, we refer to this material as azo-silane composite) as ink in a micromolding process. The moving direction of azo-silane composite is parallel to light polarization direction; in addition, the amount of azo-silane composite movement can be precisely determined by controlling light irradiation time. By exploiting this peculiar phenomenon, azo-silane composite patterns produced using the micromolding technique are arbitrarily manipulated to obtain various structural features including high-resolution size or sophisticated shape. The photoreconfigured patterns formed with azo-silane composites are then converted into pure silica patterns through pyrolytic conversion. The pyrolytic converted silica patterns are uniformly formed over a large area, ensuring crack-free formation and providing high structural fidelity. Therefore, this optical manipulation technique, in conjunction with the pyrolytic conversion process, opens a promising route to the design of silica patterns with finely tuned structural features in terms of size and shape. This platform for designing silica structures has significant value in various nanotechnology fields including micro/nanofluidic channel for lab-on-a-chip devices, transparent superhydrophobic surfaces, and optoelectronic devices.

  17. Probabilistic modeling of the flows and environmental risks of nano-silica.

    Science.gov (United States)

    Wang, Yan; Kalinina, Anna; Sun, Tianyin; Nowack, Bernd

    2016-03-01

    Nano-silica, the engineered nanomaterial with one of the largest production volumes, has a wide range of applications in consumer products and industry. This study aimed to quantify the exposure of nano-silica to the environment and to assess its risk to surface waters. Concentrations were calculated for four environmental (air, soil, surface water, sediments) and two technical compartments (wastewater, solid waste) for the EU and Switzerland using probabilistic material flow modeling. The corresponding median concentration in surface water is predicted to be 0.12 μg/l in the EU (0.053-3.3 μg/l, 15/85% quantiles). The concentrations in sediments in the complete sedimentation scenario were found to be the largest among all environmental compartments, with a median annual increase of 0.43 mg/kg · y in the EU (0.19-12 mg/kg · y, 15/85% quantiles). Moreover, probabilistic species sensitivity distributions (PSSD) were computed and the risk of nano-silica in surface waters was quantified by comparing the predicted environmental concentration (PEC) with the predicted no-effect concentration (PNEC) distribution, which was derived from the cumulative PSSD. This assessment suggests that nano-silica currently poses no risk to aquatic organisms in surface waters. Further investigations are needed to assess the risk of nano-silica in other environmental compartments, which is currently not possible due to a lack of ecotoxicological data.

  18. Rapid Sintering of Silica Xerogel Ceramic Derived from Sago Waste Ash Using Sub-millimeter Wave Heating with a 300 GHz CW Gyrotron

    Science.gov (United States)

    Aripin, Haji; Mitsudo, Seitaro; Sudiana, I. Nyoman; Tani, Shinji; Sako, Katsuhide; Fujii, Yutaka; Saito, Teruo; Idehara, Toshitaka; Sabchevski, Sliven

    2011-06-01

    In this paper, we present and discuss experimental results from a microwave sintering of a silica-glass ceramic, produced from a silica xerogel extracted from a sago waste ash. As a radiation source for the microwave heating a sub-millimeter wave gyrotron (Gyrotron FU CW I) with an output frequency of 300 GHz has been used. The powders of silica xerogel have been dry pressed and then sintered at temperatures ranging from 300°C to 1500°C. The influence of the sintering temperature on the technological properties such as porosity and bulk density was studied in detail. Furthermore, X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy have been used in order to study the structure of the produced silica glass-ceramics. It has been found that the silica xerogel crystallizes at a temperature of 800°C, which is about 200°C lower than the one observed in the conventional process. The silica xerogel samples sintered by their irradiation with a sub-millimeter wave at 900°C for 18 minutes are fully crystallized into a silica glass-ceramic with a density of about 2.2 g/cm3 and cristobalite as a major crystalline phase. The results obtained in this study allow one to conclude that the microwave sintering with sub-millimeter waves is an appropriate technological process for production of silica glass-ceramics from a silica xerogel and is characterized with such advantages as shorter times of the thermal cycle, lower sintering temperatures and higher quality of the final product.

  19. TRIMETHYLSILYLATED SILICA AS RHEOLOGY MODIFIER FOR SILICONE RESINS

    Institute of Scientific and Technical Information of China (English)

    Wei Huang; Ying Huang; Yunzhao Yu

    2000-01-01

    Trimethylsilylated silica was synthesized through hydrolytic condensation of tetraethoxysilane followed by trimethylsilylation. Rheological properties of the silicone resin with trimethylsilylated silica as modifier were studied. It turned out that the particle size of silica was important to the rheological behavior of the modified resin. Trimethylsilylated silica of medium particle size shows the strongest tendency of forming physical network in the resin.

  20. Controlled silica synthesis inspired by diatom silicon biomineralization

    NARCIS (Netherlands)

    Vrieling, EG; Sun, QY; Beelen, TPM; Hazelaar, S; Gieskes, WWC; van Santen, RA; Sommerdijk, NAJM

    2005-01-01

    Silica becomes increasingly used in chemical, pharmaceutical, and (nano)technological processes', resulting in an increased demand for well-defined silicas and silica-based materials. The production of highly structured silica from cheap starting materials and under ambient conditions, which is a ta

  1. Controlled silica synthesis inspired by diatom silicon biomineralization

    NARCIS (Netherlands)

    Vrieling, EG; Sun, QY; Beelen, TPM; Hazelaar, S; Gieskes, WWC; van Santen, RA; Sommerdijk, NAJM

    Silica becomes increasingly used in chemical, pharmaceutical, and (nano)technological processes', resulting in an increased demand for well-defined silicas and silica-based materials. The production of highly structured silica from cheap starting materials and under ambient conditions, which is a

  2. Silica Microcapsules Prepared by Interfacial Reaction Methods

    Institute of Scientific and Technical Information of China (English)

    M; Fujiwara; K; Shiokawa; Y; Nakahara

    2007-01-01

    1 Results Silica spherical particles with hollow structure are directly prepared by interfacial reaction methods using W/O/W emulsion (schematic diagram in Fig.1)[1].Fig.1 Silica microcapsule formationThe mixing of W/O emulsion consisting of sodium silicate solution (inner water phase) and n-hexane solution (oil phase) to outer water phase dissolving NH4HCO3 or other salts affords silica microcapsules.The critical feature of this method is the direct formation of hollow structure.Therefore,the core com...

  3. Structural changes in bunched crystalline ion beams

    CERN Document Server

    Bussmann, M; Schätz, T; Habs, D

    2003-01-01

    Measurements of the spatial distribution of bunched crystalline ion beams in the radio frequency quadrupole storage ring PALLAS are presented for different ratios of the longitudinal and the transverse confinement strengths. The length of highly elongated crystalline ion bunches and its dependence on the bunching voltage is compared to predictions for a one-dimensional ion string and three-dimensional space-charge-dominated beams. The length is found to be considerably shorter than that predicted by the models. Furthermore, the scaling of the length with the bunching voltage is shown to differ from the expected inverse cube root scaling. These differences can partially be attributed to the formation of a mixed crystalline structure. Additionally, a concise mapping of the structural transition from a string to a zig-zag configuration as a function of the ratio of the confinement strengths is presented, which in a similar way deviates from the predictions.

  4. Cooling and heating of crystalline ion beams

    CERN Document Server

    Schramm, U; Bussmann, M; Habs, D

    2003-01-01

    The crystallization of ion beams has recently been established in the rf quadrupole storage ring PALLAS (PAul Laser CooLing Acceleration System) for laser-cooled sup 2 sup 4 Mg sup + ion beams at an energy of about 1 eV. Yet, unexpectedly sharp constraints had to be met concerning the confinement strength and the longitudinal laser cooling rate. In this paper, related and up to now unseen heating mechanisms are pinpointed for crystalline beams. The weak but inevitable diffusive transverse heating associated with the laser cooling process itself is investigated, possibly allowing the future measurement of the latent heat of the ion crystal. As a function of the beam velocity, the influence of bending shear on the attainability of larger crystalline structures is presented. Finally, rf heating of crystalline beams of different structure is studied for discontinuous cooling.

  5. Bio-based liquid crystalline polyesters

    Science.gov (United States)

    Wilsens, Carolus; Rastogi, Sanjay; Dutch Collaboration

    2013-03-01

    The reported thin-film polymerization has been used as a screening method in order to find bio-based liquid crystalline polyesters with convenient melting temperatures for melt-processing purposes. An in depth study of the structural, morphological and chemical changes occurring during the ongoing polycondensation reactions of these polymers have been performed. Structural and conformational changes during polymerization for different compositions have been followed by time resolved X-ray and Infrared spectroscopy. In this study, bio-based monomers such as vanillic acid and 2,5-furandicarboxylic acid are successfully incorporated in liquid crystalline polyesters and it is shown that bio-based liquid crystalline polymers with high aromatic content and convenient processing temperatures can be synthesized. Special thanks to the Dutch Polymer Institute for financial support

  6. Liquid Crystalline Materials for Biological Applications.

    Science.gov (United States)

    Lowe, Aaron M; Abbott, Nicholas L

    2012-03-13

    Liquid crystals have a long history of use as materials that respond to external stimuli (e.g., electrical and optical fields). More recently, a series of investigations have reported the design of liquid crystalline materials that undergo ordering transitions in response to a range of biological interactions, including interactions involving proteins, nucleic acids, viruses, bacteria and mammalian cells. A central challenge underlying the design of liquid crystalline materials for such applications is the tailoring of the interface of the materials so as to couple targeted biological interactions to ordering transitions. This review describes recent progress toward design of interfaces of liquid crystalline materials that are suitable for biological applications. Approaches addressed in this review include the use of lipid assemblies, polymeric membranes containing oligopeptides, cationic surfactant-DNA complexes, peptide-amphiphiles, interfacial protein assemblies and multi-layer polymeric films.

  7. Structure and function of small heat shock/alpha-crystallin proteins: established concepts and emerging ideas.

    Science.gov (United States)

    MacRae, T H

    2000-06-01

    Small heat shock/alpha-crystallin proteins are defined by conserved sequence of approximately 90 amino acid residues, termed the alpha-crystallin domain, which is bounded by variable amino- and carboxy-terminal extensions. These proteins form oligomers, most of uncertain quaternary structure, and oligomerization is prerequisite to their function as molecular chaperones. Sequence modelling and physical analyses show that the secondary structure of small heat shock/alpha-crystallin proteins is predominately beta-pleated sheet. Crystallography, site-directed spin-labelling and yeast two-hybrid selection demonstrate regions of secondary structure within the alpha-crystallin domain that interact during oligomer assembly, a process also dependent on the amino terminus. Oligomers are dynamic, exhibiting subunit exchange and organizational plasticity, perhaps leading to functional diversity. Exposure of hydrophobic residues by structural modification facilitates chaperoning where denaturing proteins in the molten globule state associate with oligomers. The flexible carboxy-terminal extension contributes to chaperone activity by enhancing the solubility of small heat shock/alpha-crystallin proteins. Site-directed mutagenesis has yielded proteins where the effect of the change on structure and function depends upon the residue modified, the organism under study and the analytical techniques used. Most revealing, substitution of a conserved arginine residue within the alpha-crystallin domain has a major impact on quaternary structure and chaperone action probably through realignment of beta-sheets. These mutations are linked to inherited diseases. Oligomer size is regulated by a stress-responsive cascade including MAPKAP kinase 2/3 and p38. Phosphorylation of small heat shock/alpha-crystallin proteins has important consequences within stressed cells, especially for microfilaments.

  8. Photosensitivity and photoluminescence of Sn/Yb codoped silica optical fiber preform

    Institute of Scientific and Technical Information of China (English)

    Guanghui Chen; Yigang Li; Yaoji He; Liying Liu; Lei Xu; Wencheng Wang

    2009-01-01

    Sn/Yb codoped silica optical fiber preform is prepared by the modified chemical vapor deposition (MCVD) followed by the solution-doping method. Ultraviolet (UV) optical absorption, photoluminescence (PL) spectra under 978-nm laser diode (LD) pumping, and refractive index change after exposure to 266-nm laser pulses are obtained. There is only a little change in the PL spectra while a positive refractive index change up to 2×10-4 is observed after 30-min exposure to 266-nm laser pulses. The results show that both of the peculiar photosensitivity of Sn-doped silica and the gain property of Yb-doped silica fiber are preserved in the Sn/Yb codoped silica optical fiber preform. The experimental data suggest that the photosensitivity of the fiber preform under high energy density laser irradiation should be mainly due to the bond-breaking of oxygen deficient defects, while under relatively low energy density laser irradiation, the refractive index change probably originates from the photoconversion of optically active defects.

  9. Electronic processes in non-crystalline materials

    CERN Document Server

    Mott, Nevill Francis

    2012-01-01

    Since the first edition of this highly successful book the field saw many great developments both in experimental and theoretical studies of electrical properties of non-crystalline solids. It became necessary to rewrite nearly the whole book, while the aims of the second edition remained the same: to set out the theoretical concepts, to test them by comparison with experiment for a wide variety of phenomena, and to apply them to non-crystalline materials. Sir Nevill Mott shared the1977 Nobel Prize for Physics, awarded for his research work in this field. The reissue of this book as part of th

  10. Photochromism of 36-Armed Liquid Crystalline Dendrimer

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The photochromism of a 36-armed liquid crystalline dendrimer D6 was briefly described in this paper. The molar absorption coefficient, photoisomerization and photo back-isomerization of D6 in solution were investigated by UV/Vis absorption spectra. The results indicate that the photochromism and photo back-isomerization of D6 in chloroform (CHCl3) and tetrahydrofuran (THF) solutions are in accordance with the first order kinetics. The photochromism rate constants of D6 are 10-1 s-1, it is 107 times larger than that of side-chain liquid crystalline polymers containing the same azobenzene moieties.

  11. Used fuel disposition in crystalline rocks

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hadgu, Teklu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kalinina, Elena Arkadievna [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jerden, James L. [Argonne National Lab. (ANL), Argonne, IL (United States); Copple, Jacqueline M. [Argonne National Lab. (ANL), Argonne, IL (United States); Cruse, T. [Argonne National Lab. (ANL), Argonne, IL (United States); Ebert, W. [Argonne National Lab. (ANL), Argonne, IL (United States); Buck, E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Eittman, R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tinnacher, R. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tournassat, Christophe. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Davis, J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Viswanathan, H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chu, S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dittrich, T. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hyman, F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Karra, S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Makedonska, N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Reimus, P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Zavarin, Mavrik [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Joseph, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2016-09-01

    The U.S. Department of Energy Office of Nuclear Energy, Office of Fuel Cycle Technology established the Used Fuel Disposition Campaign (UFDC) in fiscal year 2010 (FY10) to conduct the research and development (R&D) activities related to storage, transportation and disposal of used nuclear fuel and high level nuclear waste. The objective of the Crystalline Disposal R&D Work Package is to advance our understanding of long-term disposal of used fuel in crystalline rocks and to develop necessary experimental and computational capabilities to evaluate various disposal concepts in such media.

  12. Liquid crystalline thermosetting polyimides. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Hoyt, A.E.; Huang, S.J. [Connecticut Univ., Storrs, CT (United States). Inst. of Materials Science

    1993-07-01

    Phase separation of rodlike reinforcing polymers and flexible coil matrix polymers is a common problem in formulating molecular composites. One way to reduce phase separation might be to employ liquid crystalline thermosets as the matrix material. In this work, functionally terminated polyimide oligomers which exhibit lyotropic liquid crystalline behavior were successfully prepared. Materials based on 2,2{prime}-bis(trifluoromethyl)-4,4{prime}-diaminobiphenyl and 3,3{prime},4,4{prime}-biphenylenetetra-carboxylic dianhydride have been synthesized and characterized.

  13. Exact Topological Twistons in Crystalline Polyethylene

    CERN Document Server

    Ventura, E; Bazeia, D

    2000-01-01

    We investigate the presence of topological twistons in crystalline polyethylene. We describe crystalline polyethylene with a model that couples the torsional and longitudinal degrees of freedom of the polymeric chain by means of a system of two real scalar fields. This model supports topological twistons, which are described by exact and stable topological solutions that appear when the interaction between torsional and longitudinal fields is polynomial, containing up to the sixth power in the fields. We calculate the energy of the topological twiston, and the result is in very good agreement with the value obtained via molecular simulation.

