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Sample records for iarc reevaluates silica

  1. The IARC monographs: critics and controversy.

    PubMed

    Samet, Jonathan M

    2015-07-01

    The monograph program of the International Agency for Research on Cancer (IARC), which relies on the efforts of volunteer Working Groups, uses a transparent approach to evaluate the carcinogenicity of agents for which scoping has determined that there is sufficient evidence to warrant a review. Because of the potentially powerful implications of the conclusions of the monographs and the sometimes challenging nature of the evidence reviewed, the monographs and the IARC process have been criticized from time to time. This commentary describes the IARC monograph process and addresses recent criticisms of the program, drawing on a recent defense of the program authored by 124 researchers. These authors concluded that the IARC processes are robust and transparent and not flawed and biased as suggested by some critics. PMID:25943987

  2. [IARC evaluations: how are they conducted and what suggestions are derived therefrom?].

    PubMed

    Piolatto, P G; Pira, E

    2007-01-01

    The IARC Monographs on the Evaluation of Carcinogenic Risks to Humans are considered by several Institutions a point of reference for the prevention of adverse effects (namely cancer) of occupational exposures. The conclusions which lead to the Classification of a substance or an industrial process are the results of a vote within a Working Group of experts and are expressed in terms of "evidence" based on both epidemiological and experimental data or "other relevant data". Several points are discussed which include the methods of identification of the experts, the criteria of evaluation of the available data, the meaning of some definitions and finally the impact of IARC conclusions and Classification on Public Health regulations and secondarily on compensation procedures or trial decisions. Three recent examples regarding the Classification of Free Crystalline Silica, Shift-Work and Vinyl Chloride Monomer, which cannot be accepted as such without some criticism, are reported. In conclusion the Authors appreciate the effort of the IARC to provide a source of information which "may assist national and international authorities in making risk assessments and in formulating decisions concerning any necessary preventive measures". However, they suggest that the IARC "overall evaluation" should not be taken as confidently as if no doubt at all would exist on the final statement and the consequent Classification. Some suggestions as to the solution of the question are also provided. PMID:18409257

  3. "IARC group 2B Carcinogens" reported in cigarette mainstream smoke.

    PubMed

    Smith, C J; Perfetti, T A; Mullens, M A; Rodgman, A; Doolittle, D J

    2000-09-01

    In the third and final part of a series surveying the international literature on the "IARC carcinogens" in cigarette mainstream smoke, the "IARC Group 2B carcinogens" are reviewed. A search of the published literature shows that of 227 chemical components classified as Group 2B, that is, "possible carcinogens," by the International Agency for Research on Cancer (IARC), 48 have previously been reported in cigarette mainstream smoke. Owing to its highly interactive molecular nature, removal from or inhibition of a given mutagenic or carcinogenic chemical within the complex aerosol mixture cannot reliably be predicted to reduce either the overall mutagenicity or carcinogenicity. However, in the absence of experimental data demonstrating an increase in adverse biological activity resulting from removal or inhibition of a potentially carcinogenic constituent, negation of the activity of the potential carcinogen may be considered as a desirable circumstance.

  4. IARC Classification of Cell Phones as “Possible Carcinogen”

    Cancer.gov

    The World Health Organization’s International Agency for Research on Cancer (IARC) today classified mobile phone use and other radiofrequency electromagnetic fields as a possible carcinogen (group 2B). This is neither new research nor at odds with previous findings.

  5. Research Recommendations for Selected IARC-Classified Agents

    EPA Science Inventory

    History of the NORA process and framework for the meeting. This is a concerted effort to identify means of reducing the insufficiency of available data for classifying particular agents in the International Agency for Research on Cancer (IARC) system by identifying information n...

  6. IARC Monographs: 40 Years of Evaluating Carcinogenic Hazards to Humans

    PubMed Central

    Blair, Aaron; Vineis, Paolo; Ahrens, Wolfgang; Andersen, Aage; Anto, Josep M.; Armstrong, Bruce K.; Baccarelli, Andrea A.; Beland, Frederick A.; Berrington, Amy; Bertazzi, Pier Alberto; Birnbaum, Linda S.; Brownson, Ross C.; Bucher, John R.; Cantor, Kenneth P.; Cardis, Elisabeth; Cherrie, John W.; Christiani, David C.; Cocco, Pierluigi; Coggon, David; Comba, Pietro; Demers, Paul A.; Dement, John M.; Douwes, Jeroen; Eisen, Ellen A.; Engel, Lawrence S.; Fenske, Richard A.; Fleming, Lora E.; Fletcher, Tony; Fontham, Elizabeth; Forastiere, Francesco; Frentzel-Beyme, Rainer; Fritschi, Lin; Gerin, Michel; Goldberg, Marcel; Grandjean, Philippe; Grimsrud, Tom K.; Gustavsson, Per; Haines, Andy; Hartge, Patricia; Hansen, Johnni; Hauptmann, Michael; Heederik, Dick; Hemminki, Kari; Hemon, Denis; Hertz-Picciotto, Irva; Hoppin, Jane A.; Huff, James; Jarvholm, Bengt; Kang, Daehee; Karagas, Margaret R.; Kjaerheim, Kristina; Kjuus, Helge; Kogevinas, Manolis; Kriebel, David; Kristensen, Petter; Kromhout, Hans; Laden, Francine; Lebailly, Pierre; LeMasters, Grace; Lubin, Jay H.; Lynch, Charles F.; Lynge, Elsebeth; ‘t Mannetje, Andrea; McMichael, Anthony J.; McLaughlin, John R.; Marrett, Loraine; Martuzzi, Marco; Merchant, James A.; Merler, Enzo; Merletti, Franco; Miller, Anthony; Mirer, Franklin E.; Monson, Richard; Nordby, Karl-Cristian; Olshan, Andrew F.; Parent, Marie-Elise; Perera, Frederica P.; Perry, Melissa J.; Pesatori, Angela Cecilia; Pirastu, Roberta; Porta, Miquel; Pukkala, Eero; Rice, Carol; Richardson, David B.; Ritter, Leonard; Ritz, Beate; Ronckers, Cecile M.; Rushton, Lesley; Rusiecki, Jennifer A.; Rusyn, Ivan; Samet, Jonathan M.; Sandler, Dale P.; de Sanjose, Silvia; Schernhammer, Eva; Costantini, Adele Seniori; Seixas, Noah; Shy, Carl; Siemiatycki, Jack; Silverman, Debra T.; Simonato, Lorenzo; Smith, Allan H.; Smith, Martyn T.; Spinelli, John J.; Spitz, Margaret R.; Stallones, Lorann; Stayner, Leslie T.; Steenland, Kyle; Stenzel, Mark; Stewart, Bernard W.; Stewart, Patricia A.; Symanski, Elaine; Terracini, Benedetto; Tolbert, Paige E.; Vainio, Harri; Vena, John; Vermeulen, Roel; Victora, Cesar G.; Ward, Elizabeth M.; Weinberg, Clarice R.; Weisenburger, Dennis; Wesseling, Catharina; Weiderpass, Elisabete; Zahm, Shelia Hoar

    2015-01-01

    Background: Recently, the International Agency for Research on Cancer (IARC) Programme for the Evaluation of Carcinogenic Risks to Humans has been criticized for several of its evaluations, and also for the approach used to perform these evaluations. Some critics have claimed that failures of IARC Working Groups to recognize study weaknesses and biases of Working Group members have led to inappropriate classification of a number of agents as carcinogenic to humans. Objectives: The authors of this Commentary are scientists from various disciplines relevant to the identification and hazard evaluation of human carcinogens. We examined criticisms of the IARC classification process to determine the validity of these concerns. Here, we present the results of that examination, review the history of IARC evaluations, and describe how the IARC evaluations are performed. Discussion: We concluded that these recent criticisms are unconvincing. The procedures employed by IARC to assemble Working Groups of scientists from the various disciplines and the techniques followed to review the literature and perform hazard assessment of various agents provide a balanced evaluation and an appropriate indication of the weight of the evidence. Some disagreement by individual scientists to some evaluations is not evidence of process failure. The review process has been modified over time and will undoubtedly be altered in the future to improve the process. Any process can in theory be improved, and we would support continued review and improvement of the IARC processes. This does not mean, however, that the current procedures are flawed. Conclusions: The IARC Monographs have made, and continue to make, major contributions to the scientific underpinning for societal actions to improve the public’s health. Citation: Pearce N, Blair A, Vineis P, Ahrens W, Andersen A, Anto JM, Armstrong BK, Baccarelli AA, Beland FA, Berrington A, Bertazzi PA, Birnbaum LS, Brownson RC, Bucher JR, Cantor KP

  7. An IARC evaluation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans as risk factors in human carcinogenesis.

    PubMed Central

    McGregor, D B; Partensky, C; Wilbourn, J; Rice, J M

    1998-01-01

    The International Agency for Research on Cancer (IARC) Monographs program reevaluated polychlorinated dibenzo-p-dioxins and evaluated polychlorinated dibenzofurans as possible carcinogenic hazards to humans in February 1997, using the most recent epidemiologic data on exposed human populations, experimental carcinogenicity bioassays in laboratory animals, and supporting evidence on relevant mechanisms of carcinogenesis. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) was evaluated as carcinogenic to humans (IARC group 1 classification) on the basis of limited evidence of carcinogenicity to humans derived from follow-up of workers who had been heavily exposed in industrial accidents and sufficient evidence of carcinogenicity in experimental animals. The evaluation also considered the following supporting evidence: TCDD is a multisite carcinogen in experimental animals and has been shown by several lines of evidence to act through a mechanism involving the aryl hydrocarbon receptor; this receptor is highly conserved in an evolutionary sense and functions the same way in humans as in experimental animals; tissue concentrations of TCDD are similar in heavily exposed human populations in which an increased overall cancer risk was observed and in exposed rats that developed tumors in carcinogenicity tests. Other polychlorinated dibenzo-p-dioxins, the nonchlorinated dibenzo-p-dioxin, and polychlorinated dibenzofurans were evaluated as not classifiable as to their carcinogenicity to humans (group 3). PMID:9599727

  8. Do people understand IARC's 2B categorization of RF fields from cell phones?

    PubMed

    Wiedemann, Peter M; Boerner, Franziska U; Repacholi, Michael H

    2014-07-01

    In May 2011, the International Agency on Cancer in Research (IARC) issued an official statement concluding that cell phone usage was "possibly carcinogenic to humans." There have been considerable doubts that non-experts and experts alike fully understood what IARC's categorization actually meant, as "possibly carcinogenic" can be interpreted in many ways. The present study is based on an online survey indicating that both the characterization of the probability of carcinogenicity, as well as the description of the risk increase given in the IARC press release, was mostly misunderstood by study participants. Respondents also greatly overestimated the magnitude of the potential risk. Our study results showed that IARC needs to improve their scientific communications.

  9. TP53 Variations in Human Cancers: New Lessons from the IARC TP53 Database and Genomics Data.

    PubMed

    Bouaoun, Liacine; Sonkin, Dmitriy; Ardin, Maude; Hollstein, Monica; Byrnes, Graham; Zavadil, Jiri; Olivier, Magali

    2016-09-01

    TP53 gene mutations are one of the most frequent somatic events in cancer. The IARC TP53 Database (http://p53.iarc.fr) is a popular resource that compiles occurrence and phenotype data on TP53 germline and somatic variations linked to human cancer. The deluge of data coming from cancer genomic studies generates new data on TP53 variations and attracts a growing number of database users for the interpretation of TP53 variants. Here, we present the current contents and functionalities of the IARC TP53 Database and perform a systematic analysis of TP53 somatic mutation data extracted from this database and from genomic data repositories. This analysis showed that IARC has more TP53 somatic mutation data than genomic repositories (29,000 vs. 4,000). However, the more complete screening achieved by genomic studies highlighted some overlooked facts about TP53 mutations, such as the presence of a significant number of mutations occurring outside the DNA-binding domain in specific cancer types. We also provide an update on TP53 inherited variants including the ones that should be considered as neutral frequent variations. We thus provide an update of current knowledge on TP53 variations in human cancer as well as inform users on the efficient use of the IARC TP53 Database.

  10. TP53 Variations in Human Cancers: New Lessons from the IARC TP53 Database and Genomics Data.

    PubMed

    Bouaoun, Liacine; Sonkin, Dmitriy; Ardin, Maude; Hollstein, Monica; Byrnes, Graham; Zavadil, Jiri; Olivier, Magali

    2016-09-01

    TP53 gene mutations are one of the most frequent somatic events in cancer. The IARC TP53 Database (http://p53.iarc.fr) is a popular resource that compiles occurrence and phenotype data on TP53 germline and somatic variations linked to human cancer. The deluge of data coming from cancer genomic studies generates new data on TP53 variations and attracts a growing number of database users for the interpretation of TP53 variants. Here, we present the current contents and functionalities of the IARC TP53 Database and perform a systematic analysis of TP53 somatic mutation data extracted from this database and from genomic data repositories. This analysis showed that IARC has more TP53 somatic mutation data than genomic repositories (29,000 vs. 4,000). However, the more complete screening achieved by genomic studies highlighted some overlooked facts about TP53 mutations, such as the presence of a significant number of mutations occurring outside the DNA-binding domain in specific cancer types. We also provide an update on TP53 inherited variants including the ones that should be considered as neutral frequent variations. We thus provide an update of current knowledge on TP53 variations in human cancer as well as inform users on the efficient use of the IARC TP53 Database. PMID:27328919

  11. Carcinogenic hazards from inhaled carbon black, titanium dioxide, and talc not containing asbestos or asbestiform fibers: recent evaluations by an IARC Monographs Working Group.

    PubMed

    Baan, Robert A

    2007-01-01

    In February 2006, an IARC Monographs Working Group reevaluated the carcinogenic hazards to humans of carbon black, titanium dioxide, and talc, which belong to the group of poorly soluble, low-toxicity particles. The review of the relevant literature and the evaluations by the Working Group will be published in Volume 93 of the IARC Monographs series. This article summarizes the Working Group's conclusions. Epidemiological studies among workers in carbon black production and in the rubber industry provided inadequate evidence of carcinogenicity. The overall data from cancer studies in rodents exposed to carbon black provided sufficient evidence of carcinogenicity. The Working Group evaluated carbon black as possibly carcinogenic to humans, Group 2B. Reviewing the epidemiological studies in the titanium dioxide production industry, the Working Group concluded that there is inadequate evidence of carcinogenicity. Overall, the results from rodent cancer studies with titanium dioxide were considered to provide sufficient evidence. Titanium dioxide was evaluated as possibly carcinogenic to humans, Group 2B. Epidemiological studies on talc miners and millers provided inadequate evidence of carcinogenicity of inhaled talc not containing asbestos or asbestiform fibers. The evidence from rodent cancer studies was considered limited. The Working Group evaluated inhaled talc not containing asbestos or asbestiform fibers as not classifiable as to its carcinogenicity to humans, Group 3. The Working Group noted that prolonged exposure to inhaled particles at sufficiently high concentrations in experimental animals may lead to impairment of normal clearance mechanisms in the alveolar region of the lung, resulting in a continued buildup of particles that eventually leads to excessive lung burdens accompanied by chronic alveolar inflammation. The inflammatory response may give rise to increased generation of reactive oxygen species, cell injury, cell proliferation, fibrosis

  12. Use of mechanistic data in the IARC evaluations of the carcinogenicity of polychlorinated biphenyls and related compounds.

    PubMed

    Lauby-Secretan, Béatrice; Loomis, Dana; Baan, Robert; El Ghissassi, Fatiha; Bouvard, Véronique; Benbrahim-Tallaa, Lamia; Guha, Neela; Grosse, Yann; Straif, Kurt

    2016-02-01

    The IARC Monographs are a series of scientific reviews that identify environmental factors that can increase the risk of cancer in humans. In its first part, the principles and procedures of the IARC Monographs evaluations are summarized. In a second part, we present the most recent IARC evaluation of polychlorinated biphenyls (PCBs) and polybrominated biphenyls (PBBs), performed in February 2013: PCBs and dioxin-like PCBs were both classified into group 1 "carcinogens," while PBBs were evaluated as "probably carcinogenic to humans" (group 2A). Noteworthy is that the relative contributions of different PCB congeners to the carcinogenicity of PCB mixtures are not known. The use of mechanistic data for the classification into a higher category is discussed in the context of the history of the consecutive evaluations of several related polychlorinated compounds. PMID:26077316

  13. An international literature survey of "IARC Group I carcinogens" reported in mainstream cigarette smoke.

    PubMed

    Smith, C J; Livingston, S D; Doolittle, D J

    1997-01-01

    The International Agency for Research on Cancer (IARC) currently lists 44 individual chemical agents, 12 groups or mixtures of chemicals and 13 exposure circumstances as "Group 1 human carcinogens". A comprehensive search of the published literature revealed that nine of the 44 chemical agents classified as "Group I carcinogens" by IARC have been reported to occur in mainstream cigarette smoke. The other 35 have never been reported to occur in cigarette smoke. The nine agents reported are benzene, cadmium, arsenic, nickel, chromium, 2-naphthyl-amine, vinyl chloride, 4-aminobiphenyl and beryllium. The reported yields of each of these nine agents in mainstream smoke varies widely. The range of yields reported for a given compound is influenced by the type of cigarette tested and when the analysis was conducted. In micrograms/cigarette, the ranges that have been reported for each of the nine compounds are: benzene (0.05-104), cadmium (0-6.67), arsenic (0-1.4), nickel (0-0.51), chromium (0.0002-0.5), 2-naphthylamine (0.0002-0.022), vinyl chloride (0.0013-0.0158), 4-aminobiphenyl (0.00019-0.005) and beryllium (0-0.0005). Although some of the variation in reported yields may be due to differences in analytical methodology, several correlations between the yield of a particular chemical in mainstream smoke and certain cigarette characteristics were observed. For example, charcoal filtration was associated with reduced vinyl chloride, and the concentration of sodium nitrate in the tobacco was positively correlated with the mainstream yield of both 2-naphthylamine and 4-aminobiphenyl. Benzene yield in mainstream cigarette smoke was correlated with the amount of tobacco burned and with the 'tar' level. Agronomic factors such as production practices and soil characteristics, and environmental conditions such as rainfall, reportedly influence the accumulation of metals, for example, cadmium, beryllium, chromium, nickel and arsenic, in the leaf. The use of fertilizers low in

  14. Meeting Report: Summary of IARC Monographs on Formaldehyde, 2-Butoxyethanol, and 1-tert-Butoxy-2-Propanol

    PubMed Central

    Cogliano, Vincent James; Grosse, Yann; Baan, Robert A.; Straif, Kurt; Secretan, Marie Béatrice; Ghissassi, Fatiha El

    2005-01-01

    An international, interdisciplinary working group of expert scientists met in June 2004 to develop IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans (IARC Monographs) on formaldehyde, 2-butoxyethanol, and 1-tert-butoxy-2-propanol. Each IARC Monograph includes a critical review of the pertinent scientific literature and an evaluation of an agent’s potential to cause cancer in humans. After a thorough discussion of the epidemiologic, experimental, and other relevant data, the working group concluded that formaldehyde is carcinogenic to humans, based on sufficient evidence in humans and in experimental animals. In the epidemiologic studies, there was sufficient evidence that formaldehyde causes nasopharyngeal cancer, “strong but not sufficient” evidence of leukemia, and limited evidence of sinonasal cancer. The working group also concluded that 2-butoxyethanol and 1-tert-butoxy-2-propanol are not classifiable as to their carcinogenicity to humans, each having limited evidence in experimental animals and inadequate evidence in humans. These three evaluations and the supporting data will be-published as Volume 88 of the IARC Monographs. PMID:16140628

  15. Considerations of circadian impact for defining 'shift work' in cancer studies: IARC Working Group Report.

    PubMed

    Stevens, Richard G; Hansen, Johnni; Costa, Giovanni; Haus, Erhard; Kauppinen, Timo; Aronson, Kristan J; Castaño-Vinyals, Gemma; Davis, Scott; Frings-Dresen, Monique H W; Fritschi, Lin; Kogevinas, Manolis; Kogi, Kazutaka; Lie, Jenny-Anne; Lowden, Arne; Peplonska, Beata; Pesch, Beate; Pukkala, Eero; Schernhammer, Eva; Travis, Ruth C; Vermeulen, Roel; Zheng, Tongzhang; Cogliano, Vincent; Straif, Kurt

    2011-02-01

    Based on the idea that electric light at night might account for a portion of the high and rising risk of breast cancer worldwide, it was predicted long ago that women working a non-day shift would be at higher risk compared with day-working women. This hypothesis has been extended more recently to prostate cancer. On the basis of limited human evidence and sufficient evidence in experimental animals, in 2007 the International Agency for Research on Cancer (IARC) classified 'shift work that involves circadian disruption' as a probable human carcinogen, group 2A. A limitation of the epidemiological studies carried out to date is in the definition of 'shift work.' IARC convened a workshop in April 2009 to consider how 'shift work' should be assessed and what domains of occupational history need to be quantified for more valid studies of shift work and cancer in the future. The working group identified several major domains of non-day shifts and shift schedules that should be captured in future studies: (1) shift system (start time of shift, number of hours per day, rotating or permanent, speed and direction of a rotating system, regular or irregular); (2) years on a particular non-day shift schedule (and cumulative exposure to the shift system over the subject's working life); and (3) shift intensity (time off between successive work days on the shift schedule). The group also recognised that for further domains to be identified, more research needs to be conducted on the impact of various shift schedules and routines on physiological and circadian rhythms of workers in real-world environments.

  16. Integration host factor (IHF) applied for partial digestion by restriction endonucleases in large DNA molecules (IARC procedure).

    PubMed

    Kur, J

    1993-01-01

    The IHF protein of Escherichia coli was successfully used in IHF-mediated Achilles' Heel Cleavage (IHF-AC) technique (Koob et al., 1988; Kur et al., 1992), and leads to the generation of very rare restriction sites in large DNA molecules. The first step of this procedure is methylation of DNA in the presence of IHF, when the overlapping ihf/restriction sites are protected from methylation, and in the second step the DNA is cut by the cognate restriction enzyme. The aim of the present study is to develop a very exact and reproducible procedure to obtain only a few well-defined cuts with the IHF-pre-treated DNA, depending on the variety of all parameters. This technique (IARC, i.e., IHF-assisted rare cutters) employs the restriction enzyme and only one auxiliary protein (IHF). The advantage of the IARC procedure is that no methylation is required (as opposed to the IHF-AC method). Using the IARC approach, the effects of various IHF concentrations were evaluated on cleaving the activity of the DraI, PacI, PmeI, and SwaI enzymes using DNA of phage lambda or the entire genomic 4.7-Mb DNA of E. coli. At low IHF concentrations only a few cut sites were eliminated by IHF binding, but at high IHF concentration, enzymes were able to cut in only one or several specific sites.

  17. 40 CFR 246.203 - Reevaluation.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Reevaluation. 246.203 Section 246.203 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES SOURCE SEPARATION FOR MATERIALS RECOVERY GUIDELINES Requirements and Recommended Procedures § 246.203 Reevaluation....

  18. 34 CFR 300.303 - Reevaluations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... DISABILITIES Evaluations, Eligibility Determinations, Individualized Education Programs, and Educational Placements Evaluations and Reevaluations § 300.303 Reevaluations. (a) General. A public agency must ensure... 300.311— (1) If the public agency determines that the educational or related services needs,...

  19. 34 CFR 300.303 - Reevaluations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... DISABILITIES Evaluations, Eligibility Determinations, Individualized Education Programs, and Educational Placements Evaluations and Reevaluations § 300.303 Reevaluations. (a) General. A public agency must ensure... 300.311— (1) If the public agency determines that the educational or related services needs,...

  20. Multifactorial aetiology of lung cancer among silica-exposed workers.

    PubMed

    Cocco, P

    2001-09-01

    In 1997, the International Agency for Research on Cancer (IARC) upgraded its evaluation of crystalline silica to a Group 1 human carcinogen. Criticism against such decision is based on the lack of consistency in experimental results across animal species, violation of an important principle for causality, such as the replication of findings under different circumstances of exposure, and the lack of a clear dose-response curve. The most recent epidemiological literature on the silica-silicosis-lung cancer link replicates the inconsistent findings that have been characterising 50 years of scientific debate in the occupational arena. Exposure circumstances capable of modifying the silica-lung cancer association include chronic bronchitis, composition of the dust mixing, particularly concerning co-occurrence of other known or probable lung carcinogens, total respirable dust, concentration of silica in respirable dust, type of crystalline silica and particle surface characteristics. The hypothesis of a silicosis-mediated pathway points toward an unspecific mechanism shared with other fibrotic conditions, for which silica might be just one of the triggers. In envisaging a multivariate multistep model of lung cancer among silica-exposed workers, silica might be considered as a "passive components of the sufficient cause", i.e., one of the associated risk factors, concurrent or subsequent to the "active component(s) of the sufficient cause" (including, for instance, smoking, asbestos, radon-daughters, arsenic, hexavalent chromium, nickel, polycyclic aromatic hydrocarbons (PAH), and diesel exhausts among the external risk factors; and DNA repair enzymes polymorphism and spontaneous inactivation of tumour suppressor genes among the internal risk factors), which adds up in modulating the tumoral development in not easily predictable directions. If silica acts as a human lung carcinogen depending on certain occupational exposure circumstances, perhaps those circumstances and

  1. Crystalline silica and lung cancer: a critical review of the occupational epidemiology literature of exposure-response studies testing this hypothesis.

    PubMed

    Gamble, John F

    2011-05-01

    IARC (2009; Metals, Particles and Fibres. IARC Monographs on the Evaluaton of Carcinogenic Risks to Humans. Volume 100C. Lyon, France: IARC) concluded that crystalline silica in occupational settings is a lung carcinogen. This conclusion is based primarily on studies with exposure-response (E-R) analyses and a pooled analysis of 10 major studies with about 1000 lung cancer cases. The purpose of this review is to critically assess this cancer classification based on E-R analyses in 18 studies from eight countries with about 2000 lung cancer cases and the same database used by IARC (2009) . The most appropriate exposure-response analysis is selected from latest study with least effect from bias, confounding, and presented graphically to assist individual assessment of the weight of evidence. Strength of association is consistently weak in the majority of studies. At the highest exposure level the mean relative risk (RR) is 1.5; four studies have strong associations (RRs > 2), three have moderate strong associations (RRs 1.5-2.0), six have weak-negligible associations (RRs 1-1.5), and five have no associations (RRs ≤1.0). Biological gradients were an inconsistent finding. Three studies had clear positive E-R trends; 3 had suggestive trends; and 12 had no E-R trends, 9 of which were flat or negative. There was a negative ER slope using RRs at the highest exposure of each study. Consistent findings of weak associations and lack of E-R trends does not support a causal association. Weight of evidence from occupational epidemiology does not support a causal association of lung cancer and silica exposure, which is contrary to the IARC conclusion using essentially the same data.

  2. IARC monographs, industry influence, and upgrading, downgrading, and under-grading chemicals: a personal point of view. International Agency for Research on Cancer.

    PubMed

    Huff, James

    2002-01-01

    The first IARC Monographs Volume was distributed in 1972, and over the 23 years through 1993, under the leadership of Dr Lorenzo Tomatis, 59 IARC Monographs were completed. During 1977-1979 the author was privileged to lead the program for Volumes 15-22, and participated in the pioneering development of the LARC Preamble and Categories of Evidence. During this era other Chiefs of the IARC Monographs included Claus Agthe, Harri Vainio, Antero Aitio, and Julian Wilbourn. Since then (starting with Volume 62: 1995), a new attitude seems to have pervaded the IARC Monographs program, resulting in an increasing influence of or partiality for industry and a diminishing dedication to public and occupational health and safety concerns, and for primary prevention. Some of this attitude comes from an apparent misguided scientific zest prematurely to endorse purported or hypothetical mechanisms of chemical carcinogenesis or modes of action of chemicals causing cancer in experimental animals. These speculations are in turn used cavalierly to discount the value of experimental evidence for predicting probable carcinogenicity to humans. Most often this is accomplished by opining that the mechanism(s) of carcinogenicity in animals would not be operative in humans. End of explanation. Examples whereby the IARC has recently "down-graded" or "under-graded" the available evidence of carcinogenicity include: acrylonitrile; atrazine; benzidine-based dyes; 1,3-butadiene, dichloromethane (methylene chloride); di (2-ethylhexyl) phthalate; glass wool insulation; MtBE [methyl tertiary butyl ether]; ochratoxin A; saccharin; sunlamps and sunbeds (use of); trichloroethylene; sulfamethazine; and others more inclusively mentioned in the text and tables. Further impeding or compromising public health, chemicals causing site-specific cancers in animals attendant with calculi/precipitate in the urinary bladder, goiter and thyroid gland, kidney and alpha-2mu globulin, peroxisome proliferation and

  3. The International Agency for Research on Cancer (IARC) evaluation of the carcinogenicity of outdoor air pollution: focus on China

    PubMed Central

    Loomis, Dana; Huang, Wei; Chen, Guosheng

    2014-01-01

    The International Agency for Research on Cancer (IARC) has classified outdoor air pollution and the particulate matter (PM) in outdoor air pollution as carcinogenic to humans, as based on sufficient evidence of carcinogenicity in humans and experimental animals and strong support by mechanistic studies. The data with important contributions to the evaluation are reviewed, highlighting the data with particular relevance to China, and implications of the evaluation with respect to China are discussed. The air pollution levels in Chinese cities are among the highest observed in the world today and frequently exceed health-based national and international guidelines. Data from high-quality epidemiologic studies in Asia, Europe, and North America consistently show positive associations between lung cancer and PM exposure and other indicators of air pollution, which persist after adjustment for important lung cancer risk factors, such as tobacco smoking. Epidemiologic data from China are limited but nevertheless indicate an increased risk of lung cancer associated with several air pollutants. Excess cancer risk is also observed in experimental animals exposed to polluted outdoor air or extracted PM. The exposure of several species to outdoor air pollution is associated with markers of genetic damage that have been linked to increased cancer risk in humans. Numerous studies from China, especially genetic biomarker studies in exposed populations, support that the polluted air in China is genotoxic and carcinogenic to humans. The evaluation by IARC indicates both the need for further research into the cancer risks associated with exposure to air pollution in China and the urgent need to act to reduce exposure to the population. PMID:24694836

  4. The International Agency for Research on Cancer (IARC) evaluation of the carcinogenicity of outdoor air pollution: focus on China.

    PubMed

    Loomis, Dana; Huang, Wei; Chen, Guosheng

    2014-04-01

    The International Agency for Research on Cancer (IARC) has classified outdoor air pollution and the particulate matter (PM) in outdoor air pollution as carcinogenic to humans, as based on sufficient evidence of carcinogenicity in humans and experimental animals and strong support by mechanistic studies. The data with important contributions to the evaluation are reviewed, highlighting the data with particular relevance to China, and implications of the evaluation with respect to China are discussed. The air pollution levels in Chinese cities are among the highest observed in the world today and frequently exceed health-based national and international guidelines. Data from high-quality epidemiologic studies in Asia, Europe, and North America consistently show positive associations between lung cancer and PM exposure and other indicators of air pollution, which persist after adjustment for important lung cancer risk factors, such as tobacco smoking. Epidemiologic data from China are limited but nevertheless indicate an increased risk of lung cancer associated with several air pollutants. Excess cancer risk is also observed in experimental animals exposed to polluted outdoor air or extracted PM. The exposure of several species to outdoor air pollution is associated with markers of genetic damage that have been linked to increased cancer risk in humans. Numerous studies from China, especially genetic biomarker studies in exposed populations, support that the polluted air in China is genotoxic and carcinogenic to humans. The evaluation by IARC indicates both the need for further research into the cancer risks associated with exposure to air pollution in China and the urgent need to act to reduce exposure to the population.

  5. IARC Database of p53 gene mutations in human tumors and cell lines: updated compilation, revised formats and new visualisation tools.

    PubMed Central

    Hainaut, P; Hernandez, T; Robinson, A; Rodriguez-Tome, P; Flores, T; Hollstein, M; Harris, C C; Montesano, R

    1998-01-01

    Since 1989, about 570 different p53 mutations have been identified in more than 8000 human cancers. A database of these mutations was initiated by M. Hollstein and C. C. Harris in 1990. This database originally consisted of a list of somatic point mutations in the p 53 gene of human tumors and cell lines, compiled from the published literature and made available in a standard electronic form. The database is maintained at the International Agency for Research on Cancer (IARC) and updated versions are released twice a year (January and July). The current version (July 1997) contains records on 6800 published mutations and will surpass the 8000 mark in the January 1998 release. The database now contains information on somatic and germline mutations in a new format to facilitate data retrieval. In addition, new tools are constructed to improve data analysis, such as a Mutation Viewer Java applet developed at the European Bioinformatics Institute (EBI) to visualise the location and impact of mutations on p53 protein structure. The database is available in different electronic formats at IARC (http://www.iarc. fr/p53/homepage.htm ) or from the EBI server (http://www.ebi.ac.uk ). The IARC p53 website also provides reports on database analysis and links with other p53 sites as well as with related databases. In this report, we describe the criteria for inclusion of data, the revised format and the new visualisation tools. We also briefly discuss the relevance of p 53 mutations to clinical and biological questions. PMID:9399837

  6. The Need to Reevaluate Nonresponding Ergonomic Patients

    NASA Technical Reports Server (NTRS)

    Scarpa, Philip J.; Field, Steven A.

    1999-01-01

    The Kennedy Space Center (KSC) Environmental Health (EH) contractor performs ergonomic evaluations under its Ergonomic Program. Any KSC employee may request one or the reviewing physician may request one for a patient during a visit to an onsite medical facility. As part of the ergonomic evaluation, recommendations are given to the patient to help reduce any ergonomic problems they experience. The recommendations, if implemented, are successful in the majority of KSC patients; however, a group of patients do not seem to improve. Those who don't improve may be identified by reevaluations, which are performed to implement maximum resolution of ergonomic problems.

  7. 40 CFR 51.153 - Reevaluation of episode plans.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Prevention of Air Pollution Emergency Episodes § 51.153 Reevaluation of episode plans. (a) States should periodically...

  8. 40 CFR 51.153 - Reevaluation of episode plans.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Prevention of Air Pollution Emergency Episodes § 51.153 Reevaluation of episode plans. (a) States should periodically...

  9. 40 CFR 51.153 - Reevaluation of episode plans.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Prevention of Air Pollution Emergency Episodes § 51.153 Reevaluation of episode plans. (a) States should periodically...

  10. 40 CFR 51.153 - Reevaluation of episode plans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Prevention of Air Pollution Emergency Episodes § 51.153 Reevaluation of episode plans. (a) States should periodically...

  11. 40 CFR 51.153 - Reevaluation of episode plans.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF IMPLEMENTATION PLANS Prevention of Air Pollution Emergency Episodes § 51.153 Reevaluation of episode plans. (a) States should periodically...

  12. Site characterization plan thermal goals reevaluation

    SciTech Connect

    Saterlie, S.F.; Garza, J.C. de la

    1994-12-31

    Because performance standards are not established for the Yucca Mountain Site (the Environmental Protection Agency (EPA) standards have been remanded), it is necessary to define surrogate or derived criteria to evaluate performance. The Site Characterization Plan (SCP) in 1988 attempted to define surrogate criteria that could be used to establish repository performance. Since that time, new knowledge has become available and some additional analyses of thermal loading have been performed. Thus it became clear that the thermal goals established in the SCP should be reevaluated. This paper reports on a two month effort undertaken to reevaluate the SCP thermal goals using an expert Working Group. Fifteen thermal goals identified in various sections of the SCP were evaluated by the Working Group. It was recommended that two goals be deleted: (1) to keep borehole wall temperature < 275 degrees C and keep the mid-drift temperature < 100 degrees C. It was also recommended that one goal be added to establish a thermal loading that would not degrade the Upper Paintbrush Tuff Formation (Lowermost Tiva Canyon; Yucca Mountain; Pah Canyon; and Uppermost Topopah Spring Members) (Vitric nonwelded) (PTn) barrier. Two other thermal goals and a process statement were reworded to afford compatibility with any emplacement mode, not just the vertical borehole. A recommendation was made to increase the conservatism of a goal to limit potential impact on the surface environment by limiting temperature rise to < 2 degrees C rather than < 6 degrees C. This revised set of goals was used in the Thermal Loading Systems Study.

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

    PubMed

    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

  14. Silica reusable surface insulation

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Smith, M.; Leiser, D. B. (Inventor)

    1976-01-01

    A reusable silica surface insulation material is provided by bonding amorphous silica fibers with colloidal silica at an elevated temperature. The surface insulation is ordinarily manufactured in the form of blocks (i.e., tiles).

  15. 14 CFR 161.403 - Criteria for reevaluation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Criteria for reevaluation. 161.403 Section 161.403 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED... change in the noise environment of the affected airport and that a review and reevaluation pursuant...

  16. 23 CFR 771.129 - Re-evaluations.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 23 Highways 1 2012-04-01 2012-04-01 false Re-evaluations. 771.129 Section 771.129 Highways FEDERAL... RELATED PROCEDURES § 771.129 Re-evaluations. (a) A written evaluation of the draft EIS shall be prepared... this evaluation is to determine whether or not a supplement to the draft EIS or a new draft EIS...

  17. The personal myth: a re-evaluation.

    PubMed

    Sirois, François

    2014-04-01

    This paper presents a re-evaluation of Kris's personal myth. The notion has been used rather sparingly despite the Delphi Symposium in 1984 on the question of its clinical usefulness. After framing the notion of myth, some difficulties related to the question are identified. A clinical vignette exemplifies some of the ambiguities in its definition but stresses its clinical relevance. A discussion expands on these situations so as to propose three various aspects of personal myths to account for the two variants identified by Kris. The actualization of the underlying fantasy in the character organization is a third form and the technical aspect associated with it is reviewed from a new perspective. The family romance is revisited to reassess its role as the basis of the personal myth in the face of studies favouring an earlier development of the myth. PMID:24580376

  18. Site characterization plan thermal goals reevaluation

    SciTech Connect

    1993-09-08

    The Site Characterization Plan (SCP) (DOE, 1988) attempted to define surrogate criteria that could be used to establish potential repository performance. These criteria or SCP thermal goals were developed from knowledge existing at the time and, as a reference case, emphasized performance for waste emplacement in a vertical borehole. Since that time, new knowledge has become available and some additional analyses of thermal loading have been performed. Additionally, other emplacement modes such as in-drift emplacement are being considered to accommodate larger waste packages. New concepts such as ``extended hot`` are also being considered as possible methods to achieve improved waste isolation. Thus it became clear that the thermal goals established in the SCP should be reevaluated. A Working Group was formed to reassess the SCP thermal goals to determine whether each goal was still valid, if there were goals that needed to be added, and what if any effort was needed to reduce the uncertainty associated with a particular goal. The objectives of the effort were to: (1) provide thermal goals that would support the FY 1993 Thermal Loading Systems Study; (2) help focus the planned testing and analysis efforts; and (3) acquire data that potentially could be used to initiate a change to the project technical baseline. Sixteen thermal goals were evaluated; fifteen were from various sections of the SCP; one goal was added, and another was split into two to include in-drift emplacement. The group`s findings and recommendations are presented.

  19. Reevaluation of compressible-flow Preston tube calibrations

    NASA Technical Reports Server (NTRS)

    Allen, J. M.

    1977-01-01

    Revised zero-pressure-gradient, adiabatic wall skin-friction-balance data covering a Mach number range from 1.6 to 4.6 led to a reevaluation of existing compressible flow Preston tube calibration equations.

  20. Reevaluation of erythropoietin production by the nephron.

    PubMed

    Nagai, Takanori; Yasuoka, Yukiko; Izumi, Yuichiro; Horikawa, Kahori; Kimura, Miho; Nakayama, Yushi; Uematsu, Takayuki; Fukuyama, Takashi; Yamazaki, Taiga; Kohda, Yukimasa; Hasuike, Yukiko; Nanami, Masayoshi; Kuragano, Takahiro; Kobayashi, Noritada; Obinata, Masuo; Tomita, Kimio; Tanoue, Akito; Nakanishi, Takeshi; Kawahara, Katsumasa; Nonoguchi, Hiroshi

    2014-06-27

    Erythropoietin production has been reported to occur in the peritubular interstitial fibroblasts in the kidney. Since the erythropoietin production in the nephron is controversial, we reevaluated the erythropoietin production in the kidney. We examined mRNA expressions of erythropoietin and HIF PHD2 using high-sensitive in situ hybridization system (ISH) and protein expression of HIF PHD2 using immunohistochemistry in the kidney. We further investigated the mechanism of erythropoietin production by hypoxia in vitro using human liver hepatocell (HepG2) and rat intercalated cell line (IN-IC cells). ISH in mice showed mRNA expression of erythropoietin in proximal convoluted tubules (PCTs), distal convoluted tubules (DCTs) and cortical collecting ducts (CCDs) but not in the peritubular cells under normal conditions. Hypoxia induced mRNA expression of erythropoietin largely in peritubular cells and slightly in PCTs, DCTs, and CCDs. Double staining with AQP3 or AE1 indicated that erythropoietin mRNA expresses mainly in β-intercalated or non α/non β-intercalated cells of the collecting ducts. Immunohistochemistry in rat showed the expression of HIF PHD2 in the collecting ducts and peritubular cells and its increase by anemia in peritubular cells. In IN-IC cells, hypoxia increased mRNA expression of erythropoietin, erythropoietin concentration in the medium and protein expression of HIF PHD2. These data suggest that erythropoietin is produced by the cortical nephrons mainly in the intercalated cells, but not in the peritubular cells, in normal hematopoietic condition and by mainly peritubular cells in hypoxia, suggesting the different regulation mechanism between the nephrons and peritubular cells.

  1. Reevaluation of erythropoietin production by the nephron.

    PubMed

    Nagai, Takanori; Yasuoka, Yukiko; Izumi, Yuichiro; Horikawa, Kahori; Kimura, Miho; Nakayama, Yushi; Uematsu, Takayuki; Fukuyama, Takashi; Yamazaki, Taiga; Kohda, Yukimasa; Hasuike, Yukiko; Nanami, Masayoshi; Kuragano, Takahiro; Kobayashi, Noritada; Obinata, Masuo; Tomita, Kimio; Tanoue, Akito; Nakanishi, Takeshi; Kawahara, Katsumasa; Nonoguchi, Hiroshi

    2014-06-27

    Erythropoietin production has been reported to occur in the peritubular interstitial fibroblasts in the kidney. Since the erythropoietin production in the nephron is controversial, we reevaluated the erythropoietin production in the kidney. We examined mRNA expressions of erythropoietin and HIF PHD2 using high-sensitive in situ hybridization system (ISH) and protein expression of HIF PHD2 using immunohistochemistry in the kidney. We further investigated the mechanism of erythropoietin production by hypoxia in vitro using human liver hepatocell (HepG2) and rat intercalated cell line (IN-IC cells). ISH in mice showed mRNA expression of erythropoietin in proximal convoluted tubules (PCTs), distal convoluted tubules (DCTs) and cortical collecting ducts (CCDs) but not in the peritubular cells under normal conditions. Hypoxia induced mRNA expression of erythropoietin largely in peritubular cells and slightly in PCTs, DCTs, and CCDs. Double staining with AQP3 or AE1 indicated that erythropoietin mRNA expresses mainly in β-intercalated or non α/non β-intercalated cells of the collecting ducts. Immunohistochemistry in rat showed the expression of HIF PHD2 in the collecting ducts and peritubular cells and its increase by anemia in peritubular cells. In IN-IC cells, hypoxia increased mRNA expression of erythropoietin, erythropoietin concentration in the medium and protein expression of HIF PHD2. These data suggest that erythropoietin is produced by the cortical nephrons mainly in the intercalated cells, but not in the peritubular cells, in normal hematopoietic condition and by mainly peritubular cells in hypoxia, suggesting the different regulation mechanism between the nephrons and peritubular cells. PMID:24832733

  2. Multifunctional mesoporous silica catalyst

    DOEpatents

    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. What Is Crystalline Silica?

    MedlinePlus

    ... silica, and requires a repirator protection program until engineering controls are implemented. Additionally, OSHA has a National ... silica materials with safer substitutes, whenever possible. ■ Provide engineering or administrative controls, where feasible, such as local ...

  4. Silica extraction from geothermal water

    DOEpatents

    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. FFTF (Fast Flux Test Facility) reactor shutdown system reliability reevaluation

    SciTech Connect

    Pierce, B.F.

    1986-07-01

    The reliability analysis of the Fast Flux Test Facility reactor shutdown system was reevaluated. Failure information based on five years of plant operating experience was used to verify original reliability numbers or to establish new ones. Also, system modifications made subsequent to performance of the original analysis were incorporated into the reevaluation. Reliability calculations and sensitivity analyses were performed using a commercially available spreadsheet on a personal computer. The spreadsheet was configured so that future failures could be tracked and compared with expected failures. A number of recommendations resulted from the reevaluation including both increased and decreased surveillance intervals. All recommendations were based on meeting or exceeding existing reliability goals. Considerable cost savings will be incurred upon implementation of the recommendations.

  6. Fusaproliferin production by Fusarium subglutinans and its toxicity to Artemia salina, SF-9 insect cells, and IARC/LCL 171 human B lymphocytes.

    PubMed Central

    Logrieco, A; Moretti, A; Fornelli, F; Fogliano, V; Ritieni, A; Caiaffa, M F; Randazzo, G; Bottalico, A; Macchia, L

    1996-01-01

    Fusarium subglutinans is an important pathogen of maize and other commodities worldwide. We examined MRC-115 and 71 other F. subglutinans strains from various geographic areas for their ability to synthesize fusaproliferin, a novel toxic sesterterpene recently isolated from F. proliferatum. Fusaproliferin production ranged from 30 to 1,500 micrograms/g of dried ground substrate, with 33 strains producing more than 500 micrograms/g. In particular, strain MRC-115 produced as much as 1,100 to 1,300 micrograms/g. In toxicity studies of two invertebrate models, fusaproliferin was toxic to Artemia salina (50% lethal dose, 53.4 microM) and to the lepidopteran cell line SF-9 (50% cytotoxic concentration, approximately 70 microM, after a 48-h exposure). Fusaproliferin was also toxic to the human nonneoplastic B-lymphocyte cell line IARC/LCL 171 (50% cytotoxic concentration, approximately 55 microM in culture in stationary phase after a 48-h exposure). Experiments performed will cells exposed at seeding suggested a possible cytostatic effect at subtoxic concentrations. PMID:8795229

  7. Silica-Ceria Hybrid Nanostructures

    SciTech Connect

    Munusamy, Prabhakaran; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Baer, Donald R.; Thevuthasan, Suntharampillai

    2012-04-25

    A new hybrid material system that consists of ceria attached silica nanoparticles has been developed. Because of the versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and versatile properties of silica and antioxidant properties of ceria nanoparticles, this material system is ideally suited for biomedical applications. The silica particles of size ~50nm were synthesized by the Stöber synthesis method and ceria nanoparticles of size ~2-3nm was attached to the silica surface using a hetrocoagulation method. The presence of silanol groups on the surface of silica particles mediated homogenous nucleation of ceria which were attached to silica surface by Si-O-Ce bonding. The formations of silica-ceria hybrid nanostructures were characterized by X-photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The HRTEM image confirms the formation of individual crystallites of ceria nanoparticles attached to the silica surface. The XPS analysis indicates that ceria nanoparticles are chemically bonded to surface of silica and possess mixture of +3 and +4 chemical states.

  8. Interactions of silica surfaces

    SciTech Connect

    Vigil, G.; Xu, Z.; Steinberg, S.; Israelachvili, J. . Dept. of Chemical and Nuclear Engineering and Materials Dept.)

    1994-07-01

    Adhesion, friction, and colloidal forces in air and aqueous salt solutions have been measured between various silica surfaces prepared by depositing amorphous but highly smooth silica films on mica. The results show four interesting and interrelated phenomena: (i) the adhesion of silica surfaces in air increases slowly with contact time, especially in humid air where the contacting surfaces become separated by an [approximately]20-[angstrom]-thick layer of hydrated silica or silica gel; (ii) the friction of two silica surfaces exhibits large sticking or stiction spikes, whose magnitude increases in the presence of water and when the surfaces are kept in contact longer before sliding; (iii) the non-DLVO repulsion commonly seen at short range (<40 A) between silica surfaces immersed in aqueous solutions is monotonically repulsive, with no oscillatory component, and is quite unlike theoretical expectations and previous measurements of forces due to solvent structure; (iv) dynamic contact angle measurements reveal time-dependent effects which cannot be due to a fixed surface chemical heterogeneity or roughness. The results indicate that silica surfaces undergo slow structural and chemical changes during interactions with water and with each other. More specifically, the authors propose that the unusual interfacial and colloidal properties of silica are due, not to hydration effects, but to the presence of an [approximately]10-[angstrom]-thick gel-like layer of protruding silanol and silicilic acid groups that grow on the surfaces in the presence of water. These protruding groups react chemically (sinter) with similar groups located on an opposing surface and give rise to the unusual time-dependent adhesion, friction, and non-DLVO forces observed. The proposed mechanism in terms of a surface layer of silica gel is consistent with the known surface chemistry of silica and accounts for the results reported and for other unusual surface and colloidal properties of silica.

  9. 75 FR 31834 - Adoption of Environmental Impact Statement; Availability of an Environmental Reevaluation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-04

    ... Impacts (64 FR 28545, May 26, 1999) require the reevaluation of a Final EIS if major steps toward... Federal Railroad Administration Adoption of Environmental Impact Statement; Availability of an Environmental Reevaluation AGENCY: Federal Railroad Administration (FRA), Department of Transportation...

  10. 12 CFR 226.59 - Reevaluation of rate increases.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 3 2011-01-01 2011-01-01 false Reevaluation of rate increases. 226.59 Section 226.59 Banks and Banking FEDERAL RESERVE SYSTEM (CONTINUED) BOARD OF GOVERNORS OF THE FEDERAL RESERVE SYSTEM TRUTH IN LENDING (REGULATION Z) Special Rules Applicable to Credit Card Accounts and Open-End Credit Offered to College Students §...

  11. 24 CFR 965.407 - Reevaluations of mastermeter systems.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 4 2010-04-01 2010-04-01 false Reevaluations of mastermeter systems. 965.407 Section 965.407 Housing and Urban Development Regulations Relating to Housing and Urban... URBAN DEVELOPMENT PHA-OWNED OR LEASED PROJECTS-GENERAL PROVISIONS Individual Metering of Utilities...

  12. 24 CFR 965.407 - Reevaluations of mastermeter systems.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 4 2011-04-01 2011-04-01 false Reevaluations of mastermeter systems. 965.407 Section 965.407 Housing and Urban Development REGULATIONS RELATING TO HOUSING AND URBAN... URBAN DEVELOPMENT PHA-OWNED OR LEASED PROJECTS-GENERAL PROVISIONS Individual Metering of Utilities...

  13. Silica, silicosis, and cancer

    SciTech Connect

    Goldsmith, D.F.; Winn, D.M.; Shy, C.M.

    1986-01-01

    These proceedings collect papers on occupational exposure. Topics include: measurement of silica dust, mortality in granite workers, effects of quartz in coal mine dust, pneumoconiosis, and lung cancer.

  14. 76 FR 42762 - Final Written Re-Evaluation for Environmental Impact Statement: Sikorsky Memorial Airport...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-19

    ... Federal Aviation Administration Final Written Re-Evaluation for Environmental Impact Statement: Sikorsky... Stratford, Connecticut. ADDRESSES: The Written Re-Evaluation document is available for review during normal... and other airfield improvements. This Written Re-Evaluation documents the FAA's assessment of...

  15. Men in nursing: re-evaluating masculinities, re-evaluating gender.

    PubMed

    Brown, Brian

    2009-10-01

    This paper critically interrogates and re-evaluates the notion that it is somehow difficult being a man in nursing and suggests some ways forward which will allow us to gain a more politically astute purchase on gender, nursing and the socio-political context in which the profession operates. Men appear to be well served by a career in nursing. Despite their lesser numbers they are likely to earn more and be promoted into leadership roles more readily. Yet there is a pervasive sense in the literature on men in nursing that they feel unhappy as a minority in a predominantly female occupation and feel a disjuncture between masculine identity and the nursing role. The genealogy of this idea can be traced to a more extensive literature in the 'men's movement', in sex role theory and masculinity studies which has tended to focus on the putative hurts that men suffer as they are socialized into the male role. This is itself informed by experiences and discourses from therapy, and privileges these kinds of experiences over and above more sober consideration of the respective powers of men and women and the sociopolitical context of the profession. This 'poor me' discourse deflects attention away from the business of tackling material inequalities and enables men to encroach further into the agenda of nursing discussions. Instead, a view of men and women in nursing is proposed which is attentive to the historical and political operations of power and which sees subjective experiences as the effects of power rather than as a starting point for analysis. We must place individual experience coherently and exhaustively in the material environment of social space and time. It is in this way that we can genuinely advance the interest of men and women and build an effective profile for the profession as a whole.

  16. Silica, Silicosis, and Autoimmunity

    PubMed Central

    Pollard, Kenneth Michael

    2016-01-01

    Inhalation of dust containing crystalline silica is associated with a number of acute and chronic diseases including systemic autoimmune diseases. Evidence for the link with autoimmune disease comes from epidemiological studies linking occupational exposure to crystalline silica dust with the systemic autoimmune diseases systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. Although little is known regarding the mechanism by which silica exposure leads to systemic autoimmune disease, there is a voluminous literature on silica exposure and silicosis that may help identify immune processes that precede development of autoimmunity. The pathophysiology of silicosis consists of deposition of silica particles in the alveoli of the lung. Ingestion of these particles by macrophages initiates an inflammatory response, which stimulates fibroblasts to proliferate and produce collagen. Silica particles are encased by collagen leading to fibrosis and the nodular lesions characteristic of the disease. The steps in the development of silicosis, including acute and chronic inflammation and fibrosis, have different molecular and cellular requirements, suggesting that silica-induced inflammation and fibrosis may be mechanistically separate. Significantly, it is unclear whether silica-induced inflammation and fibrosis contribute similarly to the development of autoimmunity. Nonetheless, the findings from human and animal model studies are consistent with an autoimmune pathogenesis that begins with activation of the innate immune system leading to proinflammatory cytokine production, pulmonary inflammation leading to activation of adaptive immunity, breaking of tolerance, and autoantibodies and tissue damage. The variable frequency of these immunological features following silica exposure suggests substantial genetic involvement and gene/environment interaction in silica-induced autoimmunity. However, numerous questions remain unanswered. PMID:27014276

  17. Chesapeake Bay basinwide toxics reduction strategy reevaluation report

    SciTech Connect

    Not Available

    1994-09-01

    The 1987 Chesapeake Bay Agreement committed the signatories to 'develop, adopt and begin implementation of a basinwide strategy to achieve a reduction of toxics, consistent with the Clean Water Act of 1987, which will ensure protection of human health and living resources.' The resultant Chesapeake Bay Basinwide Toxics Reduction Strategy, adopted by the Chesapeake Executive Council in January 1989, initiated a multi-jurisdictional effort to define the nature, extent, and magnitude of Chesapeake Bay toxics problems more accurately and initiate specific toxics reduction and prevention actions. The Chesapeake Bay Agreement signatories also committed to reevaluate the strategy during 1992. The objectives of this strategy reevaluation were to define: what we now know about the nature, extent, and magnitude of Bay toxics problems; what steps should be taken to reduce and prevent impacts from chemical contaminants; and what information is still needed to determine future actions. The Chesapeake Bay Program's Toxics Subcommittee investigated and evaluated the complex nature of the Bay's toxics problems through a two-year schedule of meetings, research workshops, and information-gathering forums. This report not only documents the findings of the two-year information gathering process of the strategy reevaluation but also recommends an approach for undertaking future toxics reduction and prevention actions in the Bay watershed.

  18. Silica Embedded Metal Hydrides

    SciTech Connect

    Heung, L.K.; Wicks, G.G.

    1998-08-01

    A method to produce silica embedded metal hydride was developed. The product is a composite in which metal hydride particles are embedded in a matrix of silica. The silica matrix is highly porous. Hydrogen gas can easily reach the embedded metal hydride particles. The pores are small so that the metal hydride particles cannot leave the matrix. The porous matrix also protects the metal hydride particles from larger and reactive molecules such as oxygen, since the larger gas molecules cannot pass through the small pores easily. Tests show that granules of this composite can absorb hydrogen readily and withstand many cycles without making fines.

  19. Electrochemical Sensors: Functionalized Silica

    SciTech Connect

    Fryxell, Glen E.; Lin, Yuehe; Yantasee, Wassana

    2009-03-24

    This chapter summarizes recent devellopment of electrochemical sensors based on functionlized mesoporous silica materials. The nanomatrials based sensors have been developed for sensitive and selective enrironmental detection of toxic heavy metal and uranium ions.

  20. Crystalline Silica Primer

    USGS Publications Warehouse

    ,

    1992-01-01

    substance and will present a nontechnical overview of the techniques used to measure crystalline silica. Because this primer is meant to be a starting point for anyone interested in learning more about crystalline silica, a list of selected readings and other resources is included. The detailed glossary, which defines many terms that are beyond the scope of this publication, is designed to help the reader move from this presentation to a more technical one, the inevitable next step.

  1. Silica, hybrid silica, hydride silica and non-silica stationary phases for liquid chromatography.

    PubMed

    Borges, Endler M

    2015-04-01

    Free silanols on the surface of silica are the "villains", which are responsible for detrimental interactions of those compounds and the stationary phase (i.e., bad peak shape, low efficiency) as well as low thermal and chemical stability. For these reasons, we began this review describing new silica and hybrid silica stationary phases, which have reduced and/or shielded silanols. At present, in liquid chromatography for the majority of analyses, reversed-phase liquid chromatography is the separation mode of choice. However, the needs for increased selectivity and increased retention of hydrophilic bases have substantially increased the interest in hydrophilic interaction chromatography (HILIC). Therefore, stationary phases and this mode of separation are discussed. Then, non-silica stationary phases (i.e., zirconium oxide, titanium oxide, alumina and porous graphitized carbon), which afford increased thermal and chemical stability and also selectivity different from those obtained with silica and hybrid silica, are discussed. In addition, the use of these materials in HILIC is also reviewed.

