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Sample records for direct genotoxic mode

  1. Further evidence against a direct genotoxic mode of action for arsenic-induced cancer

    SciTech Connect

    Klein, Catherine B.; Leszczynska, Joanna; Hickey, Christina; Rossman, Toby G.

    2007-08-01

    Arsenic in drinking water, a mixture of arsenite and arsenate, is associated with increased skin and other cancers in Asia and Latin America, but not the United States. Arsenite alone in drinking water does not cause skin cancers in experimental animals; therefore, it is not a complete carcinogen in skin. We recently showed that low concentrations of arsenite enhanced the tumorigenicity of solar UV irradiation in hairless mice, suggesting arsenic cocarcinogenesis with sunlight in skin cancer and perhaps with different carcinogenic partners for lung and bladder tumors. Cocarcinogenic mechanisms could include blocking DNA repair, stimulating angiogenesis, altering DNA methylation patterns, dysregulating cell cycle control, induction of aneuploidy and blocking apoptosis. Arsenicals are documented clastogens but not strong mutagens, with weak mutagenic activity reported at highly toxic concentrations of inorganic arsenic. Previously, we showed that arsenite, but not monomethylarsonous acid (MMA[III]), induced delayed mutagenesis in HOS cells. Here, we report new data on the mutagenicity of the trivalent methylated arsenic metabolites MMA(III) and dimethylarsinous acid [DMA(III)] at the gpt locus in Chinese hamster G12 cells. Both methylated arsenicals seemed mutagenic with apparent sublinear dose responses. However, significant mutagenesis occurred only at highly toxic concentrations of MMA(III). Most mutants induced by MMA(III) and DMA(III) exhibited transgene deletions. Some non-deletion mutants exhibited altered DNA methylation. A critical discussion of cell survival leads us to conclude that clastogenesis occurs primarily at highly cytotoxic arsenic concentrations, casting further doubt as to whether a genotoxic mode of action (MOA) for arsenicals is supportable.

  2. Comparison of in vivo genotoxic and carcinogenic potency to augment mode of action analysis: Case study with hexavalent chromium.

    PubMed

    Thompson, Chad M; Bichteler, Anne; Rager, Julia E; Suh, Mina; Proctor, Deborah M; Haws, Laurie C; Harris, Mark A

    2016-04-01

    Recent analyses-highlighted by the International Workshops on Genotoxicity Testing Working Group on Quantitative Approaches to Genetic Toxicology Risk Assessment-have identified a correlation between (log) estimates of a carcinogen's in vivo genotoxic potency and in vivo carcinogenic potency in typical laboratory animal models, even when the underlying data have not been matched for tissue, species, or strain. Such a correlation could have important implications for risk assessment, including informing the mode of action (MOA) of specific carcinogens. When in vivo genotoxic potency is weak relative to carcinogenic potency, MOAs other than genotoxicity (e.g., endocrine disruption or regenerative hyperplasia) may be operational. Herein, we review recent in vivo genotoxicity and carcinogenicity data for hexavalent chromium (Cr(VI)), following oral ingestion, in relevant tissues and species in the context of the aforementioned correlation. Potency estimates were generated using benchmark doses, or no-observable-adverse-effect-levels when data were not amenable to dose-response modeling. While the ratio between log values for carcinogenic and genotoxic potency was ≥1 for many compounds, the ratios for several Cr(VI) datasets (including in target tissue) were less than unity. In fact, the ratios for Cr(VI) clustered closely with ratios for chloroform and diethanolamine, two chemicals posited to have non-genotoxic MOAs. These findings suggest that genotoxicity may not play a major role in the cancers observed in rodents following exposure to high concentrations of Cr(VI) in drinking water-a finding consistent with recent MOA and adverse outcome pathway (AOP) analyses concerning Cr(VI). This semi-quantitative analysis, therefore, may be useful to augment traditional MOA and AOP analyses. More case examples will be needed to further explore the general applicability and validity of this approach for human health risk assessment. PMID:27085472

  3. Mutagenic and genotoxic potential of direct electric current in Escherichia coli and Salmonella thyphimurium strains.

    PubMed

    Gomes, Marina das Neves; Cardoso, Janine Simas; Leitão, Alvaro Costa; Quaresma, Carla Holandino

    2016-05-01

    Direct electric current has several therapeutic uses such as antibacterial and antiprotozoal action, tissues scarring and regeneration, as well as tumor treatment. This method has shown promising results in vivo and in vitro, with significant efficacy and almost no side effects. Considering lack of studies regarding direct electric current mutagenic and/or genotoxic effects, the present work evaluated both aspects by using five different bacterial experimental assays: survival of repair-deficient mutants, Salmonella-histidine reversion mutagenesis (Ames test), forward mutations to rifampicin resistance, phage reactivation, and lysogenic induction. In these experimental conditions, cells were submitted to an approach that allows evaluation of anodic, cathodic, and electro-ionic effects generated by 2 mA of direct electric current, with doses ranging from 0.36 to 3.60 Coulombs. Our results showed these doses did not induce mutagenic or genotoxic effects. Bioelectromagnetics. 37:234-243, 2016. © 2016 Wiley Periodicals, Inc. PMID:27018544

  4. Genotoxic mode of action predictions from a multiplexed flow cytometric assay and a machine learning approach.

    PubMed

    Bryce, Steven M; Bernacki, Derek T; Bemis, Jeffrey C; Dertinger, Stephen D

    2016-04-01

    Several endpoints associated with cellular responses to DNA damage as well as overt cytotoxicity were multiplexed into a miniaturized, "add and read" type flow cytometric assay. Reagents included a detergent to liberate nuclei, RNase and propidium iodide to serve as a pan-DNA dye, fluorescent antibodies against γH2AX, phospho-histone H3, and p53, and fluorescent microspheres for absolute nuclei counts. The assay was applied to TK6 cells and 67 diverse reference chemicals that served as a training set. Exposure was for 24 hrs in 96-well plates, and unless precipitation or foreknowledge about cytotoxicity suggested otherwise, the highest concentration was 1 mM. At 4- and 24-hrs aliquots were removed and added to microtiter plates containing the reagent mix. Following a brief incubation period robotic sampling facilitated walk-away data acquisition. Univariate analyses identified biomarkers and time points that were valuable for classifying agents into one of three groups: clastogenic, aneugenic, or non-genotoxic. These mode of action predictions were optimized with a forward-stepping process that considered Wald test p-values, receiver operator characteristic curves, and pseudo R(2) values, among others. A particularly high performing multinomial logistic regression model was comprised of four factors: 4 hr γH2AX and phospho-histone H3 values, and 24 hr p53 and polyploidy values. For the training set chemicals, the four-factor model resulted in 94% concordance with our a priori classifications. Cross validation occurred via a leave-one-out approach, and in this case 91% concordance was observed. A test set of 17 chemicals that were not used to construct the model were evaluated, some of which utilized a short-term treatment in the presence of a metabolic activation system, and in 16 cases mode of action was correctly predicted. These initial results are encouraging as they suggest a machine learning strategy can be used to rapidly and reliably predict new chemicals

  5. Mode selective directional coupler for NLC

    SciTech Connect

    Tantawi, S.G.

    1994-10-01

    The design method for a high power, X-band, 50 dB, circular to rectangular directional coupler is presented. The circular guide is over moded and is intended to operate in TE{sub 01} mode. The rectangular guide operates at the fundamental TE{sub 10} mode. A small percentage of higher order modes in the circular guide can cause considerable errors in the measurements because the magnitude of the axial magnetic field of these modes is higher than that of the operating mode, especially near their cutoff. We used a Hamming window patten for the coupling slots to achieve mode selectivity. Comparison of theory and experiment will be presented.

  6. Evaluation of genotoxic effects of surface waters using a battery of bioassays indicating different mode of action.

    PubMed

    Han, Yingnan; Li, Na; Oda, Yoshimitsu; Ma, Mei; Rao, Kaifeng; Wang, Zijian; Jin, Wei; Hong, Gang; Li, Zhiguo; Luo, Yi

    2016-11-01

    With the burgeoning contamination of surface waters threatening human health, the genotoxic effects of surface waters have received much attention. Because mutagenic and carcinogenic compounds in water cause tumors by different mechanisms, a battery of bioassays that each indicate a different mode of action (MOA) is required to evaluate the genotoxic effects of contaminants in water samples. In this study, 15 water samples from two source water reservoirs and surrounding rivers in Shijiazhuang city of China were evaluated for genotoxic effects. Target chemical analyses of 14 genotoxic pollutants were performed according to the Environmental quality standards for surface water of China. Then, the in vitro cytokinesis-block micronucleus (CBMN) assay, based on a high-content screening technique, was used to detect the effect of chromosome damage. The SOS/umu test using strain TA1535/pSK1002 was used to detect effects on SOS repair of gene expression. Additionally, two other strains, NM2009 and NM3009, which are highly sensitive to aromatic amines and nitroarenes, respectively, were used in the SOS/umu test to avoid false negative results. In the water samples, only two of the genotoxic chemicals listed in the water standards were detected in a few samples, with concentrations that were below water quality standards. However, positive results for the CBMN assay were observed in two river samples, and positive results for the induction of umuC gene expression in TA1535/pSK1002 were observed in seven river samples. Moreover, positive results were observed for NM2009 with S9 and NM3009 without S9 in some samples that had negative results using the strain TA1535/pSK1002. Based on the results with NM2009 and NM3009, some unknown or undetected aromatic amines and nitroarenes were likely in the source water reservoirs and the surrounding rivers. Furthermore, these compounds were most likely the causative pollutants for the genotoxic effect of these water samples. Therefore

  7. Considering mutagenicity and genotoxicity in the cancer mode of action for naphthalene, styrene, and ethylbenzene

    EPA Science Inventory

    It is well known that genotoxicity plays a significant role in the development of tumor formation. Mutations in somatic cells can play a key role early in cancer initiation and might affect other stages of the carcinogenic process. Determination of carcinogens that operate throug...

  8. ARSENIC (III) METHYLATED SPECIES REACT WITH DNA DIRECTLY AND COULD BE PROXIMATED/ULTIMATE GENOTOXIC FORMS OF ARSENIC

    EPA Science Inventory


    ARSENIC(III) METHYLATED SPECIES REACT WITH DNA DIRECTL Y AND COULD BE PROXIMATE/ULTIMATE GENOTOXIC FORMS OF ARSENIC


    Arsenite and arsenate (iAs, inorganic arsenic) have been thought to act as genotoxicants without reacting directly with DNA; neither iAs nor As(V) m...

  9. Sensitivity of Allium and Nicotiana in cellular and acellular comet assays to assess differential genotoxicity of direct and indirect acting mutagens.

    PubMed

    Bandyopadhyay, Atrayee; Mukherjee, Anita

    2011-05-01

    We have evaluated the extent of DNA damage induced by direct and indirect mutagens by cellular and acellular comet assays in two plant systems, Nicotiana tabacum (wild type tobacco) and Allium cepa (common onion). The objectives of this study were: (1) to generate dose-response curves for DNA migration values from root and shoot nuclei of A. cepa and N. tabacum treated with the direct acting mutagens, ethyl methanesulphonate (EMS), hydrogen peroxide (H(2)O(2)) and the indirect acting mutagen, cadmium chloride (CdCl(2)), (2) to assess the differential response between isolated nuclei and nuclei of root and shoot and of both plants and (3) to examine the differences of sensitivity between direct and indirect acting mutagens by cellular and acellular comet assays. Similar sensitivities were evident in both plant systems to direct and indirect acting mutagens. The combination of cellular and acellular comet assays provided valuable insight to the mode of action of the genotoxicants used. The data obtained demonstrated the estimable capacity of the two plant systems to evaluate genotoxicity under different stress conditions and suggests Allium is a more desirable test system for rapid monitoring of genotoxicity. PMID:21237510

  10. Genotoxicity of tri- and hexavalent chromium compounds in vivo and their modes of action on DNA damage in vitro.

    PubMed

    Fang, Zhijia; Zhao, Min; Zhen, Hong; Chen, Lifeng; Shi, Ping; Huang, Zhiwei

    2014-01-01

    Chromium occurs mostly in tri- and hexavalent states in the environment. Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements. In the present work, we report that they both induce genetic mutations in yeast cells. They both also cause DNA damage in both yeast and Jurkat cells and the effect of Cr(III) is greater than that of Cr(VI). We further show that Cr(III) and Cr(VI) cause DNA damage through different mechanisms. Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking. Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo. PMID:25111056

  11. Genotoxicity of Tri- and Hexavalent Chromium Compounds In Vivo and Their Modes of Action on DNA Damage In Vitro

    PubMed Central

    Fang, Zhijia; Zhao, Min; Zhen, Hong; Chen, Lifeng; Shi, Ping; Huang, Zhiwei

    2014-01-01

    Chromium occurs mostly in tri- and hexavalent states in the environment. Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements. In the present work, we report that they both induce genetic mutations in yeast cells. They both also cause DNA damage in both yeast and Jurkat cells and the effect of Cr(III) is greater than that of Cr(VI). We further show that Cr(III) and Cr(VI) cause DNA damage through different mechanisms. Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking. Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo. PMID:25111056

  12. SOME INSIGHTS INTO THE MODE OF ACTION OF BUTADIENE BY EXAMINING THE GENOTOXICITY OF ITS METABOLITES

    EPA Science Inventory

    1,3-Butadiene (BTD) is an important commodity chemical and air pollutant that has been shown to be a potent carcinogen in mice, and to a lesser extent, a carcinogen in rats. To better assess butadiene's carcinogenic risk to humans, it is important to understand its mode of action...

  13. On-chip optical mode exchange using tapered directional coupler

    PubMed Central

    Zhang, Zhonglai; Hu, Xiao; Wang, Jian

    2015-01-01

    We present an on-chip optical mode exchange between two multiplexed modes by using tapered directional couplers on silicon-on-insulator platform. The device consisting of mode multiplexing and mode exchange is compact with relatively large fabrication error tolerance. The simulation results show efficient higher order mode excitation and mode exchange. A low excess loss less than 0.5 dB and high extinction ratio larger than 15 dB over 10 nm wavelength range from 1535 to 1545 nm are achieved. PMID:26530728

  14. Mode characteristics and directional emission for square microcavity lasers

    NASA Astrophysics Data System (ADS)

    Yang, Yue-De; Huang, Yong-Zhen

    2016-06-01

    Square microcavities with high quality factor whispering-gallery-like modes have a series of novel optical properties and can be employed as compact-size laser resonators. In this paper, the mode characteristics of square optical microcavities and the lasing properties of directional-emission square semiconductor microlasers are reviewed for the realization of potential light sources in the photonic integrated circuits and optical interconnects. A quasi-analytical model is introduced to describe the confined modes in square microcavities, and high quality factor whispering-gallery-like modes are predicted by the mode-coupling theory and confirmed by the numerical simulation. An output waveguide directly coupled to the position with weak mode field is used to achieve directional emission and control the lasing mode. Electrically-pumped InP-based directional-emission square microlasers are realized at room temperature, and the lasing spectra agree well with the mode analysis. Different kinds of square microcavity lasers, including dual-mode laser with a tunable interval, single-mode laser with a wide tunable wavelength range, and high-speed direct-modulated laser are also demonstrated experimentally.

  15. Variable mode bi-directional and uni-directional computer communication system

    DOEpatents

    Cornett, Frank N.; Jenkins, Philip N.; Bowman, Terrance L.; Placek, Joseph M.; Thorson, Gregory M.

    2004-12-14

    A variable communication systems comprising a plurality of transceivers and a control circuit connected to the transceivers to configure the transceivers to operate in a bi-directional mode and a uni-directional mode at different times using different transfer methods to transfer data.

  16. Azimuthal Directivity of Fan Tones Containing Multiple Modes

    NASA Technical Reports Server (NTRS)

    Heidelberg, Laurence J.; Sutliff, Daniel L.; Nallasamy, M.

    1997-01-01

    The directivity of fan tone noise is generally measured and plotted in the sideline or flyover plane and it is assumed that this curve is the same for all azimuthal angles. When two or more circumferential (m-order) modes of the same tone are present in the fan duct, an interference pattern develops in the azimuthal direction both in the duct and in the farfield. In this investigation two m-order modes of similar power were generated in a large low speed fan. Farfield measurements and a finite element propagation code both show substantial variations in the azimuthal direction. Induct mode measurement were made and used as input to the code. Although these tests may represent a worst case scenario, the validity of the current practice of assuming axisymmetry should be questioned.

  17. A metabolomics investigation of non genotoxic carcinogenicity in the rat

    PubMed Central

    Ament, Zsuzsanna; Waterman, Claire L; West, James A; Waterfield, Catherine; Currie, Richard A; Wright, Jayne; Griffin, Julian L

    2014-01-01

    Non-genotoxic carcinogens (NGCs) promote tumour growth by altering gene expression which ultimately leads to cancer without directly causing a change in DNA sequence. As a result NGCs are not detected in mutagenesis assays. Whilst there are proposed biomarkers of carcinogenic potential, the definitive identification of non-genotoxic carcinogens still rests with the rat and mouse long term bioassay. Such assays are expensive, time consuming, require a large number of animals and their relevance to human health risk assessments is debatable. Metabolomics and lipidomics in combination with pathology and clinical chemistry were used to profile perturbations produced by 10 compounds which represented a range of rat non-genotoxic hepatocarcinogens (NGC), non-genotoxic non-hepatocarcinogens (non-NGC) and a genotoxic hepatocarcinogen. Each compound was administered at its maximum tolerated dose level for 7, 28 and 91 days to male Fisher 344 rats. Changes in liver metabolite concentration differentiated the treated groups across different time points. The most significant differences were driven by pharmacological mode of action, specifically by the peroxisome proliferator activated receptor alpha (PPAR-α) agonists. Despite these dominant effects, good predictions could be made when differentiating NGCs from non-NGCs. Predictive ability measured by leave one out cross validation was 87% and 77% after 28 days of dosing for NGCs and non-NGCs, respectively. Amongst the discriminatory metabolites we identified free fatty acids, phospholipids, triacylglycerols, as well as precursors of eicosanoid and the products of reactive oxygen species linked to processes of inflammation, proliferation and oxidative stress. Thus, metabolic profiling is able to identify changes due to the pharmacological mode of action of xenobiotics and contribute to early screening for non-genotoxic potential. PMID:24161236

  18. Chiral modes and directional lasing at exceptional points

    PubMed Central

    Peng, Bo; Özdemir, Şahin Kaya; Liertzer, Matthias; Chen, Weijian; Kramer, Johannes; Yılmaz, Huzeyfe; Wiersig, Jan; Yang, Lan

    2016-01-01

    Controlling the emission and the flow of light in micro- and nanostructures is crucial for on-chip information processing. Here we show how to impose a strong chirality and a switchable direction of light propagation in an optical system by steering it to an exceptional point (EP)—a degeneracy universally occurring in all open physical systems when two eigenvalues and the corresponding eigenstates coalesce. In our experiments with a fiber-coupled whispering-gallery-mode (WGM) resonator, we dynamically control the chirality of resonator modes and the emission direction of a WGM microlaser in the vicinity of an EP: Away from the EPs, the resonator modes are nonchiral and laser emission is bidirectional. As the system approaches an EP, the modes become chiral and allow unidirectional emission such that by transiting from one EP to another one the direction of emission can be completely reversed. Our results exemplify a very counterintuitive feature of non-Hermitian physics that paves the way to chiral photonics on a chip. PMID:27274059

  19. Chiral modes and directional lasing at exceptional points.

    PubMed

    Peng, Bo; Özdemir, Şahin Kaya; Liertzer, Matthias; Chen, Weijian; Kramer, Johannes; Yılmaz, Huzeyfe; Wiersig, Jan; Rotter, Stefan; Yang, Lan

    2016-06-21

    Controlling the emission and the flow of light in micro- and nanostructures is crucial for on-chip information processing. Here we show how to impose a strong chirality and a switchable direction of light propagation in an optical system by steering it to an exceptional point (EP)-a degeneracy universally occurring in all open physical systems when two eigenvalues and the corresponding eigenstates coalesce. In our experiments with a fiber-coupled whispering-gallery-mode (WGM) resonator, we dynamically control the chirality of resonator modes and the emission direction of a WGM microlaser in the vicinity of an EP: Away from the EPs, the resonator modes are nonchiral and laser emission is bidirectional. As the system approaches an EP, the modes become chiral and allow unidirectional emission such that by transiting from one EP to another one the direction of emission can be completely reversed. Our results exemplify a very counterintuitive feature of non-Hermitian physics that paves the way to chiral photonics on a chip. PMID:27274059

  20. Direct Optical Probing of Transverse Electric Mode in Graphene

    PubMed Central

    Menabde, Sergey G.; Mason, Daniel R.; Kornev, Evgeny E.; Lee, Changhee; Park, Namkyoo

    2016-01-01

    Unique electrodynamic response of graphene implies a manifestation of an unusual propagating and localised transverse-electric (TE) mode near the spectral onset of interband transitions. However, excitation and further detection of the TE mode supported by graphene is considered to be a challenge for it is extremely sensitive to excitation environment and phase matching condition adherence. Here for the first time, we experimentally prove an existence of the TE mode by its direct optical probing, demonstrating significant coupling to an incident wave in electrically doped multilayer graphene sheet at room temperature. We believe that proposed technique of careful phase matching and obtained access to graphene’s TE excitation would stimulate further studies of this unique phenomenon, and enable its potential employing in various fields of photonics as well as for characterization of graphene. PMID:26898892

  1. Direct Optical Probing of Transverse Electric Mode in Graphene

    NASA Astrophysics Data System (ADS)

    Menabde, Sergey G.; Mason, Daniel R.; Kornev, Evgeny E.; Lee, Changhee; Park, Namkyoo

    2016-02-01

    Unique electrodynamic response of graphene implies a manifestation of an unusual propagating and localised transverse-electric (TE) mode near the spectral onset of interband transitions. However, excitation and further detection of the TE mode supported by graphene is considered to be a challenge for it is extremely sensitive to excitation environment and phase matching condition adherence. Here for the first time, we experimentally prove an existence of the TE mode by its direct optical probing, demonstrating significant coupling to an incident wave in electrically doped multilayer graphene sheet at room temperature. We believe that proposed technique of careful phase matching and obtained access to graphene’s TE excitation would stimulate further studies of this unique phenomenon, and enable its potential employing in various fields of photonics as well as for characterization of graphene.

