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Sample records for iarc reevaluates silica

  1. Fiber glass exposure and human respiratory system cancer risk: lack of evidence persists since 2001 IARC re-evaluation.

    PubMed

    Marsh, Gary M; Buchanich, Jeanine M; Youk, Ada O

    2011-06-01

    To determine whether IARC's 2001 decision to downgrade the classification of insulation glass wool from Group 2B to Group 3 remains valid in light of epidemiological evidence reported after 2001. We performed a systematic review of epidemiological evidence regarding respiratory cancer risks in relation to man-made vitreous fiber (MMVF) exposure before and after the 2001 IARC re-evaluation with focus on glass wool exposure and respiratory system cancer. Since 2001, three new community-based, case-control studies, two detailed analyses of existing cohort studies and two reviews/meta-analyses were published. These studies revealed no consistent evidence of an increased respiratory system cancer risk in relation to glass wool exposure. From our evaluation of the epidemiological evidence published since 2001, we conclude that IARC's 2001 decision to downgrade insulation glass wool from Group 2B to Group 3 remains valid. Copyright © 2011 Elsevier Inc. All rights reserved.

  2. Man-made mineral (vitreous) fibres: evaluations of cancer hazards by the IARC Monographs Programme.

    PubMed

    Baan, Robert A; Grosse, Yann

    2004-09-03

    Man-made vitreous (glass-like) fibres are non-crystalline, fibrous inorganic substances (silicates) made primarily from rock, slag, glass or other processed minerals. These materials, also called man-made mineral fibres, include glass fibres (used in glass wool and continuous glass filament), rock or stone wool, slag wool and refractory ceramic fibres. They are widely used for thermal and acoustical insulation and to a lesser extent for other purposes. These products are potentially hazardous to human health because they release airborne respirable fibres during their production, use and removal. Man-made mineral fibres and man-made vitreous fibres have been the subject of reviews by IARC Monographs Working Groups in 1987 and 2001, respectively, which resulted in evaluations of the carcinogenic hazard to humans from exposure to these materials. These reviews and evaluations have been published as Volumes 43 and 81 of the IARC Monographs series [IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, vol. 43, Man-made Mineral Fibres and Radon (1988); IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, vol. 81, Man-made Vitreous Fibres (2002)]. The re-evaluation in 2001 was undertaken because there have been substantial improvements in the quality of the epidemiological information available on the carcinogenicity to humans of glass fibres, continuous glass filament and rock/slag wool. The new evaluations have addressed the limitations of earlier cohort studies, particularly concerning the lack of adjustment with respect to concomitant risk factors such as smoking and other sources of occupational exposure. In addition, the evaluation of the evidence for carcinogenicity of glass fibres to experimental animals has been refined, by making a distinction between insulation glass wool and special-purpose glass fibres. The results of the evaluations in 1987 and 2001 are thus different in several aspects. In this paper, the reviews and evaluations

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

    PubMed

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

    2000-04-01

    As a follow-up to an earlier study on IARC Group I compounds, further efforts have been made to evaluate the international literature on cigarette mainstream smoke for reports on constituents classified as IARC "Group 2A: probably carcinogenic to humans" and IARC "Group 2B: possibly carcinogenic to humans." IARC classifies 59 agents, mixtures and exposures as Group 2A. Of the overall list of 59, 50 represent chemical entities or complex mixtures ( [IARC,] ). When only chemical entities which have their origin from cigarette components (tobacco and paper) are considered, further searching of the international literature has revealed that nine chemical compounds of the 50 Group 2A listings have been reported in cigarette mainstream smoke ( Table 1 ). In micrograms/cigarette (mug/cig), the ranges reported for each of the nine compounds are as follows: formaldehyde (3.4-283); benzo[a]pyrene (B[a]P) (0.004-0. 108); dibenz[a,h]anthracene (DB[a,h]A) (0.004-0.076); N-nitrosodiethylamine (DEN) (non-detectable-0.0076); benz[a]anthracene (B[a]A) (trace-0.08); N-nitrosodimethylamine (DMN) (non-detectable-0.7-1.62); acrylamide (1.1-2.34); 1,3-butadiene (16-77); and 2-amino-3-methyl-3H-imidazo[4,5-f]quinoline (IQ) (0. 00026-0.00049).

  4. 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...

  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 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.

  7. Use of High Throughput Screening Data in IARC Monograph ...

    EPA Pesticide Factsheets

    Purpose: Evaluation of carcinogenic mechanisms serves a critical role in IARC monograph evaluations, and can lead to “upgrade” or “downgrade” of the carcinogenicity conclusions based on human and animal evidence alone. Three recent IARC monograph Working Groups (110, 112, and 113) pioneered analysis of high throughput in vitro screening data from the U.S. Environmental Protection Agency’s ToxCast program in evaluations of carcinogenic mechanisms. Methods: For monograph 110, ToxCast assay data across multiple nuclear receptors were used to test the hypothesis that PFOA acts exclusively through the PPAR family of receptors, with activity profiles compared to several prototypical nuclear receptor-activating compounds. For monographs 112 and 113, ToxCast assays were systematically evaluated and used as an additional data stream in the overall evaluation of the mechanistic evidence. Specifically, ToxCast assays were mapped to 10 “key characteristics of carcinogens” recently identified by an IARC expert group, and chemicals’ bioactivity profiles were evaluated both in absolute terms (number of relevant assays positive for bioactivity) and relative terms (ranking with respect to other compounds evaluated by IARC, using the ToxPi methodology). Results: PFOA activates multiple nuclear receptors in addition to the PPAR family in the ToxCast assays. ToxCast assays offered substantial coverage for 5 of the 10 “key characteristics,” with the greates

  8. 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

  9. The IARC monographs program: changing attitudes towards public health.

    PubMed

    Tomatis, Lorenzo

    2002-01-01

    From its outset, the International Agency for Research on Cancer's (IARC's) program for the evaluation of carcinogenic risks for humans had to resist strong direct and indirect pressures from various sources to protect its independence. External experts for Monographs working groups were selected on the basis of competence and the absence of conflicts of interest. The IARC did not use unpublished or confidential data, so readers could access the original information and thus follow the groups' reasoning. The strength of the original program lay in its scientific integrity and its transparency. Since 1994, however, the IARC appears to have attributed less importance to public health-oriented research and primary prevention, and the Monographs program seems to have lost some of its independence. Criteria for evaluating carcinogenicity related to mechanism(s) of action are not necessarily used as originally intended, to ensure better protection of public health. Evidence for carcinogenicity provided by the results of experimental bioassays has been disregarded on the basis of only suggested mechanistic hypotheses. If tests show those hypotheses to be incorrect, or if they do not account adequately for the wide range of susceptibility in humans, serious consequences for public health may follow.

  10. Mycotoxins as human carcinogens-the IARC Monographs classification.

    PubMed

    Ostry, Vladimir; Malir, Frantisek; Toman, Jakub; Grosse, Yann

    2017-02-01

    Humans are constantly exposed to mycotoxins (e.g. aflatoxins, ochratoxins), mainly via food intake of plant and animal origin. The health risks stemming from mycotoxins may result from their toxicity, in particular their carcinogenicity. In order to prevent these risks, the International Agency for Research on Cancer (IARC) in Lyon (France)-through its IARC Monographs programme-has performed the carcinogenic hazard assessment of some mycotoxins in humans, on the basis of epidemiological data, studies of cancer in experimental animals and mechanistic studies. The present article summarizes the carcinogenic hazard assessments of those mycotoxins, especially aflatoxins (aflatoxin B1, B2, G1, G2 and M1), fumonisins (fumonisin B1 and B2) and ochratoxin A (OTA). New information regarding the genotoxicity of OTA (formation of OTA-DNA adducts), the role of OTA in oxidative stress and the identification of epigenetic factors involved in OTA carcinogenesis-should they indeed provide strong evidence that OTA carcinogenicity is mediated by a mechanism that also operates in humans-could lead to the reclassification of OTA.

  11. [Motivation and significance of IARC classification for mobile phone].

    PubMed

    L'Abbate, N

    2011-01-01

    In May 2011, the IARC Working Group discussed the possibility that exposure to RF-EMF (radiofrequency electromagnetic fields) have to produce an increased risk for brain tumors and evaluated the available literature on different categories of subjects exposed, including, among others, a Danish cohort study, five case-control studies and the largest multi-center case-control study (INTERPHONE) on the use of mobile phone and brain tumors, including glioma, meningioma and acoustic neuroma. The Working Group also examined a number of studies with objectives related to various mechanisms ofcarcerogenesis. The findings have been reviewed critically and generally assessed as "limited" among users of wireless phones for glioma and acoustic neuroma and "inappropriate" to draw conclusions for other types of tumors. The evidence from occupational and environmental exposures were considered "insufficient" in the same way. Given the limited evidence in humans and in experimental animals, the Working Group has classified a large majority the RF-EMF fields as "possibly carcinogenic to humans" (Group 2B). The Director of IARC has recommended, however,further research in the long-term use of mobile phones and adoption of pragmatic steps to reduce exposure, such as hands-free devices or sms.

  12. Use of High Throughput Screening Data in IARC Monograph Evaluations (SOT)

    EPA Science Inventory

    Purpose: Evaluation of carcinogenic mechanisms serves a critical role in IARC monograph evaluations, and can lead to “upgrade” or “downgrade” of the carcinogenicity conclusions based on human and animal evidence alone. Three recent IARC monograph Working Groups (110, 112, and 11...

  13. 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.

  14. Research Recommendations for Selected IARC-Classified Agents

    PubMed Central

    Ward, Elizabeth M.; Schulte, Paul A.; Straif, Kurt; Hopf, Nancy B.; Caldwell, Jane C.; Carreón, Tania; DeMarini, David M.; Fowler, Bruce A.; Goldstein, Bernard D.; Hemminki, Kari; Hines, Cynthia J.; Pursiainen, Kirsti Husgafvel; Kuempel, Eileen; Lewtas, Joellen; Lunn, Ruth M.; Lynge, Elsebeth; McElvenny, Damien M.; Muhle, Hartwig; Nakajima, Tamie; Robertson, Larry W.; Rothman, Nathaniel; Ruder, Avima M.; Schubauer-Berigan, Mary K.; Siemiatycki, Jack; Silverman, Debra; Smith, Martyn T.; Sorahan, Tom; Steenland, Kyle; Stevens, Richard G.; Vineis, Paolo; Zahm, Shelia Hoar; Zeise, Lauren; Cogliano, Vincent J.

    2010-01-01

    Objectives There are some common occupational agents and exposure circumstances for which evidence of carcinogenicity is substantial but not yet conclusive for humans. Our objectives were to identify research gaps and needs for 20 agents prioritized for review based on evidence of widespread human exposures and potential carcinogenicity in animals or humans. Data sources For each chemical agent (or category of agents), a systematic review was conducted of new data published since the most recent pertinent International Agency for Research on Cancer (IARC) Monograph meeting on that agent. Data extraction Reviewers were charged with identifying data gaps and general and specific approaches to address them, focusing on research that would be important in resolving classification uncertainties. An expert meeting brought reviewers together to discuss each agent and the identified data gaps and approaches. Data synthesis Several overarching issues were identified that pertained to multiple agents; these included the importance of recognizing that carcinogenic agents can act through multiple toxicity pathways and mechanisms, including epigenetic mechanisms, oxidative stress, and immuno- and hormonal modulation. Conclusions Studies in occupational populations provide important opportunities to understand the mechanisms through which exogenous agents cause cancer and intervene to prevent human exposure and/or prevent or detect cancer among those already exposed. Scientific developments are likely to increase the challenges and complexities of carcinogen testing and evaluation in the future, and epidemiologic studies will be particularly critical to inform carcinogen classification and risk assessment processes. PMID:20562050

  15. Carcinogenicity of the insulation wools: reassessment of the IARC evaluation.

    PubMed

    Brown, R C; Davis, J M; Douglas, D; Gruber, U F; Hoskins, J A; Ilgren, E B; Johnson, N F; Rossiter, C E; Wagner, J C

    1991-08-01

    In assessing the health evidence concerning man-made mineral fibers, the chemical composition, surface activity, durability, and size of fibers have to be taken into account. Special-purpose fine glass fibers need to be separated from the insulation wools (glass, rock, and slag wool). The epidemiological evidence is sufficient to conclude that there has been no mesothelioma risk to workers producing or using glass wool, rock wool, or slag wool. The epidemiological studies have been large and powerful, and they show no evidence of a cause-effect relationship between lung cancer and exposure to glass wool, rock wool, or slag wool fibers. There is some evidence of a small cancer hazard attached to the manufacturing process in slag wool plants 20 to 50 years ago, when asbestos was used in some products and other carcinogenic substances were present. However, this hazard is not associated with any index of exposure to slag wool itself. Animal inhalation studies of ordinary insulation wools also show that there is no evidence of hazard associated with exposure to these relatively coarse, soluble fibers. The evidence of carcinogenicity is limited to experiments with special-purpose fine durable glass fibers or experimental fibers, and only when these fibers are injected directly into the pleural or peritoneal cavity. Multiple chronic inhalation studies of these same special-purpose fine glass fibers have not produced evidence of carcinogenicity. It is suggested that the present IARC evaluation of the carcinogenic risk of insulation wools should be revised to Category 3: not classifiable as to carcinogenicity to humans.

  16. IARC carcinogens reported in cigarette mainstream smoke and their calculated log P values.

    PubMed

    Smith, C J; Perfetti, T A; Garg, R; Hansch, C

    2003-06-01

    Cigarette smoke is a complex aerosol of minute liquid droplets (termed the particulate phase) suspended within a mixture of gases (CO(2), CO, NO(x), etc.) and semi-volatile compounds. The International Agency for Research on Cancer (IARC) has classified a number of the chemical constituents reported in cigarette mainstream smoke (MS) as carcinogens. Previously, we published a series of historical reviews reporting that 11 IARC Group 1 (known human), nine Group 2A (probable human) and 48 Group 2B (possible human) carcinogens have been observed in MS. Here, we expand the list of IARC classified carcinogens from 68 to 81 compounds (11 Group 1, 14 Group 2A and 56 Group 2B) reported in MS. A number of the IARC compounds reported in MS are found in the vapor phase including three Group 1, eight Group 2A and 18 Group 2B constituents. Several IARC MS compounds are found in both the vapor and particulate phases including two in Group 1, one in Group 2A and one in Group 2B. Forty-eight IARC MS carcinogens are found in the particulate phase only. Lipophilicity, as determined by the base 10 logarithm of the calculated octanol-water partition coefficient and denoted as Clog P, is reported for each of the 71 non-metallic MS IARC carcinogens. Clog P correlates with a number of biological activities including in vitro mutagenicity and carcinogenicity in rodents, and in the absence of any additional toxicological or epidemiological data, a high log P compound is more likely to be carcinogenic than a low log P compound.

  17. 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... the child's parent or teacher requests a reevaluation. (b) Limitation. A reevaluation conducted...

  18. Classification of man-made vitreous fibers: Comments on the revaluation by an IARC working group.

    PubMed

    Wardenbach, P; Rödelsperger, K; Roller, M; Muhle, H

    2005-11-01

    In 2001, an IARC working group revaluated the carcinogenic risks of man-made vitreous fibers (MMVF). Compared with the IARC evaluation in 1987, the overall evaluations of insulation glass wool, rock (stone) wool, and slag wool were changed from Group 2B to Group 3. These changes ensued from an alteration in the evidence for cancer in humans and in experimental animals: Instead of "sufficient," the evidence for cancer in experimental animals is now looked upon as "limited" if there is a carcinogenic response after intraperitoneal injection but not after recently conducted inhalation experiments. For these studies, it is argued that they did properly address the technological limitations of earlier inhalation experiments. For Maxim and McConnell [Maxim L.D., McConnell E.E., 2001. Interspecies comparisons of the toxicity of asbestos and synthetic vitreous fibers: a weight-of-the-evidence approach. Regul. Toxicol. Pharmacol. 33, 319-342], well-conducted inhalation studies are very sensitive and rats may be more sensitive than humans in detecting the carcinogenic potential of MMVF. However, their arguments are highly questionable. The explanations of the IARC working group for preferring the newer inhalation studies are not sufficiently supported by the published data. Having in mind the higher sensitivity of humans compared to rats after inhalation of asbestos, more emphasis should have been given to the carcinogenic response after intraperitoneal injection.

  19. Prioritizing Chemicals for Risk Assessment Using Chemoinformatics: Examples from the IARC Monographs on Pesticides

    PubMed Central

    Guha, Neela; Guyton, Kathryn Z.; Loomis, Dana; Barupal, Dinesh Kumar

    2016-01-01

    Background: Identifying cancer hazards is the first step towards cancer prevention. The International Agency for Research on Cancer (IARC) Monographs Programme, which has evaluated nearly 1,000 agents for their carcinogenic potential since 1971, typically selects agents for hazard identification on the basis of public nominations, expert advice, published data on carcinogenicity, and public health importance. Objectives: Here, we present a novel and complementary strategy for identifying agents for hazard evaluation using chemoinformatics, database integration, and automated text mining. Discussion: To inform selection among a broad range of pesticides nominated for evaluation, we identified and screened nearly 6,000 relevant chemical structures, after which we systematically compiled information on 980 pesticides, creating network maps that allowed cluster visualization by chemical similarity, pesticide class, and publicly available information concerning cancer epidemiology, cancer bioassays, and carcinogenic mechanisms. For the IARC Monograph meetings that took place in March and June 2015, this approach supported high-priority evaluation of glyphosate, malathion, parathion, tetrachlorvinphos, diazinon, p,p′-dichlorodiphenyltrichloroethane (DDT), lindane, and 2,4-dichlorophenoxyacetic acid (2,4-D). Conclusions: This systematic approach, accounting for chemical similarity and overlaying multiple data sources, can be used by risk assessors as well as by researchers to systematize, inform, and increase efficiency in selecting and prioritizing agents for hazard identification, risk assessment, regulation, or further investigation. This approach could be extended to an array of outcomes and agents, including occupational carcinogens, drugs, and foods. Citation: Guha N, Guyton KZ, Loomis D, Barupal DK. 2016. Prioritizing chemicals for risk assessment using chemoinformatics: examples from the IARC Monographs on Pesticides. Environ Health Perspect 124:1823–1829;

  20. Prioritizing Chemicals for Risk Assessment Using Chemoinformatics: Examples from the IARC Monographs on Pesticides.

    PubMed

    Guha, Neela; Guyton, Kathryn Z; Loomis, Dana; Barupal, Dinesh Kumar

    2016-12-01

    Identifying cancer hazards is the first step towards cancer prevention. The International Agency for Research on Cancer (IARC) Monographs Programme, which has evaluated nearly 1,000 agents for their carcinogenic potential since 1971, typically selects agents for hazard identification on the basis of public nominations, expert advice, published data on carcinogenicity, and public health importance. Here, we present a novel and complementary strategy for identifying agents for hazard evaluation using chemoinformatics, database integration, and automated text mining. To inform selection among a broad range of pesticides nominated for evaluation, we identified and screened nearly 6,000 relevant chemical structures, after which we systematically compiled information on 980 pesticides, creating network maps that allowed cluster visualization by chemical similarity, pesticide class, and publicly available information concerning cancer epidemiology, cancer bioassays, and carcinogenic mechanisms. For the IARC Monograph meetings that took place in March and June 2015, this approach supported high-priority evaluation of glyphosate, malathion, parathion, tetrachlorvinphos, diazinon, p,p'-dichlorodiphenyltrichloroethane (DDT), lindane, and 2,4-dichlorophenoxyacetic acid (2,4-D). This systematic approach, accounting for chemical similarity and overlaying multiple data sources, can be used by risk assessors as well as by researchers to systematize, inform, and increase efficiency in selecting and prioritizing agents for hazard identification, risk assessment, regulation, or further investigation. This approach could be extended to an array of outcomes and agents, including occupational carcinogens, drugs, and foods. Citation: Guha N, Guyton KZ, Loomis D, Barupal DK. 2016. Prioritizing chemicals for risk assessment using chemoinformatics: examples from the IARC Monographs on Pesticides. Environ Health Perspect 124:1823-1829; http://dx.doi.org/10.1289/EHP186.

  1. 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.

  2. Dioxin Revisited: Developments Since the 1997 IARC Classification of Dioxin as a Human Carcinogen

    PubMed Central

    Steenland, Kyle; Bertazzi, Pier; Baccarelli, Andrea; Kogevinas, Manolis

    2004-01-01

    In 1997 the International Agency for Research on Cancer (IARC) classified 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD; the most potent dioxin congener) as a group 1 carcinogen based on limited evidence in humans, sufficient evidence in experimental animals, and extensive mechanistic information indicating that TCDD acts through a mechanism involving the aryl hydrocarbon receptor (AhR), which is present in both humans and animals. The judgment of limited evidence in humans was based primarily on an elevation of all cancers combined in four industrial cohorts. The group 1 classification has been somewhat controversial and has been challenged in the literature in recent years. In this article we review the epidemiologic and mechanistic evidence that has emerged since 1997. New epidemiologic evidence consists primarily of positive exposure–response analyses in several of the industrial cohorts, as well as evidence of excesses of several specific cancers in the Seveso accident cohort. There are also new data regarding how the AhR functions in mediating the carcinogenic response to TCDD. The new evidence generally supports the 1997 IARC classification. PMID:15345337

  3. 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

  4. Use of high-throughput in vitro toxicity screening data in cancer hazard evaluations by IARC Monograph Working Groups.

    PubMed

    Chiu, Weihsueh A; Guyton, Kathryn Z; Martin, Matthew T; Reif, David M; Rusyn, Ivan

    2017-07-24

    Evidence regarding carcinogenic mechanisms serves a critical role in International Agency for Research on Cancer (IARC) Monograph evaluations. Three recent IARC Working Groups pioneered inclusion of the US Environmental Protection Agency (EPA) ToxCast program high-throughput screening (HTS) data to supplement other mechanistic evidence. In Monograph V110, HTS profiles were compared between perfluorooctanoic acid (PFOA) and prototypical activators across multiple nuclear receptors. For Monograph V112 -113, HTS assays were mapped to 10 key characteristics of carcinogens identified by an IARC expert group, and systematically considered as an additional mechanistic data stream. Both individual assay results and ToxPi-based rankings informed mechanistic evaluations. Activation of multiple nuclear receptors in HTS assays showed that PFOA targets peroxisome proliferator activated and other receptors. ToxCast assays substantially covered 5 of 10 key characteristics, corroborating literature evidence of "induces oxidative stress" and "alters cell proliferation, cell death or nutrient supply" and filling gaps for "modulates receptor-mediated effects." Thus, ToxCast HTS data were useful both in evaluating specific mechanistic hypotheses and in the overall evaluation of mechanistic evidence. However, additional HTS assays are needed to provide more comprehensive coverage of the 10 key characteristics of carcinogens that form the basis of current IARC mechanistic evaluations.

  5. 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

  6. 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.

  7. A review of the carcinogenic potential of glyphosate by four independent expert panels and comparison to the IARC assessment.

    PubMed

    Williams, Gary M; Aardema, Marilyn; Acquavella, John; Berry, Sir Colin; Brusick, David; Burns, Michele M; de Camargo, Joao Lauro Viana; Garabrant, David; Greim, Helmut A; Kier, Larry D; Kirkland, David J; Marsh, Gary; Solomon, Keith R; Sorahan, Tom; Roberts, Ashley; Weed, Douglas L

    2016-09-01

    The International Agency for Research on Cancer (IARC) published a monograph in 2015 concluding that glyphosate is "probably carcinogenic to humans" (Group 2A) based on limited evidence in humans and sufficient evidence in experimental animals. It was also concluded that there was strong evidence of genotoxicity and oxidative stress. Four Expert Panels have been convened for the purpose of conducting a detailed critique of the evidence in light of IARC's assessment and to review all relevant information pertaining to glyphosate exposure, animal carcinogenicity, genotoxicity, and epidemiologic studies. Two of the Panels (animal bioassay and genetic toxicology) also provided a critique of the IARC position with respect to conclusions made in these areas. The incidences of neoplasms in the animal bioassays were found not to be associated with glyphosate exposure on the basis that they lacked statistical strength, were inconsistent across studies, lacked dose-response relationships, were not associated with preneoplasia, and/or were not plausible from a mechanistic perspective. The overall weight of evidence from the genetic toxicology data supports a conclusion that glyphosate (including GBFs and AMPA) does not pose a genotoxic hazard and therefore, should not be considered support for the classification of glyphosate as a genotoxic carcinogen. The assessment of the epidemiological data found that the data do not support a causal relationship between glyphosate exposure and non-Hodgkin's lymphoma while the data were judged to be too sparse to assess a potential relationship between glyphosate exposure and multiple myeloma. As a result, following the review of the totality of the evidence, the Panels concluded that the data do not support IARC's conclusion that glyphosate is a "probable human carcinogen" and, consistent with previous regulatory assessments, further concluded that glyphosate is unlikely to pose a carcinogenic risk to humans.

  8. Carcinogenicity of consumption of red meat and processed meat: A review of scientific news since the IARC decision.

    PubMed

    Domingo, José L; Nadal, Martí

    2017-07-01

    In October 2015, the International Agency for Research on Cancer (IARC) issued a press release on the results of the evaluation of the carcinogenicity of red and processed meat. Based on the accumulated scientific literature, the consumption of red meat was classified as "probably carcinogenic to humans" and processed meat as "carcinogenic to humans". Given the importance of this topic, this review was aimed at revising the current state-of-the-art on the carcinogenicity of red and processed meat, some time after the IARC decision. Some new epidemiological studies and new reviews clearly supporting the IARC decision have been published during these months. However, a number of gaps still exist. It is basic to establish the mechanisms leading to the increased risk of colorectal cancer (CRC) and other cancers arising from red and processed meat consumption. Another important pending issue is to establish the role of known/suspected carcinogens contained in uncooked or unprocessed meats, as well as the influence of cooking. Finally, it would be highly recommended to conduct new epidemiological studies to elucidate whether the consumption of white meat, such as pork and/or poultry, are -positively or inversely-associated with an increased risk of CRC and other types of cancer. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Prevalence of genotoxic chemicals among animal and human carcinogens evaluated in the IARC Monograph Series.

    PubMed

    Bartsch, H; Malaveille, C

    1989-06-01

    To determine whether genotoxic and non-genotoxic carcinogens contribute similarly to the cancer burden in humans, an analysis was performed on agents that were evaluated in Supplements 6 and 7 to the IARC Monographs for their carcinogenic effects in humans and animals and for the activity in short-term genotoxicity tests. The prevalence of genotoxic carcinogens on four groups of agents, consisting of established human carcinogens (group 1, n = 30), probable human carcinogens (group 2A, n = 37), possible human carcinogens (group 2B, n = 113) and on agents with limited evidence of carcinogenicity in animals (a subset of group 3, n = 149) was determined. A high prevalence in the order of 80 to 90% of genotoxic carcinogens was found in each of the groups 1, 2A and 2B, which were also shown to be multi-species/multi-tissues carcinogens. The distribution of carcinogenic potency in rodents did not reveal any specific characteristic of the human carcinogens in group 1 that would differentiate them from agents in groups 2A, 2B and 3. The results of this analysis indicate that (a) an agent with unknown carcinogenic potential showing sufficient evidence of activity in in vitro/in vivo genotoxicity assays (involving as endpoints DNA damage and chromosomal/mutational damage) may represent a hazard to humans; and b) an agent showing lack of activity in this spectrum of genotoxicity assays should undergo evaluation for carcinogenicity by rodent bioassay, in view of the present lack of validated short-term tests for non-genotoxic carcinogens. Overall, this analysis implies that genotoxic carcinogens add more to the cancer burden in man than non-genotoxic carcinogens. Thus, identification of such genotoxic carcinogens and subsequent lowering of exposure will remain the main goal for primary cancer prevention in man.

  10. Comparison between carcinogenicity and mutagenicity based on chemicals evaluated in the IARC monographs.

    PubMed Central

    Bartsch, H; Tomatis, L

    1983-01-01

    The qualitative relationship between carcinogenicity and mutagenicity (DNA-damaging activity), based on chemicals which are known to be or suspected of being carcinogenic to man and/or to experimental animals, is analyzed using 532 chemicals evaluated in Volumes 1-25 of the IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. About 40 compounds (industrial processes) were found to be either definitely or probably carcinogenic to man, and 130 chemicals have been adequately tested in rodents and most of them also in various short-term assays. For a comparison between the carcinogenicity of a chemical and its behavior in short-term tests, systems were selected that have a value for predicting carcinogenicity. These were divided into mutagenicity in (A) the S. typhimurium/microsome assay, (B) other submammalian systems and (C) cultured mammalian cells; (D) chromosomal abnormalities in mammalian cells; (E) DNA damage and repair; (F) cell transformation (or altered growth properties) in vitro. The following conclusions can be drawn. In the absence of studies in man, long-term animal tests are still today the only ones capable of providing evidence of the carcinogenic effect of a chemical. The development and application of an appropriate combination of short-term tests (despite current limitations) can significantly contribute to the prediction/confirmation of the carcinogenic effects of chemicals in animals/man. Confidence in positive tests results is increased when they are confirmed in multiple short-term tests using nonrepetitive end points and different activation systems. Assays to detect carcinogens which do not act via electrophiles (promoters) need to be developed. The results of a given short-term test should be interpreted in the context of other toxicological data. Increasing demand for quantitative carcinogenicity data requires further examination of whether or not there is a quantitative relationship between the potency of a

  11. IARC use of oxidative stress as key mode of action characteristic for facilitating cancer classification: Glyphosate case example illustrating a lack of robustness in interpretative implementation.

    PubMed

    Bus, James S

    2017-03-06

    The International Agency for Research on Cancer (IARC) has formulated 10 key characteristics of human carcinogens to incorporate mechanistic data into cancer hazard classifications. The analysis used glyphosate as a case example to examine the robustness of IARC's determination of oxidative stress as "strong" evidence supporting a plausible cancer mechanism in humans. The IARC analysis primarily relied on 14 human/mammalian studies; 19 non-mammalian studies were uninformative of human cancer given the broad spectrum of test species and extensive use of formulations and aquatic testing. The mammalian studies had substantial experimental limitations for informing cancer mechanism including use of: single doses and time points; cytotoxic/toxic test doses; tissues not identified as potential cancer targets; glyphosate formulations or mixtures; technically limited oxidative stress biomarkers. The doses were many orders of magnitude higher than human exposures determined in human biomonitoring studies. The glyphosate case example reveals that the IARC evaluation fell substantially short of "strong" supporting evidence of oxidative stress as a plausible human cancer mechanism, and suggests that other IARC monographs relying on the 10 key characteristics approach should be similarly examined for a lack of robust data integration fundamental to reasonable mode of action evaluations.

  12. An IARC Manual series aimed at assisting cancer epidemiology and prevention. "Environmental carcinogens: selected methods of analysis".

    PubMed

    O'Neill, I K; Fishbein, L

    1986-01-01

    Since 1975, the IARC has been preparing a series of volumes entitled "Environmental Carcinogens: Selected Methods of Analysis" (IARC Manual series) of which the purposes are to assist analysts, epidemiologists and regulatory authorities in planning or performing exposure measurements that are truly comparable between different studies. The Manual series provides expert information within each volume on multi-media sampling, methods of analyses and some background of epidemiology, metabolism, use/occurrence for a group of known or suspect carcinogens. So far, eleven volumes have been published or are in preparation on the following subjects: N-nitrosamines, vinyl chloride, PAH, aromatic amines, mycotoxins, N-nitroso compounds, volatile halogenated hydrocarbons, metals, passive smoking, benzene and alkylated benzenes, dioxins, PCDFs and PCBs. The presentation will discuss needs and priorities for use of analytical chemistry in estimating exposures of apparently greatest relevance to cancer causation, i.e. the approach to developing this series. Indications from epidemiology, evaluations of carcinogenic risk to humans, and recent developments in total exposure assessment are that new methods and matrices need more emphasis, e.g. as with biochemical dosimetry, exhaled breath, and in indoor air.

  13. Reevaluations of dosimetric factors: Hiroshima and Nagasaki

    SciTech Connect

    Bond, V.P.; Thiessen, J.W.

    1982-01-01

    Separate abstracts were prepared for the 13 papers in this proceedings of a symposium on the reevaluation of dosimetric factors for Hiroshima and Nagasaki. A summary and general discussion are included at the end of the proceedings. (KRM)

  14. Opportunities to Participate in Pesticide Reevaluation

    EPA Pesticide Factsheets

    Submitting relevant information through public dockets during comment periods, and other means of input and involvement, is vital to effective reevaluation of pesticides. Find out more about opportunities for public involvement in registration review.

  15. 78 FR 14540 - Cyromazine, Silica Silicates (Silica Dioxide and Silica Gel), Glufosinate Ammonium, Dioctyl...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-06

    ... AGENCY Cyromazine, Silica Silicates (Silica Dioxide and Silica Gel), Glufosinate Ammonium, Dioctyl Sodium... the registration review of cyromazine, silica silicates (silica dioxide and silica gel), glufosinate...). Silica silicates, silicon dioxide and silica gel, are insecticides and acaracides used in...

  16. 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

  17. 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.

  18. 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

  19. Reevaluating the Basic Public Speaking Course.

    ERIC Educational Resources Information Center

    Dalton, Diana G.

    This essay develops the position that the basic public speaking course is in need of reevaluation. Topics discussed include the importance of adopting a critical pedagogical stance, Paolo Freire's (1983) banking versus problem-posing concepts of education, the problems arising from the prevalent use of teaching assistants as public speaking…

  20. 14 CFR 161.413 - Reevaluation procedure.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of Stage 3 Restrictions... FAA. The FAA will specifically solicit comments from the affected airport operator and affected local... information from the aircraft operator, airport operator, and others known to have information material to...

  1. 14 CFR 161.413 - Reevaluation procedure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of Stage 3 Restrictions... FAA. The FAA will specifically solicit comments from the affected airport operator and affected local... information from the aircraft operator, airport operator, and others known to have information material to...

  2. 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

  3. A Reevaluation of the 60% Gradeability Requirement

    DTIC Science & Technology

    1975-01-01

    D IT MTHNTtM/IMUSRITY WOK Bi*C ÜAR. äa’/ar"tfECÜT \\ A REEVALUATION OF THE 60% GRADEABILITY REQUIREMENT JANUARY 197 5 Richard L...The interdependency of gradeability with total system performance has been stressed and demonstrated. Gradeability cannot be treated as an... stress that the vehicle must be capable of approaching and leaving a 60* slope; rather it emphasizes performance on the slope. The only geometric

  4. Reevaluation of HFIR source term: Supplement 2

    SciTech Connect

    Thomas, W.E.

    1986-11-01

    The HFIR source term has been reevaluated to assess the impact of the increase in core lifetime from 15 to 24 days. Calculations were made to determine the nuclide activities of the iodines, noble gases, and other fission products. The results show that there is no significant change in off-site dose due to the increased fuel cycle for the release scenario postulated in ORNL-3573.