  14. Observation of atomic collisions in crystalline solids

    CERN Document Server

    Nelson, R S; Gevers, R

    2013-01-01

    The Observation of Atomic Collisions in Crystalline Solids presents a critical account of the more important experiments which have provided the basis for a better understanding of atomic collision phenomena in crystalline solids. Collisions have been divided into two artificial regimes; primary collisions which deal with the interaction of the incident particles with the solid, and secondary collisions which deal with those events which occur as a result of lattice atoms recoiling from primary encounters. Although the book is intended principally for the experimentalist some simple theoretica

  15. Monolithic aerogels with nanoporous crystalline phases

    Science.gov (United States)

    Daniel, Christophe; Guerra, Gaetano

    2015-05-01

    High porosity monolithic aerogels with nanoporous crystalline phases can be obtained from syndiotactic polystyrene and poly(2,6-dimethyl-1,4-phenylene)oxide thermoreversible gels by removing the solvent with supercritical CO2. The presence of crystalline nanopores in the aerogels based on these polymers allows a high uptake associated with a high selectivity of volatile organic compounds from vapor phase or aqueous solutions even at very low activities. The sorption and the fast kinetics make these materials particularly suitable as sorption medium to remove traces of pollutants from water and moist air.

  16. Neutralization of interleukin-17A delays progression of silica-induced lung inflammation and fibrosis in C57BL/6 mice

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ying; Li, Cuiying [Division of Pneumoconiosis, School of Public Health, China Medical University, Shenyang, Liaoning (China); Weng, Dong [Division of Pneumoconiosis, School of Public Health, China Medical University, Shenyang, Liaoning (China); Clinical Translational Research Center, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai (China); Song, Laiyu; Tang, Wen; Dai, Wujing; Yu, Ye; Liu, Fangwei; Zhao, Ming; Lu, Chunwei [Division of Pneumoconiosis, School of Public Health, China Medical University, Shenyang, Liaoning (China); Chen, Jie, E-mail: chenjie@mail.cmu.edu.cn [Division of Pneumoconiosis, School of Public Health, China Medical University, Shenyang, Liaoning (China)

    2014-02-15

    Silica exposure can cause lung inflammation and fibrosis, known as silicosis. Interleukin-17A (IL-17A) and Th17 cells play a pivotal role in controlling inflammatory diseases. However, the roles of IL-17A and Th17 cells in the progress of silica-induced inflammation and fibrosis are poorly understood. This study explored the effects of IL-17A on silica-induced inflammation and fibrosis. We used an anti-mouse IL-17A antibody to establish an IL-17A-neutralized mice model, and mice were exposed to silica to establish an experimental silicosis model. We showed that IL-17A neutralization delayed neutrophil accumulation and progression of silica-induced lung inflammation and fibrosis. IL-17A neutralization reduced the percentage of Th17 in CD4 + T cells, decreased IL-6 and IL-1β expression, and increased Tregs at an early phase of silica-induced inflammation. Neutralization of IL-17A delayed silica-induced Th1/Th2 immune and autoimmune responses. These results suggest that IL-17A neutralization alleviates early stage silica-induced lung inflammation and delays progression of silica-induced lung inflammation and fibrosis. Neutralization of IL-17A suppressed Th17 cell development by decreasing IL-6 and/or IL-1β and increased Tregs at an early phase of silica-induced inflammation. Neutralization of IL-17A also delayed the Th1/Th2 immune response during silica-induced lung inflammation and fibrosis. IL-17A may play a pivotal role in the early phase of silica-induced inflammation and may mediate the Th immune response to influence silica-induced lung inflammation and fibrosis in mice. - Highlights: • Neutralization of IL-17A alleviated silica-induced lung inflammation of early stage. • Neutralization of IL-17A decreased Th17 cells and increased Tregs. • IL-17A mediated the reciprocal relationship of Th17/Tregs by IL-6 and/or IL-1β. • Neutralization of IL-17A delayed silica-induced Th1/Th2 immune response. • Neutralization of IL-17A delayed silica-induced lung

  17. Monitoring annealing via carbon dioxide laser heating of defect populations in fused silica surfaces using photoluminescence microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Raman, R N; Matthews, M J; Adams, J J; Demos, S G

    2010-02-01

    Photoluminescence (PL) microscopy and spectroscopy under 266 nm and 355 nm laser excitation are explored as a means of monitoring defect populations in laser-modified sites on the surface of fused silica and their subsequent response to heating to different temperatures via exposure to a CO{sub 2} laser beam. Laser-induced temperature changes were estimated using an analytic solution to the heat flow equation and compared to changes in the PL emission intensity. The results indicate that the defect concentrations decrease significantly with increasing CO{sub 2} laser exposure and are nearly eliminated when the peak surface temperature exceeds the softening point of fused silica ({approx}1900K), suggesting that this method might be suitable for in situ monitoring of repair of defective sites in fused silica optical components.

  18. Ionoluminescence induced by swift heavy ions in silica and quartz: A comparative analysis

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Rey, D. [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid (UAM), Cantoblanco, E-28049 Madrid (Spain); Pena-Rodriguez, O., E-mail: ovidio.pena@uam.es [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid (UAM), Cantoblanco, E-28049 Madrid (Spain); Instituto de Optica, Consejo Superior de Investigaciones Cientificas (CSIC), C/ Serrano 121, E-28006 Madrid (Spain); Manzano-Santamaria, J. [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid (UAM), Cantoblanco, E-28049 Madrid (Spain); Euratom/CIEMAT Fusion Association, Madrid (Spain); Olivares, J. [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid (UAM), Cantoblanco, E-28049 Madrid (Spain); Instituto de Optica, Consejo Superior de Investigaciones Cientificas (CSIC), C/ Serrano 121, E-28006 Madrid (Spain); Munoz-Martin, A. [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid (UAM), Cantoblanco, E-28049 Madrid (Spain); Rivera, A. [Instituto de Fusion Nuclear, Universidad Politecnica de Madrid, C/ Jose Gutierrez Abascal 2, E-28006 Madrid (Spain); Agullo-Lopez, F. [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid (UAM), Cantoblanco, E-28049 Madrid (Spain)

    2012-09-01

    Ionoluminescence (IL) of the two SiO{sub 2} phases, amorphous silica and crystalline quartz, has been comparatively investigated in this work, in order to learn about the structural defects generated by means of ion irradiation and the role of crystalline order on the damage processes. Irradiations have been performed with Cl at 10 MeV and Br at 15 MeV, corresponding to the electronic stopping regime (i.e., where the electronic stopping power S{sub e} is dominant) and well above the amorphization threshold. The light-emission kinetics for the two main emission bands, located at 1.9 eV (652 nm) and 2.7 eV (459 nm), has been measured under the same ion irradiation conditions as a function of fluence for both, silica and quartz. The role of electronic stopping power has been also investigated and discussed within current views for electronic damage. Our experiments provide a rich phenomenological background that should help to elucidate the mechanisms responsible for light emission and defect creation.

  19. Fixed Bed Adsorption of Drugs on Silica Aerogel from Supercritical Carbon Dioxide Solutions

    Directory of Open Access Journals (Sweden)

    Giuseppe Caputo

    2013-01-01

    Full Text Available Supercritical adsorption coupled with the high adsorption capacity of silica aerogel allows the preparation of a new kind of delivery systems of poor water soluble drugs. In order to overcome drawbacks of conventional techniques where the use of liquid solvents can cause the fracture of aerogel porous structure, in this work a new adsorption process of drugs from a supercritical mixture is proposed. Adsorption takes place from a fluid solution of the drug in supercritical CO2 and ethanol as cosolvent. A fixed bed adsorption plant has been developed to allow fast mixing of fluid phase and effective contact in the adsorption column. The use of ethanol as cosolvent allows to overcome the limitation of supercritical adsorption due to low solubility of many drugs in supercritical CO2. Adsorption isotherms were measured for one-model substance, nimesulide, at 40°C, and breakthrough curve was experimentally obtained. The drug loading of the drug into silica aerogel was up to 9 wt%. The drug composite was characterized using scanning electron microscopy, and release kinetics of the adsorbed drug were also evaluated by in vitro dissolution tests. The dissolution of nimesulide from loaded aerogel is much faster than dissolution of crystalline nimesulide. Around 80% of nimesulide dissolves from the aerogel within 6 minutes, whereas dissolving 80% of the crystalline drug takes about 90 min.

  20. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tiwen [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Jia, Zhixin, E-mail: zxjia@scut.edu.cn [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Luo, Yuanfang; Jia, Demin [College of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Peng, Zheng [Agricultural Product Processing Research Institute, Chinese Academy of Tropical Agriculture Sciences, Zhanjiang 524001 (China)

    2015-02-15

    Highlights: • Substantiate the ring open reaction between Si-OH of silica and epoxy groups of ENR. • ENR can act as a bridge between NR and silica to enhance the interfacial interaction. • As a modifier, ENR gets the potential to be used in the tread of green tire for improving the wet skid resistance apparently. - Abstract: The epoxidized natural rubber (ENR) as an interfacial modifier was used to improve the mechanical and dynamical mechanical properties of NR/silica composites. In order to reveal the interaction mechanism between ENR and silica, the ENR/Silica model compound was prepared by using an open mill and the interfacial interaction of ENR with silica was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and stress–strain testing. The results indicated that the ring-opening reaction occurs between the epoxy groups of ENR chains and Si-OH groups on the silica surfaces and the covalent bonds are formed between two phases, which can improve the dispersion of silica in the rubber matrix and enhance the interfacial combination between rubber and silica. The ring-opening reaction occurs not only in vulcanization process but also in mixing process, meanwhile, the latter seems to be more important due to the simultaneous effects of mechanical force and temperature.

  1. Metalliferous sediment and a silica-hematite deposit within the Blanco fracture zone, Northeast Pacific

    Science.gov (United States)

    Hein, J.R.; Clague, D.A.; Koski, R.A.; Embley, R.W.; Dunham, R.E.

    2008-01-01

    A Tiburon ROV dive within the East Blanco Depression (EBD) increased the mapped extent of a known hydrothermal field by an order of magnitude. In addition, a unique opal-CT (cristobalite-tridymite)-hematite mound was discovered, and mineralized sediments and rock were collected and analyzed. Silica-hematite mounds have not previously been found on the deep ocean floor. The light-weight rock of the porous mound consists predominantly of opal-CT and hematite filaments, rods, and strands, and averages 77.8% SiO2 and 11.8% Fe2O3. The hematite and opal-CT precipitated from a low-temperature (???115?? C), strongly oxidized, silica- and iron-rich, sulfur-poor hydrothermal fluid; a bacterial mat provided the framework for precipitation. Samples collected from a volcaniclastic rock outcrop consist primarily of quartz with lesser plagioclase, smectite, pyroxene, and sulfides; SiO2 content averages 72.5%. Formation of these quartz-rich samples is best explained by cooling in an up-flow zone of silica-rich hydrothermal fluids within a low permeability system. Opal-A, opal-CT, and quartz mineralization found in different places within the EBD hydrothermal field likely reflects decreasing silica saturation and increasing temperature of the mineralizing fluid with increasing silica crystallinity. Six push cores recovered gravel, coarse sand, and mud mineralized variously by Fe or Mn oxides, silica, and sulfides. Total rare-earth element concentrations are low for both the rock and push core samples. Ce and Eu anomalies reflect high and low temperature hydrothermal components and detrital phases. A remarkable variety of types of mineralization occur within the EBD field, yet a consistent suite of elements is enriched (relative to basalt and unmineralized cores) in all samples analyzed: Ag, Au, S, Mo, Hg, As, Sb, Sr, and U; most samples are also enriched in Cu, Pb, Cd, and Zn. On the basis of these element enrichments, the EBD hydrothermal field might best be described as a base

  2. Anisotropic silica mesostructures for DNA encapsulation

    Indian Academy of Sciences (India)

    Aparna Ganguly; Ashok K Ganguli

    2013-04-01

    The encapsulation of biomolecules in inert meso or nanostructures is an important step towards controlling drug delivery agents. Mesoporous silica nanoparticles (MSN) are of immense importance owing to their high surface area, large pore size, uniform particle size and chemical inertness. Reverse micellar method with CTAB as the surfactant has been used to synthesize anisotropic mesoporous silica materials. We have used the anisotropic silica nanostructures for DNA encapsulation studies and observed a loading capacity of ∼8 g mg-1 of the sample. On functionalizing the pores of silica with amine group, the amount of DNA loaded on the rods decreases which is due to a reduction in the pore size upon grafting of amine groups.

  3. Silica Brick for Hot Blast Stove

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ 1 Scope This standard specifies the glossary and definition, marking, shape and dimension, technical requirements, test method, quality appraisal procedure, packing, label, transportation, storage and quality certification of silica brick for hot blast stove.

  4. Accelerated purification of colloidal silica sols

    Science.gov (United States)

    Bahnsen, E. B.; Garofalini, S.; Pechman, A.

    1979-01-01

    Accelerated purification process for colloidal sols using heat/deionization scheme, sharply reduces waiting time between deionization cycles from several months to a few days. Process produces same high purity silica sols as conventional methods.

  5. Amorphous silica scale in cooling waters

    Energy Technology Data Exchange (ETDEWEB)

    Midkiff, W.S.; Foyt, H.P.

    1976-01-01

    In 1968, most of the evaporation cooled recirculating water systems at Los Alamos Scientific Laboratory were nearly inoperable due to scale. These systems, consisting of cooling towers, evaporative water coolers, evaporative condensers, and air washers had been operated on continuous blowdown without chemical treatment. The feedwater contained 80 mg/l silica. A successful program of routine chemical addition in the make-up water was begun. Blends of chelants, dispersants and corrosion inhibitors were found to gradually remove old scale, prevent new scale, and keep corrosion to less than an indicated rate of one mil per year. An explanation has been proposed that amorphous silica by itself does not form a troublesome scale. When combined with a crystal matrix such as calcite, the resultant silica containing scale can be quite troublesome. Rapid buildup of silica containing scale can be controlled and prevented by preventing formation of crystals from other constituents in the water such as hardness or iron. (auth)

  6. Silicon Monoxide at 1 atm and Elevated Pressures: Crystalline or Amorphous?

    KAUST Repository

    AlKaabi, Khalid

    2014-03-05

    The absence of a crystalline SiO phase under ordinary conditions is an anomaly in the sequence of group 14 monoxides. We explore theoretically ordered ground-state and amorphous structures for SiO at P = 1 atm, and crystalline phases also at pressures up to 200 GPa. Several competitive ground-state P = 1 atm structures are found, perforce with Si-Si bonds, and possessing Si-O-Si bridges similar to those in silica (SiO2) polymorphs. The most stable of these static structures is enthalpically just a little more stable than a calculated random bond model of amorphous SiO. In that model we find no segregation into regions of amorphous Si and amorphous SiO2. The P = 1 atm structures are all semiconducting. As the pressure is increased, intriguing new crystalline structures evolve, incorporating Si triangular nets or strips and stishovite-like regions. A heat of formation of crystalline SiO is computed; it is found to be the most negative of all the group 14 monoxides. Yet, given the stability of SiO2, the disproportionation 2SiO (s) → Si(s)+SiO2(s) is exothermic, falling right into the series of group 14 monoxides, and ranging from a highly negative ΔH of disproportionation for CO to highly positive for PbO. There is no major change in the heat of disproportionation with pressure, i.e., no range of stability of SiO with respect to SiO2. The high-pressure SiO phases are metallic. © 2014 American Chemical Society.

  7. Exposure Forecaster

    Data.gov (United States)

    U.S. Environmental Protection Agency — The Exposure Forecaster Database (ExpoCastDB) is EPA's database for aggregating chemical exposure information and can be used to help with chemical exposure...

  8. Anomalous enthalpy relaxation in vitreous silica

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    2015-01-01

    scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here, we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy...... the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica....

  9. UK silica sand resources for fracking

    OpenAIRE

    Mitchell, Clive

    2013-01-01

    UK silica sand resources for fracking Clive Mitchell, Industrial Minerals Specialist, British Geological Survey, Keyworth, Nottingham, NG12 5GG Email: Silica sand is high purity quartz sand that is mainly used for glass production, as foundry sand, in horticulture, leisure and other industrial uses. One specialist use is as a ‘proppant’ to enhance oil and gas recovery. This presentation will focus on this application, particularly for shale gas recovery where it is mo...

  10. Vibrating reed experiments on compacted vitreous silica

    Science.gov (United States)

    Weiss, G.; Daum, A.; Sohn, M.; Arndt, J.

    1996-02-01

    We have studied the acoustic properties of irreversibly compacted vitreous silica (Suprasil I) at frequencies around 12 kHz between 10 mK and room temperature. At low temperatures up to a few K the compacted glass exhibits acoustic properties similar to those of normal vitreous silica, however, with considerably smaller values of the damping and of the temperature coefficient of the sound velocity. Around 30 K the internal friction is reduced by factor of 6.