  2. Structural polarity in the Chara rhizoid: a reevaluation

    NASA Technical Reports Server (NTRS)

    Kiss, J. Z.; Staehelin, L. A.

    1993-01-01

    The Chara rhizoid is a useful model system to study gravitropism since all phases of gravitropism occur in a single cell. Despite years of study, a complete description of the distinctive ultrastructure of Chara rhizoids is not available. Therefore, in this paper, we reevaluate the ultrastructural features of vertically grown rhizoids, which have a structural polarity consisting of seven distinct zones. We also characterize the apical vesicles and the cell wall in these rhizoids by using antibodies against pectic polysaccharides. These studies demonstrate that the cell wall consists of two pectinaceous domains and that a distinct population of apical vesicles contain methyl esterified pectin.

  3. Low Specific Activity materials concepts are being reevaluated

    SciTech Connect

    Rawl, R.R.

    1993-10-01

    Many types of radioactive low-level waste are classified, packaged, and transported as Low-Specific Activity (LSA) material. The transportation regulations allow LSA materials to be shipped in economical packagings and, under certain conditions, waives compliance with other detailed requirements such as labeling. The fundamental concepts which support the LSA category are being thoroughly reevaluated to determine the defensibility of the provisions. A series of national and international events are leading to the development of new dose models which are likely to fundamentally change the ways these materials are defined. Similar basis changes are likely for the packaging requirements applicable to these materials.

  4. Kinetics of silica polymerization

    SciTech Connect

    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.

  5. 43 CFR 2804.15 - When does BLM reevaluate the processing and monitoring fees?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... go into effect and at 10-year intervals after that. When reevaluating processing and monitoring fees...) Technology; (b) The procedures for processing applications and monitoring grants; (c) Statutes...

  6. Silica in alkaline brines

    USGS Publications Warehouse

    Jones, B.F.; Rettig, S.L.; Eugster, H.P.

    1967-01-01

    Analysis of sodium carbonate-bicarbonate brines from closed basins in volcanic terranes of Oregon and Kenya reveals silica contents of up to 2700 parts per million at pH's higher than 10. These high concentrations of SiO 2 can be attributed to reaction of waters with silicates, and subsequent evaporative concentration accompanied by a rise in pH. Supersaturation with respect to amorphous silica may occur and persist for brines that are out of contact with silicate muds and undersaturated with respect to trona; correlation of SiO2 with concentration of Na and total CO2 support this interpretation. Addition of moredilute waters to alkaline brines may lower the pH and cause inorganic precipitation of substantial amounts of silica.

  7. Silica Precipitation and Lithium Sorption

    SciTech Connect

    Jay Renew

    2015-09-20

    This file contains silica precipitation and lithium sorption data from the project. The silica removal data is corrected from the previous submission. The previous submission did not take into account the limit of detection of the ICP-MS procedure.

  8. Epoxy Grout With Silica Thickener

    NASA Technical Reports Server (NTRS)

    Mcclung, C. E.

    1984-01-01

    Grout cures quickly, even in presence of hydraulic oil. Grout is mixture of aggregate particles, finely-divided silica, epoxy resin, and triethylenetetramine curing agent, with mixture containing about 85 percent silica and aggregate particle sand 15 percent resin and curing agent. Silica is thickening agent and keeps grout from sagging.

  9. 34 CFR 300.305 - Additional requirements for evaluations and reevaluations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... defined in § 300.8, and the educational needs of the child; or (B) In case of a reevaluation of a child, whether the child continues to have such a disability, and the educational needs of the child; (ii) The... child needs special education and related services; or (B) In the case of a reevaluation of a...

  10. 34 CFR 300.305 - Additional requirements for evaluations and reevaluations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... defined in § 300.8, and the educational needs of the child; or (B) In case of a reevaluation of a child, whether the child continues to have such a disability, and the educational needs of the child; (ii) The... child needs special education and related services; or (B) In the case of a reevaluation of a...

  11. 24 CFR 965.407 - Reevaluations of master-meter systems.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 24 Housing and Urban Development 4 2014-04-01 2014-04-01 false Reevaluations of master-meter systems. 965.407 Section 965.407 Housing and Urban Development REGULATIONS RELATING TO HOUSING AND URBAN... Existing PHA-Owned Projects § 965.407 Reevaluations of master-meter systems. Because of changes in the...

  12. [Study of post marketing safety reevaluation of shenqi fuzheng injection].

    PubMed

    Ai, Qing-Hua; Li, Yuan-Yuan; Xie, Yan-Ming

    2014-09-01

    In order to promote the Shenqifuzheng injection (SQFZ) clinical medication safety, this study reevaluate on SQFZ post marketing safety study systematically. Including multi center large sample registration type safety monitoring research, the analysis based on national spontaneous reporting system data, the analysis based on the 20 national hospital information system data and literature research. Above the analysis, it suggests that SQFZ has good security. The more adverse drug reaction (ADR) as allergic reactions, mainly involved in the damage of skin, appendages and its systemic damage, serious person can appear allergic shock. ADR/E is more common in the elderly, may be related to medication (tumor) populations. Early warning analysis based on SRS data and literature research are of the view that "phlebitis" has a strong association with SQFZ used. PMID:25532410

  13. [The conceptual re-evaluation of therapeutic success in schizophrenia].

    PubMed

    Kalman, Janos; Kalman, Sara

    2011-12-01

    The development of new therapeutic approaches is considered to be a major contributor to the re-evaluation of therapeutic outcomes in schizophrenia. The present review accentuates the recent dimensional concept of improvement, including the integration of social and clinical aspects of different treatment approaches together with the culture-specific pragmatic concept of the therapeutic success. The outpatient status of the patient in itself is no longer recognised as a final success of the therapy, if the very basic aspects of self-management and performance, education and employment of the schizophrenic patients are not properly resolved. Thus the symptomatic therapy alone, without the amelioration of social skills, can no longer be recognised as a satisfying therapeutic target. Novel sensitive possibilities of the measurement of functional improvement were recently introduced in order to facilitate both the development of a personalized, efficient treatment and the evaluation of therapeutic efficacy in schizophrenia.

  14. Reevaluation of conventional pituitary irradiation in the therapy of acromegaly.

    PubMed

    Jaffe, C A

    1999-06-01

    External beam pituitary irradiation has been frequently used in the treatment of growth hormone (GH) secreting pituitary adenomas. Many studies have demonstrated that serum GH declines rapidly and reliably following treatment and early "cure" rates, based on a basal serum GH below 10 micrograms/L were as high as 80%. The definition of "cure" has become more stringent over time and retrospective studies have indicated that GH must be below 2.5 micrograms/L for acromegalics to achieve mortality rates comparable to a normal population. Only 20% of irradiated patients will achieve this goal by 10 yr. Even fewer will achieve a normal serum insulin-like growth factor I (IGF-I) levels. Although pituitary irradiation still has a role in the control of tumor size, its importance as a treatment for normalizing serum GH is being reevaluated. PMID:11081173

  15. Mixture interpretation: Experimental and simulated reevaluation of qualitative analysis.

    PubMed

    Manabe, Sho; Mori, Yuki; Kawai, Chihiro; Ozeki, Munetaka; Tamaki, Keiji

    2013-03-01

    We present here analytical data using the 15 STR typing (Identifiler) kit regarding heterozygote balance in experimental DNA samples including one or two persons. Surprisingly, the allelic imbalance was observed even in samples consisting of only one person but adequate DNA for the standard protocol. The variance of heterozygote balance was more expanded in two-person mixtures than in one-person samples. Therefore, it is not suitable to use allelic peak heights/areas for estimating the genotypes of the contributors such as the quantitative analysis. We also reevaluated the effectiveness of qualitative analysis by simulation, i.e. consideration of the probability of all possible genotype combinations from the typing results of a mixed DNA sample. As demonstrated, the qualitative analysis using 15 STR loci is still extremely effective even in a mixture from two or three individuals.

  16. 77 FR 73114 - Draft Written Re-Evaluation for Environmental Impact Statement: T.F. Green Airport, Warwick, RI

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-07

    ... Federal Aviation Administration Draft Written Re-Evaluation for Environmental Impact Statement: T.F. Green... Draft Written Re-Evaluation for an Environmental Impact Statement (EIS) has been prepared for Theodore... to T.F. Green Draft Written Re-Evaluation'' in the subject line Mail: Richard Doucette,...

  17. 76 FR 44648 - Notice of Availability of a Record of Decision (ROD) and Order for a Written Reevaluation of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-26

    ... Written Reevaluation of Final Environmental Impact Statement (FEIS) for the Development and Expansion of... that it has issued a ROD and Order for a written reevaluation of the FEIS for the Development and... approved project disclosed in the written reevaluation and as shown on a revised Airport Layout Plan...

  18. Viscoelasticity of silica gels

    SciTech Connect

    Scherer, G.W.

    1995-12-01

    The response of silica gels to mechanical loads depends on the properties of the solid phase and the permeability of the network. Understanding this behavior is essential for modeling of stresses developed during drying or heating of gels. The permeability and the mechanical properties are readily determined from a simple beam-bending experiment, by measuring the load relaxation that occurs at constant deflection. Load decay results from movement of the liquid within the network; in addition, there may be viscoelastic relaxation of the network itself. Silica gel is viscoelastic in chemically aggressive media, but in inert liquids (such as ethanol or acetone) it is elastic. Experiments show that the viscoelastic relaxation time decreases as the concentration and pH of the water in the pore liquid increase. During drying, the permeability decreases and the viscosity increases, both exhibiting a power-law dependence on density of the gel network.

  19. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  20. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  1. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  2. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  3. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  4. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  5. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  6. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  7. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and... GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances § 182.1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of...

  8. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  9. The world ocean silica cycle.

    PubMed

    Tréguer, Paul J; De La Rocha, Christina L

    2013-01-01

    Over the past few decades, we have realized that the silica cycle is strongly intertwined with other major biogeochemical cycles, like those of carbon and nitrogen, and as such is intimately related to marine primary production, the efficiency of carbon export to the deep sea, and the inventory of carbon dioxide in the atmosphere. For nearly 20 years, the marine silica budget compiled by Tréguer et al. (1995) , with its exploration of reservoirs, processes, sources, and sinks in the silica cycle, has provided context and information fundamental to study of the silica cycle. Today, the budget needs revisiting to incorporate advances that have notably changed estimates of river and groundwater inputs to the ocean of dissolved silicon and easily dissolvable amorphous silica, inputs from the dissolution of terrestrial lithogenic silica in ocean margin sediments, reverse weathering removal fluxes, and outputs of biogenic silica (especially on ocean margins and in the form of nondiatomaceous biogenic silica). The resulting budget recognizes significantly higher input and output fluxes and notes that the recycling of silicon occurs mostly at the sediment-water interface and not during the sinking of silica particles through deep waters.

  10. Reevaluation of the trace element content in Reference Man

    NASA Astrophysics Data System (ADS)

    Iyengar, G. V.

    1998-06-01

    Using recent analytical data, the total body content of several trace elements for the 70 kg Reference Man has been reevaluated. The evaluation leads to the following conclusions. For Al, Ba, Cu and F, the present estimates show an increase; for Br, Cs, I, Pb and Zn the average values for the total body content derived from the present evaluation have remained close to the 1975 estimates; for As, Cd and Rb, the total contents have declined; for B, Co and Mn the uncertainty of the 1975 evaluations have been reduced; and for Au and Cr the 1997 estimations are far below the 1975 estimates. Provisional estimates for Ni (4-6.5 mg), Se (14-21 mg) and Si (2000-3000 mg) are proposed for the first time. With respect to dietary intakes, in contrast to the earlier estimates intakes of trace elements were found to be decreased by factors of 2 for Cu, 2-5 for Cr, 5-10 for Cd, Hg and Pb, and >10 for Ag, As, Co, Li, Sb and V.

  11. Computed tomography for staging esophageal and gastroesophageal cancer: reevaluation

    SciTech Connect

    Thompson, W.M.; Halvorsen, R.A.; Foster, W.L. Jr.; Williford, M.E.; Postlethwait, R.W.; Korobkin, M.

    1983-11-01

    A reevaluation of computed tomography (CT) for staging carcinoma of the esophagus and gastroesophageal junction was performed in 76 patients. For comparison 26 patients without carcinoma of the esophagus with a normal mediastinum at surgery were included in the evaluation. Four radiologists evaluated the CT scans without knowledge of the diagnosis. After determining if there was an adequate amount of fat, they were asked to evaluate each case for the presence or absence of local invasion and distant metastases. The radiologists correctly identified all 26 normal patients. Eighteen of the 76 carcinoma had a paucity of fat, but only six were thought to have truly indeterminate scans. CT correctly identified 40 of the 44 esophageal carcinoma patients with mediastinal invasion and 11 of the 15 patients without invasion (accuracy 88%). CT correctly identified 15 of 19 patients with distant abdominal metastases and 28 of 30 patients without metastases (accuracy 88%). CT was only 50% accurate in predicting the presence or absence of invasion in the 12 patients with gastroesophageal junction tumors and only 58% accurate in predicting distant metastases. CT correctly staged 46(94%) of 49 patients with esophageal carcinoma but only five (42%) of 12 patients with gastroesophageal junction tumors. These results confirm that CT should be used as a major staging method in all patients with esophageal carcinoma.

  12. Arsenic hydrogeochemistry in an irrigated river valley - A reevaluation

    USGS Publications Warehouse

    Nimick, D.A.

    1998-01-01

    Arsenic concentrations in ground water of the lower Madison River valley, Montana, are high (16 to 176 ??g/L). Previous studies hypothesized that arsenic-rich river water, applied as irrigation, was evapoconcentrated during recharge and contaminated the thin alluvial aquifer. Based on additional data collection and a reevaluation of the hydrology and geochemistry of the valley, the high arsenic concentrations in ground water are caused by a unique combination of natural hydrologic and geochemical factors, and irrigation appears to play a secondary role. The high arsenic concentrations in ground water have several causes: direct aquifer recharge by Madison River water having arsenic concentrations as high as 100 ??g/L, leaching of arsenic from Tertiary volcano-clastic sediment, and release of sorbed arsenic where redox conditions in ground water are reduced. The findings are consistent with related studies that demonstrate that arsenic is sorbed by irrigated soils in the valley. Although evaporation of applied irrigation water does not significantly increase arsenic concentrations in ground water, irrigation with arsenic-rich water raises other environmental concerns.

  13. Re-evaluation of monitored retrievable storage concepts

    SciTech Connect

    Fletcher, J.F.; Smith, R.I.

    1989-04-01

    In 1983, as a prelude to the monitored retrievable storage (MRS) facility conceptual design, the Pacific Northwest Laboratory (PNL) conducted an evaluation for the US Department of Energy (DOE) that examined alternative concepts for storing spent LWR fuel and high- level wastes from fuel reprocessing. The evaluation was made considering nine concepts for dry away-from-reactor storage. The nine concepts evaluated were: concrete storage cask, tunnel drywell, concrete cask-in-trench, open-cycle vault, metal casks (transportable and stationary), closed-cycle vault, field drywell, and tunnel-rack vault. The purpose and scope of the re-evaluation did not require a repetition of the expert-based examinations used earlier. Instead, it was based on more detailed technical review by a small group, focusing on changes that had occurred since the initial evaluation was made. Two additional storage concepts--the water pool and the horizontal modular storage vault (NUHOMS system)--were ranked along with the original nine. The original nine concepts and the added two conceptual designs were modified as appropriate for a scenario with storage capacity for 15,000 MTU of spent fuel. Costs, area requirements, and technical and historical data pertaining to MRS storage were updated for each concept.

  14. Reevaluation of a walleye (Sander vitreus) bioenergetics model

    USGS Publications Warehouse

    Madenjian, Charles P.; Wang, Chunfang

    2013-01-01

    Walleye (Sander vitreus) is an important sport fish throughout much of North America, and walleye populations support valuable commercial fisheries in certain lakes as well. Using a corrected algorithm for balancing the energy budget, we reevaluated the performance of the Wisconsin bioenergetics model for walleye in the laboratory. Walleyes were fed rainbow smelt (Osmerus mordax) in four laboratory tanks each day during a 126-day experiment. Feeding rates ranged from 1.4 to 1.7 % of walleye body weight per day. Based on a statistical comparison of bioenergetics model predictions of monthly consumption with observed monthly consumption, we concluded that the bioenergetics model estimated food consumption by walleye without any significant bias. Similarly, based on a statistical comparison of bioenergetics model predictions of weight at the end of the monthly test period with observed weight, we concluded that the bioenergetics model predicted walleye growth without any detectable bias. In addition, the bioenergetics model predictions of cumulative consumption over the 126-day experiment differed fromobserved cumulative consumption by less than 10 %. Although additional laboratory and field testing will be needed to fully evaluate model performance, based on our laboratory results, the Wisconsin bioenergetics model for walleye appears to be providing unbiased predictions of food consumption.

  15. Arsenic hydrogeochemistry in an irrigated river valley -- A reevaluation

    SciTech Connect

    Nimick, D.A.

    1998-09-01

    Arsenic concentrations in ground water of the lower Madison River valley, Montana, are high. Previous studies hypothesized that arsenic-rich river water, applied as irrigation, was evapoconcentrated during recharge and contaminated the thin alluvial aquifer. Based on additional data collection and a reevaluation of the hydrology and geochemistry of the valley, the high arsenic concentrations in ground water are caused by a unique combination of natural hydrologic and geochemical factors, and irrigation appears to play a secondary role. The high arsenic concentrations in ground water have several causes: direct aquifer recharge by Madison River water having arsenic concentrations as high as 100 {micro}g/L, leaching of arsenic from Tertiary volcano-clastic sediment, and release of sorbed arsenic where redox conditions in ground water are reduced. The findings are consistent with related studies that demonstrate that arsenic is sorbed by irrigated soils in the valley. Although evaporation of applied irrigation water does not significantly increase arsenic concentrations in ground water, irrigation with arsenic-rich water raises other environmental concerns.

  16. Reevaluation of lake trout and lake whitefish bioenergetics models

    USGS Publications Warehouse

    Madenjian, Charles P.; Pothoven, Steve A.; Kao, Yu-Chun

    2013-01-01

    Using a corrected algorithm for balancing the energy budget, we reevaluated the Wisconsin bioenergetics model for lake trout (Salvelinus namaycush) in the laboratory and for lake whitefish (Coregonus clupeaformis) in the laboratory and in the field. For lake trout, results showed that the bioenergetics model slightly overestimated food consumption by the lake trout when they were fed low and intermediate rations, whereas the model predicted food consumption by lake trout fed ad libitum without any detectable bias. The slight bias in model predictions for lake trout on restricted rations may have been an artifact of the feeding schedule for these fish, and we would therefore recommend application of the Wisconsin lake trout bioenergetics model to lake trout populations in the field without any revisions to the model. Use of the Wisconsin bioenergetics model for coregonids resulted in overestimation of food consumption by lake whitefish both in the laboratory and in the field by between 20 and 30%, on average. This overestimation of food consumption was most likely due to overestimation of respiration rate. We therefore adjusted the respiration component of the bioenergetics model to obtain a good fit to the observed consumption in our laboratory tanks. The adjusted model predicted the consumption in the laboratory and the field without any detectable bias. Until a detailed lake whitefish respiration study can be conducted, we recommend application of our adjusted version of the Wisconsin generalized coregonid bioenergetics model to lake whitefish populations in the field.

  17. Reevaluation of a Suspected Cronobacter sakazakii Outbreak in Mexico.

    PubMed

    Jackson, Emily E; Flores, Julio Parra; Fernández-Escartín, Eduardo; Forsythe, Stephen J

    2015-06-01

    In 2010, two infants became ill at a hospital in Mexico. Subsequently, a range of clinical, environmental, and powdered and rehydrated infant formula isolates were identified by using a combination of phenotyping and PCR probes. The strains were clustered according to pulsed-field gel electrophoresis. The causative agent was reported as Cronobacter sakazakii, with powdered infant formula (PIF) identified as the likely source of the infections. This new study further characterized the isolates from this outbreak by using multilocus sequence typing and whole genome sequencing of selected strains. Though four PIF isolates and one hospital environmental isolate were identified as C. sakazakii sequence type 297 by multilocus sequence typing, they were isolated 6 months prior to the outbreak. Genotypic analyses of patient isolates identified them as Enterobacter hormaechei and Enterobacter spp. The pulsed-field gel electrophoresis profile of the Enterobacter spp. isolates matched those of isolates from previously unopened tins of PIF. E. hormaechei was only isolated from the two infants and not PIF. The reevaluation of this outbreak highlights the need for accurate detection and identification assays, particularly during outbreak investigations in which incorrect identifications may mislead the investigation and attribution of the source. Though the species responsible for the symptoms could not be determined, this outbreak demonstrated the possible transmission of Enterobacter spp. from PIF to infants. These are possibly the first reported cases of Enterobacter spp. infection of infants from bacterial-contaminated PIF.

  18. 42 CFR 405.213 - Re-evaluation of a device categorization.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SERVICES MEDICARE PROGRAM FEDERAL HEALTH INSURANCE FOR THE AGED AND DISABLED Medical Services Coverage Decisions That Relate to Health Care Technology § 405.213 Re-evaluation of a device categorization....

  19. 42 CFR 405.213 - Re-evaluation of a device categorization.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... SERVICES MEDICARE PROGRAM FEDERAL HEALTH INSURANCE FOR THE AGED AND DISABLED Medical Services Coverage Decisions That Relate to Health Care Technology § 405.213 Re-evaluation of a device categorization....

  20. 42 CFR 405.213 - Re-evaluation of a device categorization.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... SERVICES MEDICARE PROGRAM FEDERAL HEALTH INSURANCE FOR THE AGED AND DISABLED Medical Services Coverage Decisions That Relate to Health Care Technology § 405.213 Re-evaluation of a device categorization....

  1. 42 CFR 405.213 - Re-evaluation of a device categorization.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... SERVICES MEDICARE PROGRAM FEDERAL HEALTH INSURANCE FOR THE AGED AND DISABLED Medical Services Coverage Decisions That Relate to Health Care Technology § 405.213 Re-evaluation of a device categorization....

  2. Five-Year NRHP Re-Evaluation of Historic Buildings Assessment

    SciTech Connect

    Ullrich, R A; Heidecker, K R

    2011-09-12

    The Lawrence Livermore National Laboratory (LLNL) 'Draft Programmatic Agreement among the Department of Energy and the California State Historic Preservation Officer Regarding Operation of Lawrence Livermore National Laboratory' requires a review and re-evaluation of the eligibility of laboratory properties for the National Register of Historic Places (NRHP) every five years. The original evaluation was published in 2005; this report serves as the first five-year re-evaluation. This re-evaluation includes consideration of changes within LLNL to management, to mission, and to the built environment. it also determines the status of those buildings, objects, and districts that were recommended as NRHP-eligible in the 2005 report. Buildings that were omitted from the earlier building list, those that have reached 50 years of age since the original assessment, and new buildings are also addressed in the re-evaluation.

  3. Silica Fillers for elastomer Reinforement

    SciTech Connect

    Kohls, D.J.; Schaefer, D.W.

    2012-09-10

    This article summarizes recent work on the structure of precipitated silica used in the reinforcement of elastomers. Silica has a unique morphology, consisting of multiple structural levels that can be controlled through processing. The ability to control and characterize the multiple structures of precipitated silica is an example of morphological engineering for reinforcement applications. In this summary of some recent research efforts using precipitated silica, small-angle scattering techniques are described and their usefulness for determining the morphology of silica in terms of primary particles, aggregates, and agglomerates are discussed. The structure of several different precipitated silica powders is shown as well as the mechanical properties of elastomers reinforced with these silica particles. The study of the mechanical properties of filled elastomer systems is a challenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward rule of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fillers like silica and carbon black on the reinforcement of elastomers. In general, the structure-property relationships developed for filled elastomers have evolved into the following major areas: Filler structure, hydrodynamic reinforcement, and interactions between fillers and elastomers.

  4. Interfacial engineering for silica nanocapsules.

    PubMed

    Wibowo, David; Hui, Yue; Middelberg, Anton P J; Zhao, Chun-Xia

    2016-10-01

    Silica nanocapsules have attracted significant interest due to their core-shell hierarchical structure. The core domain allows the encapsulation of various functional components such as drugs, fluorescent and magnetic nanoparticles for applications in drug delivery, imaging and sensing, and the silica shell with its unique properties including biocompatibility, chemical and physical stability, and surface-chemistry tailorability provides a protection layer for the encapsulated cargo. Therefore, significant effort has been directed to synthesize silica nanocapsules with engineered properties, including size, composition and surface functionality, for various applications. This review provides a comprehensive overview of emerging methods for the manufacture of silica nanocapsules, with a special emphasis on different interfacial engineering strategies. The review starts with an introduction of various manufacturing approaches of silica nanocapsules highlighting surface engineering of the core template nanomaterials (solid nanoparticles, liquid droplets, and gas bubbles) using chemicals or biomolecules which are able to direct nucleation and growth of silica at the boundary of two-phase interfaces (solid-liquid, liquid-liquid, and gas-liquid). Next, surface functionalization of silica nanocapsules is presented. Furthermore, strategies and challenges of encapsulating active molecules (pre-loading and post-loading approaches) in these capsular systems are critically discussed. Finally, applications of silica nanocapsules in controlled release, imaging, and theranostics are reviewed. PMID:27522646

  5. "Gray Areas": Silica gels, amorphous silica and cryptocrystalline silica on fault surfaces

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Kirkpatrick, J. D.; White, J. C.; Faber, C.; Caine, J. S.

    2012-12-01

    Silica gels, in the form of their solid-phase equivalents, are widely found in brittle fault zones and are commonly associated with mineral deposits. High- to moderate-velocity rotary friction experiments have produced silica gels on sliding surfaces coeval with dramatic slip weakening. In light of the latter, silica gel formation has been proposed as a potential mechanism of slip weakening during earthquakes in the shallow crust. However, low velocity sliding experiments have also produced significant amounts of amorphous material distributed throughout slipping layers, and dramatic weakening is not observed. Comparison of the products of laboratory experiments to geological examples is complicated by the diagenesis and lithification of silica gels. They may form hydrous and amorphous solids, hydrous crystalline solids, or dehydrate to quartz. In addition, the abundance and style of occurrence of these products in faults suggest that there are multiple origins for silica gels in faults. We review the mechanisms by which silica gels may form in fault zones and describe the solidification, crystallization and dehydration evolution of the silica. Analytical transmission electron microscope (TEM) observations of slip-surface silica deposits from the Corona Fault, San Francisco, the Dixie Valley Fault, Nevada, and the Olive Fault, Namibia typify the nano- to micro-structural evolution of the fault surface silica layers. We suggest criteria for identifying these materials in natural fault rocks. Some of these gels may form by comminution and hydrolization of silica-rich wall rocks, as has been observed in high-velocity experiments (Corona Fault). Others may form by depressurization and boiling of aqueous fluids, probably during fault valving (Olive Fault). Silica saturated hydrothermal fluids released during faulting may contribute in some cases (Dixie Valley Fault). Regardless of the mechanism of gel formation, the dramatic rheological weakening observed in friction

  6. Carbon in, Carbon out: Reevaluating Carbon Fluxes in Subduction Zones

    NASA Astrophysics Data System (ADS)

    Manning, C. E.; Kelemen, P. B.

    2015-12-01

    Subduction zones exert a fundamental control on the deep carbon cycle. We reevaluated carbon inputs and outputs in convergent margins considering new estimates of C concentration in subducting mantle peridotites, carbonate solubility in aqueous fluids along subduction geotherms, melting and diapirism of carbon-bearing metasediments, and diffuse degassing from arcs. Our updated estimate of carbon inputs to the global subduction system, which includes estimates for C in altered peridotite, is 40-66 megatons carbon/year (MtC/y). We find that estimates of C lost from slabs (14-66 MtC/y) must take into account the high CaCO3 solubility in aqueous fluids, which contributes significant C that must be added to that derived from mineral decarbonation reactions. When taken together with hydrous silicate and carbonatite melts and metasediment diapirs, nearly all C can be scavenged from subducting lithosphere. The return of C to the atmosphere via arc-volcano degassing is only 18-43 MtC/y, but consideration deep volatile saturation of arc magmas, magma ponding in the middle and deep arc crust, and CO2 venting in forearcs can account for the remaining C lost from the slab. Thus, whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, substantial quantities of carbon are stored in the mantle lithosphere and crust and the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing, at least over the last 5-10 My. This is consistent with inferences from noble gas data. Recycled carbon in diamonds is a small fraction of the global carbon inventory.

  7. Re-evaluating the treatment of acute optic neuritis

    PubMed Central

    Bennett, Jeffrey L; Nickerson, Molly; Costello, Fiona; Sergott, Robert C; Calkwood, Jonathan C; Galetta, Steven L; Balcer, Laura J; Markowitz, Clyde E; Vartanian, Timothy; Morrow, Mark; Moster, Mark L; Taylor, Andrew W; Pace, Thaddeus W W; Frohman, Teresa; Frohman, Elliot M

    2015-01-01

    Clinical case reports and prospective trials have demonstrated a reproducible benefit of hypothalamic-pituitary-adrenal (HPA) axis modulation on the rate of recovery from acute inflammatory central nervous system (CNS) demyelination. As a result, corticosteroid preparations and adrenocorticotrophic hormones are the current mainstays of therapy for the treatment of acute optic neuritis (AON) and acute demyelination in multiple sclerosis. Despite facilitating the pace of recovery, HPA axis modulation and corticosteroids have failed to demonstrate long-term benefit on functional recovery. After AON, patients frequently report visual problems, motion perception difficulties and abnormal depth perception despite ‘normal’ (20/20) vision. In light of this disparity, the efficacy of these and other therapies for acute demyelination require re-evaluation using modern, high-precision paraclinical tools capable of monitoring tissue injury. In no arena is this more amenable than AON, where a new array of tools in retinal imaging and electrophysiology has advanced our ability to measure the anatomic and functional consequences of optic nerve injury. As a result, AON provides a unique clinical model for evaluating the treatment response of the derivative elements of acute inflammatory CNS injury: demyelination, axonal injury and neuronal degeneration. In this article, we examine current thinking on the mechanisms of immune injury in AON, discuss novel technologies for the assessment of optic nerve structure and function, and assess current and future treatment modalities. The primary aim is to develop a framework for rigorously evaluating interventions in AON and to assess their ability to preserve tissue architecture, re-establish normal physiology and restore optimal neurological function. PMID:25355373

  8. Reevaluating the functional implications of Australopithecus afarensis navicular morphology.

    PubMed

    Prang, Thomas C

    2016-08-01

    The longitudinal arch is a unique characteristic of the human foot, yet the timing and pattern of its evolution remain controversial, in part due to the disagreement among researchers over which skeletal traits are the best indicators of its presence or absence. The small size of the human navicular tuberosity has previously been linked to the presence of a longitudinal arch, implying that the large tuberosity of early hominins such as Australopithecus afarensis reflects a flat foot. However, this hypothesis is at odds with other evidence of pedal form and function, such as metatarsal, tarsal, and footprint morphology, which show that a longitudinal arch was probably present in A. afarensis. This study reevaluates the morphometric affinities of the A. afarensis naviculars among other Plio-Pleistocene fossil hominins and anthropoid primates (N = 170). Multivariate cluster analyses show that all fossil hominin naviculars, including those attributed to A. afarensis, are most similar to modern humans. A measure of navicular tuberosity size quantified as the ratio of the tuberosity volume to the surface area of the talar facet shows that Ateles has the largest navicular tuberosity among the anthropoid sample and that there is no difference between highly arboreal and terrestrial taxa in this metric (e.g., Hylobates and Gorilla beringei). Instead, a relatively large navicular tuberosity may reflect the development of leg musculature associated with ankle plantarflexion. The functional inferences derived from the morphology of the A. afarensis naviculars are consistent with the morphology of the Laetoli footprints. PMID:27457546

  9. Silaffins in Silica Biomineralization and Biomimetic Silica Precipitation

    PubMed Central

    Lechner, Carolin C.; Becker, Christian F. W.

    2015-01-01

    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. PMID:26295401

  10. Silica/Polymer and Silica/Polymer/Fiber Composite Aerogels

    NASA Technical Reports Server (NTRS)

    Ou, Danny; Stepanian, Christopher J.; Hu, Xiangjun

    2010-01-01

    Aerogels that consist, variously, of neat silica/polymer alloys and silica/polymer alloy matrices reinforced with fibers have been developed as materials for flexible thermal-insulation blankets. In comparison with prior aerogel blankets, these aerogel blankets are more durable and less dusty. These blankets are also better able to resist and recover from compression . an important advantage in that maintenance of thickness is essential to maintenance of high thermal-insulation performance. These blankets are especially suitable as core materials for vacuum- insulated panels and vacuum-insulated boxes of advanced, nearly seamless design. (Inasmuch as heat leakage at seams is much greater than heat leakage elsewhere through such structures, advanced designs for high insulation performance should provide for minimization of the sizes and numbers of seams.) A silica/polymer aerogel of the present type could be characterized, somewhat more precisely, as consisting of multiply bonded, linear polymer reinforcements within a silica aerogel matrix. Thus far, several different polymethacrylates (PMAs) have been incorporated into aerogel networks to increase resistance to crushing and to improve other mechanical properties while minimally affecting thermal conductivity and density. The polymethacrylate phases are strongly linked into the silica aerogel networks in these materials. Unlike in other organic/inorganic blended aerogels, the inorganic and organic phases are chemically bonded to each other, by both covalent and hydrogen bonds. In the process for making a silica/polymer alloy aerogel, the covalent bonds are introduced by prepolymerization of the methacrylate monomer with trimethoxysilylpropylmethacrylate, which serves as a phase cross-linker in that it contains both organic and inorganic monomer functional groups and hence acts as a connector between the organic and inorganic phases. Hydrogen bonds are formed between the silanol groups of the inorganic phase and the

  11. Reevaluation of upper Jurassic Morrison Formation, Western Interior

    SciTech Connect

    Mantzios, C.

    1989-03-01

    Comparison of the Brushy Basin member of the Upper Jurassic Morrison Formation in the Colorado Plateau with the Upper Jurassic-Lower Cretaceous Morrison-Cloverly sequence in the Bighorn basin, Wyoming, shows great similarities in their depositional environments and stratigraphy. The lower Brushy Basin member is a fluvial deposit composed of channel sandstones and overbank mudstones which display a great number of pedogenic features. Similar depositional setting has been observed in the Morrison Formation in the Bighorn basin, Wyoming, where pedogenic features suggest a distal floodplain setting with low-sinuosity channels cutting through. In both localities the dominant clay mineral is illite. The upper Brushy Basin member in the Colorado Plateau is composed mostly of gray and purpose mudstones rich in montmorillonite. Devitrified tuff beds and bentonite occur in certain levels throughout the unit. Pedogenic features are not conspicuously developed. The Lower Cretaceous Clovery Formation in the Bighorn basin, Wyoming, is strikingly similar in terms of lithological aspects. The depositional environment is interpreted in both localities as a playa deposit. A great variety of nodules is present such as silcretes, septaria, and silica-carbonate nodules. Radiometric dating of bentonites in central Utah revealed that the upper Brushy Basin member is Early Cretaceous in age. Field and geochemical data support these conclusions and aid the understanding of the exact nature of the depositional basin, environments, stratigraphy, and paleotectonics of the Upper Jurassic-Lower Cretaceous interval in the Western Interior.

  12. 76 FR 29021 - Written Re-Evaluation and Record of Decision for the Final Environmental Impact Statement for the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-19

    ... (FR) in August 2010, regarding the intent to rule on the Panama City-Bay County Airport and Industrial... Federal Aviation Administration Written Re-Evaluation and Record of Decision for the Final Environmental.... ACTION: Notice of availability of written re-evaluation and Record of Decision for the...

  13. Precipitated silica as flow regulator.

    PubMed

    Müller, Anne-Kathrin; Ruppel, Joanna; Drexel, Claus-Peter; Zimmermann, Ingfried

    2008-08-01

    Flow regulators are added to solid pharmaceutical formulations to improve the flow properties of the powder mixtures. The primary particles of the flow regulators exist in the form of huge agglomerates which are broken down into smaller aggregates during the blending process. These smaller aggregates adsorb at the surface of the solid's grains and thus diminish attractive Van-der-Waals-forces by increasing the roughness of the host's surface. In most cases amorphous silica is used as flow additive but material properties like particle size or bond strength influence the desagglomeration tendency of the agglomerates and thus the flow regulating potency of each silica. For some silica types we will show that the differences in their flow regulating potency are due to the rate and extent by which they are able to cover the surface of the host particles. Binary powder mixtures consisting of a pharmaceutical excipient and an added flow regulator were blended in a Turbula mixer for a defined period of time. As pharmaceutical excipient corn starch was used. The flow regulators were represented by a selection of amorphous silicon dioxide types like a commercial fumed silica and various types of SIPERNAT precipitated silica provided by Evonik-Degussa GmbH, Hanau, Germany. Flowability parameters of the mixtures were characterized by means of a tensile strength tester. The reduction of tensile strength with the blending time can be correlated with an increase in fragmentation of the flow regulator. PMID:18595668

  14. The Toxicity of Precipitated Silica

    PubMed Central

    Byers, P. D.; Gage, J. C.

    1961-01-01

    The proportion of respirable particles in dust clouds generated from three samples of precipitated silica has been shown to range between one-quarter and one-third by weight. After a single intratracheal dose of the silicas to rats, chemical analysis shows a progressive disappearance of silica from the lungs, though it is still detectable after 12 months. Some silica appears in the liver and kidneys but in two of the three samples none remains after 12 months. The nature and duration of the lung lesions produced in rats after a single intratracheal injection are described. A mild degree of fibrosis was observed which showed a steady regression with time and was to some extent influenced by the nature of the silica injected. The lesions showed little resemblance to those arising from quartz and were more akin to those produced by non-fibrogenic dusts. Recommendations are made for the precautions to be taken during the industrial handling of these dusts. Images PMID:13875292

  15. Silica-volatile interaction and the geological cause of the Xuan Wei lung cancer epidemic

    SciTech Connect

    David J. Large; Shona Kelly; Baruch Spiro; Linwei Tian; Longyi Shao; Robert Finkelman; Mingquan Zhang; Chris Somerfield; Steve Plint; Yasmin Ali; Yiping Zhou

    2009-12-01

    Parts of Xuan Wei County, Yunnan Province, China have the highest known lung cancer mortality in nonsmoking women. This high mortality displays a clear spatial relationship to the mines producing coal from the uppermost Permian. Geochemical, petrographic, and grain size analyses were undertaken on a set of coal samples from Xuan Wei. Results demonstrate that the single geochemical property that makes this coal unusual is its high concentration of quartz (13.5 wt %) of which 35-55% occurs as < 10 {mu}m grains. We propose the potential for silica-volatile interaction (PSVI) as a new method for assessing the combined influence of silica and volatile organic matter and use this as a basis for re-evaluating existing ecological data. Published lung cancer mortality values are more strongly correlated with PSVI values for Xuan Wei coal than with volatiles or silica alone and the PSVI values measured are distinct from those of other coals. Finally we propose that the localization of this epidemic to Xuan Wei results from enhanced weathering of the local Emeishan basalts as a consequence of geochemical perturbations at the Permo-Triassic Boundary.

  16. Loveless Frump as Hip and Sexy Party Girl: A Reevaluation of the Old-Maid Stereotype.

    ERIC Educational Resources Information Center

    Adams, Katherine C.

    2000-01-01

    Argues for a reevaluation of the old-maid stereotype that will allow professionals in the library and information science (LIS) field to embrace digital technology while remaining mindful of their distinctiveness and recognizing the stereotype as an important part of their collective identity and professional history. (Contains 55 references.)…

  17. 75 FR 55846 - Draft Re-Evaluation for Environmental Impact Statement: Sikorsky Memorial Airport, Stratford, CT

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-14

    ... Region, 16 New England Executive Park, Burlington, MA, 781-238-7613. Stratford Public Library, 2203 Main St., Stratford, CT, 203-385- 4161. Bridgeport Public Library, Borroughs Bldg., 925 Broad St.... SUMMARY: The FAA is issuing this notice to advise the public that a Draft Re-Evaluation for...

  18. 42 CFR 405.213 - Re-evaluation of a device categorization.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 2 2011-10-01 2011-10-01 false Re-evaluation of a device categorization. 405.213 Section 405.213 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM FEDERAL HEALTH INSURANCE FOR THE AGED AND DISABLED Medical Services Coverage Decisions That Relate to Health...

  19. Reevaluating the Aims of Modern Dance Training in Korea: Toward a Whole Dancer

    ERIC Educational Resources Information Center

    Kim, Na-ye

    2013-01-01

    This study reevaluates modern dance training in Korea and attempts to identify possible improvements. This study is based on the rationale that Korean modern dance training must recover its nature of a holistic connection between body and mind. A qualitative methodology was used to interpret data from in-depth interviews and open-ended…

  20. Re-Evaluation Co-Counseling: A Method of Peer Self Help.

    ERIC Educational Resources Information Center

    Rockman, Ilene F.

    The college and university counseling center traditionally employs standard techniques in helping students, faculty, and staff in overcoming problems of mental stress (Berman, 1972). A technique suitable to both individual and group sessions, but rarely utilized is Re-Evaluation Co-Counseling or R.C. For the past twenty years, R.C. has gained an…

  1. 12 CFR 560.172 - Re-evaluation of real estate owned.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... estate that is sold and reacquired less than 12 months subsequent to the most recent appraisal made... 12 Banks and Banking 5 2011-01-01 2011-01-01 false Re-evaluation of real estate owned. 560.172... of real estate owned. A savings association shall appraise each parcel of real estate owned at...

  2. 12 CFR 560.172 - Re-evaluation of real estate owned.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... estate that is sold and reacquired less than 12 months subsequent to the most recent appraisal made... 12 Banks and Banking 5 2010-01-01 2010-01-01 false Re-evaluation of real estate owned. 560.172... of real estate owned. A savings association shall appraise each parcel of real estate owned at...

  3. Reevaluation of the Amsterdam Inventory for Auditory Disability and Handicap Using Item Response Theory

    ERIC Educational Resources Information Center

    Hospers, J. Mirjam Boeschen; Smits, Niels; Smits, Cas; Stam, Mariska; Terwee, Caroline B.; Kramer, Sophia E.

    2016-01-01

    Purpose: We reevaluated the psychometric properties of the Amsterdam Inventory for Auditory Disability and Handicap (AIADH; Kramer, Kapteyn, Festen, & Tobi, 1995) using item response theory. Item response theory describes item functioning along an ability continuum. Method: Cross-sectional data from 2,352 adults with and without hearing…

  4. 34 CFR 602.19 - Monitoring and reevaluation of accredited institutions and programs.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 3 2011-07-01 2011-07-01 false Monitoring and reevaluation of accredited institutions and programs. 602.19 Section 602.19 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION THE SECRETARY'S RECOGNITION OF ACCREDITING AGENCIES The Criteria...

  5. 34 CFR 602.19 - Monitoring and reevaluation of accredited institutions and programs.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... institution it has accredited that offers distance education or correspondence education. If any such... 34 Education 3 2012-07-01 2012-07-01 false Monitoring and reevaluation of accredited institutions and programs. 602.19 Section 602.19 Education Regulations of the Offices of the Department...

  6. 34 CFR 602.19 - Monitoring and reevaluation of accredited institutions and programs.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... institution it has accredited that offers distance education or correspondence education. If any such... 34 Education 3 2013-07-01 2013-07-01 false Monitoring and reevaluation of accredited institutions and programs. 602.19 Section 602.19 Education Regulations of the Offices of the Department...

  7. 34 CFR 602.19 - Monitoring and reevaluation of accredited institutions and programs.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... institution it has accredited that offers distance education or correspondence education. If any such... 34 Education 3 2014-07-01 2014-07-01 false Monitoring and reevaluation of accredited institutions and programs. 602.19 Section 602.19 Education Regulations of the Offices of the Department...

  8. 75 FR 49930 - Stakeholder Meeting Regarding Re-Evaluation of Currently Approved Total Coliform Analytical Methods

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-16

    ... Methods AGENCY: Environmental Protection Agency (EPA). ACTION: Notice. SUMMARY: The Environmental...) analytical methods. At these meetings, stakeholders will be given an opportunity to discuss potential elements of a method re-evaluation study, such as developing a reference coliform/non-coliform library...

  9. Educational Reevaluation, Political Transformation: Québec and Higher Education

    ERIC Educational Resources Information Center

    Unger, Zoe

    2013-01-01

    This paper considers the history of Québec's higher education system and the reforms that have contributed to the role of education in the province. Québec's education system has repeatedly been a site for social and political transformation; most recently, reevaluation of education's role in the province has revealed a tension…

  10. 34 CFR 300.305 - Additional requirements for evaluations and reevaluations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... STATES FOR THE EDUCATION OF CHILDREN WITH DISABILITIES Evaluations, Eligibility Determinations, Individualized Education Programs, and Educational Placements Evaluations and Reevaluations § 300.305 Additional... 34 Education 2 2010-07-01 2010-07-01 false Additional requirements for evaluations...

  11. 34 CFR 300.305 - Additional requirements for evaluations and reevaluations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... STATES FOR THE EDUCATION OF CHILDREN WITH DISABILITIES Evaluations, Eligibility Determinations, Individualized Education Programs, and Educational Placements Evaluations and Reevaluations § 300.305 Additional... 34 Education 2 2011-07-01 2010-07-01 true Additional requirements for evaluations...

  12. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  13. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...: (i) Amorphous fumed hydrophobic silica: Not less than 99.0 percent silicon dioxide after ignition... dichlorodimethylsilane. (ii) Precipated hydrophobic silica: Not less than 94.0 percent silicon dioxide after...

  14. Physisorbed Water on Silica at Mars Temperatures

    NASA Technical Reports Server (NTRS)

    Sutter, B.; Sriwatanapongse, W.; Quinn, R.; Klug, C.; Zent, A.

    2002-01-01

    The usefulness of nuclear magnetic resonance spectroscopy in probing water interactions on silica at Mars temperatures is discussed. Results indicate that two types of water occur with silica at Mars temperatures. Additional information is contained in the original extended abstract.

  15. Optothermal nonlinearity of silica aerogel

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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 (≃10-12 m2/W), with negligible optical nonlinear absorption. The nonlinear coefficient can be increased to values in the range of 10-10 m2/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.

  16. Disentangling protein-silica interactions.

    PubMed

    Giussani, Lara; Tabacchi, Gloria; Gianotti, Enrica; Coluccia, Salvatore; Fois, Ettore

    2012-03-28

    We present the results of modelling studies aimed at the understanding of the interaction of a 7 nm sized water droplet containing a negatively charged globular protein with flat silica surfaces. We show how the droplet interaction with the surface depends on the electrostatic surface charge, and that adhesion of the droplet occurs when the surface is negatively charged as well. The key role of water and of the charge-balancing counter ions in mediating the surface-protein adhesion is highlighted. The relevance of the present results with respect to the production of bioinorganic hybrids via encapsulation of proteins inside mesoporous silica materials is discussed.

  17. Silica Materials for Medical Applications

    PubMed Central

    Vallet-Regí, María; Balas, Francisco

    2008-01-01

    The two main applications of silica-based materials in medicine and biotechnology, i.e. for bone-repairing devices and for drug delivery systems, are presented and discussed. The influence of the structure and chemical composition in the final characteristics and properties of every silica-based material is also shown as a function of the both applications presented. The adequate combination of the synthesis techniques, template systems and additives leads to the development of materials that merge the bioactive behavior with the drug carrier ability. These systems could be excellent candidates as materials for the development of devices for tissue engineering. PMID:19662110

  18. Silica Precursors Derived From TEOS

    NASA Technical Reports Server (NTRS)

    Philipp, Warren H.

    1993-01-01

    Two high-char-yield polysiloxane polymers developed. Designated as TEOS-A and TEOS-B with silica char yields of 55% and 22%, respectively. These free-flowing polymers are Newtonium liquids instead of thick gels. Easily synthesized by controlled hydrolysis of inexpensive tetraethoxysilane (TEOS). Adhesive properties of TEOS-A suggest its use as binder for fabrication of ceramic articles from oxide powders. Less-viscous and more-fluid lower-molecular-weight TEOS-B used to infiltrate already-formed porous ceramic compacts to increase densities without effecting shrinkage. Also used as paint to coat substrate with silica, and to make highly pure silicate powders.

  19. Removal of dissolved and colloidal silica

    DOEpatents

    Midkiff, William S.

    2002-01-01

    Small amorphous silica particles are used to provide a relatively large surface area upon which silica will preferentially adsorb, thereby preventing or substantially reducing scaling caused by deposition of silica on evaporative cooling tower components, especially heat exchange surfaces. The silica spheres are contacted by the cooling tower water in a sidestream reactor, then separated using gravity separation, microfiltration, vacuum filtration, or other suitable separation technology. Cooling tower modifications for implementing the invention process have been designed.

  20. The properties of silica-gelatin composites

    NASA Astrophysics Data System (ADS)

    Stavinskaya, O. N.; Laguta, I. V.

    2010-06-01

    Silica-gelatin composites with various silica-to-gelatin ratios were obtained. The influence of high-dispersity silica on the swelling of composites in water and desorption of pyridoxine and thiamine vitamins incorporated into the material was studied. The addition of silica to gelatin was shown to increase the time of the dissolution of the materials in aqueous medium and decelerate the desorption of vitamins.

  1. Sonochemical coating of magnetite nanoparticles with silica.

    PubMed

    Dang, Feng; Enomoto, Naoya; Hojo, Junichi; Enpuku, Keiji

    2010-01-01

    Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles. The dispersibility of silica-coated magnetite particles in aqueous solution was improved significantly and the agglomerate particle size was decreased to 110 nm. It was found that the agglomerate particle size of silica-coated magnetite particles was mainly decided by the coating temperature and the pH value in the silica-coating process. The weight ratio of silica in silica-coated magnetite particles was mainly decided by the pH value in the silica-coating process. The dispersibility of silica-coated magnetite particles was mainly decided by the agglomerate particle size of the suspension. The oxidation of magnetite particles in air was limited through the coated silica. The magnetism of silica-coated magnetite particles decreased slightly after silica-coating.

  2. Silica optical fibers: technology update

    NASA Astrophysics Data System (ADS)

    Krohn, David A.; McCann, Brian P.

    1995-05-01

    Silica-core optical fibers have long been the standard delivery medium for medical laser delivery systems. Their high strength, excellent flexibility, and low cost continue to make them the fiber of choice for systems operating from 300 to 2200 nm. An overview of the current fiber constructions available to the industry is reviewed. Silicone-clad fibers, hard- fluoropolymer clad fibers and silica-clad fibers are briefly compared in terms of mechanical and optical properties. The variety of fiber coatings available is also discussed. A significant product development of silica fiber delivery systems has been in side-firing laser delivery systems for Urology. These devices utilize silica-core fibers to project the laser energy at a substantial lateral angle to the conventional delivery system, typically 40 to 100 degrees off axis. Many unique distal tips have been designed to meet the needs of this potentially enormous application. There are three primary technologies employed in side-firing laser delivery systems: reflection off of an attached medium; reflection within an angle-polished fiber through total internal reflection; and reflection from both an angle-polished fiber and an outside medium. Each technology is presented and compared on the basis of operation modality, transmission efficiency, and power-handling performance.

  3. The Phagocytosis and Toxicity of Amorphous Silica

    PubMed Central

    Costantini, Lindsey M.; Gilberti, Renée M.; Knecht, David A.

    2011-01-01

    Background Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica. Methodology/Principal Findings Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles. The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37°C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica. Conclusions/Significance Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both

  4. Uranium incorporation into amorphous silica.

    PubMed

    Massey, Michael S; Lezama-Pacheco, Juan S; Nelson, Joey M; Fendorf, Scott; Maher, Kate

    2014-01-01

    High concentrations of uranium are commonly observed in naturally occurring amorphous silica (including opal) deposits, suggesting that incorporation of U into amorphous silica may represent a natural attenuation mechanism and promising strategy for U remediation. However, the stability of uranium in opaline silicates, determined in part by the binding mechanism for U, is an important factor in its long-term fate. U may bind directly to the opaline silicate matrix, or to materials such as iron (hydr)oxides that are subsequently occluded within the opal. Here, we examine the coordination environment of U within opaline silica to elucidate incorporation mechanisms. Precipitates (with and without ferrihydrite inclusions) were synthesized from U-bearing sodium metasilicate solutions, buffered at pH ∼ 5.6. Natural and synthetic solids were analyzed with X-ray absorption spectroscopy and a suite of other techniques. In synthetic amorphous silica, U was coordinated by silicate in a double corner-sharing coordination geometry (Si at ∼ 3.8-3.9 Å) and a small amount of uranyl and silicate in a bidentate, mononuclear (edge-sharing) coordination (Si at ∼ 3.1-3.2 Å, U at ∼ 3.8-3.9 Å). In iron-bearing synthetic solids, U was adsorbed to iron (hydr)oxide, but the coordination environment also contained silicate in both edge-sharing and corner-sharing coordination. Uranium local coordination in synthetic solids is similar to that of natural U-bearing opals that retain U for millions of years. The stability and extent of U incorporation into opaline and amorphous silica represents a long-term repository for U that may provide an alternative strategy for remediation of U contamination. PMID:24984107

  5. Determination of 1,3-butadiene in workplace air: reevaluation of NIOSH (National Institute for Occupational Safety and Health) Method S91 and development of NIOSH Method 1024

    SciTech Connect

    Lunsford, R.A.; Gagnon, Y.T.

    1988-08-24

    NIOSH Method S91 for the determination of 1,3-butadiene in air was reevaluated, and a new method was developed. Limitations to Method S91 included the fact that the lower quantitation limit appeared to be about 3.4 parts per million (ppm) and the packed-column gas-chromatographic analysis was subject to interference. The new method developed, Method 1024, employed collection on tandem coconut-shell charcoal tubes, desorption with methylene chloride, and high-resolution gas-chromatographic analysis. Evaluation of Method 1024 indicated that it should be useful for determining full-shift time-weighted average exposures in humid air at concentrations ranging from 0.4 to 10 ppm. The sampler's capacity should permit quantitation of levels up to 100 ppm if desorbed samples are diluted so that they fall in the calibration range. In the chromatographic process, the combination of backflushable precolumn and aluminum oxide fused-silica capillary analytical columns offered the advantages of enhanced sensitivity enabling detection down to 0.005 ppm in 25 liters, and enhanced selectivity, limiting the need for confirmatory techniques.

  6. Silica Lubrication in Faults (Invited)

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Rempe, M.; Lamothe, K.; Kirkpatrick, J. D.; White, J. C.; Mitchell, T. M.; Andrews, M.; Di Toro, G.

    2013-12-01

    Silica-rich rocks are common in the crust, so silica lubrication may be important for causing fault weakening during earthquakes if the phenomenon occurs in nature. In laboratory friction experiments on chert, dramatic shear weakening has been attributed to amorphization and attraction of water from atmospheric humidity to form a 'silica gel'. Few observations of the slip surfaces have been reported, and the details of weakening mechanism(s) remain enigmatic. Therefore, no criteria exist on which to make comparisons of experimental materials to natural faults. We performed a series of friction experiments, characterized the materials formed on the sliding surface, and compared these to a geological fault in the same rock type. Experiments were performed in the presence of room humidity at 2.5 MPa normal stress with 3 and 30 m total displacement for a variety of slip rates (10-4 - 10-1 m/s). The friction coefficient (μ) reduced from >0.6 to ~0.2 at 10-1 m/s, but only fell to ~0.4 at 10-2 - 10-4 m/s. The slip surfaces and wear material were observed using laser confocal Raman microscopy, electron microprobe, X-ray diffraction, and transmission electron microscopy. Experiments at 10-1 m/s formed wear material consisting of ≤1 μm powder that is aggregated into irregular 5-20 μm clumps. Some material disaggregated during analysis with electron beams and lasers, suggesting hydrous and unstable components. Compressed powder forms smooth pavements on the surface in which grains are not visible (if present, they are <100 nm). Powder contains amorphous material and as yet unidentified crystalline and non-crystalline forms of silica (not quartz), while the worn chert surface underneath shows Raman spectra consistent with a mixture of quartz and amorphous material. If silica amorphization facilitates shear weakening in natural faults, similar wear materials should be formed, and we may be able to identify them through microstructural studies. However, the sub

  7. Re-evaluating the northeastern Minnesota moose decline and the role of wolves

    USGS Publications Warehouse

    Mech, L. David; Fieberg, John

    2014-01-01

    We re-evaluated findings from Lenarz et al. (2009) that adult moose (Alces alces) survival in northeastern Minnesota was related to high January temperatures and that predation by wolves (Canis lupus) played a minor role. We found significant inverse relationships between annual wolf numbers in part of the moose range and various moose demographics from 2003 to 2013 that suggested a stronger role of wolves than heretofore believed. To re-evaluate the temperature findings, we conducted a simulation study, mimicking the approach taken by Lenarz et al. (2009), to explore the potential for concluding a significant relationship exists between temperature and survival, when no association exists. We found that the high R2s and low probabilities associated with the regression models in Lenarz et al. (2009) should be viewed cautiously in light of the large number of fitted models (m = 45) and few observations (n = 6 for each of 5 response variables).

  8. Orphan caribou, Rangifer tarandus, calves: A re-evaluation of overwinter survival data

    USGS Publications Warehouse

    Joly, Kyle

    2000-01-01

    Low sample size and high variation within populations reduce power of statistical tests. These aspects of statistical power appear to have affected an analysis comparing overwinter survival rates of non-orphan and orphan Caribou (Rangifer tarandus) calves by an earlier study for the Porcupine Caribou Herd. A re-evaluation of the data revealed that conclusions about a lack of significant difference in the overwinter survival rates between orphan and non-orphan calves were premature.

  9. Reevaluating nuclear safety and security in a post 9/11 era.

    SciTech Connect

    Booker, Paul M.; Brown, Lisa M.