  5. Screening assays for carcinogenic agents and mixtures: an appraisal based on data in the IARC Monograph series.

    PubMed

    Bartsch, H; Malaveille, C

    1990-01-01

    To determine whether genotoxic and non-genotoxic carcinogens contribute similarly to the cancer burden in humans and which types of short-term test are more relevant for predicting human hazards, an analysis was performed on agents that were evaluated in IARC Monographs Supplements 6 and 7 for their carcinogenic effects in humans and animals and for activity in short-term genotoxicity tests. The prevalence of genotoxicity among four groups of agents, consisting of established human carcinogens (group 1, n = 30), probable human carcinogens (group 2A, n = 37), possible human carcinogens (group 2B, n = 113) and agents with limited evidence of carcinogenicity in animals (a subset of group 3, n = 66) was determined. Each of the groups 1, 2A and 2B contained a high proportion (80-90%) of genotoxic carcinogens, which were also multi-species or multi-tissue carcinogens. The distribution of carcinogenic potency in rodents did not reveal any specific characteristic of the human carcinogens in group 1 that would differentiate them from agents in groups 2A, 2B and many in group 3. Although limited by the data-base available through the Monographs series, this analysis implies that genotoxic carcinogens add more to the human cancer burden than non-genotoxic carcinogens. Thus, the continued use of in vitro/in vivo short-term tests, involving as endpoints DNA chromosomal or mutational damage, to identify genotoxic carcinogens or in the isolation of carcinogenic components in complex mixtures is fully justified. It is concluded that (a) an agent or complex mixture with unknown carcinogenic potential showing sufficient evidence of activity in genotoxicity assays in vitro or in vivo is likely to represent a hazard to humans and (b) an agent or complex mixture showing lack of activity in this spectrum of genotoxicity assays should undergo evaluation for carcinogenicity for rodent bioassay, in view of the present lack of validated short-term tests for non-genotoxic carcinogens.

  6. [A survey on workers' individual exposure to crystalline silica in the building industry].

    PubMed

    Miscetti, G; Bodo, Patrizia; Garofani, Patrizia; Abbritti, E P; Luciani, Giuliana; Mazzanti, Manuela; Bessi, Loredana; Marsili, G

    2011-01-01

    The wide-spread presence of silica in nature and the variety of materials containing it cause crystalline silica exposure of workers in various industrial activities. Moreover crystalline silica is classified as carcinogenic to humans (Group 1) by IARC, in relation to its possible lung carcinogenicity. The purpose of this paper was to assess respirable particles and crystalline silica exposure of workers in a number of some building sites located in the area of a Local Health Unit in the Umbria region. The study examined differences in four types of building sites: "construction of new buildings", "renovation of old buildings", "road construction" and "transport of aggregates by loaders in crushing plants". According to the strategy suggested by European Standard EN 689/1997, personal air samples were collected during work in jobs characterized by elevated amounts of widespread dust. Analysis of data showed that levels of exposure to crystalline silica were lower than the limits recommended by ACGIH/2010 in almost all samples except one. The percentages of crystalline silica in respirable particles were in the range 0.4%-21%. Crystalline silica exposure levels were different in the various jobs and comparison between the mean values of exposure levels in each one showed statistically significant differences (p < 0.01, variance analysis). Work with the highest exposure to crystalline silica were: brick cutting, plaster brushing, "Serena stone" cutting, as they use tools operating at high speed and often in dry conditions (grinder, power drill, pneumatic hammer), producing low-size airborne particles (respirable fraction). During work in these jobs levels of worker exposure to crystalline silica showed high variability, so that it was impossible to establish if in the medium-long term, they were lower than the Threshold Limit Values with a set probabilistic certainty (OTL test, confidence level 95%). In the remaining jobs the assessment of occupational exposures to

  7. 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

  8. 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.

  9. 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.

  10. 23 CFR 771.129 - Re-evaluations.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... RELATED PROCEDURES § 771.129 Re-evaluations. (a) A written evaluation of the draft EIS shall be prepared... needed. (b) A written evaluation of the final EIS will be required before further approvals may be... 23 Highways 1 2010-04-01 2010-04-01 false Re-evaluations. 771.129 Section 771.129 Highways...

  11. 40 CFR 93.157 - Reevaluation of conformity.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Reevaluation of conformity. 93.157... (CONTINUED) DETERMINING CONFORMITY OF FEDERAL ACTIONS TO STATE OR FEDERAL IMPLEMENTATION PLANS Determining Conformity of General Federal Actions to State or Federal Implementation Plans § 93.157 Reevaluation...

  12. 14 CFR 161.403 - Criteria for reevaluation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of Stage 3 Restrictions... change in the noise environment of the affected airport and that a review and reevaluation pursuant to... noncompatible land uses, within an airport noise study area. For approved restrictions, calculation of...

  13. 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. Copyright © 2014 Institute of Psychoanalysis.

  14. On reevaluation rate in discrete time Hogg-Huberman model

    NASA Astrophysics Data System (ADS)

    Tanaka, Toshijiro; Shibata, Junko; Inoue, Masayoshi

    2002-06-01

    The discrete time Hogg-Huberman model is extended to a case with time-dependent reevaluation rate at which agents using one resource decide to evaluate their resource choice. In this paper the time dependence of the reevaluation rate is determined by states of the system. The dynamical behavior of the extended Hogg-Huberman model is discussed. It is found that the change of fraction of agents using resource 1 is suppressed to be smaller than that in the case of constant reevaluation rate.

  15. 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.

  16. 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.

  17. Reevaluating excess success in psychological science.

    PubMed

    van Boxtel, Jeroen J A; Koch, Christof

    2016-10-01

    Francis (Psychonomic Bulletin Review, 21, 1180-1187, 2014) recently claimed that 82 % of articles with four or more experiments published in Psychological Science between 2009 and 2012 cannot be trusted. We critique Francis' analysis and point out the dependence of his approach on including the appropriate experiments and significance tests. We focus on one of the articles (van Boxtel & Koch, in Psychological Science, 23(4), 410-418, 2012) flagged by Francis and show that the inappropriate inclusion of experiments and tests have led Francis to mistakenly flag this article. We found that decisions about whether to include certain tests potentially affect 34 of the 44 articles analyzed by Francis. We further performed p-curve analyses on the articles discussed in Francis' analysis. We found that 9 of 44 studies showed significant evidential value, 11 studies showed insufficient evidential value, and 1 study showed evidence of p-hacking. Our reevaluation is important, because some researchers may have gained the false impression that none of the quoted articles in Psychological Science can be trusted (as stated by Francis). The analysis by Francis is most likely insufficient to warrant this conclusion for some articles and certainly is insufficient with respect to the study by van Boxtel and Koch (Psychological Science, 23, 410-418, 2012).

  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. 14 CFR 161.405 - Request for reevaluation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... ordinance, airport rule, lease, or other document; (3) The quantified change in the noise environment using...) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of Stage 3...

  20. 24 CFR 965.407 - Reevaluations of mastermeter systems.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... URBAN DEVELOPMENT PHA-OWNED OR LEASED PROJECTS-GENERAL PROVISIONS Individual Metering of Utilities for Existing PHA-Owned Projects § 965.407 Reevaluations of mastermeter systems. Because of changes in the cost...

  1. 24 CFR 965.407 - Reevaluations of mastermeter systems.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... URBAN DEVELOPMENT PHA-OWNED OR LEASED PROJECTS-GENERAL PROVISIONS Individual Metering of Utilities for Existing PHA-Owned Projects § 965.407 Reevaluations of mastermeter systems. Because of changes in the cost...

  2. 24 CFR 965.407 - Reevaluations of mastermeter systems.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... URBAN DEVELOPMENT PHA-OWNED OR LEASED PROJECTS-GENERAL PROVISIONS Individual Metering of Utilities for Existing PHA-Owned Projects § 965.407 Reevaluations of mastermeter systems. Because of changes in the cost...

  3. 24 CFR 965.407 - Reevaluations of mastermeter systems.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... URBAN DEVELOPMENT PHA-OWNED OR LEASED PROJECTS-GENERAL PROVISIONS Individual Metering of Utilities for Existing PHA-Owned Projects § 965.407 Reevaluations of mastermeter systems. Because of changes in the cost...

  4. 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.

  5. 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. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

  6. 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.

  7. Silazine to silica

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.

    1993-01-01

    Thin film silica and/or methyl silicone were detected on most external surfaces of the retrieved LDEF. Both solar ultraviolet radiation and atomic oxygen can convert silicones to silica. Known sources of silicone in or on the LDEF appear inadequate to explain the ubiquitous presence of the silica and silicone films. Hexamethyldisilazane (HMDS) was used as the Challenger tile waterproofing compound for the Challenger/LDEF deployment mission. HMDS is both volatile and chemically reactive at STP. In addition, HMDS releases NH3 which depolymerizes silicone RTV's. Polyurethanes are also depolymerized. Experiments are reported that indicate much of the silicone and silica contamination of LDEF resulted directly or indirectly from HMDS.

  8. 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.

  9. 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

  10. Evaluations of the Carcinogenicity of Carbon Nanotubes, Fluoro-Edinite, and Silicon Carbide by the International Agency for Research on Cancer (IARC).

    PubMed

    Morimoto, Yasuo; Kobayashi, Norihiro

    2016-01-01

    We reported the evaluations of the carcinogenicity of fluoro-edinite, silicon carbide, and carbon nanotubes performed by IARC working group in October 2014. For carbon nanotubes (CNTs), multi-walled carbon nanotube (MWCNT)-7 was classified as Group 2B, and MWCNTs without MWCNT-7 and single-walled carbon nanotubes (SWCNTs) were classified as not classifiable in terms of their carcinogenicity to humans. There is sufficient evidence of carcinogenicity for MWCNT-7 in experimental animals, limited evidence for other MWCNTs, and inadequate evidence for SWCNTs. The mechanic evidence for CNTs was not strong. Fluoro-edinite was classified as carcinogenic to humans (Group 1) on the basis of sufficient evidence of carcinogenicity to humans and experimental animals. Silicon carbide was classified into silicon carbide fibers and whiskers. Silicon carbide fibers were evaluated as possibly carcinogenic to humans (Group 2B) on the basis of limited evidence of carcinogenicity to humans. Silicon carbide whiskers were evaluated as probably carcinogenic to humans (Group 2A) on the basis of sufficient evidence of carcinogenicity to experimental animals and the similarity of their physicochemical properties to those of asbestos in terms of the mechanism of carcinogenicity. We report the process of progression in meeting and discuss how to determine the evidence and the evaluation of the carcinogenicity of the three materials.

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

    PubMed

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

    1996-09-01

    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.

  12. Warning System Re-Evaluation and Local Government Guidance Update

    DTIC Science & Technology

    1979-08-07

    Provide an alerting and warning system for government activities and the general public who will be housed in the eastern El Paso County area. C. 6...LEVEI WARNING SYSTEM RE-EVALUATION eAND C) LOCAL GOVERNMENT GUIDANCE UPDATE FINAL REPORT AUGUST 1979 DCPA 01-78-C-0229 DCPA WORK UNIT 2234D CSC-4527...at seCUltivy CLA854PCATW Op Tol PA56mb" D b WARNING SYSTEM RE-EVALUATION AND LOCAL GOVERNMENT GUIDANCE UPDATE FINAL REPORT AUGUST 1979 Prepared for

  13. Silica, Silicosis, and Autoimmunity.

    PubMed

    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.

  14. 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

  15. 14 CFR 161.409 - Required analysis by reevaluation petitioner.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... § 161.305; and (5) Sufficient data and analysis selected from § 161.305, as applicable to the... 14 Aeronautics and Space 3 2012-01-01 2012-01-01 false Required analysis by reevaluation petitioner. 161.409 Section 161.409 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF...

  16. 14 CFR 161.409 - Required analysis by reevaluation petitioner.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... § 161.305; and (5) Sufficient data and analysis selected from § 161.305, as applicable to the... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Required analysis by reevaluation petitioner. 161.409 Section 161.409 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF...

  17. 14 CFR 161.409 - Required analysis by reevaluation petitioner.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... § 161.305; and (5) Sufficient data and analysis selected from § 161.305, as applicable to the... 14 Aeronautics and Space 3 2013-01-01 2013-01-01 false Required analysis by reevaluation petitioner. 161.409 Section 161.409 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF...

  18. 14 CFR 161.407 - Notice of reevaluation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of Stage 3 Restrictions... circulation throughout the airport noise study area (or the airport vicinity for agreements where an airport noise study area has not been delineated); post a notice in the airport in a prominent...

  19. 14 CFR 161.405 - Request for reevaluation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of Stage 3 Restrictions... ordinance, airport rule, lease, or other document; (3) The quantified change in the noise environment using... operator must include the following information: (1) The name of the airport and associated cities...

  20. 14 CFR 161.407 - Notice of reevaluation.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of Stage 3 Restrictions... circulation throughout the airport noise study area (or the airport vicinity for agreements where an airport noise study area has not been delineated); post a notice in the airport in a prominent...

  1. 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... noncompatible land uses, within an airport noise study area. For approved restrictions, calculation of...

  2. 14 CFR 161.407 - Notice of reevaluation.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Notice of reevaluation. 161.407 Section 161.407 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED... circulation throughout the airport noise study area (or the airport vicinity for agreements where an...

  3. 14 CFR 161.403 - Criteria for reevaluation.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... change in the noise environment of the affected airport and that a review and reevaluation pursuant to the criteria in § 161.305 is therefore justified. (1) A change in the noise environment sufficient to... in the noise environment or in the noncompatible land uses may be either an increase or decrease...

  4. 23 CFR 771.129 - Re-evaluations.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 23 Highways 1 2011-04-01 2011-04-01 false Re-evaluations. 771.129 Section 771.129 Highways FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RIGHT-OF-WAY AND ENVIRONMENT ENVIRONMENTAL IMPACT AND... to establish whether or not the approved environmental document or CE designation remains valid for...

  5. 34 CFR 603.23 - Initial recognition, and reevaluation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 3 2010-07-01 2010-07-01 false Initial recognition, and reevaluation. 603.23 Section 603.23 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION SECRETARY'S RECOGNITION PROCEDURES FOR STATE AGENCIES...

  6. 14 CFR 161.409 - Required analysis by reevaluation petitioner.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... TRANSPORTATION (CONTINUED) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of... agreement as incorporated in a local ordinance, airport rule, lease, or other document; (2) The aircraft... either an adequate environmental assessment of the impacts of discontinuing all or part of a...

  7. 14 CFR 161.409 - Required analysis by reevaluation petitioner.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... TRANSPORTATION (CONTINUED) AIRPORTS NOTICE AND APPROVAL OF AIRPORT NOISE AND ACCESS RESTRICTIONS Reevaluation of... agreement as incorporated in a local ordinance, airport rule, lease, or other document; (2) The aircraft... either an adequate environmental assessment of the impacts of discontinuing all or part of a...

  8. Application of silica nanoparticles for increased silica availability in maize

    NASA Astrophysics Data System (ADS)

    Suriyaprabha, R.; Karunakaran, G.; Yuvakkumar, R.; Prabu, P.; Rajendran, V.; Kannan, N.

    2013-02-01

    Silica nanoparticles were extracted from rice husk and characterised comprehensively. The synthesised silica powders were amorphous in size with 99.7% purity (20-40 nm). Nanosilica was amended with red soil at 15 kg ha-1 along with micron silica. The influence of nanoscale on silica uptake, accumulation and nutritional variations in maize roots were evaluated through the studies such as root sectioning, elemental analysis and physiological parameters (root length and silica content) and compared with micron silica and control. Nanosilica treated soil reveals enhanced silica uptake and elongated roots which make the plant to resist in stress conditions like drought.

  9. 42 CFR 405.213 - Re-evaluation of a device categorization.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 2 2010-10-01 2010-10-01 false Re-evaluation of a device categorization. 405.213... Decisions That Relate to Health Care Technology § 405.213 Re-evaluation of a device categorization. (a... experimental/investigational (Category A) may request re-evaluation of the categorization decision. (2)...

  10. 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.

  11. Cellulose-silica aerogels.

    PubMed

    Demilecamps, Arnaud; Beauger, Christian; Hildenbrand, Claudia; Rigacci, Arnaud; Budtova, Tatiana

    2015-05-20

    Aerogels based on interpenetrated cellulose-silica networks were prepared and characterised. Wet coagulated cellulose was impregnated with silica phase, polyethoxydisiloxane, using two methods: (i) molecular diffusion and (ii) forced flow induced by pressure difference. The latter allowed an enormous decrease in the impregnation times, by almost three orders of magnitude, for a sample with the same geometry. In both cases, nanostructured silica gel was in situ formed inside cellulose matrix. Nitrogen adsorption analysis revealed an almost threefold increase in pores specific surface area, from cellulose aerogel alone to organic-inorganic composite. Morphology, thermal conductivity and mechanical properties under uniaxial compression were investigated. Thermal conductivity of composite aerogels was lower than that of cellulose aerogel due to the formation of superinsulating mesoporous silica inside cellulose pores. Furthermore, composite aerogels were stiffer than each of reference aerogels.

  12. 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.

  13. 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. © Crown copyright 2014.

  14. Taxonomic and phylogenetic re-evaluation of Mycena illuminans.

    PubMed

    Chew, Audrey L C; Tan, Yee-Shin; Desjardin, Dennis E; Musa, Md Yusoff; Sabaratnam, Vikineswary

    2013-01-01

    Mycena illuminans Henn. is described and re-evaluated based on recently collected material from peninsular Malaysia, providing comprehensive descriptions, illustrations and photographs. In addition to morphological data, axenic monokaryon and dikaryon cultures were established to provide data on culture morphology and the mating system of the species. Molecular sequences data from the nuclear large subunit (LSU) gene also are presented, confirming that M. illuminans is not a synonym of Mycena chlorophos.

  15. 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.

  16. [The probability of developing brain tumours among users of cellular telephones (scientific information to the decision of the International Agency for Research on Cancer (IARC) announced on May 31, 2011)].

    PubMed

    Grigor'ev, Iu G

    2011-01-01

    The WHO's International Agency for Research on Cancer (IARC) has made May 31 2011 PRESS RELEASE No 208 which classifies radiofrequency electromagnetic fields as possibly carcinogenic to humans (Group 2B). The decision is based on an increased risk of glioma, i.e., a malignant type of brain cancer associated with the wireless phone use. This paper reports the analysis of the long-term research on the issue in question that had been carried out in many countries around the world before the decision was made.

  17. Analysis of different versions of the IARC p53 database with respect to G-->T transversion mutation frequencies and mutation hotspots in lung cancer of smokers and non-smokers.

    PubMed

    Paschke, T

    2000-11-01

    Analysis of the IARC p53 database revealed a large number of discrepancies in the classification of smoking status for identical lung cancer entries in different versions of the database. In addition, no statistically significant differences in G-->T transversion mutation frequencies or in mutational hotspots at codons 157, 248 and 273 were found in the R3 version of the database between p53 sequences from smoking and non-smoking lung cancer patients. The possible influence of confounding factors on p53 mutation spectra was demonstrated as illustrated by the impact of ethnicity on G-->T transversion mutation frequencies.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. [Postmarketing herbs clinical evaluation should concern about re-evaluating symptoms].

    PubMed

    He, Wei; Xie, Yanming; Wang, Yongyan

    2010-06-01

    Re-evaluation of premarketing medicine is a important supplementary of clinical and elementary research. It is a basement that establish the medicine administration supervisition , found and integrity postmarketing washing out mechanism and define reasonable using drug. After drug marketing, we must not only concern on the re-evaluation of herbs security but also focus on evaluating herbs suitable symptom, as well as its dosage and course of treatment, ect. The re-evaluation of symptoms were seen as the core and feature of traditional Chinese medicine's clinical evaluation. It is also seen as hot spot and difficulty of the research . This article try to focus on simply illustrating the necessity and research thinking of re-evaluation symptoms of postmarketing herbs. So we can define the re-evaluation of postmarketing drug's objection, method, and basement. It will provide beneficial experience and reference to re-evaluation symptom of marketed herbs.

  4. 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.

  5. 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.

  6. [Re-evaluation of the fundamentals of trace elements].

    PubMed

    Himeno, Seiichiro

    2012-01-01

    The roles of trace elements have been extensively studied for decades. However, recent advances in both molecular and epidemiological studies on trace elements have provided new information and concepts on the actions of trace elements. Some of our fundamental knowledge on the roles of trace elements based on classical data should be replaced by new concept based on new findings. This series of "Re-evaluation of the Fundamentals of Trace Elements" aims to provide new fundamentals on trace elements by reviewing rapidly advancing knowledge in this study area. The first article is a critical review on the role of chromium in human nutrition.

  7. The organizational learning survey: a re-evaluation of unidimensionality.

    PubMed

    Goh, Swee C; Quon, Tony K; Cousins, J Bradley

    2007-12-01

    An earlier study by Chakrabarty and Rogé evaluated the dimensionality of the Organizational Learning Survey for assessing the learning capability of organizations developed by Goh and Richards. In this paper, the survey was re-evaluated for unidimensionality using both exploratory and confirmatory factor analysis. Retaining 18 of the original 21 items was sufficient to establish unidimensionality. A number of different confirmatory models validated the unidimensional measurement model on two independent data sets. Implications for further empirical research using this inventory are discussed.

  8. 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...

  9. Dynamics of a Hogg-Huberman Model with Time Dependent Reevaluation Rates

    NASA Astrophysics Data System (ADS)

    Tanaka, Toshijiro; Kurihara, Tetsuya; Inoue, Masayoshi

    2006-05-01

    The dynamical behavior of the Hogg-Huberman model with time-dependent reevaluation rates is studied. The time dependence of the reevaluation rate that agents using one of resources decide to consider their resource choice is obtained in terms of states of the system. It is seen that the change of fraction of agents using one resource is suppressed to be smaller than that in the case of a fixed reevaluation rate and the chaos control in the system associated with time-dependent reevaluation rates can be performed by the system itself.

  10. Re-evaluation of learned information in Drosophila.

    PubMed

    Felsenberg, Johannes; Barnstedt, Oliver; Cognigni, Paola; Lin, Suewei; Waddell, Scott

    2017-04-13

    Animals constantly assess the reliability of learned information to optimize their behaviour. On retrieval, consolidated long-term memory can be neutralized by extinction if the learned prediction was inaccurate. Alternatively, retrieved memory can be maintained, following a period of reconsolidation during which it is labile. Although extinction and reconsolidation provide opportunities to alleviate problematic human memories, we lack a detailed mechanistic understanding of memory updating. Here we identify neural operations underpinning the re-evaluation of memory in Drosophila. Reactivation of reward-reinforced olfactory memory can lead to either extinction or reconsolidation, depending on prediction accuracy. Each process recruits activity in specific parts of the mushroom body output network and distinct subsets of reinforcing dopaminergic neurons. Memory extinction requires output neurons with dendrites in the α and α' lobes of the mushroom body, which drive negatively reinforcing dopaminergic neurons that innervate neighbouring zones. The aversive valence of these new extinction memories neutralizes previously learned odour preference. Memory reconsolidation requires the γ2α'1 mushroom body output neurons. This pathway recruits negatively reinforcing dopaminergic neurons innervating the same compartment and re-engages positively reinforcing dopaminergic neurons to reconsolidate the original reward memory. These data establish that recurrent and hierarchical connectivity between mushroom body output neurons and dopaminergic neurons enables memory re-evaluation driven by reward-prediction error.

  11. 24 CFR 58.47 - Re-evaluation of environmental assessments and other environmental findings.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false Re-evaluation of environmental....47 Re-evaluation of environmental assessments and other environmental findings. (a) A responsible... circumstances and environmental conditions which may affect the project or have a bearing on its impact, such...

  12. 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...

  13. Re-evaluating the age of the Haughton impact event

    NASA Astrophysics Data System (ADS)

    Sherlock, Sarah C.; Kelley, Simon P.; Parnell, John; Green, Paul; Lee, Pascal; Osinski, Gordon R.; Cockell, Charles S.

    2005-12-01

    We have re-evaluated the published age information for the Haughton impact structure, which was believed to have formed ˜23 Ma ago during the Miocene age, and report new Ar/Ar laser probe data from shocked basement clasts. This reveals an Eocene age, which is at odds with the published Miocene stratigraphic, apatite fission track and Ar/Ar data; we discuss our new data within this context. We have found that the age of the Haughton impact structure is ˜39 Ma, which has implications for both crater recolonization models and post-impact hydrothermal activity. Future work on the relationship between flora and fauna within the crater, and others at high latitude, may resolve this paradox.

  14. Ankylosing spondylitis and secretor status: a re-evaluation.

    PubMed

    Smith, G W; James, V; Mackenzie, D A; Stewart, J; Blackwell, C C; Elton, R A; Nuki, G

    1997-07-01

    Non-secretion of ABO blood group substances in body fluids is associated with susceptibility to some bacterial infections. Non-secretors were previously found to be over-represented in patients with ankylosing spondylitis (AS) (49%) compared to controls (27%). Re-evaluation of secretor status in a population of 92 AS patients and 103 controls revealed identical proportions of non-secretors (28%). Of 43 patients studied in both surveys, 6/22 typed initially as non-secretors proved to be secretors using both haemagglutination inhibition assay (HAI) and enzyme-linked immunosorbent assay (ELISA) techniques. Loss of secreted blood group antigens in the saliva is the cause of this mis-typing. Careful attention to the method of collection, handling and preservation of saliva specimens is essential for accurate assessment of secretor status. Therefore, there is no link between secretor status and AS.

  15. [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.

  16. [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.

  17. Re-evaluating the phylogeny of allopolyploid Gossypium L.

    PubMed

    Grover, Corrinne E; Gallagher, Joseph P; Jareczek, Josef J; Page, Justin T; Udall, Joshua A; Gore, Michael A; Wendel, Jonathan F

    2015-11-01

    The formation of allopolyploid cotton precipitated a rapid diversification and colonization of dry coastal American tropical and subtropical regions. Previous phylogenetic analyses, combined with molecular divergence analyses, have offered a temporal framework for this radiation, but provide only weak support for some of the resolved branches. Moreover, these earlier analyses did not include the recently recognized sixth polyploid species, G. ekmanianum Wittmack. Here we use targeted sequence capture of multiple loci in conjunction with both concatenated and Bayesian concordance analyses to reevaluate the phylogeny of allopolyploid cotton species. Although phylogenetic resolution afforded by individual genes is often low, sufficient signal was attained both through the concatenated and concordance analyses to provide robust support for the Gossypium polyploid clade, which is reported here.

  18. 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

    ... reevaluate the payment of transportation and subsistence expenses to a threatened law enforcement... PROCEDURE REQUIREMENTS Policies and Procedures Relating to Threatened Law Enforcement/Investigative... to a threatened law enforcement/investigative employee? You must reevaluate the situation every 30...

  19. Serpentinization processes: Influence of silica

    NASA Astrophysics Data System (ADS)

    Huang, R.; Sun, W.; Ding, X.; Song, M.; Zhan, W.

    2016-12-01

    Serpentinization systems are highly enriched in molecular hydrogen (H2) and hydrocarbons (e.g. methane, ethane and propane). The production of hydrocarbons results from reactions between H2 and oxidized carbon (carbon dioxide and carbon monoxide), which possibly contribute to climate changes during early history of the Earth. However, the influence of silica on the production of H2 and hydrocarbons was poorly constrained. We performed experiments at 311-500 °C and 3.0 kbar using mechanical mixtures of silica and olivine in ratios ranging from 0 to 40%. Molecular hydrogen (H2), methane, ethane and propane were formed, which were analyzed by gas chromatography. It was found that silica largely decreased H2 production. Without any silica, olivine serpentinization produced 94.5 mmol/kg H2 after 20 days of reaction time. By contrast, with the presence of 20% silica, H2 concentrations decreased largely, 8.5 mmol/kg. However, the influence of silica on the production of hydrocarbons is negligible. Moreover, with the addition of 20%-40% silica, the major hydrous minerals are talc, which was quantified according to an established standard curve calibrated by infrared spectroscopy analyses. It shows that silica greatly enhances olivine hydration, especially at 500 °C. Without any addition of silica, reaction extents were <5% at 17 days during olivine serpentinization at 500 °C and 3.0 kbar. By contrast, with the presence of 50% silica, olivine was completely transformed to talc within 9 days. This study indicates that silica impedes the oxidation of ferrous iron into ferric iron, and that rates of olivine hydration in natural geological settings are much faster with silica supply.

  20. 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.

  1. Silica, Hybrid Silica, Hydride Silica and Non-Silica Stationary Phases for Liquid Chromatography. Part II: Chemical and Thermal Stability.

    PubMed

    Borges, Endler M; Volmer, Dietrich A

    2015-08-01

    In the first part of this review, stationary phases (silica, hybrid silica, hydride silica and non-silica stationary phases) were characterized and compared with respect to selectivity, efficiency, resolution, solvent consumption and analysis time. The present review focuses on the thermal and chemical stability of stationary phases. Stationary phases of high chemical and thermal stability are required for separations that are carried over a wide pH and/or temperature range. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  2. Silica activity in lunar lavas

    NASA Technical Reports Server (NTRS)

    Nash, W. P.; Haselton, J. D.

    1975-01-01

    Calculated values of log alpha SiO2 in lunar magmas range from approximately -0.8 to unity in the temperature range of 1100-1300 C. High-titanium mare basalts begin crystallizing at silica activities insufficient for orthopyroxene saturation; in contrast to terrestrial lavas, silica activities rise substantially with crystallization and cause silica saturation in the residuum. Igneous rocks of the highland regions have relatively higher initial silica activities than mare basalts. Thermodynamic calculations indicate that high-titanium mare basalts could be derived from a 90 to 240-km deep source region containing olivine and orthopyroxene in addition to other phases.

  3. [Exposure to crystalline silica in the air during renovation of residential buildings].

    PubMed

    Cavariani, F; Bedini, L; De Rossi, M; Papandrea, F; Carai, A; Cacchioli, G

    2006-01-01

    Exposure to respirable cristalline silica dust during construction activities can cause silicosis and, in accordance with International Agency for Research on Cancer (IARC), even lung cancer. Among the different facets of construction, residential buildings are of particular interest because the lack of exposure data for workers employed. In this sector a dry sand-blasting of brick ceiling and renewal activities has been investigated. The survey has been carried out in a civil dwelling and 58 samples have been collected using the SKC aluminium cyclone and Door-Oliver plastic cyclone at flow-rate 2.2-1.7 l/min. The respirable dust samples were analysed by x-ray diffraction using NIOSH Method 7500. Even if the results of this study should be considered preliminary, they showed SLC respirable concentrations even many time above TLV-TWA during a sand-blasting activities and some times also during the other activities. Awaiting the correct classification from European Community, it would be desiderable that the workers would had appropriate information and prevention on the specific risks associated to the dust in the construction activities.

  4. Special Education Reevaluation Procedures: Individuals with Disabilities Education Act (IDEA). Legal Requirements. Practical Applications. A Technical Assistance Paper

    ERIC Educational Resources Information Center

    Copenhaver, John

    2004-01-01

    This document provides an overview of the best practices and legal requirements regarding the reevaluation procedures under the IDEA to make the process more relevant for IEP teams as they approach this issue. Sections include: (1) Authority; (2) Questions/Answers; (3) Reevaluation Process; (4) Individualized Reevaluation Plan; (5) Summary…

  5. 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.

  6. Silica Fillers for elastomer Reinforement

    SciTech Connect

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

    2009-08-26

    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.

  7. Electrochemically Formed Porous Silica

    PubMed Central

    Chazalviel, Jean-Noël; Ozanam, François

    2011-01-01

    Controlled electrochemical formation of porous silica can be realized in dilute aqueous, neutral-pH, fluoride medium. Formation of a porous film is initiated by sweeping the potential applied to silicon to values higher than 20 V. Film formation, reaching a steady state, may be pursued in a wide range of potentials, including lower potentials. The origin of a threshold potential for porous film initiation has been explained quantitatively. All of the films appear mesoporous. Films grown at high potentials exhibit a variety of macrostructures superimposed on the mesoporosity. These macrostructures result from selective dissolution of silica induced by local pH lowering due to oxygen evolution. Films grown at potentials lower than 15 V appear uniform on the micrometer scale. However, all of the films also exhibit a stratified structure on the scale of a few tens of nanometres. This periodic structure can be traced back to the oscillatory behavior observed during the electrochemical dissolution of silicon in fluoride medium. It suggests that periodic breaking of the growing film may be responsible for this morphology. PMID:28879953

  8. Postshock temperatures in silica

    SciTech Connect

    Boslough, M.B.

    1988-06-10

    Experimental postshock temperatures for crystalline quartz released from shock states between 86 and 127 GPa and for fuset silica released from 59 to 73 GPa have been determined using previously measured spectral radiance data. The temperatures range from 3660 to 4150 K and are consistent with the interpretation based on shock temperature measurements, that the Hugoniot of SiO/sub 2/ crosses the phase boundary between stishovite and liquid. The new postshock temperatures were used to determine the Grueneisen parameter of liquid silica at high pressures and temperatures and the specific volume of the release state (..gamma../V = 3.5 Mg/m/sup 3/ and F/sub r/ = 0.266 m/sup 3//Mg, respectively), although there is some ambiguity as to whether this volume corresponds to a partial or total release state. To show the validity of these postshock temperatures, a radiative transport model was extended to times after free surface arrival of the shock wave. copyright American Geophysical Union 1988

  9. Peptide -- Silica Hybrid Networks

    NASA Astrophysics Data System (ADS)

    Altunbas, Aysegul; Sharma, Nikhil; Nagarkar, Radhika; Schneider, Joel; Pochan, Darrin

    2010-03-01

    In this study, a bio-inspired route was used to fabricate scaffolds that display hierarchical organization of an inorganic layer around an organic self-assembled peptide fibril template. The 20 amino acid peptide used in this study intramolecular folds into a beta-hairpin conformation on addition of a desired solution stimulus. This intramolecular folding is followed by intermolecular self-assembly of the peptides into a three dimensional network of entangled fibrils rich in beta-sheet with a high density of lysine groups exposed on the fibril-surfaces. The lysine-rich surface chemistry was utilized to create a silica shell around the fibrils. The mineralization process of the fibrils results in a rigid, porous silica network that retains the microscale and nanoscale structure of the peptide fibril network. Structural characterization via Transmission Electron Microscopy, cryogenic-Scanning Electron Microscopy, mechanical characterization via oscillatory rheology, Small Angle X-ray and Neutron Scattering of the silicified hydrogels will be presented.

  10. Mechanism of silica deposition in sorghum silica cells.

    PubMed

    Kumar, Santosh; Milstein, Yonat; Brami, Yaniv; Elbaum, Michael; Elbaum, Rivka

    2017-01-01

    Grasses take up silicic acid from soil and deposit it in their leaves as solid silica. This mineral, comprising 1-10% of the grass dry weight, improves plants' tolerance to various stresses. The mechanisms promoting stress tolerance are mostly unknown, and even the mineralization process is poorly understood. To study leaf mineralization in sorghum (Sorghum bicolor), we followed silica deposition in epidermal silica cells by in situ charring and air-scanning electron microscopy. Our findings were correlated to the viability of silica cells tested by fluorescein diacetate staining. We compared our results to a sorghum mutant defective in root uptake of silicic acid. We showed that the leaf silicification in these plants is intact by detecting normal mineralization in leaves exposed to silicic acid. Silica cells were viable while condensing silicic acid into silica. The controlled mineral deposition was independent of water evapotranspiration. Fluorescence recovery after photobleaching suggested that the forming mineral conformed to the cellulosic cell wall, leaving the cytoplasm well connected to neighboring cells. As the silicified wall thickened, the functional cytoplasm shrunk into a very small space. These results imply that leaf silica deposition is an active, physiologically regulated process as opposed to a simple precipitation. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  11. 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

  12. 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.