  11. A reexamination of the chemisorption of trimethylaluminum on silica

    Energy Technology Data Exchange (ETDEWEB)

    Bartram, M.E.; Michalske, T.A.; Rogers, J.W. Jr. (Sandia National Lab., Albuquerque, NM (United States))

    1991-05-30

    Fourier transform infrared spectroscopy, temperature-programmed desorption, and X-ray photoelectron spectroscopy have been used to study the chemisorption and decomposition of trimethylaluminum (TMA) on silica under high vacuum. By annealing a series of silica substrates from 425 to 1,573 K prior to TMA exposures at 300 K, the authors have examined the distributions of chemisorption products as a function of the relative concentrations of isolated hydroxyls (OH{sub i}), hydrogen-bonded hydroxyls (OH{sub H}), and siloxane bridges. The observed variation in the Si-methyl to Al-methyl population ratios supports a new chemisorption model in which a monomethylaluminum surface complex and methyl groups bonded to silicon are proposed as the majority species on the surface at 300 K. Although the initial reactive sticking probability for TMA on the silica substrates is < 0.01 at 300 K, TMA chemisorption affects OH{sub i}, OH{sub H}, and siloxane bridges on the surface with equivalent probability. The common reaction probability (equivalent rate constants) implies that similar requirements may be involved in the reactive adsorption that consumes each site. Decomposition of the monomethylaluminum adsorbate begins above 373 K and increases the population of methyl groups bonded to silicon on the surface. The methyl groups react to form methane{sub g} and ethane{sub g} and adsorbed hydrocarbon fragments. In addition, the methyl groups also react further with the surface to form tetramethylsilane{sub g}. At coverages of one-third saturation and greater, the monomethylaluminum surface complex can also react with methyl groups to yield TMA{sub g} above 500 K.

  12. The moisture outgassing kinetics of a silica reinforced polydimethylsiloxane

    Science.gov (United States)

    Sharma, H. N.; McLean, W.; Maxwell, R. S.; Dinh, L. N.

    2016-09-01

    A silica-filled polydimethylsiloxane (PDMS) composite M9787 was investigated for potential outgassing in a vacuum/dry environment with the temperature programmed desorption/reaction method. The outgassing kinetics of 463 K vacuum heat-treated samples, vacuum heat-treated samples which were subsequently re-exposed to moisture, and untreated samples were extracted using the isoconversional and constrained iterative regression methods in a complementary fashion. Density functional theory (DFT) calculations of water interactions with a silica surface were also performed to provide insight into the structural motifs leading to the obtained kinetic parameters. Kinetic analysis/model revealed that no outgassing occurs from the vacuum heat-treated samples in subsequent vacuum/dry environment applications at room temperature (˜300 K). The main effect of re-exposure of the vacuum heat-treated samples to a glove box condition (˜30 ppm by volume of H2O) for even a couple of days was the formation, on the silica surface fillers, of ˜60 ppm by weight of physisorbed and loosely bonded moisture, which subsequently outgasses at room temperature in a vacuum/dry environment in a time span of 10 yr. However, without any vacuum heat treatment and even after 1 h of vacuum pump down, about 300 ppm by weight of H2O would be released from the PDMS in the next few hours. Thereafter the outgassing rate slows down substantially. The presented methodology of using the isoconversional kinetic analysis results and some appropriate nature of the reaction as the constraints for more accurate iterative regression analysis/deconvolution of complex kinetic spectra, and of checking the so-obtained results with first principle calculations such as DFT can serve as a template for treating other complex physical/chemical processes as well.

  13. Synthesis and characterization of Ni NPs-doped silica-titania nanocomposites: structural, optical and photocatalytic properties

    Science.gov (United States)

    Islam, S.; Bidin, N.; Osman, S. S.; Krishnan, G.; Salim, A. A.; Riaz, S.; Suan, L. P.; Naseem, S.; Sanagi, M. M.

    2017-01-01

    The synthesis of Ni-doped silica-titania nanocomposite is performed by sol-gel method. The samples prior and after heat treatment at 300 °C for 1 h are characterized by analytical instrumental techniques. FE-SEM and AFM results indicate the regular morphology with low surface roughness without any cracks. EDX analysis verifies the formation of nanocomposites. XRD of the films reveals crystalline titania phases after annealing at 300 °C. The FTIR confirms the bond linkage between silica, titania and nickel molecules. High surface area 155 m2/g, pore volume of 0.2 cm3/g and pore diameter of 48.10 Å are obtained after heat treatment. The magnetic results show that the composite content is reminiscent of ferromagnetic hysteresis loop, with remanence magnetization Mr of 45.35 and 13.20 emu/g for both samples. The organic dye phenol red is used for the evaluation of photocatalytic activity of the synthesized magnetic material. The homogeneous surface morphology, crystalline nature, good solubility of magnetic nanoparticles into the silica-titania matrix show that the Ni/SiO2-TiO2 magnetic photocatalyst can be efficient and reusable.

  14. Structural Control of Mesoporous 1,4-Phenylene-silica Using the Mixture of CTAB/SDS

    Institute of Scientific and Technical Information of China (English)

    Zhuang Wei; Bi Lifeng; Zhang Ming; Wang Sibing; Li Yi; Li Baozong; Yang Yonggang

    2011-01-01

    The morphology, pore architecture and crystallinity of the mesoporous 1,4-phenylene-silicas were controlled using the mixtures of cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfate (SDS). When the SDS/CTAB molar ratio increased from 0 to 1.0, the morphology of the mesoporous 1,4-phenylene-silicas changed in a sequence of sphere, hexagonal short rod, worm-like, bent flake and flower-like structure; the pore architecture of them changed from a hexagonal arranged tubular structure to a lamellar one; and the organization of the smallest repeat units within the wall changed from a random structure to a crystalline structure. At the SDS/CTAB molar ra-tios of 0.3 and 0.5, 1,4-phenylene-silica nanofibers with lamellar mesopores outside and tubular pore channels in-side were obtained. The lamellar mesopores should be formed by merging the rod-like miceUes during the reaction process.

  15. Anomalous Enthalpy Relaxation in Vitreous Silica

    Directory of Open Access Journals (Sweden)

    Yuanzheng eYue

    2015-08-01

    Full Text Available It is a challenge to calorimetrically determine the glass transition temperature (Tg of vitreous silica. Here we demonstrate that this challenge mainly arises from the extreme sensitivity of the Tg to the hydroxyl content in vitreous silica, but also from the irreversibility of its glass transition when repeating the calorimetric scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling has impact on enthalpy relaxation in glass. Here we find that vitreous silica (as a strong system exhibits striking anomalies in both glass transition and enthalpy relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica.

  16. Microporous Silica Based Membranes for Desalination

    Directory of Open Access Journals (Sweden)

    João C. Diniz da Costa

    2012-09-01

    Full Text Available This review provides a global overview of microporous silica based membranes for desalination via pervaporation with a focus on membrane synthesis and processing, transport mechanisms and current state of the art membrane performance. Most importantly, the recent development and novel concepts for improving the hydro-stability and separating performance of silica membranes for desalination are critically examined. Research into silica based membranes for desalination has focussed on three primary methods for improving the hydro-stability. These include incorporating carbon templates into the microporous silica both as surfactants and hybrid organic-inorganic structures and incorporation of metal oxide nanoparticles into the silica matrix. The literature examined identified that only metal oxide silica membranes have demonstrated high salt rejections under a variety of feed concentrations, reasonable fluxes and unaltered performance over long-term operation. As this is an embryonic field of research several target areas for researchers were discussed including further improvement of the membrane materials, but also regarding the necessity of integrating waste or solar heat sources into the final process design to ensure cost competitiveness with conventional reverse osmosis processes.

  17. Complex coacervation between colloidal silica and polyacrylamide

    Energy Technology Data Exchange (ETDEWEB)

    Kawase, Kaoru; Sakami, Hiroshi; Hayakawa, Kiyoshi

    1989-03-01

    Complex coacervation introduced by gamma-ray induced polymerization of acrylamide in colloidal silica was studied. The complex coaservate was formed by polymerization of acrylamide dissolved in a colloidal silica and methanol mixture. Complex coacervation (two-phase separation of the mixture) was observed only when the concentration of methanol was between 33 and 41 percent by volume, and the concentration of colloidal silica did not affect it. Although two phase separation was not influenced by pH change, the content of polyacrylamide was bigger in the equilibrated solution in acidic regions. It was, however, bigger in the complex coacervate at neutral and in alkaline regions. The content of polyacrylamide was also calculated from the particle diameter of complex coacervate measured by small angle X-ray scattering, and the result was well coincided with the analytical result. The stability of the complex coacervate against the addition of salts was better than that of the untreated colloidal silica. The rate of electrophoretic transport of the complex coacervate was also lower than that of the colloidal silica. From these observation it was concluded that the hydrophobic colloidal silica particles were protected by the surrounding hydrophilic polyacrylamide. (author).

  18. Agmatine attenuates silica-induced pulmonary fibrosis.

    Science.gov (United States)

    El-Agamy, D S; Sharawy, M H; Ammar, E M

    2014-06-01

    There is a large body of evidence that nitric oxide (NO) formation is implicated in mediating silica-induced pulmonary fibrosis. As a reactive free radical, NO may not only contribute to lung parenchymal tissue injury but also has the ability to combine with superoxide and form a highly reactive toxic species peroxynitrite that can induce extensive cellular toxicity in the lung tissues. This study aimed to explore the effect of agmatine, a known NO synthase inhibitor, on silica-induced pulmonary fibrosis in rats. Male Sprague Dawley rats were treated with agmatine for 60 days following a single intranasal instillation of silica suspension (50 mg in 0.1 ml saline/rat). The results revealed that agmatine attenuated silica-induced lung inflammation as it decreased the lung wet/dry weight ratio, protein concentration, and the accumulation of the inflammatory cells in the bronchoalveolar lavage fluid. Agmatine showed antifibrotic activity as it decreased total hydroxyproline content of the lung and reduced silica-mediated lung inflammation and fibrosis in lung histopathological specimen. In addition, agmatine significantly increased superoxide dismutase (p pulmonary nitrite/nitrate as well as tumor necrosis factor α. Collectively, these results demonstrate the protective effects of agmatine against the silica-induced lung fibrosis that may be attributed to its ability to counteract the NO production, lipid peroxidation, and regulate cytokine effects.

  19. Influence of Silica Fume on Normal Concrete

    Directory of Open Access Journals (Sweden)

    Debabrata Pradhan

    2013-09-01

    Full Text Available The incorporation of silica fume into the normal concrete is a routine one in the present days to produce the tailor made high strength and high performance concrete. The design parameters are increasing with the incorporation of silica fume in conventional concrete and the mix proportioning is becoming complex. The main objective of this paper has been made to investigate the different mechanical properties like compressive strength, compacting factor, slump of concrete incorporating silica fume. In this present paper 5 (five mix of concrete incorporating silica fume are cast to perform experiments. These experiments were carried out by replacing cement with different percentages of silica fume at a single constant water-cementitious materials ratio keeping other mix design variables constant. The silica fume was replaced by 0%, 5%, 10%, 15% and 20% for water-cementitious materials (w/cm ratio for 0.40. For all mixes compressive strengths were determined at 24 hours, 7 and 28 days for 100 mm and 150 mm cubes. Other properties like compacting factor and slump were also determined for five mixes of concrete.

  20. Grassy Silica Nanoribbons and Strong Blue Luminescence

    Science.gov (United States)

    Wang, Shengping; Xie, Shuang; Huang, Guowei; Guo, Hongxuan; Cho, Yujin; Chen, Jun; Fujita, Daisuke; Xu, Mingsheng

    2016-09-01

    Silicon dioxide (SiO2) is one of the key materials in many modern technological applications such as in metal oxide semiconductor transistors, photovoltaic solar cells, pollution removal, and biomedicine. We report the accidental discovery of free-standing grassy silica nanoribbons directly grown on SiO2/Si platform which is commonly used for field-effect transistors fabrication without other precursor. We investigate the formation mechanism of this novel silica nanostructure that has not been previously documented. The silica nanoribbons are flexible and can be manipulated by electron-beam. The silica nanoribbons exhibit strong blue emission at about 467 nm, together with UV and red emissions as investigated by cathodoluminescence technique. The origins of the luminescence are attributed to various defects in the silica nanoribbons; and the intensity change of the blue emission and green emission at about 550 nm is discussed in the frame of the defect density. Our study may lead to rational design of the new silica-based materials for a wide range of applications.

  1. Mesoporous Silica from Rice Husk Ash

    Directory of Open Access Journals (Sweden)

    V.R. Shelke

    2011-01-01

    Full Text Available Mesoporous silica is used as a raw material in several areas: in preparation of catalysts, in inks, as a concrete hardening accelerator, as a component of detergents and soaps, as a refractory constituent etc. Sodium silicate is produced by reacting rice hull ash (RHA with aqueous NaOH and silica is precipitated from the sodium silicate by acidification. In the present work, conversion of about 90% of silica contained in RHA into sodium silicate was achieved in an open system at temperatures of about 100 °C. The results showed that silica obtained from RHA is mesoporous, has a large surface area and small particle size. Rice Husk is usually mixed with coal and this mixture is used for firing boilers. The RHA therefore, usually contains carbon particles. Activated carbon embedded on silica has been prepared using the carbon already present in RHA. This carbon shows good adsorption capacity. ©2010 BCREC UNDIP. All rights reserved(Received: 25th April 2010, Revised: 17th June 2010, Accepted: 24th June 2010[How to Cite: V.R. Shelke, S.S. Bhagade, S.A. Mandavgane. (2010. Mesoporous Silica from Rice Husk Ash. Bulletin of Chemical Reaction Engineering and Catalysis, 5 (2: 63-67. doi:10.9767/bcrec.5.2.793.63-67][DOI: http://dx.doi.org/10.9767/bcrec.5.2.793.63-67

  2. Silica Derived from Burned Rice Hulls

    Directory of Open Access Journals (Sweden)

    M.F. de Souza

    2002-10-01

    Full Text Available Three new processes to obtain silica having high specific surface area from burned pre-treated rice hulls are presented and discussed. These procedures allow for the simultaneous recovery of biomass energy and the production of high quality silica at thermoelectric plants, without the risk of using corrosive substances in the burning process. The first method involves treatment of the hull with hot organic acid solutions before burning, the second with boiling water, both using an autoclave at temperatures close to150 °C, while the third method renders the hull fragile by treating it at 250 °C and reducing it to a fine powder before burning. The first two methods result in white amorphous silica that can show 500 m²/g of specific surface area. The third method, which does not remove the alkaline elements from the hull, produces an amorphous gray carbon-free powder whose specific surface area can be as high as 250 m²/g. An investigation of the specific surface area of the prepared silica indicates the alkaline elements are not mixed with silica in the hulls or combined as insoluble compounds. A comparison is made of these processes and the dissolution of silica by sodium hydroxide solutions is discussed.

  3. Grassy Silica Nanoribbons and Strong Blue Luminescence

    Science.gov (United States)

    Wang, Shengping; Xie, Shuang; Huang, Guowei; Guo, Hongxuan; Cho, Yujin; Chen, Jun; Fujita, Daisuke; Xu, Mingsheng

    2016-01-01

    Silicon dioxide (SiO2) is one of the key materials in many modern technological applications such as in metal oxide semiconductor transistors, photovoltaic solar cells, pollution removal, and biomedicine. We report the accidental discovery of free-standing grassy silica nanoribbons directly grown on SiO2/Si platform which is commonly used for field-effect transistors fabrication without other precursor. We investigate the formation mechanism of this novel silica nanostructure that has not been previously documented. The silica nanoribbons are flexible and can be manipulated by electron-beam. The silica nanoribbons exhibit strong blue emission at about 467 nm, together with UV and red emissions as investigated by cathodoluminescence technique. The origins of the luminescence are attributed to various defects in the silica nanoribbons; and the intensity change of the blue emission and green emission at about 550 nm is discussed in the frame of the defect density. Our study may lead to rational design of the new silica-based materials for a wide range of applications. PMID:27666663

  4. Hollow silica spheres: synthesis and mechanical properties.

    Science.gov (United States)

    Zhang, Lijuan; D'Acunzi, Maria; Kappl, Michael; Auernhammer, Günter K; Vollmer, Doris; van Kats, Carlos M; van Blaaderen, Alfons

    2009-03-03

    Core-shell polystyrene-silica spheres with diameters of 800 nm and 1.9 microm were synthesized by soap-free emulsion and dispersion polymerization of the polystyrene core, respectively. The polystyrene spheres were used as templates for the synthesis of silica shells of tunable thickness employing the Stöber method [Graf et al. Langmuir 2003, 19, 6693]. The polystyrene template was removed by thermal decomposition at 500 degrees C, resulting in smooth silica shells of well-defined thickness (15-70 nm). The elastic response of these hollow spheres was probed by atomic force microscopy (AFM). A point load was applied to the particle surface through a sharp AFM tip, and successively increased until the shell broke. In agreement with the predictions of shell theory, for small deformations the deformation increased linearly with applied force. The Young's modulus (18 +/- 6 GPa) was about 4 times smaller than that of fused silica [Adachi and Sakka J. Mater. Sci. 1990, 25, 4732] but identical to that of bulk silica spheres (800 nm) synthesized by the Stöber method, indicating that it yields silica of lower density. The minimum force needed to irreversibly deform (buckle) the shell increased quadratically with shell thickness.