    2005-07-01

    This report has the following topics: (1) Changing perspectives on nuclear safety and security; (2) Evolving needs in a post-9/11 era; (3) Nuclear Weapons--An attractive terrorist target; (4) The case for increased safety; (5) Evolution of current nuclear weapons safety and security; (6) Integrated surety; (7) The role of safety and security in enabling responsiveness; (8) Advances in surety technologies; and (9) Reevaluating safety.

  10. [Research about re-evaluation of screening of traditonal Chinese medicine symptoms item of post-marketing medicine Xuezhikang].

    PubMed

    He, Wei; Xie, Yanming; Wang, Yongyan

    2011-10-01

    The purpose of post-marketing Chinese medicine re-evaluation is to identify Chinese medicine clinical indications, while designing scientific and rational of Chinese medicine symptoms items are important to the result of symptoms re-evaluation. This study give screening of traditional Chinese medicine(TCM) symptoms item of post-marketing medicine Xuezhikang re-evaluation as example that reference to principle dyslipidemia clinical research, academic dissertations, Xuezhikang directions, clinical expert practice experience etc. while standardization those symptom names and screening 41 dyslipidemia common symptoms. Furthermore, this paper discuss about the accoerdance and announcements when screening symptoms item, so as to providing a research thread to manufacture PRO chart for post-marketing medicine re-evaluation. PMID:22292395

  11. Reevaluating Surface Composition of Asteroid (4) Vesta by Comparing HED Spectral Data with Dawn Framing Camera (FC) Observations

    NASA Astrophysics Data System (ADS)

    Giebner, T.; Jaumann, R.; Schröder, S.

    2016-08-01

    This master's thesis project tries to reevaluate previous findings on asteroid (4) Vesta's surface composition by using DAWN FC Filter image ratios in a new way in order to identify HED (howardite, eucrite, diogenite) lithologies on the surface.

  12. Defining the extent of Chesapeake Bay toxics problems: Findings from the basin-wide strategy reevaluation

    SciTech Connect

    Batiuk, R.A.

    1994-12-31

    The Chesapeake Bay Program`s Toxics Subcommittee conducted an comprehensive reevaluation of the 1989 Basin-wide Toxics Reduction Strategy during 1992-1993. The objectives of this strategy reevaluation were to define what was known about the nature, extent, and magnitude of Bay toxics problems; what steps needed to be taken to reduce and prevent impacts from toxics; and what information still needed to be determined to support management decisions for taking additional reduction and prevention actions. The Toxics Subcommittee investigated and evaluated the complex nature of the Bay`s toxics conditions and problems through a two-year schedule of meetings, research workshops, and information-gathering forums. Key to building a technical consensus on the nature and extent of the Bay`s toxics conditions and problems was a series of seven critical issue forums. The major findings from these critical issue forums and the overall strategy reevaluation included documentation of severe localized toxicity problems, evidence of toxic effects in areas previously through to be uncontaminated, and widespread low levels of toxics in all Bay habitats sampled. These findings have resulted in a revised basinwide strategy focused on pollution prevention, regulatory program implementation, regional problem areas, and directed toxics assessments.

  13. Consolidated silica glass from nanoparticles

    SciTech Connect

    Mayerhoefer, Thomas G. Shen Zhijian; Leonova, Ekaterina; Eden, Mattias; Kriltz, Antje; Popp, Juergen

    2008-09-15

    A dense silica glass was prepared by consolidating a highly dispersed silicic acid powder (particle size <10 nm) with the Spark Plasma Sintering (SPS) technique. The glass was characterized by ellipsometry, transmission electron microscopy (TEM), infrared reflectance and transmittance spectroscopy, as well as by Raman, UV-Vis-NIR and solid-state nuclear magnetic resonance (NMR) spectroscopy. The prototypic sample showed a transmittance of about 63% compared to silica glass in the UV-Vis spectral range. Based on the results of infrared transmittance spectroscopy this lower transparency is due to the comparably high water content, which is about 40 times higher than that in silica glass. {sup 1}H magic-angle spinning (MAS) NMR confirmed an increase in hydroxyl groups in the sample prepared by SPS relative to that of the conventional SiO{sub 2} reference glass. Aside from the comparably high water content, we conclude from the similarity of the IR-reflectance and the {sup 29}Si MAS NMR spectra of the SPS sample and the corresponding spectra of the conventionally prepared silica glass, that the short- and medium-range order is virtually the same in both materials. Raman spectroscopy, however, suggests that the number of three- and four-membered rings is significantly smaller in the SPS sample compared to the conventionally prepared sample. Based on these results we conclude that it is possible to prepare glasses by compacting amorphous powders by the SPS process. The SPS process may therefore enable the preparation of glasses with compositions inaccessible by conventional methods. - Graphical abstract: We report the preparation of SiO{sub 2} glass by consolidating a highly dispersed silicic acid powder with the Spark Plasma Sintering (SPS) technique. The glass was characterized by ellipsometry, transmission electron microscopy (TEM), infrared reflectance and transmittance spectroscopy, as well as by Raman-, UV-Vis-NIR- and solid-state nuclear magnetic resonance (NMR

  14. The Southern Ocean silica cycle

    NASA Astrophysics Data System (ADS)

    Tréguer, Paul J.

    2014-11-01

    The Southern Ocean is a major opal sink and plays a key role in the silica cycle of the world ocean. So far however, a complete cycle of silicon in the Southern Ocean has not been published. On one hand, Southern Ocean surface waters receive considerable amounts of silicic acid (dissolved silica, DSi) from the rest of the world ocean through the upwelling of the Circumpolar Deep Water, fed by contributions of deep waters of the Atlantic, Indian, and Pacific Oceans. On the other hand, the Southern Ocean exports a considerable flux of the silicic acid that is not used by diatoms in surface waters through the northward pathways of the Sub-Antarctic Mode Water, of the Antarctic Intermediate Water, and of the Antarctic Bottom Water. Thus the Southern Ocean is a source of DSi for the rest of the world ocean. Here we show that the Southern Ocean is a net importer of DSi: because there is no significant external input of DSi, the flux of DSi imported through the Circumpolar Deep Water pathway compensates the sink flux of biogenic silica in sediments.

  15. Silica exposure and systemic vasculitis.

    PubMed Central

    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, 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. PMID:14644669

  16. Status report and FY95 plans -- Re-evaluation of NOAA Dobson spectrophotometer total ozone data. 1994 annual report

    SciTech Connect

    1994-12-31

    The goal of this project was to re-evaluate NOAA/CMDL Dobson spectrophotometer total ozone data during FY94 from the stations Haute Provence, France; Lauder, New Zealand; Perth, Australia; and Poker Flat, Alaska and the Umkehr data from Boulder, Colorado and Mauna Loa, Hawaii. During the second year the authors planned to re-evaluate total ozone data from Byrd, Hallett and South Pole, Antarctica; Fairbanks, Alaska; Puerto Montt, Chile; Huancayo, Peru and Umkehr data from Huancayo.

  17. Toxicity assessment of silica nanoparticles, functionalised silica nanoparticles, and HASE-grafted silica nanoparticles.

    PubMed

    Clément, Laura; Zenerino, Arnaud; Hurel, Charlotte; Amigoni, Sonia; Taffin de Givenchy, Elisabeth; Guittard, Frédéric; Marmier, Nicolas

    2013-04-15

    Numerous nanomaterials have recently been developed, and numerous practical applications have been found in water treatment, medicine, cosmetics, and engineering. Associative polymers, such as hydrophobically modified alkali-soluble emulsion (HASE) systems are involved in several applications and have been extensively studied due to their ability to form three-dimensional networked gels. However, the data on the potential environmental effects of this polymers are scarce. The aim of this study is to assess the effect of functionalisation of silica nanoparticles, and coupling of functionalised silica nanoparticles to the associative polymer HASE on their toxicity. Thus, acute and chronic toxicity tests included a modified acute test (72 h) using daphnies, algae, and plants as model organisms. Gradient of toxicity varied with the tested organisms. Our results revealed that the functionalised nanoparticules and NP grafted polymer cause a global decrease in toxicity compared to commercial nanoparticule and HASE polymer. PMID:23474257

  18. Non-occupational exposure to silica dust

    PubMed Central

    Bhagia, L. J.

    2012-01-01

    Occupational exposure to silica occurs at workplaces in factories like quartz crushing facilities (silica flour milling), agate, ceramic, slate pencil, glass, stone quarries and mines, etc., Non-occupational exposure to silica dust can be from industrial sources in the vicinity of the industry as well as non-industrial sources. Recently, public concern regarding non-occupational or ambient exposure to crystalline silica has emerged making it important to gather information available on non-occupational exposures to silica dust and non-occupational silicosis. This paper reviews various non-occupational exposures reported in literature including some studies by the author. Methodology used in assessment of non-occupational exposures, standards for non-occupational exposures to silica dust and indirect estimation of cumulative risk % are also discussed. PMID:23776316

  19. Silica Extraction at Mammoth Lakes, California

    SciTech Connect

    Bourcier, W; Ralph, W; Johnson, M; Bruton, C; Gutierrez, P

    2006-06-07

    The purpose of this project is to develop a cost-effective method to extract marketable silica (SiO{sub 2}) from fluids at the Mammoth Lakes, California geothermal power plant. Silica provides an additional revenue source for the geothermal power industry and therefore lowers the costs of geothermal power production. The use of this type of ''solution mining'' to extract resources eliminates the need for acquiring these resources through energy intensive and environmentally damaging mining technologies. We have demonstrated that both precipitated and colloidal silica can be produced from the geothermal fluids at Mammoth Lakes by first concentrating the silica to over 600 ppm using reverse osmosis (RO). The RO permeate can be used in evaporative cooling at the plant; the RO concentrate is used for silica and potentially other resource extraction (Li, Cs, Rb). Preliminary results suggest that silica recovery at Mammoth Lakes could reduce the cost of geothermal electricity production by 1.0 cents/kWh.

  20. Process for preparing polymer reinforced silica aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Capadona, Lynn A. (Inventor)

    2011-01-01

    Process for preparing polymer-reinforced silica aerogels which comprises a one-pot reaction of at least one alkoxy silane in the presence of effective amounts of a polymer precursor to obtain a silica reaction product, the reaction product is gelled and subsequently subjected to conditions that promotes polymerization of the precursor and then supercritically dried to obtain the polymer-reinforced monolithic silica aerogels.

  1. Mesoporous Silica: A Suitable Adsorbent for Amines

    PubMed Central

    2009-01-01

    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. PMID:20628459

  2. A Pd/silica composite with highly uniform Pd nanoparticles on silica lamella via layered silicate

    NASA Astrophysics Data System (ADS)

    Hao, Jing; Cui, Zhi-Min; Cao, Chang-Yan; Song, Weiguo

    2016-08-01

    Pd nanoparticles was loaded on silica lamella via layered silicate through a simple ion-exchange and in situ reduction method. The obtained Pd/silica composite has Pd nanoparticles with highly uniform size dispersed well on the silica lamella. The Pd/silica composite is active and recoverable catalyst for the hydrogenation reaction and the reaction can be completed in a short time of 2 h at room temperature and 1 atm H2 pressure.

  3. Cellular membrane trafficking of mesoporous silica nanoparticles

    SciTech Connect

    Fang, I-Ju

    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

  4. Moisture Transport in Silica Gel Particle Beds: I. Theoretical Study

    SciTech Connect

    Pesaran, A. A.; Mills, A. F.

    1986-08-01

    Diffusion mechanisms of moisture within silica gel particles are investigated. It is found that for microporous silica gel surface diffusion is the dominant mechanism of moisture transport, while for macroporous silica gel both Knudsen and surface diffusion are important.

  5. Sulphur-doped silica fibres

    SciTech Connect

    Gerasimova, V I; Rybaltovskii, A O; Chernov, P V; Mashinsky, V M; Sazhin, O D; Medvedkov, O I; Rybaltovsky, A A; Khrapko, R R

    2003-01-31

    An optical fibre with low optical losses is manufactured from a sulphur-doped quartz glass. Optical absorption spectra are measured for various parts of the fibre core. Most of the bands of these spectra are assigned to oxygen-deficient centres and colour centres containing sulphur atoms. The photosensitivity of glasses exposed to laser radiation at wavelengths of 193 and 244 nm is investigated to estimate the possibility of their application for producing photorefracting devices. A Bragg grating of the refractive index with {Delta}n = 7.8 x 10{sup -4} is written in a sulphur-doped silica fibre. (fibre optics)

  6. Nanoscale control of silica particle formation via silk-silica fusion proteins for bone regeneration.

    PubMed

    Mieszawska, Aneta J; Nadkarni, Lauren D; Perry, Carole C; Kaplan, David L

    2010-10-26

    The biomimetic design of silk/silica fusion proteins was carried out, combining the self assembling domains of spider dragline silk (Nephila clavipes) and silaffin derived R5 peptide of Cylindrotheca fusiformis that is responsible for silica mineralization. Genetic engineering was used to generate the protein-based biomaterials incorporating the physical properties of both components. With genetic control over the nanodomain sizes and chemistry, as well as modification of synthetic conditions for silica formation, controlled mineralized silk films with different silica morphologies and distributions were successfully generated; generating 3D porous networks, clustered silica nanoparticles (SNPs), or single SNPs. Silk serves as the organic scaffolding to control the material stability and multiprocessing makes silk/silica biomaterials suitable for different tissue regenerative applications. The influence of these new silk-silica composite systems on osteogenesis was evaluated with human mesenchymal stem cells (hMSCs) subjected to osteogenic differentiation. hMSCs adhered, proliferated, and differentiated towards osteogenic lineages on the silk/silica films. The presence of the silica in the silk films influenced osteogenic gene expression, with the upregulation of alkaline phosphatase (ALP), bone sialoprotein (BSP), and collagen type 1 (Col 1) markers. Evidence for early bone formation as calcium deposits was observed on silk films with silica. These results indicate the potential utility of these new silk/silica systems towards bone regeneration. PMID:20976116

  7. Biomimetic silica encapsultation of living cells

    NASA Astrophysics Data System (ADS)

    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.

  8. Reusable silica surface-insulation material

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Smith, M.; Leiser, D.

    1973-01-01

    Material was specifically developed for manufacture of insulating tiles, but it can be molded into other shapes as required. Basic raw materials are high-purity silica fiber, fumed-silica powder, and reagent-grade starch. Only purest materials are used, and care must be taken to avoid contamination during processing.

  9. Re-evaluation of classical prognostic factors in resectable ductal adenocarcinoma of the pancreas

    PubMed Central

    Åkerberg, Daniel; Ansari, Daniel; Andersson, Roland

    2016-01-01

    Pancreatic ductal adenocarcinoma carries a poor prognosis with annual deaths almost matching the reported incidence rates. Surgical resection offers the only potential cure. Yet, even among patients that undergo tumor resection, recurrence rates are high and long-term survival is scarce. Various tumor-related factors have been identified as predictors of survival after potentially curative resection. These factors include tumor size, lymph node disease, tumor grade, vascular invasion, perineural invasion and surgical resection margin. This article will re-evaluate the importance of these factors based on recent publications on the topic, with potential implications for treatment and outcome in patients with pancreatic cancer. PMID:27605878

  10. Source-term reevaluation for US commercial nuclear power reactors: a status report

    SciTech Connect

    Herzenberg, C.L.; Ball, J.R.; Ramaswami, D.

    1984-12-01

    Only results that had been discussed publicly, had been published in the open literature, or were available in preliminary reports as of September 30, 1984, are included here. More than 20 organizations are participating in source-term programs, which have been undertaken to examine severe accident phenomena in light-water power reactors (including the chemical and physical behavior of fission products under accident conditions), update and reevaluate source terms, and resolve differences between predictions and observations of radiation releases and related phenomena. Results from these source-term activities have been documented in over 100 publications to date.

  11. Re-evaluation of classical prognostic factors in resectable ductal adenocarcinoma of the pancreas.

    PubMed

    Åkerberg, Daniel; Ansari, Daniel; Andersson, Roland

    2016-07-28

    Pancreatic ductal adenocarcinoma carries a poor prognosis with annual deaths almost matching the reported incidence rates. Surgical resection offers the only potential cure. Yet, even among patients that undergo tumor resection, recurrence rates are high and long-term survival is scarce. Various tumor-related factors have been identified as predictors of survival after potentially curative resection. These factors include tumor size, lymph node disease, tumor grade, vascular invasion, perineural invasion and surgical resection margin. This article will re-evaluate the importance of these factors based on recent publications on the topic, with potential implications for treatment and outcome in patients with pancreatic cancer. PMID:27605878

  12. Re-evaluation of classical prognostic factors in resectable ductal adenocarcinoma of the pancreas

    PubMed Central

    Åkerberg, Daniel; Ansari, Daniel; Andersson, Roland

    2016-01-01

    Pancreatic ductal adenocarcinoma carries a poor prognosis with annual deaths almost matching the reported incidence rates. Surgical resection offers the only potential cure. Yet, even among patients that undergo tumor resection, recurrence rates are high and long-term survival is scarce. Various tumor-related factors have been identified as predictors of survival after potentially curative resection. These factors include tumor size, lymph node disease, tumor grade, vascular invasion, perineural invasion and surgical resection margin. This article will re-evaluate the importance of these factors based on recent publications on the topic, with potential implications for treatment and outcome in patients with pancreatic cancer.

  13. Human rights as myth and ceremony? Reevaluating the effectiveness of human rights treaties, 1981-2007.

    PubMed

    Cole, Wade M

    2012-01-01

    Much research has shown human rights treaties to be ineffective or even counterproductive, often contributing to greater levels of abuse among countries that ratify them. This article reevaluates the effect of four core human rights treaties on a variety of human rights outcomes. Unlike previous studies, it disaggregates treaty membership to examine the effect of relatively "stronger" and "weaker" commitments. Two-stage regression analyses that control for the endogeneity of treaty membership show that stronger commitments in the form of optional provisions that allow states and individuals to complain about human rights abuses are often associated with improved practices. The article discusses the scholarly and practical implications of these findings.

  14. Fire effects on silica fractionation

    NASA Astrophysics Data System (ADS)

    Unzué-Belmonte, Dácil; Schaller, Jörg; Vandevenne, Floor; Barao, Lúcia; Struyf, Eric; Meire, Patrick

    2015-04-01

    Fire events are expected to increase due to climate change, both in number and intensity Effects range from changes in soil biogeochemistry up to the whole ecosystem functioning and morphology. While N, P and C cycling have received quite some attention, little attention was paid to fire effects on the biogeochemical Si cycle and the consequences after a fire event. The Si cycle is a globally important biogeochemical cycle, with strong connections to other biogeochemical cycles, including C. Dissolved silica is taken up by plants to form protective structures called phytoliths, which become a part of the soil and contribute strongly to soil Si cycling upon litter burial. Different silica fractions are found in soils, with phytoliths among the most easily soluble, especially compared to silicate minerals. A whole set of secondary non-biogenic fractions exist, that also have a high reactivity (adsorbed Si, reactive secondary minerals…). Biogenic and other pedogenic secondary Si stocks form an important filter between weathering of mineral silicates and eventual transport of dissolved Si to rivers and the coastal zone. We used a new method to analyze the different reactive fractions of silica in the litter layer of 3 ecosystems after different fire treatments. Using a continuous extraction of Si and Al in 0.5M NaOH at 85°C, biogenic and non-biogenic alkaline reactive Si fractions can be separated based on their Si/Al ratios and their reactivity. We analyzed the silica fractionation after two burning treatments (no heating, 350°C and 550°C) from three types of litter (spruce forest, beech forest and Sphagnum peat). Reactive Si from litter of spruce and beech forest was purely biogenic, based on the observed Si/Al ratio. Beech litter (~2.2 % BSi) had two different biogenic silica pools, one reactive and one more refractory. Spruce litter (~1.5% BSi) showed only one fraction of biogenic Si. There was negligible biogenic Si present in the peat samples (<0.1%). While

  15. Sample Desorption/Onization From Mesoporous Silica

    DOEpatents

    Iyer, Srinivas; Dattelbaum, Andrew M.

    2005-10-25

    Mesoporous silica is shown to be a sample holder for laser desorption/ionization of mass spectrometry. Supported mesoporous silica was prepared by coating an ethanolic silicate solution having a removable surfactant onto a substrate to produce a self-assembled, ordered, nanocomposite silica thin film. The surfactant was chosen to provide a desired pore size between about 1 nanometer diameter and 50 nanometers diameter. Removal of the surfactant resulted in a mesoporous silica thin film on the substrate. Samples having a molecular weight below 1000, such as C.sub.60 and tryptophan, were adsorbed onto and into the mesoporous silica thin film sample holder and analyzed using laser desorption/ionization mass spectrometry.

  16. Electrical conductivity of concrete containing silica fume

    SciTech Connect

    Abo El-Enein, S.A.; Kotkata, M.F.; Hanna, G.B.; Saad, M.; Abd El Razek, M.M.

    1995-12-01

    The influence of silica fume on concrete properties represents an important technical research. In general, silica fume tends to improve both mechanical characteristics and durability of concrete. Thus the electrical properties of concrete containing silica fume can be studied to clarify its physical performance during hydration. The electrical conductivity of neat cement, mortar and concrete pastes was measured during setting and hardening. The ordinary Portland cement was partially replaced by different amounts of silica fume by weight. The changes in the electrical conductivity were reported during setting and hardening after gauging with water. The results of this study showed that the electrical conductivity can be used as an indication for the setting characteristics as well as the structural changes of the hardened pastes made with and without silica fume.

  17. Dense silica coatings on ceramic powder particles

    SciTech Connect

    Opitz, J.F.A.; Mayr, W.

    1995-09-01

    Dense silica coatings on the surface of inorganic powders particles are prepared by the hydrolysis of tetraethoxysilane (TEOS) in alcoholic suspensions. In a first reaction step, the TEOS is pre-hydrolysed in acidic solution and afterwards, a suspension of powder particles in this reaction solution is treated with ammonia which results in a dense silica coating of typically 10 - 100 nm thickness. Different luminescent powders which are used in the manufacture of cathode-ray tubes or fluorescent lamps have been coated by this procedure. The silica coating forms a transparent layer and the suspension properties of the coated powders are determined by the silica layer. The silica coating also protects sulfidic luminescent powders from being attacked by oxidizing agents like dichromate ions which are used in the suspension formulations for TV tube fabrication.

  18. The formation and deposition of primary silica granules - A new model of early Archean silica deposition

    NASA Astrophysics Data System (ADS)

    Stefurak, E. J.; Lowe, D. R.; Zentner, D.; Fischer, W. W.

    2013-12-01

    In the modern silica cycle, biologically-mediated silica precipitation provides the dominant sink for dissolved silica in seawater, with additional smaller sinks in the form of authigenic phyllosilicates and silica cements. Fundamental questions remain about the mechanics of the processes responsible for removing silica from seawater prior to the evolution of silica biomineralization in late Proterozoic time, with important implications for the chemistry of seawater on the early Earth, including alkalinity budgets and the efficiency of the silicate weathering feedback. The degree to which dissolved silica leaves seawater as authigenic phyllosilicates instead of amorphous silica is important because these 'reverse weathering' reactions do not consume CO2. The abundant presence of siliceous sedimentary rocks in Archean sequences, mainly in the form of chert, reinforces the inference that abiotic silica precipitation played a more significant role during Archean time. Previous authors hypothesized that these cherts formed as primary marine precipitates, but were unable to identify a specific mode of sedimentation. Here we present sedimentologic, petrographic, and geochemical evidence that some and perhaps many Archean cherts were deposited exclusively or in large part as primary, sub-spherical, structureless, sand-sized silica grains, here termed silica granules, which precipitated within marine waters. This mode of silica deposition appears to be unique to Archean time and provides evidence that primary abiotic silica precipitation indeed occurred in Archean oceans. Furthermore, the apparent early cementation of some granules indicates that the rate of silica precipitation was rapid under certain environmental conditions, which could provide insight into microfossil preservation via early silicification.

  19. Postmarketing Safety Surveillance and Reevaluation of Danhong Injection: Clinical Study of 30888 Cases.

    PubMed

    Li, Xue-Lin; Tang, Jin-Fa; Li, Wei-Xia; Li, Chun-Xiao; Zhao, Tao; Zhao, Bu-Chang; Wang, Yong; Zhang, Hui; Chen, Xiao-Fei; Xu, Tao; Zhu, Ming-Jun

    2015-01-01

    Traditional Chinese medicine injections (TCMIs) have played an irreplaceable role for treating some clinical emergency, severe illness, and infectious diseases in China. In recent years, the incidence rates of adverse drug reactions (ADRs) of TCMIs have increased year by year. Danhong injection (DHI) is one representative TCMI comprised of Danshen and Honghua for treating cardiovascular and cerebrovascular diseases in clinic. In present study, the postmarketing safety surveillance and reevaluation of DHI were reported. Total 30888 patients in 37 hospitals from 6 provinces participated in the study. The results showed that the ADR incidence rate of DHI was 3.50‰. Seventeen kinds of new adverse reactions of DHI were found. The main type of ADRs of DHI was type A (including sweating, dizziness, headache, flushing, vasodilation, eye hemorrhage, faintness, chest pain, palpitations, breathlessness, anxious, nausea, flatulence, vomiting, hypotension, hypertension, local numbness, dyspnea, joint disease, and tinnitus) accounting for 57.75%. The severities of most ADRs of DHI were mild and moderate reactions accounting for 25.93% and 66.67%, respectively. The main disposition of ADRs of DHI was drug withdrawal and without any treatments. The results can provide basis for amendment and improvement of the instructions of DHI, as well as demonstration and reference for the postmarketing safety surveillance and reevaluation of other TCMIs. And the rationality, scientificity, and safety of clinical applications of TCMIs could be improved.

  20. Reevaluation of the emergency planning zone for nuclear power plants in Taiwan using MACCS2 code.

    PubMed

    Wu, Jay; Yang, Yung-Muh; Chen, Ing-Jane; Chen, Huan-Tong; Chuang, Keh-Shih

    2006-04-01

    According to government regulations, the emergency planning zone (EPZ) of a nuclear power plant (NPP) must be designated before operation and reevaluated every 5 years. Corresponding emergency response planning (ERP) has to be made in advance to guarantee that all necessary resources are available under accidental releases of radioisotope. In this study, the EPZ for each of the three operating NPPs, Chinshan, Kuosheng, and Maanshan, in Taiwan was reevaluated using the MELCOR Accident Consequence Code System 2 (MACCS2) developed by Sandia National Laboratory. Meteorological data around the nuclear power plant were collected during 2003. The source term data including inventory, sensible heat content, and timing duration, were based on previous PRA information of each plant. The effective dose equivalent and thyroid dose together with the related individual risk and societal risk were calculated. By comparing the results to the protective action guide and related safety criteria, 1.5, 1.5, and 4.5km were estimated for Chinshan, Kuosheng, and Maanshan NPPs, respectively. We suggest that a radius of 5.0km is a reasonably conservative value of EPZ for each of the three operating NPPs in Taiwan. PMID:16376091

  1. Postmarketing Safety Surveillance and Reevaluation of Danhong Injection: Clinical Study of 30888 Cases

    PubMed Central

    Li, Xue-Lin; Tang, Jin-Fa; Li, Wei-Xia; Li, Chun-Xiao; Zhao, Tao; Zhao, Bu-Chang; Wang, Yong; Zhang, Hui; Chen, Xiao-Fei; Xu, Tao; Zhu, Ming-Jun

    2015-01-01

    Traditional Chinese medicine injections (TCMIs) have played an irreplaceable role for treating some clinical emergency, severe illness, and infectious diseases in China. In recent years, the incidence rates of adverse drug reactions (ADRs) of TCMIs have increased year by year. Danhong injection (DHI) is one representative TCMI comprised of Danshen and Honghua for treating cardiovascular and cerebrovascular diseases in clinic. In present study, the postmarketing safety surveillance and reevaluation of DHI were reported. Total 30888 patients in 37 hospitals from 6 provinces participated in the study. The results showed that the ADR incidence rate of DHI was 3.50‰. Seventeen kinds of new adverse reactions of DHI were found. The main type of ADRs of DHI was type A (including sweating, dizziness, headache, flushing, vasodilation, eye hemorrhage, faintness, chest pain, palpitations, breathlessness, anxious, nausea, flatulence, vomiting, hypotension, hypertension, local numbness, dyspnea, joint disease, and tinnitus) accounting for 57.75%. The severities of most ADRs of DHI were mild and moderate reactions accounting for 25.93% and 66.67%, respectively. The main disposition of ADRs of DHI was drug withdrawal and without any treatments. The results can provide basis for amendment and improvement of the instructions of DHI, as well as demonstration and reference for the postmarketing safety surveillance and reevaluation of other TCMIs. And the rationality, scientificity, and safety of clinical applications of TCMIs could be improved. PMID:26508981

  2. WISC-R stability and re-evaluation of learning-disabled students.

    PubMed

    Anderson, P L; Cronin, M E; Kazmierski, S

    1989-11-01

    This study investigated the temporal stability of WISC-R IQ scores for learning-disabled subjects (N = 113). All study subjects were administered the WISC-R for an initial evaluation (M age = 8 years, 3 months) and a follow-up re-evaluation (M age = 11 years, 7 months). Pearson product-moment correlations yielded coefficients that were considerably lower than those previously reported: r = .55, p less than .001 for the Verbal IQs; r = .63, p less than .001 for the Performance IQs; and r = .58, p less than .001 for the Full Scale IQs. Results of t-test analyses indicated that only the Verbal IQ scores were significantly different when the initial evaluation (M = 89.4) was compared to the re-evaluation (M = 85.3), p less than .001. The results suggest that the WISC-R may be less stable for the learning-disabled population than for other groups and that the average 3-year test-retest time lapse was an influential factor in the reduced reliability of this instrument.

  3. A quantitative method for silica flux evaluation

    NASA Astrophysics Data System (ADS)

    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.

  4. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    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.

  5. The comet assay with multiple mouse organs: comparison of comet assay results and carcinogenicity with 208 chemicals selected from the IARC monographs and U.S. NTP Carcinogenicity Database.

    PubMed

    Sasaki, Y F; Sekihashi, K; Izumiyama, F; Nishidate, E; Saga, A; Ishida, K; Tsuda, S

    2000-11-01

    The comet assay is a microgel electrophoresis technique for detecting DNA damage at the level of the single cell. When this technique is applied to detect genotoxicity in experimental animals, the most important advantage is that DNA lesions can be measured in any organ, regardless of the extent of mitotic activity. The purpose of this article is to summarize the in vivo genotoxicity in eight organs of the mouse of 208 chemicals selected from International Agency for Research on Cancer (IARC) Groups 1, 2A, 2B, 3, and 4, and from the U.S. National Toxicology Program (NTP) Carcinogenicity Database, and to discuss the utility of the comet assay in genetic toxicology. Alkylating agents, amides, aromatic amines, azo compounds, cyclic nitro compounds, hydrazines, halides having reactive halogens, and polycyclic aromatic hydrocarbons were chemicals showing high positive effects in this assay. The responses detected reflected the ability of this assay to detect the fragmentation of DNA molecules produced by DNA single strand breaks induced chemically and those derived from alkali-labile sites developed from alkylated bases and bulky base adducts. The mouse or rat organs exhibiting increased levels of DNA damage were not necessarily the target organs for carcinogenicity. It was rare, in contrast, for the target organs not to show DNA damage. Therefore, organ-specific genotoxicity was necessary but not sufficient for the prediction of organ-specific carcinogenicity. It would be expected that DNA crosslinkers would be difficult to detect by this assay, because of the resulting inhibition of DNA unwinding. The proportion of 10 DNA crosslinkers that was positive, however, was high in the gastrointestinal mucosa, stomach, and colon, but less than 50% in the liver and lung. It was interesting that the genotoxicity of DNA crosslinkers could be detected in the gastrointestinal organs even though the agents were administered intraperitoneally. Chemical carcinogens can be classified

  6. The formation of helical mesoporous silica nanotubes

    NASA Astrophysics Data System (ADS)

    Wan, Xiaobing; Pei, Xianfeng; Zhao, Huanyu; Chen, Yuanli; Guo, Yongmin; Li, Baozong; Hanabusa, Kenji; Yang, Yonggang

    2008-08-01

    Three chiral cationic gelators were synthesized. They can form translucent hydrogels in pure water. These hydrogels become highly viscous liquids under strong stirring. Mesoporous silica nanotubes with coiled pore channels in the walls were prepared using the self-assemblies of these gelators as templates. The mechanism of the formation of this hierarchical nanostructure was studied using transmission electron microscopy at different reaction times. The results indicated that there are some interactions between the silica source and the gelator. The morphologies of the self-assemblies of gelators changed gradually during the sol-gel transcription process. It seems that the silica source directed the organic self-assemblies into helical nanostructures.

  7. Nonporous Silica Nanoparticles for Nanomedicine Application

    PubMed Central

    Tang, Li; Cheng, Jianjun

    2013-01-01

    Summary Nanomedicine, the use of nanotechnology for biomedical applications, has potential to change the landscape of the diagnosis and therapy of many diseases. In the past several decades, the advancement in nanotechnology and material science has resulted in a large number of organic and inorganic nanomedicine platforms. Silica nanoparticles (NPs), which exhibit many unique properties, offer a promising drug delivery platform to realize the potential of nanomedicine. Mesoporous silica NPs have been extensively reviewed previously. Here we review the current state of the development and application of nonporous silica NPs for drug delivery and molecular imaging. PMID:23997809

  8. Fused Silica and Other Transparent Window Materials

    NASA Technical Reports Server (NTRS)

    Salem, Jon

    2016-01-01

    Several transparent ceramics, such as spinel and AlONs are now being produced in sufficient large areas to be used in space craft window applications. The work horse transparent material for space missions from Apollo to the International Space Station has been fused silica due in part to its low coefficient of expansion and optical quality. Despite its successful use, fused silica exhibits anomalies in its crack growth behavior, depending on environmental preconditioning and surface damage. This presentation will compare recent optical ceramics to fused silica and discuss sources of variation in slow crack growth behavior.

  9. Fluorine-Based DRIE of Fused Silica

    NASA Technical Reports Server (NTRS)

    Yee, Karl; Shcheglov, Kirill; Li, Jian; Choi, Daniel

    2007-01-01

    A process of deep reactive-ion etching (DRIE) using a fluorine-based gas mixture enhanced by induction-coupled plasma (ICP) has been demonstrated to be effective in forming high-aspect-ratio three-dimensional patterns in fused silica. The patterns are defined in part by an etch mask in the form of a thick, high-quality aluminum film. The process was developed to satisfy a need to fabricate high-aspect-ratio fused-silica resonators for vibratory microgyroscopes, and could be used to satisfy similar requirements for fabricating other fused-silica components.

  10. A reevaluation of the literature regarding the health assessment of diesel engine exhaust.

    PubMed

    Bunn, William B; Hesterberg, Thomas W; Valberg, Peter A; Slavin, Thomas J; Hart, Georgia; Lapin, Charles A

    2004-12-15

    While the International Agency for Research on Cancer (IARC) classified diesel exhaust (DE) as a"probable"carcinogen in 1989 based primarily on"sufficient"animal data, other investigators have since concluded that the lung tumors found in the rat studies were a result of particle overloading. Subsequent health risk assessments of DE have not used the rat cancer data. The U.S. Environmental Protection Agency (EPA), in developing its 2002 Health Assessment Document (HAD) for DE, primarily considered the epidemiology studies of railroad workers and truck drivers to develop health risk assessments of DE. However, both sets of epidemiology studies have serious weaknesses that make them unsuitable for cancer risk assessment. Major shortcomings were the lack of contemporaneous measurements of exposures to DE, difficulties with exposure history reconstruction, and adequately accounting for other exposures such as gasoline exhaust and cigarette smoke. To compound these problems, there was not, and there is still not, a specific exposure marker for DE. Interestingly, in the underground mining industry, where diesel exposures are much higher than observed in railroad workers and truck drivers, there was no increase in lung cancer. These problems and concerns led the U.S. EPA to conclude that while DE was a"likely"carcinogen, a unit risk value or range of risk cannot be calculated from existing data and that the risk could be zero. In addition, the DE emissions have changed and continue to change with the implementation of new emission control technologies. The HAD recognized this fact and noted that further studies are needed to assess new diesel engine emissions. Recent chemical characterization studies on low-emitting diesel engines with catalyzed particulate filters have shown emissions rates for several chemicals of concern that are even lower than comparable compressed natural gas (CNG)-fueled engines. With lower emissions, better fire safety, and improved cost

  11. Self-Assembled Silica Nanostructures: Simultaneous Discrimination of Handedness, Pitch and Diameter of Helical Silica Nanotubes.

    PubMed

    Oh, C Y; Kim, D Y; Jin, S M; Kim, T K; Kim, J P; Jeong, E D; Hyun, M H; Sim, E K; Lee, Y C; Jin, J S

    2016-02-01

    The left- and right-handed helical silica nanostructures were obtained with the aid of organic templates, the formation of the nanostructures might follow a co-operation self-assembly mechanism. The chirality of the organogel self-assemblies was successfully transcribed in to the silica. The helical pitch and pore size of the silica nanotubes sensitively depended on the optical purity of the neutral gelator in the reaction mixtures. PMID:27433714

  12. THE 2005 WORLD HEALTH ORGANIZATION RE-EVALUATION OF HUMAN AND MAMMALIAN TOXIC EQUIVALENCY FACTORS FOR DIOXINS AND DIOXIN-LIKE COMPOUNDS

    EPA Science Inventory

    In June 2005 a WHO-IPCS expert meeting was held in Geneva during which the toxic equivalency factors (TEFs) for dioxin like compounds, including some polychlorinated biphenyls (PCBs), were re-evaluated. For this re-evaluation process the refined TEF database recently published by...

  13. Reevaluated macroseismic map of the strongest Vrancea (Romania) earthquake occurred in 20th century

    NASA Astrophysics Data System (ADS)

    Pantea, Aurelian; Constantin, Angela

    2010-05-01

    In order to set the basis of some rigorous standards and norms of antiseismic design, capable of assuring maximum security to buildings, in accordance with the idea of promoting and developing a national system, compatible with the European standardizing systems, we initiated a very large research activity especially of reevaluating and harmonizing of the macroseismic maps of the significant earthquakes occurred on the Romanian territory. In this paper there have been reevaluated the macroseismic effects of the strongest vrancean earthquake occurred at 10th of November 1940. The reevaluating operation of the macroseismic data consisted in the reinterpretation of over 4500 macroseismic questionnaires, as well as the critical and serious research of the expertise reports, monographies, photos, scientific papers published both inside and outside the country regarding the severity of the macroseismic effects that were noticed "in situ" in the damaged areas. The increasing intensity of the macroseismic effects towards NNE in the case of the earthquake from the 10th of November 1940, was determined by the constructive interference of the cowaves produced by successive shocks. Only by admitting that the earthquake from the 10th of November 1940 was of a multishock type, we can explain the major macroseismic effects produced in Focsani, Odobesti, Marasesti, Panciu, Barlad, as well as in the areas from the neighborhood of the source where the seismic intensity exceeded the X (MCS) degree (Lopatari, Targu Bujor, Neculele). In all these places 70% from the houses have been completely destroyed, burying a great part of the inhabitants. Taking into consideration the geological and tectonic complexity, as well as the distribution of the seismic active areas on the Romanian territory and in the transborder areas that influence the seismicity, we considered that it is necessary, for a better graphic representation of the distribution of the macroseismic field generated by the

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

    PubMed

    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.

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

    PubMed

    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. PMID:17061888

  16. Procedure to prepare transparent silica gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G. (Inventor); Simpson, Norman R. (Inventor)

    1987-01-01

    This invention relates to the production of silica gels and in particular to a process for the preparation of silica gels which can be used as a crystal growth medium that simulates the convectionless environment of space to produce structurally perfect crystals. Modern utilizations of substances in electronics, such as radio transmitters and high frequency microphones, often require single crystals with controlled purity and structural perfection. The near convectionless environment of silica gel suppresses nucleation, thereby reducing the competitive nature of crystal growth. This competition limits the size and perfection of the crystal; and it is obviously desirable to suppress nucleation until, ideally, only one crystal grows in a predetermined location. A silica gel is not a completely convectionless environment like outer space, but is the closest known environment to that of outer space that can be created on Earth.

  17. Nanoparticle-doped radioluminescent silica optical fibers

    NASA Astrophysics Data System (ADS)

    Mrazek, J.; Nikl, M.; Kasik, I.; Podrazky, O.; Aubrecht, J.; Beitlerova, A.

    2014-05-01

    This contribution deals with the preparation and characterization of the silica optical fibers doped by nanocrystalline zinc silicate. The sol-gel approach was employed to prepare colloidal solution of zinc silicate precursors. Prepared sol was thermally treated to form nanocrystalline zinc silicate disperzed inside amorphous silica matrix or soaked inside the porous silica frit deposed inside the silica substrate tube which was collapsed into preform and drawn into optical fiber. Single mode optical fiber with the core diameter 15 μm and outer diamer 125 μm was prepared. Optical and waveguiding properties of the fiber were analyzed. Concentration of the zinc silicate in the fiber was 0.93 at. %. Radioluminescence properties of nanocrystalline zinc silicate powder and of the prepared optical fiber were investigated. The nanoparticle doped samples appear a emission maximum at 390 nm.

  18. Agmatine attenuates silica-induced pulmonary fibrosis.

    PubMed

    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 < 0.001) and reduced glutathione (p < 0.05) activities with significant decrease in the lung malondialdehyde (p < 0.001) content as compared to the silica group. Agmatine also reduced silica-induced overproduction of 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. Silica, silicosis and cancer. An international symposium

    SciTech Connect

    Not Available

    1984-01-01

    The research areas discussed in the symposium include: (1) history of silicosis and SiO/sub 2/ dust measurement; (2) silicosis: present and future; (3) recent epidemiologic research; (4) recent pathphysiology of SiO/sub 2/; (5) biologic and tumorigenic response to silica; (6) silica and cancer bioassays; (7) new standards; (8) future trends and pitfalls in SiO/sub 2/ research; (9) silicosis, dusty trades, and cancer; and (10) confounding and summarization.

  20. Silica Aerogel Captures Cosmic Dust Intact

    NASA Technical Reports Server (NTRS)

    Tsou, P.

    1994-01-01

    The mesostructure of silica aerogel resembles stings of grapes, ranging in size from 10 to 100 angstrom. This fine mesostructure transmits nearly 90 percent of incident light in the visible, while providing sufficiently gentle dissipation of the kinetric energy of hypervelocity cosmic dust particles to permit their intact capture. We introduced silica aerogel in 1987 as capture medium to take advantage of its low density, fine mesostruicture and most importantly, its transparency, allowing optical location of captured micron sized particles.

  1. Reevaluating the "subjective weathering" hypothesis: subjective aging, coping resources, and the stress process.

    PubMed

    Benson, Janel E

    2014-03-01

    The subjective weathering model contends that subjective aging is a key component of the stress process. This study reevaluates and extends this model by considering how adaptive capacities influence subjective aging and depressive symptoms in late adolescence and young adulthood. Using longitudinal data from the National Longitudinal Study of Adolescent Health (n = 7,230), I investigate how earlier stressors and coping resources contribute to older age identities (ages 18-22) and how these self-perceptions influence subsequent depressive symptoms (ages 25-29). The results show that subjective weathering alone does not lead to depressive symptoms; the critical issue is the level of psychosocial maturity that accompanies an older age identity. Those with high levels of psychosocial maturity, regardless of subjective age, were least likely to exhibit depressive symptoms. These results demonstrate that psychosocial maturity is an important adaptive resource that can shield young adults from the negative effects of "subjective weathering" or growing up fast.

  2. Re-Evaluating Sexual Violence Prevention Through Bystander Education: A Latent Growth Curve Approach.

    PubMed

    Shaw, Jessica; Janulis, Patrick

    2016-10-01

    Recently, there has been a call for more advanced analytic techniques in violence against women research, particularly in community interventions that use longitudinal designs. The current study re-evaluates experimental evaluation data from a sexual violence bystander intervention program. Using an exploratory latent growth curve approach, we were able to model the longitudinal growth trajectories of individual participants over the course of the entire study. Although the results largely confirm the original evaluation findings, the latent growth curve approach better fits the demands of "messy" data (e.g., missing data, varying number of time points per participant, and unequal time spacing within and between participants) that are frequently obtained during a community-based intervention. The benefits of modern statistical techniques to practitioners and researchers in the field of sexual violence prevention, and violence against women more generally, are further discussed.

  3. Antenatal Supervision—A Review of Obstetrical Care with Suggestions for Reevaluation

    PubMed Central

    Fox, Leon Parrish

    1964-01-01

    Studies by California Maternal Mortality Study Committees over a period of six years have revealed many avoidable inadequacies in the care of pregnant patients. Other reviews have shown a high incidence of non-fatal complications arising early in pregnancy when care is often inadequate. Since antenatal care is justly credited with the vast improvement of the incidence of maternal mortality, maternal morbidity and perinatal salvage, it is time for a reevaluation and upgrading of present-day practices. Responsibility is shared by the medical and auxiliary professions and the community. The public as well as those who care for the expectant mother must have improved educational exposure to achieve better results. PMID:14199085

  4. Reevaluation of the macroseismic effects of the 23 January 1838 Vrancea earthquake

    NASA Astrophysics Data System (ADS)

    Rogozea, M.; Marmureanu, Gh.; Radulian, M.

    2012-04-01

    The aim of this paper is to analyze the great event that occurred on 23 January 1838 (magnitude 7.5 in the Romanian catalogue). Valuable information has been collected from original or compiled historical sources, such as chronicles and manuscripts on that time, and related books and reports. The historical data are critically analyzed and, on the basis of our investigation, we showed the degree of significance of the earthquake parameters, as resulted from the effect distribution. The pattern of the intensity data points as reevaluated for this historical earthquake is compared with the pattern of instrumentally recorded major earthquake of 4 March 1977, the two events assumed to be similar as hypocenter location, source parameters and rupture propagation. We make also a comparative investigation for the attenuation relationship in case of Vrancea earthquakes, using historical data vs. instrumental data. Implications for the seismic hazard assessment are finally discussed.

  5. Gastric pseudolipomatosis, usual or unusual? Re-evaluation of 909 endoscopic gastric biopsies

    PubMed Central

    Alper, Murat; Akcan, Yusuf; Belenli, Olcay K; Çukur, Selma; Aksoy, Kamuran A; Suna, Mazlume

    2003-01-01

    Microvesicular pneumatosis intestinalis, also called “pseudolipomatosis” for resembling fatty infiltration, is characterized by the presence of small gas voids in the gastrointestinal wall, especially in mucosa. These voids are not lined with epithelia. There are few reported cases about colon, duodenum and skin. Because there is only one case report about pseudolipomatosis in the stomach, we re-evaluated 909 endoscopic biopsies taken from gastric corpus to check the presence of pseudolipomatosis. We determined pseudolipomatosis foci in 3 percent (n = 27) of biopsies. In two cases there were pseudolipomatosis foci in endoscopic biopsies having otherwise normal histologic findings, while there were pseudolipomatosis foci in endoscopic biopsies of 25 patients with gastritis. Helicobacter pylori was found in 85% of biopsies having pseudolipomatosis foci. In this study, we presented some histopathologic characteristics of pseudolipomatosis seen in gastric mucosa. PMID:14669349

  6. Grassy Silica Nanoribbons and Strong Blue Luminescence

    NASA Astrophysics Data System (ADS)

    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.

  7. Grassy Silica Nanoribbons and Strong Blue Luminescence

    PubMed Central

    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

  8. Synthesis of silica based porous nanomaterials

    NASA Astrophysics Data System (ADS)

    Mueller, Paul S.

    Silica is one of the most abundant elements on the planet, has flexible bonding properties and generally excellent stability. Because of these properties, silica has been a vital component in technologies ranging from ancient glassware to modern supercomputers. Silica is able to form a wide range of materials both alone and as a component of larger material frameworks. Porous silica based nanomaterials are rapidly growing in importance because of their many applications in a wide variety of fields. This thesis focuses on the synthesis of silica based porous nanomaterials: nanocrystalline zeolites, mesoporous silica nanoparticles, and iron oxide core/shell nanocomposites. The synthetic conditions of these materials were varied in order to maximize efficiency, minimize environmental impact, and produce high quality material with far reaching potential applications. The materials were characterized by physicochemical techniques including Transmission Electron Microscopy, Dynamic Light Scattering, Powder X-Ray Diffraction, Solid State NMR, and Nitrogen Adsorption Isotherms. The materials were evaluated and conditions were controlled to produce high yields of quality nanomaterials and hypothesize methods for further synthetic control. The products will be used in studies involving nanoparticle toxicity, environmental remediation, and drug delivery.

  9. Re-evaluation of Non-regulatory Asbestos Group Minerals for Regulatory Agencies

    NASA Astrophysics Data System (ADS)

    Dogan, M.; Dogan, A.

    2013-05-01

    There are established rules and regulations for some asbestos group minerals - amphibole group minerals of actinolite, amosite, anthophyllite, crocidolite, tremolite; and serpentine group minerals of chrysotile- called "regulatory". There are also "non-regulatory" naturally occurring asbestos (NOA) group minerals as constituent of rocks and soil, including richterite, winchite, fluoro-edenite, balangeroite, carlosturanite, gageite, arfvedsonite, and magnesio-arfvedsonite. Strong evidences for carcinogenicity of these NOA minerals in later cohorts of cancer patients demonstrated the risks associated with these minerals. In addition, although the chrysotile asbestos regulated by some organizations such as WHO, World Trade Organization, United Nations, US EPA, International Labour Organization, and EU Countries; however, controversies still continue surrounding the use of chrysotile. Determinations of polymineralic fibrous veins, mixed particles, amphibole cleavage fragments, and genetic predisposition are also important issues (i.e. Dogan et al., 2006).Therefore, accurate characterizations of chemical composition, morphology, structure, and defects are necessary in order to find out mechanism(s) of carcinogenicity of all asbestos group minerals. Calculation methods of chemical composition are still under debate because of assumption of no vacancies at any sites and intergrowth of minerals. Substitution(s) may cause deviations from the ideal chemical formula and wide variations in chemical compositions. Detail morphological and chemical quantification of individual asbestos group minerals in micro- and nano-scale may help to evaluate its true carcinogenetic mechanism(s), and consequently prevention and possibly treatment of related diseases. we propose that nonregulatory asbestos minerals and the chrysotile should be re-evaluated. The amount of fibers inhaled, in terms of weight percent and number, need also be re-evaluated by mineralogists. Finally, Regulatory

  10. 41 CFR 301-70.602 - How often must we reevaluate the payment of transportation and subsistence expenses to a...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 4 2010-07-01 2010-07-01 false How often must we reevaluate the payment of transportation and subsistence expenses to a threatened law enforcement/investigative employee? 301-70.602 Section 301-70.602 Public Contracts and Property Management Federal...

  11. Re-evaluation of broiler carcass scalding protocols for impact on the recovery of Campylobacter from breast skin after defeathering

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This research re-evaluated the impact of scalding protocols on the recovery of Campylobacter from breast skin following defeathering after preliminary processing trials detected Campylobacter from breast skin for 4/8 carcasses that had vents plugged and sutured prior to scalding. Published research...

  12. Transport of colloidal silica in unsaturated sand: Effect of charging properties of sand and silica particles.

    PubMed

    Fujita, Yosuke; Kobayashi, Motoyoshi

    2016-07-01

    We have studied the transport of colloidal silica in various degrees of a water-saturated Toyoura sand column, because silica particles are widely used as catalyst carriers and abrasive agents, and their toxicity is reported recently. Since water-silica, water-sand, and air-water interfaces have pH-dependent negative charges, the magnitude of surface charge was controlled by changing the solution pH. The results show that, at high pH conditions (pH 7.4), the deposition of colloidal silica to the sand surface is interrupted and the silica concentration at the column outlet immediately reaches the input concentration in saturated conditions. In addition, the relative concentration of silica at the column outlet only slightly decreases to 0.9 with decreasing degrees of water saturation to 38%, because silica particles are trapped in straining regions in the soil pore and air-water interface. On the other hand, at pH 5 conditions (low pH), where sand and colloid have less charge, reduced repulsive forces result in colloidal silica attaching onto the sand in saturated conditions. The deposition amount of silica particles remarkably increases with decreasing degrees of water saturation to 37%, which is explained by more particles being retained in the sand column associated with the air-water interface. In conclusion, at higher pH, the mobility of silica particles is high, and the air-water interface is inactive for the deposition of silica. On the other hand, at low pH, the deposition amount increases with decreasing water saturation, and the particle transport is inhibited. PMID:27045635

  13. Silica ecosystem for synergistic biotransformation

    PubMed Central

    Mutlu, Baris R.; Sakkos, Jonathan K.; Yeom, Sujin; Wackett, Lawrence P.; Aksan, Alptekin

    2016-01-01

    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. PMID:27264916

  14. Silica ecosystem for synergistic biotransformation.

    PubMed

    Mutlu, Baris R; Sakkos, Jonathan K; Yeom, Sujin; Wackett, Lawrence P; Aksan, Alptekin

    2016-01-01

    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. PMID:27264916

  15. Silica ecosystem for synergistic biotransformation

    NASA Astrophysics Data System (ADS)

    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.

  16. Silica-metal core-shell nanostructures.

    PubMed

    Jankiewicz, B J; Jamiola, D; Choma, J; Jaroniec, M

    2012-01-15

    Silica-metal nanostructures consisting of silica cores and metal nanoshells attract a lot of attention because of their unique properties and potential applications ranging from catalysis and biosensing to optical devices and medicine. The important feature of these nanostructures is the possibility of controlling their properties by the variation of their geometry, shell morphology and shell material. This review is devoted to silica-noble metal core-shell nanostructures; specifically, it outlines the main methods used for the preparation and surface modification of silica particles and presents the major strategies for the formation of metal nanoshells on the modified silica particles. A special emphasis is given to the Stöber method, which is relatively simple, effective and well verified for the synthesis of large and highly uniform silica particles (with diameters from 100 nm to a few microns). Next, the surface chemistry of these particles is discussed with a special focus on the attachment of specific organic groups such as aminopropyl or mercaptopropyl groups, which interact strongly with metal species. Finally, the synthesis, characterization and application of various silica-metal core-shell nanostructures are reviewed, especially in relation to the siliceous cores with gold or silver nanoshells. Nowadays, gold is most often used metal for the formation of nanoshells due to its beneficial properties for many applications. However, other metals such as silver, platinum, palladium, nickel and copper were also used for fabrication of core-shell nanostructures. Silica-metal nanostructures can be prepared using various methods, for instance, (i) growth of metal nanoshells on the siliceous cores with deposited metal nanoparticles, (ii) reduction of metal species accompanied by precipitation of metal nanoparticles on the modified silica cores, and (iii) formation of metal nanoshells under ultrasonic conditions. A special emphasis is given to the seed

  17. Thermal waters along the Konocti Bay fault zone, Lake County, California: a re-evaluation

    USGS Publications Warehouse

    Thompson, J.M.; Mariner, R.H.; White, L.D.; Presser, T.S.; Evans, William C.

    1992-01-01

    The Konocti Bay fault zone (KBFZ), initially regarded by some as a promising target for liquid-dominated geothermal systems, has been a disappointment. At least five exploratory wells were drilled in the vicinity of the KBFZ, but none were successful. Although the Na-K-Ca and Na-Li geothermometers indicate that the thermal waters discharging in the vicinity of Howard and Seigler Springs may have equilibrated at temperatures greater than 200??C, the spring temperatures and fluid discharges are low. Most thermal waters along the KBFZ contain >100 mg/l Mg. High concentrations of dissolved magnesium are usually indicative of relatively cool hydrothermal systems. Dissolution of serpentine at shallow depths may contribute dissolved silica and magnesium to rising thermal waters. Most thermal waters are saturated with respect to amorphous silica at the measured spring temperature. Silica geothermometers and mixing models are useless because the dissolved silica concentration is not controlled by the solubility of either quartz or chalcedony. Cation geothermometry indicates the possibility of a high-temperature fluid (> 200??C) only in the vicinity of Howard and Seigler Springs. However, even if the fluid temperature is as high as that indicated by the geothermometers, the permeability may be low. Deuterium and oxygen-18 values of the thermal waters indicate that they recharged locally and became enriched in oxygen-18 by exchange with rock. Diluting meteoric water and the thermal water appear to have the same deuterium value. Lack of tritium in the diluted spring waters suggest that the diluting water is old. ?? 1992.

  18. Synthesis of ultrabright nanoporous fluorescent silica discoids using an inorganic silica precursor

    NASA Astrophysics Data System (ADS)

    Volkov, Dmytro O.; Cho, Eun-Bum; Sokolov, Igor

    2011-05-01

    The templated sol-gel synthesis of ultrabright fluorescent nanoporous silica particles based on the use of organic silica sources has previously been reported. The use of organosilanes as the main silica precursors has a number of issues, in particular, the low robustness of the synthesis due to instability of the organic silica source. Here we report on a novel synthesis of ultrabright fluorescent nanoporous silica discoids (a specific shape in-between the sphere and disk) of 3.1 +/- 0.7 microns in size, which were prepared using a stable inorganic sodium silicate silica source. Organic fluorescent dye Rhodamine 6G (R6G) was physically (non-covalently) entrapped inside cylindrical nanochannels of ~4-5 nm in diameter. In contrast to the synthesis with organic silica precursors, the obtained particles showed an excessive leakage of dye. To prevent this leakage, we modified the synthesis by adding a small amount of a secondary silica source. The synthesized particles show virtually no leakage, high photostability, and a brightness equivalent to the fluorescence of up to 7 × 107 free R6G molecules. This is about 7 times higher than the fluorescent brightness of particles of the same size made of CdSe/ZnS quantum dots, and 420 times higher than the brightness of the same volume of aqueous solution of free R6G dye.

  19. The Management of Silica in Los Alamos National Laboratory Tap Water - A Study of Silica Solubility

    SciTech Connect

    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.

  20. Hard magnetism in structurally engineered silica nanocomposite.

    PubMed

    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. PMID:27537252

  1. Hard magnetism in structurally engineered silica nanocomposite.

    PubMed

    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.