  13. 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.

  14. Reevaluation of the quondam dust trend in the middle atmosphere.

    PubMed

    Kocifaj, Miroslav; Horvath, Helmuth

    2005-12-01

    Quondam lunar eclipse photometry data offered valuable information on the optical properties of the middle atmosphere, including dust particles. However, in comparison with nonspherical grains, the simple model of spherical particles has a different effect on solar radiation penetrating horizontally through the atmosphere. It is shown that the systems, in which the smallest size fraction of dust particles dominates, reduce irradiation of the Earth's shadow more efficiently if the grains are of irregular shape. In contrast, the populations contaminated by a certain amount of large particles cause an opposite effect. Depending on the actual form of the size distribution function of the irregular grains, the irradiance within the center of the Earth's shadow may change by 2 orders of magnitude in the visible spectrum. It is therefore evident that dust properties retrieved in the past are eligible candidates for reevaluation to correct a view on the dust trend in the middle atmosphere. Sample calculations are presented for the lunar eclipse observed on 19 January 1954.

  15. 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.

  16. Reevaluation of the significance of sequence information for speech recognition

    NASA Astrophysics Data System (ADS)

    Sarukkai, Ramesh R.; Ballard, Dana H.

    1994-12-01

    A central difficulty with automatic speech recognition is the temporally inaccurate nature of the speech signal. Despite this, speech has been traditionally modeled as a purely sequential (albeit probabilistic) process. The usefulness of accurate sequence information is reevaluated in this paper, both at the acoustic and lexical levels for the task of speech recognition. At the acoustic level, speech segments are quantized into discrete vectors, and converted into set representations as opposed to accurate sequences. Recognition of the quantized vector sets dramatically improved performance as contrasted with the corresponding vector sequence representations. At the lexical level, our study suggests that accurate sequence information is, again, not crucial. In fact locally discarding phoneme sequence information may be useful for coping with errors (such as insertion, substitution). Based on the idea of phone set indexing, a lexical access algorithm is developed. Thus, this work questions the traditional approach of modeling speech as a purely sequential process, and suggests that discarding local sequential information may be a good idea. As an alternative to a purely sequential representation, a set representation seems to be a viable option.

  17. 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.

  18. Does calorie restriction induce mitochondrial biogenesis? A reevaluation

    PubMed Central

    Hancock, Chad R.; Han, Dong-Ho; Higashida, Kazuhiko; Kim, Sang Hyun; Holloszy, John O.

    2011-01-01

    It has been reported that 30% calorie restriction (CR) for 3 mo results in large increases in mitochondrial biogenesis in heart, brain, liver, and adipose tissue, with concomitant increases in respiration and ATP synthesis. We found these results surprising, and performed this study to determine whether 30% CR does induce an increase in mitochondria in heart, brain, liver, adipose tissue, and/or skeletal muscle. To this end, we measured the levels of a range of mitochondrial proteins, and mRNAs. With the exception of long-chain acyl-CoA dehydrogenase protein level, which was increased ∼60% in adipose tissue, none of the mitochondrial proteins or mRNAs that we measured were increased in rats subjected to 30% CR for 14 wk. There was also no increase in citrate synthase activity. Because it is not possible to have an increase in mitochondria without any increase in key mitochondrial proteins, we conclude that 30% CR does not induce an increase in mitochondria in heart, brain, liver, adipose tissue, or skeletal muscle in laboratory rodents.—Hancock, C. R., Han, D.-H., Higashida, K., Kim, S. H., Holloszy, J. O. Does calorie restriction induce mitochondrial biogenesis? A reevaluation. PMID:21048043

  19. An empirical reevaluation of absolute pitch: behavioral and electrophysiological measurements.

    PubMed

    Elmer, Stefan; Sollberger, Silja; Meyer, Martin; Jäncke, Lutz

    2013-10-01

    Here, we reevaluated the "two-component" model of absolute pitch (AP) by combining behavioral and electrophysiological measurements. This specific model postulates that AP is driven by a perceptual encoding ability (i.e., pitch memory) plus an associative memory component (i.e., pitch labeling). To test these predictions, during EEG measurements AP and non-AP (NAP) musicians were passively exposed to piano tones (first component of the model) and additionally instructed to judge whether combinations of tones and labels were conceptually associated or not (second component of the model). Auditory-evoked N1/P2 potentials did not reveal differences between the two groups, thus indicating that AP is not necessarily driven by a differential pitch encoding ability at the processing level of the auditory cortex. Otherwise, AP musicians performed the conceptual association task with an order of magnitude better accuracy and shorter RTs than NAP musicians did, this result clearly pointing to distinctive conceptual associations in AP possessors. Most notably, this behavioral superiority was reflected by an increased N400 effect and accompanied by a subsequent late positive component, the latter not being distinguishable in NAP musicians.

  20. 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.

  1. 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.

  2. Contacts in the Office of Pesticide Programs, Pesticide Re-Evaluation Division

    EPA Pesticide Factsheets

    Contact the Pesticide Re-Evaluation Division (PRD) about registration review and reregistration follow up (including post-RED activities, product reregistration, and implementing certain tolerance reassessment decisions) for conventional pesticides.

  3. 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

    ... Environmental Impact Statement (EIS) has been prepared for Sikorsky Memorial Airport in Stratford, Connecticut... Federal Aviation Administration Draft Re-Evaluation for Environmental Impact Statement: Sikorsky Memorial Airport, Stratford, CT AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of...

  4. 76 FR 42762 - Final Written Re-Evaluation for Environmental Impact Statement: Sikorsky Memorial Airport...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-19

    ... Final Environmental Impact Statement (FEIS) has been completed for Sikorsky Memorial Airport in... Federal Aviation Administration Final Written Re-Evaluation for Environmental Impact Statement: Sikorsky Memorial Airport, Stratford, CT AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice...

  5. 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

    ... From the Federal Register Online via the Government Publishing Office ENVIRONMENTAL PROTECTION AGENCY Stakeholder Meeting Regarding Re-Evaluation of Currently Approved Total Coliform Analytical...) analytical methods. At these meetings, stakeholders will be given an opportunity to discuss potential...

  6. Silica heat shield sizing

    NASA Technical Reports Server (NTRS)

    Ebbesmeyer, L. H.; Christensen, H. E.

    1975-01-01

    The sensitivity of silica heat shield requirements to gap width, tile edge radius, and heat transfer distribution within tile gaps was investigated. A two-dimensional thermal model was modified and used to determine the effect of two dimensional heat transfer distributions at high temperature reusable surface insulation edges on shuttle thermal protection system (TPS) requirements. The sensitivity of TPS requirements to coating thickness, emissivity, substructure thickness, and changes in gap heating for several locations on shuttle was also studied. An inverse solution technique was applied to temperature data obtained in the Ames 20 MW turbulent duct in order to examine the effect of tile edge radius on TPS requirements. The derived heating values were then used to predict TPS requirements. Results show that increasing tile radius reduces TPS requirements.

  7. Mechanism of mechanical fatigue of fused silica

    SciTech Connect

    Tomozawa, M.

    1992-01-01

    This report discusses work on the fatigue of fused silica. Topics covered include: the effect of residual water in silica glass on static fatigue; strengthening of abraded silica glass by hydrothermal treatment; fatigue-resistant coating of silicon oxide glass; and water entry into silica glass during slow crack growth.

  8. 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

  9. 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.

  10. Reevaluating assembly evaluations with feature response curves: GAGE and assemblathons.

    PubMed

    Vezzi, Francesco; Narzisi, Giuseppe; Mishra, Bud

    2012-01-01

    In just the last decade, a multitude of bio-technologies and software pipelines have emerged to revolutionize genomics. To further their central goal, they aim to accelerate and improve the quality of de novo whole-genome assembly starting from short DNA sequences/reads. However, the performance of each of these tools is contingent on the length and quality of the sequencing data, the structure and complexity of the genome sequence, and the resolution and quality of long-range information. Furthermore, in the absence of any metric that captures the most fundamental "features" of a high-quality assembly, there is no obvious recipe for users to select the most desirable assembler/assembly. This situation has prompted the scientific community to rely on crowd-sourcing through international competitions, such as Assemblathons or GAGE, with the intention of identifying the best assembler(s) and their features. Somewhat circuitously, the only available approach to gauge de novo assemblies and assemblers relies solely on the availability of a high-quality fully assembled reference genome sequence. Still worse, reference-guided evaluations are often both difficult to analyze, leading to conclusions that are difficult to interpret. In this paper, we circumvent many of these issues by relying upon a tool, dubbed [Formula: see text], which is capable of evaluating de novo assemblies from the read-layouts even when no reference exists. We extend the FRCurve approach to cases where lay-out information may have been obscured, as is true in many deBruijn-graph-based algorithms. As a by-product, FRCurve now expands its applicability to a much wider class of assemblers - thus, identifying higher-quality members of this group, their inter-relations as well as sensitivity to carefully selected features, with or without the support of a reference sequence or layout for the reads. The paper concludes by reevaluating several recently conducted assembly competitions and the datasets that

  11. Paclitaxel suppresses collagen-induced arthritis: a reevaluation

    PubMed Central

    Zhao, Yi; Chang, Zhi-Fang; Li, Ru; Li, Zhan-Guo; Li, Xiao-Xia; Li, Lin

    2016-01-01

    Objective: To reevaluate the suppressive effect of paclitaxel (PTX) liposome on collagen-induced arthritis (CIA) in rats and explore its mechanisms. Methods: Female Lewis rats were immunized with bovine type II collagen (CII) to induce arthritis. The rats with CIA were randomly divided into three groups: 5% GS control group, 2.5 mg/kg PTX treatment group and 1 mg/kg methotrexate (MTX) positive control group. The drugs were administered by intraperitoneal injection on the second day after arthritis onset. The body weights, arthritis scores and paw volumes were observed consecutively. The ankle joints of rats were collected for X-ray examination and histological evaluation. Serum samples were collected to test the levels of anti-CII antibodies and cytokines. Results: Body weights were not significantly affected after PTX or MTX treatments (p>0.05). Compared with 5% GS control or MTX treatment groups, PTX group showed significant decrease of arthritis scores and paw volumes (p<0.05). Radiographic and histologic evaluation provided evidence that rats with PTX treatment had less synovial proliferation and bone erosion. In addition, the levels of anti-CII antibodies as well as serum tumor necrosis factor (TNF)-α and vascular endothelial growth factor (VEGF) levels were remarkably lower in PTX group than those in 5% GS controls (p<0.05). Conclusions: PTX inhibits the progression of CIA in rats and prevents the destruction of joints. The mechanism might be related to its inhibition on the levels of serum anti-CII antibodies, TNF-α and VEGF. PMID:27904705

  12. 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

  13. Reevaluation of the Pavlov ratio in patients with cervical myelopathy.

    PubMed

    Suk, Kyung-Soo; Kim, Ki-Tack; Lee, Jung-Hee; Lee, Sang-Hun; Kim, Jin-Soo; Kim, Jin-Young

    2009-03-01

    This study was designed to reevaluate the effectiveness of the Pavlov ratio in patients with cervical myelopathy. We studied 107 patients who underwent open door laminoplasty for the treatment of cervical myelopathy between the C3 to C7 levels. We determined the Pavlov ratio on preoperative and postoperative cervical spine lateral radiographs, the vertebral body-to-canal ratio on sagittal reconstruction CT scans, and the vertebral body-to-cerebrospinal fluid (CSF) column ratio on T2-weighted sagittal MR images from C3 to C6. The severity of myelopathy was determined using the JOA score on both preoperative and postoperative images. The recovery rate was also calculated. The Pavlov ratio in plain radiographs from patients with myelopathy was compared with the ratio of the vertebral body to the spinal canal on CT and MRI. The average Pavlov ratio between C3 and C6 ranged from 0.71 to 0.76. On CT scan, the average vertebral body-to-canal ratio between C3 and C6 ranged from 0.62 to 0.66. On MRI, the vertebral body-to-CSF column ratio between C3 and C6 ranged between 0.53 and 0.57. A positive correlation was noted between the Pavlov ratio and the vertebral body-to-canal ratio on sagittal-reconstruction CT (correlation coefficient = 0.497-0.627, p = 0.000) and between the Pavlov ratio and the vertebral body-to-CSF column ratio on MRI (correlation coefficient = 0.511-0.649, p = 0.000). We demonstrated a good correlation between the Pavlov ratio and both the vertebral body-to-canal ratio on CT and the vertebral body-to-CSF column ratio on MRI. Therefore, the Pavlov ratio can be relied upon to predict narrowing of the cervical spinal canal in the sagittal plane.

  14. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Silica-supported biomimetic membranes.

    PubMed

    Ariga, Katsuhiko

    2004-01-01

    The hybridization of lipid membranes with inorganic silica-based framework results in mechanically stable biomembrane mimics. This account describes three types of silica-based biomimetic membranes. As the first example, a Langmuir monolayer of dialkylalkoxysilane was polymerized and immobilized onto a porous glass plate. Permeability through the monolayer-immobilized glass was regulated by phase transition of the immobilized monolayer. In the second example, spherical vesicles covalently attached to a silica cover layer (Cerasome) were prepared. The Cerasome was stable enough to be assembled into layer-by-layer films without destruction of its vesicular structure. This material could be an example of the multicellular assembly. Mesoporous silica films densely filling peptide assemblies (Proteosilica) are introduced as the third example. The Proteosilica was synthesized as a transparent film through template sol-gel reaction using amphiphilic peptides.

  16. Reevaluation of Friedman's Labor Curve: a pilot study.

    PubMed

    Cesario, Sandra K

    2004-01-01

    To reevaluate the average length of each phase/stage of labor for multiparous and primiparous women in North America who received no regional anesthesia or oxytocin augmentation or induction, to describe a range of labor lengths associated with good childbirth outcomes, and to determine if there is a consensus among labor and delivery nurse managers responding to the survey regarding the need to revise Friedman's Labor Curve. This pilot study used a descriptive and anonymous cross-sectional survey design. Surveys were mailed to 500 maternity care agencies in the United States, Canada, and Mexico with a return rate of 17.8% (n = 89). Each participating agency was asked to submit five patient cases to be included in the analysis. The sample of patient cases (n = 419) was drawn from randomly selected maternity care agencies throughout North America representing all sizes of agencies and geographic locations. The cases submitted for analysis represented women 14 to 44 years of age with varying ethnicities who received no regional anesthesia or oxytocin augmentation or induction. Twenty-three percent of the women in the sample (n = 97) were primigravidas. The average length of labor for primiparous and multiparous women today is similar to the average length of labor described by Friedman in 1954. However, a wider range of "normal" was found in cases included in the current study. Primiparous women remained in the first stage of labor for up to 26 hours and the second stage of labor up to 8 hours with no adverse effects to mother or infant. Multiparous women remained in the first stage of labor for up to 23 hours and the second stage of labor for up to 4.5 hours with good birth outcomes. In addition, 87.6% of nurse managers responding to the survey believed that Friedman's Labor Curve should be revised to meet the needs of current patient populations, technological advances, and nursing responsibilities. This study suggests that the parameters to determine if a labor is

  17. 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.

  18. Precipitated silica as flow regulator.

    PubMed

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

    2008-08-07

    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.

  19. Infrared spectra of silica polymorphs

    NASA Astrophysics Data System (ADS)

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

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

  20. Pumping Iron and Silica Bodybuilding

    NASA Astrophysics Data System (ADS)

    Mcnair, H.; Brzezinski, M. A.; Krause, J. W.; Parker, C.; Brown, M.; Coale, T.; Bruland, K. W.

    2016-02-01

    The availability of dissolved iron influences the stoichiometry of nutrient uptake by diatoms. Under nutrient replete conditions diatoms consume silicic acid and nitrate in a 1:1 ratio, this ratio increases under iron stress. Using the tracers 32Si and PDMPO, the total community and group-specific silica production rates were measured along a gradient of dissolved iron in an upwelling plume off the California coast. At each station, a control (ambient silicic acid) and +20 µM silicic acid treatment were conducted with each tracer to determine whether silicic acid limitation controlled the rate of silica production. Dissolved iron was 1.3 nmol kg-1 nearshore and decreased to 0.15 nmol kg-1 offshore. Silicic acid decreased more rapidly than nitrate, it was nearly 9 µM higher in the nearshore and 7 µM lower than nitrate in the middle of the transect where the iron concentration had decreased. The rate of diatom silica production decreased in tandem with silicic acid concentration, and silica production limitation by low silicic acid was most pronounced when iron concentrations were >0.4 nmol kg-1. The composition of the diatom assemblage shifted from Chaetoceros spp. dominated nearshore to a more sparse pennate-dominated assemblage offshore. Changes in taxa-specific silica production rates will be reported based on examination of PDMPO labeled cells using confocal microscopy.

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

    PubMed

    Radnoff, Diane L; Kutz, Michelle K

    2014-01-01

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

  2. [Discussion on development of four diagnostic information scale for clinical re-evaluation of postmarketing herbs].

    PubMed

    He, Wei; Xie, Yanming; Wang, Yongyan

    2011-12-01

    Post-marketing re-evaluation of Chinese herbs can well reflect Chinese medicine characteristics, which is the most easily overlooked the clinical re-evaluation content. Since little attention has been paid to this, study on the clinical trial design method was lost. It is difficult to improving the effectiveness and safety of traditional Chinese medicine. Therefore, more attention should be paid on re-evaluation of the clinical trial design method point about tcm syndrome such as the type of research program design, the study of Chinese medical information collection scale and statistical analysis methods, so as to improve the clinical trial design method study about tcm syndrome of Chinese herbs postmarketing re-evalutation status.

  3. Mesoporous silica templated zirconia nanoparticles

    NASA Astrophysics Data System (ADS)

    Ballem, Mohamed A.; Córdoba, José M.; Odén, Magnus

    2011-07-01

    Nanoparticles of zirconium oxide (ZrO2) were synthesized by infiltration of a zirconia precursor (ZrOCl2·8H2O) into a SBA-15 mesoporous silica mold using a wet-impregnation technique. X-ray diffractometry and high-resolution transmission electron microscopy show formation of stable ZrO2 nanoparticles inside the silica pores after a thermal treatment at 550 °C. Subsequent leaching out of the silica template by NaOH resulted in well-dispersed ZrO2 nanoparticles with an average diameter of 4 nm. The formed single crystal nanoparticles are faceted with 110 surfaces termination suggesting it to be the preferred growth orientation. A growth model of these nanoparticles is also suggested.

  4. Living bacteria in silica gels

    NASA Astrophysics Data System (ADS)

    Nassif, Nadine; Bouvet, Odile; Noelle Rager, Marie; Roux, Cécile; Coradin, Thibaud; Livage, Jacques

    2002-09-01

    The encapsulation of enzymes within silica gels has been extensively studied during the past decade for the design of biosensors and bioreactors. Yeast spores and bacteria have also been recently immobilized within silica gels where they retain their enzymatic activity, but the problem of the long-term viability of whole cells in an inorganic matrix has never been fully addressed. It is a real challenge for the development of sol-gel processes. Generic tests have been performed to check the viability of Escherichia coli bacteria in silica gels. Surprisingly, more bacteria remain culturable in the gel than in an aqueous suspension. The metabolic activity of the bacteria towards glycolysis decreases slowly, but half of the bacteria are still viable after one month. When confined within a mineral environment, bacteria do not form colonies. The exchange of chemical signals between isolated bacteria rather than aggregates can then be studied, a point that could be very important for 'quorum sensing'.

  5. 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.

  6. Re-evaluating possibilities of the Source Scanning Algorithm

    NASA Astrophysics Data System (ADS)

    Jansky, J.; Plicka, V.; Zahradnik, J.

    2012-04-01

    The Source Scanning Algorithm (SSA) has been introduced and developed by Hann Kao, Shao-Ju Shan and co-workers since 2004. The basic idea of SSA is simple: Seismograms in a station network can be stacked, using theoretical arrival times in a given (e.g. 3D) structural model and an assumed point source. A set of trial source positions is grid searched, and the most likely positions are those producing the largest correlation (so-called brightness). The method may work fully automatically without any manual or automatic phase picking. It can be used for events with unclear arrivals; as such it is a powerful tool to locate tremors, including their continuous monitoring. Source complexity (multiple events) can be studied and perhaps even the causative fault planes can be identified. Nevertheless, many questions related to the application of the method remain still open. Some of them are as follows: (i) Is the method competitive in comparison with standard location methods of individual events whose phase arrivals are clear? (ii) How accurate must be the structural model in which the theoretical arrival times are calculated? (iii) How to combine data from local and near regional seismic stations? We report preliminary results from a small project designed to critically re-evaluate possibilities and limitations of the SSA method. Our analysis is focused on the Efpalio 2010, Mw~5 earthquake, Corinth Gulf, Greece (Sokos et al., in press), which we previously located by a number of different methods. We use the same source-station configuration as in the real case, but invert synthetic seismograms, calculated for a 1-sec and 0.2-sec source pulse by the discrete-wavenumber method in 1D crustal models. Theoretical travel times are calculated by the ray method, including head waves from all model discontinuities (intra-crustal ones and Moho). Both the double-couple and isotropic sources are considered. We demonstrate the Lat-Lon brightness maps for varying trial source depths

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 77 FR 43143 - Limitation on Claims for Judicial Review; Re-Evaluation With Respect to the Willits Bypass...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-23

    ...-evaluations were prepared in order to determine whether a supplemental Environmental Impact Statement (SEIS... INFORMATION: Caltrans conducted two Re-evaluations of the Final Environmental Impact Statement (FEIS) issued... properties, and land use. The purpose of the Re-evaluations was to examine potential environmental...

  15. Hydrodynamically mediated macrophyte silica dynamics.

    PubMed

    Schoelynck, J; Bal, K; Puijalon, S; Meire, P; Struyf, E

    2012-11-01

    In most aquatic ecosystems, hydrodynamic conditions are a key abiotic factor determining species distributions and abundance of aquatic plants. Resisting stress and keeping an upright position often relies on investment in tissue reinforcement, which is costly to produce. Silica could provide a more economical alternative. Two laboratory experiments were conducted to measure the response of two submerged species, Egeria densa Planch. and Limnophila heterophylla (Roxb.) Benth., to dissolved silicic acid availability and exposure to hydrodynamic stress. The results were verified with a third species in a field study (Nuphar lutea (L.) Smith). Biogenic silica (BSi) concentration in both stems and leaves increases with increasing dissolved silica availability but also with the presence of hydrodynamic stress. We suggest that the inclusion of extra silica enables the plant to alternatively invest its energy in the production of lignin and cellulose. Although we found no significant effects of hydrodynamic stress on cellulose or lignin concentrations either in the laboratory or in the field, BSi was negatively correlated with cellulose concentration and positively correlated with lignin concentration in samples collected in the field study. This implies that the plant might perform with equal energy efficiency in both standing and running water environments. This could provide submerged species with a tool to respond to abiotic factors, to adapt to new ecological conditions and hence potentially colonise new environments. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

  16. High-Silica Lamoose Rock

    NASA Image and Video Library

    2015-07-23

    A rock fragment dubbed "Lamoose" is shown in this picture taken by the Mars Hand Lens Imager (MAHLI) on NASA's Curiosity rover. Like other nearby rocks in a portion of the "Marias Pass" area of Mt. Sharp, Mars, it has unusually high concentrations of silica. The high silica was first detected in the area by the Chemistry & Camera (ChemCam) laser spectrometer. This rock was targeted for follow-up study by the MAHLI and the arm-mounted Alpha Particle X-ray Spectrometer (APXS). Silica is a rock-forming compound containing silicon and oxygen, commonly found on Earth as quartz. High levels of silica could indicate ideal conditions for preserving ancient organic material, if present, so the science team wants to take a closer look. The rock is about 4 inches (10 centimeters) across. It is fine-grained, perhaps finely layered, and etched by the wind. The image was taken on the 1,041st Martian day, or sol, of the mission (July 11, 2015). MAHLI was built by Malin Space Science Systems, San Diego. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington. JPL designed and built the project's Curiosity rover. http://photojournal.jpl.nasa.gov/catalog/PIA19828

  17. 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

  18. 12 CFR 1310, Appo. A - Council reevaluation and rescission of determinations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...), as applicable. (b) Notice of reevaluation; submission of materials. The Council shall provide written... nonbank financial company an opportunity to submit written materials, within such time as the Council... financial company of such notice), to the Council to contest the determination, including materials...

  19. Psychometric Reevaluation of the Scientific Attitude Inventory-Revised (SAI-II)

    ERIC Educational Resources Information Center

    Lichtenstein, Michael J.; Owen, Steven V.; Blalock, Cheryl L.; Liu, Yan; Ramirez, Kacy A.; Pruski, Linda A.; Marshall, Carolyn E.; Toepperwein, Mary Anne

    2008-01-01

    The central purposes of this study were to review the development and evolution of the Scientific Attitude Inventory (SAI) and then reevaluate the psychometric properties of the revised form of the SAI, the Scientific Attitude Inventory II (SAI-II). The SAI-II was administered to a convenience sample of 543 middle and high school students from…

  20. 12 CFR 560.172 - Re-evaluation of real estate owned.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 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 the... under the particular circumstances. The foregoing requirement shall not apply to any parcel of...

  1. Emotional Dissonance and Burnout: The Moderating Role of Team Reflexivity and Re-Evaluation.

    PubMed

    Andela, Marie; Truchot, Didier

    2017-08-01

    The aim of the present study was to better understand the relationship between emotional dissonance and burnout by exploring the buffering effects of re-evaluation and team reflexivity. The study was conducted with a sample of 445 nurses and healthcare assistants from a general hospital. Team reflexivity was evaluated with the validation of the French version of the team reflexivity scale (Facchin, Tschan, Gurtner, Cohen, & Dupuis, 2006). Burnout was measured with the MBI General Survey (Schaufeli, Leiter, Maslach, & Jackson, 1996). Emotional dissonance and re-evaluation were measured with the scale developed by Andela, Truchot, & Borteyrou (2015). With reference to Rimé's theoretical model (2009), we suggested that both dimensions of team reflexivity (task and social reflexivity) respond to both psychological necessities induced by dissonance (cognitive clarification and socio-affective necessities). Firstly, results indicated that emotional dissonance was related to burnout. Secondly, regression analysis confirmed the buffering role of re-evaluation and social reflexivity on the emotional exhaustion of emotional dissonance. Overall, results contribute to the literature by highlighting the moderating effect of re-evaluation and team reflexivity in analysing the relationship between emotional dissonance and burnout. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  2. 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…

  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. Factors Associated with Reevaluation of the Stepwise Excavation Procedure: An 8-Year Retrospective Study.

    PubMed

    Ortega-Verdugo, Paula; Guzmán-Armstrong, Sandra; Cobb, Deborah; Dawson, Deborah V; Blanchette, Derek; Kolker, Justine L; Hernández, Marcela; Warren, J J

    2016-01-01

    Although the stepwise excavation procedure (SWP) has been shown to be an effective caries treatment technique, studies reporting its application outside of controlled clinical trials are limited. We performed a retrospective study from patient record data to assess the proportion of patients who had an SWP reevaluated within 18 months at The University of Iowa College of Dentistry (UICOD) between 2004 and 2012, and evaluated the association between different variables and this outcome. A total of 1,985 SWPs were performed in 1,326 patients, with 518 patients having had reevaluation within 18 months. Bivariate analysis and logistic regression modeling revealed strong associations between explanatory variables such as provider type, tooth type, patient age, number of recalls and the calendar year in which the SWP was done and reevaluation status. There was also evidence of association with dental insurance status. Other characteristics such as gender, distance traveled to the UICOD, number of surfaces treated and tooth arch did not show any significant association. In general, patients were more likely to have reevaluation when seen by faculty members or residents, the procedure was performed in molars/pre-molars, they were older, they had more recalls and were seen earlier in the study period. These results suggest that decisions to use SWP should consider patient demographics and treatment characteristics such as provider level, tooth type, patient age and number of recalls. The impact of treatment year may reflect program heterogeneity or temporal changes in external societal factors.

  5. 24 CFR 58.47 - Re-evaluation of environmental assessments and other environmental findings.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... EA or an EIS if its evaluation indicates potentially significant impacts. (3) Where the recipient is... assessments and other environmental findings. 58.47 Section 58.47 Housing and Urban Development Office of the....47 Re-evaluation of environmental assessments and other environmental findings. (a) A responsible...

  6. 24 CFR 58.47 - Re-evaluation of environmental assessments and other environmental findings.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... EA or an EIS if its evaluation indicates potentially significant impacts. (3) Where the recipient is... assessments and other environmental findings. 58.47 Section 58.47 Housing and Urban Development Office of the....47 Re-evaluation of environmental assessments and other environmental findings. (a) A responsible...

  7. 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…

  8. 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…

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

    Code of Federal Regulations, 2010 CFR

    2010-07-01

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

  10. 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…

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

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... evaluation (if appropriate) and as part of any reevaluation under this part, the IEP Team and other qualified... the measurable annual goals set out in the IEP of the child and to participate, as appropriate, in the...) of this section. (d) Requirements if additional data are not needed. (1) If the IEP Team and other...

  12. 34 CFR 300.305 - Additional requirements for evaluations and reevaluations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... evaluation (if appropriate) and as part of any reevaluation under this part, the IEP Team and other qualified... the measurable annual goals set out in the IEP of the child and to participate, as appropriate, in the...) of this section. (d) Requirements if additional data are not needed. (1) If the IEP Team and other...

  13. 34 CFR 300.305 - Additional requirements for evaluations and reevaluations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... evaluation (if appropriate) and as part of any reevaluation under this part, the IEP Team and other qualified... the measurable annual goals set out in the IEP of the child and to participate, as appropriate, in the...) of this section. (d) Requirements if additional data are not needed. (1) If the IEP Team and other...

  14. 34 CFR 300.305 - Additional requirements for evaluations and reevaluations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... evaluation (if appropriate) and as part of any reevaluation under this part, the IEP Team and other qualified... the measurable annual goals set out in the IEP of the child and to participate, as appropriate, in the...) of this section. (d) Requirements if additional data are not needed. (1) If the IEP Team and other...

  15. 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…

  16. 24 CFR 58.47 - Re-evaluation of environmental assessments and other environmental findings.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... assessments and other environmental findings. 58.47 Section 58.47 Housing and Urban Development Office of the... HUD ENVIRONMENTAL RESPONSIBILITIES Environmental Review Process: Environmental Assessments (EA's) § 58.47 Re-evaluation of environmental assessments and other environmental findings. (a) A responsible...

  17. 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 between…

  18. Potential of silica bodies (phytoliths) for nanotechnology.

    PubMed

    Neethirajan, Suresh; Gordon, Richard; Wang, Lijun

    2009-08-01

    Many plant systems accumulate silica in solid form, creating intracellular or extracellular silica bodies (phytoliths) that are essential for growth, mechanical strength, rigidity, predator and fungal defence, stiffness and cooling. Silica is an inorganic amorphous oxide formed by polymerization processes within plants. There has been much research to gain new insights into its biochemistry and to mimic biosilicification. We review the background on plant silica bodies, silica uptake mechanisms and applications, and suggest possible ways of producing plant silica bodies with new functions. Silica bodies offer complementary properties to diatoms for nanotechnology, including large-scale availability from crop wastes, lack of organic impurities (in some), microencapsulation and microcrystalline quartz with possibly unique optical properties.

  19. Superhydrophobicity of silica nanoparticles modified with polystyrene

    NASA Astrophysics Data System (ADS)

    Sun, X. L.; Fan, Z. P.; Zhang, L. D.; Wang, L.; Wei, Z. J.; Wang, X. Q.; Liu, W. L.

    2011-01-01

    Polystyrene/silica nanoparticles were prepared by radical polymerization of silica nanoparticles possessing vinyl groups and styrene with benzoyl peroxide. The resulting vinyl silica nanoparticles, polystyrene/silica nanoparticles were characterized by means of Fourier transformation infrared spectroscopy, scanning electron microscopy and UV-vis absorption spectroscopy. The results indicated that polystyrene had been successfully grafted onto vinyl silica nanoparticles via covalent bond. The morphological structure of polystyrene/silica nanoparticles film, investigated by scanning electron microscopy, showed a characteristic rough structure. Surface wetting properties of the polystyrene/silica nanoparticles film were evaluated by measuring water contact angle and the sliding angle using a contact angle goniometer, which were measured to be 159° and 2°, respectively. The excellent superhydrophobic property enlarges potential applications of the superhydrophobic surfaces.

  20. 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

  1. Organically modified silicas on metal nanowires.

    PubMed

    Dean, Stacey L; Stapleton, Joshua J; Keating, Christine D

    2010-09-21

    Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling.

  2. Organically Modified Silicas on Metal Nanowires

    PubMed Central

    2010-01-01

    Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling. PMID:20715881

  3. Silica-Immobilized Enzyme Reactors

    DTIC Science & Technology

    2007-08-01

    relief from the symptoms of inflammation and pain Silica-IMERs 10 and is the mode of action of drugs such as aspirin and ibuprofen .[61] Serotonin...supports and using the enantiomeric selectivity of the enzyme to resolve racemic mixtures.[100] Immobilization onto supports with various pore sizes and...activity (~37%) and used as a packed- bed IMER to catalyze the racemic resolution of (S)-ketoprofen from its constituent enantiomers . The optically pure (S

  4. Chemical substitution in silica polymorph

    NASA Technical Reports Server (NTRS)

    Smith, J. V.; Steele, I. M.

    1984-01-01

    Ion and electron probe analyses are presented for trace elements (Al, Na, K, Li, Ti) in quartz, tridymite, cristobalite and melanophlogite. Quartz and melanophlogite show low levels of trace elements relative to tridymite and cristobalite. The previously determined alpha-beta inversion temperature decreases as the Al content of quartz increases. For all silica polymorphs, Al is greater than or equal to Na + K + Li on an atom basis, with the excess Al probably balanced by H.

  5. Very deep fused silica etching

    NASA Astrophysics Data System (ADS)

    Steingoetter, Ingo; Grosse, Axel; Fouckhardt, Henning

    2003-01-01

    Fabrication processes for wet chemical and dry etching of hollow capillary leaky optical waveguides in high-purity fused silica for extended path cells for improved optical detection in analytical chemistry are described. We focus on microstructures with etch depths on the order of 80 μm. Special attention is paid to the preparation of the etch masks for the two different etch technologies. The fused silica wet chemical etching technique uses buffered hydrofluoric acid with ultrasonic agitation achieving etch rates > 100 nm/min. We succeeded in developing an etch process based on a single-layer photoresist (AZ 5214E, Clariant Corp.) soft mask, which gives excellent results due to special adhesion promotion and a photoresist hardening cycle after the developing step. This procedure allows for the production of channels of nearly semi-cylindrical profiles with etch depths of up to 87 μm. For the dry etch process a ~10 μm thick Ni layer is used as a hard mask realized with electroplating and a thick photoresist. The etch process is performed in an ECR (Electron Cyclotron Resonance) chamber using CF4 gas. The resulting etch rate for fused silica is about 138 nm/min. Etch depths of (accidentally also) 87 μm are achieved.