  5. Epidemiology of environmental exposures and human autoimmune diseases: findings from a National Institute of Environmental Health Sciences Expert Panel Workshop.

    Science.gov (United States)

    Miller, Frederick W; Alfredsson, Lars; Costenbader, Karen H; Kamen, Diane L; Nelson, Lorene M; Norris, Jill M; De Roos, Anneclaire J

    2012-12-01

    Autoimmune diseases (AID) are a collection of many complex disorders of unknown etiology resulting in immune responses to self-antigens and are thought to result from interactions between genetic and environmental factors. Here we review the epidemiologic evidence for the role of environmental factors in the development of human AID, the conclusions that can be drawn from the existing data, critical knowledge gaps, and research needed to fill these gaps and to resolve uncertainties. We specifically summarize the state of knowledge and our levels of confidence in the role of specific agents in the development of autoimmune diseases, and we define the areas of greatest impact for future investigations. Among our consensus findings we are confident that: 1) crystalline silica exposure can contribute to the development of several AID; 2) solvent exposure can contribute to the development of systemic sclerosis; 3) smoking can contribute to the development of seropositive rheumatoid arthritis; and 4) an inverse association exists between ultraviolet radiation exposure and the risk of development of multiple sclerosis. We suggest that more studies of phenotypes, genotypes, and multiple exposures are needed. Additional knowledge gaps needing investigation include: defining important windows in the timing of exposures and latencies relating to age, developmental state, and hormonal changes; understanding dose-response relationships; and elucidating mechanisms for disease development. Addressing these essential issues will require more resources to support research, particularly of rare AID, but knowledge of the risks conferred by environmental factors in specific genetic contexts could pave the way for prevention of AID in the future.

  6. Donor-hydrogen complexes in crystalline silicon

    NARCIS (Netherlands)

    Liang, Z.N.; Niesen, L; Haas, C; Denteneer, P.J.H.

    1996-01-01

    Experimental results are presented on the study of Sb-H complexes in crystalline silicon, employing Sb-119 --> Sn-119 source Mossbauer spectroscopy and a low-energy H implantation technique. In addition to a visible component, we observe a large decrease of the Mossbauer intensity associated with

  7. Smeared gap equations in crystalline color superconductivity

    CERN Document Server

    Ruggieri, M

    2006-01-01

    In the framework of HDET, we discuss an averaging procedure of the NJL quark-quark interaction lagrangian, treated in the mean field approximation, for the two flavor LOFF phase of QCD. This procedure gives results which are valid in domains where Ginzburg-Landau results may be questionable. We compute and compare the free energy for different LOFF crystalline structures.

  8. Crystalline amino acids and nitrogen emission

    NARCIS (Netherlands)

    Verstegen, M.W.A.; Jongbloed, A.W.

    2003-01-01

    Reductions in dietary protein level and supplementation with certain crystalline amino acids is a well-established method of formulating diets to achieve a more ideal amino acid pattern and to reduce nitrogen excretion. Up to 35% reduction in nitrogen excretion may be achieved by supplementing pig

  9. Quasi-crystalline geometry for architectural structures

    DEFF Research Database (Denmark)

    Wester, Ture; Weinzieri, Barbara

    The quasi-crystal (QC) type of material was discovered in 1983 by Dan Schechtman from Technion, Haifa. This new crystalline structure of material broke totally with the traditional conception of crystals and geometry introducing non-periodic close packing of cells with fivefold symmetry in 3D space...

  10. Crystalline damage development during martensitic transformations

    NARCIS (Netherlands)

    Suiker, A.S.J.; Turteltaub, S.R.

    2006-01-01

    A recently developed thermo-mechanical model [1] is presented that can be used to simulate the interactions between martensitic phase transformations and crystalline damage growth at the austenitic grain level. Subgrain information is included in the model via the crystallographic theory of martensi

  11. Donor-hydrogen complexes in crystalline silicon

    NARCIS (Netherlands)

    Liang, Z.N.; Niesen, L; Haas, C; Denteneer, P.J.H.

    1996-01-01

    Experimental results are presented on the study of Sb-H complexes in crystalline silicon, employing Sb-119 --> Sn-119 source Mossbauer spectroscopy and a low-energy H implantation technique. In addition to a visible component, we observe a large decrease of the Mossbauer intensity associated with th

  12. Topological crystalline insulator SnTe nanoribbons

    Science.gov (United States)

    Dahal, Bishnu R.; Dulal, Rajendra P.; Pegg, Ian L.; Philip, John

    2017-03-01

    Topological crystalline insulators are systems in which a band inversion that is protected by crystalline mirror symmetry gives rise to nontrivial topological surface states. SnTe is a topological crystalline insulator. It exhibits p-type conductivity due to Sn vacancies and Te antisites, which leads to high carrier density in the bulk. Thus growth of high quality SnTe is a prerequisite for understanding the topological crystalline insulating behavior. We have grown SnTe nanoribbons using a solution method. The width of the SnTe ribbons varies from 500 nm to 2 μm. They exhibit rock salt crystal structure with a lattice parameter of 6.32 Å. The solution method that we have adapted uses low temperature, so the Sn vacancies can be controlled. The solution grown SnTe nanoribbons exhibit strong semiconducting behavior with an activation energy of 240 meV. This activation energy matches with the calculated band gap for SnTe with a lattice parameter of 6.32 Å, which is higher than that reported for bulk SnTe. The higher activation energy makes the thermal excitation of bulk charges very difficult on the surface. As a result, the topological surfaces will be free from the disturbance caused by the thermal excitations

  13. Crystalline amino acids and nitrogen emission

    NARCIS (Netherlands)

    Verstegen, M.W.A.; Jongbloed, A.W.

    2003-01-01

    Reductions in dietary protein level and supplementation with certain crystalline amino acids is a well-established method of formulating diets to achieve a more ideal amino acid pattern and to reduce nitrogen excretion. Up to 35% reduction in nitrogen excretion may be achieved by supplementing pig d

  14. Carbon enters silica forming a cristobalite-type CO2-SiO2 solid solution

    Science.gov (United States)

    Santoro, Mario; Gorelli, Federico A.; Bini, Roberto; Salamat, Ashkan; Garbarino, Gaston; Levelut, Claire; Cambon, Olivier; Haines, Julien

    2014-04-01

    Extreme conditions permit unique materials to be synthesized and can significantly update our view of the periodic table. In the case of group IV elements, carbon was always considered to be distinct with respect to its heavier homologues in forming oxides. Here we report the synthesis of a crystalline CO2-SiO2 solid solution by reacting carbon dioxide and silica in a laser-heated diamond anvil cell (P=16-22 GPa, T>4,000 K), showing that carbon enters silica. Remarkably, this material is recovered to ambient conditions. X-ray diffraction shows that the crystal adopts a densely packed α-cristobalite structure (P41212) with carbon and silicon in fourfold coordination to oxygen at pressures where silica normally adopts a sixfold coordinated rutile-type stishovite structure. An average formula of C0.6(1)Si0.4(1)O2 is consistent with X-ray diffraction and Raman spectroscopy results. These findings may modify our view on oxide chemistry, which is of great interest for materials science, as well as Earth and planetary sciences.

  15. Synthesis of exfoliated PA66 nanocomposites via interfacial polycondensation: effect of layered silicate and silica nanoparticles

    Indian Academy of Sciences (India)

    HOSSIEN GHARABAGHI; MEHDI RAFIZADEH; FARAMARZ AFSHAR TAROMI

    2016-08-01

    Nanocomposites of polyamide 66 (PA66) with layered silicate and silica (SiO2) nanoparticles were prepared via in situ interfacial polycondensation method. Hexamethylenediamine (HDMA) and adipoyl chloride(AdCl) were reacted in a two-phase media. Montmorillonite (NaMMT) and silica nanoparticles were added to reacting media. Preparation of PA66 and its nanocomposites were studied using Fourier transform infrared spectroscopy.Dispersion of nanoparticles was studied using X-ray diffraction and transmission electron microscopy. The results show that two structures were achieved using two kinds of nanoparticles. Silica nanoparticles were partially exfoliated, while NaMMT nanoparticles were hybrid intercalated–exfoliated in nanocomposite samples. Thermal properties of samples were investigated by differential scanning calorimetry. The results suggest that crystallinity is heterogeneous in the presence of nanoparticles. Kinetic of crystallization was studied by means of Avrami equation, based on the kinetic parameters, spherulites are produced. Results were reported for nanocomposites containing 2 and 4% of nanoparticles. Avrami equation parameter, n, shows that spherulite crystallization occured in the samples. Addition of nanoparticles decreases n first, then n increases with nanoparticle content.

  16. Electrodeposition of macroporous nickel coating by employing nano-silica as template.

    Science.gov (United States)

    Xu, Lijian; Chen, Baizhen; Du, Jingjing

    2012-09-01

    A novel method of preparing the macrporous nickel coating was described. The macrporous nickel coating was fabricated by employing nano-silica as the template. The effects of technological conditions and the concentration of the additives on the surface quality of coating were investigated, the nano-silica was characterized transmission electron microscopy (TEM) and laser particle size analyzer, and the macrporous nickel coating was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results showed that nano-silica particles were about 100 nm, the optimal technological conditions of electrodepositing nickel were that the cathode current density was 12 A/dm2, the temperature was 30 degrees C and the pH value was 2.0, the concentration of lauryl sodium sulfate was 0.15 g/L and the concentration of glucide was 3 g/L, the macrporous nickel coating was obtained when the adding nano-SiO2 content in the electroplating bath was 6 g/L and its structure was crystalline.

  17. Development and characterization of hybrid materials based on biodegradable PLA matrix, microcrystalline cellulose and organophilic silica

    Directory of Open Access Journals (Sweden)

    Fernanda Abbate dos Santos

    2014-10-01

    Full Text Available The goal of this work was to investigate the production and properties of hybrid materials based on poly(lactic acid (PLA, employing microcrystalline cellulose (MCC and organophilic silica (R972 as fillers. The composites were obtained by solution casting to form films. Each nanoparticle was incorporated at 3 wt. %, relative to the polymer matrix. In this experiment, four films were obtained (PLA, PLA/MCC, PLA/R972 and PLA/MCC/R972. The films properties were evaluated by X-ray diffractometry, nuclear magnetic resonance, Fourier transform infrared spectroscopy and mechanical properties. The results showed that each nanoparticle, added individually or both combined, had different effect on the final properties of the films. Microcrystalline cellulose can act as nucleating agent for the crystallization of PLA. Silica promoted an increase in rigidity, due to the strong intermolecular forces, while MCC addition promoted an increase in the molecular mobility of the polymeric chains. The PLA/MCC/R972 film showed the highest crystallinity degree and tensile modulus. This film presented a T1H value between both values found for PLA/MCC and PLA/R972 films. The results indicated that silica R972 could promote a decrease of the surface tension between PLA and cellulose.

  18. The Influence of Silica Nanoparticles on Ionic Liquid Behavior: A Clear Difference between Adsorption and Confinement

    Directory of Open Access Journals (Sweden)

    Guozhong Wu

    2013-10-01

    Full Text Available The phase behaviors of ionic liquids (ILs confined in nanospace and adsorbed on outer surface of nanoparticles are expected to be different from those of the bulk. Anomalous phase behaviors of room temperature ionic liquid tributylhexadecylphosphonium bromide (P44416Br confined in ordered mesoporous silica nanoparticles with average pore size 3.7 nm and adsorbed on outer surface of the same silica nanoparticles were reported. It was revealed that the melting points (Tm of confined and adsorbed ILs depressed significantly in comparison with the bulk one. The Tm depressions for confined and adsorbed ILs are 8 °C and 14 °C, respectively. For comparison with the phase behavior of confined P44416Br, 1-butyl-3-methylimidazolium bromide (BmimBr was entrapped within silica nanopores, we observed an enhancement of 50 °C in Tm under otherwise similar conditions. The XRD analysis indicates the formation of crystalline-like phase under confinement, in contrast to the amorphous phase in adsorbed IL. It was confirmed that the behavior of IL has clear difference. Moreover, the complex π-π stacking and H-bonding do not exist in the newly proposed phosphonium-based IL in comparison with the widely studied imidazolium-based IL. The opposite change in melting point of P44416Br@SiO2 and BmimBr@SiO2 indicates that the cationic species plays an important role in the variation of melting point.

  19. Carbon enters silica forming a cristobalite-type CO2-SiO2 solid solution.

    Science.gov (United States)

    Santoro, Mario; Gorelli, Federico A; Bini, Roberto; Salamat, Ashkan; Garbarino, Gaston; Levelut, Claire; Cambon, Olivier; Haines, Julien

    2014-04-30

    Extreme conditions permit unique materials to be synthesized and can significantly update our view of the periodic table. In the case of group IV elements, carbon was always considered to be distinct with respect to its heavier homologues in forming oxides. Here we report the synthesis of a crystalline CO2-SiO2 solid solution by reacting carbon dioxide and silica in a laser-heated diamond anvil cell (P = 16-22 GPa, T>4,000 K), showing that carbon enters silica. Remarkably, this material is recovered to ambient conditions. X-ray diffraction shows that the crystal adopts a densely packed α-cristobalite structure (P4(1)2(1)2) with carbon and silicon in fourfold coordination to oxygen at pressures where silica normally adopts a sixfold coordinated rutile-type stishovite structure. An average formula of C0.6(1)Si0.4(1)O2 is consistent with X-ray diffraction and Raman spectroscopy results. These findings may modify our view on oxide chemistry, which is of great interest for materials science, as well as Earth and planetary sciences.

  20. Evidence for variable crystallinity in bivalve shells

    Science.gov (United States)

    Jacob, D. E.; Wehrmeister, U.

    2012-04-01

    Bivalve shells are used as important palaeoclimate proxy archives and monitor regional climate variations. The shells mostly exist of two crystalline polymorphic phases of calcium carbonate calcite (rombohedric) and aragonite (orthorhombic). Calcite is the most stable polymorph at standard conditions, whereas vaterite (hexagonal) is the least stable and only rarely found in these structures. Shells are characterized by organized structures and several micro architectures of mollusc shell structures have been identified: Nacre shows different types: columnar and bricked forms and consists of composite inorganic- organic at the nano-scale. They are well known to display a "brick and mortar" structure. By AFM and FIB/TEM methods it could be shown, that its nanostructure consists of the structures in the range of 50 - 100 nm [1, 2]. These structures are vesicles, consisting of CaCO3 and are individually coated by a membrane. Most probably, the mantle epithelian cells of the bivalve extrude CaCO3 vesicles. By Raman spectroscopic investigations the crystalline CaCO3 polymorphs calcite, aragonite and vaterite, as well as ACC were determined. For some species (Diplodon chilensis patagonicus, Hyriopsis cumingii) pure ACC (i.e. not intermingled with a crystalline phase) could be identified. The presence of an amorphous phase is generally deduced from the lack of definite lattice modes, whereas a broad Raman band in this region is to observe. In most of the cultured pearls (Pinctada maxima and genus Hyriopsis) the ν1-Raman band of ACC clearly displays an asymmetric shape and splits into two different bands according to a nanocrystalline and an amorphous fraction. The FWHMs of most of the crystalline fractions are too high for well crystallized materials and support the assumption of nanocrystalline calcium carbonate polymorph clusters in ACC. They are primarily composed of amorphous calcium carbonate (ACC) which is later transformed into a crystalline modification [3

  1. Successful implementation of the stepwise layer-by-layer growth of MOF thin films on confined surfaces: Mesoporous silica foam as a first case study

    KAUST Repository

    Shekhah, Osama

    2012-01-01

    Here we report the successful growth of highly crystalline homogeneous MOF thin films of HKUST-1 and ZIF-8 on mesoporous silica foam, by employing a layer-by-layer (LBL) method. The ability to control and direct the growth of MOF thin films on confined surfaces, using the stepwise LBL method, paves the way for new prospective applications of such hybrid systems. © 2012 The Royal Society of Chemistry.