  2. Transient mode competition in directly modulated DFB semiconductor laser

    NASA Astrophysics Data System (ADS)

    Xiao, RuLei; Shi, YueChun; Zheng, JiLin; Zhang, YunShan; Zheng, JunShou; Chen, XiangFei

    2015-12-01

    A new effect of transient mode competition in directly modulated DFB laser based on equivalent phase-shift (EPS) technique is presented and studied. Since there are multi-order reflections in EPS structure and if the 0th order subgrating is properly designed, the transient lasing of 0th order will occur during the rising time of the injection current. As a result, transient mode competition between -1st order (main mode) and 0th order will occur accordingly. This can consume redundant carrier and suppress the transient relaxation oscillation, which may be applied in some areas like on-off switching modulation of DFB semiconductor lasers. As an example, an equivalent π phase shift (π-EPS) is carefully designed to realize the effect. In such a laser the 0th order wavelength is in the margin of the material gain region and the -1st order wavelength is around the gain peak, while the stable single longitudinal mode (SLM) operation of the -1st order is guaranteed. The simulation investigation is performed. Good results with suppressed relaxation oscillation and 1.25 Gb/s directly on-off modulation (32 dB extinction ratio) are demonstrated. We believe it provides a new kind of method for on-off switching with high extinction ratio and weak relaxation oscillation.

  3. Comparing Direct and Semi-Direct Modes for Speaking Assessment: Affective Effects on Test Takers

    ERIC Educational Resources Information Center

    Qian, David D.

    2009-01-01

    In recent decades, with an increasing application of computer technology to the delivery of oral language proficiency assessment, there have been renewed debates over the appropriateness of two different testing modes, namely, (a) face-to-face, or direct, testing, and (b) person-to-machine, or semi-direct, testing. Previous research conducted in…

  4. Arsenic Is A Genotoxic Carcinogen

    EPA Science Inventory

    Arsenic is a recognized human carcinogen; however, there is controversy over whether or not it should be considered a genotoxic carcinogen. Many possible modes of action have been proposed on how arsenic induces cancer, including inhibiting DNA repair, altering methylation patter...

  5. SOS chromotest, a direct assay of induction of an SOS function in Escherichia coli K-12 to measure genotoxicity.

    PubMed Central

    Quillardet, P; Huisman, O; D'Ari, R; Hofnung, M

    1982-01-01

    We present and evaluate the SOS chromotest, a bacterial test for detecting DNA-damaging agents. It is a colorimetric assay based on the induction by these agents of the SOS function sfiA, whose level of expression is monitored by means of a sfiA::lacZ operon fusion. The response is rapid (a few hours), and does not require survival of the tester strain. Dose-response curves for various chemicals include a linear region. The slope of this region is taken as a measure of the SOS inducing potency. Comparison for a number of substances of known genotoxicity of the SOS inducing potency determined in the SOS chromotest with the mutagenic potency determined in the Salmonella assay (mutatest) revealed a striking quantitative correlation over more than 7 orders of magnitude. The sensitivity of the SOS chromotest (lowest amount detected) is equal to that of the mutatest and generally 4-40 times higher than that of a phage induction assay (inductest). From a practical point of view our observations contribute to the validation of the SOS chromotest as a test for detecting genotoxins and in particular genotoxic carcinogens. From a theoretical standpoint the results suggest that mutagenic potency measured in the mutatest reflects the level of induction of an SOS function and that most genotoxins are inducers of the SOS response in bacteria. PMID:6821127

  6. SOS Chromotest, a Direct Assay of Induction of an SOS Function in Escherichia coli K-12 to Measure Genotoxicity

    NASA Astrophysics Data System (ADS)

    Quillardet, Philippe; Huisman, Olivier; D'Ari, Richard; Hofnung, Maurice

    1982-10-01

    We present and evaluate the SOS chromotest, a bacterial test for detecting DNA-damaging agents. It is a colorimetric assay based on the induction by these agents of the SOS function sfiA, whose level of expression is monitored by means of a sfiA::lacZ operon fusion. The response is rapid (a few hours), and does not require survival of the tester strain. Dose-response curves for various chemicals include a linear region. The slope of this region is taken as a measure of the SOS inducing potency. Comparison for a number of substances of known genotoxicity of the SOS inducing potency determined in the SOS chromotest with the mutagenic potency determined in the Salmonella assay (mutatest) revealed a striking quantitative correlation over more than 7 orders of magnitude. The sensitivity of the SOS chromotest (lowest amount detected) is equal to that of the mutatest and generally 4-40 times higher than that of a phage induction assay (inductest). From a practical point of view our observations contribute to the validation of the SOS chromotest as a test for detecting genotoxins and in particular genotoxic carcinogens. From a theoretical standpoint the results suggest that mutagenic potency measured in the mutatest reflects the level of induction of an SOS function and that most genotoxins are inducers of the SOS response in bacteria.

  7. Bacterial genotoxicity bioreporters

    PubMed Central

    Biran, Alva; Yagur‐Kroll, Sharon; Pedahzur, Rami; Buchinger, Sebastian; Reifferscheid, Georg; Ben‐Yoav, Hadar; Shacham‐Diamand, Yosi; Belkin, Shimshon

    2010-01-01

    Summary Ever since the introduction of the Salmonella typhimurium mammalian microsome mutagenicity assay (the ‘Ames test’) over three decades ago, there has been a constant development of additional genotoxicity assays based upon the use of genetically engineered microorganisms. Such assays rely either on reversion principles similar to those of the Ames test, or on promoter–reporter fusions that generate a quantifiable dose‐dependent signal in the presence of potential DNA damaging compounds and the induction of repair mechanisms; the latter group is the subject of the present review. Some of these assays were only briefly described in the scientific literature, whereas others have been developed all the way to commercial products. Out of these, only one, the umu‐test, has been fully validated and ISO‐ and OECD standardized. Here we review the main directions undertaken in the construction and testing of bacterial‐based genotoxicity bioassays, including the attempts to incorporate at least a partial metabolic activation capacity into the molecular design. We list the genetic modifications introduced into the tester strains, compare the performance of the different assays, and briefly describe the first attempts to incorporate such bacterial reporters into actual genotoxicity testing devices. PMID:21255340

  8. Robustness of superconducting quantum modes against direct quasiparticle injection

    NASA Astrophysics Data System (ADS)

    Patel, U.; Nsanzineza, I.; Vavilov, M. G.; Plourde, B. L. T.; McDermott, R.

    Classical Josephson digital logic based on Single Flux Quantum (SFQ) pulses offers a path to high-fidelity coherent control of large-scale superconducting quantum machines. However, an SFQ pulse driver generates nonequilibrium quasiparticles that contribute to qubit relaxation, and steps must be taken to protect the qubit from this decoherence channel. Here we describe experiments to characterize the robustness of high-Q superconducting linear resonators and qubits against direct quasiparticle injection. We use NIS junctions and SFQ elements to controllably inject quasiparticles into the groundplane of superconducting resonator and qubit chips, and we characterize the quasiparticle contribution to dissipation. We examine the effectiveness of groundplane cuts, normal metal quasiparticle traps, and spatially-varying superconducting gaps at protecting the quantum modes against quasiparticle loss. Finally, we discuss strategies for the integration of multiqubit circuits with on-chip SFQ control elements.

  9. Multihit mode direct-detection laser radar system using a Geiger-mode avalanche photodiode.

    PubMed

    Oh, Min Seok; Kong, Hong Jin; Kim, Tae Hoon; Hong, Keun Ho; Kim, Byung Wook; Park, Dong Jo

    2010-03-01

    In this paper, a direct-detection laser radar system that uses a Geiger-mode avalanche photodiode (GAPD) of relatively short dead time (45 ns) is described. A passively Q-switched microchip laser is used as a laser source and a compact peripheral component interconnect system, which includes a time-to-digital converter (TDC), is set up for fast signal processing. With both the GAPD and the TDC functioning multistop acquisition, the system operates in a multihit mode. The software for the three-dimensional visualization and an algorithm for the removal of noise are developed. It is shown that the single-shot precision of the system is approximately 10 cm (sigma) and the precision is improved by increasing the number of laser pulses to be averaged so that the precision of approximately 1 cm (sigma) was acquired with more than 150 laser pulses scattered from the target. The accuracy of the system is measured to be 12 cm when the energy of the emitted laser pulse varies with a factor of 7. PMID:20370163

  10. Convenient, multi-well plate-based DNA damage response analysis using DT40 mutants is applicable to a high-throughput genotoxicity assay with characterization of modes of action

    PubMed Central

    Ridpath, John R.; Takeda, Shunichi; Swenberg, James A.; Nakamura, Jun

    2012-01-01

    Chemists continually synthesize myriad new chemicals (~2000/yr), some of which make their way into the environment or otherwise pose possible threats to humans who potentially become exposed to the compounds. Regulators must determine whether these, along with the glut (~80,000) of existing, chemicals are toxic and at what exposure levels. An important component of this determination is to ascertain the mode of action (MOA) of each compound as it relates to the pathway the compound uses to induce genotoxicity. Several assays have traditionally been used to reveal these effects to the genome: the Ames test, tests with yeast and mammalian cell lines, and animal studies. Previously, we described a new multi-well plate-based method which makes use of the DT40 isogenic cell line and its dozens of available mutants knocked out in DNA repair and cell cycle pathways and we now provide a detailed protocol of the further improvement of the assay. Although the DT40 line has existed for some time and has been used in numerous studies of DNA repair pathways, little use has been made of this valuable resource for toxicological investigations. Our method introduces the XTT dye scheme determination of cell survival in a manner that greatly increases throughput and reduces cost while maintaining reasonable sensitivity. Although this new genotoxicity assay requires validation with many more mutagens before becoming an established, regulatory decision-making analysis tool, we believe that this method will be very advantageous if eventually added to the repertoire of those investigating MOAs of potentially genotoxic substances. PMID:20839229

  11. Direct electrical-to-optical conversion and light modulation in micro whispering-gallery-mode resonators

    NASA Technical Reports Server (NTRS)

    Maleki, Lute (Inventor); Levi, Anthony F. J. (Inventor)

    2005-01-01

    Techniques for directly converting an electrical signal into an optical signal by using a whispering gallery mode optical resonator formed of a dielectric material that allows for direct modulation of optical absorption by the electrical signal.

  12. Influence of anoxia and respiratory deficiency on the genotoxicity of some direct-acting alkylating agents in yeast.

    PubMed

    Deorukhakar, V V; Murthy, M S

    1991-01-01

    We have studied the influence of anoxia and respiratory deficiency (RD) in yeast on the cytotoxic and recombinogenic effects of 5 direct-acting alkylating agents, namely N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), methylnitrosourea (MNU), ethylnitrosourea (ENU), methyl methanesulphonate (MMS) and ethyl methanesulphonate (EMS). We found that the effects of both conditions parallel each other for MMS, MNNG, MNU and ENU. Both anoxia and RD did not modify the effects of MMS to any significant extent. On the other hand, anoxic and respiratory-deficient cells were found to be more resistant than euoxic and respiratory-proficient cells respectively for MNNG, MNU and ENU. In the case of EMS, which is similar to MMS in its chemical reaction with DNA, the respiratory-deficient cells were found to be more sensitive than the respiratory-proficient ones. These studies indicate that the response of anoxic and respiratory-deficient cells cannot be predicted solely on the basis of the chemical reactivity pattern of the alkylating agents. The physiological state which exists under these conditions may exert considerable influence on the cellular response. PMID:1846028

  13. Interactions between directly- and parametrically-driven vibration modes in a micromechanical resonator

    NASA Astrophysics Data System (ADS)

    Westra, H. J. R.; Karabacak, D. M.; Brongersma, S. H.; Crego-Calama, M.; van der Zant, H. S. J.; Venstra, W. J.

    2011-10-01

    The interactions between parametrically- and directly-driven vibration modes of a clamped-clamped beam resonator are studied. An integrated piezoelectric transducer is used for direct and parametric excitation. First, the parametric amplification and oscillation of a single mode are analyzed by the power and phase dependence below and above the threshold for parametric oscillation. Then, the motion of a parametrically-driven mode is detected by the induced change in resonance frequency in another mode of the same resonator. The resonance frequency shift is the result of the nonlinear coupling between the modes by the displacement-induced tension in the beam. These nonlinear modal interactions result in the quadratic relation between the resonance frequency of one mode and the amplitude of another mode. The amplitude of a parametrically-oscillating mode depends on the square root of the pump frequency. Combining these dependencies yields a linear relation between the resonance frequency of the directly-driven mode and the frequency of the parametrically-oscillating mode.

  14. Spurious Modes in Spectral Collocation Methods with Two Non-Periodic Directions

    NASA Technical Reports Server (NTRS)

    Balachandar, S.; Madabhushi, Ravi K.

    1992-01-01

    Collocation implementation of the Kleiser-Schumann's method in geometries with two non-periodic directions is shown to suffer from three spurious modes - line, column and checkerboard - contaminating the computed pressure field. The corner spurious modes are also present but they do not affect evaluation of pressure related quantities. A simple methodology in the inversion of the influence matrix will efficiently filter out these spurious modes.

  15. Numerical Simulation of Direct Exitation of the TE11 Mode in a Coaxial Vircator

    NASA Astrophysics Data System (ADS)

    Möller, Cecilia; Hurtig, Tomas; Larsson, Anders; Nyholm, Sten E.

    Studies of the concept of direct excitation of the TE11 mode in a coaxial vircator using three-dimensional particle-in-cell simulations is presented. The excitation of the TE11 mode is made possible by sectioning the emitting surface of the cathode, thus creating two interacting virtual cathodes. It is shown that the two virtual cathodes formed oscillate in push-pull mode as previously has been described for a planar geometry.

  16. Directional couplers for detecting the TE sub 11 and TE sub 12 circular waveguide modes

    NASA Technical Reports Server (NTRS)

    Hoppe, D.

    1987-01-01

    The theoretical and experimental results for a pair of mode-selective directional couplers designed to detect the TE sub 11 and TE sub 12 modes in a multimode circular wavelength are described. A brief description of the design of the couplers is presented, followed by a comparison of their measured and calculated parameters. The couplers were used to measure the characteristics of a circular waveguide mode converter. The results of these measurements are described.

  17. Direct coupling of photonic modes and surface plasmon polaritons observed in 2-photon PEEM.

    PubMed

    Word, Robert C; Fitzgerald, Joseph P S; Könenkamp, Rolf

    2013-12-16

    We report the direct microscopic observation of optical energy transfer from guided photonic modes in an indium tin oxide (ITO) thin film to surface plasmon polaritons (SPP) at the surfaces of a single crystalline gold platelet. The photonic and SPP modes appear as an interference pattern in the photoelectron emission yield across the surface of the specimen. We explore the momentum match between the photonic and SPP modes in terms of simple waveguide theory and the three-layer slab model for bound SPP modes of thin metal films. We show that because the gold is thin (30-40 nm), two SPP modes exist and that momentum of the spatially confined asymmetric field mode coincides with the dominant mode of the ITO waveguide. The results demonstrate that photoemission electron microscopy (PEEM) can be an important tool for the observation of photonic to SPP interactions in the study of integrated photonic circuits. PMID:24514628

  18. Integrated dual-mode 3 dB power coupler based on tapered directional coupler

    PubMed Central

    Luo, Yuchan; Yu, Yu; Ye, Mengyuan; Sun, Chunlei; Zhang, Xinliang

    2016-01-01

    A dual-mode 3 dB power coupler based on silicon-on-insulator platform for mode division multiplexing system is proposed and demonstrated. The device, which consists of a tapered directional coupler and two output bend waveguides, has a 50:50 coupling ratio around the wavelength of 1550 nm for both fundamental and first order transverse magnetic (TM0 and TM1) modes. Based on asymmetrical tapered structure, a short common coupling length of ~15.2 μm for both modes is realized by optimizing the width of the tapered waveguide. The measured insertion loss for both modes is less than 0.7 dB. The crosstalks are about −14.3 dB for TM0 mode and −18.1 dB for TM1 mode. PMID:27002747

  19. Integrated dual-mode 3 dB power coupler based on tapered directional coupler.

    PubMed

    Luo, Yuchan; Yu, Yu; Ye, Mengyuan; Sun, Chunlei; Zhang, Xinliang

    2016-01-01

    A dual-mode 3 dB power coupler based on silicon-on-insulator platform for mode division multiplexing system is proposed and demonstrated. The device, which consists of a tapered directional coupler and two output bend waveguides, has a 50:50 coupling ratio around the wavelength of 1550 nm for both fundamental and first order transverse magnetic (TM0 and TM1) modes. Based on asymmetrical tapered structure, a short common coupling length of ~15.2 μm for both modes is realized by optimizing the width of the tapered waveguide. The measured insertion loss for both modes is less than 0.7 dB. The crosstalks are about -14.3 dB for TM0 mode and -18.1 dB for TM1 mode. PMID:27002747

  20. Direct determination of the number of transverse modes of a light beam.

    PubMed

    Karny, Z; Lavi, S; Kafri, O

    1983-07-01

    A method based on moiré deflectometry for direct determination of the number of transverse modes of radiation of a light beam is presented. An expression for the number of transverse modes of a light beam, as a function of the beam divergence, is derived. We demonstrate the method for a Cu-vapor laser-beam analysis. PMID:19718131

  1. Direct Estimation of Fine and Coarse Mode Particle Parameters from Multiwavelength Lidar Measurements

    NASA Astrophysics Data System (ADS)

    Kolgotin, Alexei; Korenskiy, Mikhail; Veselovskii, Igor; Whiteman, David N.

    2016-06-01

    An approach for the direct estimation (DE) of particle parameters in the fine and coarse mode from multiwavelength lidar measurements is presented. Particle size distributions in both modes are approximated by rectangular functions, so the particle density is estimated directly without solving the inverse problem. The numerical simulation demonstrates that the particle volume in both modes can be estimated from 3β+2α lidar measurements with uncertainty of ~25% for a wide range of size distributions. The technique developed was applied to the observations of NASA GSFC Raman lidar. Comparison of the results obtained with DE and regularization approach applied to the same set of data demonstrates agreement between these two techniques.

  2. Direct dark modes excitation in bi-layered enantiomeric atoms-based metasurface through symmetry matching.

    PubMed

    Bochkova, Elena; Burokur, Shah Nawaz; de Lustrac, André; Lupu, Anatole

    2016-01-15

    We provide evidence for the mechanism of direct dark mode excitation in a metasurface composed of bi-layered Z-shaped enantiomeric meta-atoms. The electromagnetic behavior of the structure is investigated through both numerical simulations and experimental measurements in the microwave domain. We demonstrate direct field coupling excitation of second higher order electric mode under normal incidence based only on symmetry matching conditions. The proposed approach provides a better flexibility in engineering dark mode resonances that do not rely on hybridization mechanism and presents important advantages for multi-spectral sensor applications. PMID:26766727

  3. A multi-mode operation control strategy for flexible microgrid based on sliding-mode direct voltage and hierarchical controls.

    PubMed

    Zhang, Qinjin; Liu, Yancheng; Zhao, Youtao; Wang, Ning

    2016-03-01

    Multi-mode operation and transient stability are two problems that significantly affect flexible microgrid (MG). This paper proposes a multi-mode operation control strategy for flexible MG based on a three-layer hierarchical structure. The proposed structure is composed of autonomous, cooperative, and scheduling controllers. Autonomous controller is utilized to control the performance of the single micro-source inverter. An adaptive sliding-mode direct voltage loop and an improved droop power loop based on virtual negative impedance are presented respectively to enhance the system disturbance-rejection performance and the power sharing accuracy. Cooperative controller, which is composed of secondary voltage/frequency control and phase synchronization control, is designed to eliminate the voltage/frequency deviations produced by the autonomous controller and prepare for grid connection. Scheduling controller manages the power flow between the MG and the grid. The MG with the improved hierarchical control scheme can achieve seamless transitions from islanded to grid-connected mode and have a good transient performance. In addition the presented work can also optimize the power quality issues and improve the load power sharing accuracy between parallel VSIs. Finally, the transient performance and effectiveness of the proposed control scheme are evaluated by theoretical analysis and simulation results. PMID:26686458

  4. METHYLATED TRIVALENT ARSENIC SPECIES ARE GENOTOXIC

    EPA Science Inventory

    ABSTRACT

    The genotoxic effects of arsenic compounds are generally believed to result from other than direct interacton with DNA. The reactivties of methyloxarsine (MAsIII) and iododimethylarsine (DMAsIII), two methylated trivalent arsenicals, toward supercoiled X174 RFI ...

  5. Tapered acoustical directional couplers for integrated acousto-optical mode converters with weighted coupling

    NASA Astrophysics Data System (ADS)

    Herrmann, Harald; Rust, Ulrich; Schafer, Klaus

    1995-03-01

    Weighted coupling for strong sidelobe suppression of integrated acoustooptical mode converters in LiNbO3 using acoustical directional couplers has been studied theoretically and experimentally. A parameter free model for the propagation of surface acoustic waves in guiding structures has been developed based on a step-like variation of the acoustic velocity. Comparisons of theoretical results with experimental ones for acoustic waveguides and directional coupler structures confirm the applicability of the model. A coupled mode description of the acousto-optical polarization conversion in converters with acoustical directional couplers has been developed and applied to several tapered acoustical directional couplers. The model reveals that the conversion characteristics are usually strongly asymmetric. If the directional coupler is appropriately designed, a sidelobe suppression of about 30 dB can be achieved. First experimental results with tapered directional couplers confirm within some limits the theoretical predictions.