  6. 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

  7. 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.

  8. 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.

  9. 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.

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

    PubMed

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

    2014-07-01

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

  11. Weak silica nanomaterial-induced genotoxicity can be explained by indirect DNA damage as shown by the OGG1-modified comet assay and genomic analysis.

    PubMed

    Pfuhler, Stefan; Downs, Thomas R; Allemang, Ashley J; Shan, Yuching; Crosby, Meredith E

    2017-01-01

    In a previous study, 15-nm silica nanoparticles (NPs) caused small increases in DNA damage in liver as measured in the in vivo comet and micronucleus assays after intravenous administration to rats at their maximum tolerated dose, a worst-case exposure scenario. Histopathological examination supported a particle-induced, tissue damage-mediated inflammatory response. This study used a targeted approach to provide insight into the mode of action (MoA) by examining transcriptional regulation of genes in liver in a time and dose-dependent manner at 1, 2, 4, 8 and 24 h after intravenous administration of 15-nm silica NPs. DNA damage was assessed using the standard comet assay and hOGG1 glycosylase-modified comet assay that also measures oxidative DNA damage. Potassium bromate, an IARC Class 2B carcinogen that specifically operates via an oxidative stress MoA, was used as a positive control for the hOGG1 comet assay and gave a strong signal in its main target organ, the kidney, while showing less activity in liver. Treatment of rats with silica NPs at 50 mg/kg body weight (bw) caused small, statistically insignificant increases in DNA damage in liver measured by the standard comet assay, while a statistically significant increase was observed at 4 h with the hOGG1 comet assay, consistent with a MoA involving reactive oxygen species. Histopathology showed liver damage and neutrophil involvement while genomic analysis and response pattern of key genes involved in inflammation and oxidative stress supported a tissue damage-mediated inflammatory response involving the complement system for removing/phagocytising damaged cells. No changes were observed for histopathology or gene array for the low-dose (5 mg/kg bw) silica NPs. The results of this study confirm our hypothesis that the weak DNA damage observed by silica NPs occurs secondary to inflammation/immune response, indicating that a threshold can be applied in the risk assessment of these materials. © The Author 2016

  12. Sealed silica pressure ampoules for crystal growth

    NASA Technical Reports Server (NTRS)

    Holland, L. R.

    1984-01-01

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

  13. 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.

  14. Interaction between silica and hydrophobic cations.

    PubMed Central

    Depasse, J

    1978-01-01

    The interactions between silica and some molecules which have a high affinity for its surface have been studied. The hydrophobic properties and the positive charge of these molecules are likely to be responsible for their strong adsorption on to silica. These observations should be useful in research into new inhibitors of the effects of silica. One of the cations tested, chloroquine, has been shown to be an effective inhibitor of the haemolytic activity of quartz. PMID:204326

  15. Reevaluating the carcinogenicity of ortho-toluidine: a new conclusion and its implications.

    PubMed

    Sellers, C; Markowitz, S

    1992-12-01

    The aromatic amine ortho-toluidine has been recognized by IARC as an animal carcinogen for the past decade. Three recent epidemiological studies of worker populations have now implicated this chemical as a human bladder carcinogen. In a study by E. Ward, A. Carpenter, S. Markowitz, D. Roberts, and W. Halperin ((1991), J. Natl. Cancer Inst. 83, 501-506), workers definitely exposed to ortho-toluidine for at least 10 years experienced a Standardized Incidence Ratio (SIR) of 27.2 (90% CI = 11.8-53.7). The other major exposure was to aniline, which significant epidemiological studies have failed to confirm as a human carcinogen. In retrospect, studies by G. F. Rubino, G. Scansetti, G. Piolatto ((1982) Environ. Res. 27, 241-254) and M. J. Stasik ((1988) Int. Arch. Occup. Environ. Health 60, 21-24) also support the hypothesis that ortho-toluidine is a human bladder carcinogen. Animal studies of both ortho-toluidine and its possible confounders in these epidemiological investigations further confirm this hypothesis. When evaluated in a suitably comprehensive way, according to the traditional standards for assessing causality outlined by A. B. Hill ((1977) A Short Textbook of Medical Statistics, pp. 288-294, Lippincott, Philadelphia) the evidence that ortho-toluidine causes human bladder cancer has become much more conclusive. In this case, animal tests have proven a good predictor of human carcinogenicity.

  16. 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

  17. 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).

  18. EPRI/NRC workshop on nuclear power plant reevaluation to quantify seismic margins: proceedings

    SciTech Connect

    Not Available

    1985-08-01

    A three-day workshop on nuclear power plant reevaluation to quantify seismic margins was held in San Francisco on October 15-17, 1984. The workshop was cosponsored by the Nuclear Regulatory Commission and the Electric Power Research Institute. The primary objective of the workshop was to develop technical strategies by which utilities could demonstrate and the NRC could evaluate seismic margins for existing nuclear plants. These proceedings contain the text of the formal technical presentations as well as summaries of the working group sessions. Thirteen technical papers as well as NRC and EPRI reserach programs were presented at the technical sessions. Four working group discussion sessions were then held in the geotechnical/structural, piping, and equipment areas. Each group provided a forum for participants to exchange ideas and to discuss in more depth the criteria, methods and needs for plant seismic reevaluation. Recommendations from the working groups were summarized and presented at the end of the workshop.

  19. A numerical re-evaluation of the Mcdonald-Vaughan model for Raman depth profiling

    NASA Astrophysics Data System (ADS)

    Caro, Jacob; Heldens, Jeroen; Leenman, Dennis

    2013-02-01

    We re-evaluate the Macdonald-Vaughan model for Raman depth profiling [J. Raman Spectrosc. 38, 584 (2007)]. The model is an geometrical description of the sample regions from which Raman signal is collected in a confocal geometry and indicates that Raman signal also originates from far outside the focus. Although correct shapes of Raman depth profiles were obtained, quantitatively the results were not satisfactory, in view of the highly deviating values of the fitted extinction coefficients of the sample material. Our re-evaluation, based on a new numerical implementation of the model, indicates that the model is not only capable of predicting the proper profiles but also yields the right extinction coefficients. As a result, the model now is highly useful for interpretation of depth profiles, also for biomedical samples such as the human skin.

  20. 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.

  1. Reevaluation of the odd chrysidid genus Atoposega Krombein (Hymenoptera, Chrysididae, Amiseginae)

    PubMed Central

    Kimsey, Lynn S.

    2014-01-01

    Abstract The south Asian amisegine genus Atoposega Krombein, 1957, is reevaluated. Three new species, A. rufithorax, A. striata and A. thailandica are described from Thailand and the previously described species, A. lineata (Krombein, 1957) from Borneo, A. rieki (Krombein, 1957) from Myanmar and A. simulans Kimsey, 1986 from Malaysia are redescribed. The species, A. decorata Kimsey, 1995, was found to lack the generic characters diagnostic for Atoposega. Atoposega is only known from females. PMID:24899842

  2. [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.

  3. 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.

  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. 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.

  6. 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)

  7. A comparison of the chromatographic properties of silica gel and silicon hydride modified silica gels.

    PubMed

    Bawazeer, Saud; Sutcliffe, Oliver B; Euerby, Melvin R; Bawazeer, Sami; Watson, David G

    2012-11-09

    The retention properties of a silica gel column and a type C silica (silicon hydride) column for bases, sugars and polar acids were compared in hydrophilic interaction chromatography (HILIC) mode with formic acid or ammonium acetate as aqueous phase modifiers. The type C silica column was much more retentive for a series of model bases than the silica gel column and, surprisingly, retention of bases increased on the type C silica column when, the higher pH, ammonium acetate containing mobile phase was used. The retention of sugars was greater on the type C silica column than on the silica gel column and also increased on the type C silica column with increased pH suggesting either a silanophilic mechanism of retention or some unknown mechanism. Three type C silica based columns, type C silica, cogent diamond hydride and a β-pinene modified column, which it was hoped might exert some additional stereochemical discrimination, were tested for metabolomic profiling of urine. In general the unmodified type C silica column gave the strongest retention of the many polar metabolites in urine and could provide a useful complement to established HILIC methods for metabolomic profiling. Copyright © 2012 Elsevier B.V. All rights reserved.

  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. Advances in Silica Planar Lightwave Circuits

    NASA Astrophysics Data System (ADS)

    Doerr, Christopher Richard; Okamoto, Katsunari

    2006-12-01

    This paper presents a synopsis of some of the advances in silica waveguide planar lightwave circuits (PLCs). It concentrates on silica PLCs for fiber-optic communications, mainly routing and signal processing devices. A significant portion is devoted to arrayed waveguide gratings.

  10. 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.

  11. 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.

  12. 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.

  13. Pressure Drops Due to Silica Scaling

    SciTech Connect

    Brown, K.L.; Freeston, D.H.; Dimas, Z.O.; Slatter, A.

    1995-01-01

    Experience with reinjection returns in many geothermal fields has prompted a move towards injecting waste fluids at some distance from the production field. This means that often, reinjection pipelines cover very long distances. If the waste water in the pipelines is supersaturated with respect to amorphous silica, then the deposition of silica in these pipelines is almost certain. Although the deposit may be of negligible thickness, the inner surface characteristics of the pipe will be different to those of clean mild steel. During a silica scaling experiment. geothermal brine was passed through a series of pipes of different sizes and over a period of three weeks, silica scale formed on the inner surface. The pressure drop along a distance of approximately 5m was measured by a water manometer in all test pipe sections. Significant pressure drop was observed during this time and can be correlated with the increase in the friction factor of the pipe walls due to silica scaling.

  14. High purity silica reflecting heat shield development

    NASA Technical Reports Server (NTRS)

    Congdon, W.

    1974-01-01

    A reflecting heat shield composed of fused silica in which the scattering results from the refractive index mismatch between silica particles and the voids introduced during the fabrication process is developed. Major considerations and conclusions of the development are: the best material to use is Type A, which is capable of ultra-high-purity and which does not show the 0.243 micrometer absorption band; the reflection efficiency of fused silica is decreased at higher temperatures due to the bathochromic shift of the ultraviolet cut-off; for a given silica material, over the wavelength region and particle sizes tested, the monodisperse particle size configurations produce higher reflectances than continuous particle size configurations; and the smaller monodisperse particle size configurations give higher reflectance than the larger ones. A reflecting silica configuration that is an efficient reflector of shock layer radiation at high ablation temperatures is achieved by tailoring the matrix for optimum scattering and using an ultra-high-purity material.

  15. Tunable photoluminescence in monodisperse silica spheres.

    PubMed

    Kong, Deyan; Zhang, Cuimiao; Xu, Zhenhe; Li, Guogang; Hou, Zhiyao; Lin, Jun

    2010-12-15

    The nanometer-scale luminescent monodisperse silica spheres have been prepared by a water/oil (W/O) microemulsion method and the size of these spheres changed with the different concentrations of 3-aminopropyltriethoxysilane (APTES). The luminescent monodisperse silica spheres at the submicrometer scale have been prepared via Stöber method and the particles size increased with the increase of the amino concentrations. After calcination, all silica spheres do not change obviously in size. The annealed silica spheres contain C impurities and O defects, which resulted in the luminescence of silica spheres. The spheres showed variations in emission due to the different size and the concentration of organosiloxane precursors. Therefore, the emission can be tuned finely via the change of organosiloxane precursor and the size of samples. Copyright © 2010 Elsevier Inc. All rights reserved.

  16. Fluid diffusion in porous silica

    NASA Astrophysics Data System (ADS)

    McCann, Lowell I.

    Fluid motion in porous media has received a great deal of theoretical and experimental attention due to its importance in systems as diverse as ground water aquifers, catalytic processes, and size separation schemes. Often, the motion of interest is the random thermal motion of molecules in a fluid undergoing no net flow. This diffusive motion is particularly important when the size of the pores is nearly the same as the size of the molecules. In this study, fluid diffusion is measured in several varieties of porous silica whose pore structure is determined by the process by which it is made. The samples in this study have porosities (φ, the ratio of the pore volume to the total sample volume) that vary from 0.3 to 0.75 and average pore radii that range from approximately 15 to 120 A. Determining the effect of the pore structure on the diffusion of a liquid in a porous material is complicated by the chemical interactions between the diffusing molecules and the pore surface. In this study, ions in a hydrophilic fluid are used to block the adsorption of the diffusing dye molecules to the hydroxyl groups covering the silica surface. This technique is unlike typical surface treatments of silica in that it does not permanently alter the pore geometry. In this work, fluid diffusion is measured with a transient holographic grating technique where interfering laser beams create a periodic refractive index modulation in the fluid. The diffraction of a third laser off this grating is monitored to determine how quickly the grating relaxes, thereby determining the diffusion coefficient of the molecules in the fluid. Varying the grating periodicity controls the length scale of the diffusion measurement from 1.2 to 100 μm which is much larger than the average pore sizes of the samples. Therefore, over these large scales, we measure 'normal' diffusion, where the mean squared displacement of a diffusing particle varies linearly with time. In one particular type of porous silica

  17. 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

  18. 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

  19. Preparation and Characterization of Silica Aerogel Microspheres

    PubMed Central

    Chen, Qifeng; Wang, Hui; Sun, Luyi

    2017-01-01

    Silica aerogel microspheres based on alkali silica sol were synthesized using the emulsion method. The experimental results revealed that the silica aerogel microspheres (4–20 µm in diameter) were mesoporous solids with an average pore diameter ranging from 6 to 35 nm. The tapping densities and specific surface areas of the aerogel microspheres are in the range of 0.112–0.287 g/cm3 and 207.5–660.6 m2/g, respectively. The diameter of the silica aerogel microspheres could be tailored by varying the processing conditions including agitation rate, water/oil ratio, mass ratio of Span 80: Tween 80, and emulsifier concentration. The effects of these parameters on the morphology and textural properties of the synthesized silica aerogel microspheres were systematically investigated. Such silica aerogel microspheres can be used to prepare large-scale silica aerogels at an ambient pressure for applications in separation and high efficiency catalysis, which requires features of high porosity and easy fill and recovery. PMID:28772795

  20. Immobilization of silver nanoparticles on silica microspheres

    NASA Astrophysics Data System (ADS)

    Huang, Chih-Kai; Chen, Chia-Yin; Han, Jin-Lin; Chen, Chii-Chang; Jiang, Meng-Dan; Hsu, Jen-Sung; Chan, Chia-Hua; Hsieh, Kuo-Huang

    2010-01-01

    The silver nanoparticles (Ag NPs) have been immobilized onto silica microspheres through the adsorption and subsequent reduction of Ag+ ions on the surfaces of the silica microspheres. The neat silica microspheres that acted as the core materials were prepared through sol-gel processing; their surfaces were then functionalized using 3-mercaptopropyltrimethoxysilane (MPTMS). The major aims of this study were to immobilize differently sized Ag particles onto the silica microspheres and to understand the mechanism of formation of the Ag nano-coatings through the self-assembly/adsorption behavior of Ag NPs/Ag+ ions on the silica spheres. The obtained Ag NP/silica microsphere conglomerates were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy-dispersive spectroscopy (EDS). Their electromagnetic wave shielding effectiveness were also tested and studied. The average particle size of the obtained Ag NPs on the silica microsphere was found that could be controllable (from 2.9 to 51.5 nm) by adjusting the ratio of MPTMS/TEOS and the amount of AgNO3.

  1. 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.

  2. Light-Induced Surface Patterning of Silica.

    PubMed

    Kang, Hong Suk; Lee, Seungwoo; Choi, Jaeho; Lee, Hongkyung; Park, Jung-Ki; Kim, Hee-Tak

    2015-10-27

    Manipulating the size and shape of silica precursor patterns using simple far-field light irradiation and transforming such reconfigured structures into inorganic silica patterns by pyrolytic conversion are demonstrated. The key concept of our work is the use of an azobenzene incorporated silica precursor (herein, we refer to this material as azo-silane composite) as ink in a micromolding process. The moving direction of azo-silane composite is parallel to light polarization direction; in addition, the amount of azo-silane composite movement can be precisely determined by controlling light irradiation time. By exploiting this peculiar phenomenon, azo-silane composite patterns produced using the micromolding technique are arbitrarily manipulated to obtain various structural features including high-resolution size or sophisticated shape. The photoreconfigured patterns formed with azo-silane composites are then converted into pure silica patterns through pyrolytic conversion. The pyrolytic converted silica patterns are uniformly formed over a large area, ensuring crack-free formation and providing high structural fidelity. Therefore, this optical manipulation technique, in conjunction with the pyrolytic conversion process, opens a promising route to the design of silica patterns with finely tuned structural features in terms of size and shape. This platform for designing silica structures has significant value in various nanotechnology fields including micro/nanofluidic channel for lab-on-a-chip devices, transparent superhydrophobic surfaces, and optoelectronic devices.

  3. 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

  4. A re-evaluation of laser heterodyne radiometer ClO measurements. [for stratospheric chemistry studies

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.

    1983-01-01

    Previously reported measurements of stratospheric ClO using a balloon-borne laser heterodyne radiometer, launched from Palestine, Texas, are re-evaluated as a result of recent spectroscopic data. A spectral feature which was observed during September, 1978 and November, 1979 flights was incorrectly identified as a ClO absorption line, while a second feature observed during the latter flight with somewhat limited sensitivity is now believed to be due to ClO. This new interpretation results in a measured ClO profile which falls off more rapidly with decreasing altitude than the previous results indicated.

  5. 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.

  6. [Re-evaluate the value of orbital decompression for thyroid associated ophthalmopathy].

    PubMed

    Sun, F Y; Wu, T

    2017-06-11

    Thyroid-associated ophthalmopathy (TAO) is a common autoimmune syndrome affecting the thyroid and orbit. It can result in the fibrosis of extraoular muscles and hyperplasia of adipose tissue. The mechanism of TAO is not clear and there was few effective treatment. Recently, orbital decompression was performed on more and more patients. The surgery can improve the appearance of the patient and relieve the symptoms caused by the high orbital pressure. Therefore, it is necessary to re-evaluate the clinical value of the orbital decompression and surgical indications. The principles and techniques of orbital decompression with relative factors were discussed in this review. (Chin J Ophthalmol, 2017, 53: 401-403).

  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. Hydrophilic Silica-Polypeptide Composite Particles

    NASA Astrophysics Data System (ADS)

    Soto-Cantu, Erick; Russo, Paul

    2007-03-01

    Composite, pH-responsive particles have been synthesized by covalently attaching a simple polypeptide to a silica core. The synthesis begins with the production of organophilic poly(benzylglutamate)-coated silica particles. The particles are rendered hydrophilic by cleaving the benzyl side group by treatment with hydrogen bromide in benzene. The resulting poly(glutamic acid)-coated silica spheres exhibit a change in hydrodynamic radius in response to pH stimulus. The size transition is due to a change in the polypeptide conformation, as deduced from circular dichroism measurements. Fong,B.; Russo, P.S. Organophilic Colloidal Particles with a Synthetic Polypeptide Coating. Langmuir 1999, 15, 4421-4426.

  11. Ultrafast laser-induced birefringence in various porosity silica glasses: from fused silica to aerogel.

    PubMed

    Cerkauskaite, Ausra; Drevinskas, Rokas; Rybaltovskii, Alexey O; Kazansky, Peter G

    2017-04-03

    We compare a femtosecond laser induced modification in silica matrices with three different degrees of porosity. In single pulse regime, the decrease of substrate density from fused silica to high-silica porous glass and to silica aerogel glass results in tenfold increase of laser affected region with the formation of a symmetric cavity surrounded by the compressed silica shell with pearl like structures. In multi-pulse regime, if the cavity produced by the first pulse is relatively large, the subsequent pulses do not cause further modifications. If not, the transition from void to the anisotropic structure with the optical axis oriented parallel to the incident polarization is observed. The maximum retardance value achieved in porous glass is twofold higher than in fused silica, and tenfold greater than in aerogel. The polarization sensitive structuring in porous glass by two pulses of ultrafast laser irradiation is demonstrated, as well as no observable stress is generated at any conditions.

  12. Fluorescence imaging of the desorption of dye from fused silica versus silica gel.

    PubMed

    Ludes, Melody D; Anthony, Shyroine R; Wirth, Mary J

    2003-07-01

    The desorption rate constants for a cationic dye from strong adsorption sites are compared for the same chromatographic interface but for two different substrates, fused silica and chromatographic silica gel. The dye is 1,1'-didodecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI). The interface consists of acetonitrile and a hydrocarbon monolayer (C8) covalently bound to the silica substrate. To measure slow desorption from fused silica, fluorescence imaging combined with correlation spectroscopy is used. To measure slow desorption from silica gel, fluorescence movies of silica gel particles are used. In both cases, the results show that there are two types of slow desorption processes on time scales exceeding 1 s. The desorption time from one type of site is within an experimental error of 7 s for both silica substrates. The adsorption kinetics for this type of site are slow, and the equilibrium population of DiI on these sites is comparable to that for DiI weakly adsorbed to the hydrocarbon monolayer. For the second type of site, for fused silica, the population of DiI is even higher than that of weakly adsorbed DiI, and the desorption time constant is approximately 2 min, although this is likely shortened by photobleaching. For silica gel, the relative population of DiI on this ultrastrong site is more than an order of magnitude lower, and the desorption time constant is 4.0 +/- 0.1 min. Both silica substrates thus show two types of sites whose time constants agree within experimental error, suggesting that the strong adsorption sites on fused silica are chemically the same as those on chromatographic silica gel.

  13. Photoluminescence decay dynamics of transparent silica glass prepared from nanometer-sized silica particles

    SciTech Connect

    Yamada, Tomoko; Uchino, Takashi

    2005-08-22

    The time-resolved photoluminescence (PL) decays are measured for transparent amorphous silica prepared from solid-phase sintering of nanometer-sized silica particles, which has recently been shown to exhibit a unique white PL emission under ultraviolet excitation [T. Uchino and T. Yamada, Appl. Phys. Lett. 85, 1164 (2004)]. Unlike usual PL processes observed in normal silica glass, it is shown that the present PL results from trapping-controlled migration of photoexcited carriers and their radiative recombination.

  14. Photoluminescence decay dynamics of transparent silica glass prepared from nanometer-sized silica particles

    NASA Astrophysics Data System (ADS)

    Yamada, Tomoko; Uchino, Takashi

    2005-08-01

    The time-resolved photoluminescence (PL) decays are measured for transparent amorphous silica prepared from solid-phase sintering of nanometer-sized silica particles, which has recently been shown to exhibit a unique white PL emission under ultraviolet excitation [T. Uchino and T. Yamada, Appl. Phys. Lett. 85, 1164 (2004)]. Unlike usual PL processes observed in normal silica glass, it is shown that the present PL results from trapping-controlled migration of photoexcited carriers and their radiative recombination.

  15. The carcinogenic action of crystalline silica: a review of the evidence supporting secondary inflammation-driven genotoxicity as a principal mechanism.

    PubMed

    Borm, Paul J A; Tran, Lang; Donaldson, Ken

    2011-10-01

    In 1987 the International Agency for Research on Cancer (IARC) classified crystalline silica (CS) as a probable carcinogen and in 1997 reclassified it as a Group 1 carcinogen, i.e., that there was sufficient evidence for carcinogenicity in experimental animals and sufficient evidence for carcinogenicity in humans. The Working Group noted that "carcinogenicity in humans was not detected in all industrial circumstances studied, carcinogenicity may be dependent on inherent characteristics of the crystalline silica or on external factors affecting its biological activity or distribution of its polymorphs." This unusual statement that the physicochemical form of the CS influences its carcinogenicity is well understood at the toxicological level and arises as a consequence of the fact that CS activity depends on the reactivity of the CS surface, which can be blocked by a number of agents. We reviewed the literature on CS genotoxicity that has been published since the 1997 monograph, with special reference to the mechanism of CS genotoxicity. The mechanism of CS genotoxicity can be primary, a result of direct interaction of CS with target cells, or indirect, as a consequence of inflammation elicited by quartz, where the inflammatory cell-derived oxidants cause the genotoxicity. The review revealed a number of papers supporting the hypothesis that the CS genotoxic and inflammatory hazard is a variable one. In an attempt to attain a quantitative basis for the potential mechanism, we carried out analysis of published data and noted a 5-fold greater dose required to reach a threshold for genotoxic effects than for proinflammatory effects in the same cell line in vitro. When we related the calculated threshold dose at the proximal alveolar region for inflammation in a published study with the threshold dose for genotoxicity in vitro, we noted that a 60-120-fold greater dose was required for direct genotoxic effects in vitro. These data strongly suggests that inflammation is

  16. 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.

  17. Carbon-Coated Silica and Silica-Coated Carbon for Elastomer Reinforcement

    NASA Astrophysics Data System (ADS)

    Kohls, D. J.; Beaucage, G.; Pratsinis, S. E.; Kammler, H.

    2000-03-01

    Recently several silica producers have introduced dual-phase grades of silica/carbon powders intended for use in elastomer reinforcement. These mass-produced, nano-structured materials have carbon content in excess of 75carbon aggregates, the intent being to enhance the strength of filler-filler networking in a nano-composite. We have recently developed pyrolytic, nano-scale silica aggregates with interfacial carbon (typically less than 3the aim of enhancing elastomer-filler interaction in green tires. Our carbon-coated silicas display improved processability in typical tire compounds and enhanced dynamic mechanical performance. We also have developed facilities to produce organically functionalized silicas using a novel, room-temperature, aerosol, chemical reactor (ASG reactor). This talk will present our results on dynamic mechanical properties of elastomer compounds with our carbon-coated silica; commercial dual-phase, silica-coated carbon; ASG-organically-modified silicas; conventional carbon black; conventional precipated and fumed silica; as well as blends of the conventional materials. The mass-fractal structure as determined by SAXS and SALS, as well as gas and DBP absorption measurements and microscopy will be presented.

  18. Adhesion of gels by silica particle.

    PubMed

    Abe, Hidekazu; Hara, Yusuke; Maeda, Shingo; Hashimoto, Shuji

    2014-03-06

    In this study, a method for achieving adhesion between two positively charged gels with high mechanical strength was developed. By utilizing a silica particle dispersion as a binder, the gels easily adhered to each other and remained stable for up to 11 days when immersed in aqueous solution. The adhesion force between the two positively charged semi-interpenetrating network gels with the silica particle was measured to be up to approximately 20 kPa, which is around 10 times larger than that with a charged polymer-rich liquid as a cross-linker (approximately 1.5 kPa). It was demonstrated that the adhesion force was a result of two types of interactions: an electrostatic attractive force between the cationic gel surface and hydrogen bonding among the silica particles. In addition, it was shown that the adhesion force was dependent on solution pH, which was attributed to changes in the charge of the silica particles.

  19. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... DRINKING WATER OF ANIMALS Listing of Specific Substances Affirmed as GRAS § 584.700 Hydrophobic silicas. (a.... It must be of purity suitable for intended use, and it must comply with the following specifications...

  20. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... DRINKING WATER OF ANIMALS Listing of Specific Substances Affirmed as GRAS § 584.700 Hydrophobic silicas. (a.... It must be of purity suitable for intended use, and it must comply with the following specifications...

  1. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... DRINKING WATER OF ANIMALS Listing of Specific Substances Affirmed as GRAS § 584.700 Hydrophobic silicas. (a.... It must be of purity suitable for intended use, and it must comply with the following specifications...

  2. Silica precipitation with synthetic silaffin peptides.

    PubMed

    Wieneke, Ralph; Bernecker, Anja; Riedel, Radostan; Sumper, Manfred; Steinem, Claudia; Geyer, Armin

    2011-08-07

    Silaffins are highly charged proteins which are one of the major contributing compounds that are thought to be responsible for the formation of the hierarchically structured silica-based cell walls of diatoms. Here we describe the synthesis of an oligo-propyleneamine substituted lysine derivative and its incorporation into the KXXK peptide motif occurring repeatedly in silaffins. N(ε)-alkylation of lysine was achieved by a Mitsunobu reaction to obtain a protected lysine derivative which is convenient for solid phase peptide synthesis. Quantitative silica precipitation experiments together with structural information about the precipitated silica structures gained by scanning electron microscopy revealed a dependence of the amount and form of the silica precipitates on the peptide structure.

  3. Accelerated purification of colloidal silica sols

    NASA Technical Reports Server (NTRS)

    Bahnsen, E. B.; Garofalini, S.; Pechman, A.

    1979-01-01

    Accelerated purification process for colloidal sols using heat/deionization scheme, sharply reduces waiting time between deionization cycles from several months to a few days. Process produces same high purity silica sols as conventional methods.

  4. 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.

  5. [Case in which transesophageal echocardiography after induction of anaesthesia was useful for reevaluation of preoperative diagnosis].

    PubMed

    Ueno, Megumi; Kunisawa, Takayuki; Nagashima, Michio; Suzuki, Akihiro; Takahata, Osamu; Iwasaki, Hiroshi

    2010-01-01

    A woman in her 70's had undergone two valve replacements (mitral valve and aortic valve). A transendothelial chest wall echocardiogram (TTE) showed that a flap lobe of a mitral mechanical valve had fixed the valve in a closed state, and it was diagnosed as stuck leaflet of a bileaflet prosthesis in the mitral position. She was scheduled for emergency surgery for mitral valve replacement. After induction of anaesthesia, a transesophageal echocardiography (TEE) probe was inserted. Observation of two-dimensional images showed that the bileaflet mechanical valve in the mitral position was functioning properly. Pulsed wave Doppler measurements showed that maximum blood flow rate, pressure-half-time, maximum gradient and average gradient were 1.5 m x sec(-1), 64 ms, 9.0 mmHg and 3.5 mmHg, respectively, and there were no findings suggesting mitral stenosis. TEE showed that there was no stuck leaflet of the bileaflet prosthesis in the mitral position, and the operation was called off. The patient was followed up in the intensive care unit. In this case, TEE was useful for reevaluation of the preoperative diagnosis and for reevaluation of indication for surgery.

  6. Reevaluation of the Munro dataset to derive more specific TTC thresholds.

    PubMed

    Leeman, Winfried R; Krul, Lisette; Houben, Geert F

    2014-07-01

    The threshold of toxicological concern (TTC) concept is a risk assessment tool for substances present at low oral exposure and lacking hazard data. In the past, several thresholds were elaborated by Munro et al. (1996) and Kroes et al. (2004). For these TTC thresholds, the Cramer class III threshold is based on a broad spectrum of substances, including organophosphates. For organophosphates a separate threshold was elaborated by Kroes et al. (2004), however without adjustment of the Cramer class III threshold. Moreover, reference was made by Munro et al. (2008) that for organohalogens a separate threshold also may apply whereas the EFSA (2012) considers that carbamate substances with anti-choline esterase activity can be included in the threshold for organophosphates. In this paper, a reevaluation of the Munro dataset (original TTC database) was performed, focused on the thresholds for organophosphates including carbamates, organohalogens and remaining Cramer class III substances. This way thresholds for each of these groups are elaborated. As a results of the current reevaluation of the Munro dataset, thresholds for life-time exposure are elaborated for the group of organophosphates including carbamates, the group of organohalogens and the remaining Cramer class III substances, being 0.30, 1.5 and 4.0 μg/kg bodyweight/day, respectively. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. 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.

  8. 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.

  9. Vibrating reed experiments on compacted vitreous silica

    NASA Astrophysics Data System (ADS)

    Weiss, G.; Daum, A.; Sohn, M.; Arndt, J.

    1996-02-01

    We have studied the acoustic properties of irreversibly compacted vitreous silica (Suprasil I) at frequencies around 12 kHz between 10 mK and room temperature. At low temperatures up to a few K the compacted glass exhibits acoustic properties similar to those of normal vitreous silica, however, with considerably smaller values of the damping and of the temperature coefficient of the sound velocity. Around 30 K the internal friction is reduced by factor of 6.

  10. [Basic requirements on post-marketing clinical re-evaluation of chinese medicine and phase IV clinical trials].

    PubMed

    Xie, Yanming; Wang, Yanping; Tian, Feng; Wang, Yongyan

    2011-10-01

    As information on safety and effectiveness is not comprehensive, gained from the researches for listing approval of Chinese medicine, it is very necessary to conduct post-marketing clinical re-evaluation of Chinese medicine. Effectiveness, safety and economic evaluation are three main aspects of post-marketing clinical re-evaluation. In this paper, the difference and relations between the post-marketing clinical re-evaluation and the phase IV clinical trials were discussed, and the basic requests and suggestions were proposed, according to the domestic and foreign relevant regulations and experts' suggestions, and discussed the requirements of the phase IV clinical trials on indications, design methods, inclusion and exclusion criteria, sample size, etc.

  11. [Post-marketing re-evaluation about usage and dosage of Chinese medicine based on human population pharmacokinetics].

    PubMed

    Jiang, Junjie; Xie, Yanming

    2011-10-01

    The usage and dosage of Chinese patent medicine are determined by rigorous evaluation which include four clinical trail stages: I, II, III. But the usage and dosage of Chinese patent medicine are lacked re-evaluation after marketing. And this lead to unchanging or fixed of the usage and dosage of Chinese patent medicine instead of different quantity based on different situations in individual patients. The situation of Chinese patent medicine used in clinical application is far away from the idea of the "Treatment based on syndrome differentiation" in traditional Chinese medicine and personalized therapy. Human population pharmacokinetics provides data support to the personalized therapy in clinical application, and achieved the postmarking reevaluating of the usage and dosage of Chinese patent medicine. This paper briefly introduced the present situation, significance and the application of human population pharmacokinetics about re-evaluation of the usage and dosage of Chinese patent medicine after marketing.

  12. 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

  13. Hollow silica spheres: synthesis and mechanical properties.

    PubMed

    Zhang, Lijuan; D'Acunzi, Maria; Kappl, Michael; Auernhammer, Günter K; Vollmer, Doris; van Kats, Carlos M; van Blaaderen, Alfons

    2009-03-03

    Core-shell polystyrene-silica spheres with diameters of 800 nm and 1.9 microm were synthesized by soap-free emulsion and dispersion polymerization of the polystyrene core, respectively. The polystyrene spheres were used as templates for the synthesis of silica shells of tunable thickness employing the Stöber method [Graf et al. Langmuir 2003, 19, 6693]. The polystyrene template was removed by thermal decomposition at 500 degrees C, resulting in smooth silica shells of well-defined thickness (15-70 nm). The elastic response of these hollow spheres was probed by atomic force microscopy (AFM). A point load was applied to the particle surface through a sharp AFM tip, and successively increased until the shell broke. In agreement with the predictions of shell theory, for small deformations the deformation increased linearly with applied force. The Young's modulus (18 +/- 6 GPa) was about 4 times smaller than that of fused silica [Adachi and Sakka J. Mater. Sci. 1990, 25, 4732] but identical to that of bulk silica spheres (800 nm) synthesized by the Stöber method, indicating that it yields silica of lower density. The minimum force needed to irreversibly deform (buckle) the shell increased quadratically with shell thickness.