  2. Native silica nanoparticles are powerful membrane disruptors.

    PubMed

    Alkhammash, Hend I; Li, Nan; Berthier, Rémy; de Planque, Maurits R R

    2015-06-28

    Silica nanoparticles are under development for intracellular drug delivery applications but can also have cytotoxic effects including cell membrane damage. In this study, we investigated the interactions of silica nanospheres of different size, surface chemistry and biocoating with membranes of phosphatidylcholine lipids. In liposome leakage assays many, but not all, of these nanoparticles induced dose-dependent dye leakage, indicative of membrane perturbation. It was found that 200 and 500 nm native-silica, aminated and carboxylated nanospheres induce near-total dye release from zwitterionic phosphatidylcholine liposomes at a particle/liposome ratio of ∼1, regardless of their surface chemistry, which we interpret as particle-supported bilayer formation following a global rearrangement of the vesicular membrane. In contrast, 50 nm diameter native-silica nanospheres did not induce total dye leakage below a particle/liposome ratio of ∼8, whereas amination or carboxylation, respectively, strongly reduced or prevented dye release. We postulate that for the smaller nanospheres, strong silica-bilayer interactions are manifested as bilayer engulfment of membrane-adsorbed particles, with localized lipid depletion eventually leading to collapse of the vesicular membrane. Protein coating of the particles considerably reduced dye leakage and lipid bilayer coating prevented dye release all together, while the inclusion of 33% anionic lipids in the liposomes reduced dye leakage for both native-silica and aminated surfaces. These results, which are compared with the effect of polystyrene nanoparticles and other engineered nanomaterials on lipid bilayers, and which are discussed in relation to nanosilica-induced cell membrane damage and cytotoxicity, indicate that a native-silica nanoparticle surface chemistry is a particularly strong membrane interaction motif.

  3. Synthesis and Characterization of Bionanoparticle-Silica Composites and Mesoporous Silica with Large Pores

    SciTech Connect

    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.

  4. Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

    PubMed

    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. PMID:27433652

  5. Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

    PubMed

    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.

  6. Subsurface defect characterization and laser-induced damage performance of fused silica optics polished with colloidal silica and ceria

    NASA Astrophysics Data System (ADS)

    Xiang, He; Gang, Wang; Heng, Zhao; Ping, Ma

    2016-04-01

    This paper mainly focuses on the influence of colloidal silica polishing on the damage performance of fused silica optics. In this paper, nanometer sized colloidal silica and micron sized ceria are used to polish fused silica optics. The colloidal silica polished samples and ceria polished samples exhibit that the root-mean-squared (RMS) average surface roughness values are 0.7 nm and 1.0 nm, respectively. The subsurface defects and damage performance of the polished optics are analyzed and discussed. It is revealed that colloidal silica polishing will introduce much fewer absorptive contaminant elements and subsurface damages especially no trailing indentation fracture. The 355-nm laser damage test reveals that each of the fused silica samples polished with colloidal silica has a much higher damage threshold and lower damage density than ceria polished samples. Colloidal silica polishing is potential in manufacturing high power laser optics.

  7. Generation of crystalline silica from sugarcane burning.

    PubMed

    Le Blond, Jennifer S; Horwell, Claire J; Williamson, Ben J; Oppenheimer, Clive

    2010-07-01

    Sugarcane leaves contain amorphous silica, which may crystallise to form crystalline silica polymorphs (cristobalite or quartz), during commercial sugarcane harvesting where sugarcane plants are burned. Respirable airborne particulate containing these phases may present an occupational health hazard. Following from an earlier pilot study (J. S. Le Blond, B. J. Williamson, C. J. Horwell, A. K. Monro, C. A. Kirk and C. Oppenheimer, Atmos. Environ., 2008, 42, 5558-5565) in which experimental burning of sugarcane leaves yielded crystalline silica, here we report on actual conditions during sugarcane burning on commercial estates, investigate the physico-chemical properties of the cultivated leaves and ash products, and quantify the presence of crystalline silica. Commercially grown raw sugarcane leaf was found to contain up to 1.8 wt% silica, mostly in the form of amorphous silica bodies (with trace impurities e.g., Al, Na, Mg), with only a small amount of quartz. Thermal images taken during several pre-harvest burns recorded temperatures up to 1056 degrees C, which is sufficient for metastable cristobalite formation. No crystalline silica was detected in airborne particulate from pre-harvest burning, collected using a cascade impactor. The sugarcane trash ash formed after pre-harvest burning contained between 10 and 25 wt% SiO(2), mostly in an amorphous form, but with up to 3.5 wt% quartz. Both quartz and cristobalite were identified in the sugarcane bagasse ash (5-15 wt% and 1-3 wt%, respectively) formed in the processing factory. Electron microprobe analysis showed trace impurities of Mg, Al and Fe in the silica particles in the ash. The absence of crystalline silica in the airborne emissions and lack of cristobalite in trash ash suggest that high temperatures during pre-harvest burning were not sustained long enough for cristobalite to form, which is supported by the presence of low temperature sylvite and calcite in the residual ash. The occurrence of quartz and

  8. Generation of crystalline silica from sugarcane burning.

    PubMed

    Le Blond, Jennifer S; Horwell, Claire J; Williamson, Ben J; Oppenheimer, Clive

    2010-07-01

    Sugarcane leaves contain amorphous silica, which may crystallise to form crystalline silica polymorphs (cristobalite or quartz), during commercial sugarcane harvesting where sugarcane plants are burned. Respirable airborne particulate containing these phases may present an occupational health hazard. Following from an earlier pilot study (J. S. Le Blond, B. J. Williamson, C. J. Horwell, A. K. Monro, C. A. Kirk and C. Oppenheimer, Atmos. Environ., 2008, 42, 5558-5565) in which experimental burning of sugarcane leaves yielded crystalline silica, here we report on actual conditions during sugarcane burning on commercial estates, investigate the physico-chemical properties of the cultivated leaves and ash products, and quantify the presence of crystalline silica. Commercially grown raw sugarcane leaf was found to contain up to 1.8 wt% silica, mostly in the form of amorphous silica bodies (with trace impurities e.g., Al, Na, Mg), with only a small amount of quartz. Thermal images taken during several pre-harvest burns recorded temperatures up to 1056 degrees C, which is sufficient for metastable cristobalite formation. No crystalline silica was detected in airborne particulate from pre-harvest burning, collected using a cascade impactor. The sugarcane trash ash formed after pre-harvest burning contained between 10 and 25 wt% SiO(2), mostly in an amorphous form, but with up to 3.5 wt% quartz. Both quartz and cristobalite were identified in the sugarcane bagasse ash (5-15 wt% and 1-3 wt%, respectively) formed in the processing factory. Electron microprobe analysis showed trace impurities of Mg, Al and Fe in the silica particles in the ash. The absence of crystalline silica in the airborne emissions and lack of cristobalite in trash ash suggest that high temperatures during pre-harvest burning were not sustained long enough for cristobalite to form, which is supported by the presence of low temperature sylvite and calcite in the residual ash. The occurrence of quartz and

  9. Silica-Rich Soil Found by Spirit

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA's Mars Exploration Rover Spirit has found a patch of bright-toned soil so rich in silica that scientists propose water must have been involved in concentrating it.

    The silica-rich patch, informally named 'Gertrude Weise' after a player in the All-American Girls Professional Baseball League, was exposed when Spirit drove over it during the 1,150th Martian day, or sol, of Spirit's Mars surface mission (March 29, 2007). One of Spirit's six wheels no longer rotates, so it leaves a deep track as it drags through soil. Most patches of disturbed, bright soil that Spirit had investigated previously are rich in sulfur, but this one has very little sulfur and is about 90 percent silica.

    This image is a approximately true-color composite of three images taken through different filters by Spirit's panoramic camera on Sol 1,187 (May 6). The track of disturbed soil is roughly 20 centimeters (8 inches) wide.

    Spirit's miniature thermal emission spectrometer, which can assess a target's mineral composition from a distance, examined the Gertrude Weise patch on Sol 1,172 (April 20). The indications it found for silica in the overturned soil prompted a decision to drive Spirit close enough to touch the soil with the alpha particle X-ray spectrometer, a chemical analyzer at the end of Spirit's robotic arm. The alpha particle X-ray spectrometer collected data about this target on sols 1,189 and 1,190 (May 8 and May 9) and produced the finding of approximately 90 percent silica.

    Silica is silicon dioxide. On Earth, it commonly occurs as the crystalline mineral quartz and is the main ingredient in window glass. The Martian silica at Gertrude Weise is non-crystalline, with no detectable quartz.

    In most cases, water is required to produce such a concentrated deposit of silica, according to members of the rover science team. One possible origin for the silica could have been interaction of soil with acidic steam produced by volcanic activity. Another could

  10. Silica-Rich Soil in Gusev Crater

    NASA Technical Reports Server (NTRS)

    2007-01-01

    NASA's Mars Exploration Rover Spirit has found a patch of bright-toned soil so rich in silica that scientists propose water must have been involved in concentrating it.

    The silica-rich patch, informally named 'Gertrude Weise' after a player in the All-American Girls Professional Baseball League, was exposed when Spirit drove over it during the 1,150th Martian day, or sol, of Spirit's Mars surface mission (March 29, 2007). One of Spirit's six wheels no longer rotates, so it leaves a deep track as it drags through soil. Most patches of disturbed, bright soil that Spirit had investigated previously are rich in sulfur, but this one has very little sulfur and is about 90 percent silica.

    Spirit's panoramic camera imaged the bright patch through various filters on Sol 1,158 (April 6). This approximately true-color image combines images taken through three different filters. The track of disturbed soil is roughly 20 centimeters (8 inches) wide.

    Spirit's miniature thermal emission spectrometer, which can assess a target's mineral composition from a distance, examined the Gertrude Weise patch on Sol 1,172 (April 20). The indications it found for silica in the overturned soil prompted a decision to drive Spirit close enough to touch the soil with the alpha particle X-ray spectrometer, a chemical analyzer at the end of Spirit's robotic arm. The alpha particle X-ray spectrometer collected data about this target on sols 1,189 and 1,190 (May 8 and May 9) and produced the finding of approximately 90 percent silica.

    Silica is silicon dioxide. On Earth, it commonly occurs as the crystalline mineral quartz and is the main ingredient in window glass. The Martian silica at Gertrude Weise is non-crystalline, with no detectable quartz.

    In most cases, water is required to produce such a concentrated deposit of silica, according to members of the rover science team. One possible origin for the silica could have been interaction of soil with acidic steam

  11. Silica Synthesis by Sponges: Unanticipated Molecular Mechanism

    NASA Astrophysics Data System (ADS)

    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

  12. Chitosan-silica hybrid porous membranes.

    PubMed

    Pandis, Christos; Madeira, Sara; Matos, Joana; Kyritsis, Apostolos; Mano, João F; Ribelles, José Luis Gómez

    2014-09-01

    Chitosan-silica porous hybrids were prepared by a novel strategy in order to improve the mechanical properties of chitosan (CHT) in the hydrogel state. The inorganic silica phase was introduced by sol-gel reactions in acidic medium inside the pores of already prepared porous scaffolds. In order to make the scaffolds insoluble in acidic media chitosan was cross-linked by genipin (GEN) with an optimum GEN concentration of 3.2 wt.%. Sol-gel reactions took place with Tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) acting as silica precursors. GPTMS served also as a coupling agent between the free amino groups of chitosan and the silica network. The morphology study of the composite revealed that the silica phase appears as a layer covering the chitosan membrane pore walls. The mechanical properties of the hybrids were characterized by means of compressive stress-strain measurements. By immersion in water the hybrids exhibit an increase in elastic modulus up to two orders of magnitude. PMID:25063153

  13. Organosiloxane reactivity on dehydroxylated silica surfaces

    SciTech Connect

    Grabbe, A.; Michalske, T.A.

    1995-12-31

    In most cases, the surface reactivity of silica glass is controlled by the presence of silanol groups. However, glass surfaces that are produced by high temperature forming processes possess little if any silanol groups. Previous work demonstrated that the reactivity of glass surfaces formed at high temperature is controlled by the existence of strained siloxane rings. In this study, the authors conducted experiments on highly dehydroxylated silica powder surfaces and silica surfaces that were formed directly from the melt to explore the reactivity of strained siloxane rings with various organosiloxanes reactants. The authors use infrared spectrometry to show that strained dimer rings react with organosiloxane molecules or with water at comparable rates, depending on the structure of the organosiloxane. The data indicate that the important features of the reacting molecule are its polarity, steric accessibility and bond strain. Since the measured reactions require approximately six orders of magnitude of gas exposure to go from 1% to 99% completion, these data present strong evidence that the surface is highly heterogeneous. By applying a linear distribution of activation energies, the authors estimate that spread in activation energy to be approximately 40 kJ/mole. In this presentation, the authors discuss the implications of this newly discovered silica chemistry for novel approaches to tailor melt-formed surfaces for improved polymer adhesion and hydrolytic stability. They will also discuss efforts to prepare true melt-formed surfaces by blowing bubbles of silica in a vacuum environment.

  14. Numerical studies of silica precipitation/dissolution

    SciTech Connect

    Lai, C.H.; Bodvarsson, G.S.; Witherspoon, P.A.

    1985-01-01

    In this paper we describe our numerical simulator PIC (pressure-temperature-chemistry), and also present the methods we use to reduce error due to numerical diffusion. Examples of the application of this approach to two problems are included. The first problem involves non-isothermal flow of supersaturated silica through single fractures. The precipitation of silica in the fractures is modeled and the resulting permeability and flow rate decreases are calculated. The second problem involves field data collected at the Ellidaar geothermal field in Iceland. After 15 years of fluid production, significant declines in pressure and temperature have been observed along with changes in silica concentrations. In order to illustrate the applicability of our model to such data, we have developed a simple numerical model that fits well with the observed production history. The applicability of our coupled method of analyzing the changing reservoir conditions is demonstrated, and the result is a more detailed understanding of the geothermal system.

  15. Fused silica windows for solar receiver applications

    NASA Astrophysics Data System (ADS)

    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.

  16. Electroactive Silica Nanoparticles for Biological Labeling

    SciTech Connect

    Wang, Jun; Liu, Guodong; Lin, Yuehe

    2006-08-29

    A novel electrochemical immuno-biosensor based on poly(guanine)-functionalized silica nanoparticle labels and mediator-generated catalytic reaction was described. The functionalized silica NPs conjugates were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemistry. This immunobiosensor is very sensitive and the limit of detection was found to be down to 0.2 ng/ml (4 pM), which was attributed to signal amplification by poly[G] functionalized silica NPs and guanine catalytic oxidation. Attractive feature of this approach is feasible to develop a cheap, sensitive and portable device for multiplexed diagnoses of different proteins. This method is simple, selective and reproducible for trace protein analysis and can be extended to study protein/protein, peptide/protein, and DNA/ protein interactions.

  17. Crystalline silica: Old problem, new problem

    SciTech Connect

    Burst, J.F. )

    1993-03-01

    Known as an industrial health hazard for centuries, crystalline silica has recently gained enhanced recognition as a threat to human health by being classified as a 2A probable carcinogen'' by The International Agency for Research on Cancer. Its maximum allowable concentration as an impurity is established as 0.1%. This has led to consternation in the mining and mineral industries inasmuch as the accuracy of methodology available to measure crystalline silica content at this level in heterogeneous matrices has been severely questioned and unlabeled products distributed with crystalline silica contents in excess of 0.1% are considered in violation of the Hazard Communication Standard. Three problems exist: (1) defining acceptable reference standards; (2) establishing adequate measurement procedures; (3) marketing products in compliance with State and Federal regulations. A review and update of these problems has been developed for the guidance of quarry operators and mineral product manufacturers.

  18. High purity silica reflective heat shield development

    NASA Technical Reports Server (NTRS)

    Nachtscheim, P. R.; Blome, J. C.

    1976-01-01

    A hyperpure vitreous silica material is being developed for use as a reflective and ablative heat shield for planetary entry. Various purity grades and forms of raw materials were evaluated along with various processing methods. Slip casting of high purity grain was selected as the best processing method, resulting in a highly reflective material in the wavelength bands of interest (the visible and ultraviolet regions). The selected material was characterized with respect to optical, mechanical and physical properties using a limited number of specimens. The process has been scaled up to produce a one-half scale heat shield (18 in. dia.) (45.72 cm) for a Jupiter entry vehicle. This work is now being extended to improve the structural safety factor of the heat shield by making hyperpure silica material tougher through the addition of silica fibers.

  19. Enthalpy of formation of amorphous silica

    SciTech Connect

    Klyuchnikov, V.A.; Voronkov, M.G.; Landa, L.M.; Pepekin, V.I.; Tikhenko, T.M.; Shvets, G.N.; Popov, V.T.

    1987-07-01

    In calculating the formation heat of organosilicon compounds from the results of their combustion heat on oxygen it is necessary to have a reliable value of the standard formation heat of hydrated silica. This paper, in trying to assess this property, examines the following factors: the character of the surface, the structure and specific concentration of surface silicon hydroxide groups, and the energy of its wetting with water. Combustion experiments are carried out and described. It is concluded that the formation heat of amorphous silica is not a constant value and is determined by the character of its surface and degree of hydration. For this reason, in the combustion of organosilicon compounds, the formation heat of silica should be determined experimentally.

  20. Tracer diffusion in silica inverse opals.

    PubMed

    Cherdhirankorn, Thipphaya; Retsch, Markus; Jonas, Ulrich; Butt, Hans-Juergen; Koynov, Kaloian

    2010-06-15

    We employed fluorescence correlation spectroscopy (FCS) to study the diffusion of small fluorescence tracers in liquid filled silica inverse opals. The inverse opals consisted of a nanoporous silica scaffold spanning a hexagonal crystal of spherical voids of 360 nm diameter connected by circular pores of 70 nm diameter. The diffusion of Alexa Fluor 488 in water and of perylene-3,4,9,10-tetracarboxylic diimide (PDI) in toluene was studied. Three diffusion modes could be distinguished: (1) Free diffusion limited by the geometric constraints given by the inverse opal, where, as compared to the free solution, this diffusion is slowed down by a factor of 3-4, (2) slow diffusion inside the nanoporous matrix of the silica scaffold, and (3) diffusion limited by adsorption. On the length scale of the focus of a confocal microscope of roughly 400 nm diffusion was non-Fickian in all cases.

  1. Surface treatment of silica nanoparticles for stable and charge-controlled colloidal silica

    PubMed Central

    Kim, Kyoung-Min; Kim, Hye Min; Lee, Won-Jae; Lee, Chang-Woo; Kim, Tae-il; Lee, Jong-Kwon; Jeong, Jayoung; Paek, Seung-Min; Oh, Jae-Min

    2014-01-01

    An attempt was made to control the surface charge of colloidal silica nanoparticles with 20 nm and 100 nm diameters. Untreated silica nanoparticles were determined to be highly negatively charged and have stable hydrodynamic sizes in a wide pH range. To change the surface to a positively charged form, various coating agents, such as amine containing molecules, multivalent metal cation, or amino acids, were used to treat the colloidal silica nanoparticles. Molecules with chelating amine sites were determined to have high affinity with the silica surface to make agglomerations or gel-like networks. Amino acid coatings resulted in relatively stable silica colloids with a modified surface charge. Three amino acid moiety coatings (L-serine, L-histidine, and L-arginine) exhibited surface charge modifying efficacy of L-histidine > L-arginine > L-serine and hydrodynamic size preservation efficacy of L-serine > L-arginine > L-histidine. The time dependent change in L-arginine coated colloidal silica was investigated by measuring the pattern of the backscattered light in a Turbiscan™. The results indicated that both the 20 nm and 100 nm L-arginine coated silica samples were fairly stable in terms of colloidal homogeneity, showing only slight coalescence and sedimentation. PMID:25565824

  2. Interfacial interaction between the epoxidized natural rubber and silica in natural rubber/silica composites

    NASA Astrophysics Data System (ADS)

    Xu, Tiwen; Jia, Zhixin; Luo, Yuanfang; Jia, Demin; Peng, Zheng

    2015-02-01

    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.

  3. Surfactant removal and silica condensation during the photochemical calcination of thin film silica mesophases.

    PubMed

    Dattelbaum, Andrew M; Amweg, Meri L; Ruiz, Julia D; Ecke, Laurel E; Shreve, Andrew P; Parikh, Atul N

    2005-08-01

    The evolution of photochemical surfactant removal and silica condensation from organically templated thin film silica nanocomposites with mesoscopic ordering has been probed using a combined application of Fourier transform infrared (FT-IR) spectroscopy and single wavelength ellipsometry. Thin films of silica nanocomposites were prepared by a previously reported evaporation-induced self-assembly process. Specifically, oxidized silicon and gold substrates were withdrawn at 25 mm/min from a subcritical micelle concentration solution containing an ethylene oxide surfactant as a structure-directing agent and tetraethyl orthosilicate as a silica precursor. Real-time grazing incidence difference FT-IR spectra of the nanocomposite films on gold taken during exposure to short-wavelength ultraviolet light (184-257 nm) show that surfactant removal and silica condensation occur gradually and concomitantly. Surfactant removal and silica reconstructions were found to be nearly complete after 90 min of exposure. Further, a transient feature was observed in the FT-IR spectra around 1713 cm(-1) during the UV exposure process and was assigned to a carbonyl (C=O) stretching mode absorption, reflecting the transient formation of a partially oxidized surfactant intermediate. From these data we propose a stepwise model for surfactant removal from the nanocomposite films. Ellipsometrically determined index of refraction values collected as a function of UV exposure are also shown to support such a stepwise mechanism of surfactant removal from the ordered nanocomposite silica thin film mesophases studied here. PMID:16852834

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

    PubMed

    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 (<200 m(2)/g at 600 °C) at high temperatures combined with the simple method makes the silica-titania aerogels promising candidates as photocatalysts.

  5. Stimuli-responsive polyaniline coated silica microspheres and their electrorheology

    NASA Astrophysics Data System (ADS)

    Park, Dae Eun; Choi, Hyoung Jin; Vu, Cuong Manh

    2016-05-01

    Silica/polyaniline (PANI) core–shell structured microspheres were synthesized by coating the surface of silica micro-beads with PANI and applied as a candidate inorganic/polymer composite electrorheological (ER) material. The silica micro-beads were initially modified using N-[(3-trimethoxysilyl)-propyl] aniline to activate an aniline functional group on the silica surface for a better PANI coating. The morphology of the PANI coating on the silica surface was examined by scanning electron microscopy and the silica/PANI core–shell structure was confirmed by transmission electron microscopy. The chemical structure of the particles was confirmed by Fourier transform infrared spectroscopy. Rotational rheometry was performed to confirm the difference in the ER properties between pure silica and silica/PANI microsphere-based ER fluids when dispersed in silicone oil.

  6. Synthesis of very small diameter silica nanofibers using sound waves.

    PubMed

    Datskos, Panos; Chen, Jihua; Sharma, Jaswinder

    2014-07-14

    Silica nanofibers of an average diameter ≈30 nm and length ≈100 μm have been synthesized using an unprecedented strategy: sound waves. A new phenomenon, spinning off the nanofibers at silica rod tips, is also observed.

  7. Stimuli-responsive polyaniline coated silica microspheres and their electrorheology

    NASA Astrophysics Data System (ADS)

    Park, Dae Eun; Choi, Hyoung Jin; Vu, Cuong Manh

    2016-05-01

    Silica/polyaniline (PANI) core-shell structured microspheres were synthesized by coating the surface of silica micro-beads with PANI and applied as a candidate inorganic/polymer composite electrorheological (ER) material. The silica micro-beads were initially modified using N-[(3-trimethoxysilyl)-propyl] aniline to activate an aniline functional group on the silica surface for a better PANI coating. The morphology of the PANI coating on the silica surface was examined by scanning electron microscopy and the silica/PANI core-shell structure was confirmed by transmission electron microscopy. The chemical structure of the particles was confirmed by Fourier transform infrared spectroscopy. Rotational rheometry was performed to confirm the difference in the ER properties between pure silica and silica/PANI microsphere-based ER fluids when dispersed in silicone oil.

  8. Organic lining of MCM-41-type silicas

    SciTech Connect

    Cauvel, A.; Brunel, D.; Di Renzo, F.; Fajula, F.

    1996-01-01

    Recently discovered MCM-41 mesoporous silicas feature cylindrical mesopores of monodispersed size. The pore surface was covalently grafted with organosiloxanes. The function of the organic moieties was then transformed into longer organic chains by successive coupling reactions. The thickness of the organic lining can be controlled by modifying the length of the organic chain bound to the mineral surface. The adsorption properties of the new functionalized silicas were investigated with a special focus on the change in the adsorption enthalpies as a function of the organic coverage. {copyright} {ital 1996 American Institute of Physics.}

  9. Silica, silicosis and cancer in Finland.

    PubMed

    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. PMID:8929699

  10. Ecodesign of ordered mesoporous silica materials.

    PubMed

    Gérardin, Corine; Reboul, Julien; Bonne, Magali; Lebeau, Bénédicte

    2013-05-01

    Characterized by a regular porosity in terms of pore size and pore network arrangement, ordered mesoporous solids have attracted increasing interest in the last two decades. These materials have been identified as potential candidates for several applications. However, more environmentally friendly and economical synthesis routes of mesoporous silica materials were found to be necessary in order to develop these applications on an industrial scale. Consequently, ecodesign of ordered mesoporous silica has been considerably developed with the objective of optimizing the chemistry and the processing aspects of the material synthesis. In this review, the main strategies developed with this aim are presented and discussed. PMID:23407854

  11. Silica, silicosis and cancer in Finland.

    PubMed

    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.

  12. Silica nanoporous membranes and their applications

    NASA Astrophysics Data System (ADS)

    Khabibullin, Amir

    This thesis describes the development of novel silica and hybrid nanoporous membranes. Nanoporous membranes are widely used in various applications. This thesis focuses on their potential applications in the energy area, such as fuel cells and lithium batteries, and in separations and ultrafiltration. We use silica colloidal spheres and polymer-modified silica spheres to prepare the membranes in a time-, cost- and material-efficient manner. First, we prepared novel silica nanoporous membranes by pressing silica colloidal spheres followed by sintering. The pore size, the thickness, and the area of the membrane are precisely controlled by experiment parameters. The resulting membranes are mechanically and thermally durable, crack-free, and capable of size-selective transport. Next, to demonstrate the utility of the pressed membranes, described above, the proton-conductive pore-filled silica colloidal membranes were prepared and the fuel cells were constructed using these membranes. We modified these membranes by filling the membrane pores with surface-attached proton-conductive polymer brushes and prepared membrane-electrode assemblies to test fuel cell performance. We studied the proton conductivity and fuel cell performance as a function of the amount of sulfonic groups in the membrane. We also prepared and characterized reversible hybrid nanoporous membranes, self-assembled from solution containing polymer-modified silica colloidal spheres. Here we applied the new concept of noncovalent membranes, where the material is held together via noncovalent interactions of polymer brushes. This enables so-called reversible assembly of the membranes, in which membrane can be assembled in one solvent and dissolved in other. This approach provides advantages in recycling and reusing of the material. This work is one of the first of its kind and it opens a whole new area of research on reversible membranes made of polymer-modified nanoparticles. Finally, we applied our

  13. Silica, pneumoconiosis and carcinoma of the lung

    SciTech Connect

    Heppleston, A.G.

    1985-01-01

    The author explains the possible relationship between exposure to mineral dust with a high silica content and the development of bronchogenic carcinoma. Studies to date accept that lung cancer is a risk associated with exposure to siliceous dust. The author has sought to establish arguments to refute this theory and has accumulated observations based on practical experiences with miners which indicate that silica does not possess this carcinogenic role. The above mentioned observations take the form of medical examinations or autopsies on mine workers in different countries. 72 references.

  14. Olefin metathesis over UV-irradiated silica

    NASA Astrophysics Data System (ADS)

    Tanaka, Tsunehiro; Matsuo, Shigehiro; Maeda, Takashi; Yoshida, Hisao; Funabiki, Takuzo; Yoshida, Satohiro

    1997-11-01

    Photoirradiated silica evacuated at temperatures higher than 800 K was found to be active for olefin metathesis reactions. The analysis of products shows that the metalacyclobutane intermediate is likely. The instantaneous response of the reaction to the irradiation and the activity change with various UV filter showed that the reaction is induced by UV-excitation of silica. The correlation between the evacuation temperature and the activity showed that the surface free from water molecules plays a role in the reaction and the removal of isolated OH groups strongly relates to the generation of active sites.

  15. Dynamic Compaction Modeling of Porous Silica Powder

    NASA Astrophysics Data System (ADS)

    Borg, John P.; Schwalbe, Larry; Cogar, John; Chapman, D. J.; Tsembelis, K.; Ward, Aaron; Lloyd, Andrew

    2006-07-01

    A computational analysis of the dynamic compaction of porous silica is presented and compared with experimental measurements. The experiments were conducted at Cambridge University's one-dimensional flyer plate facility. The experiments shock loaded samples of silica dust of various initial porous densities up to a pressure of 2.25 GPa. The computational simulations utilized a linear Us-Up Hugoniot. The compaction events were modeled with CTH, a 3D Eulerian hydrocode developed at Sandia National Laboratory. Simulated pressures at two test locations are presented and compared with measurements.

  16. Contamination of furnace-drawn silica fibers.

    PubMed

    Kaiser, P

    1977-03-01

    Contamination originating in an electric resistance furnace was found to increase substantially the losses of unclad and plastic-clad silica fibers. In contrast, the losses of doped silica fibers with sufficient cladding thickness were unaffected by impure drawing conditions. Operating the furnace without muffle tube and protecting the preform with a pure, inert gas injected via a counter-flow resulted in practically contamination-free operation and unclad-fiber losses as low as 3 dB/km. The removal of the muffle tube significantly simplified the furnace operation and reduced the cycling time from many hours to a few minutes. PMID:20168565

  17. Re-evaluation of total and Umkehr ozone data from NOAA-CMDL Dobson spectrophotometer observatories. Final report

    SciTech Connect

    Komhyr, W.D.; Quincy, D.M.; Grass, R.D.; Koenig, G.L. |

    1995-12-01

    This report describes work to improve the quality of total ozone and Umkehr data obtained in the past at the NOAA Climate Monitoring and Diagnostics Laboratory and the Dobson spectrophotometer ozone observatories. The authors present results of total ozone data re-evaluations for ten stations: Byrd, Antarctica; Fairbanks, Alaska; Hallett, Antarctica; Huancayo, Peru; Haute Provence, France; Lauder, New Zealand; Perth, Australia; Poker Flat, Alaska; Puerto Montt, Chile; and South Pole, Antarctica. The improved data will be submitted in early 1996 to the World Meteorological Organization (WMO) World Ozone Data Center (WODC), and the Atmospheric Environment Service for archiving. Considerable work has been accomplished, also, in reevaluating Umkehr data from seven of the stations, viz., Huancayo, Haute Provence, Lauder, Perth, Poker Flat, Boulder, Colorado; and Mauna Loa, Hawaii.

  18. Re-evaluation and updating of the seismic hazard of Lebanon

    NASA Astrophysics Data System (ADS)

    Huijer, Carla; Harajli, Mohamed; Sadek, Salah

    2016-01-01

    This paper presents the results of a study undertaken to evaluate the implications of the newly mapped offshore Mount Lebanon Thrust (MLT) fault system on the seismic hazard of Lebanon and the current seismic zoning and design parameters used by the local engineering community. This re-evaluation is critical, given that the MLT is located at close proximity to the major cities and economic centers of the country. The updated seismic hazard was assessed using probabilistic methods of analysis. The potential sources of seismic activities that affect Lebanon were integrated along with any/all newly established characteristics within an updated database which includes the newly mapped fault system. The earthquake recurrence relationships of these sources were developed from instrumental seismology data, historical records, and earlier studies undertaken to evaluate the seismic hazard of neighboring countries. Maps of peak ground acceleration contours, based on 10 % probability of exceedance in 50 years (as per Uniform Building Code (UBC) 1997), as well as 0.2 and 1 s peak spectral acceleration contours, based on 2 % probability of exceedance in 50 years (as per International Building Code (IBC) 2012), were also developed. Finally, spectral charts for the main coastal cities of Beirut, Tripoli, Jounieh, Byblos, Saida, and Tyre are provided for use by designers.

  19. Re-evaluation of Sinocastor (Rodentia: Castoridae) with implications on the origin of modern beavers.

    PubMed

    Rybczynski, Natalia; Ross, Elizabeth M; Samuels, Joshua X; Korth, William W

    2010-11-15

    The extant beaver, Castor, has played an important role shaping landscapes and ecosystems in Eurasia and North America, yet the origins and early evolution of this lineage remain poorly understood. Here we use a geometric morphometric approach to help re-evaluate the phylogenetic affinities of a fossil skull from the Late Miocene of China. This specimen was originally considered Sinocastor, and later transferred to Castor. The aim of this study was to determine whether this form is an early member of Castor, or if it represents a lineage outside of Castor. The specimen was compared to 38 specimens of modern Castor (both C. canadensis and C. fiber) as well as fossil specimens of C. fiber (Pleistocene), C. californicus (Pliocene) and the early castorids Steneofiber eseri (early Miocene). The results show that the specimen falls outside the Castor morphospace and that compared to Castor, Sinocastor possesses a: 1) narrower post-orbital constriction, 2) anteroposteriorly shortened basioccipital depression, 3) shortened incisive foramen, 4) more posteriorly located palatine foramen, 5) longer rostrum, and 6) longer braincase. Also the specimen shows a much shallower basiocciptal depression than what is seen in living Castor, as well as prominently rooted molars. We conclude that Sinocastor is a valid genus. Given the prevalence of apparently primitive traits, Sinocastor might be a near relative of the lineage that gave rise to Castor, implying a possible Asiatic origin for Castor.

  20. A re-evaluation of dust processing in supernova shock waves

    NASA Astrophysics Data System (ADS)

    Bocchio, Marco; Jones, Anthony P.; Slavin, Jonathan D.

    2014-10-01

    Context. There is a long-standing and large discrepancy between the timescale for dust formation around evolved stars and the rapid dust destruction timescale in interstellar shocks. Aims: We use our latest estimates for dust processing to re-evaluate the dust destruction efficiency in supernova triggered shock waves, estimate the dust lifetime, and calculate the emission and extinction from shocked dust. Methods: We modelled the sputtering and fragmentation of grains in interstellar shocks for shock velocities between 50 km s-1 and 200 km s-1. We constrained the dust destruction using our recent dust model. Finally, we coupled our code to the DustEM code in order to estimate the emission and extinction from the dust post-shock. Results: Carbonaceous grains are quickly destroyed, even in a 50 km s-1 shock, leading to a shorter lifetime than in previous studies. Silicate grains appear to be more resilient, but the new destruction lifetime that we find is similar to previous studies and short compared to the dust injection timescale. Conclusions: The calculated fraction of elements locked in grains is not compatible with the observed values and therefore implies the re-formation of dust in the dense regions of the interstellar medium. Better modelling of the silicate sputtering together with hydrodynamical simulations of interstellar shocks, appears to reduce the silicate destruction and may close the destruction-formation timescale gap. Appendices are available in electronic form at http://www.aanda.org

  1. A Reevaluation of the Contribution of Very Short Lived Bromocarbons to Stratospheric Bromine Loading

    NASA Astrophysics Data System (ADS)

    Wales, P.; Salawitch, R. J.; Canty, T. P.; Mount, G. H.; Spinei, E.; Suleiman, R. M.; Chance, K.; McPeters, R. D.; Bhartia, P. K.; Kurosu, T. P.; Simpson, W. R.; Donohoue, D.; Johnson, B. J.; Kinnison, D. E.; Tilmes, S.; Choi, S.; Joiner, J.

    2015-12-01

    The Aura Ozone Monitoring Instrument (OMI) has provided global measurements of total column BrO over the past decade. Interpreting the distribution of total column BrO between the stratosphere and troposphere depends strongly on the contribution of very short lived (VSL) bromocarbons to stratospheric inorganic bromine (Bry). Salawitch et al. (2010) suggested 7 to 12 ppt of Bry must be supplied to the lower stratosphere from the decomposition of VSL bromocarbons to accurately represent the variation of total column OMI BrO with total column O3. Here we will re-evaluate this recommendation in light of ground-based total column BrO measurements obtained over Fairbanks, Alaska using a multifunction differential optical absorption spectroscopy (MFDOAS) instrument during the spring of 2011. Additionally, we will assess how modifications to kinetics regulating the partitioning between BrO and BrONO2 proposed by Kreycy et al. (2013) affect the VSL Bry estimate as well as the modeled diurnal variation in BrO. ReferencesKreycy, S. et al. Atmos. Chem. Phys. 2013, 13, 6263-6274, doi:10.5194/acp-13-6263-2013. Salawitch, R.J. et al. Geophys. Res. Lett. 2010, 37, L21805, doi:10.1029/2010GL043798.

  2. A reevaluation of spectral ratios for lunar mare TiO2 mapping

    NASA Technical Reports Server (NTRS)

    Johnson, Jeffrey R.; Larson, Stephen M.; Singer, Robert B.

    1991-01-01

    The empirical relation established by Charette et al. (1974) between the 400/560-nm spectral ratio of mature mare soils and weight percent TiO2 has been used extensively to map titanium content in the lunar maria. Relative reflectance spectra of mare regions show that a reference wavelength further into the near-IR, e.g., above 700 nm, could be used in place of the 560-nm band to provide greater contrast (a greater range of ratio values) and hence a more sensitive indicator of titanium content. An analysis of 400/730-nm ratio values derived from both laboratory and telescopic relative reflectance spectra suggests that this ratio provides greater sensitivity to TiO2 content than the 400/560-nm ratio. The increased range of ratio values is manifested in higher contrast 400/730-nm ratio images compared to 400/560-nm ratio images. This potential improvement in sensivity encourages a reevaluation of the original Charette et al. (1974) relation using the 400/730-nm ratio.

  3. Reevaluation of the macroseismic effects of the 1887 Sonora, Mexico earthquake and its magnitude estimation

    USGS Publications Warehouse

    Suárez, Gerardo; Hough, Susan E.

    2008-01-01

    The Sonora, Mexico, earthquake of 3 May 1887 occurred a few years before the start of the instrumental era in seismology. We revisit all available accounts of the earthquake and assign Modified Mercalli Intensities (MMI), interpreting and analyzing macroseismic information using the best available modern methods. We find that earlier intensity assignments for this important earthquake were unjustifiably high in many cases. High intensity values were assigned based on accounts of rock falls, soil failure or changes in the water table, which are now known to be very poor indicators of shaking severity and intensity. Nonetheless, reliable accounts reveal that light damage (intensity VI) occurred at distances of up to ~200 km in both Mexico and the United States. The resulting set of 98 reevaluated intensity values is used to draw an isoseismal map of this event. Using the attenuation relation proposed by Bakun (2006b), we estimate an optimal moment magnitude of Mw7.6. Assuming this magnitude is correct, a fact supported independently by documented rupture parameters assuming standard scaling relations, our results support the conclusion that northern Sonora as well as the Basin and Range province are characterized by lower attenuation of intensities than California. However, this appears to be at odds with recent results that Lg attenuation in the Basin and Range province is comparable to that in California.

  4. A re-evaluation of the Moyuta geothermal system, Southern Guatemala

    SciTech Connect

    Goff, F.; Adams, A.; Trujillo, P.E.; Counce, D. ); Janik, C.; Fahlquist, L. ); Roldan, A.; Revolorio, M. . Unidad de Desarollo Geotermico)

    1991-01-01

    Chemical and isotopic data from four fumarole sites combined with prefeasibility assessments obtained in the 1970s have resulted in a re-evaluation of the Moyuta geothermal system. Moyuta consists of an east-west trending complex of Quaternary andesite/dacite domes and flows cut by north-trending faults. Areas of fumaroles, acid springs, and bicarbonate-rich thermal springs flank the north and south sides of the volcanic complex. Chloride-rich thermal springs discharge along rivers at lower elevations around the Moyuta highland. The distribution of thermal features indicates that deep reservoir fluid rises convectively near the axis of volcanism. Geochemical data suggest that there are two subsystems having temperatures of about 210{degrees}C (north flank) and 170{degrees}C (south flank). Exploration wells sited near the most northerly fumarole (Azulco) achieved temperatures of {le}113{degrees}C at 1004 m depth. We suggest the fumaroles occur above hydrothermal outflow plumes confined to vertical, fault-controlled conduits. Better drilling sites occur closer to the intersections of the north trending faults and the Quaternary volcanic axis. 21 refs., 7 figs., 2 tabs.

  5. The carcinogenic effects of aspartame: The urgent need for regulatory re-evaluation.

    PubMed

    Soffritti, Morando; Padovani, Michela; Tibaldi, Eva; Falcioni, Laura; Manservisi, Fabiana; Belpoggi, Fiorella

    2014-04-01

    Aspartame (APM) is an artificial sweetener used since the 1980s, now present in >6,000 products, including over 500 pharmaceuticals. Since its discovery in 1965, and its first approval by the US Food and Drugs Administration (FDA) in 1981, the safety of APM, and in particular its carcinogenicity potential, has been controversial. The present commentary reviews the adequacy of the design and conduct of carcinogenicity bioassays on rodents submitted by G.D. Searle, in the 1970s, to the FDA for market approval. We also review how experimental and epidemiological data on the carcinogenic risks of APM, that became available in 2005 motivated the European Commission (EC) to call the European Food and Safety Authority (EFSA) for urgent re-examination of the available scientific documentation (including the Searle studies). The EC has further requested that, if the results of the evaluation should suggest carcinogenicity, major changes must be made to the current APM specific regulations. Taken together, the studies performed by G.D. Searle in the 1970s and other chronic bioassays do not provide adequate scientific support for APM safety. In contrast, recent results of life-span carcinogenicity bioassays on rats and mice published in peer-reviewed journals, and a prospective epidemiological study, provide consistent evidence of APM's carcinogenic potential. On the basis of the evidence of the potential carcinogenic effects of APM herein reported, a re-evaluation of the current position of international regulatory agencies must be considered an urgent matter of public health.

  6. Models of hemispheric specialization in facial emotion perception--a reevaluation.

    PubMed

    Najt, Pablo; Bayer, Ulrike; Hausmann, Markus

    2013-02-01

    A considerable amount of research on functional cerebral asymmetries (FCAs) for facial emotion perception has shown conflicting support for three competing models: (i) the Right Hemisphere Hypothesis, (ii) the Valence-Specific Hypothesis, and (iii) the Approach/Withdrawal model. However, the majority of studies evaluating the Right Hemisphere or the Valence-Specific Hypotheses are rather limited by the small number of emotional expressions used. In addition, it is difficult to evaluate the Approach/Withdrawal Hypothesis due to insufficient data on anger and FCAs. The aim of the present study was (a) to review visual half field (VHF) studies of hemispheric specialization in facial emotion perception and (b) to reevaluate empirical evidence with respect to all three partly conflicting hypotheses. Results from the present study revealed a left visual field (LVF)/right hemisphere advantage for the perception of angry, fearful, and sad facial expressions and a right visual field (RVF)/left hemisphere advantage for the perception of happy expressions. Thus, FCAs for the perception of specific facial emotions do not fully support the Right Hemisphere Hypothesis, the Valence-Specific Hypothesis, or the Approach/Withdrawal model. A systematic literature review, together with the results of the present study, indicate a consistent LVF/right hemisphere advantage only for a subset of negative emotions including anger, fear and sadness, rather suggesting a "negative (only) valence model."

  7. Close friends', parents', and older siblings' smoking: reevaluating their influence on children's smoking.

    PubMed

    Bricker, Jonathan B; Peterson, Arthur V; Robyn Andersen, M; Leroux, Brian G; Bharat Rajan, K; Sarason, Irwin G

    2006-04-01

    A number of longitudinal studies have explored the role of friends', parents', and older siblings' smoking in children's smoking acquisition. A reasonable implication of this previous research is that intervention efforts could be beneficially directed toward countering the potential influence of friends' and possibly older siblings' smoking but not parents' smoking. However, methodological limitations of this previous research motivated our reevaluation of the role of friends', parents', and older siblings' smoking in children's smoking. Close friends' smoking status was assessed when children were in 5th grade, whereas parents' and older siblings' smoking status was assessed when children were in 3rd grade. The outcome, children's daily smoking status, was assessed in 12th grade. The setting was 40 Washington state school districts that participated in the long-term Hutchinson Smoking Prevention Project. Participants were the 4,576 families for whom close friends', parents', and older siblings' smoking status as well as children's smoking status were available. The probability that each close friend's smoking influenced the child to smoke daily was 9% (95% CI = 6%-12%), the probability that each parent's smoking influenced the child to smoke daily was 11% (95% CI = 9%-14%), and the probability that each older sibling's smoking influenced the child to smoke daily was 7% (95% CI = 1%-13%). These results suggest that close friends', parents', and siblings' smoking were similarly important influences on children's smoking. Family-focused interventions could be a valuable future direction of prevention research. PMID:16766414

  8. Re-Evaluation of the Lifetimes of Ozone-Depleting Substances and Related Trace Gases

    NASA Astrophysics Data System (ADS)

    Reimann, Stefan; Ko, Malcolm; Newman, Paul; Strahan, Susan

    2013-04-01

    Estimating the average lifetime of a chemical in the atmosphere is crucial to understanding their current and future atmospheric concentrations. Furthermore, for ozone depleting substances (ODSs) and greenhouse gases information on their lifetimes are of paramount importance for obtaining estimates for ozone depletion and climate forcing. Because the lifetimes of ODSs are also used to predict how the future concentrations change with emissions, they also have implications on policy decisions for limiting future release of hydrochlorofluorocarbons (HCFCs) and other replacement compounds under the Montreal Protocol. During the last 25 years, various methods have been used to derive lifetimes of ODSs and values have changed accordingly. Within the last several years evidence is growing that the lifetimes of certain ODSs are possibly somewhat longer than published values. The "Lifetime of halogen source gases" activity under the World Climate Research Programme (WCRP)/Stratospheric Processes And their Role in Climate (SPARC) project has convened a working group to re-evaluate these ODS lifetimes. The goal was to estimate the numerical values for lifetimes and their uncertainties, and to quantify how the values may depend on factors such as the use of different lifetime definitions (e.g. steady-state/instantaneous lifetimes) and changing climate. First results of the report will be shown and implications will be discussed.

  9. Dust Destruction in the ISM: A Re-Evaluation of Dust Lifetimes

    NASA Technical Reports Server (NTRS)

    Jones, A. P.; Nuth, J. A., III

    2011-01-01

    There is a long-standing conundrum in interstellar dust studies relating to the discrepancy between the time-scales for dust formation from evolved stars and the apparently more rapid destruction in supernova-generated shock waves. Aims. We re-examine some of the key issues relating to dust evolution and processing in the interstellar medium. Methods. We use recent and new constraints from observations, experiments, modelling and theory to re-evaluate dust formation in the interstellar medium (ISM). Results. We find that the discrepancy between the dust formation and destruction time-scales may not be as significant as has previously been assumed because of the very large uncertainties involved. Conclusions. The derived silicate dust lifetime could be compatible with its injection time-scale, given the inherent uncertainties in the dust lifetime calculation. The apparent need to re-form significant quantities of silicate dust in the tenuous interstellar medium may therefore not be a strong requirement. Carbonaceous matter, on the other hand, appears to be rapidly recycled in the ISM and, in contrast to silicates, there are viable mechanisms for its re-formation in the ISM.

  10. Re-Evaluation of Sinocastor (Rodentia: Castoridae) with Implications on the Origin of Modern Beavers

    PubMed Central

    Rybczynski, Natalia; Ross, Elizabeth M.; Samuels, Joshua X.; Korth, William W.

    2010-01-01

    The extant beaver, Castor, has played an important role shaping landscapes and ecosystems in Eurasia and North America, yet the origins and early evolution of this lineage remain poorly understood. Here we use a geometric morphometric approach to help re-evaluate the phylogenetic affinities of a fossil skull from the Late Miocene of China. This specimen was originally considered Sinocastor, and later transferred to Castor. The aim of this study was to determine whether this form is an early member of Castor, or if it represents a lineage outside of Castor. The specimen was compared to 38 specimens of modern Castor (both C. canadensis and C. fiber) as well as fossil specimens of C. fiber (Pleistocene), C. californicus (Pliocene) and the early castorids Steneofiber eseri (early Miocene). The results show that the specimen falls outside the Castor morphospace and that compared to Castor, Sinocastor possesses a: 1) narrower post-orbital constriction, 2) anteroposteriorly shortened basioccipital depression, 3) shortened incisive foramen, 4) more posteriorly located palatine foramen, 5) longer rostrum, and 6) longer braincase. Also the specimen shows a much shallower basiocciptal depression than what is seen in living Castor, as well as prominently rooted molars. We conclude that Sinocastor is a valid genus. Given the prevalence of apparently primitive traits, Sinocastor might be a near relative of the lineage that gave rise to Castor, implying a possible Asiatic origin for Castor. PMID:21085579

  11. Improved zircon fission-track annealing model based on reevaluation of annealing data

    SciTech Connect

    Guedes, S.; Moreira, Pedro; Devanathan, Ramaswami; Weber, William J.; Hadler, J. C.

    2012-11-10

    The thermal recovery (annealing) of mineral structure modified by the passage of fission fragments has long been studied by the etching technique. In minerals like apatite and zircon, the annealing kinetics are fairly well constrained from the hour to the million-year timescale and have been described by empirical and semi-empirical equations. On the other hand, laboratory experiments, in which ion beams interact with minerals and synthetic ceramics, have shown that there is a threshold temperature beyond which thermal recovery impedes ion-induced amorphization. In this work, it is assumed that this behavior can be extended to the annealing of fission tracks in minerals. It is proposed that there is a threshold temperature, T 0, beyond which fission tracks are erased within a time t 0, which is independent of the current state of lattice deformation. This implies that iso-annealing curves should converge to a fanning point in the Arrhenius pseudo-space (ln t vs. 1/T). Based on the proposed hypothesis, and laboratory and geological data, annealing equations are reevaluated. The geological timescale estimations of a model arising from this study are discussed through the calculation of partial annealing zone and closure temperature, and comparison with geological sample constraints found in literature. It is shown that the predictions given by this model are closer to field data on closure temperature and partial annealing zone than predictions given by previous models.

  12. Improved zircon fission-track annealing model based on reevaluation of annealing data

    SciTech Connect

    Guedes, Sandro; Moreira, Pedro A.F.P.; Devanathan, Ram; Weber, William J; Hadler, Julio C

    2013-01-01

    The thermal recovery (annealing) of mineral structure modified by the passage of fission fragments has long been studied by the etching technique. In minerals like apatite and zircon, the annealing kinetics are fairly well constrained from the hour to the million-year timescale and have been described by empirical and semi-empirical equations. On the other hand, laboratory experiments, in which ion beams interact with minerals and synthetic ceramics, have shown that there is a threshold temperature beyond which thermal recovery impedes ion-induced amorphization. In this work, it is assumed that this behavior can be extended to the annealing of fission tracks in minerals. It is proposed that there is a threshold temperature, T0, beyond which fission tracks are erased within a time t0, which is independent of the current state of lattice deformation. This implies that iso-annealing curves should converge to a fanning point in the Arrhenius pseudo-space (ln t vs. 1/T). Based on the proposed hypothesis, and laboratory and geological data, annealing equations are reevaluated. The geological timescale estimations of a model arising from this study are discussed through the calculation of partial annealing zone and closure temperature, and comparison with geological sample constraints found in literature. It is shown that the predictions given by this model are closer to field data on closure temperature and partial annealing zone than predictions given by previous models.

  13. Adaptively Reevaluated Bayesian Localization (ARBL). A Novel Technique for Radiological Source Localization

    SciTech Connect

    Miller, Erin A.; Robinson, Sean M.; Anderson, Kevin K.; McCall, Jonathon D.; Prinke, Amanda M.; Webster, Jennifer B.; Seifert, Carolyn E.

    2015-01-19

    Here we present a novel technique for the localization of radiological sources in urban or rural environments from an aerial platform. The technique is based on a Bayesian approach to localization, in which measured count rates in a time series are compared with predicted count rates from a series of pre-calculated test sources to define likelihood. Furthermore, this technique is expanded by using a localized treatment with a limited field of view (FOV), coupled with a likelihood ratio reevaluation, allowing for real-time computation on commodity hardware for arbitrarily complex detector models and terrain. In particular, detectors with inherent asymmetry of response (such as those employing internal collimation or self-shielding for enhanced directional awareness) are leveraged by this approach to provide improved localization. Our results from the localization technique are shown for simulated flight data using monolithic as well as directionally-aware detector models, and the capability of the methodology to locate radioisotopes is estimated for several test cases. This localization technique is shown to facilitate urban search by allowing quick and adaptive estimates of source location, in many cases from a single flyover near a source. In particular, this method represents a significant advancement from earlier methods like full-field Bayesian likelihood, which is not generally fast enough to allow for broad-field search in real time, and highest-net-counts estimation, which has a localization error that depends strongly on flight path and cannot generally operate without exhaustive search

  14. Reevaluation of patients with bipolar disorder on manic episode: improving the diagnosing of mixed episode.

    PubMed

    Kim, Kyung Ran; Cho, Hyun-Sang; Kim, Se Joo; Seok, Jeong-Ho; Lee, Eun; Jon, Duk-In

    2013-08-01

    Mixed manic/depressive episodes in patients with bipolar disorder are underdiagnosed because of restrictive diagnostic criteria. Using the broader definition of a mixed episode represented by the Cincinnati criteria, we reevaluated the medical records of patients with bipolar disorder hospitalized for a manic episode. We also examined the predictive power of previously unrecognized depressive symptoms. Of 520 inpatients with mania, we retrospectively diagnosed 59 (11.3%) as having a probable mixed episode. Compared with the patients with pure mania, the patients with mixed episodes were more likely to have a family history of psychiatric illness, comorbid personality disorder, and a history of suicide attempts. Binary logistic regression revealed that loss of interest, loss of energy, feelings of worthlessness, and feelings of helplessness had good positive predictive value (>0.7) for mixed episodes. Accurate diagnosis of mixed episodes may require a broadening of diagnostic criteria and emphasis on symptoms such as loss of interest, loss of energy, and feelings of worthlessness and helplessness.

  15. Reevaluating the feasibility of ground-based Earth-mass microlensing planet detections

    SciTech Connect

    Jung, Youn Kil; Park, Hyuk; Han, Cheongho; Hwang, Kyu-Ha; Shin, In-Gu; Choi, Joon-Young

    2014-05-10

    An important strength of the microlensing method to detect extrasolar planets is its high sensitivity to low-mass planets. However, many believe that microlensing detections of Earth-mass planets from ground-based observation would be difficult because of limits set by finite-source effects. This view comes from the previous estimation of planet detection probability based on the fractional deviation of planetary signals; however, a proper probability estimation is required when considering the source brightness, which is directly related to the photometric precision. In this paper, we reevaluate the feasibility of low-mass planet detections by considering photometric precision for different populations of source stars. From this, we find that the contribution of improved photometric precision to the planetary signal of a giant-source event is large enough to compensate for the decrease in magnification excess caused by finite-source effects. As a result, we conclude that giant-source events are suitable targets for Earth-mass planet detections with significantly higher detection probability than events involved with source stars of smaller radii, and we predict that Earth-mass planets could be detected by prospective high-cadence surveys.

  16. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  17. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  18. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  19. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  20. 40 CFR 721.10119 - Siloxane modified silica nanoparticles (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Siloxane modified silica nanoparticles... Specific Chemical Substances § 721.10119 Siloxane modified silica nanoparticles (generic). (a) Chemical... as siloxane modified silica nanoparticles (PMN P-05-673) is subject to reporting under this...

  1. Re-evaluation of the kidney tumors and renal histopathology occurring in a 2-year rat carcinogenicity bioassay of quercetin.

    PubMed

    Hard, Gordon C; Seely, John Curtis; Betz, Laura J; Hayashi, Shim-Mo

    2007-04-01

    Renal histopathology in the most recent 2-year carcinogenicity bioassay of quercetin, in Fischer 344 rats, was re-evaluated in an attempt to determine a mode of action underlying a small increase in renal tubule tumors reported in the males (). The re-evaluation confirmed the reported increase in renal tumors in mid- and high-dose males, including a single carcinoma in a high-dose male, as well as an exacerbation of spontaneous, chronic progressive nephropathy (CPN) in male rats only. The re-evaluation also showed that there were no cellular alterations in the kidney indicative of chemical toxicity at 6 months, 15 months, or 2 years. The evidence linked the occurrence of the predominant basophilic adenomas and foci of atypical tubule hyperplasia (ATH) with the exacerbation of CPN to advanced grades of severity, supporting a mode of action involving quercetin interaction with CPN. This mode of action represents a secondary mechanism for renal tumor development, with no relevance for extrapolation to humans. In addition, the single carcinoma present in the high-dose males, along with 4 other lesions ranging from ATH to adenoma in male and female groups, were considered to have a unique phenotype associated previously with neoplasms of spontaneous and familial origin.

  2. Characterization of vanadium/silica and copper/silica aerogel catalysts

    SciTech Connect

    Owens, L.; Tillotson, T.M.; Hair, L.M.

    1995-09-01

    Vanadium/silica and copper/silica aerogels have been prepared using the sol-gel method followed by CO{sub 2} exchange and supercritical extraction. Structural properties of samples supercritically dried, oxidized and used in reactions studies conducted with a feed representing the average composition of automobile exhaust from a lean burn engine were investigated using laser Raman spectroscopy and temperature-programmed reduction. No evidence of crystalline V{sub 2}O{sub 5} was found for the vanadium/silica aerogel, freshly extracted, oxidized or following exposure to reaction conditions using these techniques. However, results obtained for the copper/silica sample indicate that changes in the structure of the copper species had occurred as the sample was oxidized and exposed to reaction conditions.

  3. Aerosol coating of silica fibers with nanoparticles

    SciTech Connect

    Fotou, G.P.; Scott, S.J.; Pratsinis, S.E.