  6. Genotoxicity of phthalates.

    PubMed

    Erkekoglu, Pınar; Kocer-Gumusel, Belma

    2014-12-01

    Many of the environmental, occupational and industrial chemicals are able to generate reactive oxygen species (ROS) and cause oxidative stress. ROS may lead to genotoxicity, which is suggested to contribute to the pathophysiology of many human diseases, including inflammatory diseases and cancer. Phthalates are ubiquitous environmental chemicals and are well-known peroxisome proliferators (PPs) and endocrine disruptors. Several in vivo and in vitro studies have been conducted concerning the carcinogenic and mutagenic effects of phthalates. Di(2-ethylhexyl)-phthalate (DEHP) and several other phthalates are shown to be hepatocarcinogenic in rodents. The underlying factor in the hepatocarcinogenesis is suggested to be their ability to generate ROS and cause genotoxicity. Several methods, including chromosomal aberration test, Ames test, micronucleus assay and hypoxanthine guanine phosphoribosyl transferase (HPRT) mutation test and Comet assay, have been used to determine genotoxic properties of phthalates. Comet assay has been an important tool in the measurement of the genotoxic potential of many chemicals, including phthalates. In this review, we will mainly focus on the studies, which were conducted on the DNA damage caused by different phthalate esters and protection studies against the genotoxicity of these chemicals. PMID:25174766

  7. A relativistic backward wave oscillator for directly generating circularly polarized TE11 mode

    NASA Astrophysics Data System (ADS)

    Xiao, Renzhen; Zhang, Zhiqiang; Liang, Tiezhu; Deng, Yuqun; Li, Jiawei; Zhang, Qingyuan

    2016-03-01

    A relativistic backward wave oscillator for directly generating circularly polarized TE11 mode is proposed. In the device, the electrodynamics structures are divided into two groups in azimuth, each group consisting of two opposite 90 ° sectors, to produce two orthogonal TE11 modes. The axial position of the two groups is shifted to each other with a quarter of slow wave structure period to achieve a 90 ° phase difference between the two orthogonal TE11 modes. In particle-in-cell simulation, a circularly polarized TE11 mode with 1.5 GW power has been demonstrated. The amplitude ratio between the two orthogonal TE11 modes is smaller than 0.5 dB, and the phase difference is close to 90 ° .

  8. Sliding mode pulse-width modulation technique for direct torque controlled induction motor drive

    NASA Astrophysics Data System (ADS)

    Bounadja, M.; Belarbi, A. W.; Belmadani, B.

    2010-05-01

    This paper presents a novel pulse-width modulation technique based sliding mode approach for direct torque control of an induction machine drive. Methodology begins with a sliding mode control of machine's torque and stator flux to generate the reference voltage vector and to reduce parameters sensitivity. Then, the switching control of the three-phase inverter is developed using sliding mode concept to make the system tracking reference voltage inputs. The main features of the proposed methodologies are the high tracking accuracy and the much easier implementation compared to the space vector modulation. Simulations are carried out to confirm the effectiveness of proposed control algorithms.

  9. Direct diode-pumped Kerr-lens mode-locked Ti:sapphire laser.

    PubMed

    Durfee, Charles G; Storz, Tristan; Garlick, Jonathan; Hill, Steven; Squier, Jeff A; Kirchner, Matthew; Taft, Greg; Shea, Kevin; Kapteyn, Henry; Murnane, Margaret; Backus, Sterling

    2012-06-18

    We describe a Ti:sapphire laser pumped directly with a pair of 1.2 W 445 nm laser diodes. With over 30 mW average power at 800 nm and a measured pulsewidth of 15 fs, Kerr-lens-modelocked pulses are available with dramatically decreased pump cost. We propose a simple model to explain the observed highly stable Kerr-lens modelocking in spite of the fact that both the mode-locked and continuous-wave modes are smaller than the pump mode in the crystal. PMID:22714433

  10. Direct diode-pumped Kerr-lens mode-locked Ti:sapphire laser

    PubMed Central

    Durfee, Charles G.; Storz, Tristan; Garlick, Jonathan; Hill, Steven; Squier, Jeff A.; Kirchner, Matthew; Taft, Greg; Shea, Kevin; Kapteyn, Henry; Murnane, Margaret; Backus, Sterling

    2012-01-01

    We describe a Ti:sapphire laser pumped directly with a pair of 1.2W 445nm laser diodes. With over 30mW average power at 800 nm and a measured pulsewidth of 15fs, Kerr-lens-modelocked pulses are available with dramatically decreased pump cost. We propose a simple model to explain the observed highly stable Kerr-lens modelocking in spite of the fact that both the mode-locked and continuous-wave modes are smaller than the pump mode in the crystal. PMID:22714433

  11. The Direction Cosine Method of Scatterer Location Extended to Spotlight-Mode IFSAR

    SciTech Connect

    EICHEL,PAUL H.

    2000-10-26

    In this paper we have shown how the direction cosine method of stripmap-mode IFSAR maybe modified for use in the spotlight-mode case. Spotlight-mode IFSAR geometry dictates a common aperture phase center, velocity vector, and baseline vector for every pixel in an image. Angle with respect to the velocity vector is the same for every pixel in a given column and can be computed from the column index, the Doppler of the motion compensation point and the Doppler column sample spacing used in image formation. With these modifications, the direction cosines and length of the line of sight vector to every scatterer in the scene may be computed directly from the raw radar measurements of range, Doppler, and interferometric phase.

  12. Direct picosecond time resolution of unimolecular reactions initiated by local mode excitation

    NASA Technical Reports Server (NTRS)

    Scherer, N. F.; Doany, F. E.; Zewail, A. H.; Perry, J. W.

    1986-01-01

    Attention is given to the first results of direct, picosec measurements of the Delta-nu(OH) 5 local mode transition of H2O2. These time-resolved studies yield a direct measure of the unimolecular dissociation rate, and furnish a lower limit for the rate of energy redistribution from the OH stretch to the O-O reaction coordinate. The data thus determined may be used to ascertain the domain of validity for statistical unimolecular reaction rate theories.

  13. A fuzzy logic sliding mode controlled electronic differential for a direct wheel drive EV

    NASA Astrophysics Data System (ADS)

    Ozkop, Emre; Altas, Ismail H.; Okumus, H. Ibrahim; Sharaf, Adel M.

    2015-11-01

    In this study, a direct wheel drive electric vehicle based on an electronic differential system with a fuzzy logic sliding mode controller (FLSMC) is studied. The conventional sliding surface is modified using a fuzzy rule base to obtain fuzzy dynamic sliding surfaces by changing its slopes using the global error and its derivative in a fuzzy logic inference system. The controller is compared with proportional-integral-derivative (PID) and sliding mode controllers (SMCs), which are usually preferred to be used in industry. The proposed controller provides robustness and flexibility to direct wheel drive electric vehicles. The fuzzy logic sliding mode controller, electronic differential system and the overall electrical vehicle mechanism are modelled and digitally simulated by using the Matlab software. Simulation results show that the system with FLSMC has better efficiency and performance compared to those of PID and SMCs.

  14. Direct excitation of TE11 mode in a relativistic backward wave oscillator

    NASA Astrophysics Data System (ADS)

    Xiao, Renzhen; Zhang, Yuchuan; Li, Jiawei; Song, Zhimin; Sun, Jun

    2016-02-01

    A relativistic backward wave oscillator for directly generating TE11 mode is proposed. An axially asymmetric slow wave structure and a sectioned annular cathode are introduced to suppress the TM01 mode and excite the TE11 mode. A pre-modulation dual-cavity, which allows part of the backward power to propagate into the diode region, is adopted to optimize the electron beam bunch, indicating that the conventional design principle that the diode region and the beam-wave interaction region should be isolated can be broken to increase the interaction efficiency. Particle-in-cell simulations show that when the diode voltage is 780 kV, and beam current is 6.1 kA, a microwave with power of 2.0 GW, and frequency of 9.25 GHz can be obtained, corresponding to an efficiency of 42%. Furthermore, the main output mode is TE11 mode, and the power of the cross-polarized mode is less than 10% within the calculation time of 50 ns.

  15. Laser direct writing of complex radially varying single-mode polymer waveguide structures

    NASA Astrophysics Data System (ADS)

    Kruse, Kevin; Peng, Jie; Middlebrook, Christopher T.

    2015-07-01

    Increasing board-to-board and chip-to-chip computational data rates beyond 12.5 Gbs will require the use of single-mode polymer waveguides (WGs) that have high bandwidths and are able to be wavelength division multiplexed. Laser direct writing (LDW) of polymer WGs provides a scalable and reconfigurable maskless procedure compared to common photolithography fabrication. LDW of straights and radial curves are readily achieved using predefined drive commands of the two-axis direct drive linear stage system. Using the laser direct write process for advanced WG structures requires stage-drive programming techniques that account for specified polymer material exposure durations. Creating advanced structures such as WG S-bends into single-mode polymer WG builds provides designers with the ability to affect pitch control, optical coupling, and reduce footprint requirements. Fabrication of single-mode polymer WG segmented radial arcs is achieved through a smooth radial arc user-programmed defined mathematical algorithm. Cosine and raised-sine S-bends are realized through a segmentation method where the optimal incremental step length and bend dimensions are controlled to achieve minimal structure loss. Laser direct written S-bends are compared with previously published photolithographic S-bend results using theoretical bend loss models. Fabrication results show that LDW is a viable method in the fabrication of advanced polymer WG structures.

  16. Direct observation of collective modes coupled to molecular orbital-driven charge transfer

    NASA Astrophysics Data System (ADS)

    Ishikawa, Tadahiko; Hayes, Stuart A.; Keskin, Sercan; Corthey, Gastón; Hada, Masaki; Pichugin, Kostyantyn; Marx, Alexander; Hirscht, Julian; Shionuma, Kenta; Onda, Ken; Okimoto, Yoichi; Koshihara, Shin-ya; Yamamoto, Takashi; Cui, Hengbo; Nomura, Mitsushiro; Oshima, Yugo; Abdel-Jawad, Majed; Kato, Reizo; Miller, R. J. Dwayne

    2015-12-01

    Correlated electron systems can undergo ultrafast photoinduced phase transitions involving concerted transformations of electronic and lattice structure. Understanding these phenomena requires identifying the key structural modes that couple to the electronic states. We report the ultrafast photoresponse of the molecular crystal Me4P[Pt(dmit)2]2, which exhibits a photoinduced charge transfer similar to transitions between thermally accessible states, and demonstrate how femtosecond electron diffraction can be applied to directly observe the associated molecular motions. Even for such a complex system, the key large-amplitude modes can be identified by eye and involve a dimer expansion and a librational mode. The dynamics are consistent with the time-resolved optical study, revealing how the electronic, molecular, and lattice structures together facilitate ultrafast switching of the state.

  17. Direct imaging of radio-frequency modes via traveling wave magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Tonyushkin, A.; Deelchand, D. K.; Van de Moortele, P.-F.; Adriany, G.; Kiruluta, A.

    2016-01-01

    We demonstrate an experimental method for direct 2D and 3D imaging of magnetic radio-frequency (rf) field distribution in metal-dielectric structures based on traveling wave (TW) magnetic resonance imaging (MRI) at ultra-high field (>7 T). The typical apparatus would include an ultra-high field whole body or small bore MRI scanner, waveguide elements filled with MRI active dielectrics with predefined electric and magnetic properties, and TW rf transmit-receive probes. We validated the technique by obtaining TW MR images of the magnetic field distribution of the rf modes of circular waveguide filled with deionized water in a 16.4 T small-bore MRI scanner and compared the MR images with numerical simulations. Our MRI technique opens up a practical non-perturbed way of imaging of previously inaccessible rf field distribution of modes inside various shapes metal waveguides with inserted dielectric objects, including waveguide mode converters and transformers.

  18. Genotoxicity of monosodium glutamate.

    PubMed

    Ataseven, Nazmiye; Yüzbaşıoğlu, Deniz; Keskin, Ayten Çelebi; Ünal, Fatma

    2016-05-01

    Monosodium glutamate (MSG) is one of the most widely used flavor enhancers throughout the world. The aim of this study is to investigate the genotoxic potential of MSG by using chromosome aberrations (CAs), sister-chromatid exchanges (SCEs), cytokinesis-blocked micronucleus (CBMN), and random amplified polymorphic DNA-polimerase chain reaction (RAPD-PCR) in cultured human lymphocytes and alkaline comet assays in isolated human lymphocytes, which were incubated with six concentrations (250, 500, 1000, 2000, 4000 and 8000 μg/mL) of MSG. The result of this study indicated that MSG significantly and dose dependently increased the frequencies of CAs, SCE and MN in all treatments and times, compared with control. However, the replication (RI) and nuclear division indices (NDI) were not affected. In this paper, in vitro genotoxic effects of the MSG was also investigated on human peripheral lymphocytes by analysing the RAPD-PCR with arbitrary 10-mer primers. The changes occurring in RAPD profiles after MSG treatment include increase or decrease in band intensity and gain or loss of bands. In the comet assay, this additive caused DNA damage at all concentrations in isolated human lymphocytes after 1-h in vitro exposure. Our results demonstrate that MSG is genotoxic to the human peripheral blood lymphocytes in vitro. PMID:26929995

  19. Branching fractions and direct CP asymmetries of charmless decay modes at the Tevatron

    SciTech Connect

    Morello, Michael; /Pisa, Scuola Normale Superiore /INFN, Pisa

    2006-12-01

    The authors present new CDF results on the branching fractions and time-integrated direct CP asymmetries for B{sup 0} and B{sub s}{sup 0} decay modes into pairs of charmless charged hadrons (pion or kaon). The data set for this update amounts to 1 fb{sup -1} of {bar p}p collisions at {radical}s = 1.96 TeV. They report the first observation of the B{sub s}{sup 0} {yields} K{sup -}{pi}{sup +} mode and a measurement of its branching fraction and direct CP asymmetry. They also observe for the first time two charmless decays of b-baryon: {Lambda}{sub b}{sup 0} {yields} p{pi}{sup -} and {Lambda}{sub b}{sup 0} {yields} pK{sup -}.

  20. Mode Locking of Spin Waves Excited by Direct Currents in Microwave Nano-oscillators

    NASA Astrophysics Data System (ADS)

    Rezende, S. M.; de Aguiar, F. M.; Rodríguez-Suárez, R. L.; Azevedo, A.

    2007-02-01

    A spin-wave theory is presented which explains the frequency pulling and mode locking observed when two closely spaced spin-transfer nanometer-scale oscillators with slightly different frequencies are separately driven in the same magnetic thin film by spin-polarized carriers at high direct-current densities. The theory confirms recent experimental evidence that the origin of the phenomena lies in the nonlinear interaction between two overlapping spin waves excited in the magnetic nanostructure.

  1. Local mode excitation and direct unimolecular reaction rate measurements in tetramethyldioxetane

    SciTech Connect

    Cannon, B.D.; Crim, F.F.

    1981-08-15

    Direct excitation of overtone vibrations combined with time-resolved detection of product chemiluminescence produces both overtone vibration excitation spectra and directly measured unimolecular decay rates of tetramethyldioxetane. The spectra show increasingly pure local mode character in higher vibrational levels and exhibit splittings which arise from nonequivalent sites occupied by methyl hydrogens. The temporal evolution of the signal reflects the unimolecular decomposition rate of the highly vibrationally excited molecule, and comparing the observed behavior to Rice--Ramsperger--Kassel--Marcus theory calculations shows that they adequately describe the decomposition if properly averaged over the thermal vibrational energy content of the molecule.

  2. Identification of specific mRNA signatures as fingerprints for carcinogenesis in mice induced by genotoxic and nongenotoxic hepatocarcinogens.

    PubMed

    Kossler, Nadine; Matheis, Katja A; Ostenfeldt, Nina; Bach Toft, Dorthe; Dhalluin, Stéphane; Deschl, Ulrich; Kalkuhl, Arno

    2015-02-01

    Long-term rodent carcinogenicity studies for evaluation of chemicals and pharmaceuticals concerning their carcinogenic potential to humans are currently receiving critical revision. Additional data from mechanistic studies can support cancer risk assessment by clarifying the underlying mode of action. In the course of the IMI MARCAR project, a European consortium of EFPIA partners and academics, which aims to identify biomarkers for nongenotoxic carcinogenesis, a toxicogenomic mouse liver database was generated. CD-1 mice were orally treated for 3 and 14 days with 3 known genotoxic hepatocarcinogens: C.I. Direct Black 38, Dimethylnitrosamine and 4,4'-Methylenedianiline; 3 nongenotoxic hepatocarcinogens: 1,4-Dichlorobenzene, Phenobarbital sodium and Piperonyl butoxide; 4 nonhepatocarcinogens: Cefuroxime sodium, Nifedipine, Prazosin hydrochloride and Propranolol hydrochloride; and 3 compounds that show ambiguous results in genotoxicity testing: Cyproterone acetate, Thioacetamide and Wy-14643. By liver mRNA expression analysis using individual animal data, we identified 64 specific biomarker candidates for genotoxic carcinogens and 69 for nongenotoxic carcinogens for male mice at day 15. The majority of genotoxic carcinogen biomarker candidates possess functions in DNA damage response (eg, apoptosis, cell cycle progression, DNA repair). Most of the identified nongenotoxic carcinogen biomarker candidates are involved in regulation of cell cycle progression and apoptosis. The derived biomarker lists were characterized with respect to their dependency on study duration and gender and were successfully used to characterize carcinogens with ambiguous genotoxicity test results, such as Wy-14643. The identified biomarker candidates improve the mechanistic understanding of drug-induced effects on the mouse liver that result in hepatocellular adenomas and/or carcinomas in 2-year mouse carcinogenicity studies. PMID:25410580

  3. Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode

    NASA Astrophysics Data System (ADS)

    Lo, An-Ya; Liu, Shang-Bin; Kuo, Cheng-Tzu

    2010-09-01

    To improve the understanding on CNT growth modes, the various processes, including thermal CVD, MP-CVD and ECR-CVD, have been used to deposit CNTs on nanoporous SBA-15 and Si wafer substrates with C2H2 and H2 as reaction gases. The experiments to vary process parameter of Δ T, defined as the vector quantities of temperature at catalyst top minus it at catalyst bottom, were carried out to demonstrate its effect on the CNT growth mode. The TEM and TGA analyses were used to characterize their growth modes and carbon yields of the processes. The results show that Δ T can be used to monitor the temperature gradient direction across the catalyst nanoparticle during the growth stage of CNTs. The results also indicate that the tip-growth CNTs, base-growth CNTs and onion-like carbon are generally fabricated under conditions of Δ T > 0, <0 and ~0, respectively. Our proposed growth mechanisms can be successfully adopted to explain why the base- and tip-growth CNTs are common in thermal CVD and plasma-enhanced CVD processes, respectively. Furthermore, our experiments have also successfully demonstrated the possibility to vary Δ T to obtain the desired growth mode of CNTs by thermal or plasma-enhanced CVD systems for different applications.

  4. Effect of Temperature Gradient Direction in the Catalyst Nanoparticle on CNTs Growth Mode

    PubMed Central

    2010-01-01

    To improve the understanding on CNT growth modes, the various processes, including thermal CVD, MP-CVD and ECR-CVD, have been used to deposit CNTs on nanoporous SBA-15 and Si wafer substrates with C2H2 and H2 as reaction gases. The experiments to vary process parameter of ΔT, defined as the vector quantities of temperature at catalyst top minus it at catalyst bottom, were carried out to demonstrate its effect on the CNT growth mode. The TEM and TGA analyses were used to characterize their growth modes and carbon yields of the processes. The results show that ΔT can be used to monitor the temperature gradient direction across the catalyst nanoparticle during the growth stage of CNTs. The results also indicate that the tip-growth CNTs, base-growth CNTs and onion-like carbon are generally fabricated under conditions of ΔT > 0, <0 and ~0, respectively. Our proposed growth mechanisms can be successfully adopted to explain why the base- and tip-growth CNTs are common in thermal CVD and plasma-enhanced CVD processes, respectively. Furthermore, our experiments have also successfully demonstrated the possibility to vary ΔT to obtain the desired growth mode of CNTs by thermal or plasma-enhanced CVD systems for different applications. PMID:20730080

  5. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode.

    PubMed

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-01-01

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, -85 dBm and -110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz(2/3). This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10(-3 )and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications. PMID:27297267

  6. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode

    PubMed Central

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-01-01

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, −85 dBm and −110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz2/3. This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10−3 and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications. PMID:27297267

  7. 60-GHz Millimeter-wave Over Fiber with Directly Modulated Dual-mode Laser Diode

    NASA Astrophysics Data System (ADS)

    Tsai, Cheng-Ting; Lin, Chi-Hsiang; Lin, Chun-Ting; Chi, Yu-Chieh; Lin, Gong-Ru

    2016-06-01

    A directly modulated dual-mode laser diode (DMLD) with third-order intermodulation distortion (IMD3) suppression is proposed for a 60-GHz millimeter-wave over fiber (MMWoF) architecture, enabling new fiber-wireless communication access to cover 4-km single-mode-fiber (SMF) and 3-m wireless 16-QAM OFDM transmissions. By dual-mode injection-locking, the throughput degradation of the DMLD is mitigated with saturation effect to reduce its threshold, IMD3 power and relative intensity noise to 7.7 mA, ‑85 dBm and ‑110.4 dBc/Hz, respectively, providing huge spurious-free dynamic range of 85.8 dB/Hz2/3. This operation suppresses the noise floor of the DMLD carried QPSK-OFDM spectrum by 5 dB. The optical receiving power is optimized to restrict the power fading effect for improving the bit error rate to 1.9 × 10‑3 and the receiving power penalty to 1.1 dB. Such DMLD based hybrid architecture for 60-GHz MMW fiber-wireless access can directly cover the current optical and wireless networks for next-generation indoor and short-reach mobile communications.

  8. Automatically determining the origin direction and propagation mode of high-frequency radar backscatter

    NASA Astrophysics Data System (ADS)

    Burrell, Angeline G.; Milan, Stephen E.; Perry, Gareth W.; Yeoman, Timothy K.; Lester, Mark

    2015-12-01

    Elevation angles of returned backscatter are calculated at Super Dual Auroral Radar Network radars using interferometric techniques. These elevation angles allow the altitude of the reflection point to be estimated, an essential piece of information for many ionospheric studies. The elevation angle calculation requires knowledge of the azimuthal return angle. This directional angle is usually assumed to lie along a narrow beam from the front of the radar, even though the signals are known to return from both in front of and behind the radar. If the wrong direction of return is assumed, large uncertainties will be introduced through the azimuthal return angle. This paper introduces a means of automatically determining the correct direction of arrival and the propagation mode of backscatter. The application of this method will improve the accuracy of backscatter elevation angle data and aid in the interpretation of both ionospheric and ground backscatter observations.

  9. Single-Mode Fiber-Optic Directional Couplers For Narrow Spectral Linewidth Analyser

    NASA Astrophysics Data System (ADS)

    Belovolov, , M. I.; Dianov, E. M.; Krjukov, A. P.; Pencheva, V. H.