  2. Silica ecosystem for synergistic biotransformation

    Science.gov (United States)

    Mutlu, Baris R.; Sakkos, Jonathan K.; Yeom, Sujin; Wackett, Lawrence P.; Aksan, Alptekin

    2016-06-01

    Synergistical bacterial species can perform more varied and complex transformations of chemical substances than either species alone, but this is rarely used commercially because of technical difficulties in maintaining mixed cultures. Typical problems with mixed cultures on scale are unrestrained growth of one bacterium, which leads to suboptimal population ratios, and lack of control over bacterial spatial distribution, which leads to inefficient substrate transport. To address these issues, we designed and produced a synthetic ecosystem by co-encapsulation in a silica gel matrix, which enabled precise control of the microbial populations and their microenvironment. As a case study, two greatly different microorganisms: Pseudomonas sp. NCIB 9816 and Synechococcus elongatus PCC 7942 were encapsulated. NCIB 9816 can aerobically biotransform over 100 aromatic hydrocarbons, a feat useful for synthesis of higher value commodity chemicals or environmental remediation. In our system, NCIB 9816 was used for biotransformation of naphthalene (a model substrate) into CO2 and the cyanobacterium PCC 7942 was used to provide the necessary oxygen for the biotransformation reactions via photosynthesis. A mathematical model was constructed to determine the critical cell density parameter to maximize oxygen production, and was then used to maximize the biotransformation rate of the system.

  3. Stability of Decontamination Foam Containing Silica Nanoparticles and Viscosifier

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, In Ho; Jung, Chong Hun; Yoon, Suk Bon; Kim, Chorong; Jung, Jun Young; Park, Sang Yoon; Moon, Jei Kwon; Choi, Wang Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-10-15

    This formulation can significantly decrease the amounts of chemical reagents and secondary waste. The advantage of decontamination foam is its potentially wide application for metallic walls, overhead surfaces, and the elements of complex components and facilities. In addition, foam is a good material for in situ decontamination because it generates low final waste volumes owing to its volume expansion. The application of foam allows for remote decontamination processing using only an injection nozzle and the equipment to generate the decontamination foam, which reduces operator exposure to high radioactivity. The decontamination efficiency can be enhanced by improving the contact time between chemical reagents and a contaminated surface through the addition of surfactants and viscosifiers into the decontamination foam. The objective of this study is to investigate the effect of silica nanoparticles and a viscosifier on the foam stability and the dissolution behaviors of corroded specimens using a non-ionic surfactant. This study showed the effect of viscosifiers and nanoparticles on the foam stability when developing new formulations of decontamination foam. The addition of xanthan gum and the mixture of xanthan gum and silica nanoparticles (M-5) significantly increased the foam stability, compared to the surfactant solution alone. This result indicates that both the viscosifier and nanoparticles have a synergistic effect on the foam stability. As the contact time increased, the dissolution rate increased to become similar to the dissolution that contained decontamination liquid.

  4. A model for the effects of germanium on silica biomineralization in choanoflagellates

    OpenAIRE

    Marron, Alan O.; Chappell, Helen; Ratcliffe, Sarah; Goldstein, Raymond E.

    2016-01-01

    This is the final version of the article. It first appeared from Royal Society Publishing via http://dx.doi.org/10.1098/rsif.2016.0485 Silica biomineralization is a widespread phenomenon of major biotechnological interest. Modifying biosilica with substances like germanium (Ge) can confer useful new properties, although exposure to high levels of Ge disrupts normal biosilicification. No clear mechanism explains why this disruption occurs. Here, we study the effect of Ge on loricate choanof...

  5. Immunoprecipitation of bisphenol A by antibody–mesoporous silica composites

    Directory of Open Access Journals (Sweden)

    Toru Orita

    2014-09-01

    Full Text Available Bisphenol A (BPA is of global concern because of its disruption of endocrine systems and ubiquity in aquatic environment. In this study, BPA antibody was successfully immobilised on novel mesoporous silica (MPS carriers that display unique properties such as high surface area, highly uniform pore distribution and high adsorption capacity. Mobil Crystalline Material MCM-41 (2.7 nm, Santa Barbara Amorphous SBA-15-1 (12.3 nm and SBA-15-2 (24.0 nm materials were used as supports for these antibodies. On these carriers, the BPA antibody immobilisation reached 40 μg mg−1. For each MPS, 15 ng of BPA antigen was adsorbed on 1 mg of MPS–antibody composite, which resulted in an antibody activity of 30%. The highest recovery rate of BPA antigen was observed for 80% acetonitrile in 10 mM phosphate buffer (pH 7. After six repeated runs, BPA antibodies immobilised on SBA-15-1 and SBA-15-2 retained about 30% of their initial activity. In contrast, these antibodies showed 13% lower residual activity on MCM-41 than on SBA-15-1 and SBA-15-2. This result indicated that entire antibody molecules were adsorbed inside SBA-15-1 and SBA-15-2 pores, stabilising their structural conformation.

  6. Characterization of silica quartz as raw material in photovoltaic applications

    Science.gov (United States)

    Boussaa, S. Anas; Kheloufi, A.; Zaourar, N. Boutarek; Kefaifi, A.; Kerkar, F.

    2016-07-01

    Raw materials are essential for the functioning of modern societies, and access to these raw materials is vital to the world economy. Sustainable development, both globally level, raises important new challenges associated with access and efficient use of raw materials. High purity quartz, is consider as a critical raw material and it is a rare commodity that only forms under geological conditions where a narrow set of chemical and physical parameters is fulfilled. When identified and following special beneficiation techniques, high purity quartz obtains very attractive prices and is applied in high technology sectors that currently are under rapid expansion such as photovoltaic solar cells, silicon metal - oxide wafers in the semiconductor industry and long distance optical fibers that are used in communication networks. Crystalline silicon remains the principal material for photovoltaic technology. Metallurgical silicon is produced industrially by the reduction of silica with carbon in an electric arc furnace at temperatures higher than 2000 °C in the hottest parts, by a reaction that can be written ideally as: SiO2 + 2C = Si + 2CO. The aim of this study has been to test experimental methods for investigating the various physical and chemical proprieties of Hoggar quartz with different techniques: X Ray Fluorescence, infra-red spectroscopy, Scanning Electron Microscopy, Optic Microscopy, Carbon Analyzer and Vickers Hardness. The results show finally that the quartz has got good result in purity but need enrichment for the photovoltaic application.

  7. Characterization of silica quartz as raw material in photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Boussaa, S. Anas, E-mail: sabiha.anas@gmail.com; Kheloufi, A.; Kefaifi, A.; Kerkar, F. [Division croissance cristalline et procédés métallurgiques CCPM Centre de recherche en technologie des semi-conducteurs pour l’énergétique (C.R.T.S.E) 02 Bd Frantz Fanon BP. 140 Alger 7 merveilles, Alger 16200 (Algeria); Zaourar, N. Boutarek [Laboratoire des technologies des matériaux, USTHB, B.P. 32 El Alia, Bab Ezzouar, Alger, Algérie 16111 (Algeria)

    2016-07-25

    Raw materials are essential for the functioning of modern societies, and access to these raw materials is vital to the world economy. Sustainable development, both globally level, raises important new challenges associated with access and efficient use of raw materials. High purity quartz, is consider as a critical raw material and it is a rare commodity that only forms under geological conditions where a narrow set of chemical and physical parameters is fulfilled. When identified and following special beneficiation techniques, high purity quartz obtains very attractive prices and is applied in high technology sectors that currently are under rapid expansion such as photovoltaic solar cells, silicon metal - oxide wafers in the semiconductor industry and long distance optical fibers that are used in communication networks. Crystalline silicon remains the principal material for photovoltaic technology. Metallurgical silicon is produced industrially by the reduction of silica with carbon in an electric arc furnace at temperatures higher than 2000 °C in the hottest parts, by a reaction that can be written ideally as: SiO{sub 2} + 2C = Si + 2CO. The aim of this study has been to test experimental methods for investigating the various physical and chemical proprieties of Hoggar quartz with different techniques: X Ray Fluorescence, infra-red spectroscopy, Scanning Electron Microscopy, Optic Microscopy, Carbon Analyzer and Vickers Hardness. The results show finally that the quartz has got good result in purity but need enrichment for the photovoltaic application.

  8. The Management of Silica in Los Alamos National Laboratory Tap Water - A Study of Silica Solubility

    Energy Technology Data Exchange (ETDEWEB)

    Wohlberg, C.; Worland, V.P.; Kozubal, M.A.; Erickson, G.F.; Jacobson, H.M.; McCarthy, K.T.

    1999-07-01

    Well water at Los Alamos National Laboratory (LANL) has a silica (SiO{sub 2}) content of 60 to 100 mg/L, with 4 mg/L of magnesium, 13 mg/L calcium and lesser concentrations of other ions. On evaporation in cooling towers, when the silica concentration reaches 150 to 220 mg/L, silica deposits on heat transfer surfaces. When the high silica well water is used in the reprocessing of plutonium, silica remains in solution at the end of the process and creates a problem of removal from the effluent prior to discharge or evaporation. The work described in this Report is divided into two major parts. The first part describes the behavior of silica when the water is evaporated at various conditions of pH and in the presence of different classes of anions: inorganic and organic. In the second part of this work it was found that precipitation (floccing) of silica was a function of solution pH and mole ratio of metal to silica.

  9. Effect of Mineral Admixtures on Alkali-Silica Reaction

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chengzhi; WANG Aiqin

    2008-01-01

    The influence of silica fume,slag and fly ash on alkali-silica reaction under the condition of 70℃ is studied.The results show that silica,slag and fly ash may inhibit alkali-silica reaction only under suitable content.When the content is less than 10%,silica fume does not markedly influence the expansion of alkali-silica reaction.When the content is 15%-20%,silica fume only may delay the expansion of alkali-silica reaction.When the content is 30%-70%,slag may only delay the expansion of alkali-silica reaction,but cannot inhibit the expansion of alkali-silica reaction.When the content is 10%,fly ash does not markedly influence the expansion of alkali-silica reaction.When the content is 20%-30%,fly ash may only delay the expansion of alkali-silica reaction,but cannot inhibit the expansion of alkali-silica reaction.When the content is over 50%,it is possible that fly ash can inhibit effectively alkali-silica reaction.

  10. Fungus-mediated preferential bioleaching of waste material such as fly - ash as a means of producing extracellular, protein capped, fluorescent and water soluble silica nanoparticles.

    Directory of Open Access Journals (Sweden)

    Shadab Ali Khan

    Full Text Available In this paper, we for the first time show the ability of the mesophilic fungus Fusarium oxysporum in the bioleaching of waste material such as Fly-ash for the extracellular production of highly crystalline and highly stable, protein capped, fluorescent and water soluble silica nanoparticles at ambient conditions. When the fungus Fusarium oxysporum is exposed to Fly-ash, it is capable of selectively leaching out silica nanoparticles of quasi-spherical morphology within 24 h of reaction. These silica nanoparticles have been completely characterized by UV-vis spectroscopy, Photoluminescence (PL, Transmission electron microscopy (TEM, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and Energy dispersive analysis of X-rays (EDAX.

  11. Coherent X-ray and laser spectroscopy measurements of diffusion in concentrated alpha-crystallin solutions

    Science.gov (United States)

    Karunaratne, V. N. C.

    The mammalian eye lens is composed of a concentrated solution of water soluble proteins called crystallins. Alpha-crystallin, the most abundant protein found in the lens, plays a crucial role in maintaining lens transparency and lens accommodation. However, alpha-crystallins along with other ocular proteins suffer from irreversible processes such as oxidation. One cause of oxidation is radiation-induced radical formation which alters the inter-molecular interactions, thereby degrading the normal function of ocular proteins. The main goal of this thesis is to quantify molecular scale dynamics of concentrated solutions of alpha-crystallins using coherent X-rays and visible laser light. I believe a detailed analysis of the dynamics pertaining to alpha-crystallin will provide the foundation to understand molecular scale mechanisms that lead to conditions like cataract and presbyopia. I explore the dynamics of concentrated alpha-crystallin solutions by measuring diffusive motion over a range of length scales using Dynamic light scattering (DLS) and X-ray photon correlation spectroscopy (XPCS). To a certain extent, the dynamical properties of crystallins obtained in this manner are consistent with established theories in colloidal physics. However, there are some deviations, which I will address in this thesis. In terms of X-ray data, I employed a new, efficient photon correlation technique to obtain the best possible signal, furthermore this technique is embedded in a stand-alone software program that has the ability to provide real time results, quickly and efficiently with the help of high performance computing resources available at Northern Illinois University (NIU). The technique has potential to be used by the coherent X-ray spectroscopy community in the future. In addition, by using X-ray scattering data, I probe potential modifications and or damage effects on alpha-crystallins due to radiation exposure. The damage analysis methodology described in this thesis

  12. Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

    Science.gov (United States)

    Liu, Chunyuan; Kim, Jin Seuk; Kwon, Younghwan

    2016-02-01

    This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used.

  13. Synthesis and Characterization of Bionanoparticle-Silica Composites and Mesoporous Silica with Large Pores

    Energy Technology Data Exchange (ETDEWEB)

    Niu, Z.; Yang, L.; Kabisatpathy, S.; He, J.; Lee, A.; Ron, J.; Sikha, G.; Popov, B.N.; Emrick, T.; Russell, T. P.; Wang. Q.

    2009-03-24

    A sol-gel process has been developed to incorporate bionanoparticles, such as turnip yellow mosaic virus, cowpea mosaic virus, tobacco mosaic virus, and ferritin into silica, while maintaining the integrity and morphology of the particles. The structures of the resulting materials were characterized by transmission electron microscopy, small angle X-ray scattering, and N{sub 2} adsorption-desorption analysis. The results show that the shape and surface morphology of the bionanoparticles are largely preserved after being embedded into silica. After removal of the bionanoparticles by calcination, mesoporous silica with monodisperse pores, having the shape and surface morphology of the bionanoparticles replicated inside the silica, was produced,. This study is expected to lead to both functional composite materials and mesoporous silica with structurally well-defined large pores.

  14. Hard magnetism in structurally engineered silica nanocomposite.

    Science.gov (United States)

    Song, Hyon-Min; Zink, Jeffrey I

    2016-09-21

    Creation of structural complexity by simple experimental control will be an attractive approach for the preparation of nanomaterials, as a classical bottom-up method is supplemented by a more efficient and more direct artificial engineering method. In this study, structural manipulation of MCM-41 type mesoporous silica is investigated by generating and imbedding hard magnetic CoFe2O4 nanoparticles into mesoporous silica. Depending on the heating rate and target temperature, mesoporous silica undergoes a transformation in shape to form hollow silica, framed silica with interior voids, or melted silica with intact mesostructures. Magnetism is governed by the major CoFe2O4 phase, and it is affected by antiferromagnetic hematite (α-Fe2O3) and olivine-type cobalt silicate (Co2SiO4), as seen in its paramagnetic behavior at the annealing temperature of 430 °C. The early formation of Co2SiO4 than what is usually observed implies the effect of the partial substitution of Fe in the sites of Co. Under slow heating (2.5 °C min(-1)) mesostructures are preserved, but with significantly smaller mesopores (d100 = 1.5 nm). In addition, nonstoichiometric CoxFe1-xO with metal vacancies at 600 °C, and spinel Co3O4 at 700 °C accompany major CoFe2O4. The amorphous nature of silica matrix is thought to contribute significantly to these structurally diverse and rich phases, enabled by off-stoichiometry between Si and O, and accelerated by the diffusion of metal cations into SiO4 polyhedra at an elevated temperature.

  15. Shaped Ni nanoparticles with an unconventional hcp crystalline structure.

    Science.gov (United States)

    Kim, Chanyeon; Kim, Cheonghee; Lee, Kangtaek; Lee, Hyunjoo

    2014-06-18

    Hourglass-shaped Ni nanoparticles were synthesized with a hexagonal close packed (hcp) structure. The unconventional crystalline structure could be stabilized by intensive utilization of hexadecylamine. The dense organic layer on the surface protected the meta-stable crystalline structure.