    1994-12-31

    Dendritic silica fibers are in demand for applications such as hot-gas filtration, chromatography, and fabrication of ceramic composites. Because of their high interception area, these fibers are particularly suitable for use as filter elements for high-efficiency, low-pressure drop filtration of particles from gas streams. An aerosol process was developed recently for coating ultrafine silica fibers with nonsize silica particles. Fibers were suspended in air and introduced in a particle-laden flame. Coagulation between the silica particles and the fibers resulted in dendritic structures that increased the specific surface area of the fibers by up to 16 times. Sol-gel processing has also been used for coating fibers. In this study, the catalytic effect of ferrocene on the flame synthesis of high-surface area particle-coated fibers is investigated. Ferrocene (dicylopentadienyl iron) is an organometallic compound of iron. It has been used in the past as catalyst in whisker growth on carbon fibers in a laser reactor. It has also been used as additive for the control of soot growth in hydrocarbon flames. These studies showed that the effect of ferrocene on soot particle growth is related to residence time and mixing of the reactants in the flame. The efficiency of the aerosol coating process is evaluated in terms of the specific surface area enhancement of the fibers.

  4. Silica and dolomite paragenesis in crinoidal limestones

    SciTech Connect

    Lyons, T.W.; Vahrenkamp, V.C.

    1985-01-01

    The intimate association of silica and dolomite in crinoid fragments is a commonly observed phenomenon in chert-rich carbonates of all ages. An investigation of this silica/dolomite association in some Phanerozoic examples from North America has revealed a striking cause and effect relationship between silicification and dolomitization which closely parallels the findings of Jacka (1974). Based on detailed petrographic analysis of crinoidal limestones, it is argued that dolomite forms concomitant with, and as a product of, the replacement of calcium carbonate by silica. Two possible mechanisms exist regarding the observed paragenesis: 1) silica replacement of high magnesian-calcite (HMC) mobilizes and redistributes Mg/sup 2 +/ resulting in the simultaneous partial dolomitization of the remaining HMC; this dolomite is then selectively preserved or partially replaced during continued silicification; 2) initially, metastable opal-CT being derived from the crinoid host; during the ensuing opal-CT to quartz transformation, Mg/sup 2 +/ is liberated and causes local dolomitization. Petrographic observations suggest that a significant volume of replacement dolomite can be generated from a local source of Mg/sup 2 +/, here the HMC crinoid host. Dolomitization occurred during early diagenesis prior to the stabilization of HMC to LMC possibly in a mixed-water environment. Low temperature natural co-precipitation of quartz and dolomite may provide an alternative mechanism whereby the oxygen isotopic fractionation between water and dolomite could be calculated.

  5. Growth of hydroxyapatite nanoparticles on silica gels.

    PubMed

    Rivera-Muñoz, E M; Huirache-Acuña, R; Velázquez, R; Alonso-Núñez, G; Eguía-Eguía, S

    2011-06-01

    Synthetic, hydroxyapatite nanoparticles were grown on the surface of silica gels. The synthesis of those nanoparticles was obtained by immersing silica gels in a simulated body fluid (SBF) at 37 degrees C. The SBF was replaced every week to keep constant the Ca and P ion concentration and subsequent growth of hydroxyapatite was evaluated after 1-6 weeks of total soaking time in SBF. Hydroxyapatite nanoparticles were observed by scanning electron microscopy (SEM) on the surface of silica gel samples and confirmed by energy dispersive X-ray spectroscopy (EDS), Fourier Transform Infra Red Spectroscopy (FTIR) and powder X-ray Diffractometry (XRD) analysis. These particles show a regular shape and uniform size every week, keeping within the nanoscale always. Both the size and morphology of hydroxyapatite nanoparticles obtained are the result of the use of different chemical additives in the synthesis of silica gels, since they affect the liquid-to-solid interface, and the growth could correspond to a diffusion limited aggregation (DLA) process. A more detailed analysis, with higher magnifications, showed that hydroxyapatite nanoparticles are not solid spheres, showing a branched texture and their size depends on the scale and resolution of the measure instrument. PMID:21770224

  6. Zinc oxide nanostructures confined in porous silicas.

    PubMed

    Coasne, Benoit; Mezy, Aude; Pellenq, R J M; Ravot, D; Tedenac, J C

    2009-02-18

    We report on molecular simulations of zinc oxide nanostructures obtained within silica nanopores of diameter D = 1.6 nm and D = 3.2 nm. Both the effects of confinement (by varying the pore size) and degree of pore filling on the structure of the nanomaterial are addressed. Two complementary approaches are adopted: 1) the stability of the three crystalline phases of ZnO (wurtzite, rocksalt, and blende) in the silica nanopores is studied, and 2) ZnO nanostructures are obtained by slowly cooling down a homogeneous liquid phase confined in the silica pores. None of the ideal nanostructures (wurtzite, rocksalt, blende) retains the ideal structure of the initial crystal when confined within the silica pores. Only the structure starting from the ideal wurtzite nanocrystal remains significantly crystalline after relaxation, as revealed by the marked peaks in the pair correlation functions for this system. The morphology and degree of cristallinity of the structures are found to depend on the parameters involved in the synthesis (pore size, filling density). Nanograin boundaries are observed between domains of different crystal structures. Reminiscent features of the bulk behavior, such as faceting of the nanostructures, are also observed when the system size becomes large. We show that the use of nanopores as a template imposes that the confined particles exhibit neutral (basal) surfaces. These predictions provide a guide to experiments on semiconductor nanoparticles.

  7. Kinetics of silica-phase transitions

    SciTech Connect

    Duffy, C.J.

    1993-07-01

    In addition to the stable silica polymorph quartz, several metastable silica phases are present in Yucca Mountain. The conversion of these phases to quartz is accompanied by volume reduction and a decrease in the aqueous silica activity, which may destabilize clinoptilolite and mordenite. The primary reaction sequence for the silica phases is from opal or glass to disordered opal-CT, followed by ordering of the opal-CT and finally by the crystallization of quartz. The ordering of opal-CT takes place in the solid state, whereas the conversion of opal-CT takes place through dissolution-reprecipitation involving the aqueous phase. It is proposed that the rate of conversion of opal-CT to quartz is controlled by diffusion of defects out of a disordered surface layer formed on the crystallizing quartz. The reaction rates are observed to be dependent on temperature, pressure, degree of supersaturation, and pH. Rate equations selected from the literature appear to be consistent with observations at Yucca Mountain.

  8. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, N.K.; Brinker, C.J.

    1999-08-10

    A process is described for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film. 11 figs.

  9. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, Narayan K.; Brinker, Charles Jeffrey

    1999-01-01

    A process for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film.

  10. Solvated calcium ions in charged silica nanopores

    NASA Astrophysics Data System (ADS)

    Bonnaud, Patrick A.; Coasne, Benoît; Pellenq, Roland J.-M.

    2012-08-01

    Hydroxyl surface density in porous silica drops down to nearly zero when the pH of the confined aqueous solution is greater than 10.5. To study such extreme conditions, we developed a model of slit silica nanopores where all the hydrogen atoms of the hydroxylated surface are removed and the negative charge of the resulting oxygen dangling bonds is compensated by Ca2+ counterions. We employed grand canonical Monte Carlo and molecular dynamics simulations to address how the Ca2+ counterions affect the thermodynamics, structure, and dynamics of confined water. While most of the Ca2+ counterions arrange themselves according to the so-called "Stern layer," no diffuse layer is observed. The presence of Ca2+ counterions affects the pore filling for strong confinement where the surface effects are large. At full loading, no significant changes are observed in the layering of the first two adsorbed water layers compared to nanopores with fully hydroxylated surfaces. However, the water structure and water orientational ordering with respect to the surface is much more disturbed. Due to the super hydrophilicity of the Ca2+-silica nanopores, water dynamics is slowed down and vicinal water molecules stick to the pore surface over longer times than in the case of hydroxylated silica surfaces. These findings, which suggest the breakdown of the linear Poisson-Boltzmann theory, provide important information about the properties of nanoconfined electrolytes upon extreme conditions where the surface charge and ion concentration are large.

  11. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, Narayan K.; Brinker, Charles Jeffrey

    1998-01-01

    A process for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film.

  12. Determining silica solubility in bayer process liquor

    NASA Astrophysics Data System (ADS)

    Müller-Steinhagen, H.

    1998-11-01

    The efficient precipitation of dissolved silica from Bayer process liquor is essential for the production of high-quality alumina and the reduction of excessive scaling in the heat exchangers in the evaporation building of Bayer processes. The accurate prediction of silica solubility in Bayer liquor is one of the key parameters in improving the design and operation of the desilication process. Previous findings, particularly with respect to the influence of temperature and concentrations of caustic soda and alumina on the solubility of silica, are inconclusive. In this article, experimental results are presented over a wide range of temperature and alumina and caustic soda concentrations. Attempts are made to utilize artificial neural networks for identifying the process variables and modeling. The radial basis function neural network architecture was used successfully to generate a nonlinear correlation for the prediction of the solubility of silica in Bayer process liquor. The resulting correlation can predict the present data and the control data of other investigators with good accuracy.

  13. Carbon Nanotube Synthesis Using Mesoporous Silica Templates

    SciTech Connect

    Zheng, Feng; Liang, Liang; Gao, Yufei; Sukamto, Johanes H.; Aardahl, Chris L.

    2002-07-01

    Well-aligned carbon nanotubes (CNTs) were grown on mesoporous silica films by chemical vapor deposition (CVD). Ethylene was used as the carbon source and CVD was performed at 1023 K and atmospheric pressure. The films were doped with Fe during gelation, and three different structure directing agents were used for mesoporous silica synthesis: polyoxyethylene (10) cetyl ether (C16EO10), Pluronic tri-block copolymer (P123), and cetyltriethylammonium chloride (CTAC). A high degree of CNT alignment on C16EO10-mesoporous silica films was produced at Fe:Si molar ratio of 1.80. Similar alignment of CNTs was achieved on the other two types of films but on CTAC-mesoporous silica films, CNTs only grew parallel to the substrate surface from the cracks in the films because of the in-plane arrangement of the mesopores in such films. Considerable progress has been made in producing multi-walled carbon nanotubes (CNTs) by catalytic CVD techniques. If CNTs are to be integrated into certain useful devices, it is critical to be able to grow highly aligned arrays of CNTs with narrow size distribution and at specific locations on a substrate. Long-range alignment normal to the substrate results from steric crowding if the initial catalyst sites are sufficiently dense. Alignment may be improved with better control of the density of catalytic sites by means of a template of appropriate pore structure. The confinement of CNTs by the pores during the initial growth may also help align CNTs.

  14. Preparation of EPR/silica filler by a co-irradiation method forming PP/EPR/silica nanocomposites

    NASA Astrophysics Data System (ADS)

    Qian, Jun; Dang, Shuaiying; Huang, Zhijuan; Xu, Yongshen

    2012-01-01

    This paper presents a novel approach to prepare ethylene-propylene rubber (EPR)/silica filler by co-irradiation method forming polypropylene (PP)/EPR/silica nanocomposites. The grafting of maleic anhydride (MAH) on EPR was first studied by co-irradiation in the micro-suspension without any chemical initiator, and the effects of MAH concentration and the total co-irradiation dose on the graft degree of MAH were investigated. Then PP/EPR/silica nanocomposites were successfully prepared by blending of PP matrix and EPR/silica filler, which was obtained by co-irradiation using a mixture of EPR/MAH microsuspension in xylene and tetraethoxysilane/KH560 sol in formic acid. FTIR and SEM results showed that the reactions between MAH on EPR chains and KH560 surrounding silica particles were adopted to form the EPR/silica filler with strong bonding and well silica dispersion. Mechanical properties of PP/EPR/silica nanocomposites with different silica contents and the comparisons with PP, PP/EPR and PP/silica films were studied. The rigid silica particles were trapped in EPR shell and well dispersed in PP/EPR/silica nanocomposites with good compatibility and strong interfacial adhesion, achieving overall improvements in stiffness, strength and toughness compared with pure PP.

  15. Soluble polymers in sol-gel silica

    NASA Astrophysics Data System (ADS)

    Beaudry, Christopher Laurent

    In the last few years, the inherent versatility of sol-gel processing has led to a significant research effort on inorganic/organic materials. One method of incorporating an organic phase into sol-gel silica is dissolving an organic polymer in a tetraethylorthosilicate (TEOS) solution, followed by in situ polymerization of silica in the presence of organic polymer. The first part of the study involved the development of a two-step (acid-base) synthesis procedure to allow systematic control of acidity in TEOS solutions. With this procedure, it was possible to increase the pH of the TEOS solution while correlating the acidity and properties. The properties were the gelation time, syneresis rate, drying behavior, and xerogel pore structure, as determined by nitrogen sorption. Furthermore, controlling the acidity was shown to control the silica xerogel pore structure. In the second part of the study, the two-step procedure was used to synthesize silica/poly(ethylene glycol) (PEG), and silica/poly(vinyl acetate) (PVAc) composite materials. The content of organic polymer and the molecular weight were varied. The gelation time, the syneresis rate, the drying behavior, and the pore structure were determined for compositions with 10% PEG (M.W. 2,000), 5, 10, and 15% PEG (M.W. 3,400), and 10 and 25% PVAc (M.W. 83,000). Other compositions and molecular weights of PEG lead to sedimentation. In the PEG compositions, the tendency to phase separate was correlated with the effects of the processing variables on the segregation strength and polymerization rate. The PVAc compositions did not show any visible phase separation during processing, giving the composite xerogels an appearance similar to pure silica. The property differences between gels with PEG and gels with PVAc show the relative strength of the interactions with silica. Both polymers exhibit hydrogen bonding between the phases. In the case of PEG, hydrogen bonding between the ether oxygens of the polymer and silanol

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

    PubMed

    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

  17. Effect of silica nanoparticles on microbial biomass and silica availability in maize rhizosphere.

    PubMed

    Rangaraj, Suriyaprabha; Gopalu, Karunakaran; Rathinam, Yuvakkumar; Periasamy, Prabu; Venkatachalam, Rajendran; Narayanasamy, Kannan

    2014-01-01

    The effect of silica nanoparticles and conventional silica sources on the changes in microbial biomass and silica availability to pure soil and maize rhizosphere was studied. Nanosilica (20-40 nm) was synthesized from rice husk and comprehensively characterized. The efficiency of nanosilica was evaluated in terms of its effects on beneficial microbial population such as phosphate solubilizers, nitrogen fixers, silicate solubilizers, microbial biomass carbon and nitrogen content, and silica content in comparison with other silica sources such as microsilica, sodium silicate, and silicic acid. Nanosilica significantly (P < 0.05) enhanced microbial populations, total biomass content (C = 1508 μg g(-1) and N = 178 μg g(-1) ), and silica content (14.75 mg mL(-1) ). Although microsilica sources enhanced factors associated with soil fertility, their use by maize roots and silicification in soil was found to be less. The results show that nanosilica plays a vital role in influencing soil nutrient content and microbial biota and, hence, may promote the growth of maize crop. PMID:24329970

  18. Dissolution retardation of solid silica during glass batch-melting

    SciTech Connect

    Hrma, Pavel R.; Marcial, Jose

    2011-07-15

    During glass-batch melting, solid silica (quartz) usually dissolves last. A retardation function was defined as a measure of the progressive inhibition of silica dissolution that occurs during batch melting. This function is based on the comparison of the measured rate of dissolution of silica particles with the hypothetical diffusion-controlled volume flux from regularly distributed particles with uniform concentration layers around them. The severe inhibition of silica dissolution has been attributed to the irregular spatial distribution of silica particles that is associated with the formation of nearly saturated melt at a portion of their surfaces. Irregular shapes and unequal sizes of particles also contribute to their extended lifetime.

  19. Process for Preparing Epoxy-Reinforced Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B (Inventor)

    2016-01-01

    One-pot reaction process for preparing epoxy-reinforced monolithic silica aerogels comprising the reaction of at least one silicon compound selected from the group consisting of alkoxysilanes, orthosilicates and combination thereof in any ratio with effective amounts of an epoxy monomer and an aminoalkoxy silane to obtain an epoxy monomer-silica sol in solution, subsequently preparing an epoxy-monomer silica gel from said silica sol solution followed by initiating polymerization of the epoxy monomer to obtain the epoxy-reinforced monolithic silica aerogel.

  20. Silica/silicone nanofilament hybrid coatings with almost perfect superhydrophobicity.

    PubMed

    Zhang, Junping; Seeger, Stefan

    2013-06-01

    A facile method for the preparation of silica/silicone nanofilament hybrid coatings with almost perfect superhydrophobicity (contact angle=179.8° and sliding angle=1.3°) is presented. The coatings are obtained by dip-coating of silica nanoparticles, followed by chemical vapor deposition of silicone nanofilaments. Predominant growth of silicone nanofilaments onto aggregated silica nanoparticles generates a two-tier structure. The effect of silica nanoparticle size on the growth of silicone nanofilaments, along with their anti-wetting properties and transparency are investigated in detail. Surface roughness and anti-wetting properties can be simply regulated by controlling the size of silica nanoparticles.

  1. Incorporation of anti-inflammatory agent into mesoporous silica

    NASA Astrophysics Data System (ADS)

    Rodrigues Braz, Wilson; Lamec Rocha, Natállia; de Faria, Emerson H.; Silva, Márcio L. A. e.; Ciuffi, Katia J.; Tavares, Denise C.; Furtado, Ricardo Andrade; Rocha, Lucas A.; Nassar, Eduardo J.

    2016-09-01

    The unique properties of macroporous, mesoporous, and microporous systems, including their ability to accommodate molecules of different sizes inside their pores and to act as drug delivery systems, have been the object of extensive studies. In this work, mesoporous silica with hexagonal structure was obtained by template synthesis via the sol-gel process. The resulting material was used as support to accommodate the anti-inflammatory agent indomethacin. The alkaline route was used to prepare the mesoporous silica; cetyltrimethylammonium bromide was employed as porogenic agent. The silica particles were functionalized with 3-aminopropyltriethoxysilane alkoxide (APTES) by the sol-gel post-synthesis method. Indomethacin was incorporated into the silica functionalized with APTES and into non-functionalized silica. The resulting systems were characterized by x-ray diffraction (XRD), specific area, infrared spectroscopy, and thermal analyses (TGA). XRD attested to formation of mesoporous silica with hexagonal structure. This structure remained after silica functionalization with APTES and incorporation of indomethacin. Typical infrared spectroscopy vibrations and organic material decomposition during TGA confirmed silica functionalization and drug incorporation. The specific surface area and pore volume of the functionalized material incorporated with indomethacin decreased as compared with the specific surface area and pore volume of the non-functionalized silica containing no drug, suggesting both the functionalizing agent and the drug were present in the silica. Cytotoxicity tests conducted on normal fibroblasts (GM0479A) cells attested that the silica matrix containing indomethacin was less toxic than the free drug.

  2. Incorporation of anti-inflammatory agent into mesoporous silica

    NASA Astrophysics Data System (ADS)

    Rodrigues Braz, Wilson; Lamec Rocha, Natállia; de Faria, Emerson H.; Silva, Márcio L. A. e.; Ciuffi, Katia J.; Tavares, Denise C.; Furtado, Ricardo Andrade; Rocha, Lucas A.; Nassar, Eduardo J.

    2016-09-01

    The unique properties of macroporous, mesoporous, and microporous systems, including their ability to accommodate molecules of different sizes inside their pores and to act as drug delivery systems, have been the object of extensive studies. In this work, mesoporous silica with hexagonal structure was obtained by template synthesis via the sol–gel process. The resulting material was used as support to accommodate the anti-inflammatory agent indomethacin. The alkaline route was used to prepare the mesoporous silica; cetyltrimethylammonium bromide was employed as porogenic agent. The silica particles were functionalized with 3-aminopropyltriethoxysilane alkoxide (APTES) by the sol–gel post-synthesis method. Indomethacin was incorporated into the silica functionalized with APTES and into non-functionalized silica. The resulting systems were characterized by x-ray diffraction (XRD), specific area, infrared spectroscopy, and thermal analyses (TGA). XRD attested to formation of mesoporous silica with hexagonal structure. This structure remained after silica functionalization with APTES and incorporation of indomethacin. Typical infrared spectroscopy vibrations and organic material decomposition during TGA confirmed silica functionalization and drug incorporation. The specific surface area and pore volume of the functionalized material incorporated with indomethacin decreased as compared with the specific surface area and pore volume of the non-functionalized silica containing no drug, suggesting both the functionalizing agent and the drug were present in the silica. Cytotoxicity tests conducted on normal fibroblasts (GM0479A) cells attested that the silica matrix containing indomethacin was less toxic than the free drug.

  3. Conversion of geothermal waste to commercial products including silica

    DOEpatents

    Premuzic, Eugene T.; Lin, Mow S.

    2003-01-01

    A process for the treatment of geothermal residue includes contacting the pigmented amorphous silica-containing component with a depigmenting reagent one or more times to depigment the silica and produce a mixture containing depigmented amorphous silica and depigmenting reagent containing pigment material; separating the depigmented amorphous silica and from the depigmenting reagent to yield depigmented amorphous silica. Before or after the depigmenting contacting, the geothermal residue or depigmented silica can be treated with a metal solubilizing agent to produce another mixture containing pigmented or unpigmented amorphous silica-containing component and a solubilized metal-containing component; separating these components from each other to produce an amorphous silica product substantially devoid of metals and at least partially devoid of pigment. The amorphous silica product can be neutralized and thereafter dried at a temperature from about 25.degree. C. to 300.degree. C. The morphology of the silica product can be varied through the process conditions including sequence contacting steps, pH of depigmenting reagent, neutralization and drying conditions to tailor the amorphous silica for commercial use in products including filler for paint, paper, rubber and polymers, and chromatographic material.

  4. Silica substrate or portion formed from oxidation of monocrystalline silicon

    DOEpatents

    Matzke, Carolyn M.; Rieger, Dennis J.; Ellis, Robert V.

    2003-07-15

    A method is disclosed for forming an inclusion-free silica substrate using a monocrystalline silicon substrate as the starting material and oxidizing the silicon substrate to convert it entirely to silica. The oxidation process is performed from both major surfaces of the silicon substrate using a conventional high-pressure oxidation system. The resulting product is an amorphous silica substrate which is expected to have superior etching characteristics for microfabrication than conventional fused silica substrates. The present invention can also be used to convert only a portion of a monocrystalline silicon substrate to silica by masking the silicon substrate and locally thinning a portion the silicon substrate prior to converting the silicon portion entirely to silica. In this case, the silica formed by oxidizing the thinned portion of the silicon substrate can be used, for example, as a window to provide optical access through the silicon substrate.

  5. Preparation and Characterization of Silica-Enoxil Nanobiocomposites

    NASA Astrophysics Data System (ADS)

    Kuzema, Pavlo O.; Laguta, Iryna V.; Stavinskaya, Oksana N.; Kazakova, Olga A.; Borysenko, Mykola V.; Lupaşcu, Tudor

    2016-02-01

    Silica-Enoxil nanobiocomposites with 13 %w of Enoxil were prepared either by mechanical mixing of corresponding powders or by sorptive modification of fumed silica powder with aqueous Enoxil solution under fluidized bed conditions. The interaction of fumed silica with Enoxil and the properties of silica-Enoxil composites have been investigated using IR spectroscopy, thermogravimetric analysis, and quantum chemistry methods, as well as by means of water absorption, Enoxil desorption, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) test. It has been shown that the main biomolecules of Enoxil composition interact with silica involving their hydroxyl groups and surface silanol groups. The water absorption of silica-Enoxil nanocomposites was found to be less than that for the individual components. The Enoxil biomolecules are readily and completely desorbed from silica surface into water, and the antioxidant activity of desorbed Enoxil is practically the same as that for the just dissolved one.

  6. Water Vapor Effects on Silica-Forming Ceramics

    NASA Technical Reports Server (NTRS)

    Opila, E. J.; Greenbauer-Seng, L. (Technical Monitor)

    2000-01-01

    Silica-forming ceramics such as SiC and Si3N4 are proposed for applications in combustion environments. These environments contain water vapor as a product of combustion. Oxidation of silica-formers is more rapid in water vapor than in oxygen. Parabolic oxidation rates increase with the water vapor partial pressure with a power law exponent value close to one. Molecular water vapor is therefore the mobile species in silica. Rapid oxidation rates and large amounts of gases generated during the oxidation reaction in high water vapor pressures may result in bubble formation in the silica and nonprotective scale formation. It is also shown that silica reacts with water vapor to form Si(OH)4(g). Silica volatility has been modeled using a laminar flow boundary layer controlled reaction equation. Silica volatility depends on the partial pressure of water vapor, the total pressure, and the gas velocity. Simultaneous oxidation and volatilization reactions have been modeled with paralinear kinetics.

  7. Neoproterozoic extension in the greater dharwar craton: A reevaluation of the "betsimisaraka suture" in madagascar

    USGS Publications Warehouse

    Tucker, R.D.; Roig, J.-Y.; Delor, C.; Amlin, Y.; Goncalves, P.; Rabarimanana, M.H.; Ralison, A.V.; Belcher, R.W.

    2011-01-01

    The Precambrian shield of Madagascar is reevaluated with recently compiled geological data and new U-Pb sensitive high-resolution ion microprobe (SHRIMP) geochronology. Two Archean domains are recognized: the eastern Antongil-Masora domain and the central Antananarivo domain, the latter with distinctive belts of metamafic gneiss and schist (Tsaratanana Complex). In the eastern domain, the period of early crust formation is extended to the Paleo-Mesoarchean (3.32-3.15 Ga) and a supracrustal sequence (Fenerivo Group), deposited at 3.18 Ga and metamorphosed at 2.55 Ga, is identified. In the central domain, a Neoarchean period of high-grade metamorphism and anatexis that affected both felsic (Betsiboka Suite) and mafic gneisses (Tsaratanana Complex) is documented. We propose, therefore, that the Antananarivo domain was amalgamated within the Greater Dharwar Craton (India + Madagascar) by a Neoarchean accretion event (2.55-2.48 Ga), involving emplacement of juvenile igneous rocks, high-grade metamorphism, and the juxtaposition of disparate belts of mafic gneiss and schist (metagreenstones). The concept of the "Betsimisaraka suture" is dispelled and the zone is redefined as a domain of Neoproterozoic metasedimentary (Manampotsy Group) and metaigneous rocks (Itsindro-Imorona Suite) formed during a period of continental extension and intrusive igneous activity between 840 and 760 Ma. Younger orogenic convergence (560-520 Ma) resulted in east-directed overthrusting throughout south Madagascar and steepening with local inversion of the domain in central Madagascar. Along part of its length, the Manampotsy Group covers the boundary between the eastern and central Archean domains and is overprinted by the Angavo-Ifanadiana high-strain zone that served as a zone of crustal weakness throughout Cretaceous to Recent times.

  8. A reevaluation of the timing and causes of high lake phases in the Lake Michigan basin

    USGS Publications Warehouse

    Hansel, A.K.; Mickelson, D.M.

    1988-01-01

    Radiocarbon age control on the type Glenwood, Calumet, and Toleston shoreline features and on the abandoned Chicago outlet at the south end of the Lake Michigan basin provides a basis for reevaluating the timing and causes of high lake phases in the basin. Radiocarbon dates suggest that Glenwood-level (195 m) shoreline features formed between 14,100 and 12,700 yr B.P. (Glenwood I and II phases), Calumet-level (189 m) between 12,700 and 11,000 yr B.P. (Calumet I and II phases), and Toleston-level (184.5 m) between 5000 and 4000 yr B.P. (Nipissing phase), and that the Chicago outlet was cut to its present level (180 m) on bedrock while the lake was at the Glenwood level. This new chronology is inconsistent with J H. Bretz' hypothesis ((1951) American Journal of Science249, 401-429) that the progressive lowering of lake level resulted from episodic down-cutting of the outlet. Instead, the changes in lake level appear to relate to changes in the amount of glacial meltwater and precipitation entering the basin. We hypothesize that the Glenwood phases correspond with times when discharge from the Huron and Erie basins also entered the Lake Michigan basin (Lake Border and early Port Huron glacial phases), the Calumet phases with times when drainage was from the Lake Michigan basin alone (late Port Huron and Two Rivers glacial phases), and the Nipissing phase with the postglacial middle Holocene transgression caused by differential uplift in the basin. Estimates of relative net inputs to the basin during the Glenwood, Calumet, and Nipissing lake phases are consistent with estimates of relative outputs (i.e., discharge through the Chicago outlet); the magnitude of relative differences in inputs and outputs between phases is sufficient to explain lake-level changes of 4.5 to 6 m. ?? 1988.

  9. Doppler lidar atmospheric wind sensor: reevaluation of a 355-nm incoherent Doppler lidar.

    PubMed

    Rees, D; McDermid, I S

    1990-10-01

    We reevaluate the performance of an incoherent Doppler lidar system operating at 354.7 nm, based on recent but well-proven Nd:YAG laser technology and currently available optical sensors. For measurements in the lower troposphere, up to ~5 km altitude, and also in the Junge-layer of the lower stratosphere, a wind component accuracy of +/- 2 m/s and a vertical resolution of 1 km should be obtained with a single pulse from a 1-J laser, operating at Polar Platform altitudes (700-850 km) and high scan angles (55 degrees ). For wind measurements in the upper troposphere (above ~5 km altitude) and stratosphere (above and below the Junge layer) the concentration of scatterers is much lower and higher energies would be required to maintain +/-2m/s accuracy and 1 km vertical resolution, using single laser pulses. Except for the region in the vicinity of the tropopause (10 km altitude), a 5-J pulse would be appropriate to make measurements in these regions. The worst case is encountered near 10 km altitude, where we calculate that a 15-J pulse would be required. To reduce this energy requirement, we would propose to degrade the altitude resolution from 1 km to 2-3 km, and also to consider averaging multiple pulses. Degrading the vertical and horizontal resolution could provide an acceptable method of obtaining the required wind accuracy without the penalty of using a laser of higher output power. We believe that a Doppler lidar system, employing a near ultraviolet laser with a pulse energy of 5 J, could achieve the performance objectives required by the major potential users of a global space-borne wind observing system.

  10. A Reevaluation of Airborne HO(x) Observations from NASA Field Campaigns

    NASA Technical Reports Server (NTRS)

    Olson, Jennifer; Crawford, James H.; Chen, Gao; Brune, William H.; Faloona, Ian C.; Tan, David; Harder, Hartwig; Martinez, Monica

    2006-01-01

    In-situ observations of tropospheric HO(x) (OH and HO2) obtained during four NASA airborne campaigns (SUCCESS, SONEX, PEM-Tropics B and TRACE-P) are reevaluated using the NASA Langley time-dependent photochemical box model. Special attention is given to previously diagnosed discrepancies between observed and predicted HO2 which increase with higher NO(x) levels and at high solar zenith angles. This analysis shows that much of the model discrepancy at high NO(x) during SUCCESS can be attributed to modeling observations at time-scales too long to capture the nonlinearity of HO(x) chemistry under highly variable conditions for NO(x). Discrepancies at high NO(x) during SONEX can be moderated to a large extent by complete use of all available precursor observations. Differences in kinetic rate coefficients and photolysis frequencies available for previous studies versus current recommendations also explain some of the disparity. Each of these causes is shown to exert greater influence with increasing NO(x) due to both the chemical nonlinearity between HO(x) and NO(x) and the increased sensitivity of HO(x) to changes in sources at high NO(x). In contrast, discrepancies at high solar zenith angles will persist until an adequate nighttime source of HO(x) can be identified. It is important to note that this analysis falls short of fully eliminating the issue of discrepancies between observed and predicted HO(x) for high NO(x) environments. These discrepancies are not resolved with the above causes in other data sets from ground-based field studies. Nevertheless, these results highlight important considerations in the application of box models to observationally based predictions of HO(x) radicals.

  11. A Reevaluation of the Morphology, Paleoecology, and Phylogenetic Relationships of the Enigmatic Walrus Pelagiarctos

    PubMed Central

    Boessenecker, Robert W.; Churchill, Morgan

    2013-01-01

    Background A number of aberrant walruses (Odobenidae) have been described from the Neogene of the North Pacific, including specialized suction-feeding and generalist fish-eating taxa. At least one of these fossil walruses has been hypothesized to have been a specialized predator of other marine mammals, the middle Miocene walrus Pelagiarctos thomasi from the Sharktooth Hill Bonebed of California (16.1–14.5 Ma). Methodology/Principal Findings A new specimen of Pelagiarctos from the middle Miocene “Topanga” Formation of southern California (17.5–15 Ma) allows a reassessment of the morphology and feeding ecology of this extinct walrus. The mandibles of this new specimen are robust with large canines, bulbous premolars with prominent paraconid, metaconid, hypoconid cusps, crenulated lingual cingula with small talonid basins, M2 present, double-rooted P3–M1, single-rooted P1 and M2, and a P2 with a bilobate root. Because this specimen lacks a fused mandibular symphysis like Pelagiarctos thomasi, it is instead referred to Pelagiarctos sp. This specimen is more informative than the fragmentary holotype of Pelagiarctos thomasi, permitting Pelagiarctos to be included within a phylogenetic analysis for the first time. Analysis of a matrix composed of 90 cranial, dental, mandibular and postcranial characters indicates that Pelagiarctos is an early diverging walrus and sister to the late Miocene walrus Imagotaria downsi. We reevaluate the evidence for a macropredatory lifestyle for Pelagiarctos, and we find no evidence of specialization towards a macrophagous diet, suggesting that Pelagiarctos was a generalist feeder with the ability to feed on large prey. Conclusions/Significance This new specimen of Pelagiarctos adds to the knowledge of this problematic taxon. The phylogenetic analysis conclusively demonstrates that Pelagiarctos is an early diverging walrus. Pelagiarctos does not show morphological specializations associated with macrophagy, and was likely a

  12. Re-evaluation of the amplitude-force relationship of trunk muscles.

    PubMed

    Huebner, Agnes; Faenger, Bernd; Scholle, Hans-Christoph; Anders, Christoph

    2015-04-13

    Amplitude-force relationships of major trunk muscles are established in terms of curve characteristics, but up to now were not normalized with respect to maximum voluntary contraction (MVC) force levels. The study therefore aims at a re-evaluation of trunk muscle amplitude-force relationship data according to MVC. Surface EMG of five major trunk muscles was taken from 50 healthy subjects of both sexes (age 20-40 years). All tasks were performed in a device where submaximal loads on the trunk were applied by gradually tilting the subjects in sagittal plane to horizontal position. MVC flexion and extension forces were determined in upright position using an additional harness over the subject's shoulders. Furthermore, the subject's upper body mass (UBM) was obtained during forward tilt to horizontal. MVC to UBM ratio was calculated, corrected by the actual tilt angle, and these linearly estimated values compared with the measured relative values according to MVC. All abdominal muscles confirmed the known non-linear amplitude-force relationship. At low load levels the linearly estimated values overestimated the measured ones and, at higher load levels, underestimated the true stress levels considerably. Back muscles confirmed the known linear curve shape, but for the longissimus muscle at L1 level measured data was always below estimated values. With increasing load, muscular stress of abdominal muscles changes from overestimated towards considerably underestimated values if expected stress levels are based on linear interpolation. Major back muscles' activation levels are nearly linear, but the amplitude-force relationship values seem overestimated for longissimus.

  13. Reevaluation of the developmental toxicity of dieldrin by the use of fertilized Japanese quail eggs.

    PubMed

    Kamata, Ryo; Shiraishi, Fujio; Takahashi, Shinji; Shimizu, Akira; Shiraishi, Hiroaki

    2010-06-01

    To reevaluate the toxicity of the organochlorine insecticide and persistent organic pollutant dieldrin and confirm its impact on development, an exposure trial using bird eggs was performed. Dieldrin at concentrations of 10-100 microg/g of egg was injected into the yolks of Japanese quail (Coturnix japonica) eggs. Hatchlings from the eggs were raised to sexual maturity and multiple tests to detect the harmful effects of dieldrin were conducted. Dieldrin at 100 microg/g decreased egg hatchability by 50.0% (vehicle control, 86.7%), although embryogenesis even in unhatched eggs treated with high doses of dieldrin was normal. In safely hatched chicks, dose-dependent early death with tonic seizure was observed and all birds exposed to 100 microg/g died within 3 days. Other significant alterations in hatchlings were enlargement of the whole brain, decreases in mRNA expressions of tryptophan hydroxylase in the brainstem and cholesterol side-chain cleavage in the male gonad, and increases in mRNA expressions of cytochrome P450 1A and 2C18 in the liver. For mature birds (males at 5 weeks and females at 10 weeks of age), impairment of eggshell formation such as reduced eggshell mass and eggshell thinning, increases in the body mass of males and the liver mass of females and increases in serum total cholesterol and triglyceride concentrations were observed. The results indicated that not only does the neurotoxicity of dieldrin bring early death, but its effects on reproductive and hepatic functions (detected as gene transcriptional changes in hatchlings) persist harmfully after maturity. PMID:20211759

  14. The pathogenesis of syringomyelia: a re-evaluation of the elastic-jump hypothesis.

    PubMed

    Elliott, N S J; Lockerby, D A; Brodbelt, A R

    2009-04-01

    Syringomyelia is a disease in which fluid-filled cavities, called syrinxes, form in the spinal cord causing progressive loss of sensory and motor functions. Invasive monitoring of pressure waves in the spinal subarachnoid space implicates a hydrodynamic origin. Poor treatment outcomes have led to myriad hypotheses for its pathogenesis, which unfortunately are often based on small numbers of patients due to the relative rarity of the disease. However, only recently have models begun to appear based on the principles of mechanics. One such model is the mathematically rigorous work of Carpenter and colleagues (2003, "Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 1: Basic Theory," ASME J. Biomech. Eng., 125(6), pp. 852-856; 2003, "Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 2: Mechanisms for the Pathogenesis of Syringomyelia," ASME J. Biomech. Eng., 125(6), pp. 857-863). They suggested that a pressure wave due to a cough or sneeze could form a shocklike elastic jump, which when incident at a stenosis, such as a hindbrain tonsil, would generate a transient region of high pressure within the spinal cord and lead to fluid accumulation. The salient physiological parameters of this model were reviewed from the literature and the assumptions and predictions re-evaluated from a mechanical standpoint. It was found that, while the spinal geometry does allow for elastic jumps to occur, their effects are likely to be weak and subsumed by the small amount of viscous damping present in the subarachnoid space. Furthermore, the polarity of the pressure differential set up by cough-type impulses opposes the tenets of the elastic-jump hypothesis. The analysis presented here does not support the elastic-jump hypothesis or any theory reliant on cough-based pressure impulses as a mechanism for the pathogenesis of syringomyelia. PMID:19275445

  15. Exploring the uncultured microeukaryote majority in the oceans: reevaluation of ribogroups within stramenopiles.

    PubMed

    Massana, Ramon; del Campo, Javier; Sieracki, Michael E; Audic, Stéphane; Logares, Ramiro

    2014-04-01

    Molecular surveys in planktonic marine systems have unveiled a large novel diversity of small protists. A large part of this diversity belongs to basal heterotrophic stramenopiles and is distributed in a set of polyphyletic ribogroups (described from rDNA sequences) collectively named as MAST (MArine STramenopiles). In the few groups investigated, MAST cells are globally distributed and abundant bacterial grazers, therefore having a putatively large impact on marine ecosystem functioning. The main aim of this study is to reevaluate the MAST ribogroups described so far and to determine whether additional groups can be found. For this purpose, we used traditional and state-of-the-art molecular tools, combining 18S rDNA sequences from publicly available clone libraries, single amplified genomes (SAGs) of planktonic protists, and a pyrosequencing survey from coastal waters and sediments. Our analysis indicated a final set of 18 MAST groups plus 5 new ribogroups within Ochrophyta (named as MOCH). The MAST ribogroups were then analyzed in more detail. Seven were typical of anoxic systems and one of oxic sediments. The rest were clearly members of oxic marine picoplankton. We characterized the genetic diversity within each MAST group and defined subclades for the more diverse (46 subclades in 8 groups). The analyses of sequences within subclades revealed further ecological specializations. Our data provide a renovated framework for phylogenetic classification of the numerous MAST ribogroups and support the notion of a tight link between phylogeny and ecological distribution. These diverse and largely uncultured protists are widespread and ecologically relevant members of marine microbial assemblages.

  16. Re-Evaluation of Sarcolemma Injury and Muscle Swelling in Human Skeletal Muscles after Eccentric Exercise

    PubMed Central

    Yu, Ji-Guo; Liu, Jing-Xia; Carlsson, Lena; Thornell, Lars-Eric; Stål, Per S.

    2013-01-01

    The results regarding the effects of unaccustomed eccentric exercise on muscle tissue are often conflicting and the aetiology of delayed onset muscle soreness (DOMS) induced by eccentric exercise is still unclear. This study aimed to re-evaluate the paradigm of muscular alterations with regard to muscle sarcolemma integrity and fibre swelling in human muscles after voluntary eccentric exercise leading to DOMS. Ten young males performed eccentric exercise by downstairs running. Biopsies from the soleus muscle were obtained from 6 non-exercising controls, 4 exercised subjects within 1 hour and 6 exercised subjects at 2–3 days and 7–8 days after the exercise. Muscle fibre sarcolemma integrity, infiltration of inflammatory cells and changes in fibre size and fibre phenotype composition as well as capillary supply were examined with specific antibodies using enzyme histochemistry and immunohistochemistry. Although all exercised subjects experienced DOMS which peaked between 1.5 to 2.5 days post exercise, no significant sarcolemma injury or inflammation was detected in any post exercise group. The results do not support the prevailing hypothesis that eccentric exercise causes an initial sarcolemma injury which leads to subsequent inflammation after eccentric exercise. The fibre size was 24% larger at 7–8 days than at 2–3 days post exercise (p<0.05). In contrast, the value of capillary number per fibre area tended to decrease from 2–3 days to 7–8 days post exercise (lower in 5 of the 6 subjects at 7–8 days than at 2–3 days; p<0.05). Thus, the increased fibre size at 7–8 days post exercise was interpreted to reflect fibre swelling. Because the fibre swelling did not appear at the time that DOMS peaked (between 1.5 to 2.5 days post exercise), we concluded that fibre swelling in the soleus muscle is not directly associated with the symptom of DOMS. PMID:23614012

  17. Silica fractionation and reactivity in soils

    NASA Astrophysics Data System (ADS)

    Unzué Belmonte, Dácil; Barão, Lúcia; Vandevenne, Floor; Schoelynck, Jonas; Struyf, Eric; Meire, Patrick

    2014-05-01

    The Si cycle is a globally important biogeochemical cycle, with strong connections to other biogeochemical cycles, including C. Silica is taken up by plants to form protective structures called phytoliths, which become a part of the soil and contribute strongly to soil Si cycling upon litter burial. Different silica fractions are found in soils, with phytoliths among the most easily soluble, especially compared to silicate minerals. A whole set of secondary non-biogenic fractions exist, that also have a high reactivity (adsorbed Si, reactive secondary minerals…). A good characterization of the different fractions of reactive silica is crucial to move forward knowledge on ecosystem Si cycling, which has been recognized in the last decade as crucial for terrestrial Si fluxes. A new method to analyze the different fractions of silica in soils has been described by Koning et al. (2002) and adapted by our research team (Barão et al. 2013). Using a continuous extraction of Si and aluminum in 0.5M NaOH, biogenic and non-biogenic reactive fractions are separated based on their Si/Al ratios and their reactivity in NaOH. Applying this new method I will investigate three emerging ideas on how humans can affect directly terrestrial Si fluxes. -Land use. I expect strong silica fractionation and reactivity differences in different land uses. These effects due to agricultural and forestry management have already been shown earlier in temperate soils (Vandevenne et al. 2012). Now we will test this hypothesis in recently deforested soils, in the south of Brazil. 'Pristine' forest, managed forest and tobacco field soils (with and without rotation crops) will be studied. This research belongs to an interdisciplinary project on soils and global change. -Fire. According to the IPCC report, extreme events such as fires (number and intensity) would increase due to climate change. We analyzed litter from spruce forest, beech forest and peat soils at two burning levels, after 350°C and

  18. Positronium reemission yield from mesostructured silica films

    NASA Astrophysics Data System (ADS)

    Liszkay, L.; Corbel, C.; Perez, P.; Desgardin, P.; Barthe, M.-F.; Ohdaira, T.; Suzuki, R.; Crivelli, P.; Gendotti, U.; Rubbia, A.; Etienne, M.; Walcarius, A.

    2008-02-01

    The reemission yield of ortho-positronium (o-Ps) into vacuum outside mesoporous silica films on glass is measured in reflection mode with a specially designed lifetime (LT) spectrometer. Values as high as 40% are found. The intensity of the 142ns vacuum LT is recorded as a function of reemission depth. The LT depth profiling is correlated to the 2γ and 3γ energy ones to determine the annihilation characteristics inside the films. Positron lifetime in capped films is used to determine the pore size. For the first time, a set of consistent fingerprints for positronium annihilation, o-Ps reemission into vacuum, and pore size, is directly determined in surfactant-templated mesoporous silica films.

  19. Multipod-like silica/polystyrene clusters

    NASA Astrophysics Data System (ADS)

    Désert, Anthony; Morele, Jérémy; Taveau, Jean-Christophe; Lambert, Olivier; Lansalot, Muriel; Bourgeat-Lami, Elodie; Thill, Antoine; Spalla, Olivier; Belloni, Luc; Ravaine, Serge; Duguet, Etienne

    2016-03-01

    Multipod-like clusters composed of a silica core and PS satellites are prepared according to a seeded-growth emulsion polymerization of styrene in the presence of size-monodisperse silica particles previously surface-modified with methacryloxymethyltriethoxysilane. Tuning the diameter and concentration of the silica seeds affords homogeneous batches of tetrapods, hexapods, octopods, nonapods and dodecapods with morphology yields as high as 80%. Three-dimensional reconstructions by cryo-electron tomography are presented on large fields for the first time to show the high symmetry and regularity of the clusters demonstrating the good control of the synthesis process. These synthesis experiments are visited again digitally, in order to successfully refine an original simulation model and better understand the correlation between the history of the cluster growth and the final composition of the cluster mixture. Finally, using the model as a predictive tool and varying the extra experimental conditions, e.g. the composition of the surfactant mixture and the styrene concentration, result in trapping other cluster morphologies, such as tripods.Multipod-like clusters composed of a silica core and PS satellites are prepared according to a seeded-growth emulsion polymerization of styrene in the presence of size-monodisperse silica particles previously surface-modified with methacryloxymethyltriethoxysilane. Tuning the diameter and concentration of the silica seeds affords homogeneous batches of tetrapods, hexapods, octopods, nonapods and dodecapods with morphology yields as high as 80%. Three-dimensional reconstructions by cryo-electron tomography are presented on large fields for the first time to show the high symmetry and regularity of the clusters demonstrating the good control of the synthesis process. These synthesis experiments are visited again digitally, in order to successfully refine an original simulation model and better understand the correlation between the

  20. Carbon nanomaterials in silica aerogel matrices

    SciTech Connect

    Hamilton, Christopher E; Chavez, Manuel E; Duque, Juan G; Gupta, Gautam; Doorn, Stephen K; Dattelbaum, Andrew M; Obrey, Kimberly A D

    2010-01-01

    Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWCNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWCNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWCNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

  1. Thermoporometry characterization of silica microparticles and nanowires.

    PubMed

    Wu, Jiaxin; Zheng, Han; Cheng, He; Zhou, L; Leong, K C; Rajagopalan, R; Too, H P; Choi, W K

    2014-03-01

    We present the results of a systematic study on the porosity of silica microparticles and nanowires prepared by glancing angle deposition-metal-assisted chemical etching (GLAD-MACE) and interference lithography-metal-assisted chemical etching (IL-MACE) techniques using the thermoporometry (TPM) method. Good agreement was obtained between our TPM results and published data provided by the suppliers of silica microparticles. TPM characterization of the GLAD-MACE and IL-MACE nanowires was carried out on the basis of parameters obtained from TPM experiments on microparticles. Our nanowires showed a similar trend but lower values of the pore volume and surface area than nanowires prepared by MACE with AgNO3 solution. We attribute the enhanced bioanalysis performance of the GLAD-MACE nanowires based devices to the increased pore volume and total surface area of the nanowires.

  2. Stress relaxation of vitreous silica on irradiation

    SciTech Connect

    Primak, W.

    1982-11-01

    The radiation-induced stress relaxation which is observed on ion bombardment of vitreous silica is described as a viscoelastic behavior in which the apparent viscosity is reduced to approx.10/sup 14/ Poise during irradiation and then increases rapidly by 4 or 5 orders of magnitude on cessation or interruption of irradiation. The bombarded layer appears to possess a viscosity approx.10/sup 19/ Poise, lower than would be expected for normal vitreous silica. On electron bombardment the viscosity is also reduced, but not as greatly as an ion bombardment, yet sufficiently to result in the whole radiation-induced volume contraction being realized perpendicularly to the surface, as has been found for ion bombardment. The maximum elastic stored energy which can be realized is but a fraction of a calorie per gram, hence the reported values of 200 cal/g would seem to be associated with the fragmentation of the network responsible for the reduced viscosity.

  3. Drug release from ordered mesoporous silicas.

    PubMed

    Doadrio, Antonio L; Salinas, Antonio J; Sánchez-Montero, José M; Vallet-Regí, M

    2015-01-01

    The state-of-the-art in the investigation of drugs release from Silica-based ordered Mesoporous Materials (SMMs) is reviewed. First, the SMM systems used like host matrixes are described. Then, the model drugs studied until now, including their pharmacological action, structure and the mesoporous matrix employed for each drug, are comprehensively listed. Next, the factors influencing the release of drugs from SMMs and the strategies used to control the drug delivery, specially the chemical functionalization of the silica surface, are discussed. In addition, how all these factors were gathered in a kinetic equation that describes the drug release from the mesoporous matrixes is explained. The new application of molecular modeling and docking in the investigation of the drug delivery mechanisms from SMMs is also presented. Finally, the new approaches under investigation in this field are mentioned including the design of smart stimuli-responsive materials and other recent proposals for a future investigation. PMID:26549760

  4. Bright photoluminescent hybrid mesostructured silica nanoparticles.

    PubMed

    Miletto, Ivana; Bottinelli, Emanuela; Caputo, Giuseppe; Coluccia, Salvatore; Gianotti, Enrica

    2012-07-28

    Bright photoluminescent mesostructured silica nanoparticles were synthesized by the incorporation of fluorescent cyanine dyes into the channels of MCM-41 mesoporous silica. Cyanine molecules were introduced into MCM-41 nanoparticles by physical adsorption and covalent grafting. Several photoluminescent nanoparticles with different organic loadings have been synthesized and characterized by X-ray powder diffraction, high resolution transmission electron microscopy and nitrogen physisorption porosimetry. A detailed photoluminescence study with the analysis of fluorescence lifetimes was carried out to elucidate the cyanine molecules distribution within the pores of MCM-41 nanoparticles and the influence of the encapsulation on the photoemission properties of the guests. The results show that highly stable photoluminescent hybrid materials with interesting potential applications as photoluminescent probes for diagnostics and imaging can be prepared by both methods. PMID:22706523

  5. Coupled reactions and silica diffusion during serpentinization

    NASA Astrophysics Data System (ADS)

    Ogasawara, Yuichi; Okamoto, Atsushi; Hirano, Nobuo; Tsuchiya, Noriyoshi

    2013-10-01

    Silica activity is one of the key factors in controlling reaction paths of serpentinization. We conducted hydrothermal experiments in the olivine (Ol)-orthopyroxene (Opx)-H2O system at 250 °C and at a vapor-saturated pressure of 3.98 MPa to explore the role of silica diffusion in aqueous fluids during serpentinization. Olivine (Fo91), orthopyroxene (En91), or their composite powders (with Ol/Opx/Ol zones) were set in tube-in-tube vessels, and solution chemistry and the extent of serpentinization were analyzed in detail. In the Ol-H2O experiments, the product changed from serpentine + magnetite to serpentine + brucite + magnetite, accompanied by a Si-drop in the solutions. Serpentinization proceeded uniformly throughout the reaction tube, indicating that the supply of water was not the rate-determining process. In the Opx-H2O experiments, orthopyroxenes were dissolved along the cleavages, and the amount of newly formed serpentine was very small. The silica activity of the solutions in the Opx-H2O experiments was 1-3 orders higher than in the Ol-H2O experiments. In the Ol-Opx-H2O experiments, serpentinization proceeded in both the Ol and Opx zones. In the Opx zone, the extent of serpentinization was constant, whereas in the Ol zone, serpentinization was most extensive along the boundary between the Ol and Opx zones, and it decreased gradually away from the boundary. Serpentinization in the Ol-Opx-H2O experiments was modeled simply by coupled processes involving silica diffusion and two serpentinization reactions: a silica-consuming reaction after olivine and a silica-releasing reaction after orthopyroxene. The spatial pattern of the extent of serpentinization was controlled by the diffusion coefficient of silica in aqueous solution, DSiO2,aq, and the apparent reaction rate constants k‧Ol in the olivine zone, and k‧Opx in the orthopyroxene zone. Assuming DSiO2,aq = 2.0 × 10-4 cm2/s, the observed variation in the extent of serpentinization after a run of 1512 h

  6. Opaline silica in young deposits on Mars

    NASA Astrophysics Data System (ADS)

    Milliken, R. E.; Swayze, G. A.; Arvidson, R. E.; Bishop, J. L.; Clark, R. N.; Ehlmann, B. L.; Green, R. O.; Grotzinger, J. P.; Morris, R. V.; Murchie, S. L.; Mustard, J. F.; Weitz, C.

    2008-11-01

    High spatial and spectral resolution reflectance data acquiredby the Mars Reconnaissance Orbiter Compact Reconnaissance ImagingSpectrometer for Mars (CRISM) instrument reveal the presenceof H2O- and SiOH-bearing phases on the Martian surface. Thespectra are most consistent with opaline silica and glass alteredto various degrees, confirming predictions based on geochemicalexperiments and models that amorphous silica should be a commonweathering product of the basaltic Martian crust. These materialsare associated with hydrated Fe sulfates, including H3O-bearingjarosite, and are found in finely stratified deposits exposedon the floor of and on the plains surrounding the Valles Marineriscanyon system. Stratigraphic relationships place the formationage of these deposits in the late Hesperian or possibly theAmazonian, implying that aqueous alteration continued to bean important and regionally extensive process on Mars duringthat time.

  7. Water evaporation in silica colloidal deposits.

    PubMed

    Peixinho, Jorge; Lefèvre, Grégory; Coudert, François-Xavier; Hurisse, Olivier

    2013-10-15

    The results of an experimental study on the evaporation and boiling of water confined in the pores of deposits made of mono-dispersed silica colloidal micro-spheres are reported. The deposits are studied using scanning electron microscopy, adsorption of nitrogen, and adsorption of water through attenuated total reflection-infrared spectroscopy. The evaporation is characterized using differential scanning calorimetry and thermal gravimetric analysis. Optical microscopy is used to observe the patterns on the deposits after evaporation. When heating at a constant rate and above boiling temperature, the release of water out of the deposits is a two step process. The first step is due to the evaporation and boiling of the surrounding and bulk water and the second is due to the desorption of water from the pores. Additional experiments on the evaporation of water from membranes having cylindrical pores and of heptane from silica deposits suggest that the second step is due to the morphology of the deposits.

  8. Silica removal in industrial effluents with high silica content and low hardness.

    PubMed

    Latour, Isabel; Miranda, Ruben; Blanco, Angeles

    2014-01-01

    High silica content of de-inked paper mill effluents is limiting their regeneration and reuse after membrane treatments such as reverse osmosis (RO). Silica removal during softening processes is a common treatment; however, the effluent from the paper mill studied has a low hardness content, which makes the addition of magnesium compounds necessary to increase silica removal. Two soluble magnesium compounds (MgCl₂∙6H₂O and MgSO₄∙7H₂O) were tested at five dosages (250-1,500 mg/L) and different initial pH values. High removal rates (80-90%) were obtained with both products at the highest pH tested (11.5). With these removal efficiencies, it is possible to work at high RO recoveries (75-85%) without silica scaling. Although pH regulation significantly increased the conductivity of the waters (at pH 11.5 from 2.1 to 3.7-4.0 mS/cm), this could be partially solved by using Ca(OH)₂ instead of NaOH as pH regulator (final conductivity around 3.0 mS/cm). Maximum chemical oxygen demand (COD) removal obtained with caustic soda was lower than with lime (15 vs. 30%). Additionally, the combined use of a polyaluminum coagulant during the softening process was studied; the coagulant, however, did not significantly improve silica removal, obtaining a maximum increase of only 10%. PMID:24777323

  9. Silica Foams for Fire Prevention and Firefighting.

    PubMed

    Vinogradov, Alexander V; Kuprin, D S; Abduragimov, I M; Kuprin, G N; Serebriyakov, Evgeniy; Vinogradov, Vladimir V

    2016-01-13

    We report the new development of fire-extinguishing agents employing the latest technology of fighting and preventing fires. The in situ technology of fighting fires and explosions involves using large-scale ultrafast-gelated foams, which possess new properties and unique characteristics, in particular, exceptional thermal stability, mechanical durability, and full biocompatibility. We provide a detailed description of the physicochemical processes of silica foam formation at the molecular level and functional comparison with current fire-extinguishing and fire-fighting agents. The new method allows to produce controllable gelation silica hybrid foams in the range from 2 to 30 s up to 100 Pa·s viscosity. Chemical structure and hierarchical morphology obtained by scanning electron microscopy and transmission electron microscopy images develop thermal insulation capabilities of the foams, reaching a specific heat value of more than 2.5 kJ/(kg·°C). The produced foam consists of organized silica nanoparticles as determined by X-ray photoelectron spectroscopy and X-ray diffraction analysis with a narrow particle size distribution of ∼10-20 nm. As a result of fire-extinguishing tests, it is shown that the extinguishing efficiency exhibited by silica-based sol-gel foams is almost 50 times higher than that for ordinary water and 15 times better than that for state-of-the-art firefighting agent aqueous film forming foam. The biodegradation index determined by the time of the induction period was only 3 d, while even for conventional foaming agents this index is several times higher.