    1988-02-01

    A new design of Y-type end-fused single-mode fiber directional couplers has been suggest ed, and its optimum parameters with which it is possible to obtain losses of 0,5-1 dB have been determined. Cross-talk attenuation between reverse channels exceeds 60 dB. It has been found by experiments that transmission coefficients of the developed couplers are stable at wavelength variations. Furthermore, Y-type directional couplers maintain polarization state of the propagating radiation. Simple Michelson interferometer based on Y-type fiber optic directional couplers with a new optical fringe visibility registration system for the narrow linewidth( ▵V) = 10 kHz - 1 MHz) analysis of the single-frequency lasers has been created.

  10. Genotoxicity of glycol ethers.

    PubMed Central

    McGregor, D B

    1984-01-01

    The genetic toxicology of glycol ethers is reviewed. Ethylene glycol monomethyl ether (EGME) and diglyme have been more extensively studied than other members of this series. Most results indicate a lack of genotoxic potential, but certain tests have yielded positive responses with certain compounds. Ethylene glycol monoethyl ether (EGEE) induced sister chromatid exchanges and chromosomal aberrations in cultured cells. Both EGME and diglyme induced mouse sperm head morphological changes, male rat weak dominant lethal mutations and marked, but reversible, loss of male rat fertility. PMID:6541999

  11. Direct Geolocation of TerraSAR-X Spotlight Mode Image and Error Correction

    NASA Astrophysics Data System (ADS)

    Zhou, Xiao; Zeng, Qiming; Jiao, Jian; Zhang, Jingfa; Gong, Lixia

    2013-01-01

    The research dealt with direct geolocation of spaceborne high-resolution SAR image. The TerraSAR-X spotlight mode image was chosen as the study object. The mathematical model of SAR geolocation is Range-Doppler (RD) model. Its resolving algorithms had been studied and the ASF algorithm was chosen because of its high accuracy. The focus of this research laid on the error sources and their correction method which could affect the geolocation accuracy, such as the orbit errors, azimuth timing errors and range timing errors. At last, the accuracy of this method was verified by the experiment results.

  12. Indirect mechanisms of genotoxicity.

    PubMed

    Kirsch-Volders, Micheline; Vanhauwaert, Annelies; Eichenlaub-Ritter, Ursula; Decordier, Ilse

    2003-04-11

    Indirect mechanisms of genotoxicity correspond to interactions of mutagens with non-DNA targets, and are expected to show threshold concentration-effect response curves. If these thresholds can be proven experimentally they may provide a third alternative for risk assessment, besides the No Effect Level/Safety Factor approach and the low dose linear extrapolation method. We contributed significantly to the in vitro assessment of thresholds in human lymphocytes exposed to the spindle inhibitors nocodazole and carbendazim showing dose dependency and existence of lower thresholds for induction of non-disjunction as compared to chromosome loss. Micronuclei correlated with p53-independent or p53-dependent apoptosis and elimination of aneuploid cells. Extrapolation from in vitro threshold values to the in vivo situation remains unsolved. Comparing the in vitro threshold values for griseofulvin in human and rat lymphocytes with in vivo NOAEL/LOAEL in bone marrow/gut/erythrocytes suggests that the in vitro human system is the most sensitive. The threshold for induction of non-disjunction in in vitro maturing, nocodazole-exposed mouse oocytes was in the same low range. Regulators (UK Committee on Mutagenicity, http://www.doh.gov.uk/com/com.htm) considered the importance of thresholds for indirect mechanisms of genotoxicity. Acceptance of a non-linear extrapolation for mutagens requires mechanistic studies identifying the mutagen/target interactions. Moreover appropriate risk evaluation will require additional studies on individual susceptibility for indirect mutagenic effects and on interactions of aneugens in complex mixtures. PMID:12676452

  13. Accuracy details in realistic CFD modeling of an industrial centrifugal pump in direct and reverse modes

    NASA Astrophysics Data System (ADS)

    Páscoa, J. C.; Silva, F. J.; Pinheiro, J. S.; Martins, D. J.

    2010-12-01

    Numerical computation of the flowfield inside a pump is herein used as a numerical laboratory, subject to the limitations of modeling assumptions and to experimental verification. A numerical computation of the flow inside a real industrial centrifugal pump is performed that includes a very sophisticated geometry. Conversely to other computations, in this test case no simplification of the geometry was introduced. Numerical computations are obtained using Spalart-Allmaras turbulence model. A detailed analysis of the turbulent flowstructure is performed for the design point and two off design conditions. Additional computations were performed in order to compare the numerical and experimental pump characteristics; these were obtained under normalized testing conditions. Further computations are presented for the pump working in reverse turbine mode (PAT). Detailed analyses of the flow allow a comparison of the internal flow losses when the pump is operating in direct and reverse mode. This is also useful to help in the selection of an adequate pump geometry that can work in both modes with best efficiency.

  14. Two modes of a plasma jet excited by a direct current voltage

    NASA Astrophysics Data System (ADS)

    Li, Xuechen; Zhang, Panpan; Bao, Wenting; Jia, Pengying; Chu, Jingdi

    2016-04-01

    A plasma jet excited by a direct current voltage is developed to generate a diffuse plasma plume by blowing atmospheric pressure argon. Results show that the plume discharge operates in a single-pulsed mode or a continuous one depending on the applied voltage. For the single-pulsed mode, the discharge frequency increases with increasing the applied voltage or the air concentration, while it keeps almost constant with increasing the argon flow rate. The discharge dynamics at the breakdown stage indicate that the light emission propagates along the gas flow at a velocity in the order of 104 m s-1. The spatially resolved emission intensity at the afterglow stage of the pulsed discharge manifests a stratification into dark and bright luminous regions along the gas flow. For the continuous mode, however, the emission intensity gradually decreases along the gas flow. It is found that the continuous discharge is in a Townsend discharge regime judged from both the positive slope of the voltage-current curve and the small current density on the cathode surface. Based on optical emission spectroscopy, excited electron temperature and gas temperature of the plasma plume are obtained by a Boltzmann plot and fitting the spectra of OH radicals, respectively.

  15. Laser direct micro-machining with top-hat-converted single mode lasers

    NASA Astrophysics Data System (ADS)

    Homburg, O.; Toennissen, F.; Mitra, T.; Lissotschenko, V.

    2008-02-01

    Laser direct micro-machining processes are used in a variety of industries like inkjet printing, semiconductor processing, solar technology, flat-panel display production and medicine. Various kinds of materials, e.g. ceramics, metals, isolators, oxides, organics and semiconductors are being structured. In most cases pulsed single mode solid state lasers with an inhomogeneous Gaussian beam profile are employed, like YAG lasers and their harmonics. However, the quality and functionality of the generated structures and micro-systems as well as the speed of the process can be improved by the utilization of homogeneous top hat profiles. The beam shaping principle of refractive Gaussian-to-top-hat converters is shown. Compact beam shaper modules based on this principle have been developed - supporting most direct laser micro-machining applications. The resulting process advantages are demonstrated by selected application results, namely the drilling of holes and patterning of trenches for different kinds of materials.

  16. Two-Sided Pyramid Wavefront Sensor in the Direct Phase Mode

    SciTech Connect

    Phillion, D; Baker, K

    2006-04-12

    The two-sided pyramid wavefront sensor has been extensively simulated in the direct phase mode using a wave optics code. The two-sided pyramid divides the focal plane so that each half of the core only interferes with the speckles in its half of the focal plane. A relayed image of the pupil plane is formed at the CCD camera for each half. Antipodal speckle pairs are separated so that a pure phase variation causes amplitude variations in the two images. The phase is reconstructed from the difference of the two amplitudes by transforming cosine waves into sine waves using the Hilbert transform. There are also other corrections which have to be applied in Fourier space. The two-sided pyramid wavefront sensor performs extremely well: After two or three iterations, the phase error varies purely in y. The two-sided pyramid pair enables the phase to be completely reconstructed. Its performance has been modeled closed loop with atmospheric turbulence and wind. Both photon noise and read noise were included. The three-sided and four-sided pyramid wavefront sensors have also been studied in direct phase mode. Neither performs nearly as well as does the two-sided pyramid wavefront sensor.

  17. A Mode Detection Method Using the Azimuthal Directivity of a Turbofan Model

    NASA Technical Reports Server (NTRS)

    Thomas, R. H.; Farassat, F.; Clark, L. R.; Gerhold, C. H.; Kelly, J. J.; Becker, L. E.

    1999-01-01

    The azimuthal, far field directivity of a scale fan model was measured in high resolution. The model is a 12 inch diameter rotor with 16 blades followed by 40 stator vanes. The tests were conducted at the nominal 100% speed corresponding to a tip speed of 905 ft/sec. Measurement of the radiated sound field, forward of the fan, was made in an anechoic chamber with an inflow control device and a baffle separating the aft and forward radiated interaction noise. The acoustic field was surveyed with a circular hoop array of 16 microphones which was moved to 14 axial stations. At each axial station the hoop was rotated in half-degree increments to take 736 points in the azimuthal angle. In addition to sound pressure level, the phase angle relative to a reference microphone was measured at each point. The sound pressure level is shown to vary in patterns by 10-15 dB especially for the fundamental tone but also for the first and second harmonic. A far field mode detection method has been developed and used with the data which determines the modes generated by the fan and which then interact to form the azimuthal directivity.

  18. The genotoxicity of selenium.

    PubMed

    Shamberger, R J

    1985-07-01

    Selenium at nutritional levels has been shown to have numerous anticarcinogenic or preventative effects against carcinogen-induced breast, colon, liver and skin cancer in animals. Many of these anticarcinogenic effects have been summarized. In addition, numerous mutagenic and antimutagenic effects of selenium compounds have been reported. Some of the selenium compounds frequently tested for mutagenicity are listed in Table 1. Because of the numerous reported anticarcinogenic and preventative effects of selenium, many individuals are supplementing their diets with amounts of selenium that are greater than the recommended daily requirement. Selenium is also used widely in industrial products such as selenium rectifiers, photoelectric batteries, alloys and paints. Because selenium at higher levels is known to be toxic, there should be a greater understanding about its genotoxic as well as its beneficial effect. The object of this review is to summarize experimental evidence both for the antimutagenic and the mutagenic effect of selenium. PMID:3923345

  19. An instrument for direct observations of seismic and normal-mode rotational oscillations of the Earth

    PubMed Central

    Cowsik, R.

    2007-01-01

    The rotations around the vertical axis associated with the normal mode oscillations of the Earth and those induced by the seismic and other disturbances have been very difficult to observe directly. Such observations will provide additional information for 3D modeling of the Earth and for understanding earthquakes and other underground explosions. In this paper, we describe the design of an instrument capable of measuring the rotational motions associated with the seismic oscillations of the Earth, including the lowest frequency normal mode at ν ≈ 3.7 × 10−4 Hz. The instrument consists of a torsion balance with a natural frequency of ν0 ≈ 1.6 × 10−4 Hz, which is observed by an autocollimating optical lever of high angular resolution and dynamic range. Thermal noise limits the sensitivity of the apparatus to amplitudes of ≈ 1.5 × 10−9 rad at the lowest frequency normal mode and the sensitivity improves as ν−3/2 with increasing frequency. Further improvements in sensitivity by about two orders of magnitude may be achieved by operating the balance at cryogenic temperatures. Alternatively, the instrument can be made more robust with a reduced sensitivity by increasing ν0 to ≈10−2 Hz. This instrument thus complements the ongoing effort by Igel and others to study rotational motions using ring laser gyroscopes and constitutes a positive response to the clarion call for developments in rotation seismology by Igel, Lee, and Todorovska [H. Igel, W.H.K. Lee and M.I. Todorovska, AGU Fall Meeting 2006, Rotational Seismology Sessions: S22A,S23B, Inauguration of the International Working Group on Rotational Seismology (IWGoRS)]. PMID:17438268

  20. Burst-mode-operated, sub-nanosecond fiber MOPA system incorporating direct seed-packet shaping.

    PubMed

    Chen, Tao; Liu, Hao; Kong, Wei; Shu, Rong

    2016-09-01

    We report a novel burst-mode-operated sub-nanosecond fiber Master Oscillator, Power Amplifier (MOPA) system incorporating direct seed-packet shaping without external modulators. A fast digital-to-analog converter with 1 Gsps sampling rate and 16 bit resolution was developed to control the pulse amplitudes and sequences of a distributed feedback semiconductor seed laser to realize packet-shaped burst mode operation. Optical pulses with durations as short as 700 ps and peak power as high as 1 W can be generated from the seed by applying proper reverse voltages after positive electrical pulses to the laser driver to cancel the residual charges at its gate electrode. The average power of the laser can be amplified to nearly 40 W with FWHM spectral linewidth of ~0.12 nm after three stages of polarization maintaining fiber amplifiers. Different packet shapes including ramp-off, Gaussian, square and double rectangle can be produced from the fiber MOPA by finely pre-shaping the seed pulse bursts. It is believed that such a laser has provided a cost-effective solution to the generation of pulse bursts with arbitrary packet shapes for different practical applications including material micromachining and nonlinear frequency conversion. PMID:27607699

  1. Non-destructive Patterning of Carbon Electrodes by Using the Direct Mode of Scanning Electrochemical Microscopy.

    PubMed

    Stratmann, Lutz; Clausmeyer, Jan; Schuhmann, Wolfgang

    2015-11-16

    Patterning of glassy carbon surfaces grafted with a layer of nitrophenyl moieties was achieved by using the direct mode of scanning electrochemical microscopy (SECM) to locally reduce the nitro groups to hydroxylamine and amino functionalities. SECM and atomic force microscopy (AFM) revealed that potentiostatic pulses applied to the working electrode lead to local destruction of the glassy carbon surface, most likely caused by etchants generated at the positioned SECM tip used as the counter electrode. By applying galvanostatic pulses, and thus, limiting the current during structuring, corrosion of the carbon surface was substantially suppressed. After galvanostatic patterning, unambiguous proof of the formation of the anticipated amino moieties was possible by modulation of the pH value during the feedback mode of SECM imaging. This patterning strategy is suitable for the further bio-modification of microstructured surfaces. Alkaline phosphatase, as a model enzyme, was locally bound to the modified areas, thus showing that the technique can be used for the development of protein microarrays. PMID:26316379

  2. Mode- and Direction-Dependent Mechanical Energy Dissipation in Single-Crystal Resonators due to Anharmonic Phonon-Phonon Scattering

    NASA Astrophysics Data System (ADS)

    Iyer, Srikanth S.; Candler, Robert N.

    2016-03-01

    In this work, we determine the intrinsic mechanical energy dissipation limit for single-crystal resonators due to anharmonic phonon-phonon scattering in the Akhiezer (Ω τ ≪1 ) regime. The energy loss is derived using perturbation theory and the linearized Boltzmann transport equation for phonons, and includes the direction- and polarization-dependent mode-Grüneisen parameters in order to capture the strain-induced anharmonicity among phonon branches. This expression reveals the fundamental differences among the internal friction limits for different types of bulk-mode elastic waves. For cubic crystals, 2D-extensional modes have increased dissipation compared to width-extensional modes because the biaxial deformation opposes the natural Poisson contraction of the solid. Additionally, we show that shear-mode vibrations, which preserve volume, have significantly reduced energy loss because dissipative phonon-phonon scattering is restricted to pure-shear phonon branches, indicating that Lamé- or wineglass-mode resonators will have the highest upper limit on mechanical efficiency. Finally, we employ key simplifications to evaluate the quality factor limits for common mode shapes in single-crystal silicon devices, explicitly including the correct effective elastic storage moduli for different vibration modes and crystal orientations. Our expression satisfies the pressing need for a reliable analytical model that can predict the phonon-phonon dissipation limits for modern resonant microelectromechanical systems, where precise manufacturing techniques and accurate finite-element methods can be used to select particular vibrational mode shapes and crystal orientations.

  3. Measurements of Nitrogen Dioxide Total Column Amounts using a Brewer Double Spectrophotometer in Direct Sun Mode

    NASA Technical Reports Server (NTRS)

    Cede, Alexander; Herman, Jay; Richter, Andreas; Krotkov, Nickolay; Burrows, John

    2006-01-01

    NO2 column amounts were measured for the past 2 years at Goddard Space Flight Center, Greenbelt, Maryland, using a Brewer spectrometer in direct Sun mode. A new bootstrap method to calibrate the instrument is introduced and described. This technique selects the cleanest days from the database to obtain the solar reference spectrum. The main advantage for direct Sun measurements is that the conversion uncertainty from slant column to vertical column is negligible compared to the standard scattered light observations where it is typically on the order of 100% (2sigma) at polluted sites. The total 2sigma errors of the direct Sun retrieved column amounts decrease with solar zenith angle and are estimated at 0.2 to 0.6 Dobson units (DU, 1 DU approx. equal to 2.7 10(exp 16) molecules cm(exp -2)), which is more accurate than scattered light measurements for high NO2 amounts. Measured NO2 column amounts, ranging from 0 to 3 DU with a mean of 0.7 DU, show a pronounced daily course and a strong variability from day to day. The NO2 concentration typically increases from sunrise to noon. In the afternoon it decreases in summer and stays constant in winter. As expected from the anthropogenic nature of its source, NO2 amounts on weekends are significantly reduced. The measurements were compared to satellite retrievals from Scanning Image Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). Satellite data give the same average NO2 column and show a seasonal cycle that is similar to the ground data in the afternoon. We show that NO2 must be considered when retrieving aerosol absorption properties, especially for situations with low aerosol optical depth.

  4. Current investigations into the genotoxicity of zinc oxide and silica nanoparticles in mammalian models in vitro and in vivo: carcinogenic/genotoxic potential, relevant mechanisms and biomarkers, artifacts, and limitations

    PubMed Central

    Kwon, Jee Young; Koedrith, Preeyaporn; Seo, Young Rok

    2014-01-01

    Engineered nanoparticles (NPs) are widely used in many sectors, such as food, medicine, military, and sport, but their unique characteristics may cause deleterious health effects. Close attention is being paid to metal NP genotoxicity; however, NP genotoxic/carcinogenic effects and the underlying mechanisms remain to be elucidated. In this review, we address some metal and metal oxide NPs of interest and current genotoxicity tests in vitro and in vivo. Metal NPs can cause DNA damage such as chromosomal aberrations, DNA strand breaks, oxidative DNA damage, and mutations. We also discuss several parameters that may affect genotoxic response, including physicochemical properties, widely used assays/end point tests, and experimental conditions. Although potential biomarkers of nanogenotoxicity or carcinogenicity are suggested, inconsistent findings in the literature render results inconclusive due to a variety of factors. Advantages and limitations related to different methods for investigating genotoxicity are described, and future directions and recommendations for better understanding genotoxic potential are addressed. PMID:25565845

  5. Updated recommended lists of genotoxic and non-genotoxic chemicals for assessment of the performance of new or improved genotoxicity tests.

    PubMed

    Kirkland, David; Kasper, Peter; Martus, Hans-Jörg; Müller, Lutz; van Benthem, Jan; Madia, Federica; Corvi, Raffaella

    2016-01-01

    In 2008 we published recommendations on chemicals that would be appropriate to evaluate the sensitivity and specificity of new/modified mammalian cell genotoxicity tests, in particular to avoid misleading positive results. In light of new data it is appropriate to update these lists of chemicals. An expert panel was convened and has revised the recommended chemicals to fit the following different sets of characteristics: • Group 1: chemicals that should be detected as positive in in vitro mammalian cell genotoxicity tests. Chemicals in this group are all in vivo genotoxins at one or more endpoints, either due to DNA-reactive or non DNA-reactive mechanisms. Many are known carcinogens with a mutagenic mode of action, but a sub-class of probable aneugens has been introduced. • Group 2: chemicals that should give negative results in in vitro mammalian cell genotoxicity tests. Chemicals in this group are usually negative in vivo and non-DNA-reactive. They are either non-carcinogenic or rodent carcinogens with a non-mutagenic mode of action. • Group 3: chemicals that should give negative results in in vitro mammalian cell genotoxicity tests, but have been reported to induce gene mutations in mouse lymphoma cells, chromosomal aberrations or micronuclei, often at high concentrations or at high levels of cytotoxicity. Chemicals in this group are generally negative in vivo and negative in the Ames test. They are either non-carcinogenic or rodent carcinogens with an accepted non-mutagenic mode of action. This group contains comments as to any conditions that can be identified under which misleading positive results are likely to occur. This paper, therefore, updates these three recommended lists of chemicals and describes how these should be used for any test evaluation program. PMID:26774663

  6. Genotoxicity of pyrrolizidine alkaloids.

    PubMed

    Chen, Tao; Mei, Nan; Fu, Peter P

    2010-04-01

    Pyrrolizidine alkaloids (PAs) are common constituents of many plant species around the world. PA-containing plants are probably the most common poisonous plants affecting livestock and wildlife. They can inflict harm to humans through contaminated food sources, herbal medicines and dietary supplements. Half of the identified PAs are genotoxic and many of them are tumorigenic. The mutagenicity of PAs has been extensively studied in different biological systems. Upon metabolic activation, PAs produce DNA adducts, DNA cross-linking, DNA breaks, sister chromatid exchange, micronuclei, chromosomal aberrations, gene mutations and chromosome mutations in vivo and in vitro. PAs induced mutations in the cII gene of rat liver and in the p53 and K-ras genes of mouse liver tumors. It has been suggested that all PAs produce a set of (+/-)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine-derived DNA adducts and similar types of gene mutations. The signature types of mutations are G : C --> T : A transversion and tandem base substitutions. Overall, PAs are mutagenic in vivo and in vitro and their mutagenicity appears to be responsible for the carcinogenesis of PAs. PMID:20112250

  7. Genotoxicity and anti-genotoxicity of some traditional medicinal herbs.

    PubMed

    Romero-Jiménez, Magdalena; Campos-Sánchez, Juan; Analla, Mohamed; Muñoz-Serrano, Andrés; Alonso-Moraga, Angeles

    2005-08-01

    Six herbal infusions used worldwide (Matricaria chamomilla, Tilia cordata, Mentha piperita, Mentha pulegium, Uncaria tomentosa and Valeriana officinalis) were assayed for anti-genotoxicity using the Somatic Mutation And Recombination Test (SMART) in Drosophila melanogaster. All these infusions are traditionally used for various medical purposes, including anti-inflammatory processes. Hydrogen peroxide was used as an oxidative genotoxicant to test the anti-genotoxic potency of the medicinal infusions. None of these infusions showed a significant genotoxicity, quite the reverse they were able to behave as desmutagens, detoxifying the mutagen hydrogen peroxide. The phenolic content of such herbal infusions is argued to be the possible scavenger of reactive oxygen radicals produced by the hydrogen peroxide. PMID:16005256

  8. Polarization-dependent continuous change in the propagation direction of Dirac-cone modes in photonic-crystal slabs

    NASA Astrophysics Data System (ADS)

    Sakoda, Kazuaki

    2014-07-01

    We show that the propagation direction of the Dirac-cone modes of photonic-crystal slabs can be continuously controlled by the polarization of the incident wave. This property is realized by their isotropic dispersion relation and anisotropic mixture of two dipolar wave functions. To clarify these features, we formulate a Green-function method to describe the excitation process of the Dirac-cone modes and analyze the coupling strength with the incident wave by group theory. This angular dependence of the intensity distribution of the excited wave can be used for experimentally detecting the Dirac cones and distinguishing their mode symmetry.