  16. Performance analysis of field exposed single crystalline silicon modules

    Energy Technology Data Exchange (ETDEWEB)

    Sastry, O.S.; Saurabh, Sriparn; Shil, S.K.; Pant, P.C.; Kumar, Rajesh; Kumar, Arun; Bandopadhyay, Bibek [Solar Energy Centre, Ministry of New and Renewable Energy, Block-14, CGO Complex, Lodhi Road, New Delhi - 110003 (India)

    2010-09-15

    This paper presents results on the field performance degradation of mono-crystalline silicon PV modules from 11 PV module manufacturers under identical field conditions. The modules were installed in both fixed tilt and manual tracking modes. The data were monitored using a CR23X Data logger and I-V curves were taken using SPI 240A Sun simulator. The performance parameters analyzed are V{sub oc}, I{sub sc}, P{sub max}, I{sub mp}, V{sub mp} and the fill factor, as a function of time of field exposure. Qualitative studies are made on physically visible defects such as EVA coloration, cell de-laminations, corrosion of solar cell grid, corrosion of end strip connected in the terminal box, failure of by-pass diode, detachment of the terminal box, tearing of tedlar sheet, etc. The effect of field exposure on the performance parameters indicates that the qualification standard (s) needs to be reviewed and revised if the modules are to perform for {proportional_to}20 years under actual field conditions in India. (author)

  17. Effect of chemically modified silicas on the properties of hybrid gel electrolyte for Li-ion batteries

    Science.gov (United States)

    Walkowiak, Mariusz; Zalewska, Aldona; Jesionowski, Teofil; Waszak, Daniel; Czajka, Bogdan

    The aim of the presented work was to perform a preliminary study the physico-chemical properties of hybrid organic-inorganic gel electrolytes for Li-ion batteries based on the PVdF-HFP polymeric matrix and surface modified fumed silicas. Modifications were done by means of the so-called dry method using seven different silanes differing in the nature of the principal functional group: N-2-(aminoethyl)-3-amino propyltrimethoxysilane, 3-glycidoxypropyltrimetoxysilane, 3-mercaptopropyltrimetoxysilane, n-octyltriethoxysilane, 3-(chloropropyl)trimethoxysilane, 3-methacryloxypropyltrimetoxysilane, vinyltrimethoxysilane. The PVdF-HFP gels were prepared according to the so-called Bellcore process (two-step method). Impact of the silicas surface functionality on the degree of crystallinity of the polymeric membranes was studied using the differential scanning calorimetry technique. Applicability of the prepared gel electrolytes for the Li-ion technology was estimated on the basis of specific conductivity measurements. It was shown that modification of the silica surface by most of the silanes causes an increase in the gel specific conductivity by about two orders of magnitude as compared to gel with unmodified silica.

  18. Effect of chemically modified silicas on the properties of hybrid gel electrolyte for Li-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Walkowiak, Mariusz; Waszak, Daniel; Czajka, Bogdan [Central Laboratory of Batteries and Cells, ul. Forteczna 12, 61-362 Poznan (Poland); Zalewska, Aldona [Warsaw University of Technology, Department of Chemistry, ul. Noakowskiego 3, 00-664 Warsaw (Poland); Jesionowski, Teofil [Poznan University of Technology, Institute of Chemical Technology and Engineering, Pl. Marii Sklodowskiej-Curie 2, 60-965 Poznan (Poland)

    2006-09-13

    The aim of the presented work was to perform a preliminary study the physico-chemical properties of hybrid organic-inorganic gel electrolytes for Li-ion batteries based on the PVdF-HFP polymeric matrix and surface modified fumed silicas. Modifications were done by means of the so-called dry method using seven different silanes differing in the nature of the principal functional group: N-2-(aminoethyl)-3-amino propyltrimethoxysilane, 3-glycidoxypropyltrimetoxysilane, 3-mercaptopropyltrimetoxysilane, n-octyltriethoxysilane, 3-(chloropropyl)trimethoxysilane, 3-methacryloxypropyltrimetoxysilane, vinyltrimethoxysilane. The PVdF-HFP gels were prepared according to the so-called Bellcore process (two-step method). Impact of the silicas surface functionality on the degree of crystallinity of the polymeric membranes was studied using the differential scanning calorimetry technique. Applicability of the prepared gel electrolytes for the Li-ion technology was estimated on the basis of specific conductivity measurements. It was shown that modification of the silica surface by most of the silanes causes an increase in the gel specific conductivity by about two orders of magnitude as compared to gel with unmodified silica. (author)

  19. Increasing the oral bioavailability of the poorly water soluble drug itraconazole with ordered mesoporous silica.

    Science.gov (United States)

    Mellaerts, Randy; Mols, Raf; Jammaer, Jasper A G; Aerts, Caroline A; Annaert, Pieter; Van Humbeeck, Jan; Van den Mooter, Guy; Augustijns, Patrick; Martens, Johan A

    2008-05-01

    This study aims to evaluate the in vivo performance of ordered mesoporous silica (OMS) as a carrier for poorly water soluble drugs. Itraconazole was selected as model compound. Physicochemical characterization was carried out by SEM, TEM, nitrogen adsorption, DSC, TGA and in vitro dissolution. After loading itraconazole into OMS, its oral bioavailability was compared with the crystalline drug and the marketed product Sporanox in rabbits and dogs. Plasma concentrations of itraconazole and OH-itraconazole were determined by HPLC-UV. After administration of crystalline itraconazole in dogs (20mg), no systemic itraconazole could be detected. Using OMS as a carrier, the AUC0-8 was boosted to 681+/-566 nM h. In rabbits, the AUC0-24 increased significantly from 521+/-159 nM h after oral administration of crystalline itraconazole (8 mg) to 1069+/-278 nM h when this dose was loaded into OMS. Tmax decreased from 9.8+/-1.8 to 4.2+/-1.8h. No significant differences (AUC, Cmax, and Tmax) could be determined when comparing OMS with Sporanox in both species. The oral bioavailability of itraconazole formulated with OMS as a carrier compares well with the marketed product Sporanox, in rabbits as well as in dogs. OMS can therefore be considered as a promising carrier to achieve enhanced oral bioavailability for drugs with extremely low water solubility.

  20. Assessment of occupational exposure in a granite quarry and processing factory.

    Science.gov (United States)

    Tejado, J J; Guillén, J; Baeza, A

    2016-09-01

    Workers in the granite industry face an occupational hazard: silicosis due to the crystalline silica present in inhalable dust. As granite can also present a variable, and occasionally significant, content of naturally occurring radionuclides, they may also face a radiological hazard. In order to assess the risk, a granite industry with a quarry and processing factory was selected to assess the occupational exposure. Three main potential pathways were observed: external irradiation, inhalation of granite dust, and radon exposure. The external dose rate was similar to that in a nearby farming area. A slight increment (0.016-0.076 mSv yr(-1)) was observed in the quarry and stockpile, due to quarry faces and granite blocks. The effective dose due to granite dust inhalation was 0.182  ±  0.009 mSv yr(-1) in the worst case scenario (3 mg m(-3) dust load in air and no use of filter masks). Thus, the mean value of the effective dose from these two pathways was 0.26 mSv yr(-1), lower than the reference level of 1 mSv yr(-1) for the general population. The annual mean value of radon concentration in the indoor air was 33 Bq m(-3). However, during granite processing works the radon concentration can increase up to 216 Bq m(-3), due to mechanical operations (sawing, polishing, sanding, etc). This radon concentration was below the 600 Bq m(-3) reference level for action in working places. Therefore, workers in this granite factory face no significant additional radiological exposure, and no-one needs to be designated as occupationally exposed and subject to individual dosimetry.

  1. Silica in a Mars analog environment: Ka u Desert, Kilauea Volcano, Hawaii

    Science.gov (United States)

    Seelos, K.D.; Arvidson, R. E.; Jolliff, B.L.; Chemtob, S.M.; Morris, R.V.; Ming, D. W.; Swayze, G.A.

    2010-01-01

    Airborne Visible/Near-Infrared Imaging Spectrometer (AVIRIS) data acquired over the Ka u Desert are atmospherically corrected to ground reflectance and used to identify the mineralogic components of relatively young basaltic materials, including 250-700 and 200-400 year old lava flows, 1971 and 1974 flows, ash deposits, and solfatara incrustations. To provide context, a geologic surface units map is constructed, verified with field observations, and supported by laboratory analyses. AVIRIS spectral endmembers are identified in the visible (0.4 to 1.2 ??m) and short wave infrared (2.0 to 2.5 ??m) wavelength ranges. Nearly all the spectral variability is controlled by the presence of ferrous and ferric iron in such minerals as pyroxene, olivine, hematite, goethite, and poorly crystalline iron oxides or glass. A broad, nearly ubiquitous absorption feature centered at 2.25 ??m is attributed to opaline (amorphous, hydrated) silica and is found to correlate spatially with mapped geologic surface units. Laboratory analyses show the silica to be consistently present as a deposited phase, including incrustations downwind from solfatara vents, cementing agent for ash duricrusts, and thin coatings on the youngest lava flow surfaces. A second, Ti-rich upper coating on young flows also influences spectral behavior. This study demonstrates that secondary silica is mobile in the Ka u Desert on a variety of time scales and spatial domains. The investigation from remote, field, and laboratory perspectives also mimics exploration of Mars using orbital and landed missions, with important implications for spectral characterization of coated basalts and formation of opaline silica in arid, acidic alteration environments. Copyright 2010 by the American Geophysical Union.

  2. Enhanced Photocatalytic Activity for Degradation of Methyl Orange over Silica-Titania

    Directory of Open Access Journals (Sweden)

    Yaping Guo

    2011-01-01

    Full Text Available Silica-modified titania (SMT powders with different atomic ratios of silica to titanium (Rx were successfully synthesized by a simple ultrasonic irradiation technique. The prepared samples were characterized by X-ray diffraction (XRD, FT-IR spectroscopy, transmission electron microscopy (TEM, X-ray photoelectron spectroscopy (XPS, and ultraviolet visible spectroscopy. The specific surface area was measured according to BET theory. Results indicate that the addition of silica to titania can suppress the crystalline size growth and the transformation of anatase phase to rutile phase of titania, enlarge specific surface area of the titania particles, and result in a blue shift of absorption edge compared to pure titania. The photocatalytic activity of the SMT samples was evaluated by decolorizing methyl orange aqueous solutions under UV-visible light irradiation. It was found in our study that this activity was affected by silica content, calcination temperature, H2SO4, and oxidants such as KIO4, (NH42S2O8 and H2O2. The results reveal that the photocatalytic activity of 0.1-SMT catalyst is the best among all samples calcined at 550°C for 1 h and it is 1.56 times higher than that of Degussa P-25 titania, which is a widely used commercial TiO2 made by Germany Degussa company and has been most widely used in industry as photocatalyst, antiultraviolet product, and thermal stabilizer. The optimal calcination temperature for preparation was 550°C. The photocatalytic activity of SMT samples is significantly enhanced by H2SO4 solution treatment and oxidants.

  3. Silica Synthesis by Sponges: Unanticipated Molecular Mechanism

    Science.gov (United States)

    Morse, D. E.; Weaver, J. C.

    2001-12-01

    Oceanic diatoms, sponges and other organisms synthesize gigatons per year of silica from silicic acid, ultimately obtained from the weathering of rock. This biogenic silica exhibits a remarkable diversity of structures, many of which reveal a precision of nanoarchitectural control that exceeds the capabilities of human engineering. In contrast to the conditions of anthropogenic and industrial manufacture, the biological synthesis of silica occurs under mild physiological conditions of low temperatures and pressures and near-neutral pH. In addition to the differentiation between biological and abiotic processes governing silica formation, the biomolecular mechanisms controlling synthesis of these materials may offer insights for the development of new, environmentally benign routes for synthesis of nanostructurally controlled silicas and high-performance polysiloxane composites. We found that the needle-like silica spicules made by the marine sponge, Tethya aurantia, each contain an occluded axial filament of protein composed predominantly of repeating assemblies of three similar subunits we named "silicateins." To our surprise, analysis of the purified protein subunits and the cloned silicatein DNAs revealed that the silicateins are highly homologous to a family of hydrolytic enzymes. As predicted from this finding, we discovered that the silicatein filaments are more than simple, passive templates; they actively catalyze and spatially direct polycondensation to form silica, (as well as the phenyl- and methyl-silsesquioxane) from the corresponding silicon alkoxides at neutral pH and low temperature. Catalytic activity also is exhibited by the silicatein subunits obtained by disaggregation of the protein filaments and those produced from recombinant DNA templates cloned in bacteria. This catalytic activity accelerates the rate-limiting hydrolysis of the silicon alkoxide precursors. Genetic engineering, used to produce variants of the silicatein molecule with

  4. Synthesis and structural characterization of ZnO and CuO nanoparticles supported mesoporous silica SBA-15

    Science.gov (United States)

    El-Nahhal, Issa M.; Salem, Jamil K.; Selmane, Mohamed; Kodeh, Fawzi S.; Ebtihan, Heba A.

    2017-01-01

    Zinc oxide (ZnO) and copper oxide (CuO) nanoparticles were loaded into mesoporous silica SBA-15 by post-synthesis and direct methods. The structural properties were characterized using wide and small angle X-ray diffraction (WXRD & SXRD), X-ray photoelectron spectroscopy (XPS) and N2-adsorption desorption (BET). The WXRD showed that, the loaded zinc and copper oxides were present in crystalline forms (impregnation). The mesoporosity properties of SBA-15 silica were well maintained even after the introduction of metal oxide nanoparticles. BET analysis indicate that the impregnated and condensed ZnO and CuO supported SBA-15 nanocomposites have a lower surface area than that of its parent SBA-15.

  5. Molecular imprinting of bulk, microporous silica

    Science.gov (United States)

    Katz, Alexander; Davis, Mark E.

    2000-01-01

    Molecular imprinting aims to create solid materials containing chemical functionalities that are spatially organized by covalent or non-covalent interactions with imprint (or template) molecules during the synthesis process. Subsequent removal of the imprint molecules leaves behind designed sites for the recognition of small molecules, making the material ideally suited for applications such as separations, chemical sensing and catalysis. Until now, the molecular imprinting of bulk polymers and polymer and silica surfaces has been reported, but the extension of these methods to a wider range of materials remains problematic. For example, the formation of substrate-specific cavities within bulk silica, while conceptually straightforward, has been difficult to accomplish experimentally. Here we describe the imprinting of bulk amorphous silicas with single aromatic rings carrying up to three 3-aminopropyltriethoxysilane side groups; this generates and occupies microporosity and attaches functional organic groups to the pore walls in a controlled fashion. The triethoxysilane part of the molecules' side groups is incorporated into the silica framework during sol-gel synthesis, and subsequent removal of the aromatic core creates a cavity with spatially organized aminopropyl groups covalently anchored to the pore walls. We find that the imprinted silicas act as shape-selective base catalysts. Our strategy can be extended to imprint other functional groups, which should give access to a wide range of functionalized materials.

  6. Femtosecond laser writing of waveguide retarders in fused silica for polarization control in optical circuits.

    Science.gov (United States)

    Fernandes, Luís A; Grenier, Jason R; Herman, Peter R; Aitchison, J Stewart; Marques, Paulo V S

    2011-09-12

    Femtosecond laser (300 fs, 500 kHz, 522 nm) fabrication of optical waveguides in bulk silica glass is extended to waveguide retarders. We study the merits of nanograting orientation (perpendicular or parallel to the waveguide) for generating high and low birefringence waveguides. This is used together with other exposure condition to control the waveguide birefringence between 10⁻⁵ and 10⁻⁴ permitting for the simultaneous fabrication of the waveguides and the tuning of the retardance demonstrating quarter and half-wave retarders in the 1200 nm to 1700 nm spectrum. The wavelength dependence of the birefringence is also characterized over a range of exposure conditions.

  7. Evaluation of UV absorption coefficient in laser-modified fused silica

    Energy Technology Data Exchange (ETDEWEB)

    Negres, R A; Burke, M W; Sutton, S B; DeMange, P; Feit, M D; Demos, S G

    2006-08-21

    Laser-induced damage in transparent dielectrics leads to the formation of laser-modified material as a result of exposure to extreme localized temperatures and pressures. In this work, we used an infrared thermal imaging system in combination with a fluorescence microscope to map the dynamics of the local surface temperature and fluorescence intensity under cw, UV excitation of laser-modified fused silica within a damage site. Based on a thermal diffusion model, we estimate the energy deposited via linear absorption mechanisms and derive the absorption coefficient of the modified material. In addition, irreversible changes in the absorption following extended laser exposure were observed.

  8. Development of a biosensor for environmental monitoring based on microalgae immobilized in silica hydrogels.

    Science.gov (United States)

    Ferro, Yannis; Perullini, Mercedes; Jobbagy, Matias; Bilmes, Sara A; Durrieu, Claude

    2012-12-06

    A new biosensor was designed for the assessment of aquatic environment quality. Three microalgae were used as toxicity bioindicators: Chlorella vulgaris, Pseudokirchneriella subcapitata and Chlamydomonas reinhardtii. These microalgae were immobilized in alginate and silica hydrogels in a two step procedure. After studying the growth rate of entrapped cells, chlorophyll fluorescence was measured after exposure to (3-(3,4-dichlorophenyl)-1,1-dimethylurea) (DCMU) and various concentrations of the common herbicide atrazine. Microalgae are very sensitive to herbicides and detection of fluorescence enhancement with very good efficiency was realized. The best detection limit was 0.1 µM, obtained with the strain C. reinhardtii after 40 minutes of exposure.