  10. Crystallization of hollow mesoporous silica nanoparticles.

    PubMed

    Drisko, Glenna L; Carretero-Genevrier, Adrian; Perrot, Alexandre; Gich, Martí; Gàzquez, Jaume; Rodriguez-Carvajal, Juan; Favre, Luc; Grosso, David; Boissière, Cédric; Sanchez, Clément

    2015-03-11

    Complex 3D macrostructured nanoparticles are transformed from amorphous silica into pure polycrystalline α-quartz using catalytic quantities of alkaline earth metals as devitrifying agent. Walls as thin as 10 nm could be crystallized without losing the architecture of the particles. The roles of cation size and the mol% of the incorporated devitrifying agent in crystallization behavior are studied, with Mg(2+), Ca(2+), Sr(2+) and Ba(2+) all producing pure α-quartz under certain conditions.

  11. Stabilization of Colloidal Silica Using Small Polyols

    SciTech Connect

    GULLEY, GERALD L.; MARTIN, JAMES E.

    1999-09-07

    We have discovered that small polyols are reasonably effective at stabilizing colloidal silica against aggregation, even under the conditions of high pH and salt concentration. Both quasielastic and elastic light scattering were used to show that these polyols dramatically decrease the aggregation rate of the suspension, changing the growth kinetics from diffusion-limited cluster-cluster aggregation to reaction-limited cluster-cluster aggregation. These polyols maybe useful in the treatment of tank wastes at the Hanford site.

  12. High purity silica reflective heat shield development

    NASA Technical Reports Server (NTRS)

    Blome, J. C.; Drennan, D. N.; Schmitt, R. J.

    1974-01-01

    Measurements were made of reflectance in the vacuum ultraviolet down to 0.15 micron. Scattering coefficients (S) and absorption coefficients (K) were also measured. These coefficients express the optical properties and are used directly in a thermodynamic analysis for sizing a heat shield. The effect of the thin silica melt layer formed during entry was also studied from the standpoint of trapped radiant energy.

  13. Fast Glazing of Alumina/Silica Tiles

    NASA Technical Reports Server (NTRS)

    Creedon, J. F.; Gzowski, E. R.; Wheeler, W. H.

    1986-01-01

    Technique for applying ceramic coating to fibrous silica/alumina insulation tiles prevents cracks and substantially reduces firing time. To reduce thermal stresses in tile being coated, high-temperature, shorttime firing schedule implemented. Such schedule allows coating to mature while substrate remains at relatively low temperature, reducing stress differential between coating and substrate. Technique used to repair tiles with damaged coatings and possibly used in heat-treating objects made of materials having different thermal-expansion coefficients.

  14. Electrostatic Discharge Properties of Fused Silica Coatings

    NASA Astrophysics Data System (ADS)

    Andersen, Allen; Sim, Charles; Dennison, J. R.

    2012-10-01

    The electric field value at which electrostatic discharge (ESD) occurs was studied for thin coatings of fused silica (highly disordered SiO2/SiOx) on conductive substrates, such as those encountered as optical coatings and in Si microfabrication. The electrostatic breakdown field was determined using an increasing voltage, while monitoring the leakage current. A simple parallel-plate capacitor geometry was used, under medium vacuum and at temperatures down to ˜150 K using a liquid N2 reservoir. The breakdown field, pre-breakdown arcing and I-V curves for fused silica samples are compared for ˜60 nm and ˜80 μm thick, room and low temperature, and untreated and irradiated samples. Unlike typical I-V results for polymeric insulators, the thin film silica samples did not exhibit pre-breakdown arcing, displayed transitional resistivity after initial breakdown, and in many cases showed evidence of a second discontinuity in the I-V curves. This diversity of observed discharge phenomena is discussed in terms of breakdown modes and defect generation on a microscopic scale.

  15. Novel silica-based ion exchange resin

    SciTech Connect

    1997-11-01

    Eichrom`s highly successful Diphonixo resin resembles a conventional ion exchange resin in its use of sulfonic acid ligands on a styrene- divinylbenzene matrix. Diphonix resin exhibits rapid exchange kinetics that allow economical operation of ion exchange systems. Unlike conventional resins, Diphonix resin contains chelating ligands that are diphosphonic acid groups that recognize and remove the targeted metals and reject the more common elements such as sodium, calcium and magnesium. This latter property makes Diphonix ideal for many industrial scale applications, including those involving waste treatment. For treatment of low-level, transuranic (TRU) and high- level radioactive wastes, Diphonix`s polystyrene backbone hinders its application due to radiolytic stability of the carbon-hydrogen bonds and lack of compatibility with expected vitrification schemes. Polystyrene-based Diphonix is approximately 60% carbon- hydrogen. In response to an identified need within the Department of Energy for a resin with the positive attributes of Diphonix that also exhibits greater radiolytic stability and final waste form compatibility, Eichrom has successfully developed a new, silica-based resin version of Diphonix. Target application for this new resin is for use in environmental restoration and waste management situations involving the processing of low-level, transuranic and high-level radioactive wastes. The resin can also be used for processing liquid mixed waste (waste that contains low level radioactivity and hazardous constituents) including mixed wastes contaminated with organic compounds. Silica-based Diphonix is only 10% carbon-hydrogen, with the bulk of the matrix silica.

  16. Luminescent Silica Nanoparticles for cancer diagnosis

    PubMed Central

    Montalti, Marco; Petrizza, Luca; Rampazzo, Enrico; Zaccheroni, Nelsi; Marchiò, Serena

    2015-01-01

    Fluorescence imaging techniques are becoming essential in preclinical investigations, and the research of suitable tools for in vivo measurements is gaining more and more importance and attention. Nanotechnology entered the field to try to find solutions for many limitation at the state of the art, and luminescent nanoparticles (NPs) are one of the most promising materials proposed for future diagnostic implementation. NPs constitute also a versatile platform that can allow facile multi-functionalization to perform multimodal imaging or theranostic (simultaneous diagnosis and therapy). In this contribution we have focussed our attention only on dye doped silica or silica-based NPs conjugated with targeting moieties to enable specific cancer cells imaging and differentiation, even if also a few non targeted systems have been cited and discussed for completeness. We have summarized common synthetic approaches to these materials and then surveyed the most recent imaging applications of silica-based nanoparticles in cancer. The field of theranostic is so important and stimulating that, even if it is not the central topic of this paper, we have included some significant examples. We have then concluded with short hints on systems already in clinical trials and examples of specific applications in children tumours. This review tries to describe and discuss, through focussed examples, the great potentialities of these materials in the medical field, with the aim to encourage further research to implement applications that are still rare. PMID:23458621

  17. Novel silica-based ion exchange resin

    SciTech Connect

    Gula, M.; Harvey, J.

    1996-12-31

    Shortcomings of chelating resins have been addressed by a new class of ion exchange resins called dual mechanism bifunctional polymers (DMBPs). DMBPs use hydrophilic cation exchange ligands with rapid uptake kinetics and use chelating ligands for selectivity for one or more metals; result is a resin that quickly recognizes and removes targeted metals from waste, remediation, and process streams. Eichrom`s Diphonix {reg_sign} resin is the first DMBP to be widely released as a commercial product; it is polystyrene based. Objective of this work is to synthesize commercial quantities of a silica-based ion exchange resin with the same or better metal ion selectivity, metal uptake kinetics, and acid stability as Diphonix. Feasibility was determined, however the process needs to be optimized. Studies at Eichrom and ANL of the performance of Diphonix resin over a broad range of HNO3 and HCl conditions and inorganic salt loadings are discussed together with the proposed method of incorporating similar characteristics into a silica-based resin. The new, silica-based resin functionalized with diphosphonic acid ligands can be used in environmental restoration and waste management situations involving processing of low-level, transuranic, and high-level radioactive wastes; it can also be used for processing liquid mixed waste including wastes contaminated with organic compounds.

  18. Fear but not fright: re-evaluating traumatic experience attenuates anxiety-like behaviors after fear conditioning.

    PubMed

    Costanzi, Marco; Saraulli, Daniele; Cannas, Sara; D'Alessandro, Francesca; Florenzano, Fulvio; Rossi-Arnaud, Clelia; Cestari, Vincenzo

    2014-01-01

    Fear allows organisms to cope with dangerous situations and remembering these situations has an adaptive role preserving individuals from injury and death. However, recalling traumatic memories can induce re-experiencing the trauma, thus resulting in a maladaptive fear. A failure to properly regulate fear responses has been associated with anxiety disorders, like Posttraumatic Stress Disorder (PTSD). Thus, re-establishing the capability to regulate fear has an important role for its adaptive and clinical relevance. Strategies aimed at erasing fear memories have been proposed, although there are limits about their efficiency in treating anxiety disorders. To re-establish fear regulation, here we propose a new approach, based on the re-evaluation of the aversive value of traumatic experience. Mice were submitted to a contextual-fear-conditioning paradigm in which a neutral context was paired with an intense electric footshock. Three weeks after acquisition, conditioned mice were treated with a less intense footshock (pain threshold). The effectiveness of this procedure in reducing fear expression was assessed in terms of behavioral outcomes related to PTSD (e.g., hyper-reactivity to a neutral tone, anxiety levels in a plus maze task, social avoidance, and learning deficits in a spatial water maze) and of amygdala activity by evaluating c-fos expression. Furthermore, a possible role of lateral orbitofrontal cortex (lOFC) in mediating the behavioral effects induced by the re-evaluation procedure was investigated. We observed that this treatment: (i) significantly mitigates the abnormal behavioral outcomes induced by trauma; (ii) persistently attenuates fear expression without erasing contextual memory; (iii) prevents fear reinstatement; (iv) reduces amygdala activity; and (v) requires an intact lOFC to be effective. These results suggest that an effective strategy to treat pathological anxiety should address cognitive re-evaluation of the traumatic experience mediated

  19. Recruitment processes in Baltic sprat - A re-evaluation of GLOBEC Germany hypotheses

    NASA Astrophysics Data System (ADS)

    Voss, Rüdiger; Peck, Myron A.; Hinrichsen, Hans-Harald; Clemmesen, Catriona; Baumann, Hannes; Stepputtis, Daniel; Bernreuther, Matthias; Schmidt, Jörn O.; Temming, Axel; Köster, Fritz W.

    2012-12-01

    The GLOBEC Germany program (2002-2007) had the ambitious goal to resolve the processes impacting the recruitment dynamics of Baltic sprat (Sprattus sprattus L.) by examining various factors affecting early life history stages. At the start of the research program, a number of general recruitment hypotheses were formulated, i.e. focusing on (1) predation, (2) food availability, (3) physical parameters, (4) the impact of current systems, and finally (5) the importance of top-down vs bottom-up effects. The present study synthesizes the results of field sampling (2002 and 2003), laboratory experiments, and modeling studies to re-evaluate these hypotheses for the Baltic sprat stock. Recruitment success was quite different in the 2 years investigated. Despite a lower spawning stock biomass in 2003, the total number of recruits was almost 2-fold higher that year compared to 2002. The higher recruitment success in 2003 could be attributed to enhanced survival success during the post-larval/juvenile stage, a life phase that appears to be critical for recruitment dynamics. In the state of the Baltic ecosystem during the period of investigation, we consider bottom-up control (e.g. temperature, prey abundance) to be more important than top-down control (predation mortality). This ranking in importance does not vary seasonally. Prevailing water circulation patterns and the transport dynamics of larval cohorts have a strong influence on sprat recruitment success. Pronounced transport to coastal areas is detrimental for year-class strength particularly at high sprat stock sizes. A suggested mechanism is density-dependant regulation of survival via intra- and inter-specific competition for prey in coastal areas. A documented change in larval vertical migration behavior between the early 1990s and early 2000s increased the transport potential to the coast, strengthening the coupling between inter-annual differences in the magnitude and direction of wind-driven surface currents and

  20. Reevaluation and comparison of energy source of chemosynthesis-based animals in each hydrothermal fields

    NASA Astrophysics Data System (ADS)

    Yamagami, S.; Fujikura, K.; Koito, T.; Inoue, K.; Yamanaka, T.

    2012-12-01

    Large biomass of dense benthic animals containing characteristic endemic species is often observed around seafloor cold seep and hydrothermal fluid vents. Parts of such animals rely on symbiotic microbes as their energy source. Those microbes are chemotrophic primary producer such as thioautotrophic and/or methanotrophic microbes. Therefore, it is commonly believed that those animals are supported only by geofluid that contains extremely high concentrations of reduced chemical species such as hydrogen sulfide and methane. However, geographical distribution of those animals is not limited nearby geofluid emitting area and is widely spreading around hydrothermal fields. Some communities are observed at an area where lack of detectable amount of reduced chemical species for sustaining the symbiotic animals. The purpose of this study, therefore, is reevaluation and comparison of the energy source quantitatively for chemotrophic primary production utilizing stable isotope signatures. We try to understand the origin of energy source for chemosynthesis-based benthic animals obtained from three areas, Okinawa Trough, Izu-Bonin Arc and Sagami Bay, where have different geological background and dominant animal species among each other. Samples of eight animal species were collected at the five geofluid fields, Iheya, Izena, Myojin, Suiyo and Sagami Bay, using RV/Natsushima and ROV/HyperDolphin during NT10-17 and NT11-09 cruise. In Okinawa Trough, the isotopic signature from the soft body parts of the thiotrophic animals who harbor sulfur-oxidizing microbes suggest that most of these animals assimilate not only originally geofluid-derived sulfide but also seawater-sulfate-derived sulfide through microbial sulfate-reducing activity. Furthermore, it seems that the methanotrophic species who harbor methane-oxidizing microbes do not rely only on their symbionts. It means that the animal species who harbor symbionts whether sulfur-oxidizing bacteria or methane-oxidizing bacteria

  1. REEVALUATION OF MALARIA PARASITES IN EL-FAYOUM GOVERNORATE, EGYPT USING RAPID DIAGNOSTIC TESTS (RDTS).

    PubMed

    Dahesh, Salwa M A; Mostafa, Heba I

    2015-12-01

    Malaria as a disease has been identified in Egypt since ancient times. Malaria was endemic in almost all parts of the country but prevalence showed a steady decrease by 1990, and regressed in most of the Governorates. Then by the end of 1998 till now Egypt become free from local transmission of malaria. All reported cases were imported mainly from Sudan. However, the outbreak of falciparum (1 case) and vivax (23 cases) that occurred (May 2014) in Aswan Governorate strongly indicated that malaria is reemerging in the country. El-Fayoum should be take special attention, rather than being the last residual focus. The efficient malaria vector A. sergenti, the proven vector A. pharoensis and the suspected vector A. multicolor were encountered. This work reevaluated malaria status by using RDTs in survey and Giemsa stained thick films to confirm positive cases and estimation of parasite rate, formula, densities and species, also to study the ecological and entomological efficacy factors. The result showed that out of 2044 examined persons, 14 (0.68%) were passive cases, i.e., attending themselves to El-Fayoum Malaria Units after their return from Sudan. Microscopic examination of their stained thick films obtained from MOH&P shows that 9 (64.2%) out of passive cases were positive 3 of them are P. falciparum (33.3%) and the rest P. vivax 6 (66.7%) The species formulas of P. falciparum and P. vivax were 33.3% and 66.7% respectively. Concerning the density class, only one vivax case was of low density class while the other cases were of high density class. All positive cases were males, imported from Sudan and most of them were merchants having trade activities in Sudan. All examined persons during active case detection ACD (1551) and neighborhood of detected cases NOD (479) were malaria negative by rapid diagnostic tests. The areas recording the highest number of imported cases were Abu Shanap, Aboxa (Ballona) and Kafr Aboud (Abshaway Center) but no Anopheline spp larvae

  2. REEVALUATION OF MALARIA PARASITES IN EL-FAYOUM GOVERNORATE, EGYPT USING RAPID DIAGNOSTIC TESTS (RDTS).

    PubMed

    Dahesh, Salwa M A; Mostafa, Heba I

    2015-12-01

    Malaria as a disease has been identified in Egypt since ancient times. Malaria was endemic in almost all parts of the country but prevalence showed a steady decrease by 1990, and regressed in most of the Governorates. Then by the end of 1998 till now Egypt become free from local transmission of malaria. All reported cases were imported mainly from Sudan. However, the outbreak of falciparum (1 case) and vivax (23 cases) that occurred (May 2014) in Aswan Governorate strongly indicated that malaria is reemerging in the country. El-Fayoum should be take special attention, rather than being the last residual focus. The efficient malaria vector A. sergenti, the proven vector A. pharoensis and the suspected vector A. multicolor were encountered. This work reevaluated malaria status by using RDTs in survey and Giemsa stained thick films to confirm positive cases and estimation of parasite rate, formula, densities and species, also to study the ecological and entomological efficacy factors. The result showed that out of 2044 examined persons, 14 (0.68%) were passive cases, i.e., attending themselves to El-Fayoum Malaria Units after their return from Sudan. Microscopic examination of their stained thick films obtained from MOH&P shows that 9 (64.2%) out of passive cases were positive 3 of them are P. falciparum (33.3%) and the rest P. vivax 6 (66.7%) The species formulas of P. falciparum and P. vivax were 33.3% and 66.7% respectively. Concerning the density class, only one vivax case was of low density class while the other cases were of high density class. All positive cases were males, imported from Sudan and most of them were merchants having trade activities in Sudan. All examined persons during active case detection ACD (1551) and neighborhood of detected cases NOD (479) were malaria negative by rapid diagnostic tests. The areas recording the highest number of imported cases were Abu Shanap, Aboxa (Ballona) and Kafr Aboud (Abshaway Center) but no Anopheline spp larvae

  3. Direct formation of S-nitroso silica nanoparticles from a single silica source.

    PubMed

    Chou, Hung-Chang; Chiu, Shih-Jiuan; Liu, Ying-Ling; Hu, Teh-Min

    2014-01-28

    Nitric oxide (NO) is a ubiquitous molecule in the body. Because of its multiple pathophysiologic roles, the potential for treating various diseases by the exogenous administration of NO has been under intensive investigation. However, the unstable, radical nature of NO poses a major challenge to the effective delivery of NO. Previously, silica nanoparticles synthesized by the traditional method have been developed into NO-carrying systems. In the present study, for the first time NO-carrying silica nanoparticles were prepared from a single silica precursor using a simple nanoprecipitation method. (3-Mercaptopropyl)-trimethoxysilane (MPTMS) was used as the sole silane source, which was subjected to acid-catalyzed S-nitrosation and condensation reactions in a one-pot organic phase. S-Nitroso silica nanoparticles (SNO-SiNPs) were then produced by injecting a smaller quantity of the organic phase into a larger amount of water without surfactants. Various preparation parameters were tested to obtain optimized conditions. Moreover, a phase diagram demonstrating the ouzo effect was constructed. The prepared SNO-SiNPs were spherical particles with a tunable size in the range of 100-400 nm. The nanoparticles in aqueous dispersions exhibited high colloid stability, possibly resulting from highly negatively charged surfaces. The result of solid-state (29)Si NMR shows the predominance of T(2) and T(3) silicon structures, suggesting that nanoparticles were formed from polycondensed silica species. In conclusion, NO-loaded silica nanoparticles have been directly prepared from a single silane precursor using a surfactant-free, low-energy, one-step nanoprecipitation approach. The method precludes the need for the initial formation of bare particles and subsequent functionalization steps. PMID:24410024

  4. Development of an improved toughness hyperpure silica reflective heat shield

    NASA Technical Reports Server (NTRS)

    Rusert, E. L.; Hackett, T. L.; Drennan, D. N.

    1979-01-01

    High purity three dimensionally woven silica-silica materials were evaluated for use as a tough reflective heat shield for planetary entry probes. A special weave design was selected to minimize light piping effects through the heat shield thickness. Various weave spacings were evaluated for densification efficiency with an 0.7 micron particle size high purity silica. Spectral hemispherical reflectance was measured from 0.2 to 2.5 microns at room temperature. Reflectance increases due to densification and purity of material were measured. Reflectance of 3D hyperpure silica was higher than 3D astroquartz silica for all wavelengths. Mechanical properties were measured in beam flexure and beam shear tests. Results indicated strengths lower than reported for slip cast fused silica. Low strengths were attributed to low densities achieved through vacuum impregnation.

  5. Aggregation kinetics and shear rheology of aqueous silica suspensions

    NASA Astrophysics Data System (ADS)

    Metin, Cigdem O.; Bonnecaze, Roger T.; Lake, Larry W.; Miranda, Caetano R.; Nguyen, Quoc P.

    2012-12-01

    The kinetics of aggregation of silica nanoparticle solutions as a function of NaCl and silica concentrations is studied experimentally and theoretically. Silica nanoparticles form fractal aggregates due to the collapse of the electrical double layer at high salt concentrations and resulting reduction in stabilizing repulsive force. We propose a convenient model to describe the aggregation of silica nanoparticles and the growth of their aggregate size that depends on particle size and concentration and salt concentration. The model agrees well with experimental data. The aggregation of silica nanoparticles also affects the rheology of the suspension. We propose an equilibrium approach for sediment volume fraction to determine the maximum effective packing fraction. The results for the relative viscosity of silica aggregates agree well with the proposed viscosity model, which also collapses onto a single master curve.

  6. Synthesis and surface functionalization of silica nanoparticles for nanomedicine

    NASA Astrophysics Data System (ADS)

    Liberman, Alexander; Mendez, Natalie; Trogler, William C.; Kummel, Andrew C.

    2014-09-01

    There are a wide variety of silica nanoformulations being investigated for biomedical applications. Silica nanoparticles can be produced using a wide variety of synthetic techniques with precise control over their physical and chemical characteristics. Inorganic nanoformulations are often criticized or neglected for their poor tolerance; however, extensive studies into silica nanoparticle biodistributions and toxicology have shown that silica nanoparticles may be well tolerated, and in some case are excreted or are biodegradable. Robust synthetic techniques have allowed silica nanoparticles to be developed for applications such as biomedical imaging contrast agents, ablative therapy sensitizers, and drug delivery vehicles. This review explores the synthetic techniques used to create and modify an assortment of silica nanoformulations, as well as several of the diagnostic and therapeutic applications.

  7. Synthesis and surface functionalization of silica nanoparticles for nanomedicine

    PubMed Central

    Liberman, Alexander; Mendez, Natalie; Trogler, William C.; Kummel, Andrew C.

    2014-01-01

    There are a wide variety of silica nanoformulations being investigated for biomedical applications. Silica nanoparticles can be produced using a wide variety of synthetic techniques with precise control over their physical and chemical characteristics. Inorganic nanoformulations are often criticized or neglected for their poor tolerance; however, extensive studies into silica nanoparticle biodistributions and toxicology have shown that silica nanoparticles may be well tolerated, and in some case are excreted or are biodegradable. Robust synthetic techniques have allowed silica nanoparticles to be developed for applications such as biomedical imaging contrast agents, ablative therapy sensitizers, and drug delivery vehicles. This review explores the synthetic techniques used to create and modify an assortment of silica nanoformulations, as well as several of the diagnostic and therapeutic applications. PMID:25364083

  8. Silica powders for powder evacuated thermal insulating panel and method

    DOEpatents

    Harris, Michael T.; Basaran, Osman A.; Kollie, Thomas G.; Weaver, Fred J.

    1996-01-01

    A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2/ g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

  9. Silica powders for powder evacuated thermal insulating panel and method

    DOEpatents

    Harris, Michael T.; Basaran, Osman A.; Kollie, Thomas G.; Weaver, Fred J.

    1994-01-01

    A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2 /g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

  10. Silica powders for powder evacuated thermal insulating panel and method

    DOEpatents

    Harris, M.T.; Basaran, O.A.; Kollie, T.G.; Weaver, F.J.

    1996-01-02

    A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm{sup 3} and an external surface area in the range of about 90 to 600 m{sup 2}/g is described. The silica powders are prepared by reacting a tetraalkyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders. 2 figs.

  11. Silica powders for powder evacuated thermal insulating panel and method

    DOEpatents

    Harris, Michael T.; Basaran, Osman A.; Kollie, Thomas G.; Weaver, Fred J.

    1995-01-01

    A powder evacuated thermal insulating panel using generally spherical and porous silica particles of a median size less than about 100 nanometers in diameter, a pour packing density of about 0.4 to 0.6 g/cm.sup.3 and an external surface area in the range of about 90 to 600 m.sup.2/ g is described. The silica powders are prepared by reacting a tetraakyl silicate with ammonia and water in an alcohol solvent, distilling the solution after the reaction to remove the ammonia and recover the alcohol. The resulting aqueous slurry was dried, ball-milled, and dried again to provide the silica particles with defined internal and external porosity. The nanometer size and the large external surface area of the silica particles along with the internal and external porosity of the silica particles provide powder evacuated thermal insulating panels with significantly higher R-values than obtainable using previously known silica powders.

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

    PubMed Central

    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

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

    SciTech Connect

    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. Sonochemical synthesis of silica particles and their size control

    NASA Astrophysics Data System (ADS)

    Kim, Hwa-Min; Lee, Chang-Hyun; Kim, Bonghwan

    2016-09-01

    Using an ultrasound-assisted sol-gel method, we successfully synthesized very uniformly shaped, monodisperse, and size-controlled spherical silica particles from a mixture of ethanol, water, and tetraethyl orthosilicate in the presence of ammonia as catalyst, at room temperature. The diameters of the silica particles were distributed in the range from 40 to 400 nm; their morphology was well characterized by scanning electron microscopy. The silica particle size could be adjusted by choosing suitable concentrations of ammonium hydroxide and water, which in turn determined the nucleation and growth rates of the particles during the reaction. This sonochemical-based silica synthesis offers an alternative way to produce spherical silica particles in a relatively short reaction time. Thus, we suggest that this simple, low-cost, and efficient method of preparing uniform silica particles of various sizes will have practical and wide-ranging industrial applicability.

  15. Protein adsorption enhanced radio-frequency heating of silica nanoparticles

    PubMed Central

    Wosik, Jarek; Pande, Rohit; Xie, Leiming; Ketharnath, Dhivya; Srinivasan, Srimeenakshi; Godin, Biana

    2013-01-01

    Measurements of specific-absorption-rate (SAR) of silica 30, 50, and 100 nm nanoparticles (NP) suspended in water were carried out at 30 MHz in 7 kV/m radio-frequency (rf) electric field. Size dependent, NP-suspension interface related heating of silica NP was observed. To investigate a possible mechanism of heating, bovine serum albumin was adsorbed on the surface of silica NPs in suspension. It resulted in significant enhancement of SAR when compared to bare silica NPs. A calorimetric and rf loss model was used to calculate effective conductivity of silica NP with/without adsorbed albumin as a function of silica size and albumin concentration. PMID:23964135

  16. Improvements in geothermal electric power and silica production

    DOEpatents

    Hill, J.H.; Fulk, M.M.

    Electricity is generated from hot geothermal solution by extracting heat therefrom, mineral solids which form in a so cooled geothermal solution are separated to recover minerals and facilitate reinjection of the solution into the ground. The separated solids are treated to recover silica by addition of an acid (amorphous silica precipitates) or a base (other minerals precipitate and soulble silicates are formed which are subsequently precipitated by acid neutralization). If desired, after silica is separated, other minerals can be separated and recovered.

  17. Properties of maxillofacial silicone elastomers reinforced with silica powder.

    PubMed

    Andreopoulos, A G; Evangelatou, M; Tarantili, P A

    1998-07-01

    Compounds of a silicone elastomer suitable for preparing maxillofacial prostheses, reinforced with various amounts of silica powder, have been studied for their mechanical response and wetting properties in terms of contact angle. Tensile strength and elongation at break showed an increase with increasing silica volume fraction up to 35%, whereas the Young modulus displayed small dependence on the silica content and the resistance to tear increased continuously with filler volume fraction (Vf). The wetting properties assessed via the contact angle, seemed to degrade with increasing silica Vf, but a dependence on the elastomer network density has also been recorded.

  18. Occupational exposure to crystalline silica and autoimmune disease.

    PubMed

    Parks, C G; Conrad, K; Cooper, G S

    1999-10-01

    Occupational exposure to silica dust has been examined as a possible risk factor with respect to several systemic autoimmune diseases, including scleroderma, rheumatoid arthritis, systemic lupus erythematosus, and some of the small vessel vasculitidies with renal involvement (e.g., Wegener granulomatosis). Crystalline silica, or quartz, is an abundant mineral found in sand, rock, and soil. High-level exposure to respirable silica dust can cause chronic inflammation and fibrosis in the lung and other organs. Studies of specific occupational groups with high-level silica exposure (e.g., miners) have shown increased rates of autoimmune diseases compared to the expected rates in the general population. However, some clinic- and population-based studies have not demonstrated an association between silica exposure and risk of autoimmune diseases. This lack of effect may be due to the limited statistical power of these studies to examine this association or because the lower- or moderate-level exposures that may be more common in the general population were not considered. Experimental studies demonstrate that silica can act as an adjuvant to nonspecifically enhance the immune response. This is one mechanism by which silica might be involved in the development of autoimmune diseases. Given that several different autoimmune diseases may be associated with silica dust exposure, silica dust may act to promote or accelerate disease development, requiring some other factor to break immune tolerance or initiate autoimmunity. The specific manifestation of this effect may depend on underlying differences in genetic susceptibility or other environmental exposures.

  19. Four hundred million years of silica biomineralization in land plants

    NASA Astrophysics Data System (ADS)

    Trembath-Reichert, Elizabeth; Wilson, Jonathan Paul; McGlynn, Shawn E.; Fischer, Woodward W.

    2015-04-01

    Biomineralization plays a fundamental role in the global silicon cycle. Grasses are known to mobilize significant quantities of Si in the form of silica biominerals and dominate the terrestrial realm today, but they have relatively recent origins and only rose to taxonomic and ecological prominence within the Cenozoic Era. This raises questions regarding when and how the biological silica cycle evolved. To address these questions, we examined silica abundances of extant members of early-diverging land plant clades, which show that silica biomineralization is widespread across terrestrial plant linages. Particularly high silica abundances are observed in lycophytes and early-diverging ferns. However, silica biomineralization is rare within later-evolving gymnosperms, implying a complex evolutionary history within the seed plants. Electron microscopy and X-ray spectroscopy show that the most common silica-mineralized tissues include the vascular system, epidermal cells, and stomata, which is consistent with the hypothesis that biomineralization in plants is frequently coupled to transpiration. Furthermore, sequence, phylogenetic, and structural analysis of nodulin 26-like intrinsic proteins from diverse plant genomes points to a plastic and ancient capacity for silica accumulation within terrestrial plants. The integration of these two comparative biology approaches demonstrates that silica biomineralization has been an important process for land plants over the course of their >400 My evolutionary history.

  20. Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels.

    PubMed

    Kato, Kazuaki; Matsui, Daisuke; Mayumi, Koichi; Ito, Kohzo

    2015-01-01

    A significantly soft and tough nanocomposite gel was realized by a novel network formed using cyclodextrin-based polyrotaxanes. Covalent bond formation between the cyclic components of polyrotaxanes and the surface of silica nanoparticles (15 nm diameter) resulted in an infinite network structure without direct bonds between the main chain polymer and the silica. Small-angle X-ray scattering revealed that the homogeneous distribution of silica nanoparticles in solution was maintained in the gel state. Such homogeneous nanocomposite gels were obtained with at least 30 wt % silica content, and the Young's modulus increased with silica content. Gelation did not occur without silica. This suggests that the silica nanoparticles behave as cross-linkers. Viscoelastic measurements of the nanocomposite gels showed no stress relaxation regardless of the silica content for <20% compression strain, indicating an infinite stable network without physical cross-links that have finite lifetime. On the other hand, the infinite network exhibited an abnormally low Young's modulus, ~1 kPa, which is not explainable by traditional rubber theory. In addition, the composite gels were tough enough to completely maintain the network structure under 80% compression strain. These toughness and softness properties are attributable to both the characteristic sliding of polymer chains through the immobilized cyclodextrins on the silica nanoparticle and the entropic contribution of the cyclic components to the elasticity of the gels. PMID:26664642

  1. Dissolution and analysis of amorphous silica in marine sediments.

    USGS Publications Warehouse

    Eggimann, D.W.; Manheim, F. T.; Betzer, P.R.

    1980-01-01

    The analytical estimation of amorphous silica in selected Atlantic and Antarctic Ocean sediments, the U.S.G.S. standard marine mud (MAG-1), A.A.P.G. clays, and samples from cultures of a marine diatom, Hemidiscus, has been examined. Our values for amorphous silica-rich circum-Antarctic sediments are equal to or greater than literature values, whereas our values for a set of amorphous silica-poor sediments from a transect of the N. Atlantic at 11oN, after appropriate correction for silica released from clays, are significantly lower than previous estimates from the same region. -from Authors

  2. Developing a Process for Commercial Silica Production from Geothermal Brines

    SciTech Connect

    Bourcier, W; Martin, S; Viani, B; Bruton, C

    2001-04-11

    Useful mineral by-products can be produced from geothermal brines. Although silica has many commercial uses, problems remain in producing a marketable product. We are conducting laboratory and modeling studies aimed at optimizing for rubber additive use, the properties of silica precipitates from Salton Sea and Coso-like geothermal fluids, Our goal is to develop a robust technique for producing silicas that have desirable physical and chemical properties for commercial use, while developing a generic understanding of silica precipitation that will allow extraction to be extended to additional fluid types, and to be easily modified to produce new types of marketable silica. Our experiments start with an acidified geothermal fluid similar to those treated by pH modification technology. Silica precipitation is induced by adding base and/or adding Mg or Ca salts to affect the nature of the precipitate. For the analog Salton Sea fluids, adding base alone caused silica to precipitate fairly rapidly. To date, we have characterized precipitates from experiments in which the final pH varied from 4 to 8, where NaOH and Na{sub 2}C0{sub 3} were added as bases, and CaCl{sub 2} and MgCl{sub 2} were added as salts. SEM photos of the silica precipitates from the Salton Sea and Cos0 fluids show that the silica particles are clusters of smaller silica particles down to the resolution of the SEM (about 80-100 nm in diameter). The particle sizes and surface areas of silicas from the Salton Sea and Coso analog brines are similar to the properties of the Degussa silica commonly used as a rubber additive. An evaluation of the strength of the silica-organic bond as tested by dispersion in oil (polybutadiene) was inconclusive. Neither the Degussa materials nor our laboratory precipitates dispersed readily in nor dispersed down to the fundamental particle size. Preliminary NMR data indicates that the Degussa silica has a smaller degree of silica polymerization (a slightly smaller average

  3. The properties of Portland cement-limestone-silica fume mortars

    SciTech Connect

    Zelic, J.; Krstulovic, R.; Tkalcec, E.; Krolo, P.

    2000-01-01

    This work has studied the influence of the combined action of silica fume and limestone or strength development, porosity, pore structure and morphological features in the system where 15 wt% of cement was substituted by finely ground limestone. Silica fume was added in amounts of 0, 2, 5, 8, 11 and 15 wt% on a cement basis, respectively. It has been established that limestone addition considerably increases the total porosity of mortars. However, if introduced together with silica fume up to 8 wt% of silica, porosity decreases. More than 8 wt% of silica increases the porosity again. The cement mortar containing 8 wt% of silica fume shows the highest compressive strength, the minimum value of the total porosity, and its pore size distribution curve shows a discontinuous pore structure. Limestone is taken up to the system and reacts with aluminate and ferrite phases from cement. Approximately 5 wt% is available for reaction after 120 days hydration of mortars containing no silica fume. The quantity of limestone incorporated is affected by the silica fume content. The replacement of Portland cement by 15 wt% of silica fume causes reduction both in the amount of cement and in the free CH content available for limestone chemical activity, and in this condition limestone acts only as a filler addition.

  4. Nanodiamond-Decorated Silica Spheres as a Chromatographic Material.

    PubMed

    Xue, Zuqin; Vinci, John C; Colón, Luis A

    2016-02-17

    Nanodiamond (ND) particles (∼5 nm), obtained from detonation soot, were oxidized and/or thermally hydrogenated. Both, the non-hydrogenated and hydrogenated ND particles were successfully coupled to the surface of micrometer-size organo-silica particles. A thin layer of nanodiamonds (NDs) decorating the surface of the organo-silica particles was visible on transmission electron microscopy (TEM) images. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) were used to characterize the NDs prior to coupling and to confirm attachment onto the organo-silica particles. Both, ultraviolet (UV) radiation and a chemical initiator were proved to be effective radical initiators for the ND-silica coupling reaction, although for scale-up purposes the chemical initiation was more advantageous to produce the ND-silica composite. Commercially available nanodiamond primary particles were also coupled to the surface of silica particles. The ND-containing silica particles were packed into chromatographic columns to study their initial feasibility as adsorbent material for liquid chromatography. The organo-silica particles decorated with hydrogenated NDs were shown to possess reversed phase type (i.e., hydrophobic) behavior toward the probe compounds, whereas silica particles decorated with the non-hydrogenated NDs showed polar (i.e., hydrophilic) interactions, both under liquid chromatographic conditions. PMID:26790050

  5. Four hundred million years of silica biomineralization in land plants.

    PubMed

    Trembath-Reichert, Elizabeth; Wilson, Jonathan Paul; McGlynn, Shawn E; Fischer, Woodward W

    2015-04-28

    Biomineralization plays a fundamental role in the global silicon cycle. Grasses are known to mobilize significant quantities of Si in the form of silica biominerals and dominate the terrestrial realm today, but they have relatively recent origins and only rose to taxonomic and ecological prominence within the Cenozoic Era. This raises questions regarding when and how the biological silica cycle evolved. To address these questions, we examined silica abundances of extant members of early-diverging land plant clades, which show that silica biomineralization is widespread across terrestrial plant linages. Particularly high silica abundances are observed in lycophytes and early-diverging ferns. However, silica biomineralization is rare within later-evolving gymnosperms, implying a complex evolutionary history within the seed plants. Electron microscopy and X-ray spectroscopy show that the most common silica-mineralized tissues include the vascular system, epidermal cells, and stomata, which is consistent with the hypothesis that biomineralization in plants is frequently coupled to transpiration. Furthermore, sequence, phylogenetic, and structural analysis of nodulin 26-like intrinsic proteins from diverse plant genomes points to a plastic and ancient capacity for silica accumulation within terrestrial plants. The integration of these two comparative biology approaches demonstrates that silica biomineralization has been an important process for land plants over the course of their >400 My evolutionary history.

  6. Intermolecular interactions in the bilirubin-cholate-silica system

    NASA Astrophysics Data System (ADS)

    Vlasova, N. N.; Golovkova, L. P.; Severinovskaya, O. V.

    2007-06-01

    Bilirubin-cholate interactions in aqueous solutions were studied. The constants of binding of bilirubin with taurocholate dimers and taurodeoxycholate trimers were calculated. The adsorption of bilirubin and cholates on the surface of highly dispersed silica was studied. It was shown that taurine-conjugated cholates are poorly adsorbed from micellar solutions on the silica surface, the specific amount of bilirubin adsorbed decreases with increasing concentration of cholates in the solution, the affinity of free bilirubin for the silica surface is independent of the nature of the cholic acid, and that the affinity of cholate-bilirubin complexes for the silica surface is lower than the affinity of free bilirubin.

  7. Osteoinductive silk-silica composite biomaterials for bone regeneration

    PubMed Central

    Mieszawska, Aneta J.; Fourligas, Nikolaos; Georgakoudi, Irene; Ouhib, Nadia; Belton, David J.; Perry, Carole C.; Kaplan, David L.

    2010-01-01

    Osteoinductive and biodegradable composite biomaterials for bone regeneration were prepared by combining silk fibroin with silica particles. The influence of these composite systems on osteogenesis was evaluated with human mesenchymal stem cells (hMSCs) subjected to osteogenic differentiation. hMSCs adhered, proliferated, and differentiated towards osteogenic lineages on silk/silica films. The addition of the silica to the silk films influenced gene expression leading to upregulation of bone sialoprotein (BSP) and collagen type 1 (Col 1) osteogenic markers. Evidence for early bone formation in the form of collagen fibers and apatite nodules was obtained on the silk/silica films. Collagen fibers were closely associated with apatite deposits and overall collagen content was higher for the silica containing samples. Also, smaller sized silica particles (24 nm – 2 μm) with large surface area facilitated silica biodegradation in vitro through particle dissolution, leading to ~5 fold decrease in silica content over 10 weeks. These results indicate suitability of silk/silica composite system towards bone regeneration, where degradation/remodeling rates of the organic and inorganic components can be controlled. PMID:20817293

  8. Occupational exposure to crystalline silica and autoimmune disease.

    PubMed Central

    Parks, C G; Conrad, K; Cooper, G S

    1999-01-01

    Occupational exposure to silica dust has been examined as a possible risk factor with respect to several systemic autoimmune diseases, including scleroderma, rheumatoid arthritis, systemic lupus erythematosus, and some of the small vessel vasculitidies with renal involvement (e.g., Wegener granulomatosis). Crystalline silica, or quartz, is an abundant mineral found in sand, rock, and soil. High-level exposure to respirable silica dust can cause chronic inflammation and fibrosis in the lung and other organs. Studies of specific occupational groups with high-level silica exposure (e.g., miners) have shown increased rates of autoimmune diseases compared to the expected rates in the general population. However, some clinic- and population-based studies have not demonstrated an association between silica exposure and risk of autoimmune diseases. This lack of effect may be due to the limited statistical power of these studies to examine this association or because the lower- or moderate-level exposures that may be more common in the general population were not considered. Experimental studies demonstrate that silica can act as an adjuvant to nonspecifically enhance the immune response. This is one mechanism by which silica might be involved in the development of autoimmune diseases. Given that several different autoimmune diseases may be associated with silica dust exposure, silica dust may act to promote or accelerate disease development, requiring some other factor to break immune tolerance or initiate autoimmunity. The specific manifestation of this effect may depend on underlying differences in genetic susceptibility or other environmental exposures. PMID:10970168

  9. Tailoring silver nanoparticle construction using dendrimer templated silica networks

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojun; Kakkar, Ashok

    2008-06-01

    We have examined the role of the internal environment of dendrimer templated silica networks in tailoring the construction of silver nanoparticle assemblies. Silica networks from which 3,5-dihydroxybenzyl alcohol based dendrimer templates have been completely removed, slowly wet with an aqueous solution of silver acetate. The latter then reacts with internal silica silanol groups, leading to chemisorption of silver ions, followed by the growth of silver oxide nanoparticles. Silica network constructed using generation 4 dendrimer contains residual dendrimer template, and mixes with aqueous silver acetate solution easily. Upon chemisorption, silver ions get photolytically reduced to silver metal under a stabilizing dendrimer environment, leading to the formation of silver metal nanoparticles.

  10. Coated Fused Silica Fibers for Enhanced Sensitivity Torsion Pendulum

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Horowitz, Jordan; Camp, Jordan

    2007-01-01

    In order to investigate the fundamental thermal noise limit of a torsion pendulum using a fused silica fiber, we systematically measured and modeled the mechanical losses of thin fused silica fibers coated by electrically conductive thin metal films. Our results indicate that it is possible to achieve a thermal noise limit for coated silica lower by a factor between 3 and 9, depending on the silica diameter, compared to the best tungsten fibers available. This will allow a corresponding increase in sensitivity of torsion pendula used for weak force measurements, including the gravitational constant measurement and ground-based force noise testing for the Laser Interferometer Space Antenna (LISA) mission.

  11. Silica scintillating materials prepared by sol-gel methods

    SciTech Connect

    Werst, D.W.; Sauer, M.C. Jr.; Cromack, K.R.; Lin, Y.; Tartakovsky, E.A.; Trifunac, A.D.

    1993-12-31

    Silica was investigated as a rad-hard alternative to organic polymer hosts for organic scintillators. Silica sol-gels were prepared by hydrolysis of tetramethoxysilane in alcohol solutions. organic dyes were incorporated into the gels by dissolving in methanol at the sol stage of gel formation. The silica sol-gel matrix is very rad-hard. The radiation stability of silica scintillators prepared by this method is dye-limited. Transient radioluminescence was measured following excitation with 30 ps pulses of 20 MeV electrons.

  12. Biomimetic growth of silica tubes in confined media.

    PubMed

    Gautier, Clémentine; Lopez, Pascal J; Hemadi, Miryana; Livage, Jacques; Coradin, Thibaud

    2006-10-24

    Polymer membranes were used as biomimetic environments to study the effect of confinement on silica formation. Within membrane pores, silica tubes were formed, consisting of a dense silica shell incorporating nanoparticle aggregates. The shell structure does not depend on the membrane pore size, suggesting that its formation proceeds via interfacial interactions with the pore surface. In contrast, the size of primary nanoparticles within core aggregates is influenced by pore dimensions, indicating an effect of confinement on the diffusion-limited growth of silica. A parallel can be drawn with reported roles of confinement in biomineralization processes, providing a basis for future developments in biosilicification mimetic approaches and biofunctional nanomaterials design.

  13. Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels

    PubMed Central

    Matsui, Daisuke; Mayumi, Koichi

    2015-01-01

    Summary A significantly soft and tough nanocomposite gel was realized by a novel network formed using cyclodextrin-based polyrotaxanes. Covalent bond formation between the cyclic components of polyrotaxanes and the surface of silica nanoparticles (15 nm diameter) resulted in an infinite network structure without direct bonds between the main chain polymer and the silica. Small-angle X-ray scattering revealed that the homogeneous distribution of silica nanoparticles in solution was maintained in the gel state. Such homogeneous nanocomposite gels were obtained with at least 30 wt % silica content, and the Young’s modulus increased with silica content. Gelation did not occur without silica. This suggests that the silica nanoparticles behave as cross-linkers. Viscoelastic measurements of the nanocomposite gels showed no stress relaxation regardless of the silica content for <20% compression strain, indicating an infinite stable network without physical cross-links that have finite lifetime. On the other hand, the infinite network exhibited an abnormally low Young’s modulus, ~1 kPa, which is not explainable by traditional rubber theory. In addition, the composite gels were tough enough to completely maintain the network structure under 80% compression strain. These toughness and softness properties are attributable to both the characteristic sliding of polymer chains through the immobilized cyclodextrins on the silica nanoparticle and the entropic contribution of the cyclic components to the elasticity of the gels. PMID:26664642

  14. Measurement and modelization of silica opal optical properties

    NASA Astrophysics Data System (ADS)

    Avoine, Amaury; Hong, Phan Ngoc; Frederich, Hugo; Aregahegn, Kifle; Bénalloul, Paul; Coolen, Laurent; Schwob, Catherine; Thu Nga, Pham; Gallas, Bruno; Maître, Agnès

    2014-03-01

    We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflection spectra and we validate it by comparison with two independent infrared methods for the index and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements for the spheres diameter.

  15. Four hundred million years of silica biomineralization in land plants

    PubMed Central

    Trembath-Reichert, Elizabeth; Wilson, Jonathan Paul; McGlynn, Shawn E.; Fischer, Woodward W.

    2015-01-01

    Biomineralization plays a fundamental role in the global silicon cycle. Grasses are known to mobilize significant quantities of Si in the form of silica biominerals and dominate the terrestrial realm today, but they have relatively recent origins and only rose to taxonomic and ecological prominence within the Cenozoic Era. This raises questions regarding when and how the biological silica cycle evolved. To address these questions, we examined silica abundances of extant members of early-diverging land plant clades, which show that silica biomineralization is widespread across terrestrial plant linages. Particularly high silica abundances are observed in lycophytes and early-diverging ferns. However, silica biomineralization is rare within later-evolving gymnosperms, implying a complex evolutionary history within the seed plants. Electron microscopy and X-ray spectroscopy show that the most common silica-mineralized tissues include the vascular system, epidermal cells, and stomata, which is consistent with the hypothesis that biomineralization in plants is frequently coupled to transpiration. Furthermore, sequence, phylogenetic, and structural analysis of nodulin 26-like intrinsic proteins from diverse plant genomes points to a plastic and ancient capacity for silica accumulation within terrestrial plants. The integration of these two comparative biology approaches demonstrates that silica biomineralization has been an important process for land plants over the course of their >400 My evolutionary history. PMID:25825729

  16. A re-evaluation of /sup 32/S(n,p) cross sections from threshold to 5 MeV

    SciTech Connect

    Fu, C.Y.

    1989-01-01

    Two evaluations of the /sup 32/S(n,p) reaction cross sections, currently being used for the Nagasaki and Hiroshima dosimetry studies, yielded results that differ significantly. These two evaluations were reviewed and both were found to be quite old and without benefit of modern theoretical guidance and recent experimental data, hence inadequate in view of its relative importance for the present application. The necessity for a re-evaluation is further enhanced by the fact that: the present data search has uncovered a relatively high-quality data set that was not known previously, a generalized Bayes-theorem code is now available for averaging the various data sets with uncertainties and generating uncertainties for the results, effects on data combination of differing energy resolution in the various measurements can now be accounted for, and the ENDF/B-VI standards for /sup 238/U(n,f) cross sections have become available for renormalizing two of the available data sets. The re-evaluation is performed to 5 MeV, the upper energy limit for the present purpose. 8 refs., 2 figs.

  17. Re-Evaluation of the 1921 Peak Discharge at Skagit River near Concrete, Washington

    USGS Publications Warehouse

    Mastin, M.C.

    2007-01-01

    The peak discharge record at the U.S. Geological Survey (USGS) gaging station at Skagit River near Concrete, Washington, is a key record that has come under intense scrutiny by the scientific and lay person communities in the last 4 years. A peak discharge of 240,000 cubic feet per second for the flood on December 13, 1921, was determined in 1923 by USGS hydrologist James Stewart by means of a slope-area measurement. USGS then determined the peak discharges of three other large floods on the Skagit River (1897, 1909, and 1917) by extending the stage-discharge rating through the 1921 flood measurement. The 1921 estimate of peak discharge was recalculated by Flynn and Benson of the USGS after a channel roughness verification was completed based on the 1949 flood on the Skagit River. The 1949 recalculation indicated that the peak discharge probably was 6.2 percent lower than Stewart's original estimate but the USGS did not officially change the peak discharge from Stewart's estimate because it was not more than a 10-percent change (which is the USGS guideline for revising peak flows) and the estimate already had error bands of 15 percent. All these flood peaks are now being used by the U.S. Army Corps of Engineers to determine the 100-year flood discharge for the Skagit River Flood Study so any method to confirm or improve the 1921 peak discharge estimate is warranted. During the last 4 years, two floods have occurred on the Skagit River (2003, 2006) that has enabled the USGS to collect additional data, do further analysis, and yet again re-evaluate the 1921 peak discharge estimate. Since 1949, an island/bar in the study reach has reforested itself. This has complicated the flow hydraulics and made the most recent recalculation of the 1921 flood based on channel roughness verification that used 2003 and 2006 flood data less reliable. However, this recent recalculation did indicate that the original peak-discharge calculation by Stewart may be high, and it added to a

  18. Is the Gop rift oceanic? A reevaluation of the Seychelles-India conjugate margins

    NASA Astrophysics Data System (ADS)

    Guan, Huixin; Werner, Philippe; Geoffroy, Laurent

    2016-04-01

    Recent studies reevaluated the timing and evolution of the breakup process between the Seychelles continental ridge and India, and the relationship between this evolution and mantle melting associated with the Deccan Igneous Province1,2,3. Those studies, mainly based on gravity and seismic refraction surveys, point that the oceanic domain located between the Seychelles and the Laxmi Ridge (here designed as the Carlsberg Basin) is the youngest oceanic domain between India and the Seychelles. To the East of the Laxmi Ridge, the aborted Gop Rift is considered as an older highly magmatic extensional continental system with magmatism, breakup and oceanic spreading being coeval with or even predating the emplacement of the major pulse of the Deccan trapps. This interpretation on the oceanic nature of the Gop Rift conflicts with other extensive surveys based on magnetic and seismic reflection data4 which suggest that the Gop Rift is an extended syn-magmatic continental domain. In our work based (a) on the existing data, (b) on new deep-seismic reflection surveys (already published by Misra5) down to the Moho and underlying mantle and (c) on new concepts on the geometry of volcanic passive margins, we propose a distinct interpretation of the Seychelles-India system. As proposed by former authors6,7, the Indian margin suffered some continental stretching and thinning before the onset of the Deccan traps during the Mesozoic. Thus continental crust thickness cannot be used easily as a proxy of syn-magmatic stretching-thinning processes or even to infer the presence or not of oceanic-type crust based, solely, on crustal thickness. However, some remarkable features appear on some of the deep penetration seismic lines we studied. We illustrate that the whole Seychelles/India system, before the opening of the present-day "Carlsberg Basin" may simply be regarded as a pair of sub-symmetric conjugate volcanic passive margins (VPMs) with inner and outer SDR wedges dipping towards the

  19. Influence of amorphous silica on the hydration in ultra-high performance concrete

    SciTech Connect

    Oertel, Tina; Helbig, Uta; Hutter, Frank; Kletti, Holger; Sextl, Gerhard

    2014-04-01

    Amorphous silica particles (silica) are used in ultra-high performance concretes to densify the microstructure and accelerate the clinker hydration. It is still unclear whether silica predominantly increases the surface for the nucleation of C–S–H phases or dissolves and reacts pozzolanically. Furthermore, varying types of silica may have different and time dependent effects on the clinker hydration. The effects of different silica types were compared in this study by calorimetric analysis, scanning and transmission electron microscopy, in situ X-ray diffraction and compressive strength measurements. The silica component was silica fume, pyrogenic silica or silica synthesized by a wet-chemical route (Stoeber particles). Water-to-cement ratios were 0.23. Differences are observed between the silica for short reaction times (up to 3 days). Results indicate that silica fume and pyrogenic silica accelerate alite hydration by increasing the surface for nucleation of C–S–H phases whereas Stoeber particles show no accelerating effect.

  20. Silica uptake from nanoparticles and silica condensation state in different tissues of Phragmites australis.

    PubMed

    Schaller, Jörg; Brackhage, Carsten; Paasch, Silvia; Brunner, Eike; Bäucker, Ernst; Dudel, E Gert

    2013-01-01

    Silicon is described as beneficial for grasses by enhancing yield and fitness via a considerable contribution to pathogen, drought, and pest resistance. Silicic acid is the predominant form for uptake and transport within the plant and will precipitate in leaves. But it is unknown whether polymeric nanosilicon compounds in its synthetic form, with an increasing concentration in aquatic environments, can be suitable for plant nutrition. Therefore, we investigated the uptake, transport, and deposition of silicic acid/silica within plants using synthetic nanosilica. Our results show a significant difference in silicon (Si) content within the different tissues of Phragmites australis. The nanosilica had been dissolved prior to the uptake by plants. The chemical form of Si during uptake was not traceable. A significant enhancement in the condensation state of the silica was found from root to leaves especially from culm to leaf tips visible by the increasing content of Q(4)-groups in the NMR spectra. We conclude that synthetic nanosilica has the same quality as source for the beneficial element Si like natural silica. Since the condensation state is described to control silica solubility, we suggest that different condensation states within the plant may result in different remobilization of silicon during decomposition of the plant material. PMID:23178503

  1. Silica-replaced oolites, bedded shelf cherts and Paleozoic changes in the silica cycle

    NASA Astrophysics Data System (ADS)

    Kidder, David L.; Mumma, Stephanie A.

    2003-12-01

    Oolites that were replaced by early diagenetic silica and were not reworked from their original depositional setting can serve as a useful tool to evaluate a previously suggested retreat of biosiliceous facies from peritidal environments to deeper water settings in the Early Paleozoic. The silica-replaced oolites suggest that the retreat was largely over by the Middle Ordovician, which is consistent with emerging compilations of the spatial and temporal distribution Ordovician cherts. Whether the retreat was a function of declining concentration of dissolved silica in shallow marine waters or of radiation of faunas from nearshore into offshore settings or some combination of both is an issue that may be clarified with improved resolution of the timing of the retreat. A small Upper Carboniferous peak in silica-replaced oolite abundance coincides with a minor rebound in shelf chert accumulation and the common presence of coastal flint deposits in Upper Carboniferous cyclothems, suggesting that cherty facies returned to shallow water environments at this time.

  2. Synthesis of microforsterite using derived-amorphous-silica of silica sands

    NASA Astrophysics Data System (ADS)

    Nurbaiti, Upik; Triwikantoro, Zainuri, Mochamad; Pratapa, Suminar

    2016-04-01

    Synthesis of microforsterite (Mg2SiO4) has been successfully done by a simple method benefiting of the local silica sands from Tanah Laut, Indonesia. The starting material was amorphous silica powder which was processed using coprecipitation method from the sands. The silica powder was obtained from a series of stages of the purification process of the sands, namely magnetic separation, grinding and soaking with HCl. The microforsterite synthesis followed the reaction of stoichiometric mole ratio mixing of 1:2 of the amorphous silica and MgO powders with 3 wt% addion of PVA as a catalyst.The mixture was calcined at temperatures between 1150-1400°C with 4 hours holding time. XRD data showed that calcination at a temperature of 1150°C for 4 hours was optimum where the weight fraction of forsterite can reach as much as 93 wt% with MgO as the secondary phase and without MgSiO3. SEM photograph of the microforsterite showed tapered morphology with a relatively homogeneous distribution.