  9. Coupled-mode analysis of power-transfer characteristics in a three-waveguide nonlinear directional coupler

    NASA Astrophysics Data System (ADS)

    Yasumoto, K.; Mitsunaga, N.; Maeda, H.

    1996-03-01

    A planar three-waveguide nonlinear directional coupler (NLDC) is analyzed by the use of a coupled-mode approach based on the singular perturbation technique. The self-consistent first-order coupled-mode equations are derived in an analytically closed form, which demonstrates that the power transfer in three-waveguide NLDC is described by linear-coupling terms and nonlinear self-modulation terms. The optical switching characteristics predicted by the coupled-mode theory are discussed and shown to be in good agreement with those obtained from a numerical analysis with the finite-difference beam-propagation method.

  10. Genotoxicity of Endodontic Materials: A Critical Review.

    PubMed

    Mohammadi, Zahed; Shalavi, Sousan; Jafarzadeh, Hamid; Bhandi, Shilpa; Patil, Shankargouda

    2015-08-01

    Genotoxicity is an action on cell's genetic material which may affect its integrity. This includes certain types of radiations and also certain chemical compounds. Genotoxic materials are those with affinity to interact with DNA but render them potentially carcinogenic or mutagenic. This review will address the genotoxicity of endodontic irrigants, medicaments and sealers. PMID:26423507

  11. Direct Measurement of Optical Force Induced by Near-Field Plasmonic Cavity Using Dynamic Mode AFM

    PubMed Central

    Guan, Dongshi; Hang, Zhi Hong; Marcet, Zsolt; Liu, Hui; Kravchenko, I. I.; Chan, C. T.; Chan, H. B.; Tong, Penger

    2015-01-01

    Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength gold disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. The experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures. PMID:26586455

  12. Direct measurement of optical force induced by near-field plasmonic cavity using dynamic mode AFM

    SciTech Connect

    Guan, Dongshi; Hang, Zhi Hong; Marset, Zsolt; Liu, Hui; Kravchenko, Ivan I.; Chan, Ho Bun; Chan, C. T.; Tong, Penger

    2015-11-20

    Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength gold disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. Lastly, the experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures.

  13. Direct measurement of optical force induced by near-field plasmonic cavity using dynamic mode AFM

    DOE PAGESBeta

    Guan, Dongshi; Hang, Zhi Hong; Marset, Zsolt; Liu, Hui; Kravchenko, Ivan I.; Chan, Ho Bun; Chan, C. T.; Tong, Penger

    2015-11-20

    Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength goldmore » disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. Lastly, the experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures.« less

  14. Design and fabrication of tubular scaffolds via direct writing in a melt electrospinning mode.

    PubMed

    Brown, Toby D; Slotosch, Anna; Thibaudeau, Laure; Taubenberger, Anna; Loessner, Daniela; Vaquette, Cedryck; Dalton, Paul D; Hutmacher, Dietmar W

    2012-12-01

    Flexible tubular structures fabricated from solution electrospun fibers are finding increasing use in tissue engineering applications. However it is difficult to control the deposition of fibers due to the chaotic nature of the solution electrospinning jet. By using non-conductive polymer melts instead of polymer solutions the path and collection of the fiber becomes predictable. In this work we demonstrate the melt electrospinning of polycaprolactone in a direct writing mode onto a rotating cylinder. This allows the design and fabrication of tubes using 20 μm diameter fibers with controllable micropatterns and mechanical properties. A key design parameter is the fiber winding angle, where it allows control over scaffold pore morphology (e.g. size, shape, number and porosity). Furthermore, the establishment of a finite element model as a predictive design tool is validated against mechanical testing results of melt electrospun tubes to show that a lesser winding angle provides improved mechanical response to uniaxial tension and compression. In addition, we show that melt electrospun tubes support the growth of three different cell types in vitro and are therefore promising scaffolds for tissue engineering applications. PMID:22589056

  15. Direct Measurement of Optical Force Induced by Near-Field Plasmonic Cavity Using Dynamic Mode AFM

    NASA Astrophysics Data System (ADS)

    Guan, Dongshi; Hang, Zhi Hong; Marcet, Zsolt; Liu, Hui; Kravchenko, I. I.; Chan, C. T.; Chan, H. B.; Tong, Penger

    2015-11-01

    Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength gold disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. The experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures.

  16. Fractional fuzzy adaptive sliding-mode control of a 2-DOF direct-drive robot arm.

    PubMed

    Efe, Mehmet Onder

    2008-12-01

    This paper presents a novel parameter adjustment scheme to improve the robustness of fuzzy sliding-mode control achieved by the use of an adaptive neuro-fuzzy inference system (ANFIS) architecture. The proposed scheme utilizes fractional-order integration in the parameter tuning stage. The controller parameters are tuned such that the system under control is driven toward the sliding regime in the traditional sense. After a comparison with the classical integer-order counterpart, it is seen that the control system with the proposed adaptation scheme displays better tracking performance, and a very high degree of robustness and insensitivity to disturbances are observed. The claims are justified through some simulations utilizing the dynamic model of a 2-DOF direct-drive robot arm. Overall, the contribution of this paper is to demonstrate that the response of the system under control is significantly better for the fractional-order integration exploited in the parameter adaptation stage than that for the classical integer-order integration. PMID:19022726

  17. Direct Measurement of Optical Force Induced by Near-Field Plasmonic Cavity Using Dynamic Mode AFM.

    PubMed

    Guan, Dongshi; Hang, Zhi Hong; Marcet, Zsolt; Liu, Hui; Kravchenko, I I; Chan, C T; Chan, H B; Tong, Penger

    2015-01-01

    Plasmonic nanostructures have attracted much attention in recent years because of their potential applications in optical manipulation through near-field enhancement. Continuing experimental efforts have been made to develop accurate techniques to directly measure the near-field optical force induced by the plasmonic nanostructures in the visible frequency range. In this work, we report a new application of dynamic mode atomic force microscopy (DM-AFM) in the measurement of the enhanced optical force acting on a nano-structured plasmonic resonant cavity. The plasmonic cavity is made of an upper gold-coated glass sphere and a lower quartz substrate patterned with an array of subwavelength gold disks. In the near-field when the sphere is positioned close to the disk array, plasmonic resonance is excited in the cavity and the induced force by a 1550 nm infrared laser is found to be increased by an order of magnitude compared with the photon pressure generated by the same laser light. The experiment demonstrates that DM-AFM is a powerful tool for the study of light induced forces and their enhancement in plasmonic nanostructures. PMID:26586455

  18. Efficient forward and adjoint calculations of normal mode spectra in laterally heterogeneous earth models using an iterative direct solution method

    NASA Astrophysics Data System (ADS)

    Al-Attar, D.; Woodhouse, J. H.

    2011-12-01

    Normal mode spectra provide a valuable data set for global seismic tomography, and, notably, are amongst the few geophysical observables that are sensitive to lateral variations in density structure within the Earth. Nonetheless, the effects of lateral density variations on mode spectra are rather subtle. In order, therefore, to reliably determine density variations with in the earth, it is necessary to make use of sufficiently accurate methods for calculating synthetic mode spectra. In particular, recent work has highlighted the need to perform 'full-coupling calculations' that take into account the interaction of large numbers of spherical earth multiplets. However, present methods for performing such full-coupling calculations require diagonalization of large coupling matrices, and so become computationally inefficient as the number of coupled modes is increased. In order to perform full-coupling calculations more efficiently, we describe a new implementation of the direct solution method for calculating synthetic spectra in laterally heterogeneous earth models. This approach is based on the solution of the inhomogeneous mode coupling equations in the frequency domain, and does not require the diagonalization of large matrices. Early implementations of the direct solution method used LU-decomposition to solve the mode coupling equations. However, as the number of coupled modes is increased, this method becomes impractically slow. To circumvent this problem, we solve the mode coupling equations iteratively using the preconditioned biconjugate gradient algorithm. We present a number of numerical tests to display the accuracy and efficiency of this method for performing large full-coupling calculations. In addition, we describe a frequency-domain formulation of the adjoint method for the calculation of Frechet kernels that show the sensitivity of normal mode observations to variations in earth structure. The calculation of such Frechet kernels involves one solution

  19. Genotoxicity of diuron and glyphosate in oyster spermatozoa and embryos.

    PubMed

    Akcha, F; Spagnol, C; Rouxel, J

    2012-01-15

    We investigated the effects of genotoxicant exposure in gametes and embryos to find a possible link between genotoxicity and reproduction/developmental impairment, and explore the impact of chemical genotoxicity on population dynamics. Our study focused on the genotoxic effects of two herbicides on oyster gametes and embryos: glyphosate (both as an active substance and in the Roundup formulation) and diuron. France is Europe's leading consumer of agrochemical substances and as such, contamination of France's coastal waters by pesticides is a major concern. Glyphosate and diuron are among the most frequently detected herbicides in oyster production areas; as oyster is a specie with external reproduction, its gametes and embryos are in direct contact with the surrounding waters and are hence particularly exposed to these potentially dangerous substances. In the course of this study, differences in genotoxic and embryotoxic responses were observed in the various experiments, possibly due to differences in pollutant sensitivity between the tested genitor lots. Glyphosate and Roundup had no effect on oyster development at the concentrations tested, whereas diuron significantly affected embryo-larval development from the lowest tested concentration of 0.05 μg L⁻¹, i.e. an environmentally realistic concentration. Diuron may therefore have a significant impact on oyster recruitment rates in the natural environment. Our spermiotoxicity study revealed none of the tested herbicides to be cytotoxic for oyster spermatozoa. However, the alkaline comet assay showed diuron to have a significant genotoxic effect on oyster spermatozoa at concentrations of 0.05 μg L⁻¹ upwards. Conversely, no effects due to diuron exposure were observed on sperm mitochondrial function or acrosomal membrane integrity. Although our initial results showed no negative effect on sperm function, the possible impact on fertilization rate and the consequences of the transmission of damaged DNA for

  20. Mode-specific tunneling splittings in 9-hydroxyphenalenone: Comparison of two methods for direct tunneling dynamics

    NASA Astrophysics Data System (ADS)

    Fernández-Ramos, Antonio; Smedarchina, Zorka; Zgierski, Marek Z.; Siebrand, Willem

    1998-07-01

    A benchmark comparison is presented of two direct dynamics methods for proton tunneling, namely variational transition-state theory with semiclassical tunneling corrections (VTST/ST) and the instanton method. The molecules chosen for the comparison are 9-hydroxyphenalenone-d0 and -d1, which have 64 vibrational degrees of freedom and show large tunneling splittings for the zero-point level and several vibrationally excited levels of the electronic ground state. Some of the excited-level splittings are larger and some smaller than the zero-level splitting, illustrating the multidimensional nature of the tunneling. Ab initio structure and force field calculations at the Hartree-Fock/6-31G** level are carried out for the two stationary points of the tunneling potential, viz. the equilibrium configuration and the transition state. The VTST/ST calculations are based on both the small- and the large-curvature approximation; the additional quantum-chemical calculations required at intermediate points of the potential are performed at the semiempirical modified neglect of differential overlap (MNDO)/H2 level. The VTST/ST computations use the MORATE 6.5 code developed by Truhlar and co-workers. The instanton dynamics calculations are based on the method we previously developed and applied to tropolone, among others. It uses the transition state rather than the equilibrium configuration as reference structure and approximates the least action analytically. The computations use our "dynamics of instanton tunneling" (DOIT) code. It is found that the large-curvature approximation and the instanton method both reproduce the observed zero-level splitting of the d0 isotopomer if the calculated barrier is reduced by a factor 0.87. With this adjusted barrier, the instanton method also reproduces the zero-level and excited-level splittings of the d1 isotopomer. However, both the small- and the large-curvature approximations severely underestimate all these splittings. These methods

  1. Direct Observation of Mode-Coupling Instability in Two-Dimensional Plasma Crystals

    SciTech Connect

    Coueedel, L.; Nosenko, V.; Ivlev, A. V.; Zhdanov, S. K.; Thomas, H. M.; Morfill, G. E.

    2010-05-14

    Dedicated experiments on melting of two-dimensional plasma crystals were carried out. The melting was always accompanied by spontaneous growth of the particle kinetic energy, suggesting a universal plasma-driven mechanism underlying the process. By measuring three principal dust-lattice wave modes simultaneously, it is unambiguously demonstrated that the melting occurs due to the resonance coupling between two of the dust-lattice modes. The variation of the wave modes with the experimental conditions, including the emergence of the resonant (hybrid) branch, reveals exceptionally good agreement with the theory of mode-coupling instability.

  2. Periodic Radiation Patterns and Circulating Direction of Lasing Light by Quasi Whispering Gallery Mode in Hexagonal GaN Microdisk

    NASA Astrophysics Data System (ADS)

    Kouno, Tetsuya; Suzuki, Sho; Sakai, Masaru; Kishino, Katsumi; Hara, Kazuhiko

    2016-05-01

    We have experimentally elucidated the periodic radiation patterns and circulating direction of the lasing light generated by the quasi-whispering-gallery mode (QWGM) in a hexagonal GaN microdisk. The radiated lasing light from the microdisk is highly directional, with the high intensities of the obtained radiated lasing light having a periodic spacing of 120° in the planar direction. The results show that the QWGM-generated lasing light circulates in a single direction in the microdisk, namely, either clockwise or counter-clockwise.

  3. Directional whispering gallery mode emission from Limaçon-shaped electrically pumped quantum dot micropillar lasers

    NASA Astrophysics Data System (ADS)

    Albert, F.; Hopfmann, C.; Eberspächer, A.; Arnold, F.; Emmerling, M.; Schneider, C.; Höfling, S.; Forchel, A.; Kamp, M.; Wiersig, J.; Reitzenstein, S.

    2012-07-01

    We experimentally demonstrate directional far field emission from whispering gallery modes (WGMs) in electrically driven quantum dot micropillar lasers. In-plane directionality of whispering gallery mode emission is obtained by patterning micropillars with Limaçon-shaped cross-section and an upper air-bridge contact for current injection. The micropillar lasers with radii R0 down to 4.5 μm show Q-factors of 40 000 and threshold currents of 40 μA at low temperature. We achieved a far field divergence of about 30° and a directionality of 1.67 ± 0.15 for an optimal Limaçon deformation factor ɛ ≈ 0.5. Parameter dependent studies of the directional emission as a function of ɛ reveal good qualitative agreement with theoretical predictions.

  4. Quantitative and Direct Near-Field Analysis of Plasmonic-Induced Transparency and the Observation of a Plasmonic Breathing Mode.

    PubMed

    Khunsin, Worawut; Dorfmüller, Jens; Esslinger, Moritz; Vogelgesang, Ralf; Rockstuhl, Carsten; Etrich, Christoph; Kern, Klaus

    2016-02-23

    We investigated experimentally and numerically in the optical near-field a plasmonic model system similar to a dolmen-type structure for phenomena such as plasmon-induced transparency. Through engineering of coupling strength, structure orientation, and incident angle and phase of the excitation source it was possible to control near-field excitation of the dark modes. We showed that quantitative analysis of near-field amplitude and excitation strength provided essential information that allowed identifying the interaction between the bright and the dark mode and how it causes the formation of plasmon-induced transparency features and a Fano resonance. In addition, we introduced a mechanism to excite field distributions in plasmonic structures that cannot be accessed directly using far-field illumination and demonstrated the excitation of a dark mode akin to a symmetry-forbidden plasmonic breathing mode using a linearly polarized far-field source. PMID:26789080

  5. Studies of H-Mode Plasmas Produced Directly by Pellet Injection in the DIII-D Tokamak

    SciTech Connect

    P. Gohil; L.R. Baylor; T.C. Jernigan; K.H. Burrell; T.N. Carlstrom; G.R. McKee; T.L. Rhodes

    2000-08-01

    A key issue for the physics of H-mode plasmas is to determine which plasma quantities are critical for the formation of the edge transport barrier. One approach is to directly perturb the edge plasma and observe the subsequent changes. In DIII-D, pellet injection has been used to directly change the edge plasma conditions and produce H-mode transitions. One hypothesis for the H-mode transition is that the attainment of a critical edge electron temperature is required for the transition [1-3]. This hypothesis is disproved in this paper. H-mode transitions were produced by injecting frozen deuterium pellets of diameter 2.7 mm from the inner wall of the DIII-D vessel into the high toroidal field side (HFS) and from the outer wall into the low field side (LFS) of the plasma. Both the HFS and LFS pellets produced significant increases in the edge electron density, which led to substantial reductions in the edge electron and ion temperatures. However, H-mode transitions were still produced with the lowered edge temperatures, implying that a critical edge temperature is not necessary for H-mode transitions. The pellet induced H-mode plasma exhibited clear pedestals in electron density and electron and ion temperatures at the plasma edge and persisted for the duration of the applied neutral beam power. The HFS pellet's penetration and deposition profiles were substantially deeper (up to {rho} {approx} 0.2) than that of the LFS pellet (up to {rho} {approx} 0.7). However, since both HFS and LFS pellets produced H-mode transitions, this implies that pellet penetration depth is not important the important factor is the large increase in the electron density right at the plasma edge produced by both types of pellets. The values of the edge plasma quantities at the H-mode transition were expressed in the parametric terms described in several theories and models of the H-mode transitions [4-6]. On comparison, the experimentally determined parameters at the H-mode transition were

  6. Saturable absorbers incorporating carbon nanotubes directly synthesized onto substrates and fibers and their application to mode-locked fiber lasers

    NASA Astrophysics Data System (ADS)

    Yamashita, S.; Inoue, Y.; Maruyama, S.; Murakami, Y.; Yaguchi, H.; Jablonski, M.; Set, S. Y.

    2004-07-01

    We present novel carbon-nanotube-based saturable absorbers. Using the low-temperature alcohol catalytic chemical-vapor deposition method, high-quality single-walled carbon nanotubes (SWNTs) were directly synthesized on quartz substrates and fiber ends. We successfully applied the SWNTs to mode lock a fiber laser producing subpicosecond pulses at a 50-MHz repetition rate.

  7. Residual-QSAR. Implications for genotoxic carcinogenesis

    PubMed Central

    2011-01-01

    Introduction Both main types of carcinogenesis, genotoxic and epigenetic, were examined in the context of non-congenericity and similarity, respectively, for the structure of ligand molecules, emphasizing the role of quantitative structure-activity relationship ((Q)SAR) studies in accordance with OECD (Organization for Economic and Cooperation Development) regulations. The main purpose of this report involves electrophilic theory and the need for meaningful physicochemical parameters to describe genotoxicity by a general mechanism. Residual-QSAR Method The double or looping multiple linear correlation was examined by comparing the direct and residual structural information against the observed activity. A self-consistent equation of observed-computed activity was assumed to give maximum correlation efficiency for those situations in which the direct correlations gave non-significant statistical information. Alternatively, it was also suited to describe slow and apparently non-noticeable cancer phenomenology, with special application to non-congeneric molecules involved in genotoxic carcinogenesis. Application and Discussions The QSAR principles were systematically applied to a given pool of molecules with genotoxic activity in rats to elucidate their carcinogenic mechanisms. Once defined, the endpoint associated with ligand-DNA interaction was used to select variables that retained the main Hansch physicochemical parameters of hydrophobicity, polarizability and stericity, computed by the custom PM3 semiempirical quantum method. The trial and test sets of working molecules were established by implementing the normal Gaussian principle of activities that applies when the applicability domain is not restrained to the congeneric compounds, as in the present study. The application of the residual, self-consistent QSAR method and the factor (or average) method yielded results characterized by extremely high and low correlations, respectively, with the latter resembling

  8. Genotoxicity of titanium dioxide nanoparticles.

    PubMed

    Chen, Tao; Yan, Jian; Li, Yan

    2014-03-01

    Titanium dioxide nanoparticles (TiO(2)-NPs, <100 nm) are increasingly being used in pharmaceuticals and cosmetics due to the unique properties derived from their small sizes. However, their large surface-area to mass ratio and high redox potential may negatively impact human health and the environment. TiO(2)-NPs can cause inflammation, pulmonary damage, fibrosis, and lung tumors and they are possibly carcinogenic to humans. Because cancer is a disease involving mutation, there are a large number of studies on the genotoxicity of TiO(2)-NPs. In this article, we review the results that have been reported in the literature, with a focus on data generated from the standard genotoxicity assays. The data include genotoxicity results from the Ames test, in vitro and in vivo Comet assay, in vitro and in vivo micronucleus assay, sister chromatid exchange assay, mammalian cell hypoxanthine-guanine phosphoribosyl transferase gene assay, the wing somatic mutation and recombination assay, and the mouse phosphatidylinositol glycan, class A gene assay. Inconsistent results have been found in these assays, with both positive and negative responses being reported. The in vitro systems for assessing the genotoxicity of TiO(2)-NPs have generated a greater number of positive results than the in vivo systems, and tests for DNA and chromosome damage have produced more positive results than the assays measuring gene mutation. Nearly all tests for measuring the mutagenicity of TiO(2)-NPs were negative. The current data indicate that the genotoxicity of TiO(2)-NPs is mediated mainly through the generation of oxidative stress in cells. PMID:24673907

  9. Direct observation of dynamic modes excited in a magnetic insulator by pure spin current

    PubMed Central

    Demidov, V. E.; Evelt, M.; Bessonov, V.; Demokritov, S. O.; Prieto, J. L.; Muñoz, M.; Ben Youssef, J.; Naletov, V. V.; de Loubens, G.; Klein, O.; Collet, M.; Bortolotti, P.; Cros, V.; Anane, A.