  9. Electromagnetic Processes in strong Crystalline Fields

    CERN Multimedia

    Uggerhoj, U I; Mikkelsen, F K

    2007-01-01

    We propose a number of new investigations on aspects of radiation from high energy electron and positron beams (10-300 GeV) in single crystals and amorphous targets. The common heading is radiation emission by electrons and positrons in strong electromagnetic fields, but as the setup is quite versatile, other related phenomena in radiation emission can be studied as well. The intent is to clarify the role of a number of important aspects of radiation in strong fields as e.g. observed in crystals. We propose to measure trident 'Klein-like' production in strong crystalline fields, 'crystalline undulator' radiation, 'sandwich' target phenomena, LPM suppression of pair production as well as axial and planar effects in contributions of spin to the radiation.

  10. Liquid Crystalline Semiconductors Materials, properties and applications

    CERN Document Server

    Kelly, Stephen; O'Neill, Mary

    2013-01-01

    This is an exciting stage in the development of organic electronics. It is no longer an area of purely academic interest as increasingly real applications are being developed, some of which are beginning to come on-stream. Areas that have already been commercially developed or which are under intensive development include organic light emitting diodes (for flat panel displays and solid state lighting), organic photovoltaic cells, organic thin film transistors (for smart tags and flat panel displays) and sensors. Within the family of organic electronic materials, liquid crystals are relative newcomers. The first electronically conducting liquid crystals were reported in 1988 but already a substantial literature has developed. The advantage of liquid crystalline semiconductors is that they have the easy processability of amorphous and polymeric semiconductors but they usually have higher charge carrier mobilities. Their mobilities do not reach the levels seen in crystalline organics but they circumvent all of t...

  11. Radiation collimation in a thick crystalline undulator

    Science.gov (United States)

    Wistisen, Tobias Nyholm; Uggerhøj, Ulrik Ingerslev; Hansen, John Lundsgaard; Lauth, Werner; Klag, Pascal

    2017-05-01

    With the recent experimental confirmation of the existence of energetic radiation from a Small Amplitude, Small Period (SASP) crystalline undulator [T.N. Wistisen, K.K. Andersen, S. Yilmaz, R. Mikkelsen, J. Lundsgaard Hansen, U.I. Uggerhøj, W. Lauth, H. Backe, Phys. Rev. Lett. 112, 254801 (2014)], the field of specially manufactured crystals, from which specific radiation characteristics can be obtained, has evolved substantially. In this paper we confirm the existence of the crystalline undulator radiation, using electrons of energies of 855 GeV from the MAinzer MIcrotron (MAMI) in a crystal that is approximately 10 times thicker than the previous one. Furthermore, we have measured a significant increase in enhancement, in good agreement with calculations, of the undulator peak by collimation to angles smaller than the natural opening angle of the radiation emission process, 1 /γ. Contribution to the Topical Issue: "Dynamics of Systems at the Nanoscale", edited by Andrey Solov'yov and Andrei Korol.

  12. Basic research challenges in crystalline silicon photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Werner, J.H. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    1995-08-01

    Silicon is abundant, non-toxic and has an ideal band gap for photovoltaic energy conversion. Experimental world record cells of 24 % conversion efficiency with around 300 {mu}m thickness are only 4 % (absolute) efficiency points below the theoretical Auger recombination-limit of around 28 %. Compared with other photovoltaic materials, crystalline silicon has only very few disadvantages. The handicap of weak light absorbance may be mastered by clever optical designs. Single crystalline cells of only 48 {mu}m thickness showed 17.3 % efficiency even without backside reflectors. A technology of solar cells from polycrystalline Si films on foreign substrates arises at the horizon. However, the disadvantageous, strong activity of grain boundaries in Si could be an insurmountable hurdle for a cost-effective, terrestrial photovoltaics based on polycrystalline Si on foreign substrates. This talk discusses some basic research challenges related to a Si based photovoltaics.

  13. University Crystalline Silicon Photovoltaics Research and Development

    Energy Technology Data Exchange (ETDEWEB)

    Ajeet Rohatgi; Vijay Yelundur; Abasifreke Ebong; Dong Seop Kim

    2008-08-18

    The overall goal of the program is to advance the current state of crystalline silicon solar cell technology to make photovoltaics more competitive with conventional energy sources. This program emphasizes fundamental and applied research that results in low-cost, high-efficiency cells on commercial silicon substrates with strong involvement of the PV industry, and support a very strong photovoltaics education program in the US based on classroom education and hands-on training in the laboratory.

  14. Cystoid Macular Edema in Bietti's Crystalline Retinopathy

    Directory of Open Access Journals (Sweden)

    Ali Osman Saatci

    2014-01-01

    Full Text Available A 27-year-old man with progressive bilateral visual decline was diagnosed to have Bietti's crystalline dystrophy (BCD. Fluorescein angiography revealed bilateral petaloid type late hyperfluorescence implicating concurrent cystoid macular edema (CME. Optical coherence tomography exhibited cystoid foveal lacunas OU. During the follow-up of six years, intraretinal crystals reduced in amount but CME persisted angiographically and tomographically. CME is among the rare macular features of BCD including subfoveal sensorial detachment, subretinal neovascular membrane, and macular hole.

  15. Concentration Transitions on the Crystalline Lattices

    Directory of Open Access Journals (Sweden)

    N.A. Gorenko

    2014-07-01

    Full Text Available Results of numerical modeling of dilute 2D and 3D crystalline lattices are presented. The percolation thresholds for face-centered cubic (fcc, body-centered cubic (bcc and the simple cubic (sc lattices for the first, second and third coordination spheres are obtained by means of Monte Carlo (MC method. It is shown, that the mean value of the percolation cluster density has a minimum value at the percolation threshold.

  16. Cystoid Macular Edema in Bietti's Crystalline Retinopathy

    OpenAIRE

    Ali Osman Saatci; Hasan Can Doruk; Aylin Yaman

    2014-01-01

    A 27-year-old man with progressive bilateral visual decline was diagnosed to have Bietti's crystalline dystrophy (BCD). Fluorescein angiography revealed bilateral petaloid type late hyperfluorescence implicating concurrent cystoid macular edema (CME). Optical coherence tomography exhibited cystoid foveal lacunas OU. During the follow-up of six years, intraretinal crystals reduced in amount but CME persisted angiographically and tomographically. CME is among the rare macular features of BCD in...

  17. Bietti’ Crystalline Retinal Dystrophy: A Case Report

    Directory of Open Access Journals (Sweden)

    Muhammed Şahin

    2016-03-01

    Full Text Available Bietti’ crystalline retinal dystrophy (BCD is a rare, auto­somal, recessively inherited disorder, characterized by the deposition of yellow crystals in the corneal limbus and retina. In this paper we aimed to present a pediatric case with BCD, with clinical, electrophysiological and spectral domain optical coherence tomography (SD-OCT findings and discuss BCD with the light of the literature. J Clin Exp Invest 2016; 7 (1: 94-97

  18. Controlled synthesis of single-crystalline graphene

    Directory of Open Access Journals (Sweden)

    Wang Xueshen

    2014-02-01

    Full Text Available This paper reports the controlled synthesis of single-crystalline graphene on the back side of copper foil using CH4 as the precursor. The influence of growth time and the pressure ratio of CH4/H2 on the structure of graphene are examined. An optimized polymer-assisted method is used to transfer the synthesized graphene onto a SiO2/Si substrate. Scanning electron microscopy and Raman spectroscopy are used to characterize the graphene.

  19. The elastic properties of crystalline syndiotactic polypropylene

    Directory of Open Access Journals (Sweden)

    Paul Unwin

    1998-01-01

    Full Text Available The ability to predict the ultimate mechanical stiffness of a polymer is of considerable value because this provides a good indication of the effort which might justifiably be expended either in polymer synthesis or in polymer engineering to produce optimum polymer structures. Generally, the best mechanical properties are identified with those of the crystalline structure, so the problem is essentially one of measuring or predicting the crystal properties.

  20. Effect of polylactic acid crystallinity on its electret properties

    Science.gov (United States)

    Guzhova, A. A.; Galikhanov, M. F.; Kuznetsova, N. V.; Petrov, V. A.; Khairullin, R. Z.

    2016-09-01

    Electret properties of the polylactic acid films with different degree of crystallinity due to different cooling and annealing conditions were studied. Samples with the higher degree of crystallinity showed more stable electret characteristics resulting from amorphous-crystalline interface boundary growth and capturing bigger amount of injected charge carriers by volume energy traps.

  1. Crystallinity in starch plastics: consequences for material properties

    NARCIS (Netherlands)

    Vliegenthart, J.F.G.; Soest, J.J.G. van

    1997-01-01

    The processing of starches with biodegradable additives has made biodegradable plastics suitable for a number of applications. Starch plastics are partially crystalline as a result of residual crystallinity and the recrystallization of amylose and amylopectin. Such crystallinity is a key determinant

  2. Fracture of polypropylene: 2. the effect of the crystallinity

    NARCIS (Netherlands)

    van der Wal, A.; Wal, A.; Mulder, J.J.; Gaymans, R.J.

    1998-01-01

    The effect of crystallinity on the fracture behaviour of polypropylene was studied under impact conditions. The crystallinity was varied by taking low- and high-isotactic polypropylenes and mixtures thereof. The crystallinity ranged from 31 to 53 wt%. The fracture behaviour was studied as a function

  3. PREPARATION AND CHARACTERIZATION OF POLY-CRYSTALLINE SILICON THIN FILM

    Institute of Scientific and Technical Information of China (English)

    Y.F. Hu; H. Shen; Z.Y. Liu; L.S. Wen

    2003-01-01

    Poly-crystalline silicon thin film has big potential of reducing the cost of solar cells.In this paper the preparation of thin film is introduced, and then the morphology of poly-crystalline thin film is discussed. On the film we developed poly-crystalline silicon thin film solar cells with efficiency up to 6. 05% without anti-reflection coating.

  4. Stamp forming optimization for formability and crystallinity

    Science.gov (United States)

    Donderwinkel, T. G.; Rietman, B.; Haanappel, S. P.; Akkerman, R.

    2016-10-01

    The stamp forming process is well suited for high volume production of thermoplastic composite parts. The process can be characterized as highly non-isothermal as it involves local quench-cooling of a molten thermoplastic composite blank where it makes contact with colder tooling. The formability of the thermoplastic composite depends on the viscoelastic material behavior of the matrix material, which is sensitive to temperature and degree of crystallinity. An experimental study was performed to determine the effect of temperature and crystallinity on the storage modulus during cooling for a woven glass fiber polyamide-6 composite material. An increase of two decades in modulus was observed during crystallization. As this will significantly impede the blank formability, the onset of crystallization effectively governs the time available for forming. Besides the experimental work, a numerical model is developed to study the temperature and crystallinity throughout the stamp forming process. A process window can be determined by feeding the model with the experimentally obtained data on crystallization.

  5. Thermal and Chemical Stability of Crystalline Silicotitanate Sorbent

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, P.A.

    2000-10-04

    The Savannah River Site (SRS) is evaluating technologies for removing radioactive cesium ({sup 137}Cs) from the supernate solutions stored in the high-level waste tanks at the site. Crystalline silicotitanate sorbent (IONSIV IE-911,{reg_sign} UOP LLC, Des Plaines, IL), which is very effective at removing cesium from high-salt solution, is one of three technologies currently being tested. Because of the extremely high inventory of {sup 137}Cs expected for the large columns of crystalline silicotitanate (CST) that would be used for treating the SRS supernate, any loss of flow or cooling to the columns could result in high temperatures from radiolytic heating. Also, even for normal operation, the CST would be exposed to the supernates for up to a year before being removed. Small-scale tests using simulant solutions were used to determine the long-term stability of the CST to the solutions at various temperatures. In the tests performed in this study, the cesium capacity of the CST decreased significantly (76%) as the temperature of the simulant and CST during loading was increased from 23 to 80 C. CST exposed to recirculating SRS average simulant solution at room temperature in a column test showed a slow decrease in cesium loading capacity (measured at 23 C), with a drop of 30% for CST from the top of the bed and 13% for CST from the bottom of the bed after a 12-month period of exposure. A similar column test using a high-pH salt solution did not show any change in the cesium capacity of the CST. An increase was noted in pressure drop through the column using average simulant, but no change was observed for the column using high-pH salt solution.

  6. Deleterious role of trace elements - Silica and lead in the development of chronic kidney disease.

    Science.gov (United States)

    Mascarenhas, Starlaine; Mutnuri, Srikanth; Ganguly, Anasuya

    2017-06-01

    Chronic-Kidney-Disease of Unknown-etiology (CKDu) has been reported in developing-countries like Sri-Lanka, India and Central-America without sparing the Indian sub-district (namely Canacona) located in south-Goa. The disease etiology is unlinked to common causes of diabetes and hypertension and assumed to be environmentally induced due to its asymptomatic-nature and occurrence in groundwater relying communities. This study aimed to understand environmental risk-factors underlying CKDu-etiology using Indian sub-district (Canacona) as case-study. Biochemical-analysis of CKDu-affected and non-affected individual's blood and detailed hydro-geochemical analyses of CKDu-affected and non-affected region's groundwater (drinking-water)were conducted. Trace geogenic-element-silica was highly dominant in affected-region's groundwater, thus its nephrotoxic-potential was analysed via in-vitro cytotoxicity-assays on human-kidney-cell-lines. All CKDu-affected-subjects showed increased-levels of serum-urea (52.85 mM),creatinine (941.5 μM),uric-acid (1384.5 μM), normal blood-glucose (4.65 mM), being distinct biomarkers of environmentally-induced CKD-'chronic-tubulo-interstitial-nephritis'. Affected-subjects reported high blood-lead levels (1.48 μM)suggesting direct-nephrotoxicity resulting in impaired blood-clearance and also exhibits indirect-nephrotoxicity by disrupting calcium-homeostasis causing skeletal-disorders and prolonged-consumption of NSAID's (pain-alleviation), indirectly causing renal-damage. Affected-region's groundwater was acidic (pH-5.6), resulting in borderline-lead (9.98 μgL(-1)) and high-silica (115.5 mgL(-1))contamination. Silica's bio-availability (determining its nephrotoxicity) was enhanced at groundwater's acidic-pH and Ca-Mg-deficient-composition (since these cations complex with silica reducing bioavailability). Silica exhibited renal-proximal-tubular-cytotoxicity on long-term exposure comparable with affected-region's groundwater silica

  7. Hard Coal Fly Ash and Silica-Effect of Fine Particulate Matter Deposits on Brassica chinensis

    Directory of Open Access Journals (Sweden)

    Christian Ulrichs

    2009-01-01

    Full Text Available Problem statement: One focus in recent atmospheric pollution research is on fine Particle Matter (PM, especially as result of increasing traffic and anthropogenic activity in urban areas. Here, the impact on animal and human health has been in the center of many studies. Despite the fact that PM depositions can affect plants on the long term, there are only few studies about the impact on plants conducted. Approach: Therefore we studied the impact of PM on plants, using naturally occurring silica dusts (diatomaceous earth and hard Coal Fly Ash (CFA from burning processes. Dusts were applied onto Brassica chinensis L. using a simple duster (covering upper leaf surfaces or electrostatically (covering leaf upper and -underside. Results: Main components of the tested CFA are SO42-, K, Ca and NH4+. The pH value of eluates was found to be around 9.5 in CFA and 5.7 in silica. B. chinensis was insensitive towards the high pH and showed no growth reduction when grown in silica or CFA substrate. PM deposition on leaf surfaces results through shading in a reduced photosynthetic activity. The reduction is relatively higher at higher light intensities. Photosynthesis stays reduced after removal of silica PM from leaf surfaces. We assume that stomata get cloaked by small particles and that silica absorbs lipids from the epicuticle resulting in a general stress reaction. Smaller sized silica particles resulted in a higher reduction of CO2-absorption. Next to particle size is the photosynthesis negatively correlated with exposure time for silica PM. The chlorophyll fluorescence data indicate that dust-covered leaves exhibited significantly lower quantum yield of PS II and a reduced quantum efficiency of PS II and therefore supported the gas exchange data. Conclusion: Reduced photosynthetic performance would be expected to reduce growth and productivity of B. chinensis. In contrast to silica hard coal fly ash

  8. Altered Gene Transcription in Human Cells Treated with Ludox® Silica Nanoparticles

    Directory of Open Access Journals (Sweden)

    Caterina Fede

    2014-08-01

    Full Text Available Silica (SiO2 nanoparticles (NPs have found extensive applications in industrial manufacturing, biomedical and biotechnological fields. Therefore, the increasing exposure to such ultrafine particles requires studies to characterize their potential cytotoxic effects in order to provide exhaustive information to assess the impact of nanomaterials on human health. The understanding of the biological processes involved in the development and maintenance of a variety of pathologies is improved by genome-wide approaches, and in this context, gene set analysis has emerged as a fundamental tool for the interpretation of the results. In this work we show how the use of a combination of gene-by-gene and gene set analyses can enhance the interpretation of results of in vitro treatment of A549 cells with Ludox® colloidal amorphous silica nanoparticles. By gene-by-gene and gene set analyses, we evidenced a specific cell response in relation to NPs size and elapsed time after treatment, with the smaller NPs (SM30 having higher impact on inflammatory and apoptosis processes than the bigger ones. Apoptotic process appeared to be activated by the up-regulation of the initiator genes TNFa and IL1b and by ATM. Moreover, our analyses evidenced that cell treatment with LudoxÒ silica nanoparticles activated the matrix metalloproteinase genes MMP1, MMP10 and MMP9. The information derived from this study can be informative about the cytotoxicity of Ludox® and other similar colloidal amorphous silica NPs prepared by solution processes.