  3. Amorphous silica-like carbon dioxide.

    PubMed

    Santoro, Mario; Gorelli, Federico A; Bini, Roberto; Ruocco, Giancarlo; Scandolo, Sandro; Crichton, Wilson A

    2006-06-15

    Among the group IV elements, only carbon forms stable double bonds with oxygen at ambient conditions. At variance with silica and germania, the non-molecular single-bonded crystalline form of carbon dioxide, phase V, only exists at high pressure. The amorphous forms of silica (a-SiO2) and germania (a-GeO2) are well known at ambient conditions; however, the amorphous, non-molecular form of CO2 has so far been described only as a result of first-principles simulations. Here we report the synthesis of an amorphous, silica-like form of carbon dioxide, a-CO2, which we call 'a-carbonia'. The compression of the molecular phase III of CO2 between 40 and 48 GPa at room temperature initiated the transformation to the non-molecular amorphous phase. Infrared spectra measured at temperatures up to 680 K show the progressive formation of C-O single bonds and the simultaneous disappearance of all molecular signatures. Furthermore, state-of-the-art Raman and synchrotron X-ray diffraction measurements on temperature-quenched samples confirm the amorphous character of the material. Comparison with vibrational and diffraction data for a-SiO2 and a-GeO2, as well as with the structure factor calculated for the a-CO2 sample obtained by first-principles molecular dynamics, shows that a-CO2 is structurally homologous to the other group IV dioxide glasses. We therefore conclude that the class of archetypal network-forming disordered systems, including a-SiO2, a-GeO2 and water, must be extended to include a-CO2. PMID:16778885

  4. Protein-templated biomimetic silica nanoparticles.

    PubMed

    Jackson, Erienne; Ferrari, Mariana; Cuestas-Ayllon, Carlos; Fernández-Pacheco, Rodrigo; Perez-Carvajal, Javier; de la Fuente, Jesús M; Grazú, Valeria; Betancor, Lorena

    2015-03-31

    Biomimetic silica particles can be synthesized as a nanosized material within minutes in a process mimicked from living organisms such as diatoms and sponges. In this work, we have studied the effect of bovine serum albumin (BSA) as a template to direct the synthesis of silica nanoparticles (NPs) with the potential to associate proteins on its surface. Our approach enables the formation of spheres with different physicochemical properties. Particles using BSA as a protein template were smaller (∼250-380 nm) and were more monodisperse than those lacking the proteic core (∼700-1000 nm) as seen by dynamic light scattering (DLS), scanning electron microscopy (SEM), and environmental scanning electron microscopy (ESEM) analysis. The absence of BSA during synthesis produced silica nanoparticles without any porosity that was detectable by nitrogen adsorption, whereas particles containing BSA developed porosity in the range of 4 to 5 nm which collapsed on the removal of BSA, thus producing smaller pores. These results were in accordance with the pore size calculated by high-resolution transmission electron microscopy (HTEM). The reproducibility of the BSA-templated nanoparticle properties was determined by analyzing four batches of independent synthesizing experiments that maintained their properties. The high positive superficial charge of the nanoparticles facilitated adsorption under mild conditions of a range of proteins from an E. coli extract and a commercial preparation of laccase from Trametes versicolor. All of the proteins were quantitatively desorbed. Experiments conducted showed the reusability of the particles as supports for the ionic adsorption of the biomolecules. The protein loading capacity of the BSA-based biomimetic particles was determined using laccase as 98.7 ± 6.6 mg·g(-1) of particles.

  5. Silica nanoparticle phytotoxicity to Arabidopsis thaliana.

    PubMed

    Slomberg, Danielle L; Schoenfisch, Mark H

    2012-09-18

    The phytotoxicity of silica nanoparticles (SiNPs) was evaluated as a function of particle size (14, 50, and 200 nm), concentration (250 and 1000 mg L(-1)), and surface composition toward Arabidopsis thaliana plants grown hydroponically for 3 and 6 weeks. Reduced development and chlorosis were observed for plants exposed to highly negative SiNPs (-20.3 and -31.9 mV for the 50 and 200 nm SiNPs, respectively) regardless of particle concentration when not controlling pH of the hydroponic medium, which resulted in increased alkalinity (~pH 8). Particles were no longer toxic to the plants at either concentration upon calcination or removal of surface silanols from the SiNP surface, or adjusting the pH of the growth medium to pH 5.8. The phytotoxic effects observed for the negatively charged 50 and 200 nm SiNPs were attributed to pH effects and the adsorption of macro- and micro-nutrients to the silica surface. Size-dependent uptake of the nanoparticles by the plants was confirmed using transmission electron microscopy (TEM) and inductively coupled plasma-optical emission spectroscopy (ICP-OES) with plant roots containing 32.0, 1.85, and 7.00 × 10(-3) mg Si·kg tissue(-1)/nm(3) (normalized for SiNP volume) for the 14, 50, and 200 nm SiNPs respectively, after 6 weeks exposure at 1000 ppm (pH 5.8). This study demonstrates that the silica scaffolds are not phytotoxic up to 1000 ppm despite significant uptake of the SiNPs (14, 50, and 200 nm) into the root system of A. thaliana. PMID:22889047

  6. Quartz/fused silica chip carriers

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The primary objective of this research and development effort was to develop monolithic microwave integrated circuit (MMIC) packaging which will operate efficiently at millimeter-wave frequencies. The packages incorporated fused silica as the substrate material which was selected due to its favorable electrical properties and potential performance improvement over more conventional materials for Ka-band operation. The first step towards meeting this objective is to develop a package that meets standard mechanical and thermal requirements using fused silica and to be compatible with semiconductor devices operating up to at least 44 GHz. The second step is to modify the package design and add multilayer and multicavity capacity to allow for application specific integrated circuits (ASIC's) to control multiple phase shifters. The final step is to adapt the package design to a phased array module with integral radiating elements. The first task was a continuation of the SBIR Phase 1 work. Phase 1 identified fused silica as a viable substrate material by demonstrating various plating, machining, and adhesion properties. In Phase 2 Task 1, a package was designed and fabricated to validate these findings. Task 2 was to take the next step in packaging and fabricate a multilayer, multichip module (MCM). This package is the predecessor to the phased array module and demonstrates the ability to via fill, circuit print, laminate, and to form vertical interconnects. The final task was to build a phased array module. The radiating elements were to be incorporated into the package instead of connecting to it with wire or ribbon bonds.

  7. Biologically Inspired Flagella-Templated Silica Nanotubes

    NASA Astrophysics Data System (ADS)

    Jo, Wonjin

    The desire and need for various types of nanostructures have been met with challenges of feasibility, reproducibility, and long fabrication time. To work towards improved bottom-up methods of nanofabrication, bacterial flagella are particularly attractive bio-templates for nanotubes due to their tubular structures and small inner and outer diameters. In this work, flagella isolated from Salmonella typhimurium are used as bio-templates to fabricate silica mineralized nanotubes. The process involves as well-controlled hydrolysis and condensation reaction with aminopropyltriethoxysilane (APTES), followed by the addition of tetraethoxysilane (TEOS). By controlling the concentration of TEOS and the reaction time, a simple and precise method is developed for creating silica-mineralized flagella nanotubes (SMFNs) with various thicknesses of the silica layer. In addition, the SMFNs are further modified to multifunctional nanotubes by coating metal nanoparticles (NPs) or metal oxide NPs such as gold, palladium, and iron oxide. The metallized SMFNs are achieved through reactions including reductive metallization or oxidative hydrolysis. The results from these studies provide evidence for the complete coating of SMFNs with uniform metal NP sizes and high surface area coverage. The metallized SMFNs are found to be electrically conductive along their network structures. The current-voltage characteristics show remarkably improved electrical conductivities depending on the types of metal NPs loading and SMFN networks concentration. The biologically inspired SMFNs with metal loading will allow have controlled electrical properties that can lead to the potential of creating unique and precise nanoelectronic materials. Lastly, the randomly entangled SMFNs are characterized to demonstrate their capabilities for hydrophilic and hydrophobic surface applications.

  8. Absorption of isoflurane by silica gel.

    PubMed

    Lumb, A B; Landon, M J

    1991-07-01

    We have studied the capacity of the drying agent silica gel (SG) to absorb isoflurane from gas samples. When dry, SG was able to absorb 31 times its own volume of isoflurane vapour, which could be recovered almost completely from the SG by displacement with water vapour. However, we were unable to demonstrate any significant absorption of isoflurane by wet SG. Care must be taken, therefore, when using SG as a drying agent in the sampling line of an analyser during research involving volatile anaesthetic agents. PMID:1650238

  9. Optomechanics and thermometry of cryogenic silica microresonators

    NASA Astrophysics Data System (ADS)

    MacDonald, A. J. R.; Hauer, B. D.; Rojas, X.; Kim, P. H.; Popowich, G. G.; Davis, J. P.

    2016-01-01

    We present measurements of silica optomechanical resonators, known as bottle resonators, passively cooled in a cryogenic environment. These devices possess a suite of properties that make them advantageous for preparation and measurement in the mechanical ground state, including high mechanical frequency, high optical and mechanical quality factors, and optomechanical sideband resolution. Performing thermometry of the mechanical motion, we find that the optical and mechanical modes demonstrate quantitatively similar laser-induced heating, limiting the lowest average phonon occupation observed to just ˜1500 . Thermalization to the 9 mK thermal bath would facilitate quantum measurements on these promising nanogram-scale mechanical resonators.

  10. Composite Silica Aerogels Opacified with Titania

    NASA Technical Reports Server (NTRS)

    Paik, Jon-Ah; Sakamoto, Jeffrey; Jones, Steven; Fleurial, Jean-Pierre; DiStefano, Salvador; Nesmith, Bill

    2009-01-01

    A further improvement has been made to reduce the high-temperature thermal conductivities of the aerogel-matrix composite materials described in Improved Silica Aerogel Composite Materials (NPO-44287), NASA Tech Briefs, Vol. 32, No. 9 (September 2008), page 50. Because the contribution of infrared radiation to heat transfer increases sharply with temperature, the effective high-temperature thermal conductivity of a thermal-insulation material can be reduced by opacifying the material to reduce the radiative contribution. Therefore, the essence of the present improvement is to add an opacifying constituent material (specifically, TiO2 powder) to the aerogel-matrix composites.

  11. Inert strength of pristine silica glass fibers

    SciTech Connect

    Smith, W.L.; Michalske, T.A.

    1993-11-01

    Silica glass fibers have been produced and tested under ultra high vacuum (UHV) conditions to investigate the inert strength of pristine fibers in absence of reactive agents. Analysis of the coefficient of variation in diameter ({upsilon}{sub d}) vs the coefficient of variation of breaking strength ({upsilon}{sub {sigma}}) does not adequately explain the variation of breaking stress. Distribution of fiber tensile strength data suggests that the inert strength of such fibers is not single valued and that the intrinsic strength is controlled by defects in the glass. Furthermore, comparison of room temperature UHV data with LN{sub 2} data indicates that these intrinsic strengths are not temperature dependent.

  12. Prediction of rigid silica based insulation conductivity

    NASA Technical Reports Server (NTRS)

    Williams, Stanley D.; Curry, Donald M.

    1993-01-01

    A method is presented for predicting the thermal conductivity of low density, silica based fibrous insulators. It is shown that the method can be used to extend data values to the upper material temperature limits from those obtained from the test data. It is demonstrated that once the conductivity is accurately determined by the analytical model the conductivity for other atmospheres can be predicted. The method is similar to that presented by previous investigators, but differs significantly in the contribution due to gas and internal radiation.

  13. Fluorescence properties of dye doped mesoporous silica

    SciTech Connect

    Carbonaro, Carlo M. Corpino, Riccardo Ricci, Pier Carlo Chiriu, Daniele; Cannas, Carla

    2014-10-21

    In this paper we present a review of the main results we obtained studying the emission properties of organic-inorganic hybrids obtained combining mesoporous silica and Xantene dyes, in particular the standard reference Rhodamine 6G. The purpose of the review is to show the possibility to efficiently 'dope' the transparent inorganic porous matrix to obtain promising systems for photonic and biomedical applications. The strategies to solve the concentration effect and the leaching phenomenon are discussed within the framework of the single exciton theory.

  14. Adsorption in sparse networks. 2: Silica aerogels

    SciTech Connect

    Scherer, G.W.; Calas, S.; Sempere, R.

    1998-06-15

    The model developed in Part 1 is applied to nitrogen adsorption isotherms obtained for a series of silica aerogels whose densities are varied by partial sintering. The isotherms are adequately described by a cubic network model, with all of the pores falling in the mesopore range; the adsorption and desorption branches are fit by the same pore size distribution. For the least dense gels, a substantial portion of the pore volume is not detected by condensation. The model attributes this effect to the shape of the adsorbate/adsorptive interface, which can adopt zero curvature even in mesopores, because of the shape of the network.

  15. Fibrous composites comprising carbon nanotubes and silica

    DOEpatents

    Peng, Huisheng; Zhu, Yuntian Theodore; Peterson, Dean E.; Jia, Quanxi

    2011-10-11

    Fibrous composite comprising a plurality of carbon nanotubes; and a silica-containing moiety having one of the structures: (SiO).sub.3Si--(CH.sub.2).sub.n--NR.sub.1R.sub.2) or (SiO).sub.3Si--(CH.sub.2).sub.n--NCO; where n is from 1 to 6, and R.sub.1 and R.sub.2 are each independently H, CH.sub.3, or C.sub.2H.sub.5.

  16. Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

    SciTech Connect

    Alyoshina, Nonna A.; Parfenyuk, Elena V.

    2013-09-15

    A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N{sub 2} adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica.

  17. New insight into silica deposition in horsetail (Equisetum arvense)

    PubMed Central

    2011-01-01

    Background The horsetails (Equisetum sp) are known biosilicifiers though the mechanism underlying silica deposition in these plants remains largely unknown. Tissue extracts from horsetails grown hydroponically and also collected from the wild were acid-digested in a microwave oven and their silica 'skeletons' visualised using the fluor, PDMPO, and fluorescence microscopy. Results Silica deposits were observed in all plant regions from the rhizome through to the stem, leaf and spores. Numerous structures were silicified including cell walls, cell plates, plasmodesmata, and guard cells and stomata at varying stages of differentiation. All of the major sites of silica deposition in horsetail mimicked sites and structures where the hemicellulose, callose is known to be found and these serendipitous observations of the coincidence of silica and callose raised the possibility that callose might be templating silica deposition in horsetail. Hydroponic culture of horsetail in the absence of silicic acid resulted in normal healthy plants which, following acid digestion, showed no deposition of silica anywhere in their tissues. To test the hypothesis that callose might be templating silica deposition in horsetail commercially available callose was mixed with undersaturated and saturated solutions of silicic acid and the formation of silica was demonstrated by fluorimetry and fluorescence microscopy. Conclusions The initiation of silica formation by callose is the first example whereby any biomolecule has been shown to induce, as compared to catalyse, the formation of silica in an undersaturated solution of silicic acid. This novel discovery allowed us to speculate that callose and its associated biochemical machinery could be a missing link in our understanding of biosilicification. PMID:21801378

  18. Relationship between amorphous silica and precious metal in quartz veins

    NASA Astrophysics Data System (ADS)

    Harrichhausen, N.; Rowe, C. D.; Board, W. S.; Greig, C. J.

    2015-12-01

    Super-saturation of silica is common in fault fluids, due to pressure changes associated with fracture, fault slip, or temperature gradients in hydrothermal systems. These mechanisms lead to precipitation of amorphous silica, which will recrystallize to quartz under typical geologic conditions. These conditions may also promote the saturation of precious metals, such as gold, and the precipitation of nanoparticles. Previous experiments show that charged nanoparticles of gold can attach to the surface of amorphous silica nanoparticles. Thus, gold and silica may be transported as a colloid influencing mineralization textures during amorphous silica recrystallization to quartz. This may enrich quartz vein hosted gold deposits, but the instability of hydrous silica during subsequent deformation means that the microstructural record of precipitation of gold is lost. We investigate a recent, shallow auriferous hydrothermal system at Dixie Valley, Nevada to reveal the nano- to micro-scale relationships between gold and silica in fresh veins. Fault slip surfaces at Dixie Valley exhibit layers of amorphous silica with partial recrystallization to quartz. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) show amorphous silica can contain a few wt. % gold while areas recrystallized to quartz are barren. At the Jurassic Brucejack deposit in British Columbia, Canada we observe the cryptocrystalline quartz textures that may indicate recrystallization from amorphous silica within quartz-carbonate veins containing high grade gold. Comb quartz within syntaxial veins, vugs, and coating breccia clasts indicate structural dilation. Vein geometry is investigated to determine relative importance of fault slip in creating dilational sites. By comparing quartz-carbonate veins from the Dixie Valley to Brucejack, we can determine whether amorphous silica formed in different environments show similar potential to affect precious metal mineralization.

  19. Multifunctional antireflection coatings based on novel hollow silica-silica nanocomposites.

    PubMed

    Zhang, Xianpeng; Lan, Pinjun; Lu, Yuehui; Li, Jia; Xu, Hua; Zhang, Jing; Lee, YoungPak; Rhee, Joo Yull; Choy, Kwang-Leong; Song, Weijie

    2014-02-12

    Antireflection (AR) coatings that exhibit multifunctional characteristics, including high transparency, robust resistance to moisture, high hardness, and antifogging properties, were developed based on hollow silica-silica nanocomposites. These novel nanocomposite coatings with a closed-pore structure, consisting of hollow silica nanospheres (HSNs) infiltrated with an acid-catalyzed silica sol (ACSS), were fabricated using a low-cost sol-gel dip-coating method. The refractive index of the nanocomposite coatings was tailored by controlling the amount of ACSS infiltrated into the HSNs during synthesis. Photovoltaic transmittance (TPV) values of 96.86-97.34% were obtained over a broad range of wavelengths, from 300 to 1200 nm; these values were close to the theoretical limit for a lossy single-layered AR coating (97.72%). The nanocomposite coatings displayed a stable TPV, with degradation values of less than 4% and 0.1% after highly accelerated temperature and humidity stress tests, and abrasion tests, respectively. In addition, the nanocomposite coatings had a hardness of approximately 1.6 GPa, while the porous silica coatings with an open-pore structure showed more severe degradation and had a lower hardness. The void fraction and surface roughness of the nanocomposite coatings could be controlled, which gave rise to near-superhydrophilic and antifogging characteristics. The promising results obtained in this study suggest that the nanocomposite coatings have the potential to be of benefit for the design, fabrication, and development of multifunctional AR coatings with both omnidirectional broadband transmission and long-term durability that are required for demanding outdoor applications in energy harvesting and optical instrumentation in extreme climates or humid conditions.

  20. Rubber products prepared from silica modified by radiation-induced admicellar polymerization

    NASA Astrophysics Data System (ADS)

    Pongprayoon, Thirawudh; Yooprasert, Narissara; Suwanmala, Phiriyatorn; Hemvichian, Kasinee

    2012-05-01

    Unmodified silica, silica modified with Si69, silica modified by thermal admicellar polymerization and silica modified by radiation-induced admicellar polymerization were applied as rubber reinforcement. Mechanical properties of these different rubber formulae were subsequently tested. The results revealed that the mechanical properties of rubber reinforced with silica modified by admicellar polymerization were superior to those reinforced with unmodified silica or silica modified with Si69. As for the silica modified by admicellar polymerization, cetyltrimethyl ammonium bromide (CTAB) proved to be the most effective surfactant, compared to dodecyltrimethyl ammonium bromide (DTAB) and tetradecyltrimethyl ammonium bromide (TTAB).

  1. Dopamine-induced silica-polydopamine hybrids with controllable morphology.

    PubMed

    Ho, Chia-Che; Ding, Shinn-Jyh

    2014-04-01

    Novel silica-polydopamine hybrids, with controllable morphology, are facilely fabricated in an emulsion system consisting of tetraethyl orthosilicate, dopamine, water, and NaOH under weakly basic conditions (pH 8.5-10). An increase in initial pH favors the formation of nano-structured spherical silica-PDA hybrids from a flocculated structure.

  2. Dynamics of a hydrogenated silica xerogel: A neutron scattering study

    SciTech Connect

    Fontana, A.; Orsingher, L.; Rossi, F.

    2006-11-01

    Neutron scattering measurements of a hydrogenated vitreous silica (or xerogel) sample reveal an unexpectedly high mean-square displacement of the silanol hydrogen atoms at 150 and 300 K. At 150 K, the spectrum mimics the boson peak of vitreous silica. The finding suggests a large local displacement of the boson peak modes at the breaking points of the continuous random network.

  3. Biodegradable hollow silica nanospheres containing gold nanoparticle arrays.

    PubMed

    Cassano, Domenico; Rota Martir, Diego; Signore, Giovanni; Piazza, Vincenzo; Voliani, Valerio

    2015-06-21

    We introduce biodegradable hollow silica nanocapsules embedding arrays of 3 nm gold nanoparticles. The silica shell degrades in full serum in a few hours, potentially allowing the clearance of the capsules and their contents by the efficient renal pathway, and thereby overcoming accumulation issues typical of metal nanoparticles.

  4. Community Geothermal Technology Program: Silica bronze project. Final report

    SciTech Connect

    Bianchini, H.

    1989-10-01

    Objective was to incorporate waste silica from the HGP-A geothermal well in Pohoiki with other refractory materials for investment casting of bronze sculpture. The best composition for casting is about 50% silica, 25% red cinders, and 25% brick dust; remaining ingredient is a binder, such as plaster and water.

  5. A solubility model for amorphous silica in concentrated electrolytes

    SciTech Connect

    Felmy, A.R.; Schroeder, C.C.; Mason, M.J.

    1994-08-01

    Silica is one of the major constituents of the earth`s crust and is ubiquitously present in most natural materials. The solubility of silica and other silica-containing compounds is, therefore, of primary concern in geochemistry and in chemical processing applications where silica scale formation, resulting from changes in temperature and electrolyte composition, can cause problems in process design and operation. This paper describes the development of an aqueous thermodynamic model for accurately predicting the solubility of amorphous silica and other silica-containing compounds in the system Na{sup +}-H{sup +}-Mg{sup 2+}-NO{sub 3}{sup {minus}}-SO{sub 4}{sup 2{minus}}-Cl{sup {minus}}-H{sub 2}O to high concentration and across the temperature range 25--100 C. This model, which utilizes the aqueous thermodynamic model of Pitzer, includes only one dissolved silica species, H{sub 4}SiO{sub 4}(aq), and is valid in neutral to very acidic solutions. The model is parameterized from the extensive set of solubility data in the literature as well as from new experimental data on amorphous silica solubility in HNO{sub 3} and HCl developed as part of this study. The accuracy of the model is tested on solutions more complex than those used in model parameterization.

  6. Maintenance of Bacterial Cultures on Anhydrous Silica Gel

    ERIC Educational Resources Information Center

    Lennox, John E.

    1977-01-01

    Suspensions of 20 different cultures were grown on appropriate media, then pipetted into sterile anhydrous silica gel. Silica gel cultures after incubation and refrigerated storage were tested for viability. Results showed little mutation, low replication, low contamination, minimal expenses, and survival up to two years. (CS)

  7. Laser based on dye-activated silica gel

    SciTech Connect

    Altshuler, G.B.; Bakhanov, V.A.; Dulneva, E.G.; Erofeev, A.V.; Mazurin, O.V.; Roskova, G.P.; Tsekhomskaya, T.S.

    1987-06-01

    Silica gel activated by a dye is used as a new laser medium. The lasin characteristics of rhodamine 6G in silica gel are reported. An important characteristic of the dye laser is its long service life, which is determined by the photostability of the dye in silic gel.(AIP)

  8. 78 FR 3449 - Silica Bricks and Shapes From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-16

    ... 23, 2012 (77 FR 70185). The conference was held in Washington, DC, on December 6, 2012, and all... COMMISSION Silica Bricks and Shapes From China Determination On the basis of the record \\1\\ developed in the... China of silica bricks and shapes, provided for in subheading 6902.20.10 of the Harmonized...

  9. Preparation and Characterization of Colloidal Silica Particles under Mild Conditions

    ERIC Educational Resources Information Center

    Neville, Frances; Zin, Azrinawati Mohd.; Jameson, Graeme J.; Wanless, Erica J.

    2012-01-01

    A microscale laboratory experiment for the preparation and characterization of silica particles at neutral pH and ambient temperature conditions is described. Students first employ experimental fabrication methods to make spherical submicrometer silica particles via the condensation of an alkoxysilane and polyethyleneimine, which act to catalyze…

  10. Electrophoretic deposition of composite hydroxyapatite-silica-chitosan coatings

    SciTech Connect

    Grandfield, K.; Zhitomirsky, I.

    2008-01-15

    Electrophoretic deposition (EPD) method has been developed for the fabrication of nanocomposite silica-chitosan coatings. Cathodic deposits were obtained on various conductive substrates using suspensions of silica nanoparticles in a mixed ethanol-water solvent, containing dissolved chitosan. Co-deposition of silica and hydroxyapatite (HA) nanoparticles resulted in the fabrication of HA-silica-chitosan coatings. The deposition yield has been studied at a constant voltage mode at various deposition durations. The method enabled the formation of coatings of different thickness in the range of up to 100 {mu}m. Deposit composition, microstructure and porosity can be varied by variation of HA and silica concentration in the suspensions. It was demonstrated that EPD can be used for the fabrication of HA-silica-chitosan coatings of graded composition and laminates. The method enabled the deposition of coatings containing layers of silica-chitosan and HA-chitosan nanocomposites using suspensions with different HA and silica content. Obtained coatings were studied by X-ray diffraction, thermogravimetric and differential thermal analysis, scanning electron microscopy and energy dispersive spectroscopy. The mechanism of deposition is discussed.

  11. A bioinspired strategy for surface modification of silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Tian, Jianwen; Zhang, Haoxuan; Liu, Meiying; Deng, Fengjie; Huang, Hongye; Wan, Qing; Li, Zhen; Wang, Ke; He, Xiaohui; Zhang, Xiaoyong; Wei, Yen

    2015-12-01

    Silica nanoparticles have become one of the most promising nanomaterials for a vast of applications. In this work, a novel strategy for surface modification of silica nanoparticles has been developed for the first time via combination of mussel inspired chemistry and Michael addition reaction. In this procedure, thin polydopamine (PDA) films were first coated on the bare silica nanoparticles via self-polymerization of dopamine in alkaline condition. And then amino-containing polymers were introduced onto the PDA coated silica nanoparticles through Michael addition reaction, that are synthesized from free radical polymerization using poly(ethylene glycol) methyl methacrylate (PEGMA) and N-(3-aminopropyl) methacrylamide (NAPAM) as monomers and ammonium persulfate as the initiator. The successful modification of silica nanoparticles was evidenced by a series of characterization techniques. As compared with the bare silica nanoparticles, the polymers modified silica nanoparticles showed remarkable enhanced dispersibility in both aqueous and organic solution. This strategy is rather simple, effective and versatile. Therefore, it should be of specific importance for further applications of silica nanoparticles and will spark great research attention of scientists from different fields.

  12. Abnormal behavior of silica doped with small amounts of aluminum

    PubMed Central

    Liu, Jinling; Wang, Yiguang; An, Linan

    2016-01-01

    Silica is the most abundant mineral in the crust of the Earth. It has been demonstrated that the aluminum concentration in silica plays a key role in determining many properties of silica-based components. Although the alumina-silica system has been intensely studied, the effect of very small amounts of aluminum on the structure and properties of silica remains unclear. We report results of first principles calculations showing that small amounts of aluminum could be metastable when located in the center of Si-O rings without breaking the silica network. In contrast, higher aluminum contents will result in the destruction of the Si-O bonds, leading to the formation of triclusters and a 4-, 5-, and 6-fold Al-O coordination, as observed in previous studies. Based on the silica structure obtained through geometric optimization, the properties of silica doped with small amounts of aluminum were calculated. The results can account for many ‘abnormal’ phenomena experimentally observed. The results benefit most areas such as geosciences, microelectronics, glass industry, and ceramic materials. PMID:27752133

  13. CO2 laser welding fused silica.

    SciTech Connect

    Reed, Scott T.; MacCallum, Danny O'Neill; Knorovsky, Gerald Albert

    2005-08-01

    The feasibility of laser welding of fused silica (aka quartz) has been demonstrated recently by others. An application requiring hermetic sealing of a thin, pressure-bearing quartz diaphragm to a thicker frame led us to explore this technique. We found that laser welding techniques normally used for metallic parts caused scorching and uneven melting. Contrary to standard practices (near focus, high travel speed, high power density), successful welds in fused silica required a broad heat source applied over a large area under a slow rotation to gradually heat the glass through the annealing, softening and finally working temperatures. Furthermore, good mechanical contact between the parts to be joined played an even more important role in this process than in typical metallic joints. A 50 W CO2 laser with 4 f.l. ZnSe2 lens and rotary head was used to weld 0.425 OD, 0.006-0.010 thick, disks to 0.500 OD tubing with 0.125 walls. Several joint geometries and beam orientations were investigated. Temperature profiles were measured and compared to an FEM thermal model. We will discuss the effects of laser power, travel speed, number of passes, joint geometry and part thicknesses on achieving hermeticity and cosmetically-acceptable joints.

  14. Mechanical and Thermal Characterization of Silica Nanocomposites

    NASA Astrophysics Data System (ADS)

    Cunningham, Anthony Lamar

    Polymer nanocomposites are a class of materials containing nanoparticles with a large interfacial surface area. Only a small quantity of nanoparticles are needed to provide superior multifunctional properties; such as mechanical, thermal, electrical, and moisture absorption properties in polymers. Nanoparticles tend to agglomerate, so special techniques are required for homogeneous distribution. Nanosilica is now readily available as colloidal sols, for example; Nanopox RTM F400 (supplied by Evonik Nanoresins AG, Germany). The nanoparticles are first synthesized from aqueous sodium silicate solution, and then undergo a surface modification process with organosilane and matrix exchange. F400 contains 40%wt silica nanoparticles colloidally dispersed in a DGEBA epoxy resin. The mean particle diameter is about 20 nm with a narrow distribution range of about 5 to 35 nm. The objectives of this study are to develop a reproducible processing method for nanosilica enhanced resin systems used in the manufacturing of fiber reinforced composites that will be characterized for mechanical and thermal properties. Research has concluded that shows improvements in the properties of the matrix material when processed in loading variations of 0 to 25%wt silica nanoparticles. The loadings were also used to manufacture fiberglass reinforced nanocomposite laminates and also tested for mechanical and thermal properties.

  15. Gated Silica Mesoporous Materials in Sensing Applications

    PubMed Central

    Sancenón, Félix; Pascual, Lluís; Oroval, Mar; Aznar, Elena; Martínez-Máñez, Ramón

    2015-01-01

    Silica mesoporous supports (SMSs) have a large specific surface area and volume and are particularly exciting vehicles for delivery applications. Such container-like structures can be loaded with numerous different chemical substances, such as drugs and reporters. Gated systems also contain addressable functions at openings of voids, and cargo delivery can be controlled on-command using chemical, biochemical or physical stimuli. Many of these gated SMSs have been applied for drug delivery. However, fewer examples of their use in sensing protocols have been reported. The approach of applying SMSs in sensing uses another concept—that of loading pores with a reporter and designing a capping mechanism that is selectively opened in the presence of a target analyte, which results in the delivery of the reporter. According to this concept, we provide herein a complete compilation of published examples of probes based on the use of capped SMSs for sensing. Examples for the detection of anions, cations, small molecules and biomolecules are provided. The diverse range of gated silica mesoporous materials presented here highlights their usefulness in recognition protocols. PMID:26491626

  16. Bimodal mesoporous silica with bottleneck pores.

    PubMed

    Reber, M J; Brühwiler, D

    2015-11-01

    Bimodal mesoporous silica consisting of two sets of well-defined mesopores is synthesized by a partial pseudomorphic transformation of an ordered mesoporous starting material (SBA-15 type). The introduction of a second set of smaller mesopores (MCM-41 type) establishes a pore system with bottlenecks that restricts the access to the core of the bimodal mesoporous silica particles. The particle size and shape of the starting material are retained, but micropores present in the starting material disappear during the transformation, leading to a true bimodal mesoporous product. A varying degree of transformation allows the adjustment of the pore volume contribution of the two mesopore domains. Information on the accessibility of the mesopores is obtained by the adsorption of fluorescence-labeled poly(amidoamine) dendrimers and imaging by confocal laser scanning microscopy. This information is correlated with nitrogen sorption data to provide insights regarding the spatial distribution of the two mesopore domains. The bimodal mesoporous materials are excellent model systems for the investigation of cavitation effects in nitrogen desorption isotherms. PMID:26399172

  17. Epoxy Crosslinked Silica Aerogels (X-Aerogels)

    NASA Technical Reports Server (NTRS)

    fabrizio, Eve; Ilhan, Faysal; Meador, Mary Ann; Johnston, Chris; Leventis, Nicholas

    2004-01-01

    NASA is interested in the development of strong lightweight materials for the dual role of thermal insulator and structural component for space vehicles; freeing more weight for useful payloads. Aerogels are very-low density materials (0.010 to 0.5 g/cc) that, due to high porosity (meso- and microporosity), can be, depending on the chemical nature of the network, ideal thermal insulators (thermal conductivity approx. 15 mW/mK). However, aerogels are extremely fragile. For practical application of aerogels, one must increase strength without compromising the physical properties attributed to low density. This has been achieved by templated growth of an epoxy polymer layer that crosslinks the "pearl necklace" network of nanoparticles: the framework of a typical silica aerogel. The requirement for conformal accumulation of the epoxy crosslinker is reaction both with the surface of silica and with itself. After cross-linking, the strength of a typical aerogel monolith increases by a factor of 200, in the expense of only a 2-fold increase in density. Strength is increased further by coupling residual unreacted epoxides with diamine.

  18. Gated Silica Mesoporous Materials in Sensing Applications.

    PubMed

    Sancenón, Félix; Pascual, Lluís; Oroval, Mar; Aznar, Elena; Martínez-Máñez, Ramón

    2015-08-01

    Silica mesoporous supports (SMSs) have a large specific surface area and volume and are particularly exciting vehicles for delivery applications. Such container-like structures can be loaded with numerous different chemical substances, such as drugs and reporters. Gated systems also contain addressable functions at openings of voids, and cargo delivery can be controlled on-command using chemical, biochemical or physical stimuli. Many of these gated SMSs have been applied for drug delivery. However, fewer examples of their use in sensing protocols have been reported. The approach of applying SMSs in sensing uses another concept-that of loading pores with a reporter and designing a capping mechanism that is selectively opened in the presence of a target analyte, which results in the delivery of the reporter. According to this concept, we provide herein a complete compilation of published examples of probes based on the use of capped SMSs for sensing. Examples for the detection of anions, cations, small molecules and biomolecules are provided. The diverse range of gated silica mesoporous materials presented here highlights their usefulness in recognition protocols. PMID:26491626

  19. Temperature measurements of shocked silica aerogel foam

    NASA Astrophysics Data System (ADS)

    Falk, K.; McCoy, C. A.; Fryer, C. L.; Greeff, C. W.; Hungerford, A. L.; Montgomery, D. S.; Schmidt, D. W.; Sheppard, D. G.; Williams, J. R.; Boehly, T. R.; Benage, J. F.

    2014-09-01

    We present recent results of equation-of-state (EOS) measurements of shocked silica (SiO2) aerogel foam at the OMEGA laser facility. Silica aerogel is an important low-density pressure standard used in many high energy density experiments, including the novel technique of shock and release. Due to its many applications, it has been a heavily studied material and has a well-known Hugoniot curve. This work then complements the velocity and pressure measurements with additional temperature data providing the full EOS information within the warm dense matter regime for the temperature interval of 1-15 eV and shock velocities between 10 and 40 km/s corresponding to shock pressures of 0.3-2 Mbar. The experimental results were compared with hydrodynamic simulations and EOS models. We found that the measured temperature was systematically lower than suggested by theoretical calculations. Simulations provide a possible explanation that the emission measured by optical pyrometry comes from a radiative precursor rather than from the shock front, which could have important implications for such measurements.

  20. Temperature measurements of shocked silica aerogel foam.

    PubMed

    Falk, K; McCoy, C A; Fryer, C L; Greeff, C W; Hungerford, A L; Montgomery, D S; Schmidt, D W; Sheppard, D G; Williams, J R; Boehly, T R; Benage, J F

    2014-09-01

    We present recent results of equation-of-state (EOS) measurements of shocked silica (SiO_{2}) aerogel foam at the OMEGA laser facility. Silica aerogel is an important low-density pressure standard used in many high energy density experiments, including the novel technique of shock and release. Due to its many applications, it has been a heavily studied material and has a well-known Hugoniot curve. This work then complements the velocity and pressure measurements with additional temperature data providing the full EOS information within the warm dense matter regime for the temperature interval of 1-15 eV and shock velocities between 10 and 40 km/s corresponding to shock pressures of 0.3-2 Mbar. The experimental results were compared with hydrodynamic simulations and EOS models. We found that the measured temperature was systematically lower than suggested by theoretical calculations. Simulations provide a possible explanation that the emission measured by optical pyrometry comes from a radiative precursor rather than from the shock front, which could have important implications for such measurements.

  1. Cobalt oxide silica membranes for desalination.

    PubMed

    Lin, Chun Xiang C; Ding, Li Ping; Smart, Simon; da Costa, João C Diniz

    2012-02-15

    This work shows for the first time the potential of cobalt oxide silica (CoO(x)Si) membranes for desalination of brackish (1 wt.% NaCl), seawater (3.5 wt.% NaCl) and brine (7.5-15 wt.% NaCl) concentrations at feed temperatures between 25 and 75 °C. CoO(x)Si xerogels were synthesised via a sol-gel method including TEOS, cobalt nitrate hydrate and peroxide. Initial hydrothermal exposure (<2 days) of xerogels prepared with various pH (3-6) resulted in densification of the xerogel via condensation reactions within the silica matrix, with the xerogel synthesised at pH 5 the most resistant. Subsequent exposure was not found to significantly alter the pore structure of the xerogels, suggesting they were hydrostable and that the pore sizes remained at molecular sieving dimensions. Membranes were then synthesised using identical sol-gel conditions to the xerogel samples and testing showed that elevated feed temperatures resulted in increased water fluxes, whilst increasing the saline feed concentration resulted in decreased water fluxes. The maximum flux observed was 1.8 kg m(-2) h(-1) at 75 °C for a 1 wt.% NaCl feed concentration. The salt rejection was consistently in excess of 99%, independent of either the testing temperature or salt feed concentration.

  2. Temperature measurements of shocked silica aerogel foam

    SciTech Connect

    Falk, K.; McCoy, C. A.; Fryer, C. L.; Greeff, C. W.; Hungerford, A. L.; Montgomery, D. S.; Schmidt, D. W.; Sheppard, D. G.; Williams, J. R.; Boehly, T. R.; Benage, J. F.

    2014-09-12

    We present recent results of equation-of-state (EOS) measurements of shocked silica (SiO2) aerogel foam at the OMEGA laser facility. Silica aerogel is an important low-density pressure standard used in many high energy density experiments, including the novel technique of shock and release. Due to its many applications, it has been a heavily studied material and has a well-known Hugoniot curve. This work then complements the velocity and pressure measurements with additional temperature data providing the full EOS information within the warm dense matter regime for the temperature interval of 1–15 eV and shock velocities between 10 and 40 km/s corresponding to shock pressures of 0.3–2 Mbar. The experimental results were compared with hydrodynamic simulations and EOS models. We found that the measured temperature was systematically lower than suggested by theoretical calculations. As a result, simulations provide a possible explanation that the emission measured by optical pyrometry comes from a radiative precursor rather than from the shock front, which could have important implications for such measurements.

  3. Temperature measurements of shocked silica aerogel foam

    DOE PAGES

    Falk, K.; McCoy, C. A.; Fryer, C. L.; Greeff, C. W.; Hungerford, A. L.; Montgomery, D. S.; Schmidt, D. W.; Sheppard, D. G.; Williams, J. R.; Boehly, T. R.; et al

    2014-09-12

    We present recent results of equation-of-state (EOS) measurements of shocked silica (SiO2) aerogel foam at the OMEGA laser facility. Silica aerogel is an important low-density pressure standard used in many high energy density experiments, including the novel technique of shock and release. Due to its many applications, it has been a heavily studied material and has a well-known Hugoniot curve. This work then complements the velocity and pressure measurements with additional temperature data providing the full EOS information within the warm dense matter regime for the temperature interval of 1–15 eV and shock velocities between 10 and 40 km/s correspondingmore » to shock pressures of 0.3–2 Mbar. The experimental results were compared with hydrodynamic simulations and EOS models. We found that the measured temperature was systematically lower than suggested by theoretical calculations. As a result, simulations provide a possible explanation that the emission measured by optical pyrometry comes from a radiative precursor rather than from the shock front, which could have important implications for such measurements.« less

  4. Shape matters when engineering mesoporous silica-based nanomedicines.

    PubMed

    Hao, Nanjing; Li, Laifeng; Tang, Fangqiong

    2016-04-01

    Mesoporous silica nanomaterials have been successfully employed in the development of novel carriers for drug delivery. Numerous studies have been reported on engineering mesoporous silica-based carriers for drug loading, release, cellular uptake, and biocompatibility. A number of design parameters that govern the in vitro and in vivo performance of the carriers, including particle diameter, surface chemistry, and pore size, have been tuned to optimize nanomedicine efficacy. However, particle shape, which may generate a high impact on nanomedicine performance, has still not been thoroughly investigated. This is probably due to the limited availability of strategies and techniques to produce non-spherical mesoporous silica nanomaterials. Recent breakthroughs in controlling the particle shape of mesoporous silica nanomaterials have confirmed the important roles of shape on nanomedicine development. This review article introduces various fabrication methods for non-spherical mesoporous silica nanomaterials, including rod, ellipsoid, film, platelet/sheet, and cube, and the roles of particle shape in nanomedicine applications. PMID:26818852

  5. Water dissociation on silica in the presence of atomic platinum

    NASA Astrophysics Data System (ADS)

    Klett, Joachim; Elger, Benjamin; Krähling, Stephan; Kaiser, Bernhard; Jaegermann, Wolfram; Schäfer, Rolf

    2016-07-01

    We have investigated the adsorption of water on well-defined silica and silica/Pt interfaces by synchrotron X-Ray Photoelectron Spectroscopy (SXPS). For that purpose silica surfaces grown on Si have been covered with atomic platinum in order to facilitate water dissociation. Water was adsorbed from the gas phase at cryogenic temperatures and its dissociation was observed on clean and platinum coated surfaces. After desorption the adsorbed hydroxides decompose on the blank surface, whereas the hydroxides remain stable if the surface was modified with platinum. The principal reversibility of the hydroxylation process implies the necessity of point defects in order to stabilize hydroxides on well-ordered silica surfaces. Deposited platinum atoms are able to stabilize hydroxides in their proximity and act as an acceptor state on the silica surface.

  6. Adsorption Characteristics of Silica Gels Treated with Fluorinated Silylation Agents

    PubMed

    Monde; Nakayama; Yano; Yoko; Konakahara

    1997-01-01

    Branched-chain polyfluorosilane (monochlorodimethyl[4,4-bis(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoroheptyl)-bonded silica gels were prepared. The surface properties of the silica gels modified with various organic silanes were evaluated by the adsorption density of polar and nonpolar gases calculated from adsorption isotherms of nitrogen, carbon dioxide, and normal butane gases. The polyfluorocarbon-bonded silica gel surface was found to be both hydrophobic and oleophobic in nature, whereas the hydrocarbon-bonded silica gel surface was characterized only as hydrophobic. The trifunctional fluorinated silane provides the silica gel surface with a more hydrophilic nature than the monofunctional silane because of the formation of a denser polymeric coating layer with a larger number of silanols. PMID:9056313

  7. Silica Waste Utilisation Phase II - Preliminary Laboratory Results

    SciTech Connect

    Lund, J.W.; Boyd, T.L.

    1995-01-01

    A second phase of laboratory testing is being performed on waste silica from the Cerro Prieto geothermal field in Mexico. The main objective is to produce mixes of various combinations of hydrated lime, portland cement, and plastic fibers with the waste silica from disposal ponds to determine their suitability for use as insulating bricks in low cost housing. Silica-cement mixtures appear to have the highest flexural strength and resistance to weathering. Silica-lime mixtures appear to have the best insulating properties (lowest thermal conductivity). The addition of plastic fibers to the silica-lime mixture appears to improve both strength and weather resistance. Work is still in progress and will be completed in 1996 with the construction of various test walls in the Mexicali, Mexico area.

  8. Adsorption Characteristics of Silica Gels Treated with Fluorinated Silylation Agents

    PubMed

    Monde; Nakayama; Yano; Yoko; Konakahara

    1997-01-01

    Branched-chain polyfluorosilane (monochlorodimethyl[4,4-bis(trifluoromethyl)-5,5,6,6,7,7,7-heptafluoroheptyl)-bonded silica gels were prepared. The surface properties of the silica gels modified with various organic silanes were evaluated by the adsorption density of polar and nonpolar gases calculated from adsorption isotherms of nitrogen, carbon dioxide, and normal butane gases. The polyfluorocarbon-bonded silica gel surface was found to be both hydrophobic and oleophobic in nature, whereas the hydrocarbon-bonded silica gel surface was characterized only as hydrophobic. The trifunctional fluorinated silane provides the silica gel surface with a more hydrophilic nature than the monofunctional silane because of the formation of a denser polymeric coating layer with a larger number of silanols.

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

    PubMed

    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.

  10. High export of dissolved silica from the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D. W.; Arendt, K. E.; Yde, J. C.; Juul Pedersen, T.; Hopwood, M. J.; Rysgaard, S.; Meysman, F. J. R.

    2016-09-01

    Silica is an essential element for marine life and plays a key role in the biogeochemistry of the ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported to coastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial areas such as the Greenland Ice Sheet is presently poorly quantified and not accounted for in global budgets. Here we present data from two fjord systems adjacent to the Greenland Ice Sheet which reveal a large export of dissolved silica by glacial meltwater relative to other macronutrients. Upscaled to the entire Greenland Ice Sheet, the export of dissolved silica equals 22 ± 10 Gmol Si yr-1. When the silicate-rich meltwater mixes with upwelled deep water, either inside or outside Greenland's fjords, primary production takes place at increased silicate to nitrate ratios. This likely stimulates the growth of diatoms relative to other phytoplankton groups.

  11. Structural and analytical studies of silica accumulations in Equisetum hyemale.

    PubMed

    Sapei, Lanny; Gierlinger, Notburga; Hartmann, Jürgen; Nöske, Robert; Strauch, Peter; Paris, Oskar

    2007-10-01

    Horsetail (Equisetum spp.) is known as one of the strongest accumulators of silicon among higher terrestrial plants. We use the combination of position-resolved analytical techniques, namely microtomography, energy-dispersive X-Ray elemental mapping, Raman microscopy, as well as small-angle and wide-angle scattering of X-rays, to study the type, distribution and nanostructure of silica in the internodes of Equisetum hyemale. The predominant silicification pattern is a thin continuous layer on the entire outer epidermis with the highest density in particular knob regions of the long epidermal cells. The knob tips contain up to 33 wt% silicon in the form of pure hydrated amorphous silica, while the silica content is lower in the inner part of the knobs and on the continuous layer. In contrast to the knob tips, the silica in these regions lacks silanol groups and is proposed to be in close association with polysaccharides. No mentionable amount of crystalline silica is detected by wide-angle X-ray scattering. The small-angle X-ray scattering data are consistent with the presence of colloidal, sheet-like silica agglomerates with a thickness of about 2 nm. From these results we conclude that there are at least two distinct forms of silica in E. hyemale which may have different functions. The close association of silica with cell wall polymers suggests that they may act as a polymeric template that controls the shape and size of the colloidal silica particles similar to many other biominerals and mineralised tissues. We propose that owing to its specific distribution in E. hyemale, a protective role and possibly also an important biomechanical role are among the most likely functions of silica in these plants.

  12. Reevaluation of Vitrified High-Level Waste Form Criteria for Potential Cost Savings at the Defense Waste Processing Facility - 13598

    SciTech Connect

    Ray, J.W.; Marra, S.L.; Herman, C.C.

    2013-07-01

    At the Savannah River Site (SRS) the Defense Waste Processing Facility (DWPF) has been immobilizing SRS's radioactive high level waste (HLW) sludge into a durable borosilicate glass since 1996. Currently the DWPF has poured over 3,500 canisters, all of which are compliant with the U. S. Department of Energy's (DOE) Waste Acceptance Product Specifications for Vitrified High-Level Waste Forms (WAPS) and therefore ready to be shipped to a federal geologic repository for permanent disposal. Due to DOE petitioning to withdraw the Yucca Mountain License Application (LA) from the Nuclear Regulatory Commission (NRC) in 2010 and thus no clear disposal path for SRS canistered waste forms, there are opportunities for cost savings with future canister production at DWPF and other DOE producer sites by reevaluating high-level waste form requirements and compliance strategies and reducing/eliminating those that will not negatively impact the quality of the canistered waste form. (authors)

  13. A reevaluation of the common factor theory of shared variance among age, sensory function, and cognitive function in older adults.

    PubMed

    Anstey, K J; Luszcz, M A; Sanchez, L

    2001-01-01

    The common cause hypothesis of the relationship among age, sensory measures, and cognitive measures in very old adults was reevaluated. Both sensory function and processing speed were evaluated as mediators of the relationship between age and cognitive function. Cognitive function was a latent variable that comprised 3 factors including memory, speed, and verbal ability. The sample was population based and comprised very old adults (n = 894; mean age = 77.7, SD = 5.6 years) from the Australian Longitudinal Study of Ageing. The results showed that there was common variance in the cognitive factor shared by age, speed, vision, and hearing but that specific effects of age on cognition remained. Furthermore, speed did not fully mediate the effect of age or sensory function on cognition. Some age differences in cognitive performance are not explained by the same processes that explain age differences in sensory function and processing speed.

  14. Uncertainty reevaluation in determining the volume of a silicon sphere by spherical harmonics in an Avogadro project

    NASA Astrophysics Data System (ADS)

    Zhang, Ji-Tao; Wu, Xue-Jian; Li, Yan

    2011-09-01

    To determine the Avogadro constant with a target relative uncertainty of 2 × 10-8, the uncertainty component of the silicon sphere's volume introduced by the spherical harmonics method, which is usually used in determining the sphere's volume, is reevaluated. By means of representing the shape of the silicon sphere by an ellipsoid with Gaussian white noise in its diameters, the uncertainty of the current mapping methods based on the spherical harmonics theory can be estimated theoretically. It is evidenced that the uncertainty component attributed to the current mapping method is underestimated. To eliminate this effect as much as possible, the number of mapping points should be increased to more than before. Moreover, a new mapping method is proposed to accomplish the equal-area mapping with large number points on the silicon sphere.

  15. Regulations and guidelines should be strengthened urgently for re-evaluation on post-marketing medicines in China.

    PubMed

    Xie, Yan-Ming; Tian, Feng

    2013-07-01

    This paper reviewed the situation of regulations and guidelines on post-marketing medicines in the developed countries and in China. The developed countries have accumulated a lot of empirical principles and techniques on postmarketing surveillance (also named pharmacovigilance), therefore, their regulation systems are nearly perfect. In China, the regulations on post-marketing re-evaluation and relative technical guidelines do not cover the whole aspects, even lack in some important aspects, and long-term risk management mechanisms have not been established. So it is urgent to establish new regulations and improve the regulatory system in China based on the existing regulations and guidelines, by learning from the ideas of foreign advanced regulations, then fully integrating them with China's actual conditions, and cooperating with multidisciplinary researchers. PMID:23818198

  16. Re-evaluation of heat flow data near Parkfield, CA: Evidence for a weak San Andreas Fault

    USGS Publications Warehouse

    Fulton, P.M.; Saffer, D.M.; Harris, Reid N.; Bekins, B.A.

    2004-01-01

    Improved interpretations of the strength of the San Andreas Fault near Parkfield, CA based on thermal data require quantification of processes causing significant scatter and uncertainty in existing heat flow data. These effects include topographic refraction, heat advection by topographically-driven groundwater flow, and uncertainty in thermal conductivity. Here, we re-evaluate the heat flow data in this area by correcting for full 3-D terrain effects. We then investigate the potential role of groundwater flow in redistributing fault-generated heat, using numerical models of coupled heat and fluid flow for a wide range of hydrologic scenarios. We find that a large degree of the scatter in the data can be accounted for by 3-D terrain effects, and that for plausible groundwater flow scenarios frictional heat generated along a strong fault is unlikely to be redistributed by topographically-driven groundwater flow in a manner consistent with the 3-D corrected data. Copyright 2004 by the American Geophysical Union.

  17. Reevaluation Of Vitrified High-Level Waste Form Criteria For Potential Cost Savings At The Defense Waste Processing Facility

    SciTech Connect

    Ray, J. W.; Marra, S. L.; Herman, C. C.

    2013-01-09

    At the Savannah River Site (SRS) the Defense Waste Processing Facility (DWPF) has been immobilizing SRS's radioactive high level waste (HLW) sludge into a durable borosilicate glass since 1996. Currently the DWPF has poured over 3,500 canisters, all of which are compliant with the U. S. Department of Energy's (DOE) Waste Acceptance Product Specifications for Vitrified High-Level Waste Forms (WAPS) and therefore ready to be shipped to a federal geologic repository for permanent disposal. Due to DOE petitioning to withdraw the Yucca Mountain License Application (LA) from the Nuclear Regulatory Commission (NRC) in 2010 and thus no clear disposal path for SRS canistered waste forms, there are opportunities for cost savings with future canister production at DWPF and other DOE producer sites by reevaluating high-level waste form requirements and compliance strategies and reducing/eliminating those that will not negatively impact the quality of the canistered waste form.

  18. The investigation of the viscoelastic properties of silica/PMMA nanocomposites as a function of silica surface chemistry

    NASA Astrophysics Data System (ADS)

    Conway, Heather; Rende, Deniz; Ozisik, Rahmi

    2013-03-01

    Poly(methyl methacrylate), PMMA, has been used as an economic alternative to glass and polycarbonate in differing situations because of its lightweight, shatter resistance, and ease of processability. The uses of PMMA can be expanded if its weakness to impact force and its scratch resistance are improved. In the current study, viscoelastic properties of silica nanoparticle filled PMMA were investigated via nanoindentation experiments. Silica nanoparticles are known to increase the toughness of PMMA. In the current study, silica nanoparticles were chemically modified with fluorinated alkanes to alter nanofiller-polymer interactions. Results show that viscoelastic properties are strongly affected by silica surface chemistry and silica concentration. This work was partially supported by NSF CMMI-1200270 and DUE-1003574

  19. The annual silica cycle of the North Pacific subtropical gyre

    NASA Astrophysics Data System (ADS)

    Brzezinski, Mark A.; Krause, Jeffrey W.; Church, Matthew J.; Karl, David M.; Li, Binglin; Jones, Janice L.; Updyke, Brett

    2011-10-01

    Silica cycling in the upper 175 m of the North Pacific Subtropical Gyre was examined over a two year period (January 2008-December 2009) at the Hawaii Ocean Time-series (HOT) station ALOHA. Silicic acid concentrations in surface waters ranged from 0.6 to 1.6 μM, exhibiting no clear seasonal trends. Biogenic silica concentrations and silica production rates increased by an order of magnitude each summer following stratification of the upper 50 m reaching values of 157 nmol Si L -1 and 81 nmol Si L -1 d -1, in 2008 and 2009, respectively. Sea surface height anomalies together with analyses of variability in isothermal surfaces at 150-175 m indicated that the summer periods of elevated biogenic silica were associated with anticyclonic mesoscale features during both years. Lithogenic silica concentrations increased in the spring during the known period of maximum atmospheric dust concentrations with maximum values of 36 nmol Si L -1 in the upper 10 m. Dust deposition would enhance levels of dissolved iron in surface waters, but there was no response of diatom biomass or silica production to increases in near-surface ocean lithogenic silica concentrations suggesting iron sufficiency of diatom silica production rates. Low ambient silicic acid concentrations restricted silica production rates to an average of 43% of maximum potential rates. Si sufficiency only occurred during the summer period when diatom biomass was elevated suggesting that bloom diatoms are adapted to exploit low silicic acid concentrations. Annual silica production at HOT is estimated to be 63 mmol Si m -2 a -1 with summer blooms contributing 29% of the annual total. Diatoms are estimated to account for 3-7% of total phytoplankton primary productivity, but 9-20% of organic carbon export confirming past suggestions that diatoms are relatively minor contributors to primary productivity and autotrophic biomass, but important contributors to new and export production in oligotrophic open-ocean ecosystems

  20. Effects of major depression, aging and gender upon calculated diurnal free plasma cortisol concentrations: a re-evaluation study.

    PubMed

    Deuschle, M; Weber, B; Colla, M; Depner, M; Heuser, I

    1998-12-01

    Depression, aging and female gender are associated with increased diurnal concentrations of total plasma cortisol. For the physical effects of hypercortisolemia, however, it is generally assumed that free rather than total plasma cortisol concentrations are of importance. Herein, we report a mathematical approach to determine free plasma cortisol concentrations on the basis of total cortisol, corticosteroid binding-globulin (CBG) and albumin plasma concentrations. This approach was used to re-evaluate two sets of data in order to estimate the effect of depression as well as the effect of aging and gender upon free plasma cortisol concentrations. Comparing male depressed patients with healthy controls, we found 24-hour free cortisol minima (MIN: 4.1 +/- 1.8 vs. 1.6 +/- 1.1 nmol/l, p < 0.0001), mean (MEAN: 25.5 +/- 6.7 vs. 10.4 +/- 2.7 nmol/l, p < 0.0001) and maximal (MAX: 85.3 +/- 23.3 vs. 45.2 +/- 15. 8 nmol/l, p < 0.0001) concentrations to be significantly increased in depressed patients. In general, the impact of depression upon total plasma cortisol were not only maintained, but stronger regarding free plasma cortisol. Also, age was associated with free plasma cortisol MIN (F1,30= 10.8, p < 0.003) and free plasma cortisol MEAN (F1,30 = 8.9, p < 0.006). All effects of age upon total plasma cortisol were generally also found in free plasma cortisol, though with less impact. No effect of gender upon any of the given free plasma cortisol outcome variables was found. Taken together, our re-evaluation clearly shows not only depression but also aging to be associated with increases in free plasma cortisol concentrations. This finding is in line with the observation that in both conditions medical problems triggered and/or maintained by glucocorticoids (e.g. osteoporosis) are frequently seen.

  1. Reevaluation of waterborne releases of radioactive materials from the Mayak Production Association into the Techa River in 1949-1951.

    PubMed

    Degteva, M O; Shagina, N B; Vorobiova, M I; Anspaugh, L R; Napier, B A

    2012-01-01

    The Mayak Production Association was the first site for the production of weapons-grade plutonium in Russia. Early operations led to the waterborne release of radioactive materials into the small Techa River. Residents living downstream used river water for drinking and other purposes. The releases and subsequent flooding resulted in deposition of sediments along the shoreline and on floodplain soil. Primary routes of exposure were external dose from the deposited sediments and ingestion of 90Sr and other radionuclides. Study of the Techa River Cohort has revealed an increased incidence of leukemia and solid cancers. Epidemiologic studies are supported by extensive dose-reconstruction activities that have led to various versions of a Techa River Dosimetry System (TRDS). The correctness of the TRDS has been challenged by the allegation that releases of short-lived radionuclides were much larger than those used in the TRDS. Although the dosimetry system depends more upon measurements of 90Sr in humans and additional measurements of radionuclides and of exposure rates in the environment, a major activity has been undertaken to define more precisely the time-dependent rates of release and their radionuclide composition. The major releases occurred during 1950-1951 in the form of routine releases and major accidental releases. The reevaluated amount of total release is 114 PBq, about half of which was from accidents that occurred in late 1951. The time-dependent composition of the radionuclides released has also been reevaluated. The improved understanding presented in this paper is possible because of access to many documents not previously available. PMID:22134076

  2. Governmental re-evaluation of the committed effective dose received by emergency workers at the TEPCO Fukushima Daiichi NPP accident.