  14. Grazers: biocatalysts of terrestrial silica cycling

    PubMed Central

    Vandevenne, Floor Ina; Barão, Ana Lúcia; Schoelynck, Jonas; Smis, Adriaan; Ryken, Nick; Van Damme, Stefan; Meire, Patrick; Struyf, Eric

    2013-01-01

    Silica is well known for its role as inducible defence mechanism countering herbivore attack, mainly through precipitation of opaline, biogenic silica (BSi) bodies (phytoliths) in plant epidermal tissues. Even though grazing strongly interacts with other element cycles, its impact on terrestrial silica cycling has never been thoroughly considered. Here, BSi content of ingested grass, hay and faeces of large herbivores was quantified by performing multiple chemical extraction procedures for BSi, allowing the assessment of chemical reactivity. Dissolution experiments with grass and faeces were carried out to measure direct availability of BSi for dissolution. Average BSi and readily soluble silica numbers were higher in faeces as compared with grass or hay, and differences between herbivores could be related to distinct digestive strategies. Reactivity and dissolvability of BSi increases after digestion, mainly due to degradation of organic matrices, resulting in higher silica turnover rates and mobilization potential from terrestrial to aquatic ecosystems in non-grazed versus grazed pasture systems (2 versus 20 kg Si ha−1 y−1). Our results suggest a crucial yet currently unexplored role of herbivores in determining silica export from land to ocean, where its availability is linked to eutrophication events and carbon sequestration through C–Si diatom interactions. PMID:24107532

  15. 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.

  16. Anomalous Enthalpy Relaxation in Vitreous Silica

    NASA Astrophysics Data System (ADS)

    Yue, Yuanzheng

    2015-08-01

    It is a challenge to calorimetrically determine the glass transition temperature (Tg) of vitreous silica. Here we demonstrate that this challenge mainly arises from the extreme sensitivity of the Tg to the hydroxyl content in vitreous silica, but also from the irreversibility of its glass transition when repeating the calorimetric scans. It is known that the liquid fragility (i.e., the speed of the viscous slow-down of a supercooled liquid at its Tg during cooling) has impact on enthalpy relaxation in glass. Here we find that vitreous silica (as a strong system) exhibits striking anomalies in both glass transition and enthalpy relaxation compared to fragile oxide systems. The anomalous enthalpy relaxation of vitreous silica is discovered by performing the hperquenching-annealing-calorimetry experiments. We argue that the strong systems like vitreous silica and vitreous Germania relax in a structurally cooperative manner, whereas the fragile ones do in a structurally independent fashion. We discuss the origin of the anomalous enthalpy relaxation in the HQ vitreous silica.

  17. Grazers: biocatalysts of terrestrial silica cycling.

    PubMed

    Vandevenne, Floor Ina; Barão, Ana Lúcia; Schoelynck, Jonas; Smis, Adriaan; Ryken, Nick; Van Damme, Stefan; Meire, Patrick; Struyf, Eric

    2013-12-07

    Silica is well known for its role as inducible defence mechanism countering herbivore attack, mainly through precipitation of opaline, biogenic silica (BSi) bodies (phytoliths) in plant epidermal tissues. Even though grazing strongly interacts with other element cycles, its impact on terrestrial silica cycling has never been thoroughly considered. Here, BSi content of ingested grass, hay and faeces of large herbivores was quantified by performing multiple chemical extraction procedures for BSi, allowing the assessment of chemical reactivity. Dissolution experiments with grass and faeces were carried out to measure direct availability of BSi for dissolution. Average BSi and readily soluble silica numbers were higher in faeces as compared with grass or hay, and differences between herbivores could be related to distinct digestive strategies. Reactivity and dissolvability of BSi increases after digestion, mainly due to degradation of organic matrices, resulting in higher silica turnover rates and mobilization potential from terrestrial to aquatic ecosystems in non-grazed versus grazed pasture systems (2 versus 20 kg Si ha(-1) y(-1)). Our results suggest a crucial yet currently unexplored role of herbivores in determining silica export from land to ocean, where its availability is linked to eutrophication events and carbon sequestration through C-Si diatom interactions.

  18. 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.

  19. 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.

  20. 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

  1. Relating Silica Scaling in Reverse Osmosis to Membrane Surface Properties.

    PubMed

    Tong, Tiezheng; Zhao, Song; Boo, Chanhee; Hashmi, Sara M; Elimelech, Menachem

    2017-04-18

    We investigated the relationship between membrane surface properties and silica scaling in reverse osmosis (RO). The effects of membrane hydrophilicity, free energy for heterogeneous nucleation, and surface charge on silica scaling were examined by comparing thin-film composite polyamide membranes grafted with a variety of polymers. Results show that the rate of silica scaling was independent of both membrane hydrophilicity and free energy for heterogeneous nucleation. In contrast, membrane surface charge demonstrated a strong correlation with the extent of silica scaling (R(2) > 0.95, p < 0.001). Positively charged membranes significantly facilitated silica scaling, whereas a more negative membrane surface charge led to reduced scaling. This observation suggests that deposition of negatively charged silica species on the membrane surface plays a critical role in silica scale formation. Our findings provide fundamental insights into the mechanisms governing silica scaling in reverse osmosis and highlight the potential of membrane surface modification as a strategy to reduce silica scaling.

  2. 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.

  3. Effects of silica content on the formation and morphology of ENR/PVC/Silica composites beads

    NASA Astrophysics Data System (ADS)

    Abdullah, Nurul Amni; Tahiruddin, Nordiana Suhada Mohmad; Othaman, Rizafizah

    2017-05-01

    The effects of silica content in preparing silica-filled epoxidized natural rubber/polyvinyl chloride (ENR/PVC) beads were investigated. ENR/PVC matrix blend used was of composition 60% (ENR50) and 40% (PVC) by weight. The matrix blend was then dissolved in tetrahydrofuran (THF) by sol-gel technique prior to addition of silica fume as filler at varying amounts up to 25 wt% of the matrix mass. The composites beads were formed via phase inversion method by dropping the polymeric solution into a non-solvent. The size and shape were improved by adding in an increased amount of silica. Morphological studies showed distinct features of beads' surface in terms of homogeneity of silica particle distribution and presence of agglomerations and voids within the ENR/PVC matrix. Formation of silica network was apparent on the bead at 25 wt% silica content. The bead formation was found to be significantly affected by the silica loading in the ENR/PVC solution.

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

    PubMed

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

    2012-08-29

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

  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. 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.

  7. 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...

  8. 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...

  9. Silica-based cationic bilayers as immunoadjuvants

    PubMed Central

    Lincopan, Nilton; Santana, Mariana RA; Faquim-Mauro, Eliana; da Costa, Maria Helena B; Carmona-Ribeiro, Ana M

    2009-01-01

    Background Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design. Results Firstly, the silica/DODAB assembly was characterized at 1 mM NaCl, pH 6.3 or 5 mM Tris.HCl, pH 7.4 and 0.1 mg/ml silica over a range of DODAB concentrations (0.001–1 mM) by means of dynamic light scattering for particle sizing and zeta-potential analysis. 0.05 mM DODAB is enough to produce cationic bilayer-covered particles with good colloid stability. Secondly, conditions for maximal adsorption of bovine serum albumin (BSA) or a recombinant, heat-shock protein from Mycobacterium leprae (18 kDa-hsp) onto DODAB-covered or onto bare silica were determined. At maximal antigen adsorption, cellular immune responses in vivo from delayed-type hypersensitivity reactions determined by foot-pad swelling tests (DTH) and cytokines analysis evidenced the superior performance of the silica/DODAB adjuvant as compared to alum or antigens alone whereas humoral response from IgG in serum was equal to the one elicited by alum as adjuvant. Conclusion Cationized silica is a biocompatible, inexpensive, easily prepared and possibly general immunoadjuvant for antigen presentation which displays higher colloid stability than alum, better performance regarding cellular immune responses and employs very low, micromolar doses of cationic and toxic synthetic lipid. PMID:19152701

  10. Chemistry of Silica in Cerro Prieto Brines

    SciTech Connect

    Weres, Oleh; Iglesias, Eduardo; Tsao, Leon

    1980-04-01

    The precipitation of amorphous silica from synthetic geothermal, brines which resemble the flashed brine at Cerro Prieto has been studied. It was found that part of the dissolved silica quickly polymerizes to form suspended colloidal silica. The colloidal silica flocculates and settles slowly at unmodified brine pH values near 7.35. Raising the pH of the brine to about 7.8 by adding base and stirring for a few minutes causes rapid and complete flocculation and settling. these results have been confirmed in the field using actual Cerro Prieto brine. Both in the laboratory and in the field quaternary amines were found to be effective with some brine compositions but not with others. Polyacrylamides do not work at all. These results suggest the following simple preinjection brine treatment process: age the brine for 10-20 minutes in a covered holding tank, add 20-30 ppm lime (CaO), stir for 5 minutes, and separate the flocculated silica from the brine using a conventional clarifier. The brine coming out of such a process will be almost completely free of suspended solids. The pilot plant tests needed to reduce this conceptual process to practice are discussed. The rate of deposition of silica scale from synthetic brines was separately studied. It was found that a modest decrease in pH could significantly reduce the scaling rate at a reasonable cost. The equilibrium chemistry of Cerro Prieto brine was studied theoretically. These calculations indicate that increasing the brine pH to remove silica might cause some precipitation of carbonate minerals, but also that this problem could easily be eliminated at a reasonable cost if it did arise.

  11. Hydrothermal synthesis of hollow silica spheres under acidic conditions.

    PubMed

    Yu, Qiyu; Wang, Pengpeng; Hu, Shi; Hui, Junfeng; Zhuang, Jing; Wang, Xun

    2011-06-07

    It is well-known that silica can be etched in alkaline media or in a unique hydrofluoric acid (HF) solution, which is widely used to prepare various kinds of hollow nanostructures (including silica hollow structures) via silica-templating methods. In our experiments, we found that stöber silica spheres could be etched in generic acidic media in a well-controlled way under hydrothermal conditions, forming well-defined hollow/rattle-type silica spheres. Furthermore, some salts such as NaCl and Na(2)SO(4) were found to be favorable for the formation of hollow/rattle-type silica spheres.

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. Generation of crystalline silica from sugarcane burning.

    PubMed

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

    2010-07-08

    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

  18. Reevaluating the tectonic uplift of western Mount Carmel, Israel, since the middle Pleistocene

    NASA Astrophysics Data System (ADS)

    Zviely, Dov; Galili, Ehud; Ronen, Avraham; Salamon, Amos; Ben-Avraham, Zvi

    2009-03-01

    Reevaluation of geological and archaeological evidence from western Mount Carmel constrains its maximal tectonic uplift since the Middle Pleistocene. Tabun Cave, presently 45 m above sea level (asl), revealed human occupation from about 600 ka to 90 ka before present. The 25 m thick archaeological strata at Tabun are composed of laminated fine sand, silt and clays. Moreover, no marine deposits were found in Tabun or nearby caves. Since sea level in the last 600 ka reached a maximal of 5 to 10 m asl, Tabun Cave could not have been uplifted since then by more than 35 to 40 m, that is a maximal average rate of 58 to 67 mm/ka.

  19. Reevaluation of an individual's radiation exposure at NTS in 1963-64. [FRAN reactor

    SciTech Connect

    Myers, D.S.

    1983-02-25

    The FRAN prompt burst reactor began operation at NTS on November 1, 1962 and continued in use until April 1965. From January 2, 1963 to August 12, 1964, an individual periodically performed maintenance and troubleshooting functions on various components of the FRAN reactor system. In June, 1980, the individual requested a review of the radiation dose that he received from his involvement with the FRAN reactor. An evaluation of the individual's radiation dose associated with the FRAN reactor operation was performed. This report details the reevaluation of the individual's estimated radiation dose from the FRAN reactor assembly, as derived from computer calculations, GODIVA-IV measurements, personnel dosimetry results, and a reconstruction of work scenarios.

  20. The squirrel hill site: A comparative geophysical investigation and cultural reevaluation

    NASA Astrophysics Data System (ADS)

    DeHaven, Lydia Sue

    The Squirrel Hill site is one of the defining sites of the Johnston phase (A.D. 1450-1590) of the Monongahela tradition. Limited investigations of the site have taken place, but no notes or site maps remain. As part of the Johnston phase, the site has also been hypothesized to represent an amalgamation of the Monongahela with the McFate culture from northwestern Pennsylvania. This thesis addresses two research topics: a.) the efficiency in using geophysical instruments to relocate prehistoric sites in the region and b.) a re-evaluation of the site's relation to the Johnston phase and the presence of the McFate culture. These research topics were investigated through multiple surveys with different geophysical instruments, excavation, artifact analysis and AMS radiocarbon dating.

  1. Re-evaluating Traditional Predictors of Incoming Knowledge in Astronomy 101 and Implications for Course Revitalization

    NASA Astrophysics Data System (ADS)

    Berryhill, K. J.; Slater, T. F.; Slater, S. J.; Harbour, C.; Forrester, J. H.

    2016-12-01

    A wide range of incoming knowledge is seen in students taking introductory astronomy courses. Using the Test Of Astronomy STandards (TOAST) as a pre-course measure of incoming knowledge, an evaluation was completed to discover any explanation for this variation. It would be reasonable to suggest that this could result from the variety we see in student's motivation, self-efficacy, general scholastic achievement, their high school science experience, or even whether one or more of their parents is in a STEM field. In this re-evaluation, there was no correlation seen between the above and the student's pre-test scores. Instead, the only predictor of pretest scores was student's exposure to astronomy through informal learning opportunities. This leads to important implications for faculty revitalizing their courses to improve student learning.

  2. A re-evaluation of subspecific variation and canine dimorphism in woolly spider monkeys (Brachyteles arachnoides).

    PubMed

    Leigh, S R; Jungers, W L

    1994-12-01

    A recent study suggests that differing populations of woolly spider monkeys exhibit a substantial degree of morphological, cytogenetic, and behavioral variation. We re-evaluate the differences between populations in the degree of canine tooth height sexual dimorphism and in the frequency of thumbs. Statistical analysis of variation in the degree of canine sexual dimorphism between these populations fails to provide strong evidence for subspecific variation: differences in the degree of canine dimorphism cannot be considered statistically significant. Differences between populations in the frequency of thumbs are, however, statistically significant. The lack of clear distinctions between populations in the degree of canine dimorphism complicates assessments of behavioral variation between these populations. We suggest that the level of geographic variation in woolly spider monkey canine dimorphism is not consistent with subspecific status.

  3. 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.

  4. Re-evaluation of the 1962 Mark VI-B dynamic tests regarding reactivity coefficients

    SciTech Connect

    Burnett, T.

    1991-06-01

    The 1962 Mark VI-B rod tests have been re-evaluated. A significantly lower (more negative) coolant coefficient is now ascribed to that test, {minus}1 pcm/Deg-C vs the previously reported +2 pcm/Deg-C. The change from the previous value is because of revisions to delayed neutron constants and accounting for spatial effects. The new value is in reasonable agreement with the currently calculated value of {minus}2 pcm/Deg-C, considering measurement and calculational uncertainties. Therefore, the authors conclude that the current analytic models for physics and transient analysis methodology (GLASS, GRIMHX & TRIMHX, AND MARY) are fully consistent with 1962 test observations, and that there is no basis for assigning a calculational bias or increasing uncertainty allowances.

  5. New approaches to prepare hydride silica.

    PubMed

    Gomez, Jorge E; Sandoval, Junior E

    2010-09-01

    Two synthetic schemes to produce a hydride-modified support that serves as an intermediate for the preparation of bonded phases for liquid chromatography (LC) and capillary electrophoresis (CE) are investigated. The strategies differ in the silane reagent utilized (trichlorosilane (TCS) or triethoxysilane (TES)) and the manner water is incorporated into the reaction. In the first approach, TCS in toluene reacts with a previously humidified silica substrate so that the reaction is confined to the silica surface. In the second approach, TES and a small amount of aqueous HCl are dissolved in THF, and this hydrolysate is diluted by a great factor in cyclohexane, prior to reaction with the silica substrate. Atomic force microscopy (AFM) images of the hydride film on wafers revealed that, unlike the traditional approach that produced a patchy coating, both new methods provided a homogeneous layer on the substrate's surface. IR and NMR spectra from porous silica particles clearly confirmed a successful surface modification. AFM and water contact angles (WCA) were used to examine the effect of dilution of the TES hydrolysate in cyclohexane on the trend of the film to polymerize on wafers and found that a dilution factor of at least 100 is required to attain a molecularly thin hydride layer. WCA and CE also revealed a strong susceptibility of the hydride silica intermediate to hydrolyze, even at low pH. Compared to TCS, the lower reactivity and volatility of TES resulted in a much more desirable experimental approach.

  6. Molecular imprinting of bulk, microporous silica

    NASA Astrophysics Data System (ADS)

    Katz, Alexander; Davis, Mark E.

    2000-01-01

    Molecular imprinting aims to create solid materials containing chemical functionalities that are spatially organized by covalent or non-covalent interactions with imprint (or template) molecules during the synthesis process. Subsequent removal of the imprint molecules leaves behind designed sites for the recognition of small molecules, making the material ideally suited for applications such as separations, chemical sensing and catalysis. Until now, the molecular imprinting of bulk polymers and polymer and silica surfaces has been reported, but the extension of these methods to a wider range of materials remains problematic. For example, the formation of substrate-specific cavities within bulk silica, while conceptually straightforward, has been difficult to accomplish experimentally. Here we describe the imprinting of bulk amorphous silicas with single aromatic rings carrying up to three 3-aminopropyltriethoxysilane side groups; this generates and occupies microporosity and attaches functional organic groups to the pore walls in a controlled fashion. The triethoxysilane part of the molecules' side groups is incorporated into the silica framework during sol-gel synthesis, and subsequent removal of the aromatic core creates a cavity with spatially organized aminopropyl groups covalently anchored to the pore walls. We find that the imprinted silicas act as shape-selective base catalysts. Our strategy can be extended to imprint other functional groups, which should give access to a wide range of functionalized materials.

  7. 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

  8. Reevaluation of long-term Umkehr data and ozone profiles at Japanese stations

    NASA Astrophysics Data System (ADS)

    Miyagawa, Koji; Sasaki, Toru; Nakane, Hideaki; Petropavlovskikh, Irina; Evans, Robert D.

    2009-04-01

    Umkehr observations have been routinely conducted at Japanese stations, Sapporo, Tsukuba, Kagoshima, and Naha, and the Antarctic station, Syowa, for more than 50 years. Umkehr data are a valuable source of information on long-term changes in the ozone vertical profile; however, the Umkehr record at Japanese stations has evident discontinuities. The majority of the discontinuities are related to the exchange of instruments for calibration (for total ozone measurements) and the replacement of instruments. These discontinuities may be related to the difference in instrument characteristics. In this article, reevaluation of the long-term Umkehr data in Japanese network is done by assessment of instrument-related changes in compared N values that exhibit solar zenith angle and total ozone dependence in addition to the step changes. The systematic errors are evaluated by simultaneous intercomparisons of each instrument with the reference instrument. Through this reevaluation, most discontinuities in a station's Umkehr time series are successfully corrected, and new sets of ozone vertical profiles are derived. The ozone profiles retrieved by two available Umkehr retrieval algorithms are compared with ozonesonde observations at every station and ozone lidar observations at Tsukuba. The results show that the revised Umkehr ozone profiles show improved consistency with both types of auxiliary ozone observations as compared to the old data sets, especially with regard to ozonesonde observations (difference of less than 5%). Trend analyses of the revised Umkehr ozone profile time series show a significant decrease in stratospheric ozone over Japan during the 1980s. It also varies between stations, with Naha showing the least significant trend among Japanese stations and Sapporo exhibiting as much as 6% of ozone decline per decade. In addition, a positive and statistically significant trend is detected in tropospheric ozone column at Naha (˜5.5% per decade) and Tsukuba (˜3

  9. [Post-marketing reevaluation for potential quality risk and quality control in clinical application of traditional Chinese medicines].

    PubMed

    Li, Hong-jiao; He, Li-yun; Liu, Bao-yan

    2015-06-01

    The effective quality control in clinical practices is an effective guarantee for the authenticity and scientificity of the findings. The post-marketing reevaluation for traditional Chinese medicines (TCM) focuses on the efficacy, adverse reaction, combined medication and effective dose of drugs in the market by expanded clinical trials, and requires a larger sample size and a wider range of patients. Therefore, this increases the difficulty of quality control in clinical practices. With the experience in quality control in clinical practices for the post-marketing reevaluation for Kangbingdu oral for cold, researchers in this study reviewed the study purpose, project, scheme design and clinical practice process from an overall point of view, analyzed the study characteristics of the post-marketing reevaluation for TCMs and the quality control risks, designed the quality control contents with quality impacting factors, defined key review contents and summarized the precautions in clinical practices, with the aim to improve the efficiency of quality control of clinical practices. This study can provide reference to clinical units and quality control-related personnel in the post-marketing reevaluation for TCMs.

  10. 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

    ... January 7, 2013. Issued on: November 26, 2012. Richard Doucette, Environmental Program Manager, Airports... Federal Aviation Administration Draft Written Re-Evaluation for Environmental Impact Statement: T.F. Green Airport, Warwick, RI AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of...

  11. 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 Runway 9R-27L and Associated Projects at the Fort Lauderdale-Hollywood International Airport AGENCY... Expansion of Runway 9R-27L and Associated Projects at the Fort Lauderdale-Hollywood International...

  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

    ... Environmental Impact Statement for the Relocation of the Panama City-Bay County International Airport (2006..., Environmental Protection Specialist, Federal Aviation Administration, Orlando Airports District Office, 5950... Federal Aviation Administration Written Re-Evaluation and Record of Decision for the Final...

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

    USDA-ARS?s Scientific Manuscript database

    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...

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. Functional Films from Silica/Polymer Nanoparticles

    PubMed Central

    Ribeiro, Tânia; Baleizão, Carlos; Farinha, José Paulo S.

    2014-01-01

    High performance functional coatings, based on hybrid organic/inorganic materials, are being developed to combine the polymer flexibility and ease of processing with the mechanical properties and versatility of inorganic materials. By incorporating silica nanoparticles (SiNPs) in the polymeric matrices, it is possible to obtain hybrid polymer films with increased tensile strength and impact resistance, without decreasing the flexural properties of the polymer matrix. The SiNPs can further be used as carriers to impart other functionalities (optical, etc.) to the hybrid films. By using polymer-coated SiNPs, it is possible to reduce particle aggregation in the films and, thus, achieve more homogeneous distributions of the inorganic components and, therefore, better properties. On the other hand, by coating polymer particles with silica, one can create hierarchically structured materials, for example to obtain superhydrophobic coatings. In this review, we will cover the latest developments in films prepared from hybrid polymer/silica functional systems. PMID:28788655

  19. Silica enhancement of murine endotoxin sensitivity.

    PubMed

    Vogel, S N; English, K E; O'Brien, A D

    1982-11-01

    Silica has been used for many years as an agent which selectively alters macrophage functions and, as such, has been used to assess the role of macrophages in the immune response to a variety of microbial and chemically defined agents. Silica treatment of C3H/HeN mice 1 day before challenge with protein-free Escherichia coli endotoxin (lipopolysaccharide [LPS]) resulted in a marked increase in LPS sensitivity, as evidenced by accelerated signs of endotoxemia as well as a fourfold decrease in the LPS 50% lethal dose. The silica-mediated increase in responsiveness to LPS was associated with increased production of macrophage-derived soluble factors both in vivo (interferon) and in vitro (Interleukin 1; previously referred to as lymphocyte activating factor or LAF) upon endotoxin stimulation. These findings support the central role of the macrophage and its products in mediating endotoxic reactions.

  20. High resolution patterning of silica aerogels

    SciTech Connect

    Bertino, M.F.; Hund, J.F.; Sosa, J.; Zhang, G.; Sotiriou-Leventis, C.; Leventis, N.; Tokuhiro, A.T.; Terry, J.

    2008-10-30

    Three-dimensional metallic structures are fabricated with high spatial resolution in silica aerogels. In our method, silica hydrogels are prepared with a standard base-catalyzed route, and exchanged with an aqueous solution typically containing Ag{sup +} ions (1 M) and 2-propanol (0.2 M). The metal ions are reduced photolytically with a table-top ultraviolet lamp, or radiolytically, with a focused X-ray beam. We fabricated dots and lines as small as 30 x 70 {micro}m, protruding for several mm into the bulk of the materials. The hydrogels are eventually supercritically dried to yield aerogels, without any measurable change in the shape and spatial resolution of the lithographed structures. Transmission electron microscopy shows that illuminated regions are composed by Ag clusters with a size of several {micro}m, separated by thin layers of silica.

  1. Thermal resistance between amorphous silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Meng, Fanhe; Elsahati, Muftah; Liu, Jin; Richards, Robert F.

    2017-05-01

    Nanoparticle-based materials have been used as thermal insulation in a variety of macroscale and microscale applications. In this work, we investigate the heat transfer between nanoparticles using non-equilibrium molecular dynamics simulations. We calculate the total thermal resistance and thermal boundary resistance between adjacent amorphous silica nanoparticles. Numerical results are compared to interparticle resistances determined from experimental measurements of heat transfer across packed silica nanoparticle beds. The thermal resistance between nanoparticles is shown to increase rapidly as the particle contact radius decreases. More significantly, the interparticle resistance depends strongly on the forces between particles, in particular, the presence or absence of chemical bonds between nanoparticles. In addition, the effect of interfacial force strength on thermal resistance increases as the nanoparticle diameter decreases. The simulations results are shown to be in good agreement with experimental results for 20 nm silica nanoparticles.

  2. Fullerene-silica complexes for medical chemistry

    NASA Astrophysics Data System (ADS)

    Sheka, E. F.

    2007-06-01

    A quantum-chemical study of the interaction of C60 fullerene with nanosized silica was performed. It was demonstrated that a fullerene molecule forms a weakly bound complex with a pyrogenic silica (Aerosil) particle only via the interaction with the silanediol groups of the hydroxyl covering on the particle. By contrast, a fullerene molecule is not bonded to an individual siloxane cycle, and, therefore, fullerosilica gel is formed due to the retention of fullerene molecules in pores of silica gel as a result cooperative action of the siloxane cycles comprising the pore. In both cases, the predicted medico-biological action of medicinal preparations is due to the radical-like and donor-acceptor characteristics of the C60 molecule.

  3. Cellular complexity captured in durable silica biocomposites

    PubMed Central

    Kaehr, Bryan; Townson, Jason L.; Kalinich, Robin M.; Awad, Yasmine H.; Swartzentruber, B. S.; Dunphy, Darren R.; Brinker, C. Jeffrey

    2012-01-01

    Tissue-derived cultured cells exhibit a remarkable range of morphological features in vitro, depending on phenotypic expression and environmental interactions. Translation of these cellular architectures into inorganic materials would provide routes to generate hierarchical nanomaterials with stabilized structures and functions. Here, we describe the fabrication of cell/silica composites (CSCs) and their conversion to silica replicas using mammalian cells as scaffolds to direct complex structure formation. Under mildly acidic solution conditions, silica deposition is restricted to the molecularly crowded cellular template. Inter- and intracellular heterogeneity from the nano- to macroscale is captured and dimensionally preserved in CSCs following drying and subjection to extreme temperatures allowing, for instance, size and shape preserving pyrolysis of cellular architectures to form conductive carbon replicas. The structural and behavioral malleability of the starting material (cultured cells) provides opportunities to develop robust and economical biocomposites with programmed structures and functions. PMID:23045634

  4. 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.

  5. 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.

  6. 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.

  7. Morphology and surface properties of fumed silicas.

    PubMed

    Gun'ko, V M; Mironyuk, I F; Zarko, V I; Voronin, E F; Turov, V V; Pakhlov, E M; Goncharuk, E V; Nychiporuk, Y M; Vlasova, N N; Gorbik, P P; Mishchuk, O A; Chuiko, A A; Kulik, T V; Palyanytsya, B B; Pakhovchishin, S V; Skubiszewska-Zieba, J; Janusz, W; Turov, A V; Leboda, R

    2005-09-15

    Several series of fumed silicas and mixed fumed oxides produced and treated under different conditions were studied in gaseous and liquid media using nitrogen and water adsorption-desorption, mass spectrometry, FTIR, NMR, thermally stimulated depolarization current (TSDC), photon correlation spectroscopy (PCS), zeta potential, potentiometric titration, and Auger electron spectroscopy methods. Aggregation of primary particles and adsorption capacity (Vp) decrease and hysteresis loops of nitrogen adsorption-desorption isotherms becomes shorter with decreasing specific surface area (S(BET)). However, the shape of nitrogen adsorption-desorption isotherms can be assigned to the same type independent of S(BET) value. The main maximum of pore size distribution (gaps between primary nonporous particles in aggregates and agglomerates) shifts toward larger pore size and its intensity decreases with decreasing S(BET) value. The water adsorption increases with increasing S(BET) value; however, the opposite effect is observed for the content of surface hydroxyls (in mmol/m2). Associative desorption of water (2(SiOH)-->SiOSi+H2O) depends on both the morphology and synthesis conditions of fumed silica. The silica dissolution rate increases with increasing S(BET) and pH values. However, surface charge density and the modulus of zeta-potential increase with decreasing S(BET) value. The PCS, 1H NMR, and TSDC spectra demonstrate rearrangement of the fumed silica dispersion depending on the S(BET) value and the silica concentration (C(SiO2)) in the aqueous suspensions. A specific state of the dispersion is observed at the C(SiO2) values corresponding to the bulk density of the initial silica powder.

  8. 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.

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

    SciTech Connect

    Datskos, Panos; Chen, Jihua; Sharma, Jaswinder

    2014-01-01

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

  10. 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.

  11. Transmitting and reflecting diffuser. [using ultraviolet grade fused silica coatings

    NASA Technical Reports Server (NTRS)

    Keafer, L. S., Jr.; Burcher, E. E.; Kopia, L. P. (Inventor)

    1977-01-01

    An ultraviolet grade fused silica substrate is coated with vaporized fused silica. The coating thickness is controlled, one thickness causing ultraviolet light to diffuse and another thickness causing ultraviolet light to reflect a near Lambertian pattern.

  12. Synthesis and Application of Metal-Containing Silicas

    NASA Astrophysics Data System (ADS)

    Katok, K.; Tertykh, V.; Yanishpolskii, V.

    Gold nanoparticles were obtained by in situ reduction with silicon hydride groups grafted to the silochrom C-120 and aerosil A-300 silica surface. Such gold-containing silicas have been applied for hydrogen oxidation.

  13. Ecodesign of ordered mesoporous silica materials.

    PubMed

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

    2013-05-07

    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.

  14. 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.

  15. Thermal pretreatment of silica composite filler materials

    PubMed Central

    Wan, Quan; Ramsey, Christopher

    2010-01-01

    Three different silica filler materials were thermally treated in order to effect dehydration, dehydroxylation, and rehydroxylation. Samples were characterized by thermogravimetry (TG), pycnometry, elemental analysis, and scanning electron microscopy (SEM). For all fillers, our results indicate incremental removal of silanol groups at higher heating temperatures and irreversible dehydroxylation at over 673 K. To remove the organic content and maintain adequate silanol density for subsequent silanization on Stöber-type silica, we suggest heating at 673 K followed by overnight boiling in water. PMID:20445821

  16. 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.}

  17. Devitrification and shrinkage behavior of silica fibers

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, I.

    1972-01-01

    Devitrification and shrinkage of three batches of silica fibers were investigated in the temperature range of 1200 to 1350 C. Fibers with high water and impurity content devitrified rapidly to cristobalite and quartz and exhibited rapid, but the least amount of, shrinkage. A batch with low water and impurity content devitrified more slowly to cristobalite only and underwent severe shrinkage by the mechanism of viscous flow. A third batch of intermediate purity level and low water content devitrified at a moderate rate mainly to cristobalite but shrunk very rapidly. Completely devitrified silica fibers did not exhibit any further shrinkage.

  18. Facile phenylboronate modification of silica by a silaneboronate.

    PubMed

    Pelton, Robert; Cui, Yuguo; Zhang, Dan; Chen, Yang; Thompson, Kate L; Armes, Steven P; Brook, Michael A

    2013-01-15

    Macroscopic and colloidal silica surfaces were readily modified with alkoxysilaneboronate, IV, yielding silica surfaces with covalently bonded phenylboronic acid groups. XPS and neutron activation confirmed the presence of boron. The ability of these surfaces to specifically interact with polyols was demonstrated with polyol-coated latex and ARS, a dye that specifically couples to boronic acid groups immobilized on colloidal or macroscopic silica. This is a new, direct approach for introduction of phenylboronic acid groups onto silica surfaces.

  19. Physicochemical properties of the surfaces of silica species

    NASA Astrophysics Data System (ADS)

    Roshchina, T. M.; Shoniya, N. K.; Tegina, O. Ya.; Tkachenko, O. P.; Kustov, L. M.

    2017-02-01

    The results from studying the physicochemical characteristics of the adsorption of n-alkanes, arenes, and acetonitrile on silicas of different origins, silica gels, and silochromes are presented. It is shown that increasing the concentration of silanol groups reduces the role of dispersion interactions accompanied by the intensification of specific interactions on silica gels, compared to silochromes. According to diffuse reflectance FTIR spectroscopy data, the acidity of silanol groups on silica gel is in this case less pronounced.

  20. 78 FR 3449 - Silica Bricks and Shapes From China

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-16

    ... 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 Tariff... injury by reason of LTFV imports of silica bricks and shapes from China. Accordingly, effective November...

  1. 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...

  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. 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.

  4. The synthesis, full characterisation and utilisation of template-free silica sodalite, a novel polymorph of silica.

    PubMed

    King, R S P; Dann, S E; Elsegood, M R J; Kelly, P F; Mortimer, R J

    2009-01-01

    Empty glass: Subjecting ethylene glycol silica sodalite to heat (680 degrees C) under a nitrogen atmosphere (i) successfully removes the templating agent to give cubic silica sodalite, which, upon consequent heating under an oxygen atmosphere (ii), transforms into a rhombohedral form of the empty sodalite, in effect a novel polymorph of silica.

  5. Microbial silica deposition in geothermal hot waters.

    PubMed

    Inagaki, F; Motomura, Y; Ogata, S

    2003-02-01

    A combined use of molecular ecological techniques and geochemical surveys revealed that thermophilic or hyperthermophilic microorganisms living in geothermal environments are likely to be implicated in the formation of biogenic siliceous deposits. Electron microscopic observations indicated that numerous microorganism-like fabrics were preserved in naturally occurring siliceous deposits such as siliceous sinter, geyserite, and silica scale, which suggests microbial contribution to silica precipitation. Molecular phylogenetic analyses suggested that extreme thermophilic bacteria within the genera Thermus and Hydrogenobacter are predominant components among the indigenous microbial community in siliceous deposits formed in pipes and equipment of Japanese geothermal power plants. These bacteria seem to actively contribute to the rapid formation of huge siliceous deposits. Additionally, in vitro examination suggested that Thermus cells induced the precipitation of supersaturated amorphous silica during the exponential growth phase, concomitant with the production of a specific cell envelope protein. Dissolved silica in geothermal hot water may be a significant component in the maintenance of position and survival of microorganisms in limited niches.

  6. 21 CFR 584.700 - Hydrophobic silicas.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE IN FEED AND...

  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. Fluorescent silica nanoparticles for cancer imaging.