    2016-01-01

    Excitation of magnetization dynamics by pure spin currents has been recently recognized as an enabling mechanism for spintronics and magnonics, which allows implementation of spin-torque devices based on low-damping insulating magnetic materials. Here we report the first spatially-resolved study of the dynamic modes excited by pure spin current in nanometer-thick microscopic insulating Yttrium Iron Garnet disks. We show that these modes exhibit nonlinear self-broadening preventing the formation of the self-localized magnetic bullet, which plays a crucial role in the stabilization of the single-mode magnetization oscillations in all-metallic systems. This peculiarity associated with the efficient nonlinear mode coupling in low-damping materials can be among the main factors governing the interaction of pure spin currents with the dynamic magnetization in high-quality magnetic insulators. PMID:27608533

  10. Direct observation of dynamic modes excited in a magnetic insulator by pure spin current.

    PubMed

    Demidov, V E; Evelt, M; Bessonov, V; Demokritov, S O; Prieto, J L; Muñoz, M; Ben Youssef, J; Naletov, V V; de Loubens, G; Klein, O; Collet, M; Bortolotti, P; Cros, V; Anane, A

    2016-01-01

    Excitation of magnetization dynamics by pure spin currents has been recently recognized as an enabling mechanism for spintronics and magnonics, which allows implementation of spin-torque devices based on low-damping insulating magnetic materials. Here we report the first spatially-resolved study of the dynamic modes excited by pure spin current in nanometer-thick microscopic insulating Yttrium Iron Garnet disks. We show that these modes exhibit nonlinear self-broadening preventing the formation of the self-localized magnetic bullet, which plays a crucial role in the stabilization of the single-mode magnetization oscillations in all-metallic systems. This peculiarity associated with the efficient nonlinear mode coupling in low-damping materials can be among the main factors governing the interaction of pure spin currents with the dynamic magnetization in high-quality magnetic insulators. PMID:27608533

  11. A new asymmetric directional microphone algorithm with automatic mode-switching ability for binaural hearing support devices.

    PubMed

    Kim, Jinryoul; Nam, Kyoung Won; Yook, Sunhyun; Jang, Dong Pyo; Kim, In Young; Hong, Sung Hwa

    2015-06-01

    For hearing support devices, it is important to minimize the negative effect of ambient noises for speech recognition but also, at the same time, supply natural ambient sounds to the hearing-impaired person. However, conventional fixed bilateral asymmetric directional microphone (DM) algorithms cannot perform in such a way when the DM-mode device and a dominant noise (DN) source are placed on the same lateral hemisphere. In this study, a new binaural asymmetric DM algorithm that can overcome the defects of conventional algorithms is proposed. The proposed algorithm can estimate the position of a specific DN in the 90°-270° range and switch directional- and omnidirectional-mode devices automatically if the DM-mode device and the DN are placed in opposite lateral hemispheres. Computer simulation and KEMAR mannequin recording tests demonstrated that the performance of the conventional algorithm deteriorated when the DM-mode device and the DN were placed in the opposite hemisphere; in contrast, the performance of the proposed algorithm was consistently maintained regardless of directional variations in the DN. Based on these experimental results, the proposed algorithm may be able to improve speech quality and intelligibility for hearing-impaired persons who have similar degrees of hearing impairment in both ears. PMID:25597956

  12. Mechanism of genotoxicity induced by targeted cytoplasmic irradiation

    PubMed Central

    Hong, M; Xu, A; Zhou, H; Wu, L; Randers-Pehrson, G; Santella, R M; Yu, Z; Hei, T K

    2010-01-01

    Background: Direct damage to DNA is generally accepted as the main initiator of mutation and cancer induced by environmental carcinogens or ionising radiation. However, there is accumulating evidence suggesting that extracellular/extranuclear targets may also have a key role in mediating the genotoxic effects of ionising radiation. As the possibility of a particle traversal through the cytoplasm is much higher than through the nuclei in environmental radiation exposure, the contribution to genotoxic damage from cytoplasmic irradiation should not be ignored in radiation risk estimation. Although targeted cytoplasmic irradiation has been shown to induce mutations in mammalian cells, the precise mechanism(s) underlying the mutagenic process is largely unknown. Methods: A microbeam that can target the cytoplasm of cells with high precision was used to study mechanisms involved in mediating the genotoxic effects in irradiated human–hamster hybrid (AL) cells. Results: Targeted cytoplasmic irradiation induces oxidative DNA damages and reactive nitrogen species (RNS) in AL cells. Lipid peroxidation, as determined by the induction of 4-hydroxynonenal was enhanced in irradiated cells, which could be suppressed by butylated hydroxyl toluene treatment. Moreover, cytoplasmic irradiation of AL cells increased expression of cyclooxygenase-2 (COX-2) and activation of extracellular signal-related kinase (ERK) pathway. Conclusion: We herein proposed a possible signalling pathway involving reactive oxygen/nitrogen species and COX-2 in the cytoplasmic irradiation-induced genotoxicity effect. PMID:20842121

  13. Genotoxicity of complex mixtures: CHO cell mutagenicity assay

    SciTech Connect

    Frazier, M.E.; Samuel, J.E.

    1985-02-01

    A Chinese hamster ovary (CHO) mammalian cell assay was used to evaluate the genotoxicity of complex mixtures (synthetic fuels). The genotoxicity (mutagenic potency) of the mixtures increased as the temperature of their boiling range increased. Most of the genotoxicity in the 750/sup 0/F+ boiling-range materials was associated with the neutral polycyclic aromatic hydrocarbon (PAH) fractions. Chemical analysis data indicate that the PAH fractions of high-boiling coal liquids contain a number of known chemical carcinogens, including five- and six-ring polyaromatics (e.g., benzo(a)pyrene) as well as four- and five-ring alkyl-substituted PAH (e.g., methylchrysene and dimethylbenzanthracenes); concentrations are a function of boiling point (bp). In vitro genotoxicity was also detected in fractions of nitrogen-containing polyaromatic compounds, as well as in those with aliphatics of hydroxy-containing PAH. Mutagenic activity of some fractions was detectable in the CHO assay in the absence of an exogenous metabolic activation system; in some instances, addition of exogenous enzymes and cofactors inhibited expression of the direct-acting mutagenic potential of the fraction. These data indicate that the organic matrix of the chemical fraction determines whether, and to what degree, various mutagens are expressed in the CHO assay. Therefore, the results of biological assays of these mixtures must be correlated with chemical analyses for proper interpretation of these data. 29 references, 16 figures, 4 tables.

  14. Mutagenicity and genotoxicity of coal fly ash water leachate

    SciTech Connect

    Chakraborty, R.; Mukherjee, A.

    2009-03-15

    Fly ash is a by-product of coal-fired electricity generation plants. The prevalent practice of disposal is as slurry of ash and water to storage or ash ponds located near power stations. This has lain to waste thousands of hectares of land all over the world. Since leaching is often the cause of off-site contamination and pathway of introduction into the human environment, a study on the genotoxic effects of fly ash leachate is essential. Leachate prepared from the fly ash sample was analyzed for metal content, and tested for mutagenicity and genotoxicity. Analyses of metals show predominance of the metals - sodium, silicon, potassium, calcium, magnesium, iron, manganese, zinc, and sulphate. The Ames Salmonella mutagenicity assay, a short-term bacterial reverse mutation assay, was conducted on two-tester strains of Salmonella typhimurium strains TA97a and TA102. For genotoxicity, the alkaline version of comet assay on fly ash leachate was carried in vitro on human blood cells and in vivo on Nicotiana plants. The leachate was directly mutagenic and induced significantconcentration-dependent increases in DNA damage in whole blood cells, lymphocytes, and in Nicotiana plants. The comet parameters show increases in tail DNA percentage (%), tail length (mu m), and olive tail moment (arbitrary units). Our results indicate that leachate from fly ash dumpsites has the genotoxic potential and may lead to adverse effects on vegetation and on the health of exposed human populations.

  15. Rat Pig-a mutation assay responds to the genotoxic carcinogen ethyl carbamate but not the non-genotoxic carcinogen methyl carbamate

    PubMed Central

    Bemis, Jeffrey C.; Labash, Carson; Avlasevich, Svetlana L.; Carlson, Kristine; Berg, Ariel; Torous, Dorothea K.; Barragato, Matthew; MacGregor, James T.; Dertinger, Stephen D.

    2015-01-01

    Determination of the mode of action of carcinogenic agents is an important factor in risk assessment and regulatory practice. To assess the ability of the erythrocyte-based Pig-a mutation assay to discriminate between genotoxic and non-genotoxic modes of action, the mutagenic response of Sprague Dawley rats exposed to methyl carbamate (MC) or ethyl carbamate (EC) was investigated. EC, a potent carcinogen, is believed to induce DNA damage through the formation of a DNA-reactive epoxide group, whereas the closely structurally related compound, MC, cannot form this epoxide and its weaker carcinogenic activity is thought to be secondary to inflammation and promotion of cell proliferation. The frequency of Pig-a mutant phenotype cells was monitored before, during, and after 28 consecutive days of oral gavage exposure to either MC (doses ranging from 125 to 500mg/kg/day) or EC (250mg/kg/day). Significant increases in the frequency of mutant reticulocytes were observed from Days 15 through 43, with a peak mean frequency of 19.9×10−6 on Day 29 (i.e. 24.9-fold increase relative to mean vehicle control across all four sampling times). As expected, mutant erythrocyte responses lagged behind mutant reticulocyte responses, with a maximal mean frequency of 8.2×10−6 on Day 43 (i.e. 16.4-fold increase). No mutagenic effects were observed with MC. A second indicator of in vivo genotoxicity, peripheral blood micronucleated reticulocytes, was also studied. This endpoint was responsive to EC (3.3-fold mean increase), but not to MC. These results support the hypothesis that genotoxicity contributes to the carcinogenicity of EC but not of MC, and illustrates the value of the Pig-a assay for discriminating between genotoxic and non-genotoxic modes of action. PMID:25833916

  16. The modes of physician remuneration and their effect on direct patient contact.

    PubMed

    Basu, Kisalaya; Mandelzys, David

    2008-01-01

    Initiatives such as primary care reform have allocated millions of dollars towards the Canadian health care system. The way physicians are remunerated affects the supply of physician services and as such is essential to these initiatives to facilitate policy goals. However, there exists a gap in understanding how different modes of remuneration affect physician-patient contact. This paper examines if there is a significant difference between the average full-time-equivalent (FTE) of family physicians (FPs) remunerated through fee-for-service (FFS), salary, and blended arrangements. We used Nova Scotia physician billings dataset which tracks every services performed by both FFS and salaried physicians over the fiscal year 2003 to 2004. We estimated two semi-logarithmic models to examine the relationship between (1) modes of remuneration and FTE, and (2) modes of remuneration and total services, using ordinary least squares method. The National Physician Survey shows a significant difference between the current modes of remuneration and the preferred modes of remuneration; thus ruling out the possibility of selectivity bias. The results show that compared to the FFS FPs, the salaried FPs and blended FPs produce on average 40.46% and 23.13% less FTE respectively. It also indicates that compared to the FFS FPs, the salaried FPs and blended FPs deliver 53.54% and 31.49% fewer services on average. PMID:18447065

  17. Oscillation modes of direct current microdischarges with parallel-plate geometry

    SciTech Connect

    Stefanovic, Ilija; Kuschel, Thomas; Winter, Joerg; Skoro, Nikola; Maric, Dragana; Petrovic, Zoran Lj

    2011-10-15

    Two different oscillation modes in microdischarge with parallel-plate geometry have been observed: relaxation oscillations with frequency range between 1.23 and 2.1 kHz and free-running oscillations with 7 kHz frequency. The oscillation modes are induced by increasing power supply voltage or discharge current. For a given power supply voltage, there is a spontaneous transition from one to other oscillation mode and vice versa. Before the transition from relaxation to free-running oscillations, the spontaneous increase of oscillation frequency of relaxation oscillations form 1.3 kHz to 2.1 kHz is measured. Fourier transform spectra of relaxation oscillations reveal chaotic behavior of microdischarges. Volt-ampere (V-A) characteristics associated with relaxation oscillations describes periodical transition between low current, diffuse discharge, and normal glow. However, free-running oscillations appear in subnormal glow only.

  18. Parity time-symmetric vertical cavities: intrinsically single-mode regime in longitudinal direction.

    PubMed

    Jones, Hugh F; Kulishov, Mykola; Kress, Bernard

    2016-07-25

    We explore a new class of distributed feedback (DFB) structures that employ the recently-developed concept of parity-time (PT) symmetry in optics. We show that, based on PT-symmetric pure reflective volume gratings, a vertical surface-emitting cavity can be constructed. We provide a detailed analysis of the threshold conditions as well as the wavelength and angular spectral characteristics using the Kogelnik coupled-wave approximation, backed up by an exact solution of the Helmholtz equation. We show that such a PT-symmetric cavity can be configured to support one and only one longitudinal mode, leading to inherently single-mode lasing. PMID:27464163

  19. Direct X-B mode conversion for high-β national spherical torus experiment in nonlinear regime

    SciTech Connect

    Ali Asgarian, M. E-mail: maa@msu.edu; Parvazian, A.; Abbasi, M.; Verboncoeur, J. P.

    2014-09-15

    Electron Bernstein wave (EBW) can be effective for heating and driving currents in spherical tokamak plasmas. Power can be coupled to EBW via mode conversion of the extraordinary (X) mode wave. The most common and successful approach to study the conditions for optimized mode conversion to EBW was evaluated analytically and numerically using a cold plasma model and an approximate kinetic model. The major drawback in using radio frequency waves was the lack of continuous wave sources at very high frequencies (above the electron plasma frequency), which has been addressed. A future milestone is to approach high power regime, where the nonlinear effects become significant, exceeding the limits of validity for present linear theory. Therefore, one appropriate tool would be particle in cell (PIC) simulation. The PIC method retains most of the nonlinear physics without approximations. In this work, we study the direct X-B mode conversion process stages using PIC method for incident wave frequency f{sub 0} = 15 GHz, and maximum amplitude E{sub 0} = 10{sup 5 }V/m in the national spherical torus experiment (NSTX). The modelling shows a considerable reduction in X-B mode conversion efficiency, C{sub modelling} = 0.43, due to the presence of nonlinearities. Comparison of system properties to the linear state reveals predominant nonlinear effects; EBW wavelength and group velocity in comparison with linear regime exhibit an increment around ∼36% and 17%, respectively.

  20. Cell-Based Genotoxicity Testing

    NASA Astrophysics Data System (ADS)

    Reifferscheid, Georg; Buchinger, Sebastian

    Genotoxicity test systems that are based on bacteria display an important role in the detection and assessment of DNA damaging chemicals. They belong to the basic line of test systems due to their easy realization, rapidness, broad applicability, high sensitivity and good reproducibility. Since the development of the Salmonella microsomal mutagenicity assay by Ames and coworkers in the early 1970s, significant development in bacterial genotoxicity assays was achieved and is still a subject matter of research. The basic principle of the mutagenicity assay is a reversion of a growth inhibited bacterial strain, e.g., due to auxotrophy, back to a fast growing phenotype (regain of prototrophy). Deeper knowledge of the ­mutation events allows a mechanistic understanding of the induced DNA-damage by the utilization of base specific tester strains. Collections of such specific tester strains were extended by genetic engineering. Beside the reversion assays, test systems utilizing the bacterial SOS-response were invented. These methods are based on the fusion of various SOS-responsive promoters with a broad variety of reporter genes facilitating numerous methods of signal detection. A very important aspect of genotoxicity testing is the bioactivation of ­xenobiotics to DNA-damaging compounds. Most widely used is the extracellular metabolic activation by making use of rodent liver homogenates. Again, genetic engineering allows the construction of highly sophisticated bacterial tester strains with significantly enhanced sensitivity due to overexpression of enzymes that are involved in the metabolism of xenobiotics. This provides mechanistic insights into the toxification and detoxification pathways of xenobiotics and helps explaining the chemical nature of hazardous substances in unknown mixtures. In summary, beginning with "natural" tester strains the rational design of bacteria led to highly specific and sensitive tools for a rapid, reliable and cost effective ­genotoxicity

  1. Direct assignment of molecular vibrations via normal mode analysis of the neutron dynamic pair distribution function technique

    SciTech Connect

    Fry-Petit, A. M. E-mail: afry@fullerton.edu; Sheckelton, J. P.; McQueen, T. M. E-mail: afry@fullerton.edu; Rebola, A. F.; Fennie, C. J.; Mourigal, M.; Valentine, M.; Drichko, N.

    2015-09-28

    For over a century, vibrational spectroscopy has enhanced the study of materials. Yet, assignment of particular molecular motions to vibrational excitations has relied on indirect methods. Here, we demonstrate that applying group theoretical methods to the dynamic pair distribution function analysis of neutron scattering data provides direct access to the individual atomic displacements responsible for these excitations. Applied to the molecule-based frustrated magnet with a potential magnetic valence-bond state, LiZn{sub 2}Mo{sub 3}O{sub 8}, this approach allows direct assignment of the constrained rotational mode of Mo{sub 3}O{sub 13} clusters and internal modes of MoO{sub 6} polyhedra. We anticipate that coupling this well known data analysis technique with dynamic pair distribution function analysis will have broad application in connecting structural dynamics to physical properties in a wide range of molecular and solid state systems.

  2. Experimental and theoretical analysis of THz-frequency, direction-dependent, phonon polariton modes in a subwavelength, anisotropic slab waveguide.

    PubMed

    Yang, Chengliang; Wu, Qiang; Xu, Jingjun; Nelson, Keith A; Werley, Christopher A

    2010-12-01

    Femtosecond optical pulses were used to generate THz-frequency phonon polariton waves in a 50 micrometer lithium niobate slab, which acts as a subwavelength, anisotropic planar waveguide. The spatial and temporal electric field profiles of the THz waves were recorded for different propagation directions using a polarization gating imaging system, and experimental dispersion curves were determined via a two-dimensional Fourier transform. Dispersion relations for an anisotropic slab waveguide were derived via analytical analysis and found to be in excellent agreement with all observed experimental modes. From the dispersion relations, we analyze the propagation-direction-dependent behavior, effective refractive index values, and generation efficiencies for THz-frequency modes in the subwavelength, anisotropic slab waveguide. PMID:21164986

  3. Direct assignment of molecular vibrations via normal mode analysis of the neutron dynamic pair distribution function technique.

    PubMed

    Fry-Petit, A M; Rebola, A F; Mourigal, M; Valentine, M; Drichko, N; Sheckelton, J P; Fennie, C J; McQueen, T M

    2015-09-28

    For over a century, vibrational spectroscopy has enhanced the study of materials. Yet, assignment of particular molecular motions to vibrational excitations has relied on indirect methods. Here, we demonstrate that applying group theoretical methods to the dynamic pair distribution function analysis of neutron scattering data provides direct access to the individual atomic displacements responsible for these excitations. Applied to the molecule-based frustrated magnet with a potential magnetic valence-bond state, LiZn2Mo3O8, this approach allows direct assignment of the constrained rotational mode of Mo3O13 clusters and internal modes of MoO6 polyhedra. We anticipate that coupling this well known data analysis technique with dynamic pair distribution function analysis will have broad application in connecting structural dynamics to physical properties in a wide range of molecular and solid state systems. PMID:26429001

  4. Direct and Inverse Techniques of Guided-Mode Resonance Filters Designs

    NASA Technical Reports Server (NTRS)

    Tibuleac, Sorin; Magnusson, Robert; Maldonado, Theresa A.; Zuffada, Cinzia

    1997-01-01

    Guided-mode resonances arise in single or multilayer waveguides where one or more homogeneous layers are replaced by diffraction gratings (Fig. 1.) The diffractive element enables an electromagnetic wave incident on a waveguide grating to be coupled to the waveguide modes supportable by the structure in the absence of the modulation (i.e. the difference between the high and low dielectric constants of the grating) at specific values of the wavelength and incident angle. The periodic modulation of the guide makes the structure leaky, preventing sustained propagation of modes in the waveguide and coupling the waves out into the substrate and cover. As the wavelength is varied around resonance a rapid variation in the intensities of the external propagating waves occurs. By selecting a grating period small enough to eliminate the higher-order propagating waves, an increase in the zero-order intensities up to 100% can result. The pronounced frequency selectivity of guided-mode resonances in dielectric waveguide gratings can be applied to design high-efficiency reflection and transmission filters [1-3].

  5. The use of ex vivo human skin tissue for genotoxicity testing.

    PubMed

    Reus, Astrid A; Usta, Mustafa; Krul, Cyrille A M

    2012-06-01

    As a result of the chemical legislation concerning the registration, evaluation, authorization and restriction of chemicals (REACH), and the Seventh Amendment to the Cosmetics Directive, which prohibits animal testing in Europe for cosmetics, alternative methods for safety evaluation of chemicals are urgently needed. Current in vitro genotoxicity assays are not sufficiently predictive for the in vivo situation, resulting in an unacceptably high number of misleading positives. For many chemicals and ingredients of personal care products the skin is the first site of contact, but there are no in vitro genotoxicity assays available in the skin for additional evaluation of positive or equivocal responses observed in regulatory in vitro genotoxicity assays. In the present study ex vivo human skin tissue obtained from surgery was used for genotoxicity evaluation of chemicals by using the comet assay. Fresh ex vivo human skin tissue was cultured in an air-liquid interface and topically exposed to 20 chemicals, including true positive, misleading positive and true negative genotoxins. Based on the results obtained in the present study, the sensitivity, specificity and accuracy of the ex vivo skin comet assay to predict in vivo genotoxicity were 89%, 90% and 89%, respectively. Donor and experimental variability were mainly reflected in the magnitude of the response and not the difference between the presence and absence of a genotoxic response. The present study indicates that human skin obtained from surgery is a promising and robust model for safety evaluation of chemicals that are in direct contact with the skin. PMID:22507867

  6. The use of ex vivo human skin tissue for genotoxicity testing

    SciTech Connect

    Reus, Astrid A.; Usta, Mustafa; Krul, Cyrille A.M.