    PubMed

    Yasui, Shojiro

    2015-01-01

    In April 2013, the Ministry of Health, Labour and Welfare (MHLW) noticed that significant discrepancies were present between the committed effective dose (CED) data for emergency workers at the TEPCO Fukushima Daiichi Nuclear Power Plant provided by TEPCO and that reported by five primary contractors. The MHLW, based on re-evaluation of the data, provided administrative guidance which required TEPCO and the five primary contractors to readjust the CED data for 479 workers (2.5% of 19,346 emergency workers). Of these, data for 450 workers from the primary contractors were readjusted based on the change in assessment methods. Doses were readjusted to higher values for 431 workers and doses were readjusted to lower values for 19 workers, CED data were corrected due to calculation errors for 29 workers from seven contractors, 12 additional workers were found to have received more than 50 mSv but no more than 100 mSv, an increase of 1.7% over the previously established count of 723 workers who had received that dose. Six additional workers were found to have received more than 100 mSv, an increase of 3.6% compared with the previous count of 167 workers. Major issues addressed during re-evaluation included: a) selection of intake scenario for the calculation of the residual activity ratio; b) assumptions about the intake date; c) assessments of exposure to radiation from (132)I and (132)Te; and d) assumptions about (131)I exposure in cases where (131)I was undetectable. Regarding the divergent CED data of 138 workers, the MHLW also confirmed that the CEDs assessed by the primary contractors were valid. To prevent the recurrence of similar incidents, the MHLW issued administrative guidance documents to TEPCO and primary contractors to employ standardized CED assessment methods on July 5. 2013. PMID:25585203

  3. REEVALUATION OF WATERBORNE RELEASES OF RADIOACTIVE MATERIALS FROM THE MAYAK PRODUCTION ASSOCIATION INTO THE TECHA RIVER IN 1949-1951

    SciTech Connect

    Degteva, M. O.; Shagina, N. B.; Vorobiova, M. I.; Anspaugh, L. R.; Napier, Bruce A.

    2012-01-01

    The Mayak Production Association was the first site for the production of weapon-grade plutonium in Russia. Early operations led to the waterborne release of large amounts of radioactive materials into the small Techa River. Residents living downstream used river water for drinking and other purposes. The releases and subsequent flooding resulted in the deposition of sediments along the shoreline and on floodplain soil. Primary routes of exposure were external dose from the deposited sediments and the ingestion of 90Sr and other radionuclides. Study of the Techa River Cohort has revealed an increased incidence of leukemia and solid cancers. These epidemiologic studies are supported by extensive dose-reconstruction activities that have led to the creation of various versions of a Techa River Dosimetry System (TRDS). The correctness of the TRDS has been challenged by the allegation that releases of short-lived radionuclides were much larger than those used in the TRDS. Although the dosimetry system depends more upon the measurements of 90Sr in humans and additional measurements of radionuclides and of exposure rates in the environment, a major activity has been undertaken to define more precisely the time-dependent rates of release and radionuclide composition of the releases. The major releases occurred during 1950-1951. In addition to routine releases major accidental releases occurred. The re-evaluated amount of total release is 114 PBq, about half of which was from accidents that occurred in late 1951. The composition of the radionuclides released has also been re-evaluated; this composition changed with time.

  4. Letter to the Editor, Response to Commentary "Re-Evaluation of the Big Blue® Mouse Assay of Propiconazole Suggests Lack of Mutagenicity"

    EPA Science Inventory

    In their commentary titled "Re-Evaluation of the Big Blue® Mouse Assay of Propiconazole Suggests Lack of Mutagenicity", Shane et 01. present an overview of portions of our previously reported work examining the potential for some conazole fungicides to induce increases in mutant ...

  5. Constraining silica diagenesis in methane-seep deposits

    NASA Astrophysics Data System (ADS)

    Smrzka, Daniel; Kraemer, Stephan; Zwicker, Jennifer; Birgel, Daniel; Fischer, David; Kasten, Sabine; Goedert, James; Peckmann, Jörn

    2015-04-01

    Silicified fossils and silicified early diagenetic carbonate minerals as well as authigenic silica phases are common in ancient seep limestones. Silicification of calcareous fossils facilitates the preservation of even fine details and is therefore of great interest to paleontologists, permitting a reliable taxonomic identification of the chemosynthesis-based taxa that lived at ancient hydrocarbon seeps. Four methane-seep limestones of Paleozoic, Mesozoic, and Cenozoic age with abundant silica phases are compared in this study; one, an Eocene seep deposit on the north shore of the Columbia River at Knappton, western Washington State, USA, is described for the first time. Its lithology and fabrics, negative δ13Ccarbonate values as low as -27.6‰, and 13C-depleted biomarkers of archaea involved in the anaerobic oxidation of methane (AOM) reveal that the carbonate rock formed at a methane seep. The background sediments of the studied Phanerozoic seep limestones contain abundant siliceous microfossils, radiolarian tests in case of the Late Carboniferous Dwyka Group deposits from Namibia and the Late Triassic Graylock Butte deposits from eastern Oregon (USA), diatom frustules in case of the Eocene Knappton limestone and an Oligocene seep deposit from the Lincoln Creek Formation (western Washington State, USA). These microfossils are regarded as the source of dissolved silica, causing silicification and silica precipitation. All seep limestones used in this study are characterized by very similar paragenetic sequences. Silicified fossils include brachiopods and worm tubes, silica cements include microquartz, fibrous microcrystalline silica, and megaquartz. The silica cements formed after the AOM-derived cements ceased to precipitate but before equant calcite spar formed. Numerical experiments using the computer code PHREEQC were conducted to test the hypothesis that (1) AOM increases the pH of pore waters and that (2) this pH increase subsequently mobilizes biogenic

  6. Morphological characterization of silica obtained by calcination of methacrylic and epoxy - silica hybrid systems

    NASA Astrophysics Data System (ADS)

    Tescione, F.; Lionetto, F.; Corcione, C. Esposito; Buonocore, G. G.; Striani, R.; Lavorgna, M.; Frigione, M.

    2016-05-01

    The work is addressed to investigating the potentiality of calcination of organic-inorganic (O-I) hybrids as a feasible approach to produce silica particles, at mild temperature conditions and with tailored morphology. Two different innovative hybrid systems were obtained through sol-gel process with a siloxane content ranging from 6 to 26wt%. The two O-I hybrids differed for i) the organic matrix (methacrylic or epoxy), ii) its crosslinking mechanism (photopolymerization for methacrylic systems or thermal cold-cure for epoxy systems) and iii) the rate ratio between sol-gel and crosslinking reactions. Different characterization techniques were used to understand the effect of composition and curing method on the morphology of the silica obtained from O-I hybrids after calcination in air. The results confirm the morphology and properties of silica particles in terms of surface and porosity may be tailored over a wide range by varying the composition and nature of organic and inorganic precursors of hybrids.

  7. Laser Damage Precursors in Fused Silica

    SciTech Connect

    Miller, P; Suratwala, T; Bude, J; Laurence, T A; Shen, N; Steele, W A; Feit, M; Menapace, J; Wong, L

    2009-11-11

    There is a longstanding, and largely unexplained, correlation between the laser damage susceptibility of optical components and both the surface quality of the optics, and the presence of near surface fractures in an optic. In the present work, a combination of acid leaching, acid etching, and confocal time resolved photoluminescence (CTP) microscopy has been used to study laser damage initiation at indentation sites. The combination of localized polishing and variations in indentation loads allows one to isolate and characterize the laser damage susceptibility of densified, plastically flowed and fractured fused silica. The present results suggest that: (1) laser damage initiation and growth are strongly correlated with fracture surfaces, while densified and plastically flowed material is relatively benign, and (2) fracture events result in the formation of an electronically defective rich surface layer which promotes energy transfer from the optical beam to the glass matrix.

  8. Diatomite releases silica during spirit filtration.

    PubMed

    Gómez, J; Gil, M L A; de la Rosa-Fox, N; Alguacil, M

    2014-09-15

    The purpose of this study was to ascertain whether diatomite is an inert filter aid during spirit filtration. Surely, any compound with a negative effect on the spirit composition or the consumer's health could be dissolved. In this study different diatomites were treated with 36% vol. ethanol/water mixtures and the amounts and structures of the extracted compounds were determined. Furthermore, Brandy de Jerez was diatomite- and membrane-filtered at different temperatures and the silicon content was analysed. It was found that up to 0.36% by weight of diatomite dissolved in the aqueous ethanol and amorphous silica, in the form of hollow spherical microparticles, was the most abundant component. Silicon concentrations in Brandy de Jerez increased by up to 163.0% after contact with diatomite and these changes were more marked for calcined diatomite. In contrast, reductions of more than 30% in silicon concentrations were achieved after membrane filtration at low temperatures.

  9. Envelope Solitons in Acoustically Dispersive Vitreous Silica

    NASA Technical Reports Server (NTRS)

    Cantrell, John H.; Yost, William T.

    2012-01-01

    Acoustic radiation-induced static strains, displacements, and stresses are manifested as rectified or dc waveforms linked to the energy density of an acoustic wave or vibrational mode via the mode nonlinearity parameter of the material. An analytical model is developed for acoustically dispersive media that predicts the evolution of the energy density of an initial waveform into a series of energy solitons that generates a corresponding series of radiation-induced static strains (envelope solitons). The evolutionary characteristics of the envelope solitons are confirmed experimentally in Suprasil W1 vitreous silica. The value (-11.9 plus or minus 1.43) for the nonlinearity parameter, determined from displacement measurements of the envelope solitons via a capacitive transducer, is in good agreement with the value (-11.6 plus or minus 1.16) obtained independently from acoustic harmonic generation measurements. The agreement provides strong, quantitative evidence for the validity of the model.

  10. Physical Sate of Shocked Silica Aerogel

    NASA Astrophysics Data System (ADS)

    Greeff, Carl; Benage, John; Falk, Katerina; Fryer, Christopher; Boehly, Thomas; McCoy, Chad

    2013-06-01

    We have performed laser driven shock experiments on silica aerogel of initial density 0.2 g/cc. These experiments employed streaked optical pyrometry as a temperature diagnostic. The Hugoniot states accessed have densities between the critical density and the crystal density, and temperatures of a few eV. These densities are high enough that bonding is non-negligible and the electronic spectrum is strongly modified from that of the constituent atoms. The temperature is high enough for electronic excitation to be important, but low compared to the full ionization limit. We examine the physical basis of Sesame equation of state models in this regime with special attention to uncertainty in the calculated temperature. We present new results from quantum molecular dynamics simulations for the structural and electronic properties in the shocked state, and use these results to improve the Sesame models.

  11. Mesoporous silica nanoparticles inhibit cellular respiration.

    PubMed

    Tao, Zhimin; Morrow, Matthew P; Asefa, Tewodros; Sharma, Krishna K; Duncan, Cole; Anan, Abhishek; Penefsky, Harvey S; Goodisman, Jerry; Souid, Abdul-Kader

    2008-05-01

    We studied the effect of two types of mesoporous silica nanoparticles, MCM-41 and SBA-15, on mitochondrial O 2 consumption (respiration) in HL-60 (myeloid) cells, Jurkat (lymphoid) cells, and isolated mitochondria. SBA-15 inhibited cellular respiration at 25-500 microg/mL; the inhibition was concentration-dependent and time-dependent. The cellular ATP profile paralleled that of respiration. MCM-41 had no noticeable effect on respiration rate. In cells depleted of metabolic fuels, 50 microg/mL SBA-15 delayed the onset of glucose-supported respiration by 12 min and 200 microg/mL SBA-15 by 34 min; MCM-41 also delayed the onset of glucose-supported respiration. Neither SBA-15 nor MCM-41 affected cellular glutathione. Both nanoparticles inhibited respiration of isolated mitochondria and submitochondrial particles.

  12. Modified silica sol coatings for surface enhancement of leather.

    PubMed

    Mahltig, Boris; Vossebein, Lutz; Ehrmann, Andrea; Cheval, Nicolas; Fahmi, Amir

    2012-06-01

    The presented study reports on differently modified silica sols for coating applications on leather. Silica sols are prepared by acidic hydrolysis of tetraethoxysilane and modified by silane compounds with fluorinated and non-fluorinated alkylgroups. In contrast to many earlier investigations regarding sol-gel applications on leather, no acrylic resin is used together with the silica sols when applying on leather. The modified silica particles are supposed to aggregate after application, forming thus a modified silica coating on the leather substrate. Scanning electron microscopy investigation shows that the applied silica coatings do not fill up or close the pores of the leather substrate. However, even if the pores of the leather are not sealed by this sol-gel coating, an improvement of the water repellent and oil repellent properties of the leather substrates are observed. These improved properties of leather by application of modified silica sols can provide the opportunity to develop sol-gel products for leather materials present in daily life.

  13. Antioxidative and antiinflammatory activities of quercetin-loaded silica nanoparticles.

    PubMed

    Lee, Ga Hyun; Lee, Sung June; Jeong, Sang Won; Kim, Hyun-Chul; Park, Ga Young; Lee, Se Geun; Choi, Jin Hyun

    2016-07-01

    Utilizing the biological activities of compounds by encapsulating natural components in stable nanoparticles is an important strategy for a variety of biomedical and healthcare applications. In this study, quercetin-loaded silica nanoparticles were synthesized using an oil-in-water microemulsion method, which is a suitable system for producing functional nanoparticles of controlled size and shape. The resulting quercetin-loaded silica nanoparticles were spherical, highly monodispersed, and stable in an aqueous system. Superoxide radical scavenging effects were found for the quercetin-loaded silica nanoparticles as well as free quercetin. The quercetin-loaded silica nanoparticles showed cell viability comparable to that of the controls. The amounts of proinflammatory cytokines produced by macrophages, such as interleukin 1 beta, interleukin 6, and tumor necrosis factor alpha, were reduced significantly for the quercetin-loaded silica nanoparticles. These results suggest that the antioxidative and antiinflammatory activities of quercetin are maintained after encapsulation in silica. Silica nanoparticles can be used for the effective and stable incorporation of biologically active natural components into composite biomaterials. PMID:27038916

  14. Phase behavior and rheological characterization of silica nanoparticle gel

    NASA Astrophysics Data System (ADS)

    Metin, Cigdem O.; Rankin, Kelli M.; Nguyen, Quoc P.

    2014-01-01

    Preferential injection into high permeability thief zones or fractures can result in early breakthrough at production wells and large unswept areas of high oil saturation, which impact the economic life of a well. A variety of conformance control techniques, including polymer and silica gel treatments, have been designed to block flow through the swept zones. Over a certain range of salinities, silica nanoparticle suspensions form a gel in bulk phase behavior tests. These gels have potential for in situ flow diversion, but in situ flow tests are required to determine their applicability. To determine the appropriate scope of the in situ tests, it is necessary to obtain an accurate description of nanoparticle phase behavior and gel rheology. In this paper, the equilibrium phase behavior of silica nanoparticle solutions in the presence of sodium chloride (NaCl) is presented with four phase regions classified as a function of salinity and nanoparticle concentration. Once the gelation window was clearly defined, rheology experiments of silica nanoparticle gels were also carried out. Gelation time decreases exponentially as a function of silica concentration, salinity, and temperature. Following a power law behavior, the storage modulus, G', increases with particle concentration. Steady shear measurements show that silica nanoparticle gels exhibit non-Newtonian, shear thinning behavior. This comprehensive study of the silica nanoparticle gels has provided a clear path forward for in situ tests to determine the gel's applicability for conformance control operations.

  15. Size- and structure-dependent toxicity of silica particulates

    NASA Astrophysics Data System (ADS)

    Hanada, Sanshiro; Miyaoi, Kenichi; Hoshino, Akiyoshi; Inasawa, Susumu; Yamaguchi, Yukio; Yamamoto, Kenji

    2011-03-01

    Nano- and micro-particulates firmly attach with the surface of various biological systems. In some chronic pulmonary disease such as asbestosis and silicosis, causative particulates will induce chronic inflammatory disorder, followed by poor prognosis diseases. However, nano- and micro-scale specific toxicity of silica particulates is not well examined enough to recognize the risk of nano- and micro-particulates from the clinical aspect. To clarify the effect of the size and structure of silica particulates on the cellular damage and the biological response, we assessed the cytotoxicity of the various kinds of silica particles including amorphous and crystalline silica, in mouse alveolar macrophage culture, focusing on the fibrotic and inflammatory response. Our study showed that the cytotoxicity, which depends on the particle size and surface area, is correlated with their inflammatory response. By contrast, production of TGF-β, which is one of the fibrotic agents in lung, by addition of crystal silica was much higher than that of amorphous silica. We conclude that fibrosis and inflammation are induced at different phases and that the size- and structure-differences of silica particulates affect the both biological responses, caused by surface activity, radical species, and so on.

  16. Insitu grafting silica nanoparticles reinforced nanocomposite hydrogels

    NASA Astrophysics Data System (ADS)

    Yang, Jun; Han, Chun-Rui; Duan, Jiu-Fang; Xu, Feng; Sun, Run-Cang

    2013-10-01

    Highly flexible nanocomposite hydrogels were prepared by using silica nanoparticles (SNPs) as fillers and multi-functional cross-links to graft hydrophilic poly(acrylic acid) (PAA) by free radical polymerization from an aqueous solution. The SNPs were collected by neighboring polymer chains and dispersed uniformly within a PAA matrix. The mechanical properties of the nanocomposite hydrogels were tailored by the concentration of SNPs according to the percolation model. It was proposed that covalent bonds of adsorbed chains on the filler surface resulted in the formation of a shell of an immobilized glassy layer and trapped entanglements, where the glassy polymer layer greatly enhanced the elastic modulus and the release of trapped entanglements at deformation contributed to the viscoelastic properties.Highly flexible nanocomposite hydrogels were prepared by using silica nanoparticles (SNPs) as fillers and multi-functional cross-links to graft hydrophilic poly(acrylic acid) (PAA) by free radical polymerization from an aqueous solution. The SNPs were collected by neighboring polymer chains and dispersed uniformly within a PAA matrix. The mechanical properties of the nanocomposite hydrogels were tailored by the concentration of SNPs according to the percolation model. It was proposed that covalent bonds of adsorbed chains on the filler surface resulted in the formation of a shell of an immobilized glassy layer and trapped entanglements, where the glassy polymer layer greatly enhanced the elastic modulus and the release of trapped entanglements at deformation contributed to the viscoelastic properties. Electronic supplementary information (ESI) available: FTIR spectra of SNP after silane treatment, dynamic oscillatory shear measurements as a function of frequency, constrained polymer chain analysis by a change in the peak height in loss factor spectra, molecular weight of grafted chains at different stages of gelation, prediction of the SNP reinforcing mechanism in the

  17. Electrochemical strain microscopy of silica glasses

    NASA Astrophysics Data System (ADS)

    Proksch, R.

    2014-08-01

    Piezoresponse Force Microscopy and Electrochemical Strain Microscopy (ESM) are two related techniques that have had considerable success in nano-scale probing of functional material properties. Both measure the strain of the sample in response to a localized electric field beneath a sharp conductive tip. In this work, a collection of commercially available glass samples were measured with a variety of Si cantilevers coated with different conductive metals. In some cases, these glasses showed significant hysteresis loops, similar in appearance to those measured on ferroelectric materials with spontaneous permanent electric dipoles. The magnitude of the electrochemical strain and hysteresis correlated well with the molar percentage of sodium in the glass material, with high sodium (soda-lime) glass showing large hysteresis and fused silica (pure SiO2) showing essentially no hysteresis. The "elephant-ear" shape of the hysteresis loops correlated well with it originating from relaxation behavior—an interpretation verified by observing the temperature dependent relaxation of the ESM response. Cation mobility in a disordered glass should have a low diffusion constant. To evaluate this diffusion constant, the temperature of the glass was varied between room temperature to ˜200 °C. Vanishing hysteresis as the temperature increased was associated with a decrease in the relaxation time of the electrochemical response. The hysteretic behavior changed drastically in this temperature range, consistent with bound surface water playing a large role in the relaxation. This demonstrates the ability of ESM to differentiate cationic concentrations in a range of silica glasses. In addition, since glass is a common sample substrate for, this provides some clear guidance for avoiding unwanted substrate crosstalk effects in piezoresponse and electrochemical strain response measurements.

  18. Series-Coupled Pairs of Silica Microresonators

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Iltchenko, Vladimir; Maleki, Lute; Handley, Tim

    2009-01-01

    Series-coupled pairs of whispering-gallery-mode optical microresonators have been demonstrated as prototypes of stable, narrow-band-pass photonic filters. Characteristics that are generally considered desirable in a photonic or other narrow-band-pass filter include response as nearly flat as possible across the pass band, sharp roll-off, and high rejection of signals outside the pass band. A single microresonator exhibits a Lorentzian filter function: its peak response cannot be made flatter and its roll-off cannot be made sharper. However, as a matter of basic principle applicable to resonators in general, it is possible to (1) use multiple resonators, operating in series or parallel, to obtain a roll-off sharper, and out-of-band rejection greater, relative to those of a Lorentzian filter function and (2) to make the peak response (the response within the pass band) flatter by tuning the resonators to slightly different resonance frequencies that span the pass band. The first of the two microresonators in each series-coupled pair was a microtorus made of germania-doped silica (containing about 19 mole percent germania), which is a material used for the cores of some optical fibers. The reasons for choosing this material is that exposing it to ultraviolet light causes it to undergo a chemical change that changes its index of refraction and thereby changes the resonance frequency. Hence, this material affords the means to effect the desired slight relative detuning of the two resonators. The second microresonator in each pair was a microsphere of pure silica. The advantage of making one of the resonators a torus instead of a sphere is that its spectrum of whispering-gallery-mode resonances is sparser, as needed to obtain a frequency separation of at least 100 GHz between resonances of the filter as a whole.

  19. The phagocytosis of crystalline silica particles by macrophages.

    PubMed

    Gilberti, Renée M; Joshi, Gaurav N; Knecht, David A

    2008-11-01

    Silicosis is a chronic lung disease induced by the inhalation of crystalline silica. Exposure of cultured macrophages to crystalline silica leads to cell death; however, the mechanism of cell-particle interaction, the fate of particles, and the cause of death are unknown. Time-lapse imaging shows that mouse macrophages avidly bind particles that settle onto the cell surface and that cells also extend protrusions to capture distant particles. Using confocal optical sectioning, silica particles were shown to be present within the cytoplasmic volume of live cells. In addition, electron microscopy and elemental analysis showed silica in internal cellular sections. To further examine the phagocytosis process, the kinetics of particle uptake was quantified using an assay in which cells were exposed to ovalbumin (OVA)-coated particles, and an anti-OVA antibody was used to distinguish surface-bound from internalized particles. Fc receptor-mediated uptake of antibody-coated silica particles was nearly complete within 5 minutes. In contrast, no OVA-coated particles were internalized at this time. After 30 minutes, 30% of bound silica was internalized and uptake continued slowly thereafter. OVA-coated latex beads, regardless of surface charge, were internalized at a similarly slow rate. These results demonstrate that macrophages internalize silica and that nonopsonized phagocytosis occurs by a temporally, and possibly mechanistically, distinct pathway from Fc receptor-mediated phagocytosis. Eighty percent of macrophages die within 12 hours of silica exposure. Neither OVA coating nor tetramethylrhodamine isothiocyanate labeling has any effect on cell death. Interestingly, antibody coating dramatically reduces silica toxicity. We hypothesize that the route of particle entry and subsequent phagosome trafficking affects the toxicity of internalized particles.

  20. The Phagocytosis of Crystalline Silica Particles by Macrophages

    PubMed Central

    Gilberti, Renée M.; Joshi, Gaurav N.; Knecht, David A.

    2008-01-01

    Silicosis is a chronic lung disease induced by the inhalation of crystalline silica. Exposure of cultured macrophages to crystalline silica leads to cell death; however, the mechanism of cell–particle interaction, the fate of particles, and the cause of death are unknown. Time-lapse imaging shows that mouse macrophages avidly bind particles that settle onto the cell surface and that cells also extend protrusions to capture distant particles. Using confocal optical sectioning, silica particles were shown to be present within the cytoplasmic volume of live cells. In addition, electron microscopy and elemental analysis showed silica in internal cellular sections. To further examine the phagocytosis process, the kinetics of particle uptake was quantified using an assay in which cells were exposed to ovalbumin (OVA)-coated particles, and an anti-OVA antibody was used to distinguish surface-bound from internalized particles. Fc receptor–mediated uptake of antibody-coated silica particles was nearly complete within 5 minutes. In contrast, no OVA-coated particles were internalized at this time. After 30 minutes, 30% of bound silica was internalized and uptake continued slowly thereafter. OVA-coated latex beads, regardless of surface charge, were internalized at a similarly slow rate. These results demonstrate that macrophages internalize silica and that nonopsonized phagocytosis occurs by a temporally, and possibly mechanistically, distinct pathway from Fc receptor–mediated phagocytosis. Eighty percent of macrophages die within 12 hours of silica exposure. Neither OVA coating nor tetramethylrhodamine isothiocyanate labeling has any effect on cell death. Interestingly, antibody coating dramatically reduces silica toxicity. We hypothesize that the route of particle entry and subsequent phagosome trafficking affects the toxicity of internalized particles. PMID:18556590

  1. Species-specific polyamines from diatoms control silica morphology

    NASA Astrophysics Data System (ADS)

    Kröger, Nils; Deutzmann, Rainer; Bergsdorf, Christian; Sumper, Manfred

    2000-12-01

    Biomineralizing organisms use organic molecules to generate species-specific mineral patterns. Here, we describe the chemical structure of long-chain polyamines (up to 20 repeated units), which represent the main organic constituent of diatom biosilica. These substances are the longest polyamine chains found in nature and induce rapid silica precipitation from a silicic acid solution. Each diatom is equipped with a species-specific set of polyamines and silica-precipitating proteins, which are termed silaffins. Different morphologies of precipitating silica can be generated by polyamines of different chain lengths as well as by a synergistic action of long-chain polyamines and silaffins.

  2. Polycationic peptides from diatom biosilica that direct silica nanosphere formation.

    PubMed

    Kröger, N; Deutzmann, R; Sumper, M

    1999-11-01

    Diatom cell walls are regarded as a paradigm for controlled production of nanostructured silica, but the mechanisms allowing biosilicification to proceed at ambient temperature at high rates have remained enigmatic. A set of polycationic peptides (called silaffins) isolated from diatom cell walls were shown to generate networks of silica nanospheres within seconds when added to a solution of silicic acid. Silaffins contain covalently modified lysine-lysine elements. The first lysine bears a polyamine consisting of 6 to 11 repeats of the N-methyl-propylamine unit. The second lysine was identified as epsilon-N,N-dimethyl-lysine. These modifications drastically influence the silica-precipitating activity of silaffins.

  3. Nanoindentation studies of nickel zinc ferrite embedded mesoporous silica template

    NASA Astrophysics Data System (ADS)

    Banerjee, S.; Hajra, P.; Mada, M. R.; Bandopadhyay, S.; Chakravorty, D.

    2013-02-01

    Nickel zinc ferrite (NZF) embedded mesoporous silica KIT-6 nanocomposite (NZFMS) was synthesized via impregnation method. The microstructure of the samples was characterized by transmission electron microscopy (TEM). Nanoindentation (NI) studies were carried out on both mesoporous silica (MS) and the nanocomposite NZFMS. It was found that the young's modulus (E) and hardness (H) of the NZFMS were higher than that of the MS. From creep measurement it was observed that the creep-strain rate was greater for NZFMS compared to MS. This arose due to diffusion of Fe3+ ions from nickel zinc ferrite to the silica glass. The results indicate that the NZFMS material shows superplastic behaviour at room temperature.

  4. Measurements of BET Surface Area on Silica Nanosprings

    SciTech Connect

    Karkamkar, Abhijeet J.

    2008-09-01

    Nitrogen adsorption desorption isotherm for Silica nanosprings (GoNano2) samples deposited on substrate. The isotherm was obtained at 77 K using liquid N2 bath. The area of the substrate is 16 cm2. The amount of the sample is 0.44 mg/cm2. Amount of silica nanosprings= 7.04 mg. There is no indication of substantial micro or mesoporosity in the sample based on the nature of the isotherm. Eleven point BET surface area was measured. Nine points plotted. Goodness if fit R= 0.9992. BET surface area for silica nanosprings= 262 cm2/g

  5. Effect of size of silica microspheres on photonic band gap

    SciTech Connect

    Dhiman, N. Sharma, A. Gathania, A. K.; Singh, B. P.

    2014-04-24

    In present work photonic crystals of different size of silica microspheres have been fabricated. The optical properties of these developed photonic crystals have been studied using UV-visible spectroscopy. UV-visible spectroscopy shows that they have photonic band gap that can be tuned in visible and infrared regime by changing the size of silica microspheres. The photonic band gap structures of these photonic crystals have been calculated using MIT photonic band gap package. It also reveals that with the increase in size of silica microspheres the photonic band gap shifts to lower energy region.

  6. Physical Separation of Straw Stem Components to Reduce Silica

    SciTech Connect

    Hess, John Richard; Thompson, David Neal; Hoskinson, Reed Louis; Shaw, Peter Gordon; Grant, D.R.

    2002-04-01

    In this paper, we describe ongoing efforts to solve challenges to using straw for bioenergy and bioproducts. Among these, silica in straw forms a low-melting eutectic with potassium, causing slag deposits, and chlorides cause corrosion beneath the deposits. Straw consists principally of stems, leaves, sheaths, nodes, awns, and chaff. Leaves and sheaths are higher in silica, while chaff, leaves and nodes are the primary source of fines. Our approach to reducing silica is to selectively harvest the straw stems using an in-field physical separation, leaving the remaining components in the field to build soil organic matter and contribute soil nutrients.

  7. Influence of grain boundary silica impurity on alumina toughness

    SciTech Connect

    Moya, J.S.; Kriven, W.M.; Pask, J.A.

    1980-08-01

    In a series of previous reports the effect of silica impurity on aggregation state and on electropheretic, pressing, filtering and sintering behavior on alumina powders was presented. The results obtained showed that the silica surface impurity plays an important role in the ceramic processing of powders by (a) decreasing the pH values of the isoelectric point (i.e.p.), which affects the aggregation state of the powder, and (b) decreasing the compactability and the activation energy for the initial stage of sintering. In the phase of the studies emphasis was given to the effect of the presence of silica impurity on the toughness and fracture behavior of alumina samples.

  8. Development of silica glass microstructured optical fibers technology in Poland

    NASA Astrophysics Data System (ADS)

    Wójcik, J.; Janoszczyk, B.; Poturaj, K.; Makara, M.; Walewski, A.; Mergo, P.; Klimek, J.; Skorupski, K.; Czyżewska, L.

    2007-04-01

    Paper presents the state of advance of the silica glass microstructured optical fibers technology n Poland especially in Department of Optical Fibers Technology Maria Curie Sklodowska University. Only in this Department there are the technological apparatus for advanced investigations on the technology of the silica glass optical fibers. In paper was describe the technology of optical fiber photonic structure manufacturing, high silica glass synthesis from vapor phase with MCVD and OVD methods. Next was describe some kinds of microstructured optical fibers witch technologies elaborated in UMCS in support of own and received from cooperated research teams optical fibers structures, modeling and measurements results.

  9. 42 CFR 84.1147 - Silica mist test for dust, fume, and mist respirators; minimum requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Silica mist test for dust, fume, and mist... Efficiency Respirators and Combination Gas Masks § 84.1147 Silica mist test for dust, fume, and mist... nor more than 25 milligrams of silica mist, weighed as silica dust, per cubic meter of air. (d)...

  10. 42 CFR 84.1147 - Silica mist test for dust, fume, and mist respirators; minimum requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Silica mist test for dust, fume, and mist... Efficiency Respirators and Combination Gas Masks § 84.1147 Silica mist test for dust, fume, and mist... nor more than 25 milligrams of silica mist, weighed as silica dust, per cubic meter of air. (d)...

  11. 42 CFR 84.1147 - Silica mist test for dust, fume, and mist respirators; minimum requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Silica mist test for dust, fume, and mist... Efficiency Respirators and Combination Gas Masks § 84.1147 Silica mist test for dust, fume, and mist... nor more than 25 milligrams of silica mist, weighed as silica dust, per cubic meter of air. (d)...

  12. 42 CFR 84.1147 - Silica mist test for dust, fume, and mist respirators; minimum requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Silica mist test for dust, fume, and mist... Efficiency Respirators and Combination Gas Masks § 84.1147 Silica mist test for dust, fume, and mist... nor more than 25 milligrams of silica mist, weighed as silica dust, per cubic meter of air. (d)...

  13. 42 CFR 84.1147 - Silica mist test for dust, fume, and mist respirators; minimum requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Silica mist test for dust, fume, and mist... Efficiency Respirators and Combination Gas Masks § 84.1147 Silica mist test for dust, fume, and mist... nor more than 25 milligrams of silica mist, weighed as silica dust, per cubic meter of air. (d)...

  14. Synthesis, characterisation and application of silica-magnetite nanocomposites

    NASA Astrophysics Data System (ADS)

    Bruce, Ian J.; Taylor, James; Todd, Michael; Davies, Martin J.; Borioni, Enrico; Sangregorio, Claudio; Sen, Tapas

    2004-12-01

    Silica-magnetite composites were prepared for eventual applications in biomolecular separations (nucleic acids). Their production on large scale has been optimised and they have been extensively characterised in a physical and chemical context. They perform at least as well, if not better than a commercially available equivalent at adsorbing and eluting DNA. Several methods for the preparation of magnetite were compared in order to select one, which produced particles, possessing high magnetic susceptibility, low rate of sedimentation and good chemical stability. Of the main methods studied: (i) oxidative hydrolysis of iron(II) sulphate in alkaline media, (ii) alkaline hydrolysis of iron(II) and iron(III) chloride solutions, and (iii) precipitation from iron(II) and iron(III) chloride solutions by hydrolysis of urea, method (i) produced the 'best' magnetite particles. Silica-magnetite composites were prepared using the 'best' magnetite, and, for comparison, two methods for depositing silica were used to coat the silica onto magnetite nanoparticles, from silicic acid at pH 10 and by acid hydrolysis of tetraethoxysilane (TEOS) at 90 °C. The best method for yielding silica-magnetite composites that worked well in DNA adsorption and elution proved to be that involving silicic acid and this material could be made in 20 g batch sizes. Silica-magnetite composites from the two methods proved to have distinct and different physical and chemical properties. All magnetite and silica-magnetite samples were fully characterised for their relative chemical composition using Fourier-transform infrared, XRF and thermo-gravimetric analysis. Their physical characteristics were determined using scanning electron microscopy and N2 adsorption and Mossbauer spectroscopy was used to confirm the identity of the iron oxides produced. Selected samples were comparatively tested for their ability to adsorb, and subsequently elute, 2-deoxyguanosine-5-monophosphate (GMP) and its non

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

    SciTech Connect

    Izvekov, Sergei Rice, Betsy M.

    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.

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

    NASA Astrophysics Data System (ADS)

    Izvekov, Sergei; Rice, Betsy M.

    2015-12-01

    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.

  17. Highly aspherical silica nanoshells by templating tubular liposomes

    PubMed Central

    Tan, Grace; Xu, Peng; He, Jibao; Lawson, Louise; McPherson, Gary L.

    2010-01-01

    A dual-lipid liposome system consisting of a phospholipid and a skin ceramide extruded though a 100 nm membrane yields novel tubular and helical liposomes. These liposomes were used as templates to generate highly aspherical silica nanocapsules with length to diameter aspect ratios exceeding 10. Many of these nanocapsules have the morphology of a bulbous end attached to a long tip, mimicking microneedles attached to a reservoir. The fidelity of helical liposomes is transcribed to the silicas and the long tips indicate helically entwined left-handed silica structures. The silica coating is expected to protect and stabilize the internal contents of the liposomes, as well as enable surface functionalization for applications in drug or targeted delivery. PMID:20352059

  18. Formation of hollow silica nanospheres by reverse microemulsion

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Han; Chang, Jen-Hsuan; Yeh, Yi-Qi; Wu, Si-Han; Liu, Yi-Hsin; Mou, Chung-Yuan

    2015-05-01

    Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and water in a continuous oil phase (alkanes) coalesce into size-tunable silica nanoparticles via diffusion aggregation after the introduction of silica precursors. Here, we elucidate in detail the growth mechanism for silica nanoparticles via nucleation of ammonium-catalyzed silica oligomers from tetraethylorthosilicate (TEOS) and nanoporous aminopropyltrimethoxy silane (APTS) in the reverse microemulsion system. The formation pathway was studied in situ with small-angle X-ray scattering (SAXS). We find a four-stage process showing a sigmoidal growth behavior in time with a crossover from the induction period, early nucleation stage, coalescence growth and a final slowing down of growth. Various characterizations (TEM, N2 isotherm, dynamic light scattering, zeta potential, NMR, elemental analysis) reveal the diameters, scattering length density (SLD), mesoporosity, surface potentials and chemical compositions of the HSNs. Oil phases of alkanes with different alkyl chains are systematically employed to tune the sizes of HSNs by varying oil molar volumes, co-solvent amounts or surfactant mixture ratios. Silica condensation is incomplete in the core region, with the silica source of TEOS and APTS leading to the hollow silica nanosphere after etching with warm water.Uniform hollow silica nanospheres (HSNs) synthesized with reverse microemulsion have great application potential as nanoreactors because enzymes or nanocatalysts can be easily encapsulated de novo in synthesis. Water-in-oil (w/o) reverse microemulsions comprising the polymeric surfactant polyoxyethylene (5) isooctylphenyl ether (Igepal CA-520), ammonia and

  19. Silica coated noble metal nanoparticle hydrosols as supported catalyst precursors.

    PubMed

    Kong, Tung Shing Adam; Yu, Kai Man Kerry; Tsang, Shik Chi

    2006-04-01

    Synthesis of well-defined nanoparticles has been intensively pursued not only for their fundamental scientific interest, but also for many technological applications. One important development of the nanomaterial is in the area of chemical catalysis. We have now developed a new aqueous-based method for the synthesis of silica encapsulated noble metal nanoparticles in controlled dimensions. Thus, colloid stable silica encapsulated approximately 5 nm platinum nanoparticle is synthesized by a multi-step method. The thickness of the silica coating could be controlled using a different amount of silica precursor. These particles supported on a high surface area alumina are also demonstrated to display a superior hydrogenation activity and stability against metal sintering after thermal activation.

  20. Mesostructured silica and aluminosilicate carriers for oxytetracycline delivery systems.

    PubMed

    Berger, D; Nastase, S; Mitran, R A; Petrescu, M; Vasile, E; Matei, C; Negreanu-Pirjol, T

    2016-08-30

    Oxytetracycline delivery systems containing various MCM-type silica and aluminosilicate with different antibiotic content were developed in order to establish the influence of the support structural and textural properties and aluminum content on the drug release profile. The antibiotic molecules were loaded into the support mesochannels by incipient wetness impregnation method using a drug concentrated aqueous solution. The carriers and drug-loaded materials were investigated by small- and wide-angle XRD, FTIR spectroscopy, TEM and N2 adsorption-desorption isotherms. Faster release kinetics of oxytetracycline from uncalcined silica and aluminosilicate supports was observed, whereas higher drug content led to lower delivery rate. The presence of aluminum into the silica network also slowed down the release rate. The antimicrobial assays performed on Staphylococcus aureus clinical isolates showed that the oxytetracycline-loaded materials containing MCM-41-type mesoporous silica or aluminosilicate carriers inhibited the bacterial development. PMID:26861688

  1. CO adsorption on a silica bilayer supported on Ru(0001)

    NASA Astrophysics Data System (ADS)

    Schlexer, Philomena; Pacchioni, Gianfranco; Włodarczyk, Radosław; Sauer, Joachim

    2016-06-01

    Silica bilayers are built up of two layers of corner sharing SiO4-tetrahedra and constitute an inert ultra-thin membrane supported on the Ru(0001) surface. We have investigated the adsorption of CO on that system using DFT with inclusion of dispersion corrections. The molecules adsorb at the interface between the SiO2 film and Ru(0001) surface. The estimated barrier for diffusion of CO through the silica bilayer is around 0.5 eV. The CO bond length, the C-O stretching frequency and the silica-ruthenium distance depend strongly on the CO coverage. The band observed at 2051 cm- 1 in previous experiments can be assigned to a CO coverage of around 0.5 ML on Ru(0001), with the silica bilayer floating above the CO molecules.

  2. Fabrication of keratin-silica hydrogel for biomedical applications.

    PubMed

    Kakkar, Prachi; Madhan, Balaraman

    2016-09-01

    In the recent past, keratin has been fabricated into different forms of biomaterials like scaffold, gel, sponge, film etc. In lieu of the myriad advantages of the hydrogels for biomedical applications, a keratin-silica hydrogel was fabricated using tetraethyl orthosilicate (TEOS). Textural analysis shed light on the physical properties of the fabricated hydrogel, inturn enabling the optimization of the hydrogel. The optimized keratin-silica hydrogel was found to exhibit instant springiness, optimum hardness, with ease of spreadability. Moreover, the hydrogel showed excellent swelling with highly porous microarchitecture. MTT assay and DAPI staining revealed that keratin-silica hydrogel was biocompatible with fibroblast cells. Collectively, these properties make the fabricated keratin-silica hydrogel, a suitable dressing material for biomedical applications.

  3. New insights into silica-based NMR “chromatography”

    NASA Astrophysics Data System (ADS)

    Pemberton, Chava; Hoffman, Roy; Aserin, Abraham; Garti, Nissim

    2011-02-01

    Silica is used as an important component for NMR “chromatography”. In this study the effect of the binding strength to silica of a variety of compounds on their diffusion rate is measured for the first time. Over two orders of magnitude of diffusion difference enhancement was obtained in the presence of silica for some compounds. An explanation of the enhancement is given that also allows one to predict the “chromatographic” behavior of new compounds or mixtures. The binding strength is divided into categories of weakly bound, singly bound and multiply bound. Carboxylates, sulfonates, and diols are found to be particularly strongly bound and to diffuse up to 2½ orders of magnitude more slowly in the presence of silica.

  4. Silica and titanium dioxide nanoparticles cause pregnancy complications in mice

    NASA Astrophysics Data System (ADS)

    Yamashita, Kohei; Yoshioka, Yasuo; Higashisaka, Kazuma; Mimura, Kazuya; Morishita, Yuki; Nozaki, Masatoshi; Yoshida, Tokuyuki; Ogura, Toshinobu; Nabeshi, Hiromi; Nagano, Kazuya; Abe, Yasuhiro; Kamada, Haruhiko; Monobe, Youko; Imazawa, Takayoshi; Aoshima, Hisae; Shishido, Kiyoshi; Kawai, Yuichi; Mayumi, Tadanori; Tsunoda, Shin-Ichi; Itoh, Norio; Yoshikawa, Tomoaki; Yanagihara, Itaru; Saito, Shigeru; Tsutsumi, Yasuo

    2011-05-01

    The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.

  5. In situ synthesis of polysulfides covalently bonded to silica.

    PubMed

    Ossenkamp, Gabriel C; Kemmitt, Tim; Johnston, Jim H

    2002-05-15

    Silanol groups, triple bond SiOH, on the surface of silica were esterified with unsaturated alcohols and long-chain alcohols bearing thiol groups. The modified silicas obtained were used as substrates for a vulcanization-analogous reaction with sulfur catalyzed by zinc dimethyldithiocarbamate. Surface-esterified thiols could be smoothly converted to bridged polysulfides bonded to the silica surface, whereas the use of surface-esterified unsaturated alcohols led to removal of the surface-esterified alcohol from the silica surface. The materials were characterized by solid-state NMR and thermal and microanalytical analysis. The linking of surface-esterified alkenols and thiols by sulfide bridges was investigated by a numerical model for a flat surface. This showed that for a typical density of 3-4 micromol/m(2) surface groups, a statistical maximum of 70-75% of groups could be linked by S(n) bridges (n=2-4). PMID:16290622

  6. Quantification of residual stress from photonic signatures of fused silica

    NASA Astrophysics Data System (ADS)

    Cramer, K. Elliott; Hayward, Maurice; Yost, William T.

    2014-02-01

    A commercially available grey-field polariscope (GFP) instrument for photoelastic examination is used to assess impact damage inflicted upon the outer-most pane of Space Shuttle windows made from fused silica. A method and apparatus for calibration of the stress-optic coefficient using four-point bending is discussed. The results are validated on known material (acrylic) and are found to agree with literature values to within 6%. The calibration procedure is then applied to fused-silica specimens and the stress-optic coefficient is determined to be 2.43 ± 0.54 × 10-12 Pa-1. Fused silica specimens containing impacts artificially made at NASA's Hypervelocity Impact Technology Facility (HIT-F), to simulate damage typical during space flight, are examined. The damage sites are cored from fused silica window carcasses and examined with the GFP. The calibrated GFP measurements of residual stress patterns surrounding the damage sites are presented.

  7. Mineralogy of Silica Polymorphs in Basaltic Clasts in Eucrites

    NASA Astrophysics Data System (ADS)

    Ono, H.; Takenouchi, A.; Mikouchi, T.

    2016-08-01

    We analyzed silica polymorphs in basaltic clasts in Y-75011, Pasamonte and Stannern eucrites. Cristobalite and quartz have been found, which suggests wide occurrence of hydrothermal activity throughout the crust of Vesta.

  8. HILIC separation mechanisms of tetracyclines on amino bonded silica column

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Effects of mobile phase variations on the chromatographic separation on amino bonded silica column in hydrophilic interaction chromatography (HILIC) were investigated for four zwitterionic tetracyclines (TCs): oxytetracycline, doxycycline, chlortetracycline and tetracycline. A mixed-mode retention m...

  9. Incorporation of terbium(III) ion into mesoporous silica particles

    NASA Astrophysics Data System (ADS)

    Kataoka, Takuya; Wang, Liyin; Kobayashi, Kouhei; Nishikawa, Masami; Tagaya, Motohiro

    2016-10-01

    Terbium(III)-doped mesoporous silicas were synthesized, and the states of terbium ions in the silica frameworks were investigated. The mesopores were preserved upon doping at terbium ion molar concentrations relative to (Si+Tb) up to 15 mol %, indicating the interaction of terbium ions with Si-O bonds. Significant morphological changes of the particles were observed with increasing the doping concentration. The shapes of the photoluminescence spectra due to the transitions of 5D4 → 7F6 and 5D4 → 7F5 were indicative of the presence of terbium ions in the silica matrix, and the quantum efficiency (2.1-2.8%) and lifetime (1.6-1.9 ms) decreased with increasing the doping concentration up to 15 mol %. Therefore, the terbium ions are considered to be located inside the amorphous silica frameworks, where they electrostatically interact with the O atoms of silanol and siloxane groups.

  10. Removal of silica from Raft River geothermal water

    SciTech Connect

    Suciu, D.F.; Miller, R.L.

    1980-06-01

    Lack of sufficient quantities of clean surface or near-surface water at Raft River for cooling purposes dictates that cooled geothermal fluid, effluent from the Raft River 5 MW(e) Pilot Power Plant, must also be used as condenser coolant. Prior testing revealed that a water-treatment system would be required to reduce silica and calcium concentrations of the cooling fluid. The water-treatment system specified was to use dolomitic lime for both pH adjustment and source of magnesium. The dolomitic lime treatment was investigated and found to be inadequate. Subsequent testing was done to find chemical systems that would adequately reduce silica concentrations. Three magnesium and two iron compounds were found which reduced silica to acceptable concentration levels. They are magnesium bicarbonate, magnesium chloride, magnesium sulfate, iron sulfate, and iron chloride. Magnesium oxide, using a two-stage countercurrent process, will also reduce silica to adequate levels.

  11. Patterned silica films using microphase separation of a block copolymer

    NASA Astrophysics Data System (ADS)

    Kataoka, Sho; Takeuchi, Yasutaka; Endo, Akira

    2014-11-01

    Block copolymers exhibit various nanoscale ordered morphologies induced by microphase separation. Here, we present a method for providing two types of patterned silica films on Si wafer substrates simply by shifting the phase equilibrium of a block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-P4VP). In this method, siloxane is adsorbed onto poly(4-vinylpyridine) blocks of PS-P4VP whose structure varies with solvent polarity and is calcined to remove the block copolymer. Siloxane is in a dispersed phase with toluene as a solvent resulting in silica nanoparticle arrays, while siloxane is in a continuous phase with N, N-dimethylformamide (DMF) resulting in silica films with ordered mesopores. Since the pore size of silica films prepared in DMF is approximately 20 nm, the film has the ability to serve as a support for enzymes such as laccase.

  12. Mesostructured silica and aluminosilicate carriers for oxytetracycline delivery systems.

    PubMed

    Berger, D; Nastase, S; Mitran, R A; Petrescu, M; Vasile, E; Matei, C; Negreanu-Pirjol, T

    2016-08-30

    Oxytetracycline delivery systems containing various MCM-type silica and aluminosilicate with different antibiotic content were developed in order to establish the influence of the support structural and textural properties and aluminum content on the drug release profile. The antibiotic molecules were loaded into the support mesochannels by incipient wetness impregnation method using a drug concentrated aqueous solution. The carriers and drug-loaded materials were investigated by small- and wide-angle XRD, FTIR spectroscopy, TEM and N2 adsorption-desorption isotherms. Faster release kinetics of oxytetracycline from uncalcined silica and aluminosilicate supports was observed, whereas higher drug content led to lower delivery rate. The presence of aluminum into the silica network also slowed down the release rate. The antimicrobial assays performed on Staphylococcus aureus clinical isolates showed that the oxytetracycline-loaded materials containing MCM-41-type mesoporous silica or aluminosilicate carriers inhibited the bacterial development.

  13. Energy saving tire with silica-rich tread

    SciTech Connect

    Ahmad, S.; Schaefer, R. J.

    1985-05-28

    A pneumatic radial tire is provided with a tread having from 1 part by weight of hydrated amorphous fine-particle silica per 3 parts of carbon black tread reinforcing filler, to about 3 parts by weight of the silica to 1 part of the carbon black. The amount of silica present is preferably in the range from about 18 parts to about 50 parts by weight per 100 parts of natural or synthetic rubber. When such a tread is compounded with a mercaptosilane in which the mercapto group is reversibly blocked, the tread provides reduced rolling resistance without loss of traction. Such reduction in rolling resistance without loss of traction is not observed when the silica is not coupled with the mercaptosilane coupling agent.

  14. Apatite nucleation on silica surface: a zeta potential approach.

    PubMed

    Coreño, J; Martínez, A; Bolarín, A; Sánchez, F

    2001-10-01

    Zeta potential measurements on pure silica, prepared by the sol-gel method from tetraethoxysilane under acidic conditions, are reported in different suspensions. Water suspensions and suspensions containing calcium or phosphate ions with and without NaCl were tested. zeta potential measurements were carried out as a function of the pH and ion concentration. Also, calcium and phosphate adsorption on silica was determined experimentally. The results of zeta potential and adsorption measurements suggest that both calcium and phosphate ions can be adsorbed on the silica surface; however, calcium adsorption is stronger than phosphate adsorption. When calcium and sodium ions are present in the suspension, calcium adsorption decreases. It seems that certain sites on the silica surface are specific for calcium adsorption.

  15. Development of Filler Structure in Colloidal Silica-Polymer Nanocomposites

    SciTech Connect

    Meth, Jeffrey S; Zane, Stephen G; Chi, Changzai; Londono, J David; Wood, Barbara A; Cotts, Patricia; Keating, Mimi; Guise, William; Weigand, Steven

    2012-02-07

    The realization of the full potential for polymeric nanocomposites to manifest their entitled property improvements relies, for some properties, on the ability to achieve maximum particle-matrix interfacial area. Well-dispersed nanocomposites incorporating colloidal silica as the filler can be realized in both polystyrene and poly(methyl methacrylate) matrices by exploiting the charge stabilized nature of silica in nonaqueous solvents which act as Bronsted bases. We demonstrate that dispersions of colloidal silica in dimethylformamide are charge stabilized, regardless of organosilyl surface functionalization. When formulated with polymer solutions, the charge stabilized structure is maintained during drying until the charged double layer collapses. Although particles are free to diffuse and cluster after this neutralization, increased matrix viscosity retards the kinetics. We demonstrate how high molecular weight polymers assist in immobilizing the structure of the silica to produce well-dispersed composites. The glass transition temperatures of these composites do not vary, even at loadings up to 50 vol %.

  16. Polishing-paste-induced silica granuloma of the gingiva.

    PubMed

    Lombardi, T; Kuffer, R; Dubrez, B

    2001-01-01

    Polishing-paste-induced silica granuloma of the gingiva, an uncommon condition, may mimic various local or systemic pathological entities. A 33-year-old woman and a 42-year-old man were referred for a localised refractory gingival inflammation. Clinical diagnoses included allergy, lichen planus and herpes. Biopsy showed well-demarcated non-caseating granulomas, associating epithelioid and Langhans giant cells. Special bacterial and mycological stains were negative. Systemic examination and laboratory tests ruled out sarcoidosis and Crohn's disease. Polarised light revealed birefringent crystalline foreign material. A diagnosis of silica granuloma was made. Both patients had frequent dental hygiene treatment including polishing with abrasive paste, suggesting an iatrogenic implantation of the foreign bodies. Gingival damage can result from the use of some dental materials containing silica. Often asymptomatic, sometimes producing visible lesions, granulomatous gingivitis may mislead into wrong diagnosis and treatment. Old silica granulomas may become symptomatic if the patient contracts sarcoidosis.

  17. Method of synthesizing silica nanofibers using sound waves

    SciTech Connect

    Sharma, Jaswinder K.; Datskos, Panos G.

    2015-09-15

    A method for synthesizing silica nanofibers using sound waves is provided. The method includes providing a solution of polyvinyl pyrrolidone, adding sodium citrate and ammonium hydroxide to form a first mixture, adding a silica-based compound to the solution to form a second mixture, and sonicating the second mixture to synthesize a plurality of silica nanofibers having an average cross-sectional diameter of less than 70 nm and having a length on the order of at least several hundred microns. The method can be performed without heating or electrospinning, and instead includes less energy intensive strategies that can be scaled up to an industrial scale. The resulting nanofibers can achieve a decreased mean diameter over conventional fibers. The decreased diameter generally increases the tensile strength of the silica nanofibers, as defects and contaminations decrease with the decreasing diameter.

  18. Stable and responsive fluorescent carbon nanotube silica gels

    SciTech Connect

    Dattelbaum, Andrew M; Gupta, Gautam; Doorn, Stephen K; Duque, Juan G

    2010-05-03

    Here we report a general route to prepare silica nanocomposite gels doped with fluorescent single walled carbon nanotubes (SWNT). We show that tetramethylorthosilicate (TMOS) vapors can be used to gel an aqueous suspension of surfactant-wrapped SWNT while maintaining fluorescence from the semiconducting nanotubes. The vapor phase silica process is performed at room temperature and is simple, reproducible, relatively quick, and requires no dilution of SWNT dispersions. However, exposure of aqueous SWNT suspensions to TMOS vapors resulted in an acidification of the suspension prior to gelation that caused a decrease in the emission signal from sodium dodecylsulfate (SDS) wrapped SWNT. We also show that although the SWNT are encapsulated in silica the emission signal from the encapsulated SWNT may be attenuated by exposing the nanocomposites to small aromatic molecules known to mitigate SWNT emission. These results demonstrate a new route for the preparation of highly luminescent SWNT/silica composite materials that are potentially useful for future sensing applications.

  19. Chronic obstructive pulmonary disease and occupational exposure to silica.

    PubMed

    Rushton, Lesley

    2007-01-01

    Prolonged exposure to high levels of silica has long been known to cause silicosis This paper evaluates the evidence for an increased risk of chronic obstructive pulmonary disease (COPD) in occupations and industries in which exposure to crystalline silica is the primary exposure, with a focus on the magnitude of risks and levels of exposure causing disabling health effects. The literature suggests consistently elevated risks of developing COPD associated with silica exposure in several occupations, including the construction industry; tunneling; cement industry; brick manufacturing; pottery and ceramic work; silica sand, granite and diatomaceous earth industries; gold mining; and iron and steel founding, with risk estimates being high in some, even after taking into account the effect of confounders like smoking. Average dust levels vary from about 0.5 mg.m3 to over 10 mg.m3 and average silica levels from 0.04 to over 5 mg.m3, often well above occupational standards. Factors influencing the variation from industry to industry in risks associated with exposure to silica-containing dusts include (a) the presence of other minerals in the dust, particularly when associated with clay minerals; (b) the size of the particles and percentage of quartz; (c) the physicochemical characteristics, such as whether the dust is freshly fractured. Longitudinal studies suggest that loss of lung function occurs with exposure to silica dust at concentrations of between 0.1 and 0.2 mg.m3, and that the effect of cumulative silica dust exposure on airflow obstruction is independent of silicosis. Nevertheless, a disabling loss of lung function in the absence of silicosis would not occur until between 30 and 40 years exposure.

  20. AEM and HREM evaluation of carbon nanostructures in silica aerogels

    SciTech Connect

    Song, X.Y.; Cao, W.; Hunt, A.J.

    1994-04-01

    Nanostructured carbon has been deposited in silica aerogels by chemical vapor infiltration using acetylene or ferrocene at moderate temperatures. Using analytical electron microscopy and high-resolution electron microscopy, we have observed various carbon rings and nanotubes in the silica aerogel-based carbon composite. Both X-ray microanalysis and nano-probe diffraction techniques have been used to confirm the presence of those carbon nanostructures. Morphologies and structural properties of the carbon nanotubes and rings have also been examined in detail.