    PubMed

    Santra, Swadeshmukul

    2010-01-01

    In recent years, fluorescent silica nanoparticles (FSNPs) received immense interest in cancer imaging. FSNPs are a new class of engineered optical probes consisting of silica NPs loaded with fluorescent dye molecules. These probes exhibit some attractive features, such as photostability and brightness, which allow sensitive imaging of cancer cells. In general, FSNPs are chemically synthesized in solution using appropriate silane-based precursors. Fluorescent dye molecules are entrapped during the synthesis process. The synthetic process involves hydrolysis and condensation reactions of silane precursors. Stöber's sol-gel and water-in-oil (W/O) microemulsion methods are two popular chemical methods that have been used for synthesizing FSNPs. Silica matrix is capable of carrying hundreds of fluorescent dye molecules in each FSNP, resulting in bright fluorescence. In FSNPs, fluorescent molecules are somewhat protected by the surrounding silica layer, resulting in good photostability. For cancer cell imaging, surface modification of FSNPs is often necessary to obtain appropriate surface functional groups to improve NP aqueous dispersibility as well as bioconjugation capability. Using conventional bioconjugate chemistry, cancer cell-specific biomolecules are then attached to the surface-modified FSNPs. For targeting cancer cells, the FSNPs are often conjugated to specific biomolecules such as antibodies, aptamers, and folic acid. In this chapter, different approaches for the FSNP design will be discussed and some representative protocols for FSNP synthesis will be provided. We will also discuss FSNP surface modification and bioconjugation techniques that are useful for cancer cell imaging.

  9. Optical properties of polyimide/silica nanocomposite

    NASA Astrophysics Data System (ADS)

    Tommalieh, M. J.; Zihlif, A. M.

    2010-12-01

    The optical properties of thin films of polyimide/silica nanocomposites prepared via sol-gel process were investigated as a function of nanosilica particles content. Absorption and reflectance spectra were collected by a spectrophotometer giving UV-radiation of wavelength range 200-800 nm. The optical data obtained were analyzed in terms of absorption formula for non-crystalline materials. The calculated values of the optical energy gap and the width of the energy tails of the localized states exhibited silica concentration dependence. The direct optical energy gap for neat polyimide is about 1.95 eV, and decreases to a value of 1.8 eV for nanocomposite of 25 wt% nanosilica content. It was found that the calculated refractive index and dielectric constants of nanocomposites increase with silica particles content. The overall dependence of the optical and dielectrical constants on silica content in polyimide matrix is argued on the basis of the observed morphology and overlap of the localized energy sates of different color centers. The EMT model was fitted to the observed dielectric data.

  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. Relaxation processes of densified silica glass

    NASA Astrophysics Data System (ADS)

    Cornet, Antoine; Martinez, Valérie; de Ligny, Dominique; Champagnon, Bernard; Martinet, Christine

    2017-03-01

    Densified SiO2 glasses, obtained from different pressure and temperature routes, have been annealed over a wide range of temperatures far below the glass transition temperature (500 °C-900 °C). Hot and cold compressions were useful to separate the effects of pressure and the compression temperature. In situ micro-Raman spectroscopy was used to follow the structural evolution during the thermal relaxation. A similar glass structure between the non-densified silica and the recovered densified silica after the temperature annealing demonstrates a perfect recovery of the non-densified silica glass structure. While the density decreases monotonically, the structural relaxation takes place through a more complex mechanism, which shows that density is not a sufficient parameter to fully characterize the structure of densified silica glass. The relaxation takes place through a transitory state, consisting in an increase of the network inhomogeneity, shown by an increase in the intensity of the D2 band which is associated with 3 membered rings. The activation energy of these processes is 255 ± 45 kJ/mol for the hot compressed samples. The kinetic is overall faster for the cold compressed samples. In that last case, the relaxation is partially activated by internal stresses release.

  13. Immobilization of bacteriophages on modified silica particles.

    PubMed

    Cademartiri, Rebecca; Anany, Hany; Gross, Isabelle; Bhayani, Rahul; Griffiths, Mansel; Brook, Michael A

    2010-03-01

    Bacteriophages are selective anti-bacterial agents, which are receiving increasing acceptance by regulatory agencies for use both in the food industry and in clinical settings for biocontrol. While immobilized phage could be particularly useful to create antimicrobial surfaces, current immobilization strategies require chemical bioconjugation to surfaces or more difficult processes involving modification of their head proteins to express specific binding moieties, for example, biotin or cellulose binding domains; procedures that are both time and money intensive. We report that morphologically different bacteriophages, active against a variety of food-borne bacteria: Escherichia coli; Salmonella enterica; Listeria monocytogenes; and Shigella boydii, will effectively physisorb to silica particles, prepared by silica surface modification with poly(ethylene glycol), carboxylic acid groups, or amines. The phages remain infective to their host bacteria while adsorbed on the surface of the silica particles. The number of infective phage bound to the silica is enhanced by the presence of ionic surfaces, with greater surface charge - to a maximum - correlating with greater concentration of adsorbed phage. Above the maximum charge concentration, the number of active phage drops.

  14. Mechanism of mechanical fatigue of silica glass

    SciTech Connect

    Tomozawa, Minoru.

    1990-01-01

    Research continued on the mechanism of mechanical fatigue of silica glass. Significant accomplishments this quarter include: strength increase of abraded glasses by thermal and chemical treatments was found best explained by crack tip blunting; fatigue was found to involve crack initiation in addition to crack propagation, and only water and ammonia were found capable of causing crack initiation from blunt crack tips at sub-critical stresses; water was found to enter into silica glass during microhardness indentation as well as during slow crack growth in water-containing atmospheres at room temperature; water diffusion at low temperature showed anomalous phenomena including initial time dependences of solubility and apparent diffusion coefficient; glass containing water showed greater fatigue susceptibility and lower crack initiation stress than dry glass; fatigue of abraded silica glass showed effects of cyclic stress when tested by the rotation bending method while no cyclic stress effect was observed in reciprocal bending; and a new coating which can reduce fatigue of silica glass was developed.

  15. 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.

  16. 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 Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) SUBSTANCES GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances §...

  17. 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.

  18. 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.

  19. Transport in Thermally Grown Silica on Silicon.

    DTIC Science & Technology

    1980-01-01

    catalyze the crvstallization of amorphous silica to cristobalite . 4 "" rhc activation ener- 4ies for oxidation when cristobalite forms increase but...categories. These are 65 kcal (due to formation of cristobalite ); " 40 kcal (in dry oxygen); and 30 kcal or less (in moist oxygen). S TU’ARY Based on

  20. Mesoporous silica coated silica-titania spherical particles: from impregnation to core-shell formation.

    PubMed

    Shiba, Kota; Takei, Toshiaki; Ogawa, Makoto

    2016-11-22

    The coating of solid surfaces with inorganic materials is a promising approach not only to impart various functionalities but also to modify physicochemical properties that are affected by the geometry/structure of the coating. In this study, a silica-hexadecyltrimethylammonium (silica-CTA) hybrid layer was deposited on monodispersed spherical particles composed of titania and octadecylamine (titania-ODA) by a sol-gel reaction of tetraethoxysilane in aqueous CTA/ammonia/methanol solution. The formation of the coating was confirmed by SEM and TEM observations. The coating thickness varied from a few nm to 100 nm depending on the Si/Ti ratio. We found that Si/Ti = 0.68 resulted in the formation of microporous silica-titania particles with the pore size of 0.7 nm as revealed by nitrogen adsorption/desorption measurements. Because the titania-ODA particles can be converted to mesoporous titania particles after removing ODA by acid/base treatment, the silica species can be impregnated into the titania particles and replace ODA under basic conditions. By increasing the Si/Ti molar ratio up to 1.4, silica-titania particles with non-porous structures were obtained. An amorphous to anatase transition occurred at around 800 °C, indicating the complete impregnation of silica inside the titania particles. Further increases of the Si/Ti molar ratio (to 3.4 and 6.8) led to the formation of the silica-CTA shell on the core particles, and the shell was converted to mesoporous silica layers with a pore size of 2 nm after calcination at 550 °C for 5 h. Non-linear control of the pore size/structure is presented for the first time; this will be useful for the precise design of diverse hybrid materials for optical, catalytic and biomedical applications.

  1. 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

  2. Mathematical Modelling of Silica Scaling Deposition in Geothermal Wells

    NASA Astrophysics Data System (ADS)

    Nizami, M.; Sutopo

    2016-09-01

    Silica scaling is widely encountered in geothermal wells in which produce two-phase geothermal fluid. Silica scaling could be formed due to chemical reacting by mixing a geothermal fluid with other geothermal fluid in different compositions, or also can be caused by changes in fluid properties due to changes pressure and temperature. One of method to overcome silica scaling which is occurred around geothermal well is by workover operation. Modelling of silica deposition in porous medium has been modeled in previously. However, the growth of silica scaling deposition in geothermal wells has never been modeled. Modelling of silica deposition through geothermal is important aspects to determine depth of silica scaling growth and best placing for workover device to clean silica scaling. This study is attempted to develop mathematical models for predicting silica scaling through geothermal wells. The mathematical model is developed by integrating the solubility-temperature correlation and two-phase pressure drop coupled wellbore fluid temperature correlation in a production well. The coupled model of two-phase pressure drop and wellbore fluid temperature correlation which is used in this paper is Hasan-Kabir correlation. This modelling is divided into two categories: single and two phase fluid model. Modelling of silica deposition is constrained in temperature distribution effect through geothermal wells by solubility correlation for silica. The results of this study are visualizing the growth of silica scaling thickness through geothermal wells in each segment of depth. Sensitivity analysis is applied in several parameters, such as: bottom-hole pressure, temperature, and silica concentrations. Temperature is most impact factor for silica scaling through geothermal wellbore and depth of flash point. In flash point, silica scaling thickness has reached maximum because reducing of mole in liquid portion.

  3. [Genetic tests and clinical re-evaluation of 85 children with suspected spinal muscular atrophy].

    PubMed

    Ji, Xing; Liu, Xiao-qing; Shen, Jia-wei; Li, Xi-hua; Tao, Jiong

    2010-06-01

    Spinal muscular atrophy (SMA), characterized by degeneration of the anterior horn cells in the spinal cord and symmetric proximal muscle weakness, is the most common autosomal recessive neuromuscular disease in infants and children. In Caucasian population, about 95% of clinically typical patients lack both copies of the telomeric survival motor neuron gene (SMN 1). However, the detection rate of the homozygous absence in Chinese patients is still controversial, which may lead to reduced confidence in the SMA genetic testing in clinical practice. The purpose of the current study was to determine the frequency of homozygous deletions of SMN 1 in Chinese patients, to evaluate the significance of the SMN 1 homozygous deletion assay in clinical applications, and the impact of the clinical re-visit followed by the genetic testing. Totally 85 patients initially suspected of SMA were referred for SMA genetic testing. A polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) assay was used to detect the homozygous absence of SMN 1. Clinical re-visit was performed by the pediatric neurology specialists according to the international SMA diagnostic criteria, and histological examinations were carried out when they were necessary. Absence of both copies of SMN 1 exon 7 were found in 57 (67%) of the 85 patients, and 28 patients (33%) had at least one copy. For the 28 patients with negative results, 19 were followed up by the pediatric neurologists. The clinical diagnosis of SMA could be excluded in 15 patients, but retained in the other 4 patients after the clinical re-evaluation and histological examinations. Thus, approximately 95% of the patients with clinically typical SMA in our cohort lacked both copies of SMN 1. Homozygous deletions of SMN 1 were detected in 96% (22/23), 93% (28/30) and 100% (7/7) of the patients with SMA type I, type II and type III, respectively. There was no significant difference in the deletion frequency among the subtypes

  4. 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.

  5. 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.

  6. Non-destructively shattered mesoporous silica for protein drug delivery

    SciTech Connect

    Lei, Chenghong; Chen, Baowei; Li, Xiaolin; Qi, Wen N.; Liu, Jun

    2013-07-15

    Mesoporous silicas have been extensively used for entrapping small chemical molecules and biomacromolecules. We hypothesize that the loading density of biomacromlecules such as proteins in mesoporous silicas could be limited due to mesopore disorderness and depth because of some pore volume inaccessible. We innovatively shattered mesoporous silicas resulting in reduced particle sizes and improved intramesoporous structures in aqueous solution by a powerful sonication, where the mesoporous structures were still well maintained. The sonication-shattered mesoporous silicas can allow protein loading densities to be increased by more than 170%, demonstrating that significantly more mesoporous room of the silicas could become accessible for biomacromolecule loading after the sonication-shattering.

  7. Silica scaling in forward osmosis: From solution to membrane interface.

    PubMed

    Xie, Ming; Gray, Stephen R

    2017-01-01

    Membrane silica scaling hinders sustainable water production. Understanding silica scaling mechanisms provides options for better membrane process management. In this study, we elucidated silica scaling mechanisms on an asymmetric cellulose triacetate (CTA) membrane and polyamide thin-film composite (TFC) membrane. Scaling filtration showed that TFC membrane was subjected to more severe water flux decline in comparison with the CTA membrane, together with different scaling layer morphology. To elucidate the silica scaling mechanisms, silica species in the aqueous solution were characterised by mass spectrometry as well as light scattering. Key thermodynamic parameters of silica surface nucleation on the CTA and TFC membranes were estimated to compare the surface nucleation energy barrier. In addition, high resolution X-ray photoelectron spectroscopy resolved the chemical origin of the silica-membrane interaction via identifying the specific silicon bonds. These results strongly support that silica scaling in the CTA membrane was driven by the aggregation of mono-silicic acid into large silica aggregates, followed by the deposition from bulk solution onto the membrane surface; by contrast, silica polymerised on the TFC membrane surface where mono-silicic acid interacted with TFC membrane surface, which was followed by silica surface polymerisation.

  8. 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.

  9. Incorporation of anti-inflammatory agent into mesoporous silica.

    PubMed

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

    2016-09-23

    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.

  10. 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.

  11. Adsorption of DNA onto Polypyrrole-Silica Nanocomposites

    PubMed

    Saoudi; Jammul; Chehimi; McCarthy; Armes

    1997-08-01

    DNA adsorption onto polypyrrole (PPy) powder, a colloidal silica sol, and three polypyrrole-silica nanocomposite particles (untreated and amine- or carboxylic acid-functionalized) was investigated at neutral pH using sodium phosphate buffer. The extent of DNA adsorption was found to be 32 and 22 mg/g for the aminated silica sol and aminated PPy-silica particles respectively, and 6.5 mg/g for the carboxylated particles. DNA adsorption onto the unfunctionalized PPy-silica particles occurs to a lesser extent, whereas no adsorption was detected for the colloidal silica sol. Our results suggest that DNA adsorption is mainly governed by electrostatic and hydrophobic interactions. DNA is adsorbed onto polypyrrole chloride bulk powder and also onto the aminated PPy-silica particles, which both have cationic binding sites. The silica sol and the unfunctionalized PPy-silica particles both possess a net negative surface charge at this pH, which probably accounts for the zero or very low adsorbed amounts of DNA on these substrates. DNA adsorption onto the carboxylated PPy-silica particles may be enhanced by hydrogen bonding relative to the unfunctionalized polypyrrole-silica particles.

  12. Silica-based integrated optic components for telecommunications applications

    NASA Astrophysics Data System (ADS)

    Allen, James J.; Shipley, Simon P.; Nourshargh, Noorallah

    1993-05-01

    Waveguide devices have been produced comprising germania-doped silica cores and silica claddings on silica substrates, using microwave plasma assisted chemical vapor deposition and reactive-ion etching. This all-silica structure offers the maximum compatibility between fibers and waveguides in terms of both optical and physical properties. The all-silica philosophy is extended to the use of laser-cut silica V grooves in the construction of input/output fiber arrays. An important features of this approach is that it enables fiber/waveguide interfacing by CO2 laser welding of the respective silica blocks without the introduction of any significant additional loss. Both the waveguide fabrication and laser-welding processes are well suited to large-scale production of low-cost components.

  13. 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.

  14. Aminated hollow silica spheres for electrochemical DNA biosensor

    NASA Astrophysics Data System (ADS)

    Ariffin, Eda Yuhana; Heng, Lee Yook; Futra, Dedi; Ling, Tan Ling

    2015-09-01

    An electrochemical DNA biosensor for e.coli determination based on aminated hollow silica was successfully developed. Aminated hollow silica spheres were prepared through the reaction of Tween 20 template and silica precursor. The template was removed by the thermal decomposition at 620°C. Hollow silica spheres were modified with (3-Aminopropyl) triethoxysilane (APTS) to form aminated hollow silica spheres.Aminated DNA probe were covalently immobilized on to the amine functionalized hollow silica spheres through glutaradehyde linkers. The formation hollow silica was characterized using FTIR and FESEM. A range of 50-300nm particle size obtained from FESEM micrograph. Meanwhile for the electrochemical study, a quasi-reversible system has been obtain via cyclic voltammetry (CV).

  15. 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.

  16. Spherical ordered mesoporous silicas and silica monoliths as stationary phases for liquid chromatography.

    PubMed

    Galarneau, Anne; Iapichella, Julien; Brunel, Daniel; Fajula, François; Bayram-Hahn, Zöfre; Unger, Klaus; Puy, Guillaume; Demesmay, Claire; Rocca, Jean-Louis

    2006-04-01

    Ordered mesoporous silicas such as micelle-templated silicas (MTS) feature unique textural properties in addition to their high surface area (approximately 1000 m2/g): narrow mesopore size distributions and controlled pore connectivity. These characteristics are highly relevant to chromatographic applications for resistance to mass transfer, which has never been studied in chromatography because of the absence of model materials such as MTS. Their synthesis is based on unique self-assembly processes between surfactants and silica. In order to take advantage of the perfectly adjustable texture of MTS in chromatographic applications, their particle morphology has to be tailored at the micrometer scale. We developed a synthesis strategy to control the particle morphology of MTS using the concept of pseudomorphic transformation. Pseudomorphism was recognized in the mineral world to gain a mineral that presents a morphology not related to its crystallographic symmetry group. Pseudomorphic transformations have been applied to amorphous spherical silica particles usually used in chromatography as stationary phases to produce MTS with the same morphology, using alkaline solution to dissolve progressively and locally silica and reprecipitate it around surfactant micelles into ordered MTS structures. Spherical beads of MTS with hexagonal and cubic symmetries have been synthesized and successfully used in HPLC in fast separation processes. MTS with a highly connected structure (cubic symmetry), uniform pores with a diameter larger than 6 nm in the form of particles of 5 microm could compete with monolithic silica columns. Monolithic columns are receiving strong interest and represent a milestone in the area of fast separation. Their synthesis is a sol-gel process based on phase separation between silica and water, which is assisted by the presence of polymers. The control of the synthesis of monolithic silica has been systematically explored. Because of unresolved yet

  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 of skin-explant model in graft-versus-host disease prediction.

    PubMed

    Sahin, S; Akoğlu, T F; Gürbüz, O; Ergun, T; Küllü, S; Sav, A; Ahiskali, R; Tüzüner, N; Doğusoy, G

    1995-10-01

    An in vitro skin explant model has been proposed for prediction of graft versus host disease and reported to be highly sensitive and specific for this purpose. In this study we have re-evaluated this model in both HLA full-matched BMT recipient-donor sibling pairs and also in HLA one haplotype-matched parent-children pairs. All assessments were made blindly by 3 independent observers. The predictive value of the test for the occurrence of clinical GvHD in 14 BMT patients was found to be less sensitive than reported previously (correlation coefficients were +0.019, +0.067 and -0.061 between clinical GvHD and in vitro primed allogeneic, primed mixed and unprimed allogeneic settings, indicating "poor" correlation). False positive and false negative results were high and there were also significant discrepancies between three blind observations in the grading of skin changes. Weighted kappa analysis revealed that there were "fair" correlations between the 3 observers (K = 0.25). These results indicated that the skin explant model is an unpredictable test system and there are great problems in standardization of the method.

  19. A re-evaluation of PETROTOX for predicting acute and chronic toxicity of petroleum substances.

    PubMed

    Redman, Aaron D; Parkerton, Thomas F; Leon Paumen, Miriam; Butler, Josh D; Letinski, Daniel J; den Haan, Klass

    2017-08-01

    The PETROTOX model was developed to perform aquatic hazard assessment of petroleum substances based on substance composition. The model relies on the hydrocarbon block method, which is widely used for conducting petroleum substance risk assessments providing further justification for evaluating model performance. Previous work described this model and provided a preliminary calibration and validation using acute toxicity data for limited petroleum substance. The objective of the present study was to re-evaluate PETROTOX using expanded data covering both acute and chronic toxicity endpoints on invertebrates, algae, and fish for a wider range of petroleum substances. The results indicated that recalibration of 2 model parameters was required, namely, the algal critical target lipid body burden and the log octanol-water partition coefficient (KOW ) limit, used to account for reduced bioavailability of hydrophobic constituents. Acute predictions from the updated model were compared with observed toxicity data and found to generally be within a factor of 3 for algae and invertebrates but overestimated fish toxicity. Chronic predictions were generally within a factor of 5 of empirical data. Furthermore, PETROTOX predicted acute and chronic hazard classifications that were consistent or conservative in 93 and 84% of comparisons, respectively. The PETROTOX model is considered suitable for the purpose of characterizing petroleum substance hazard in substance classification and risk assessments. Environ Toxicol Chem 2017;36:2245-2252. © 2017 SETAC. © 2017 SETAC.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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." PsycINFO Database Record (c) 2013 APA, all rights reserved.

  5. 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

  6. Reevaluation of Antioxidative Strategies for Birth Defect Prevention in Diabetic Pregnancies.

    PubMed

    Zhao, Zhiyong

    2016-09-01

    Diabetes mellitus in early pregnancy is the most severe maternal disease that is counted for 10% of newborn infants with structural defects. With the rapid increases in the number of diabetic women in childbearing age, the birth defect rate is projected to elevate dramatically. Thus, prevention of embryonic malformations becomes an urgent task. Animal studies have revealed an involvement of oxidative stress in diabetic embryopathy and treatment with antioxidants can reduce embryonic abnormalities. However, the failure of clinical trials using free radical-scavenging antioxidants to alleviate oxidative stress-related diseases prompts researchers to reevaluate the strategy in birth defect prevention. Hyperglycemia also disturbs other intracellular homeostasis, generating aberrant conditions. Perturbed folding of newly synthesized proteins causes accumulation of unfolded and misfolded proteins in the lumen of the endoplasmic reticulum (ER). The ER under the stress activates signaling cascades, known as unfolded protein response, to suppress cell mitosis and/or trigger apoptosis. ER stress can be ameliorated by chemical chaperones, which promote protein folding. Hyperglycemia also stimulates the expression of nitric oxide (NO) synthase 2 (NOS2) to produce high levels of NO and reactive nitrogen species and augment protein nitrosylation and nitration, resulting in nitrosative stress. Inhibition of NOS2 using inhibitors has been demonstrated to reduce embryonic malformations in diabetic animals. Therefore, targeting ER and nitrosative stress conditions using specific agents to prevent birth defects in diabetic pregnancies warrant further investigations. Simultaneously targeting multiple stress conditions using combined agents is a potentially effective and feasible approach.

  7. 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

  8. Reevaluation of thermonuclear reaction rate of 50Fe(p, 𝜸)51Co

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Ping; He, Jian-Jun; Chai, Wan-Dong; Hou, Su-Qing; Zhang, Li-Yong

    2016-11-01

    The thermonuclear rate of the 50Fe(p, 𝜸)51Co reaction in the Type I X-ray bursts (XRBs) temperature range has been reevaluated based on a recent precise mass measurement at CSRe Lanzhou, where the proton separation energy Sp = 142±77 keV has been determined firstly for the 51Co nucleus. Comparing to the previous theoretical predictions, the experimental Sp value has much smaller uncertainty. Based on the nuclear shell model and mirror nuclear structure information, we have calculated two sets of thermonuclear rates for the 50Fe(p, 𝜸)51Co reaction by utilizing the experimental Sp value. It shows that the statistical-model calculations are not ideally applicable for this reaction primarily because of the low density of low-lying excited states in 51Co. In this work, we recommend that a set of new reaction rates based on the mirror structure of 51Cr should be incorporated in future astrophysical network calculations. Supported by Natural Science Foundation of Inner Mongolia Autonomous Region of China (2013MS0916) and National Natural Science Foundation of China (11490562, 11405228)

  9. Reevaluation of the Reservoir Gas Sands of Rashidpur Gas Field: A Case Study

    NASA Astrophysics Data System (ADS)

    Eahsanul Haque, Akm; Ahmed, Nur

    2010-05-01

    Rashidpur Gas Field is located in the west of Srimongal in East Central Bangladesh. The accumulation associated with the Miocene Bhuban-Boka Bil Sandstone Reservoirs in a structural trap. The structure is about 35 km long and 7 km wide with amplitude of some 4900 ft. Rashidpur anticline is a sub-meriodinal axis, elongated, asymmetrical doubly plunging anticline which has two pay sands namely Upper Gas Sand (UGS) and Lower Gas Sand (LGS) indicated in all four wells drilled in the structure. After penetrating the shalebsection beneath LGS, drilling plan was rescheduled to a depth of 9200 ft in order to investigate the deeper sands of potential hydrocarbon accumulation. On reaching a depth of 10073 ft a sudden kick occurred, which halted the drilling operation and forced to kill the well. An immediate sidetrack well (4521 ft) was drilled at Well-4 and an existence of a sealing fault was drawn on the final report. But mud logs of Well-3 and Well-4 based on the hydrocarbon component of UGS and LGS clearly indicate the absence of any fault between Well-3 and Well-4. Recent geological investigation in the study area reveals the updated facts on the two wells of Rashidpur Gas Field. The paper analyses mud logs and other geological data and reevaluates the reservoir gas sands of Rashidpur Gas Field.

  10. Re-evaluation of focal depths and source mechanisms of selected earthquakes in the Afar depression

    NASA Astrophysics Data System (ADS)

    Hagos, L.; Shomali, H.; Roberts, R.

    2006-10-01

    We present a stepwise inversion procedure to assess the focal depth and model earthquake source complexity of seven moderate-sized earthquakes (6.2 >Mw > 5.1) that occurred in the Afar depression and the surrounding region. The Afar depression is a region of highly extended and intruded lithosphere, and zones of incipient seafloor spreading. A time-domain inversion of full moment tensor was performed to model direct P and SH waves of teleseismic data. Waveform inversion of the selected events estimated focal depths in the range of 17-22 km, deeper than previously published results. This suggests that the brittle-ductile transition zone beneath parts of the Afar depression extends more than 22 km. The effect of near-source velocity structure on the moment tensor elements was also investigated and was found to respond little to the models considered. Synthetic tests indicate that the size of the estimated, non-physical, non-isotropic source component is rather sensitive to incorrect depth estimation. The dominant double couple part of the moment tensor solutions for most of the events indicates that their occurrence is mainly due to shearing. Parameters associated with source directivity (rupture velocity and azimuth) were also investigated. Re-evaluation of the analysed events shows predominantly normal faulting consistent with the relative plate motions in the region.

  11. 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.

  12. 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.

  13. 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.

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

    PubMed

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

    2016-04-01

    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. Cross-sectional data from 2,352 adults with and without hearing impairment, ages 18-70 years, were analyzed. They completed the AIADH in the web-based prospective cohort study "Netherlands Longitudinal Study on Hearing." A graded response model was fitted to the AIADH data. Category response curves, item information curves, and the standard error as a function of self-reported hearing ability were plotted. The graded response model showed a good fit. Item information curves were most reliable for adults who reported having hearing disability and less reliable for adults with normal hearing. The standard error plot showed that self-reported hearing ability is most reliably measured for adults reporting mild up to moderate hearing disability. This is one of the few item response theory studies on audiological self-reports. All AIADH items could be hierarchically placed on the self-reported hearing ability continuum, meaning they measure the same construct. This provides a promising basis for developing a clinically useful computerized adaptive test, where item selection adapts to the hearing ability of individuals, resulting in efficient assessment of hearing disability.

  15. 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.

  16. 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.

  17. Re-evaluation of epidermodysplasia verruciformis: Reconciling more than 90 years of debate.

    PubMed

    Przybyszewska, Joanna; Zlotogorski, Abraham; Ramot, Yuval

    2017-02-10

    Epidermodysplasia verruciformis (EV) is a rare genodermatosis characterized by abnormal susceptibility to cutaneous human beta-papillomavirus infections causing persistent flat warts or pityriasis versicolor-like lesions. This generalized verrucous skin disorder resembles generalized verrucosis, but these 2 conditions are distinguished by differences in clinical manifestation and the human papillomavirus types involved. A breakthrough in our understanding of EV was the discovery that homozygous inactivating mutations in TMC6 (EVER1) and TMC8 (EVER2) determine susceptibility to this disorder; however, they have not solved all EV cases fully. These deficiencies account for 75% of affected individuals, leaving a substantial number of patients without an underlying genetic cause. Recently, it has been revealed that mutations in additional genes (RHOH, MST-1, CORO1A, and IL-7) result in extensive human beta-papillomavirus replication and therefore manifest with an EV-like phenotype. The term "acquired EV" is used to describe an EV-like phenotype that develops in immunocompromised hosts, and the introduction of this entity further aggravates the confusion. Reevaluation of these entities is warranted. Here, we review the available data on this issue, provide up to date information on the major characteristics that differentiate between these seemingly clinically similar disorders, and highlight the different mechanisms involved in each disorder.

  18. Aldrin and dieldrin: a reevaluation of the cancer and noncancer dose-response assessments.

    PubMed

    Hooker, Eric P; Fulcher, Keri G; Gibb, Herman J

    2014-05-01

    The dose-response analyses of cancer and noncancer health effects of aldrin and dieldrin were evaluated using current methodology, including benchmark dose analysis and the current U.S. Environmental Protection Agency (U.S. EPA) guidance on body weight scaling and uncertainty factors. A literature review was performed to determine the most appropriate adverse effect endpoints. Using current methodology and information, the estimated reference dose values were 0.0001 and 0.00008 mg/kg-day for aldrin and dieldrin, respectively. The estimated cancer slope factors for aldrin and dieldrin were 3.4 and 7.0 (mg/kg-day)(-1), respectively (i.e., about 5- and 2.3-fold lower risk than the 1987 U.S. EPA assessments). Because aldrin and dieldrin are no longer used as pesticides in the United States, they are presumed to be a low priority for additional review by the U.S. EPA. However, because they are persistent and still detected in environmental samples, quantitative risk assessments based on the best available methods are required. Recent epidemiologic studies do not demonstrate a causal association between aldrin and dieldrin and human cancer risk. The proposed reevaluations suggest that these two compounds pose a lower human health risk than currently reported by the U.S. EPA. © 2013 Society for Risk Analysis.

  19. Re-evaluation of the life to rupture of ductile metals by cyclic plastic strain

    NASA Astrophysics Data System (ADS)

    Kapoor, A.

    1994-02-01

    Experiments have been performed on specimens subjected to strain cycles similar to those experienced by sub-surface elements of material in rolling/sliding contact. It has been observed that if the strain cycle is closed then failure takes place by low cycle fatigue and the Coffin-Manson relationship may be used to predict the number of cycles to failure. If however, the strain cycle is open, so that the material accumulates unidirectional plastic strain (the situation known as 'ratchetting') a different type of failure, which is termed ratchetting failure may occur. It occurs when the total accumulated plastic strain reaches a critical value which is comparable with the strain to failure in a monotonic tension test. The number of cycles to failure under these circumstances may be estimated by dividing this critical strain by the ratchetting strain per cycle. It is suggested that low cycle fatigue and ratchetting are independent and competitive mechanisms so that failure occurs by whichever of them corresponds to a shorter life. The results of both uniaxial and biaxial tests reported in the literature have been re-evaluated and these, together with new data on biaxial tests on copper, found to be consistent with this hypothesis.

  20. Re-evaluation of the life to rupture of ductile metals by cyclic plastic strain

    SciTech Connect

    Kapoor, A.

    1994-02-01

    Experiments have been performed on specimens subjected to strain cycles similar to those experienced by sub-surface elements of material in rolling/sliding contact. It has been observed that if the strain cycle is closed then failure takes place by low cycle fatigue and the Coffin-Manson relationship may be used to predict the number of cycles to failure. If however, the strain cycle is open, so that the material accumulates unidirectional plastic strain (the situation known as `ratchetting`) a different type of failure, which is termed ratchetting failure may occur. It occurs when the total accumulated plastic strain reaches a critical value which is comparable with the strain to failure in a monotonic tension test. The number of cycles to failure under these circumstances may be estimated by dividing this critical strain by the ratchetting strain per cycle. It is suggested that low cycle fatigue and ratchetting are independent and competitive mechanisms so that failure occurs by whichever of them corresponds to a shorter life. The results of both uniaxial and biaxial tests reported in the literature have been re-evaluated and these, together with new data on biaxial tests on copper, found to be consistent with this hypothesis. 25 refs.

  1. How much do I give? Reevaluation of insulin dosing estimation formulas using continuous glucose monitoring.

    PubMed

    King, Allen B

    2010-01-01

    To reevaluate current formulas for determining the total basal insulin dosage (TBD), insulin to carbohydrate ratio (ICR), and correction factor (CF) from weight or total daily dosage (TDD) in pump-treated patients with type 1 diabetes mellitus. From a post hoc analysis of data from 4 previously published studies, subjects who met the inclusion criteria were selected. No subject was duplicated. For all studies, the basal glucose target was to have fewer than 20%of glucose readings greater than 170 mg/dL and to have 10% or fewer glucose readings less than 70 mg/dL. Bolus insulin was adjusted to achieve a 2- to 4-hour postbolus glucose value within 20% of the premeal glucose (ICR) or 80 to 120 mg/dL from premeal hyperglycemia (CF). In the first 2 studies, dosing titration by CGM was performed from 72-hour CGM tracings every week to every 6 weeks. In the other 2 studies, 24- to 72-hour CGM downloads and insulin adjustments were done each weekday. Of 101 participants, 61 (59% women) met the inclusion criteria. Estimation formulas could be rounded to the following: TBD = 0.2 x weight (kg) or 0.4 x TDD; ICR = 300 / TDD; and CF = 1500 / TDD. In particular the relationship between all 3 dosing factors could be represented as 100 / TBD = ICR = CF / 4.5. These results suggest that current formulas give a higher estimate for TBD and a lower estimate for the bolus dose.