    2012-06-01

    As a result of the chemical legislation concerning the registration, evaluation, authorization and restriction of chemicals (REACH), and the Seventh Amendment to the Cosmetics Directive, which prohibits animal testing in Europe for cosmetics, alternative methods for safety evaluation of chemicals are urgently needed. Current in vitro genotoxicity assays are not sufficiently predictive for the in vivo situation, resulting in an unacceptably high number of misleading positives. For many chemicals and ingredients of personal care products the skin is the first site of contact, but there are no in vitro genotoxicity assays available in the skin for additional evaluation of positive or equivocal responses observed in regulatory in vitro genotoxicity assays. In the present study ex vivo human skin tissue obtained from surgery was used for genotoxicity evaluation of chemicals by using the comet assay. Fresh ex vivo human skin tissue was cultured in an air–liquid interface and topically exposed to 20 chemicals, including true positive, misleading positive and true negative genotoxins. Based on the results obtained in the present study, the sensitivity, specificity and accuracy of the ex vivo skin comet assay to predict in vivo genotoxicity were 89%, 90% and 89%, respectively. Donor and experimental variability were mainly reflected in the magnitude of the response and not the difference between the presence and absence of a genotoxic response. The present study indicates that human skin obtained from surgery is a promising and robust model for safety evaluation of chemicals that are in direct contact with the skin. -- Highlights: ► We use human skin obtained from surgery for genotoxicity evaluation of chemicals. ► We use the comet assay as parameter for genotoxicity in ex vivo human skin. ► Sensitivity, specificity and accuracy to predict in vivo genotoxins are determined. ► Sensitivity, specificity and accuracy are 89%, 90% and 90%, respectively. ► The method

  7. Influence of equilibrium shear flow in the parallel magnetic direction on edge localized mode crash

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Chen, S. Y.; Huang, J.; Xiong, Y. Y.; Tang, C. J.

    2016-04-01

    The influence of the parallel shear flow on the evolution of peeling-ballooning (P-B) modes is studied with the BOUT++ four-field code in this paper. The parallel shear flow has different effects in linear simulation and nonlinear simulation. In the linear simulations, the growth rate of edge localized mode (ELM) can be increased by Kelvin-Helmholtz term, which can be caused by the parallel shear flow. In the nonlinear simulations, the results accord with the linear simulations in the linear phase. However, the ELM size is reduced by the parallel shear flow in the beginning of the turbulence phase, which is recognized as the P-B filaments' structure. Then during the turbulence phase, the ELM size is decreased by the shear flow.

  8. The cadmium–mercaptoacetic acid complex contributes to the genotoxicity of mercaptoacetic acid-coated CdSe-core quantum dots

    PubMed Central

    Tang, Weikun; Fan, Junpeng; He, Yide; Huang, Bihai; Liu, Huihui; Pang, Daiwen; Xie, Zhixiong

    2012-01-01

    Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes. However, the genotoxicity potential of QDs still remains unclear. In this paper, a plasmid-based system was designed to explore the genotoxic mechanism of QDs by detecting changes in DNA configuration and biological activities. The direct chemicobiological interactions between DNA and mercaptoacetic acid-coated CdSecore QDs (MAA–QDs) were investigated. After incubation with different concentrations of MAA–QDs (0.043, 0.13, 0.4, 1.2, and 3.6 μmol/L) in the dark, the DNA conversion of the covalently closed circular (CCC) DNA to the open circular (OC) DNA was significantly enhanced (from 13.9% ± 2.2% to 59.9% ± 12.8%) while the residual transformation activity of plasmid DNA was greatly decreased (from 80.7% ± 12.8% to 13.6% ± 0.8%), which indicated that the damages to the DNA structure and biological activities induced by MAA–QDs were concentration-dependent. The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium–mercaptoacetic acid complex (Cd–MAA) that is formed in the solution of MAA–QDs. Circular dichroism spectroscopy and transformation assay results indicated that the Cd–MAA complex might interact with DNA through the groove-binding mode and prefer binding to DNA fragments with high adenine and thymine content. Furthermore, the plasmid transformation assay could be used as an effective method to evaluate the genotoxicities of nanoparticles. PMID:22679373

  9. The cadmium-mercaptoacetic acid complex contributes to the genotoxicity of mercaptoacetic acid-coated CdSe-core quantum dots.

    PubMed

    Tang, Weikun; Fan, Junpeng; He, Yide; Huang, Bihai; Liu, Huihui; Pang, Daiwen; Xie, Zhixiong

    2012-01-01

    Quantum dots (QDs) have many potential clinical and biological applications because of their advantages over traditional fluorescent dyes. However, the genotoxicity potential of QDs still remains unclear. In this paper, a plasmid-based system was designed to explore the genotoxic mechanism of QDs by detecting changes in DNA configuration and biological activities. The direct chemicobiological interactions between DNA and mercaptoacetic acid-coated CdSecore QDs (MAA-QDs) were investigated. After incubation with different concentrations of MAA-QDs (0.043, 0.13, 0.4, 1.2, and 3.6 μmol/L) in the dark, the DNA conversion of the covalently closed circular (CCC) DNA to the open circular (OC) DNA was significantly enhanced (from 13.9% ± 2.2% to 59.9% ± 12.8%) while the residual transformation activity of plasmid DNA was greatly decreased (from 80.7% ± 12.8% to 13.6% ± 0.8%), which indicated that the damages to the DNA structure and biological activities induced by MAA-QDs were concentration-dependent. The electrospray ionization mass spectrometry data suggested that the observed genotoxicity might be correlated with the cadmium-mercaptoacetic acid complex (Cd-MAA) that is formed in the solution of MAA-QDs. Circular dichroism spectroscopy and transformation assay results indicated that the Cd-MAA complex might interact with DNA through the groove-binding mode and prefer binding to DNA fragments with high adenine and thymine content. Furthermore, the plasmid transformation assay could be used as an effective method to evaluate the genotoxicities of nanoparticles. PMID:22679373

  10. Influence of modes of metal transfer on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals

    SciTech Connect

    Mukherjee, Manidipto; Saha, Saptarshi; Pal, Tapan Kumar; Kanjilal, Prasanta

    2015-04-15

    The present study elaborately discussed the effect of different modes of metal transfer (i.e., short circuit mode, spray mode and pulse mode) on grain structure and direction of grain growth in low nickel austenitic stainless steel weld metals. Electron backscattered diffraction (EBSD) analysis was used to study the grain growth direction and grain structure in weld metals. The changes in grain structure and grain growth direction were found to be essentially varied with the weld pool shape and acting forces induced by modes of metal transfer at a constant welding speed. Short circuit mode of metal transfer owing to higher Marangoni force (M{sub a}) and low electromagnetic force (R{sub m}) promotes the lower weld pool volume (Γ) and higher weld pool maximum radius (r{sub m}). Short circuit mode also shows curved and tapered columnar grain structures and the grain growth preferentially occurred in <001> direction. In contrast, spray mode of metal transfer increases the Γ and reduces the r{sub m} values due to very high R{sub m} and typically reveals straight and broad columnar grain structures with preferential growth direction in <111>. In the pulse mode of metal transfer relatively high M{sub a} and R{sub m} simultaneously increase the weld pool width and the primary penetration which might encourage relatively complex grain growth directions in the weld pool and cause a shift of major intensity from <001> to <111> direction. It can also be concluded that the fusion zone grain structure and direction of grain growth are solely dependent on modes of metal transfer and remain constant for a particular mode of metal transfer irrespective of filler wire used. - Highlights: • Welded joints of LNiASS were prepared by varying modes of metal transfer. • Weld pool shape, grain structure and grain growth direction were studied. • Short circuit mode shows curved and tapered grain growth in <001> direction. • Spray mode shows straight and broad columnar grain growth

  11. Biomonitoring of genotoxic effects for human exposure to nanomaterials: The challenge ahead.

    PubMed

    Gonzalez, Laetitia; Kirsch-Volders, Micheline

    2016-01-01

    Exposures to nanomaterials (NMs), with their specific physico-chemical characteristics, are likely to increase over the next years, as their production for industrial, consumer and medical applications is steadily rising. Therefore, there is an urgent need for the implementation of human biomonitoring studies of genotoxic effects after NM exposures in order to monitor and assure safety for workers and the general population. In this review, most commonly used biomarkers of early genetic effects were analyzed for their adequacy after NM exposures. A more in depth analysis of the ex vivo/in vitro lymphocyte MN assay was performed, although, in literature no studies are available using this assay for NM exposures. Therefore, the known factors determining the NMs tissue/cellular targets and the multiplicity of modes of action of NMs were summarized. The main pending questions are whether (1) lymphocytes are a NM target or an adequate surrogate tissue, (2) whether the buccal MN assay might be more suitable for NM exposures via inhalation or ingestion, as buccal cells might be exposed more directly. While the current state-of-the-art does not allow for drawing firm conclusions, major research gaps are identified and some cautious recommendations can be formulated. Therefore in vitro and in vivo studies should be conducted comparing methodologies side-by-side in the same subjects and for different types of NMs. The ex vivo/in vitro MN assay in its automated version, allowing objective analysis of large cohorts and detection of direct and indirect genotoxic effects, remains a valuable candidate for human biomonitoring to NM exposure. Considering the potential cancer risk from exposure to NMs and previous dramatic experiences with too late surveillance of occupational exposures to similar substances (e.g. to asbestos), there is an urgent need to define and implement adequate scientifically sound biomonitoring methods and programme for exposure to NMs. PMID:27234560

  12. Efficient Bidirectional Quantum Secure Direct Communication with Single Photons in Both Polarization and Spatial-Mode Degrees of Freedom

    NASA Astrophysics Data System (ADS)

    Wang, L. L.; Ma, W. P.; Shen, D. S.; Wang, M. L.

    2015-10-01

    With single photos in both polarization and spatial-mode degrees of freedom,we present an efficient bidirectional quantum secure direct communication (QSDC) protocol is proposed. The participants' secret messages can be transmitted directly in a quantum channel through performing different local unitary operations, which are chosen by the two participants separately from the Pauli operations and Hadamard operations, on the polarization states and the spatial-mode states of single photons. Each single photon in two degrees of freedom can carry two bits of information. Thus the capacity of quantum communication of our protocol is improved. Moreover, we discuss the security of our QSDC network protocol comprehensively. It is showed that the proposed scheme not only can defend several outsider eavesdropper's attacks but also can remove the drawback of information leakage, which prevents the secret messages being leaked out to other people through the public information. In addition, our protocol is practical since the preparation and the measurement of single photon quantum states in both the polarization and the spatial-mode degrees of freedom are available with current quantum techniques.

  13. Direct generation of genuine single-longitudinal-mode narrowband photon pairs

    NASA Astrophysics Data System (ADS)

    Luo, Kai-Hong; Herrmann, Harald; Krapick, Stephan; Brecht, Benjamin; Ricken, Raimund; Quiring, Viktor; Suche, Hubertus; Sohler, Wolfgang; Silberhorn, Christine

    2015-07-01

    The practical prospect of quantum communication and information processing relies on sophisticated single-photon pairs, which feature a controllable waveform, narrow spectrum, excellent purity, fiber compatibility, and miniaturized design. For practical realizations, stable, miniaturized, low-cost devices are required. Sources with one or some of the above characteristics have already been demonstrated, but it is quite challenging to obtain a source with all of the described characteristics simultaneously. Here we report on an integrated single-longitudinal-mode, non-degenerate, narrowband photon pair source that exhibits all the requirements needed for quantum applications. The device is composed of a periodically poled, Ti-indiffused, lithium niobate waveguide with high reflective dielectric mirror coatings deposited on the waveguide end-faces. Photon pairs with wavelengths around 890 and 1320 nm are generated via type II phase-matched parametric down-conversion (PDC). Clustering in this dispersive cavity restricts the whole conversion spectrum to one single-longitudinal mode in a single cluster, yielding a narrow bandwidth of only 60 MHz. The high conversion efficiency in the waveguide, together with the spectral clustering in the doubly resonant waveguide, leads to a high brightness of 3× {10}4 pairs/(s mW MHz). This source exhibits prominent single-longitudinal-mode purity and remarkable temporal shaping capability. In particular, due to temporal broadening, we can observe that the coherence time of the two-photon component of the PDC state is actually longer than that of the single-photon states. The miniaturized monolithic design enables this source to have various fiber communication applications.

  14. The influence of organic solvents on estimates of genotoxicity and antigenotoxicity in the SOS chromotest

    PubMed Central

    Quintero, Nathalia; Stashenko, Elena E.; Fuentes, Jorge Luis

    2012-01-01

    In this work, the toxicity and genotoxicity of organic solvents (acetone, carbon tetrachloride, dichloromethane, dimethylsulfoxide, ethanol, ether and methanol) were studied using the SOS chromotest. The influence of these solvents on the direct genotoxicity induced by the mutagens mitomycin C (MMC) and 4-nitroquinoline-1-oxide (4-NQO) were also investigated. None of the solvents were genotoxic in Escherichia coli PQ37. However, based on the inhibition of protein synthesis assessed by constitutive alkaline phosphatase activity, some solvents (carbon tetrachloride, dimethylsulfoxide, ethanol and ether) were toxic and incompatible with the SOS chromotest. Solvents that were neither toxic nor genotoxic to E. coli (acetone, dichloromethane and methanol) significantly reduced the genotoxicity of MMC and 4-NQO. When these solvents were used to dissolve vitamin E they increased the antigenotoxic activity of this compound, possibly through additive or synergistic effects. The relevance of these results is discussed in relation to antigenotoxic studies. These data indicate the need for careful selection of an appropriate diluent for the SOS chromotest since some solvents can modulate genotoxicity and antigenotoxicity. PMID:22888301

  15. Genotoxic and mutagenic effects of sewage sludge on higher plants.

    PubMed

    Corrêa Martins, Maria Nilza; de Souza, Victor Ventura; Souza, Tatiana da Silva

    2016-02-01

    Sewage treatment yields sludge, which is often used as a soil amendment in agriculture and crop production. Although the sludge contains elevated concentrations of macro and micronutrients, high levels of inorganic and organic compounds with genotoxic and mutagenic properties are present in sludge. Application of sludge in agriculture is a pathway for direct contact of crops to toxic chemicals. The objective of this study was to compile information related to the genotoxic and mutagenic effects of sewage sludge in different plant species. In addition, data are presented on toxicological effects in animals fed with plants grown in soils supplemented with sewage sludge. Despite the benefits of using sewage sludge as organic fertilizer, the data showcased in this review suggest that this residue can induce genetic damage in plants. This review alerts potential risks to health outcomes after the intake of food cultivated in sewage sludge-amended soils. PMID:26643763

  16. Distinct ETA receptor binding mode of macitentan as determined by site directed mutagenesis.

    PubMed

    Gatfield, John; Mueller Grandjean, Celia; Bur, Daniel; Bolli, Martin H; Nayler, Oliver

    2014-01-01

    The competitive endothelin receptor antagonists (ERA) bosentan and ambrisentan, which have long been approved for the treatment of pulmonary arterial hypertension, are characterized by very short (1 min) occupancy half-lives at the ET(A) receptor. The novel ERA macitentan, displays a 20-fold increased receptor occupancy half-life, causing insurmountable antagonism of ET-1-induced signaling in pulmonary arterial smooth muscle cells. We show here that the slow ET(A) receptor dissociation rate of macitentan was shared with a set of structural analogs, whereas compounds structurally related to bosentan displayed fast dissociation kinetics. NMR analysis showed that macitentan adopts a compact structure in aqueous solution and molecular modeling suggests that this conformation tightly fits into a well-defined ET(A) receptor binding pocket. In contrast the structurally different and negatively charged bosentan-type molecules only partially filled this pocket and expanded into an extended endothelin binding site. To further investigate these different ET(A) receptor-antagonist interaction modes, we performed functional studies using ET(A) receptor variants harboring amino acid point mutations in the presumed ERA interaction site. Three ET(A) receptor residues significantly and differentially affected ERA activity: Mutation R326Q did not affect the antagonist activity of macitentan, however the potencies of bosentan and ambrisentan were significantly reduced; mutation L322A rendered macitentan less potent, whereas bosentan and ambrisentan were unaffected; mutation I355A significantly reduced bosentan potency, but not ambrisentan and macitentan potencies. This suggests that--in contrast to bosentan and ambrisentan--macitentan-ET(A) receptor binding is not dependent on strong charge-charge interactions, but depends predominantly on hydrophobic interactions. This different binding mode could be the reason for macitentan's sustained target occupancy and insurmountable

  17. H-mode and Edge Physics on the Pegasus ST: Progress and Future Directions

    NASA Astrophysics Data System (ADS)

    Bongard, M. W.; Bodner, G. M.; Barr, J. L.; Burke, M. G.; Fonck, R. J.; Hinson, E. T.; Kriete, D. M.; Lewicki, B. T.; Perry, J. M.; Reusch, J. A.; Schlossberg, D. J.; Thome, K. E.; Winz, G. R.

    2015-11-01

    Ohmic H-modes are routinely attained on the Pegasus ST, in part due to the low L-H power threshold PLH arising from low-BT operation at A ~ 1 . Characteristics of H-mode include: improved τe, consistent with H98 ~ 1 edge current and pressure pedestal formation; and the occurrence of ELMs. Experiments in the past year have examined magnetic topology and density dependencies of PLH in detail. PLH exceeds ITER L-H scaling values by 10-20 ×, with PLH /PITPA 08 increasing sharply as A --> 1 . No PLH-minimizing density has been found. Unlike at high- A, PLH is insensitive to limited or diverted magnetic topologies to date. The low BT and modest pedestal values at A ~ 1 afford unique edge diagnostic accessibility to investigate ELMs and their nonlinear dynamics. Jedge (R , t) measured through a Type I ELM shows a complex pedestal collapse and filament ejection. These studies are being extended to higher Ip and longer pulse length with LHI startup to conserve Ohmic V-s and improve MHD stability. A modest-cost upgrade to the facility will enable detailed validation studies of nonlinear ELM dynamics and ELM control. This initiative will upgrade the centerstack, increasing BT by × 3 , Ohmic V-s by × 4 , and pulse lengths to 100 ms at A < 1 . 3 , as well as deploy a comprehensive 3D magnetic perturbation coil system with full poloidal coverage from frame coils and helical centerstack windings. Work supported by US DOE grant DE-FG02-96ER54375.

  18. Heating mode transition in a hybrid direct current/dual-frequency capacitively coupled CF{sub 4} discharge

    SciTech Connect

    Zhang, Quan-Zhi; Wang, You-Nian; Bogaerts, Annemie

    2014-06-14

    Computer simulations based on the particle-in-cell/Monte Carlo collision method are performed to study the plasma characteristics and especially the transition in electron heating mechanisms in a hybrid direct current (dc)/dual-frequency (DF) capacitively coupled CF{sub 4} discharge. When applying a superposed dc voltage, the plasma density first increases, then decreases, and finally increases again, which is in good agreement with experiments. This trend can be explained by the transition between the four main heating modes, i.e., DF coupling, dc and DF coupling, dc source dominant heating, and secondary electron dominant heating.

  19. Comparison of epoxy- and siloxane-based single-mode optical waveguides defined by direct-write lithography

    NASA Astrophysics Data System (ADS)

    Elmogi, Ahmed; Bosman, Erwin; Missinne, Jeroen; Van Steenberge, Geert

    2016-02-01

    This paper reports on the fabrication and characterization of single-mode polymer optical waveguides at telecom and SOI compatible wavelengths; by making a comparison between an epoxy and a siloxane polymer waveguide material system (both commercially-available). The proposed waveguides can be used in short-reach optical interconnects targeting chip-to-chip communication on the interposer level or providing a coupling interface between single-mode optical fibers and photonic integrated circuits (PICs). This technology enables the integration of optoelectronic chips for photonic packaging purposes. First, the single-mode dimensions (4 × 4 μm2 and 5 × 5 μm2) for both materials at selected wavelengths (1.31 μm and 1.55 μm) were determined based on the refractive index measurements. Then, the waveguides were patterned by a direct-write lithography method. The fabricated waveguides show a high-quality surface with smooth sidewalls. The optical propagation losses were measured using the cut-back method. For the siloxane-based waveguides, the propagation losses were found to be 0.34 dB/cm and 1.36 dB/cm at 1.31 μm and 1.55 μm respectively while for the epoxy-based waveguides the losses were 0.49 dB/cm and 2.23 dB/cm at 1.31 μm and 1.55 μm respectively.

  20. Three-party Quantum Secure Direct Communication with Single Photons in both Polarization and Spatial-mode Degrees of Freedom

    NASA Astrophysics Data System (ADS)

    Wang, LiLi; Ma, WenPing; Wang, MeiLing; Shen, DongSu

    2016-05-01

    We present an efficient three-party quantum secure direct communication (QSDC) protocol with single photos in both polarization and spatial-mode degrees of freedom. The three legal parties' messages can be encoded on the polarization and the spatial-mode states of single photons independently with desired unitary operations. A party can obtain the other two parties' messages simultaneously through a quantum channel. Because no extra public information is transmitted in the classical channels, the drawback of information leakage or classical correlation does not exist in the proposed scheme. Moreover, the comprehensive security analysis shows that the presented QSDC network protocol can defend the outsider eavesdropper's several sorts of attacks. Compared with the single photons with only one degree of freedom, our protocol based on the single photons in two degrees of freedom has higher capacity. Since the preparation and the measurement of single photon quantum states in both the polarization and the spatial-mode degrees of freedom are available with current quantum techniques, the proposed protocol is practical.