  9. Altered gene transcription in human cells treated with Ludox® silica nanoparticles.

    Science.gov (United States)

    Fede, Caterina; Millino, Caterina; Pacchioni, Beniamina; Celegato, Barbara; Compagnin, Chiara; Martini, Paolo; Selvestrel, Francesco; Mancin, Fabrizio; Celotti, Lucia; Lanfranchi, Gerolamo; Mognato, Maddalena; Cagnin, Stefano

    2014-08-28

    Silica (SiO2) nanoparticles (NPs) have found extensive applications in industrial manufacturing, biomedical and biotechnological fields. Therefore, the increasing exposure to such ultrafine particles requires studies to characterize their potential cytotoxic effects in order to provide exhaustive information to assess the impact of nanomaterials on human health. The understanding of the biological processes involved in the development and maintenance of a variety of pathologies is improved by genome-wide approaches, and in this context, gene set analysis has emerged as a fundamental tool for the interpretation of the results. In this work we show how the use of a combination of gene-by-gene and gene set analyses can enhance the interpretation of results of in vitro treatment of A549 cells with Ludox® colloidal amorphous silica nanoparticles. By gene-by-gene and gene set analyses, we evidenced a specific cell response in relation to NPs size and elapsed time after treatment, with the smaller NPs (SM30) having higher impact on inflammatory and apoptosis processes than the bigger ones. Apoptotic process appeared to be activated by the up-regulation of the initiator genes TNFa and IL1b and by ATM. Moreover, our analyses evidenced that cell treatment with LudoxÒ silica nanoparticles activated the matrix metalloproteinase genes MMP1, MMP10 and MMP9. The information derived from this study can be informative about the cytotoxicity of Ludox® and other similar colloidal amorphous silica NPs prepared by solution processes.

  10. Lung toxicities of core–shell nanoparticles composed of carbon, cobalt, and silica

    Science.gov (United States)

    Al Samri, Mohammed T; Silva, Rafael; Almarzooqi, Saeeda; Albawardi, Alia; Othman, Aws Rashad Diab; Al Hanjeri, Ruqayya SMS; Al Dawaar, Shaikha KM; Tariq, Saeed; Souid, Abdul-Kader; Asefa, Tewodros

    2013-01-01

    We present here comparative assessments of murine lung toxicity (biocompatibility) after in vitro and in vivo exposures to carbon (C–SiO2-etched), carbon–silica (C–SiO2), carbon–cobalt–silica (C–Co–SiO2), and carbon–cobalt oxide–silica (C–Co3O4–SiO2) nanoparticles. These nanoparticles have potential applications in clinical medicine and bioimaging, and thus their possible adverse events require thorough investigation. The primary aim of this work was to explore whether the nanoparticles are biocompatible with pneumatocyte bioenergetics (cellular respiration and adenosine triphosphate content). Other objectives included assessments of caspase activity, lung structure, and cellular organelles. Pneumatocyte bioenergetics of murine lung remained preserved after treatment with C–SiO2-etched or C–SiO2 nanoparticles. C–SiO2-etched nanoparticles, however, increased caspase activity and altered lung structure more than C–SiO2 did. Consistent with the known mitochondrial toxicity of cobalt, both C–Co–SiO2 and C–Co3O4–SiO2 impaired lung tissue bioenergetics. C–Co–SiO2, however, increased caspase activity and altered lung structure more than C–Co3O4–SiO2. The results indicate that silica shell is essential for biocompatibility. Furthermore, cobalt oxide is the preferred phase over the zerovalent Co(0) phase to impart biocompatibility to cobalt-based nanoparticles. PMID:23658487

  11. SYNTHESIS AND COATING OF ORDERED MESOPOROUS SILICA

    Institute of Scientific and Technical Information of China (English)

    Wei Guo; Guangsheng Luo; Yujun Wang

    2003-01-01

    1,3,5-trimethyl benzene (TMB) was used as organic swelling agent in O/W emulsions to template ultra-large mesoporous materials using the hydrothermal method. The silicas with well-defined mesopores and hydrothermally robust framework were characterized by X-ray diffraction, transmission electron microscopy and BET surface area analysis. The influence of the quantity of TMB during preparation was studied. It has been found that the TMB/CTAB ratio must be controlled for producing high pore volume materials. Polysulfone (PSU), as the usual extraction agent, was coated on the silicas with the solvent evaporation method to produce a solid separation medium. The adsorptivity and the surface area of the coated MCM were determined: 10% PSU coated MCM adsorbed twice as much phenol as the uncoated material, reaching 0.5 mg/g silica. It was found that the surface area of the coated material decreased rapidly with an increase of the PSU loading.

  12. Thermal resistance between amorphous silica nanoparticles

    Science.gov (United States)

    Meng, Fanhe; Elsahati, Muftah; Liu, Jin; Richards, Robert F.

    2017-05-01

    Nanoparticle-based materials have been used as thermal insulation in a variety of macroscale and microscale applications. In this work, we investigate the heat transfer between nanoparticles using non-equilibrium molecular dynamics simulations. We calculate the total thermal resistance and thermal boundary resistance between adjacent amorphous silica nanoparticles. Numerical results are compared to interparticle resistances determined from experimental measurements of heat transfer across packed silica nanoparticle beds. The thermal resistance between nanoparticles is shown to increase rapidly as the particle contact radius decreases. More significantly, the interparticle resistance depends strongly on the forces between particles, in particular, the presence or absence of chemical bonds between nanoparticles. In addition, the effect of interfacial force strength on thermal resistance increases as the nanoparticle diameter decreases. The simulations results are shown to be in good agreement with experimental results for 20 nm silica nanoparticles.

  13. Fused silica windows for solar receiver applications

    Science.gov (United States)

    Hertel, Johannes; Uhlig, Ralf; Söhn, Matthias; Schenk, Christian; Helsch, Gundula; Bornhöft, Hansjörg

    2016-05-01

    A comprehensive study of optical and mechanical properties of quartz glass (fused silica) with regard to application in high temperature solar receivers is presented. The dependence of rupture strength on different surface conditions as well as high temperature is analyzed, focussing particularly on damage by devitrification and sandblasting. The influence of typical types of contamination in combination with thermal cycling on the optical properties of fused silica is determined. Cleaning methods are compared regarding effectiveness on contamination-induced degradation for samples with and without antireflective coating. The FEM-aided design of different types of receiver windows and their support structure is presented. A large-scale production process has been developed for producing fused silica dome shaped windows (pressurized window) up to a diameter of 816 mm. Prototypes were successfully pressure-tested in a test bench and certified according to the European Pressure Vessel Directive.

  14. Functional Films from Silica/Polymer Nanoparticles

    Directory of Open Access Journals (Sweden)

    Tânia Ribeiro

    2014-05-01

    Full Text Available High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs in the polymeric matrices, it is possible to obtain hybrid polymer films with increased tensile strength and impact resistance, without decreasing the flexural properties of the polymer matrix. The SiNPs can further be used as carriers to impart other functionalities (optical, etc. to the hybrid films. By using polymer-coated SiNPs, it is possible to reduce particle aggregation in the films and, thus, achieve more homogeneous distributions of the inorganic components and, therefore, better properties. On the other hand, by coating polymer particles with silica, one can create hierarchically structured materials, for example to obtain superhydrophobic coatings. In this review, we will cover the latest developments in films prepared from hybrid polymer/silica functional systems.

  15. Electrical transport in crystalline phase change materials

    Energy Technology Data Exchange (ETDEWEB)

    Woda, Michael

    2012-01-06

    In this thesis, the electrical transport properties of crystalline phase change materials are discussed. Phase change materials (PCM) are a special class of semiconducting and metallic thin film alloys, typically with a high amount of the group five element antimony or the group six element tellurium, such as Ge{sub 2}Sb{sub 2}Te{sub 5}. The unique property portfolio of this material class makes it suitable for memory applications. PCMs reveal fast switching between two stable room-temperature phases (amorphous and crystalline) realized by optical laser or electrical current pulses in memory devices. Additionally, a pronounced property contrast in form of optical reflectivity and electrical conductivity between the amorphous and crystalline phase is the characteristic fingerprint of PCMs. The emerging electrical solid state memory PCRAM is a very promising candidate to replace Flash memory in the near future or to even become a universal memory, which is non-volatile and shows the speed and cyclability of DRAM. One of the main technological challenges is the switching process into the amorphous state, which is the most power demanding step. In order to reduce the switching power, the crystalline resistivity needs to be increased at a given voltage. Thus understanding and tayloring of this property is mandatory. In this work, first the technological relevance, i.e. optical and electrical memory concepts based on PCMs are introduced. Subsequently a description of the physical properties of PCMs in four categories is given. Namely, structure, kinetics, optical properties and electrical properties are discussed. Then important recent developments such as the identification of resonant bonding in crystalline PCMs and a property predicting coordination scheme are briefly reviewed. The following chapter deals with the theoretical background of electrical transport, while the next chapter introduces the experimental techniques: Sputtering, XRR, XRD, DSC, thermal annealing

  16. Epoxy + liquid crystalline epoxy coreacted network

    Science.gov (United States)

    Punchaipetch, Prakaipetch

    2000-10-01

    Molecular reinforcement through in-situ polymerization of liquid crystalline epoxies (LCEs) and a non-liquid crystalline epoxy has been investigated. Three LCEs: diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) and digylcidyl ether of 4-hydroxyphenyl-4″-hydroxybiphenyl-4 '-carboxylate (DGE-HHC), were synthesized and blended with diglycidyl ether of bisphenol F (DGEBP-F) and subsequently cured with anhydride and amine curing agents. Curing kinetics were determined using differential scanning calorimetry (DSC). Parameters for autocatalytic curing kinetics of both pure monomers and blended systems were determined. The extent of cure for both monomers was monitored by using Fourier transform infrared spectroscopy (FT-IR). The glass transitions were evaluated as a function of composition using DSC and dynamic mechanical analysis (DMA). The results show that the LC constituent affects the curing kinetics of the epoxy resin and that the systems are highly miscible. The effects of molecular reinforcement of DGEBP-F by DGE-DHBP and DGE-HHC were investigated. The concentration of the liquid crystalline moiety affects mechanical properties. Tensile, impact and fracture toughness tests results are evaluated. Scanning electron microscopy of the fracture surfaces shows changes in failure mechanisms compared to the pure components. Results indicate that mechanical properties of the blended samples are improved already at low concentration by weight of the LCE added into epoxy resin. The improvement in mechanical properties was found to occur irrespective of the absence of liquid crystallinity in the blended networks. The mechanism of crack study indicates that crack deflection and crack bridging are the mechanisms in case of LC epoxy. In case of LC modified epoxy, the crack deflection is the main mechanism. Moreover, the effect of coreacting an epoxy with a reactive monomer liquid crystalline epoxy as a matrix for glass fiber composites was investigated. Mechanical

  17. Properties of silica from rice husk and rice husk ash and their utilization for zeolite y synthesis

    OpenAIRE

    Jan-Jezreel F. Saceda; Leon,Rizalinda L. de; Kamolwan Rintramee; Sanchai Prayoonpokarach; Jatuporn Wittayakun

    2011-01-01

    This study compared properties of silica (SiO2) from rice husk (RH) and rice husk ash (RHA) extracted by acid- and heat-treatment. The SiO2 from RH was in amorphous phase with nearly 100% purity while that from RHA was in crystalline phase with 97.56% purity. Both extracted SiO2 were used in the synthesis of zeolite NaY but that from RH was better due to the efficiency in product recovery and simplicity of extraction. After the NaY was exchanged to NH4Y and calcined to convert to HY, the prod...

  18. Loading amorphous Asarone in mesoporous silica SBA-15 through supercritical carbon dioxide technology to enhance dissolution and bioavailability.

    Science.gov (United States)

    Zhang, Zhengzan; Quan, Guilan; Wu, Qiaoli; Zhou, Chan; Li, Feng; Bai, Xuequn; Li, Ge; Pan, Xin; Wu, Chuanbin

    2015-05-01

    The aim of this study was to load amorphous hydrophobic drug into ordered mesoporous silica (SBA-15) by supercritical carbon dioxide technology in order to improve the dissolution and bioavailability of the drug. Asarone was selected as a model drug due to its lipophilic character and poor bioavailability. In vitro dissolution and in vivo bioavailability of the obtained Asarone-SBA-15 were significantly improved as compared to the micronized crystalline drug. This study offers an effective, safe, and environmentally benign means of solving the problems relating to the solubility and bioavailability of hydrophobic molecules.

  19. Vacuum arc on the polycrystalline silica cathode

    Directory of Open Access Journals (Sweden)

    D. V. Duhopel'nikov

    2014-01-01

    Full Text Available Thin films of silica and its compounds are used in modern technology to produce Li-ion batteries, wear-resistant and protective coatings, thin-films insulators, etc. This coating is produced with CVD methods, with magnetron sputtering systems or with electron-beam evaporation. The vacuum arc evaporation method, presently, is not used.The paper demonstrates a possibility for a long-term operation of vacuum arc evaporator with polycrystalline silica-aluminum alloy (90% of silica cathode and with magnetic system to create a variable form of arch-like magnetic field on the cathode surface. It was shown that archlike configuration of magnetic field provides a stable discharge and uniform cathode spots moving with the velocities up to 5 m/s with magnetic fields induction about 10 mT. Thus, there is no local melting of the cathode, and this provides its long-term work without chips, cracks and destruction. Cathodes spots move over the cathode surface leaving t big craters with melted edges on its surface. The craters size was 150-450μm. The cathode spot movement character and the craters on the cathode surface were like the spots movement, when working on the copper or aluminum cathodes. With the magnetic field induction less than 1 mT, the cathode spots movement was the same as that of on the silica mono-crystal without magnetic field. Thus, the discharge volt-ampere characteristics for different values of magnetic fields were obtained. Voltampere characteristics were increasing and were shifted to the higher voltage with increasing magnetic field. The voltage was 18.7-26.5 V for the arc current 30-140 A.So, it was confirmed that vacuum arc evaporation method could be used for effective evaporation of silica and silica-based alloys and for thin films deposition of this materials.

  20. Adsorption of mercury ions by mercapto-functionalized amorphous silica

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Quintanilla, Damian; Hierro, Isabel del; Fajardo, Mariano; Sierra, Isabel [Universidad Rey Juan Carlos, Departamento de Tecnologia Quimica y Ambiental, E.S.C.E.T, Mostoles, Madrid (Spain); Carrillo-Hermosilla, Fernando [Universidad de Castilla-La Mancha, Departamento de Quimica Inorganica, Organica y Bioquimica, Facultad de Quimicas, Ciudad Real (Spain)

    2006-02-01

    Amorphous silicas have been functionalized by two different methods. In the heterogeneous route the silylating agent, 3-chloropropyltriethoxysilane, was initially immobilized onto the silica surface to give the chlorinated silica Cl-Sil. In a second reaction, multifunctionalized N,S donor compounds were incorporated to obtain the functionalized silicas, which are denoted as L-Sil-Het (where L=mercaptothiazoline, mercaptopyridine or mercaptobenzothiazole). In the homogeneous route, the functionalization was achieved through a one-step reaction between the silica and an organic ligand containing the chelating functions; this gave the modified silicas denoted as L-Sil-Hom. The functionalized silicas were characterized by elemental analysis, IR spectroscopy and thermogravimetry. These materials were employed as adsorbents for mercury cations from aqueous and acetone solutions at room temperature. The results indicate that, in all cases, mercury adsorption was higher in the modified silicas prepared by the homogeneous method. (orig.)