  2. Time to Re-evaluate the Guideline Value for Manganese in Drinking Water?

    PubMed Central

    Ljung, Karin; Vahter, Marie

    2007-01-01

    Objective We reviewed the scientific background for the current health-based World Health Organization (WHO) guideline value for manganese in drinking water. Data sources and extraction The initial starting point was the background document for the development of the WHO’s guideline value for manganese in drinking water as well as other regulations and recommendations on manganese intake levels. Data referred to in these documents were traced back to the original research papers. In addition, we searched for scientific reports on manganese exposure and health effects. Data synthesis The current health-based guideline value for manganese in drinking water is based partly on debatable assumptions, where information from previous reports has been used without revisiting original scientific articles. Presently, preparation of common infant formulas with water containing manganese concentrations equivalent to the WHO guideline value will result in exceeding the maximum manganese concentration for infant formula. However, there are uncertainties about how this maximum value was derived. Concurrently, there is increasing evidence of negative neurologic effects in children from excessive manganese exposure. Conclusions The increasing number of studies reporting associations between neurologic symptoms and manganese exposure in infants and children, in combination with the questionable scientific background data used in setting the manganese guideline value for drinking water, certainly warrant a re-evaluation of the guideline value. Further research is needed to understand the causal relationship between manganese exposure and children’s health, and to enable an improved risk assessment. PMID:18007980

  3. Time to re-evaluate the guideline value for manganese in drinking water?

    PubMed

    Ljung, Karin; Vahter, Marie

    2007-11-01

    We reviewed the scientific background for the current health-based World Health Organization (WHO) guideline value for manganese in drinking water. The initial starting point was the background document for the development of the WHO's guideline value for manganese in drinking water as well as other regulations and recommendations on manganese intake levels. Data referred to in these documents were traced back to the original research papers. In addition, we searched for scientific reports on manganese exposure and health effects. The current health-based guideline value for manganese in drinking water is based partly on debatable assumptions, where information from previous reports has been used without revisiting original scientific articles. Presently, preparation of common infant formulas with water containing manganese concentrations equivalent to the WHO guideline value will result in exceeding the maximum manganese concentration for infant formula. However, there are uncertainties about how this maximum value was derived. Concurrently, there is increasing evidence of negative neurologic effects in children from excessive manganese exposure. The increasing number of studies reporting associations between neurologic symptoms and manganese exposure in infants and children, in combination with the questionable scientific background data used in setting the manganese guideline value for drinking water, certainly warrant a re-evaluation of the guideline value. Further research is needed to understand the causal relationship between manganese exposure and children's health, and to enable an improved risk assessment.

  4. Re-evaluation of a LEED Platinum Building: Occupant experiences of health and comfort.

    PubMed

    Dorsey, Julie; Hedge, Alan

    2017-01-01

    There is a need to better understand the perceived experiences of workers in green buildings as the literature to this point has been mixed. To re-evaluate occupant experiences within a LEED platinum building and investigate current experiences in general. An online post occupancy evaluation (POE) survey of 62 occupants of LEED Platinum building on a US college campus is reported. The online survey addressed indoor environmental quality in relation to health, productivity and satisfaction. Of the respondents, 38.7% had participated in a prior POE of this building in 2011 and results were compared for this subgroup, as well as for overall results. There was a significant increase in satisfaction with office workstations and air freshness as compared to 3 years earlier. However, there was also a significant increase in reported frequency of all physical symptoms. When looking just at the current POE results, control over features of the workstation had a significant relationship with most outcomes of interest. While improvements have been noted, issues continue to exist that have implications for health, productivity and satisfaction. The results of this study have implications for the ergonomic design of workstations and indoor environmental quality within LEED buildings.

  5. 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.

  6. Adaptively Reevaluated Bayesian Localization (ARBL): A novel technique for radiological source localization

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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. 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. 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.

  7. 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

  8. Re-evaluation of the dosimetry for reactor pressure-vessel surveillance capsules

    SciTech Connect

    Simons, R.L.; Kellogg, L.S.; Lippincott, E.P.; McElroy, W.N.; Oberg, D.L.

    1982-03-01

    Revised fluences and displacements per atom (dpa) and their uncertainties were determined after re-evaluating the neutron dosimeters from forty-one pressurized water reactor (PWR) surveillance capsules. The goals of this HEDL Reactor Dosimetry Center work are (1) to apply and test new ASTM recommended physics-dosimetry analysis methods and data being developed for LWR power plant surveillance and (2) to provide improved neutron exposure values for reactor pressure vessel steel metallurgical data bases; particularly for the changes in nil ductility transition temperature (..delta..NDTT) and upper shelf energy. Uncertainties in the FERRET-SAND adjustment Code derived neutron exposure values range from 10 to 34%. The ratio of the new to the old exposure values for fluence greater than 1 MeV varied from a low of 0.79 to a high of 2.11, with an average value of 1.30. The fission reactions for /sup 238/U and /sup 237/Np were found to be instrumental in producing low uncertainties in the exposure values (10 to 15%) whereas with their absence the uncertainty increased to 25 to 34%. Corrections for fissile impurity atoms in the /sup 238/U dosimeters were found to be as high as 29% in some cases. Other sources of corrections such as surveillance capsule perturbations and photo fission reactions have been considered.

  9. 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.

  10. 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

  11. Genotyping of Brucella melitensis by rpoB gene analysis and re-evaluation of conventional serotyping method.

    PubMed

    Sayan, Murat; Yumuk, Zeki; Bilenoglu, Onur; Erdenlig, Sevil; Willke, Ayse

    2009-03-01

    In Turkey, where brucellosis is endemic, a comparison of conventional and molecular genotyping methods has not been published to date. In this study, we investigated the efficacy of single nucleotide polymorphism (SNP) analysis of rpoB gene in the genotyping of Brucella melitensis strains by sequencing. In light of the molecular genotyping method available now in Turkey, the adequacy of serological typing alone should be re-evaluated as a tool for epidemiologic studies of B. melitensis.

  12. Self-Reevaluation and Anticipated Regret Did Not Change Attitude, Nor Perceived Distance in an Online Context

    PubMed Central

    Crutzen, Rik; Cyr, Dianne; Taylor, Sarah E.; Lim, Eric; Ruiter, Robert A. C.

    2017-01-01

    Internet-delivered interventions can be effective in changing behavior, but more research is needed on effective elements of behavior change interventions. Moreover, although anonymity is one of the advantages of using an online context, it might also increase the perceived distance between the participant and the intervention. Hence, the current study investigated whether the behavior change methods of self-reevaluation and anticipated regret can be used to narrow the perceived distance and, ultimately, foster attitude change. A 3 × 3 factorial between-persons design with an additional control group was used (N = 466), resulting in a total of 10 conditions (n's ranging from 43 to 49). The first factor manipulated is assessment of self-image; cognitive, affective, or the combination of both. The second factor manipulated is behavioral focus; self-image with behavior, without behavior or both with and without behavior. Post-test measurements were conducted immediately after the manipulation. The key finding of the current study is that the behavior change methods of self-reevaluation and anticipated regret did not have an impact on changes in attitude toward oral contraceptive use, nor on the distance perceived by participants. Despite the null results, the current study contributes to the body of evidence regarding self-reevaluation and anticipated regret, which can be integrated in meta-regressions of experimental studies to advance behavior change theory. PMID:28123373

  13. Approaches to separations using silica colloidal membranes

    NASA Astrophysics Data System (ADS)

    Ignacio-de Leon, Patricia Anne Argana

    This thesis describes the synthesis and properties of free-standing nanoporous silica colloidal membranes where the molecular transport is controlled on the basis of size, charge, and chiral selectivity. To achieve this, free-standing membranes were prepared from colloidal solutions of silica nanospheres and the nanopore size and surface functionality were varied. First, Au-coated membranes were prepared and the transport of neutral and charged small molecules through Au-coated silica colloidal membranes modified with poly(methacrylic acid) was studied. Polymer length was controlled by polymerization time to produce pH- and ion-responsive brushes inside the nanopores. By monitoring the flux of a diffusing species, it was demonstrated that the polyelectrolyte brush undergoes swelling and collapse when the pH is increased and decreased, respectively. We also observed an expansion and contraction in the absence and presence of counterions, respectively. We also studied the transport of enantiomers of a chiral dye molecule through silica colloidal membranes with attached chiral moieties. We used small molecules and polymers of amino acid derivatives and chiral calixarenes capable of chiral recognition as a result of stereochemically dependent noncovalent interactions with the diffusing molecule. We found that the selectivity remains approximately the same for membranes modified with small molecules and with polymers. This suggests that enantiopermselectivity depends primarily on the strength of noncovalent interactions rather than the availability of recognition sites. Next, the transport of various generations of dendrimers through silica colloidal membranes was studied in a proof-of-concept experiment to demonstrate the size-selectivity of our materials. Smaller dendrimers were found to diffuse faster and selectivity is improved by using smaller nanopores. Finally, the transport of proteins through silica colloidal membranes was studied as a function of nanopore size

  14. Control over Silica Particle Growth and Particle–Biomolecule Interactions Facilitates Silica Encapsulation of Mammalian Cells with Thickness Control

    DOE PAGES

    Johnston, Robert K.; Harper, Jason C.; Tartis, Michaelann S.

    2017-07-13

    Over the past 20 years, many strategies utilizing sol–gel chemistry to integrate biological cells into silica-based materials have been reported. One such strategy, Sol-Generating Chemical Vapor into Liquid (SG-CViL) deposition, shows promise as an efficient encapsulation technique due to the ability to vary the silica encapsulation morphology obtained by this process through variation of SG-CViL reaction conditions. In this report, we develop SG-CViL as a tunable, multi-purpose silica encapsulation strategy by investigating the mechanisms governing both silica particle generation and subsequent interaction with phospholipid assemblies (liposomes and living cells). Using Dynamic Light Scattering (DLS) measurements, linear and exponential silica particlemore » growth dynamics were observed which were dependent on deposition buffer ion constituents and ion concentration. Silica particle growth followed a cluster–cluster growth mechanism at acidic pH, and a monomer-cluster growth mechanism at neutral to basic pH. Increasing silica sol aging temperature resulted in higher rates of particle growth and larger particles. DLS measurements employing PEG-coated liposomes and cationic liposomes, serving as model phospholipid assemblies, revealed that electrostatic interactions promote more stable liposome–silica interactions than hydrogen bonding and facilitate silica coating on suspension cells. However, continued silica reactivity leads to aggregation of silica-coated suspension cells, revealing the need for cell isolation to tune deposited silica thickness. As a result, utilizing these mechanistic study insights, silica was deposited onto adherent HeLa cells under biocompatible conditions with micrometer-scale control over silica thickness, minimal cell manipulation steps, and retained cell viability over several days.« less

  15. Production and Application of Olivine Nano-Silica in Concrete

    NASA Astrophysics Data System (ADS)

    Mardiana, Oesman; Haryadi

    2017-05-01

    The aim of this research was to produce nano silica by synthesis of nano silica through extraction and dissolution of ground olivine rock, and applied the nano silica in the design concrete mix. The producing process of amorphous silica used sulfuric acid as the dissolution reagent. The separation of ground olivine rock occurred when the rock was heated in a batch reactor containing sulfuric acid. The results showed that the optimum mole ratio of olivine- acid was 1: 8 wherein the weight ratio of the highest nano silica generated. The heating temperature and acid concentration influenced the mass of silica produced, that was at temperature of 90 °C and 3 M acid giving the highest yield of 44.90%. Characterization using Fourier Transform Infrared (FTIR ) concluded that amorphous silica at a wavenumber of 1089 cm-1 indicated the presence of siloxane, Si-O-Si, stretching bond. Characterization using Scanning Electron Microscope - Energy Dispersive Spectroscopy (SEM-EDS) showed the surface and the size of the silica particles. The average size of silica particles was between 1-10 μm due to the rapid aggregation of the growing particles of nano silica into microparticles, caused of the pH control was not fully achieved.

  16. Assembly of functional gold nanoparticle on silica microsphere.

    PubMed

    Wang, Hsuan-Lan; Lee, Fu-Cheng; Tang, Tse-Yu; Zhou, Chenguang; Tsai, De-Hao

    2016-05-01

    We demonstrate a controlled synthesis of silica microsphere with the surface-decorated functional gold nanoparticles. Surface of silica microsphere was modified by 3-aminopropypltriethoxysilane and 3-aminopropyldimethylethoxysilane to generate a positive electric field, by which the gold nanoparticles with the negative charges (unconjugated, thiolated polyethylene glycol functionalized with the traceable packing density and conformation) were able to be attracted to the silica microsphere. Results show that both the molecular conjugation on gold nanoparticle and the uniformity in the amino-silanization of silica microsphere influenced the loading and the homogeneity of gold nanoparticles on silica microsphere. The 3-aminopropyldimethylethoxysilane-functionalized silica microsphere provided an uniform field to attract gold nanoparticles. Increasing the ethanol content in aminosilane solution significantly improved the homogeneity and the loading of gold nanoparticles on the surface of silica microsphere. For the gold nanoparticle, increasing the molecular mass of polyethylene glycol yielded a greater homogeneity but a lower loading on silica microsphere. Bovine serum albumin induced the desorption of gold nanoparticles from silica microsphere, where the extent of desorption was suppressed by the presence of high-molecular mass polyethylene glycol on gold nanoparticles. This work provides the fundamental understanding for the synthesis of gold nanoparticle-silica microsphere constructs useful to the applications in chemo-radioactive therapeutics.

  17. Robust, ultrasmall organosilica nanoparticles without silica shells

    NASA Astrophysics Data System (ADS)

    Murray, Eoin; Born, Philip; Weber, Anika; Kraus, Tobias

    2014-07-01

    Traditionally, organosilica nanoparticles have been prepared inside micelles with an external silica shell for mechanical support. Here, we compare these hybrid core-shell particles with organosilica particles that are robust enough to be produced both inside micelles and alone in a sol-gel process. These particles form from octadecyltrimethoxy silane as silica source either in microemulsions, resulting in water-dispersible particles with a hydrophobic core, or precipitate from an aqueous mixture to form particles with both hydrophobic core and surface. We examine size and morphology of the particles by dynamic light scattering and transmission electron microscopy and show that the particles consist of Si-O-Si networks pervaded by alkyl chains using nuclear magnetic resonance, infrared spectroscopy, and thermogravimetric analysis.

  18. Targeted mesoporous silica nanocarriers in oncology.

    PubMed

    Baeza, Alejandro; Vallet-Regí, Maria

    2016-06-02

    Cancer is one of the major leading causes of death worldwide and its prevalence will be higher in the coming years due to the progressive aging of the population. The development of nanocarriers in oncology has provided a new hope in the fight against this terrible disease. Among the different types of nanoparticles which have been described, mesoporous silica nanoparticles (MSNs) constitute a very promising material due to their inherent properties as high loading capacity of many different drugs, excellent biocompatibility and easiness functionalization. This review presents the current state of the art related with the development of mesoporous silica nanocarriers for antitumoral therapy paying special attention on targeted MSN able to selectively destroy tumoral cells reducing the side damage in healthy ones, and the basic principles of targeting tumoral tissues and cells.

  19. 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.

  20. Phase diagram of silica from computer simulation

    NASA Astrophysics Data System (ADS)

    Saika-Voivod, Ivan; Sciortino, Francesco; Grande, Tor; Poole, Peter H.

    2004-12-01

    We evaluate the phase diagram of the “BKS” potential [van Beest, Kramer, and van Santen, Phys. Rev. Lett. 64, 1955 (1990)], a model of silica widely used in molecular dynamics (MD) simulations. We conduct MD simulations of the liquid, and three crystals ( β -quartz, coesite, and stishovite) over wide ranges of temperature and density, and evaluate the total Gibbs free energy of each phase. The phase boundaries are determined by the intersection of these free energy surfaces. Not unexpectedly for a classical pair potential, our results reveal quantitative discrepancies between the locations of the BKS and real silica phase boundaries. At the same time, we find that the topology of the real phase diagram is reproduced, confirming that the BKS model provides a satisfactory qualitative description of a silicalike material. We also compare the phase boundaries with the locations of liquid-state thermodynamic anomalies identified in previous studies of the BKS model.

  1. 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.

  2. Silica containing highly porous alumina ceramic

    NASA Astrophysics Data System (ADS)

    Svinka, R.; Svinka, V.; Zake, I.

    2011-04-01

    Porous alumina ceramic were produced by slip casting of aqueous alumina slurry with added small amount of metallic aluminium powder. Pores form in result of chemical reaction of aluminum with water by hydrogen gas evolution reaction and solidification of suspension. Porosity of such materials sintered at a temperature of 1600 - 1750°C varies from 60 to 90%. Pore size distribution and mechanical strength of these materials depend largely on the grain size of used raw materials. The major part of pores in the materials produced without additive of silica are larger than 10 ±m, but with 5 - 10 wt.% additive of silica in the raw mix pore size decreases considerably. The sintering shrinkage decreases to 2.5%. Coefficient of thermal expansion equally decreases from 8.9-10-6 K-1 to 7.1 10-6 K-1 and classification temperature increases to 1600°C, while deformation at high temperature decreases considerably.

  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.

  4. Optimization of silica silanization by 3-aminopropyltriethoxysilane.

    PubMed

    Howarter, John A; Youngblood, Jeffrey P

    2006-12-19

    Thin films of 3-aminopropyltriethoxysilane (APTES) are commonly used to promote adhesion between silica substrates and organic or metallic materials with applications ranging from advanced composites to biomolecular lab-on-a-chip. Unfortunately, there is confusion as to which reaction conditions will result in consistently aminated surfaces. A wide range of conflicting experimental methods are used with researchers often assuming the creation of smooth self-assembled monolayers. A range of film morphologies based on the film deposition conditions are presented here to establish an optimized method of APTES film formation. The effect of reaction temperature, solution concentration, and reaction time on the structure and morphology was studied for the system of APTES on silica. Three basic morphologies were observed: smooth thin film, smooth thick film, and roughened thick film.

  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. Interaction between water and defective silica surfaces

    SciTech Connect

    Chen Yunwen; Cheng Haiping

    2011-03-21

    We use the density functional theory method to study dry (1 x 1) {alpha}-quartz (0001) surfaces that have Frenkel-like defects such as oxygen vacancy and oxygen displacement. These defects have distinctively different effects on the water-silica interface depending on whether the adsorbent is a single water molecule, a cluster, or a thin film. The adsorption energies, bonding energies, and charge transfer or redistributions are analyzed, from which we find that the existence of a defect enhances the water molecule and cluster surface interaction by a large amount, but has little or even negative effect on water thin film-silica surface interaction. The origin of the weakening in film-surface systems is the collective hydrogen bonding that compromises the water-surface interaction in the process of optimizing the total energy. For clusters on surfaces, the lowest total energy states lower both the bonding energy and the adsorption energy.

  7. 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

  8. (129)Xe NMR of Mesoporous Silicas

    SciTech Connect

    Anderson, M.T.; Asink, R.A.; Kneller, J.M.; Pietrass, T.

    1999-04-23

    The porosities of three mesoporous silica materials were characterized with {sup 129}Xe NMR spectroscopy. The materials were synthesized by a sol-gel process with r = 0, 25, and 70% methanol by weight in an aqueous cetyltrimethylammonium bromide solution. Temperature dependent chemical shifts and spin lattice relaxation times reveal that xenon does not penetrate the pores of the largely disordered (r= 70%) silica. For both r = 0 and 25%, temperature dependent resonances corresponding to physisorbed xenon were observed. An additional resonance for the r = 25% sample was attributed to xenon between the disordered cylindrical pores. 2D NMR exchange experiments corroborate the spin lattice relaxation data which show that xenon is in rapid exchange between the adsorbed and the gas phase.

  9. Stress relaxation of vitreous silica on irradiation

    NASA Astrophysics Data System (ADS)

    Primak, William

    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 ˜1014 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 ˜1019 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.

  10. Mortality in the UK industrial silica sand industry: 1. Assessment of exposure to respirable crystalline silica

    PubMed Central

    Brown, T; Rushton, L

    2005-01-01

    Aims: To develop a job-exposure matrix (JEM) from personal and static respirable crystalline silica (RCS) measurements in UK industrial silica sand workers. Methods: A total of 2429 personal and 583 static RCS dust samples were collected using cyclone samplers at seven UK quarries between 1978 and 2000. These data were combined, and analysis of variance using general linear models was used to evaluate the effect of quarry, job, and year on RCS concentrations, and facilitate the creation of five quarry and three time categories with similar exposure levels by comparing the least-square GM RCS concentrations. Results: The overall geometric mean (GM) RCS concentration was 0.09 mg/m3 (geometric standard deviation 3.9). Silica flour and dry job categories tended to have the highest RCS exposure and 13.3% of all samples exceeded the UK maximum exposure level of 0.3 mg/m3. RCS levels generally decreased over time. Conclusions: Data have been collected and used to develop a JEM for UK industrial silica sand workers between 1978 and 2000. Although there were some limitations in the data and certain assumptions were made, the use of available data to estimate exposure quantitatively is an improvement over the use of qualitative and surrogate measures of exposure. The continual collection of dust measurements in the industry is essential to facilitate the exploration of exposure-response relations that may exist between silica and silicosis, lung cancer, and other diseases. PMID:15961619

  11. Interaction of silica nano-particles with a flat silica surface through neutron reflectometry

    SciTech Connect

    Chung, Eunhyea; Yiacoumi, Sotira; Halbert, Candice E; Ankner, John Francis; Wang, Wei; Tsouris, Costas

    2012-01-01

    Neutron reflectometry (NR) was employed to study the interaction of nanosized silica particles with a flat silica surface in aqueous solutions. Unlike other experimental tools that are used to study surface interactions, NR can provide information on the particle density profile in the solution near the interface. Two types of silica particles (25 and 100 nm) were suspended in aqueous solutions of varying ionic strength. Theoretical calculations of the surface interaction potential between a particle and a flat silica surface using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were compared to the experimental data. The theory predicts that the potential energy is highly dependent on the ionic strength. In high ionic strength solutions, NR reveals a high concentration of particles near the flat silica surface. Under the same conditions, theoretical calculations show an attractive force between a particle and a flat surface. For low ionic strength solutions, the particle concentration near the surface obtained from NR is the same as the bulk concentration, while depletion of particles near the surface is expected because of the repulsion predicted by the DLVO theory.

  12. 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%.

  13. Mortality in the UK industrial silica sand industry: 1. Assessment of exposure to respirable crystalline silica.

    PubMed

    Brown, T P; Rushton, L

    2005-07-01

    To develop a job-exposure matrix (JEM) from personal and static respirable crystalline silica (RCS) measurements in UK industrial silica sand workers. A total of 2429 personal and 583 static RCS dust samples were collected using cyclone samplers at seven UK quarries between 1978 and 2000. These data were combined, and analysis of variance using general linear models was used to evaluate the effect of quarry, job, and year on RCS concentrations, and facilitate the creation of five quarry and three time categories with similar exposure levels by comparing the least-square GM RCS concentrations. The overall geometric mean (GM) RCS concentration was 0.09 mg/m3 (geometric standard deviation 3.9). Silica flour and dry job categories tended to have the highest RCS exposure and 13.3% of all samples exceeded the UK maximum exposure level of 0.3 mg/m3. RCS levels generally decreased over time. Data have been collected and used to develop a JEM for UK industrial silica sand workers between 1978 and 2000. Although there were some limitations in the data and certain assumptions were made, the use of available data to estimate exposure quantitatively is an improvement over the use of qualitative and surrogate measures of exposure. The continual collection of dust measurements in the industry is essential to facilitate the exploration of exposure-response relations that may exist between silica and silicosis, lung cancer, and other diseases.

  14. Adsorption of silica colloids onto like-charged silica surfaces of different roughness

    DOE PAGES

    Dylla-Spears, R.; Wong, L.; Shen, N.; ...

    2017-01-17

    Particle adsorption was explored in a model optical polishing system, consisting of silica colloids and like-charged silica surfaces. The adsorption was monitored in situ under various suspension conditions, in the absence of surfactants or organic modifiers, using a quartz crystal microbalance with dissipation monitoring (QCM-D). Changes in surface coverage with particle concentration, particle size, pH, ionic strength and ionic composition were quantified by QCM-D and further characterized ex situ by atomic force microscopy (AFM). A Monte Carlo model was used to describe the kinetics of particle deposition and provide insights on scaling with particle concentration. Transitions from near-zero adsorption tomore » measurable adsorption were compared with equilibrium predictions made using the Deraguin-Verwey-Landau-Overbeek (DLVO) theory. In addition, the impact of silica surface roughness on the propensity for particle adsorption was studied on various spatial scale lengths by intentionally roughening the QCM sensor surface using polishing methods. It was found that a change in silica surface roughness at the AFM scale from 1.3 nm root-mean-square (rms) to 2.7 nm rms resulted in an increase in silica particle adsorption of 3-fold for 50-nm diameter particles and 1.3-fold for 100-nm diameter particles—far exceeding adsorption observed by altering suspension conditions alone, potentially because roughness at the proper scale reduces the total separation distance between particle and surface.« less

  15. Microelectrophoresis of Silica Rods Using Confocal Microscopy

    PubMed Central

    2017-01-01

    The electrophoretic mobility and the zeta potential (ζ) of fluorescently labeled colloidal silica rods, with an aspect ratio of 3.8 and 6.1, were determined with microelectrophoresis measurements using confocal microscopy. In the case where the colloidal particles all move at the same speed parallel to the direction of the electric field, we record a xyz-stack over the whole depth of the capillary. This method is faster and more robust compared to taking xyt-series at different depths inside the capillary to obtain the parabolic flow profile, as was done in previous work from our group. In some cases, rodlike particles do not move all at the same speed in the electric field, but exhibit a velocity that depends on the angle between the long axis of the rod and the electric field. We measured the orientation-dependent velocity of individual silica rods during electrophoresis as a function of κa, where κ–1 is the double layer thickness and a is the radius of the rod associated with the diameter. Thus, we determined the anisotropic electrophoretic mobility of the silica rods with different sized double layers. The size of the double layer was tuned by suspending silica rods in different solvents at different electrolyte concentrations. We compared these results with theoretical predictions. We show that even at already relatively high κa when the Smoluchowski limiting law is assumed to be valid (κa > 10), an orientation dependent velocity was measured. Furthermore, we observed that at decreasing values of κa the anisotropy in the electrophoretic mobility of the rods increases. However, in low polar solvents with κa < 1, this trend was reversed: the anisotropy in the electrophoretic mobility of the rods decreased. We argue that this decrease is due to end effects, which was already predicted theoretically. When end effects are not taken into account, this will lead to strong underestimation of the experimentally determined zeta potential. PMID:28045541

  16. 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.

  17. 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.

  18. 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.

  19. Formation of silica nanoparticles in microemulsions.

    PubMed

    Finnie, Kim S; Bartlett, John R; Barbé, Christophe J A; Kong, Linggen

    2007-03-13

    Silica nanoparticles for controlled release applications have been produced by the reaction of tetramethylorthosilicate (TMOS) inside the water droplets of a water-in-oil microemulsion, under both acidic (pH 1.05) and basic (pH 10.85) conditions. In-situ FTIR measurements show that the addition of TMOS to the microemulsion results in the formation of silica as TMOS, preferentially located in the oil phase, diffuses into the water droplets. Once in the hydrophilic domain, hydrolysis occurs rapidly as a result of the high local concentration of water. Varying the pH of the water droplets from 1.05 to 10.85, however, considerably slows the hydrolysis reaction of TMOS. The formation of a dense silica network occurs rapidly under basic conditions, with IR indicating the slower formation of more disordered silica in acid. SAXS analysis of the evolving particles shows that approximately 11 nm spheres are formed under basic conditions; these are stabilized by a water/surfactant layer on the particle surface during formation. Under acidic conditions, highly uniform approximately 5 nm spheres are formed, which appear to be retained within the water droplets (approximately 6 nm diameter) and form an ordered micelle nanoparticle structure that exhibits sufficient longer-range order to generate a peak in the scattering at q approximately equal to 0.05 A-1. Nitrogen adsorption analysis reveals that high surface area (510 m2/g) particles with an average pore size of 1 nm are formed at pH 1.05. In contrast, base synthesis results in low surface area particles with negligible internal porosity.

  20. 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.

  1. Silica exposure in hand grinding steel castings.

    PubMed

    O'Brien, D; Froehlich, P A; Gressel, M G; Hall, R M; Clark, N J; Bost, P; Fischbach, T

    1992-01-01

    Exposure to silica dust was studied in the grinding of castings in a steel foundry that used conventional personal sampling methods and new real-time sampling techniques developed for the identification of high-exposure tasks and tools. Approximately one-third of the personal samples exceeded the National Institute for Occupational Safety and Health recommended exposure limit for crystalline silica, a fraction similar to that identified in other studies of casting cleaning. Of five tools used to clean the castings, the tools with the largest wheels, a 6-in. grinder and a 4-in. cutoff wheel, were shown to be the major sources of dust exposure. Existing dust control consisted of the use of downdraft grinding benches. The size of the casting precluded working at a distance close enough to the grates of the downdraft benches for efficient capture of the grinding dust. In addition, measurements of air recirculated from the downdraft benches indicated that less than one-half of the respirable particles were removed from the contaminated airstream. Previous studies have shown that silica exposures in the cleaning of castings can be reduced or eliminated through the use of mold coatings, which minimize sand burn-in on the casting surface; by application of high-velocity, low-volume exhaust hoods; and by the use of a nonsilica molding aggregate such as olivine. This study concluded that all these methods would be appropriate control options.

  2. Ammonia hardening of porous silica antireflective coatings

    NASA Astrophysics Data System (ADS)

    Belleville, Philippe F.; Floch, Herve G.

    1994-10-01

    The adhesion of sol-gel antireflective porous silica coatings on vitreous optical substrates has been dramatically improved by exposure to ammonia vapors or a dip in basic solutions. The approximately 70 to 270-nm thick coatings consisted of monolayers of spherical, 20-nm diameter amorphous silica particles deposited from ethanolic colloidal suspensions by conventional liquid coating techniques. Although, the as-deposited coatings had only low adhesion and were easily damaged when cleaned by standard drag-wiping procedures, coatings exposed over 5 hours to ammonia vapors passed both adhesive-tape and moderate abrasive- resistance tests. The increase in strength was accompanied by a roughly 20% shrinkage of the original coating thickness but the antireflective properties were retained. Our explanation of this chemical effect is a base-catalyzed phenomenon leading to surface silanol condensation and hydrogen-bonding of neighbor silica particles. In addition, since this basic treatment enhanced the laser damage resistance, such strengthened antireflective coatings have been successfully evaluated on flashlamps used on Phebus, Europe's most powerful laser. This allows an increase of the laser-disk pumping efficiency.

  3. The Optical Properties of Ion Implanted Silica

    NASA Technical Reports Server (NTRS)

    Smith, Cydale C.; Ila, D.; Sarkisov, S.; Williams, E. K.; Poker, D. B.; Hensley, D. K.

    1997-01-01

    We will present our investigation on the change in the optical properties of silica, 'suprasil', after keV through MeV implantation of copper, tin, silver and gold and after annealing. Suprasil-1, name brand of silica glass produced by Hereaus Amerisil, which is chemically pure with well known optical properties. Both linear nonlinear optical properties of the implanted silica were investigated before and after thermal annealing. All implants, except for Sn, showed strong optical absorption bands in agreement with Mie's theory. We have also used Z-scan to measure the strength of the third order nonlinear optical properties of the produced thin films, which is composed of the host material and the metallic nanoclusters. For implants with a measurable optical absorption band we used Doyle's theory and the full width half maximum of the absorption band to calculate the predicted size of the formed nanoclusters at various heat treatment temperatures. These results are compared with those obtained from direct observation using transmission electron microscopic techniques.

  4. Precipitation and Crystallization Kinetics in Silica Gardens.

    PubMed

    Glaab, Fabian; Rieder, Julian; Klein, Regina; Choquesillo-Lazarte, Duane; Melero-Garcia, Emilio; García-Ruiz, Juan-Manuel; Kunz, Werner; Kellermeier, Matthias

    2017-02-17

    Silica gardens are extraordinary plant-like structures resulting from the complex interplay of relatively simple inorganic components. Recent work has highlighted that macroscopic self-assembly is accompanied by the spontaneous formation of considerable chemical gradients, which induce a cascade of coupled dissolution, diffusion, and precipitation processes occurring over timescales as long as several days. In the present study, this dynamic behavior was investigated for silica gardens based on iron and cobalt chloride by means of two synchrotron-based techniques, which allow the determination of concentration profiles and time-resolved monitoring of diffraction patterns, thus giving direct insight into the progress of dissolution and crystallization phenomena in the system. On the basis of the collected data, a kinetic model is proposed to describe the relevant reactions on a fundamental physicochemical level. The results show that the choice of the metal cations (as well as their counterions) is crucial for the development of silica gardens in both the short and long term (i.e. during tube formation and upon subsequent slow equilibration), and provide important clues for understanding the properties of related structures in geochemical and industrial environments.

  5. Seeded Growth of Colloidal Silica Particles

    NASA Technical Reports Server (NTRS)

    Wurm, David B.

    1999-01-01

    The method of seeded growth was studied for producing mondisperse colloidal silica particles. It was shown that particle size as well as weight percent solids could be controlled by using this method. The particles were characterized by transmission electron microscopy (TEM) and quasielastic light scattering (QELS). The particles were found to have a bimodal size distribution when examined by TEM. The particle size as determined by QELS was found to be roughly 10-20% larger than the particle size as determined by TEM. Furthermore, the polydispersity (standard deviation/mean particle size) as determined by QELS was found to be significantly lower than the polydispersity as determined by TEM. This underscores the importance of using TEM as a characterization technique for determining particle monodispersity. It was also noted that there was an increase in particle roughness as the weight percent of the silica particles increased and a new nucleation of particles was observed as the weight percent approached 13%. A recipe for producing monodisperse silica particles in the 150 nm size range is presented.

  6. The Optical Properties of Ion Implanted Silica

    NASA Technical Reports Server (NTRS)

    Smith, Cydale C.; Ila, D.; Sarkisov, S.; Williams, E. K.; Poker, D. B.; Hensley, D. K.

    1997-01-01

    We will present our investigation on the change in the optical properties of silica, 'suprasil', after keV through MeV implantation of copper, tin, silver and gold and after annealing. Suprasil-1, name brand of silica glass produced by Hereaus Amerisil, which is chemically pure with well known optical properties. Both linear nonlinear optical properties of the implanted silica were investigated before and after thermal annealing. All implants, except for Sn, showed strong optical absorption bands in agreement with Mie's theory. We have also used Z-scan to measure the strength of the third order nonlinear optical properties of the produced thin films, which is composed of the host material and the metallic nanoclusters. For implants with a measurable optical absorption band we used Doyle's theory and the full width half maximum of the absorption band to calculate the predicted size of the formed nanoclusters at various heat treatment temperatures. These results are compared with those obtained from direct observation using transmission electron microscopic techniques.

  7. Silica Nanoconstruct Cellular Toleration Threshold In Vitro

    PubMed Central

    Herd, Heather L.; Malugin, Alexander; Ghandehari, Hamidreza

    2011-01-01

    The influence of geometry of silica nanomaterials on cellular uptake and toxicity on epithelial and phagocytic cells was studied. Three types of amine-terminated silica nanomaterials were prepared and characterized via the modified Stober method, namely spheres (178±27 nm), worms (232±22 nm × 1348±314 nm) and cylinders (214±29 nm × 428±66 nm). The findings of the study suggest that in this size range and for the cell types studied, geometry does not play a dominant role in the modes of toxicity and uptake of these particles. Rather, a concentration threshold and cell type dependent toxicity of all particle types was observed. This correlated with confocal microscopy observations, as all nanomaterials were observed to be taken up in both cell types, with a greater extent in phagocytic cells. It must be noted that there appears to be a concentration threshold at ~100 µg/mL, below which there is limited to no impact of the nanoparticles on membrane integrity, mitochondrial function, phagocytosis or cell death. Analysis of cell morphology by transmission electron microscopy, colocalization experiments with intracellular markers and Western Blot results provide evidence of potential involvement of lysosomal escape, autophagic like activity, compartmental fusion and recycling in response to intracellular nanoparticle accumulation. These processes could be involved in cellular coping or defense mechanisms. The manipulation of physicochemical properties to enhance or reduce toxicity paves the way for the safe design of silica-based nanoparticles for use in nanomedicine. PMID:21342660

  8. Nanostructured mesoporous silica matrices in nanomedicine.

    PubMed

    Vallet-Regí, M

    2010-01-01

    In the last few years the biomedical research field has shown a growing interest towards nanostructured mesoporous silica materials, whose chemical composition is silica and present nanometric pores. These bioceramics exhibit two important features: they can regenerate osseous tissues--the bond bioactivity of these materials has been confirmed by the formation of biological-like nanoapatites on their surface when in contact with physiological fluids--and they are able to act as controlled release systems. Drugs in the nanometre scale can be loaded on those matrices and then locally released in a controlled fashion. It is possible to chemically modify the silica walls to favour the adsorption of certain biomolecules such as peptides, proteins or growth factors. It is even possible to design smart biomaterials where the drug is released under an external stimulus. Thus, looking at all those properties, a question arises: Have these bioceramics good expectations to be used in clinical medical practice? Their biocompatibility, bioactivity, capacity to regenerate bone and ability to act as controlled release systems of biologically active species have been confirmed. In fact, their preliminary in vitro and in vivo essays have been positive. Now it is the time to adequate all these properties to the actual clinical problems, and to evaluate their efficiency in comparison with materials already known and currently employed such as bioglasses.

  9. Precipitation and Crystallization Kinetics in Silica Gardens

    PubMed Central

    Glaab, Fabian; Rieder, Julian; Klein, Regina; Choquesillo‐Lazarte, Duane; Melero‐Garcia, Emilio; García‐Ruiz, Juan‐Manuel

    2017-01-01

    Abstract Silica gardens are extraordinary plant‐like structures resulting from the complex interplay of relatively simple inorganic components. Recent work has highlighted that macroscopic self‐assembly is accompanied by the spontaneous formation of considerable chemical gradients, which induce a cascade of coupled dissolution, diffusion, and precipitation processes occurring over timescales as long as several days. In the present study, this dynamic behavior was investigated for silica gardens based on iron and cobalt chloride by means of two synchrotron‐based techniques, which allow the determination of concentration profiles and time‐resolved monitoring of diffraction patterns, thus giving direct insight into the progress of dissolution and crystallization phenomena in the system. On the basis of the collected data, a kinetic model is proposed to describe the relevant reactions on a fundamental physicochemical level. The results show that the choice of the metal cations (as well as their counterions) is crucial for the development of silica gardens in both the short and long term (i.e. during tube formation and upon subsequent slow equilibration), and provide important clues for understanding the properties of related structures in geochemical and industrial environments. PMID:28001337

  10. 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.

  11. 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

  12. Reevaluation of tephra volumes for the 1982 eruption of El Chichón volcano, Mexico

    NASA Astrophysics Data System (ADS)

    Nathenson, M.; Fierstein, J.

    2012-12-01

    Reevaluation of tephra volumes for the 1982 eruption of El Chichón volcano, Mexico Manuel Nathenson and Judy Fierstein U.S. Geological Survey, 345 Middlefield Road MS-910, Menlo Park, CA 94025 In a recent numerical simulation of tephra transport and deposition for the 1982 eruption, Bonasia et al. (2012) used masses for the tephra layers (A-1, B, and C) based on the volume data of Carey and Sigurdsson (1986) calculated by the methodology of Rose et al. (1973). For reasons not clear, using the same methodology we obtained volumes for layers A-1 and B much less than those previously reported. For example, for layer A-1, Carey and Sigurdsson (1986) reported a volume of 0.60 km3, whereas we obtain a volume of 0.23 km3. Moreover, applying the more recent methodology of tephra-volume calculation (Pyle, 1989; Fierstein and Nathenson, 1992) and using the isopachs maps in Carey and Sigurdsson (1986), we calculate a total tephra volume of 0.52 km3 (A-1, 0.135; B, 0.125; and C, 0.26 km3). In contrast, Carey and Sigurdsson (1986) report a much larger total volume of 2.19 km3. Such disagreement not only reflects the differing methodologies, but we propose that the volumes calculated with the methodology of Pyle and of Fierstein and Nathenson—involving the use of straight lines on a log thickness versus square root of area plot—better represent the actual fall deposits. After measuring the areas for the isomass contours for the HAZMAPP and FALL3D simulations in Bonasia et al. (2012), we applied the Pyle-Fierstein and Nathenson methodology to calculate the tephra masses deposited on the ground. These masses from five of the simulations range from 70% to 110% of those reported by Carey and Sigurdsson (1986), whereas that for layer B in the HAZMAP calculation is 160%. In the Bonasia et al. (2012) study, the mass erupted by the volcano is a critical input used in the simulation to produce an ash cloud that deposits tephra on the ground. Masses on the ground (as calculated by us

  13. 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.

  14. 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.

  15. 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

  16. Reevaluation of Neptunium-Nitric Acid Radiation Chemistry by Multiscale Modeling.

    PubMed

    Horne, G P; Grimes, T S; Mincher, B J; Mezyk, S P

    2016-12-15

    Multiscale modeling has been used to quantitatively reevaluate the radiation chemistry of neptunium in a range of aerated nitric acid solutions (0.1-6.0 mol dm(-3)). Exact calculation of initial radiolytic yields accounting for changes in radiation track chemistry was found to be crucial for reproducing experimental data. The γ irradiation induces changes in the Np(VI)/Np(V) oxidation-state distribution, predominantly driven by reactions involving HNO2, H2O2, NO2(•), and NO3(•) from the radiolysis of aqueous nitric acid. Oxidation of Np(V) by NO3(•) (k = 8.1 × 10(8) dm(3) mol(-1) s(-1)) provides the initial increase in Np(VI) concentration, while also delaying net reduction of Np(VI) by consuming HNO2. Reduction of Np(VI) is dominated by thermal reactions with HNO2 (k = 0.7-73 dm(3) mol(-1) s(-1)) and H2O2 (k = 1.9 dm(3) mol(-1) s(-1)). A steady state is eventually established once the concentration of Np(V) is sufficiently high to be oxidized by NO2(•) (k = 2.4 × 10(2)-3.1 × 10(4) dm(3) mol(-1) s(-1)). An additional thermal oxidation reaction between Np(V) and HNO3 (k = 2.0 × 10(3) dm(3) mol(-1) s(-1)) is required for nitric acid concentrations >4.0 mol dm(-3). For 0.1 mol dm(-3) HNO3, the rate of Np(VI) reduction is in excess of that which can be accounted for by radiolytic product mass balance, suggesting the existence of a catalytic-acid-dependent reduction process.

  17. A reevaluation of the morphology, paleoecology, and phylogenetic relationships of the enigmatic walrus Pelagiarctos.

    PubMed

    Boessenecker, Robert W; Churchill, Morgan

    2013-01-01

    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). 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. 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 generalist predator, feeding on fish, invertebrates, and the occasional

  18. Re-evaluating the 1257 AD eruption using annually-resolved ice core chemical analyses

    NASA Astrophysics Data System (ADS)

    Simonsen, M. F.; Kjær, H. A.; Vallelonga, P. T.; Neff, P. D.; Bertler, N. A. N.; Svensson, A.; Seierstad, I.; Albert, P. G.; Bourne, A. J.; Kurbatov, A.

    2014-12-01

    The source of the 1257 AD volcanic eruption has recently been proposed to be Samalas in Indonesia. The eruption was one of the largest of the Holocene and has been recorded in ice cores in both hemispheres from sulfate and acidity measurements. The estimate of its sulfate load varies from 2 to 8 times that of Tambora. This is also the only volcano for which tephras have been assigned in ice cores from both Antarctica and Greenland (GISP2). Due to this unique assignment of a bipolar tephra layer in ice cores, the origins of the sulfate and tephras have been disputed and it has been proposed that at least one of the tephras was due to an additional volcanic eruption local to either Greenland or Antarctica. We have re-evaluated the acid and tephra deposition from the 1257 AD volcano in two ice cores, one from Greenland (NGRIP. 75.1° N, 42.3° W) and one from Antarctica (RICE, Roosevelt Island. 79.36° S, -161.71° W). Annually-resolved continuous flow analysis (CFA) measurements determined relevant parameters such as melt water conductivity, sulphate and acidity. The acidity peak at RICE (~20 uM H+) is approximately double that found at NGRIP (10 uM H+). The only visible tephra layer found in the corresponding depth range was deposited at 1250 AD, 9 years before the acidity peak. The high resolution of the data offers a precise evaluation of the delay between the deposition of tephra and acid (sulfate) in each hemisphere. The comparison between poles allows some evaluation of the spread of deposition from the volcanic eruption.

  19. A Re-Evaluation of the Relativistic Redshift on Frequency Standards at NIST, Boulder, Colorado, USA

    NASA Astrophysics Data System (ADS)

    Pavlis, N. K.; Weiss, M. A.

    2014-12-01

    Primary frequency standards that realize the definition of the second based on the Caesium (Cs) atom are used to steer International Atomic Time. According to the theory of relativity, their frequency should be adjusted to that at which these would operate, if located on the geoid. Current best standards for the current definition of the second are approaching uncertainties of one part in 1016. Optical frequency standards however are now reaching uncertainties of few parts in 1018 and are expected to lead to a new definition of the second. Their performance requires centimetre-level geoid accuracy, in order to calculate accurately the redshift frequency offset necessary for their inter-comparison. We re-evaluated the relativistic redshift of the frequency standards at NIST in Boulder, Colorado, USA, based on a recent precise GPS survey of several benchmarks on the roof of the building where these are housed, and on global and local geoid models supported by data from the GRACE and GOCE missions, including EGM2008, USGG2009, and USGG2012. We also evaluated the redshift offset based on the published NAVD88 geopotential number of the levelling benchmark Q407, after estimating the bias of the NAVD88 datum at our specific location. We present and discuss the results that we obtained using different methods, and provide our current estimate of the redshift offset and of its accuracy, considering the main error sources contributing to the total error budget. We compare our current estimates to those published by Pavlis and Weiss in 2003, using the data and models that were available at that time. We also discuss the prospects of using inter-connected ultra-precise frequency standards for the direct determination of geoid height differences, which may provide in the not-too-distant future an alternative approach for the establishment of vertical datums and the independent verification of the accuracy of global and local geoid models.

  20. 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.

  1. 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.

  2. 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.

  3. Re-evaluation of in vitro activity of primycin against prevalent multiresistant bacteria.

    PubMed

    Feiszt, Péter; Mestyán, Gyula; Kerényi, Monika; Dobay, Orsolya; Szabó, Judit; Dombrádi, Zsuzsanna; Urbán, Edit; Emődy, Levente

    2014-11-01

    With the increasing emergence of antibiotic resistances old antibiotics became a valuable source to find agents suitable to address this problem. More than 20 years after the last report, our purpose was to re-evaluate the in vitro antibacterial activity of the topical agent primycin against current important bacterial pathogens. Minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) of primycin were tested in comparison with agents widely applied topically, and with those of mupirocin and vancomycin, the topical and the non-topical gold-standard anti-MRSA agents. Primycin was ineffective (MIC>64 μg/ml) against all the Gram-negative isolates tested. On the other hand, all the tested Gram-positive isolates were susceptible with MIC90 values of 0.06 μg/ml for staphylococci and 0.5-1 μg/ml for enterococci, streptococci, and P. acnes isolates, including all the multiresistant strains. Against MRSA isolates primycin showed slightly higher activity than mupirocin, and inhibited the mupirocin-resistant strains also. MBC90 values ranged from 0.25 to 2 μg/ml for the investigated Gram-positive species. The bactericidal effect proved to be concentration-dependent in time-kill experiments. Spontaneous resistant mutants did not emerge in single-step mutation experiments and the resistance development was very slow by serial passaging. Passaged S. aureus strains showing increased primycin MIC values exhibited elevated vancomycin and daptomycin MIC values also. Though elucidation of the mechanisms behind warrants further investigations, these correlations can be related to development of vancomycin-intermediate phenotype. From the point of view of medical practice it is noteworthy that the increased primycin MIC values remained far below the concentration accessible by local application of the agent. These data make primycin a remarkable object of further investigations as well as a promising candidate for topical application against

  4. A need for reevaluation of sports participation recommendations for children with a solitary kidney.

    PubMed

    Johnson, Blake; Christensen, Clinton; Dirusso, Stephen; Choudhury, Muhammad; Franco, Israel

    2005-08-01

    We sought to evaluate the incidence and outcome of blunt renal injury in children by mechanism of injury. These data could then be used to provide the basis for more rational recommendations to parents and physicians regarding participation in sporting activities. We analyzed data on 49,651 pediatric trauma cases collected by 92 trauma centers as part of the National Pediatric Trauma Registry from 1995 to 2001. Cases involving renal injury were isolated and the data were stratified according to age, sex and injury, as well as procedures required for treatment and outcomes. Of 49,651 pediatric trauma patients 813 incurred renal injury. There were 516 males and 291 females, and sex was not documented in 6 children. Average age was 10.6 years. There were no reports of a solitary kidney. In the sports group there were 4 nephrectomies, which were associated with sledding (2), skiing (1) and rollerblading (1), and 2 deaths related to skiing (1) and jet skiing (1). All 3 nephrectomies in the nonsports/other group were associated with equestrian activities, and 1 death occurred in this population. The nonsports/other group includes minor sports that are outlined by the American Academy of Pediatrics Committee on Sports Medicine and Fitness. The majority of renal injuries in children associated with kidney loss (21 of 28) occurred as a result of motor vehicle accidents, pedestrians being struck by a vehicle or other object, and falls. There were no kidneys lost in any contact sport. Sledding, skiing and rollerblading resulted in kidney loss. Current recommendations of the American Academy of Pediatrics Committee on Sports Medicine and Fitness prohibiting children with a solitary kidney from participating in contact sports appear to be overly protective and need to be reevaluated. In some instances activities listed as limited contact sports resulted in renal loss, showing that the risk associated with these activities has been underestimated.

  5. 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

  6. A case study of the seismic source function: Salmon and sterling reevaluated

    NASA Astrophysics Data System (ADS)

    Denny, Marvin D.; Goodman, Dennis M.

    1990-11-01

    As part of a larger joint effort by the Defense Advanced Research Project Agency and the Department of Energy to study the seismic source problem, a comprehensive reevaluation of the 1964 Salmon and 1966 Sterling nuclear explosions in dome salt was carried out. The Sterling source function originally estimated by Springer et al. (1968) conveys the impression that the cavity was badly overdriven; on reexamination this does not appear to be the case. The work of Glenn et al. (1987) on the Sterling free-field data is expanded upon, confirming that the cavity response was close to the theoretical expectation. Sterling's source function is estimated and is found to be comparable to Patterson's (1966) slightly weakened salt model. A source model for Salmon is derived from the Sterling source model and the five seismic stations that recorded both events. The new source model has a reduced displacement potential ψ∝ of about half that previously estimated. A temporary nonlinear two-wave system developed during the Salmon explosion as the compressional wave evolved from a shock wave; the separation of these two waves resulted in a high-frequency roll-off of the reduced velocity potential of ω-3. In addition, it is shown that the comer frequency is much higher and is created much closer to the cavity than the eigenfrequency. For both Salmon and Sterling the radial stresses are approximately a low-passed damped sinusoid superimposed on a small step function. The decoupling value of 72 obtained by Springer et al. (1968) is confirmed. A revision of Patterson's (1966) partial decoupling curve shows that the value for full decoupling in a shot-generated cavity would be only slightly higher. Contrary to previous studies, decoupling as a function of frequency for the surface waves is found to be the same as for the P waves. A new definition of decoupling appropriate to threshold test-ban treaty monitoring is also proposed.

  7. 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. Copyright 2010 Elsevier Inc. All rights reserved.

  8. Reevaluation of Commercial Reagents for Detection of Histoplasma capsulatum Antigen in Urine

    PubMed Central

    Harring, Julie A.; Dababneh, Ala S.; Rollins, Leonard O.; Bestrom, Jeannie E.; Jespersen, Deborah J.

    2015-01-01

    Detection of the Histoplasma capsulatum urinary antigen (UAg) is among the most sensitive and rapid means to diagnose histoplasmosis. Previously, we evaluated analyte-specific reagents (ASR) manufactured by IMMY (Norman, OK) for detection of Histoplasma galactomannan (GM) in urine using an enzyme immunoassay (EIA), and we showed low positive agreement (64.5%) with the MiraVista (MVista) Histoplasma antigen (Ag) quantitative EIA (MiraVista Diagnostics, Indianapolis, IN). Here we reevaluated the IMMY GM ASR following modification of our original assay protocol and introduction of an indeterminate range. A total of 150 prospectively collected urine samples were tested with both the IMMY and MVista EIAs, and clinical histories were recorded for all study subjects. The IMMY GM ASR showed positive and negative agreements of 82.3% (14/17 samples) and 100% (121/121 samples), respectively (with exclusion of 12 indeterminate results), and overall agreement of 90% (135/150 samples) with respect to the MVista EIA. Of the three patients with negative IMMY GM ASR results and positive MVista EIA results, testing was performed for initial diagnostic purposes for one patient (<0.4 ng/ml by the MVista EIA) and UAg levels were being monitored for the remaining two patients (both <0.7 ng/ml by the MVista EIA). The MVista EIA results were positive for 6/12 samples that tested indeterminate by the IMMY GM ASR. We also show that the IMMY GM ASR can be used to serially monitor Histoplasma UAg levels. In conclusion, we demonstrate that, with modification, the IMMY GM ASR is a reliable rapid assay for detection of Histoplasma UAg. PMID:25631806

  9. Re-evaluation of sarcolemma injury and muscle swelling in human skeletal muscles after eccentric exercise.

    PubMed

    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.

  10. 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. © 2014 Wiley Periodicals, Inc.

  11. The diagnostic criteria for iron deficiency in infants should be reevaluated.

    PubMed

    Domellöf, Magnus; Dewey, Kathryn G; Lönnerdal, Bo; Cohen, Roberta J; Hernell, Olle

    2002-12-01

    Diagnostic criteria for iron deficiency (ID) and iron deficiency anemia (IDA) in infants are poorly defined. Our aim was to establish appropriate cut-off values for hemoglobin (Hb), plasma ferritin, erythrocyte mean cell volume (MCV), zinc protoporphyrin (ZPP) and soluble transferrin receptors (TfR) in infancy. Exclusively breast-fed infants (n = 263) in Honduras and Sweden were randomly assigned to receive iron supplementation or placebo, and blood samples were obtained at 4, 6 and 9 mo of age. Reference ranges were determined using three different approaches for defining iron-replete infants. The usefulness of several variables for predicting the Hb response to iron was evaluated. We found the following 2 SD cut-off values in iron-replete infants: Hb <105 g/L at 4-6 mo and <100 g/L at 9 mo; ZPP >75 micro mol/mol heme at 4-6 mo and >90 micro mol/mol heme at 9 mo; ferritin <20 micro g/L at 4 mo, <9 micro g/L at 6 mo and <5 micro g/L at 9 mo; and TfR >11 mg/L at 4-9 mo. The Hb response to iron was not a useful definition of IDA at 4 mo of age. Hb, MCV and ZPP at 6 mo as well as growth variables predicted the Hb response at 6-9 mo, but ferritin and TfR at 6 mo did not. We conclude that there is need for a reevaluation of the definitions of ID and IDA in infants.

  12. Silica encapsulation by miniemulsion polymerization: distribution and localization of the silica particles in droplets and latex particles.

    PubMed

    Bourgeat-Lami, E; Farzi, G A; David, L; Putaux, J-L; McKenna, T F L

    2012-04-10

    The impact of including hydrophobically modified silica on the morphology of miniemulsified monomer mixtures and that of the resulting polymer particles was investigated, with emphasis placed on the distribution and localization of the inorganic phase. Silica nanoparticles with diameters of 20 and 78 nm were first modified with γ-methacryloxypropyl trimethoxysilane (γ-MPS) to favor their dispersion in methyl methacrylate (MMA)/n-butyl acrylate (BuA) and mixtures of varying MMA to BuA weight ratios. The monomer-silica dispersions were then emulsified by ultrasonication, and the resulting silica-loaded droplets were examined using cryo-transmission electron microscopy (cryo-TEM). This represents the first time such silica-loaded nanodroplets were examined in this way. The results of the cryo-TEM show that whereas the silica particles could easily be dispersed in MMA or a mixture of MMA and BuA to produce stable dispersions, the emulsification step promotes the (re)localization of the silica at the oil-water interfaces. It was also shown that not all droplets are equal; some droplets and particles contain no silica whereas others contain many silica particles. After the subsequent polymerization step, the silica was buried inside the latex particles. © 2012 American Chemical Society

  13. Silica and silica-titania sol-gel materials: synthesis and analytical application.

    PubMed

    Morosanova, Elena I

    2012-12-15

    This review describes last decade progress in the synthesis of sol-gel materials with analytically relevant properties and their application for the determination of metal ions, non-metal and organic compounds. The following types of materials are discussed: silica sol-gel materials doped with various analytical reagents, organofunctional silica sol-gel materials, and silica titania sol-gel materials. The variety of obtained materials allows their application for a wide range of analytical systems: electrochemical sensors, solid phase spectrophotometrical and SIA determination, and also for test determination including the employment of "length-of-stain" indicator tubes. This review surveys the results of studies on mentioned above subjects and summarizes the works accomplished in the field by author's team in Moscow State University.

  14. 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.

  15. Water-Silica Force Field for Simulating Nanodevices

    PubMed Central

    Cruz-Chu, Eduardo R.; Aksimentiev, Aleksei; Schulten, Klaus

    2008-01-01

    Amorphous silica is an inorganic material that is central for many nanotechnology appplications, such as nanoelectronics, microfluidics, and nanopore technology. In order to use molecular dynamics (MD) simulations to study the behavior of biomolecules with silica, we developed a force field for amorphous silica surfaces based on their macroscopic wetting properties that is compatible with the CHARMM force field and TIP3P water model. The contact angle of a water droplet with silica served as a criterion to tune the intermolecular interactions. The resulting force field was used to study the permeation of water through silica nanopores, illustrating the influence of the surface topography and the intermolecular parameters on permeation kinetics. We find that minute modeling of the amorphous surface is critical for MD studies, since the particular arrangement of surface atoms controls sensitively electrostatic interactions between silica and water. PMID:17064100

  16. 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.

  17. [Silica risk in construction industry: an investigation on raw materials].

    PubMed

    Bottai, M; Cini, A; Talini, D; Dini, F; Berti, S; Vincentini, M; Cosentino, E; Taddeo, D

    2007-01-01

    Typical construction activities like demolition, excavation and sanding can expose workers to silica, but there are few investigations carried out with the aim of evaluating the silica content in raw materials used for these activities (mortars, plasters, cement...). Our intervention has been directed in looking for free crystalline silica in samples of raw materials. We have measured the silica content in these materials comparing declared and real composition found in the products. Our intent was to obtain more information about the working activities which expose workers to free crystalline silica in construction industry and to highlight the silica presence in raw materials also when the companies don't declare it, against labeling rules based on Italian law D.lgs 65/03.

  18. Pillaring effects in macroporous carrageenan-silica composite microspheres.

    PubMed

    Boissière, M; Tourrette, A; Devoisselle, J M; Di Renzo, F; Quignard, F

    2006-02-01

    The impregnation of a carrageenan gel by a silica sol is an efficient method to form a composite material which can be conveniently activated by CO2 supercritical drying. The textural properties of the solids have been characterized by nitrogen adsorption-desorption at 77 K and their composition by thermogravimetric analysis and EDX microprobe. Morphology was examined by SEM. The silica-carrageenan composites present an open macroporous structure. Silica particles retained inside the gel behaved as pillars between the polysaccharide fibrils and form a stick-and-ball network. The stiffening of the carrageenan gel by silica prevented its shrinkage upon drying. The nature of the alkali cations affected the retention of silica particles inside the gel. In the absence of silica, carrageenan fibrils rearrange under supercritical drying and form an aerogel with cavities in the mesopore range.

  19. Non-silica aerogels as hypervelocity particle capture materials

    NASA Astrophysics Data System (ADS)

    Jones, Steven M.

    2010-01-01

    The Stardust sample return mission to the comet Wild 2 used silica aerogel as the principal cometary and interstellar particle capture and return medium. However, since both cometary dust and interstellar grains are composed largely of silica, using a silica collector complicates the science that can be accomplished with these particles. The use of non-silica aerogel in future extra-terrestrial particle capture and return missions would expand the scientific value of these missions. Alumina, titania, germania, zirconia, tin oxide, and resorcinol/formaldehyde aerogels were produced and impact tested with 20, 50, and 100μm glass microspheres to determine the suitability of different non-silica aerogels as hypervelocity particle capture mediums. It was found that non-silica aerogels do perform as efficient hypervelocity capture mediums, with alumina, zirconia, and resorcinol/formaldehyde aerogels proving to be the best of the materials tested.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. Rapid evaporation-induced synthesis of monodisperse budded silica spheres.

    PubMed

    Chen, Hongmin; He, Junhui

    2007-12-15

    Budded silica spheres have been synthesized by a novel rapid evaporation-induced self-assembly combined with the well-known Stöber method. The morphology of budded silica spheres were examined by transmission electron microscopy, and their mean size and size distribution were also estimated. Both the temperature of the sol-gel reaction and following post-treatment were found to play crucial roles in determining the surface morphology of obtained silica spheres and the yield of budded silica spheres. The possible formation mechanism was also proposed on the basis of experimental observations. The budded silica spheres would have higher surface areas than smooth silica spheres, and significant potentials for catalyst supports, building blocks of photonic crystals, and for constructing superhydrophobic and superhydrophilic surfaces.

  8. Evaluation of respirable crystalline silica in high school ceramics classrooms.

    PubMed

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

    2014-01-23

    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 excess of 21%.

  9. Silica-based nanoprobes for biomedical imaging and theranostic applications†

    PubMed Central

    Vivero-Escoto, Juan L.; Huxford-Phillips, Rachel C.

    2013-01-01

    Nanoparticle-based contrast agents are attracting a great deal of attention for various biomedical imaging and theranostic applications. Compared to conventional contrast agents, nanoparticles possess several potential advantages to improve in vivo detection and to enhance targeting efficiency. Silica-based nanoprobes can be engineered to achieve longer blood circulation times, specific clearance pathways, and multivalent binding. In this tutorial review, we summarize the latest progress on designing silica-based nanoprobes for imaging and theranostic applications. The synthesis of both solid silica and mesoporous silica nanoparticles is described, along with different approaches used for surface functionalization. Special emphasis is placed on the application of silica-based nanoprobes in optical, magnetic resonance, and multimodal imaging. The latest breakthroughs in the applications of silica nanoparticles as theranostic agents are also highlighted. PMID:22234515

  10. 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.

  11. ADL-4D6: A Silica/Silica Composite for Hardened Antenna Windows.

    DTIC Science & Technology

    1976-12-30

    advanced missile shock-resistan antenna window applications.R-it is based on RESD’s l6mni- weave I4-D reinforcement system using high purity fused...RESD have been based on the use of "Omniweave" woven preforms or rein- forcements of J.P. Stevens "Astro-quartz" high purity fused silica. Figure 1 -2...the silica fiber system, causing fiber damage (see Figure 6 of Ref. 1). Also, the dense, rigid matrix had too high an effective shear modulus, so that

  12. Synthesis of vinyl polymer-silica colloidal nanocomposites prepared using commercial alcoholic silica sols.

    PubMed

    Percy, M J; Amalvy, J I; Randall, D P; Armes, S P; Greaves, S J; Watts, J F

    2004-03-16

    The surfactant-free synthesis of vinyl polymer-silica nanocomposite particles has been achieved in aqueous alcoholic media at ambient temperature in the absence of auxiliary comonomers. Styrene, methyl methacrylate, methyl acrylate, n-butyl acrylate, and 2-hydroxypropyl methacrylate were homopolymerized in turn in the presence of three commercially available ultrafine alcoholic silica sols. Stable colloidal dispersions with reasonably narrow size distributions were obtained, with silica contents of up to 58% by mass indicated by thermogravimetric analysis. Particle size distributions were assessed using both dynamic light scattering and disk centrifuge photosedimentometry. The former technique indicated that the particle size increased for the first 1-2 h at 25 degrees C and thereafter remained constant. Particle morphologies were studied using electron microscopy. Most of the colloidal nanocomposites comprised approximately spherical particles with relatively narrow size distributions, but in some cases more polydisperse or nonspherical particles were obtained. Selected acrylate-based nanocomposites were examined in terms of their film formation behavior. Scanning electron microscopy studies indicated relatively smooth films were obtained on drying at 20 degrees C, with complete loss of the original particle morphology. The optical clarity of solution-cast 10 microm nanocomposite films was assessed using visible absorption spectrophotometry, with 93-98% transmission being obtained from 400 to 800 nm; the effect of long-term immersion of such films in aqueous solutions was also examined. X-ray photoelectron spectroscopy studies indicated that the surface compositions of these nanocomposite particles are invariably silica-rich, which is consistent with their long-term colloidal stability and also with aqueous electrophoresis measurements. FT-IR studies suggested that in the case of the poly(methyl methacrylate)-silica nanocomposite particles, the carbonyl ester

  13. Photonic integrated circuits based on silica and polymer PLC

    NASA Astrophysics Data System (ADS)

    Izuhara, T.; Fujita, J.; Gerhardt, R.; Sui, B.; Lin, W.; Grek, B.

    2013-03-01

    Various methods of hybrid integration of photonic circuits are discussed focusing on merits and challenges. Material platforms discussed in this report are mainly polymer and silica. We categorize the hybridization methods using silica and polymer waveguides into two types, chip-to-chip and on-chip integration. General reviews of these hybridization technologies from the past works are reviewed. An example for each method is discussed in details. We also discuss current status of our silica PLC hybrid integration technology.

  14. Mechanism of mechanical fatigue of silica glass. Progress report

    SciTech Connect

    Tomozawa, M.

    1993-11-01

    Results are summarized on: blunt crack tip existence, mechanical behavior of glasses with blunt cracks, water entry into glass under stress, water diffusion into SiO{sub 2} glass at low temperature, mechanical properties of glasses with high water content, cyclic fatigue, fatigue resistance improvement by coating, IR peaks of silica-water, water diffusion and structural changes in silica glasses, water diffusion and time dependent mechanical properties, effects of N and C implantation on devitrification of silica glasses.

  15. Method of manufacturing silicon from powdered material containing silica

    SciTech Connect

    Santen, S.; Edstrom, J.O.

    1984-03-27

    Silicon is manufactured from powdered material containing silica by injecting this, optionally together with a reducing agent, into a gas plasma with the help of a carrier gas. Thereafter the silica material thus heated, together with the reducing agent if any and the energy-rich plasma gas, is introduced in a reaction chamber surrounded by solid reducing agent in lump form, so that the silica is caused to melt and is reduced to liquid silicon.

  16. Structural changes in precipitated silica induced by external forces

    NASA Astrophysics Data System (ADS)

    Schneider, Gerald Johannes; Göritz, Dietmar

    2010-04-01

    The morphology of pure precipitated silica, silica filled in polydimethylsiloxane rubber, and silica filled in styrene butadiene rubber was studied by means of small-angle X-ray scattering experiments. The silica at a length scale of a few nanometers consists of primary particles, which form aggregates, and clusters with aggregates as basic units. It is evidenced that the aggregate branching, represented by the mass fractal dimension, and the aggregate diameter are different if pure silica and silica in rubber are compared. Contrary, the size of the primary particles and their surface are not influenced. It is demonstrated that the change in the aggregate morphology is due to the external mechanical forces appearing during the mixing process. This is achieved by model experiments using a pistil and a mortar and a composite with different silica fractions. By that means, a systematic change in the morphology with grinding time is observed. Then, the experiments on the composite demonstrate that the major contributions to the mass fractal dimensions are due to the external mechanical forces. In order to test reproducibility and universal validity in the case of precipitated silicas, independent experiments on one silica and further silicas are performed. Several important conclusions are obtained from the study. First, it is shown that a comparison of different pure silica samples without knowing their history may be difficult or questionable. Second, it becomes evident that it is not sufficient to provide only a description of the materials, rather than the details of the sample treatment have to be reported. Therefore, solely the characterization of the morphology of the pure silica is not sufficient to be compared to the mechanical properties of the composites.

  17. Graphene-silica composite thin films as transparent conductors.

    PubMed

    Watcharotone, Supinda; Dikin, Dmitriy A; Stankovich, Sasha; Piner, Richard; Jung, Inhwa; Dommett, Geoffrey H B; Evmenenko, Guennadi; Wu, Shang-En; Chen, Shu-Fang; Liu, Chuan-Pu; Nguyen, SonBinh T; Ruoff, Rodney S

    2007-07-01

    Transparent and electrically conductive composite silica films were fabricated on glass and hydrophilic SiOx/silicon substrates by incorporation of individual graphene oxide sheets into silica sols followed by spin-coating, chemical reduction, and thermal curing. The resulting films were characterized by SEM, AFM, TEM, low-angle X-ray reflectivity, XPS, UV-vis spectroscopy, and electrical conductivity measurements. The electrical conductivity of the films compared favorably to those of composite thin films of carbon nanotubes in silica.

  18. 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.

  19. Nanopatterned protein microrings from a diatom that direct silica morphogenesis

    PubMed Central

    Scheffel, André; Poulsen, Nicole; Shian, Samuel; Kröger, Nils

    2011-01-01

    Diatoms are eukaryotic microalgae that produce species-specifically structured cell walls made of SiO2 (silica). Formation of the intricate silica structures of diatoms is regarded as a paradigm for biomolecule-controlled self-assembly of three-dimensional, nano- to microscale-patterned inorganic materials. Silica formation involves long-chain polyamines and phosphoproteins (silaffins and silacidins), which are readily soluble in water, and spontaneously form dynamic supramolecular assemblies that accelerate silica deposition and influence silica morphogenesis in vitro. However, synthesis of diatom-like silica structure in vitro has not yet been accomplished, indicating that additional components are required. Here we describe the discovery and intracellular location of six novel proteins (cingulins) that are integral components of a silica-forming organic matrix (microrings) in the diatom Thalassiosira pseudonana. The cingulin-containing microrings are specifically associated with girdle bands, which constitute a substantial part of diatom biosilica. Remarkably, the microrings exhibit protein-based nanopatterns that closely resemble characteristic features of the girdle band silica nanopatterns. Upon the addition of silicic acid the microrings become rapidly mineralized in vitro generating nanopatterned silica replicas of the microring structures. A silica-forming organic matrix with characteristic nanopatterns was also discovered in the diatom Coscinodiscus wailesii, which suggests that preassembled protein-based templates might be general components of the cellular machinery for silica morphogenesis in diatoms. These data provide fundamentally new insight into the molecular mechanisms of biological silica morphogenesis, and may lead to the development of self-assembled 3D mineral forming protein scaffolds with designed nanopatterns for a host of applications in nanotechnology. PMID:21300899

  20. Osteoinductive silk-silica composite biomaterials for bone regeneration.

    PubMed

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

    2010-12-01

    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 the suitability of silk/silica composite system towards bone regeneration, where degradation/remodeling rates of the organic and inorganic components can be controlled. Copyright © 2010 Elsevier Ltd. All rights reserved.