  1. Genotoxicity of streptonigrin: a review.

    PubMed

    Bolzán, A D; Bianchi, M S

    2001-03-01

    Streptonigrin (SN, CAS no. 3930-19-6) is an aminoquinone antitumor antibiotic isolated from cultures of Streptomyces flocculus. This compound is a member of a group of antitumor agents which possess the aminoquinone moiety and that includes also mitomycin C, porfiromycin, actinomycin, rifamycin and geldanamycin. Because of the potential use of SN in clinical chemotherapy, the study of its genotoxicity has considerable practical significance.SN inhibits the synthesis of DNA and RNA, causes DNA strand breaks after reduction with NADH, induces unscheduled DNA synthesis and DNA adducts and inhibits topoisomerase II. At the chromosome level, this antibiotic causes chromosome damage and increases the frequency of sister-chromatid exchanges.SN cleaves DNA in cell-free systems by a mechanism that involves complexing with metal ions and autoxidation of the quinone moiety to semiquinone in the presence of NADH with production of oxygen-derived reactive species. Recent evidence strongly suggests that the clastogenic action of this compound is partially mediated by free radicals. The present review aims at summarizing past and current knowledge concerning the genotoxic effects of SN. PMID:11223403

  2. Measurement of direct photon emission in the K(L) ---> pi+ pi- gamma decay mode

    SciTech Connect

    Abouzaid, E.; Arenton, M.; Barker, A.R.; Bellantoni, L.; Bellavance, A.; Blucher, E.; Bock, G.J.; Cheu, E.; Coleman, R.; Corcoran, M.D.; Corti, G.; /Virginia U. /Wisconsin U., Madison

    2006-04-01

    In this paper the KTeV collaboration reports the analysis of 112.1 x 10{sup 3} candidate K{sub L} {yields} {pi}{sup +}{pi}{sup -}{gamma} decays including a background of 671 {+-} 41 events with the objective of determining the photon production mechanisms intrinsic to the decay process. These decays have been analyzed to extract the relative contributions of the Cp violating bremsstrahlung process and the CP conserving M1 and CP violating E1 direct photon emission processes. The M1 direct photon emission amplitude and its associated vector form factor parameterized as |{bar g}{sub M1}|(1 + a{sub 1}/a{sub 2}/(M{sub {rho}}{sup 2}-M{sub K}{sup 2}) + 2M{sub K}E{sub {gamma}}) have been measured to be |{bar g}{sub M1}| = 1.198 {+-} 0.035(stat) {+-} 0.086(syst) and a{sub 1}/a{sub 2} = =0.738 {+-} 0.007(stat) {+-} 0.018(syst) GeV{sup 2}/c{sup 2} respectively. An upper limit for the CP violating E1 direct emission amplitude |g{sub E1}| {le} 0.1 (90%CL) has been found. The overall ratio of direct photon emission (DE) to total photon emission including the bremsstrahlung process (IB) has been determined to be DE/(DE + IB) = 0.689 {+-} 0.021 for E{sub {gamma}} {ge} 20 MeV.

  3. Dermal fibroblast infiltration of poly(ε-caprolactone) scaffolds fabricated by melt electrospinning in a direct writing mode.

    PubMed

    Farrugia, Brooke L; Brown, Toby D; Upton, Zee; Hutmacher, Dietmar W; Dalton, Paul D; Dargaville, Tim R

    2013-06-01

    Melt electrospinning in a direct writing mode is a recent additive manufacturing approach to fabricate porous scaffolds for tissue engineering applications. In this study, we describe porous and cell-invasive poly (ε-caprolactone) scaffolds fabricated by combining melt electrospinning and a programmable x-y stage. Fibers were 7.5 ± 1.6 µm in diameter and separated by interfiber distances ranging from 8 to 133 µm, with an average of 46 ± 22 µm. Micro-computed tomography revealed that the resulting scaffolds had a highly porous (87%), three-dimensional structure. Due to the high porosity and interconnectivity of the scaffolds, a top-seeding method was adequate to achieve fibroblast penetration, with cells present throughout and underneath the scaffold. This was confirmed histologically, whereby a 3D fibroblast-scaffold construct with full cellular penetration was produced after 14 days in vitro. Immunohistochemistry was used to confirm the presence and even distribution of the key dermal extracellular matrix proteins, collagen type I and fibronectin. These results show that melt electrospinning in a direct writing mode can produce cell invasive scaffolds, using simple top-seeding approaches. PMID:23443534

  4. Histaminergic nerves demonstrated in the skin. A new direct mode of neurogenic inflammation?

    PubMed

    Johansson, O; Virtanen, M; Hilliges, M

    1995-04-01

    An intradermal administration of histamine into human skin results in a local erythema, edema and often also the sensations of itch and/or pain. These effects have classically been attributed to the presence of histamine-containing mast cells. However, in the present investigation, we report the observation of histamine-immunoreactive nerves in the skin of Sprague-Dawley rats using a new and highly sensitive immunohistochemical approach. These data suggest a more direct route of cutaneous histamine effects, mediated exclusively by the peripheral nervous system. The findings could also give a new basis for explaining histamine-related issues, such as itch. PMID:7543795

  5. Direct single-mode fibre-coupled miniature White cell for laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Kühnreich, Benjamin; Höh, Matthias; Wagner, Steven; Ebert, Volker

    2016-02-01

    We present the design, setup, and characterization of a new lens-free fibre-coupled miniature White cell for extractive gas analysis using direct tunable diode laser absorption spectroscopy (dTDLAS). The construction of this cell is based on a modified White cell design and allows for an easy variation of the absorption length in the range from 29 cm to 146 cm. The design avoids parasitic absorption paths outside the cell by using direct, lensless fibre coupling and allows small physical cell dimensions and cell volumes. To characterize the cell performance, different H2O and CH4 concentration levels were measured using dTDLAS. Detection limits of 2.5 ppm ṡ m for CH4 (at 1.65 μm) and 1.3 ppm ṡ m for H2O (at 1.37 μm) were achieved. In addition, the gas exchange time and its flow-rate dependence were determined for both species and found to be less than 15 s for CH4 and up to a factor of thirteen longer for H2O.

  6. METABOLISM AND GENOTOXICITY OF 1-NITROPYRENE

    EPA Science Inventory

    1-Nitropyrene (NP), a nitrated polycyclic aromatic hydrocarbon and a potent bacterial mutagen, has been identified in combustion emissions and may contribute to the burden of genotoxicity associated with air pollution. NP undergoes rapid metabolism by rat hepatic subcellular frac...

  7. Assessing of genotoxicity of 16 centralized source-waters in China by means of the SOS/umu assay and the micronucleus test: initial identification of the potential genotoxicants by use of a GC/MS method and the QSAR Toolbox 3.0.

    PubMed

    Ye, Yan; Weiwei, Jiang; Na, Li; Mei, Ma; Donghong, Wang; Zijian, Wang; Kaifeng, Rao

    2014-03-15

    Only few studies were conducted to assess genotoxicity of centralized source waters in China and almost none of them dealt with the causal relationship between the genotoxic effect and genotoxicants. In this work, 16 centralized source waters in China were sampled from five river systems and genotoxicity of their organic extracts was assessed by use of the SOS/umu test for DNA-damaging effect and the miniaturized flow cytometry-based micronucleus (MN) test for chromosome-damaging effect. In addition, initial identification of potential genotoxicants for the six samples from the Yangtze River was done with a GC/MS method and the QSAR toolbox 3.0. The results demonstrate that eight samples showed both indirect and direct DNA-damaging effects, another four samples showed only indirect DNA-damaging effects, while chromosome-damaging effects were found for 14 out of the 16 samples, in which aneugenic and clastogenic modes of action were found for 4 and 10 samples, respectively. Both direct/indirect DNA-damaging effects and chromosome-damaging effects were induced by the six Yangtze River samples, and the existing different types of genotoxicant confirmed the results. Furthermore, o-phenylphenol was initially identified as the major cause for the DNA-damaging effects while PAHs, pesticides, phenol and anthraquinone were identified as ubiquitous chromosome-damaging agents among these samples. In conclusion, a combination of the SOS/umu test and the miniaturized flow cytometry-based MN test to detect both DNA-damaging and chromosome-damaging effects could be used as a comprehensive genotoxicity assessment tool for the evaluation and classification of genotoxicity of complex mixtures, and potential genotoxicants can be initially identified with additional information from chemical analysis and the QSAR toolbox. PMID:24525378

  8. Ameliorative effect of certain antioxidants against mercury induced genotoxicity in peripheral blood lymphocytes.

    PubMed

    Patel, Tapan A; Rao, Mandava V

    2015-10-01

    Various antioxidants play an important role in reducing the reactive oxygen species (ROS) by scavenging them directly or indirectly. Mercury (Hg) is one of the known hazardous genotoxicant, induces the genotoxicity by enhancing the ROS. In the present study, three structurally different bioactive compounds such as melatonin (0.2 mM), curcumin (3.87 µM) and andrographolide (0.4 µM) were evaluated against the genotoxic effect of mercury. All the experiments were conducted using the peripheral blood lymphocytes In Vitro. The cultures were exposed to different doses (2.63 µM; 6.57 µM; 10.52 µM) of mercury salt (HgCl2) for studying various genotoxic indices. All three antioxidant compounds, alone and in combination with high dose of mercury, were added to the cultures with controls. For ascertaining genotoxicity, sister chromatid exchanges (SCEs), cell cycle proliferative index/replicative index (CCPI/RI), average generation time (AGT), population doubling time (PDT), %M1, %M2 and %M3 were assessed and analyzed using suitable statistical analysis. The results revealed a dose dependent increase in SCEs, AGT and PDT, with a concomitant reduction in CCPI values after treatment of mercury. Supplementation of these three antioxidant compounds effectively negated these genotoxic endpoints in treated cultures with improvement in the cell cycle kinetics i.e. CCPI. The antimutagenic activity of these compounds on mercury induced genotoxicity was in the following order: melatonin > curcumin > andrographolide. In conclusion, these compounds have ameliorated mercury induced increase in genotoxic indices due to their excellent antioxidant properties and the combination seems to be effective. PMID:25645230

  9. Based on interval type-2 fuzzy-neural network direct adaptive sliding mode control for SISO nonlinear systems

    NASA Astrophysics Data System (ADS)

    Lin, Tsung-Chih

    2010-12-01

    In this paper, a novel direct adaptive interval type-2 fuzzy-neural tracking control equipped with sliding mode and Lyapunov synthesis approach is proposed to handle the training data corrupted by noise or rule uncertainties for nonlinear SISO nonlinear systems involving external disturbances. By employing adaptive fuzzy-neural control theory, the update laws will be derived for approximating the uncertain nonlinear dynamical system. In the meantime, the sliding mode control method and the Lyapunov stability criterion are incorporated into the adaptive fuzzy-neural control scheme such that the derived controller is robust with respect to unmodeled dynamics, external disturbance and approximation errors. In comparison with conventional methods, the advocated approach not only guarantees closed-loop stability but also the output tracking error of the overall system will converge to zero asymptotically without prior knowledge on the upper bound of the lumped uncertainty. Furthermore, chattering effect of the control input will be substantially reduced by the proposed technique. To illustrate the performance of the proposed method, finally simulation example will be given.

  10. Study of a dual mode SWIR active imaging system for direct imaging and non-line-of-sight vision

    NASA Astrophysics Data System (ADS)

    Laurenzis, Martin; Christnacher, Frank; Velten, Andreas

    2015-05-01

    The application of non-line of sight vision and see around a corner has been demonstrated in the recent past on laboratory level with round trip path lengths on the scale of 1 m as well as 10 m. This method uses a computational imaging approach to analyze the scattered information of objects which are hidden from the direct sensors field of view. Recent demonstrator systems were driven at laser wavelengths (800 nm and 532 nm) which are far from the eye-safe shortwave infrared (SWIR) wavelength band i.e. between 1.4 μm and 2 μm. Therefore, the application in public or inhabited areas is difficult with respect to international laser safety conventions. In the present work, the authors evaluate the application of recent eye safe laser sources and sensor devices for non-line of sight sensing and give predictions on range and resolution. Further, the realization of a dual mode concept is studied enabling both, the direct view on a scene and the indirect view on a hidden scene. While recent laser gated viewing sensors have high spatial resolution, their application in non-line of sight imaging suffer from a too low temporal resolution due to minimal sensor gate width of around 150 ns. On the other hand, Geiger-mode single photon counting devices have high temporal resolution, but their spatial resolution is (until now) limited to array sizes of some thousand sensor elements. In this publication the authors present detailed theoretical and experimental evaluations.

  11. Employment of adult mammalian primary cells in toxicology: In vivo and in vitro genotoxic effects of environmentally significant N-nitrosodialkylamines in cells of the liver, lung, and kidney

    SciTech Connect

    Pool, B.L.; Brendler, S.Y.; Liegibel, U.M.; Schmezer, P. ); Tompa, A. )

    1990-01-01

    This report focuses on the use of freshly isolated primary mammalian cells from different tissues and organs of the rat for the rapid and efficient analysis of toxic and genotoxic chemicals. The cells are either treated in vitro or they are isolated from treated animals. Viability by trypan blue exclusion and DNA damage as single-strand breaks are monitored in either case. Therefore, it is possible to compare in vitro and in vivo results directly. N-nitrosamines with unique organ-specific modes in carcinogenesis were studied in vitro using hepatocytes derived from three species (rat, hamster, and pig) and in rat lung and kidney cells. The sensitive detection of all carcinogenic nitrosamines was achieved, although a pattern of cell-specific activation was not observable. The new modification of the in vivo approach allowed the sensitive detection of NDMA genotoxicity in hepatic and in extrahepatic tissues. It is important to point out that the method is an efficient tool for toxicokinetic studies with genotoxic carcinogens in vivo.

  12. Genotoxicity of organic extracts of airborne particles in somatic cells of Drosophila melanogaster.

    PubMed

    Delgado-Rodríguez, A; Ortíz-Marttelo, R; Villalobos-Pietrini, R; Gómez-Arroyo, S; Graf, U

    1999-07-01

    Complex mixtures extracted from air filters exposed for 24 h in two sessions (27 July and 02 August 1991) and at two locations (Merced, downtown, and Pedregal de San Angel, south-west) in Mexico City were analysed. The organic extracts were from airborne particles equal or smaller than 10 microns (PM10), and from total suspended particles (TSP). These organic extracts were assayed in the somatic mutation and recombination test (SMART) in wings of Drosophila melanogaster using two different crosses as well as in the Salmonella/microsome assay using strain TA98 with and without S9 fraction. The presence of polycyclic aromatic hydrocarbons (PAH) in the extracts was determined by gas chromatography. The genotoxic activities observed in the two test systems were comparable with the indirect mutagens producing greater response than the direct mutagens. The quantities of particulate matter as well as the genotoxic activities were higher on 02 August than on 27 July 1991 for both locations. The amounts of airborne particles and the resulting genotoxic activities were higher at Merced than at Pedregal. In both biological systems, PM10 were more genotoxic than TSP. These results demonstrate the sensitivity of the Drosophila wing SMART-which is an in vivo eukaryotic genotoxicity assay-as a biological monitor of environmental pollution related to airborne particles. PMID:10377966

  13. Protective Effects of Quercetin against Dimethoate-Induced Cytotoxicity and Genotoxicity in Allium sativum Test

    PubMed Central

    Ahmad, Waseem; Shaikh, Sibhghatulla; Nazam, Nazia; Lone, Mohammad Iqbal

    2014-01-01

    The present investigation was directed to study the possible protective activity of quercetin—a natural antioxidant against dimethoate-induced cyto- and genotoxicity in meristematic cells of Allium sativum. So far there is no report on the biological properties of quercetin in plant test systems. Chromosome breaks, multipolar anaphase, stick chromosome, and mitotic activity were undertaken in the current study as markers of cyto- and genotoxicity. Untreated control, quercetin controls (@ 5, 10 and 20 μg/mL for 3 h), and dimethoate exposed groups (@ 100 and 200 μg/mL for 3 h) were maintained. For protection against cytogenotoxicity, the root tip cells treated with dimethoate at 100 and 200 μg/mL for 3 h and quercetin treatment at 5, 10, and 20 μg/mL for 16 h, prior to dimethoate treatment, were undertaken. Quercetin was found to be neither cytotoxic nor genotoxic in Allium sativum control at these doses. A significant increase (P < 0.05) in chromosomal aberrations was noted in dimethoate treated Allium. Pretreatment of Allium sativum with quercetin significantly (P < 0.05) reduced dimethoate-induced genotoxicity and cytotoxicity in meristematic cells, and these effects were dose dependent. In conclusion, quercetin has a protective role in the abatement of dimethoate-induced cyto- and genotoxicity in the meristematic cells of Allium sativum that resides, at least in part, on its antioxidant effects. PMID:27379342

  14. High speed flux feedback for tuning a universal field oriented controller capable of operating in direct and indirect field orientation modes

    SciTech Connect

    De Doncker, Rik W. A. A.

    1992-01-01

    The direct (d) and quadrature (q) components of flux, as sensed by flux sensors or determined from voltage and current measurements in a direct field orientation scheme, are processed rapidly and accurately to provide flux amplitude and angular position values for use by the vector rotator of a universal field-oriented (UFO) controller. Flux amplitude (linear or squared) is provided as feedback to tune the UFO controller for operation in direct and indirect field orientation modes and enables smooth transitions from one mode to the other.

  15. High speed flux feedback for tuning a universal field oriented controller capable of operating in direct and indirect field orientation modes

    DOEpatents

    De Doncker, R.W.A.A.

    1992-09-01

    The direct (d) and quadrature (q) components of flux, as sensed by flux sensors or determined from voltage and current measurements in a direct field orientation scheme, are processed rapidly and accurately to provide flux amplitude and angular position values for use by the vector rotator of a universal field-oriented (UFO) controller. Flux amplitude (linear or squared) is provided as feedback to tune the UFO controller for operation in direct and indirect field orientation modes and enables smooth transitions from one mode to the other. 3 figs.

  16. Acrolein genotoxicity in Drosophila melanogaster. III. Effects of metabolism modification.

    PubMed

    Barros, A R; Sierra, L M; Comendador, M A

    1994-05-01

    In order to investigate the role of metabolism in acrolein genotoxicity in D. melanogaster, the action of several metabolism modifiers, namely phenobarbital, an inducer of xenobiotic metabolism, phenylimidazole and iproniazid, inhibitors of oxidative activities of cytochrome P450, and diethyl maleate, a glutathione-depleting agent, have been assayed using the sex-linked recessive lethal (SLRL) test, with two different administration routes (feeding and injection). The results support the hypothesis that acrolein is not only a direct mutagen but is also transformed, by oxidative activities of cytochrome P450 after glutathione conjugation, into an active metabolite, possibly glycidaldehyde. Moreover, acrolein is deactivated by an enzymatic activity induced by phenobarbital. PMID:7513061

  17. Method for direct detection of pitch angle scattering of energetic electrons caused by whistler mode chorus emissions

    NASA Astrophysics Data System (ADS)

    Kitahara, M.; Katoh, Y.

    2016-06-01

    The Wave-Particle Interaction Analyzer (WPIA), a new instrument proposed by Fukuhara et al. (2009), measures the relative phase angle between the wave magnetic field vector and the velocity vector of each particle and calculates the energy exchange from waves to particles. In this study, we expand its applicability by proposing a method of using the WPIA to directly detect pitch angle scattering of resonant particles by plasma waves by calculating the g values. The g value is defined as the accumulation value of the Lorentz force acting on each particle and indicates the lost momentum of waves. We apply the proposed method to the results of a one-dimensional electron hybrid simulation reproducing the generation of whistler mode chorus emissions around the magnetic equator. Using the wave and particle data obtained at fixed observation points assumed in the simulation system, we conduct a pseudo-observation of the simulation result using the WPIA and analyze the g values. Our analysis yielded significant values indicating the strong pitch angle scattering for electrons in the kinetic energy and pitch angle ranges satisfying the cyclotron resonance condition with the reproduced chorus emissions. The results of this study demonstrate that the proposed method enables us to directly and quantitatively identify the location at which pitch angle scattering occurs in the simulation system and that the method can be applied to the results of space-based observations by the forthcoming Exploration of energization and Radiation in Geospace (ERG) satellite.

  18. METHYLATED ARSENICIII SPECIES ARE POTENTIAL PROXIMATE OR ULTIMATE GENOTOXIC FORMS OF ARSENIC

    EPA Science Inventory

    METHYLATED ARSENIC(III) SPECIES ARE POTENTIAL PROXIMATE OR UL TIMA TE GENOTOXIC FORMS OF ARSENIC

    Inorganic arsenic (iAs, arsenite and arsenate) has been thought to act as a genotoxicant without reacting directly with DNA; neither iAs nor As(V) methylated metabolites are e...

  19. Development of a Fish Cell Biosensor System for Genotoxicity Detection Based on DNA Damage-Induced Trans-Activation of p21 Gene Expression

    PubMed Central

    Geng, Deyu; Zhang, Zhixia; Guo, Huarong

    2012-01-01

    p21CIP1/WAF1 is a p53-target gene in response to cellular DNA damage. Here we report the development of a fish cell biosensor system for high throughput genotoxicity detection of new drugs, by stably integrating two reporter plasmids of pGL3-p21-luc (human p21 promoter linked to firefly luciferase) and pRL-CMV-luc (CMV promoter linked to Renilla luciferase) into marine flatfish flounder gill (FG) cells, referred to as p21FGLuc. Initial validation of this genotoxicity biosensor system showed that p21FGLuc cells had a wild-type p53 signaling pathway and responded positively to the challenge of both directly acting genotoxic agents (bleomycin and mitomycin C) and indirectly acting genotoxic agents (cyclophosphamide with metabolic activation), but negatively to cyclophosphamide without metabolic activation and the non-genotoxic agents ethanol and D-mannitol, thus confirming a high specificity and sensitivity, fast and stable response to genotoxic agents for this easily maintained fish cell biosensor system. This system was especially useful in the genotoxicity detection of Di(2-ethylhexyl) phthalate (DEHP), a rodent carcinogen, but negatively reported in most non-mammalian in vitro mutation assays, by providing a strong indication of genotoxicity for DEHP. A limitation for this biosensor system was that it might give false positive results in response to sodium butyrate and any other agents, which can trans-activate the p21 gene in a p53-independent manner. PMID:25585933

  20. Photoactivated hypericin is not genotoxic.

    PubMed

    Feruszová, Jana; Imreová, Petronela; Bodnárová, Kristína; Ševčovičová, Andrea; Kyzek, Stanislav; Chalupa, Ivan; Gálová, Eliška; Miadoková, Eva

    2016-04-01

    The study was designed to test the potential photogenotoxicity of hypericin (HYP) at three different levels: primary DNA damages, gene mutations and chromosome aberrations. Primary genetic changes were detected using the comet assay. The potential mutagenic activity of HYP was assessed using the Ames/Salmonella typhimurium assay. Finally, the ability of photoactivated HYP to induce chromosome aberrations was evaluated by the in vitro mammalian chromosome aberration test and compared to that of non-photoactivated HYP. The results have shown that photoactivated HYP can only induce primary DNA damages (single-strand DNA breaks), acting in a dose-response manner. This activity depended both on HYP concentrations and an intensity of the light energy needed for its photoactivation. However, mutagenic effect of photoactivated HYP evaluated in the Ames assay using three bacterial strains S. typhimurium (TA97, TA98 and TA100) was not confirmed. Moreover, photoactivated HYP in the range of concentrations (0.005-0.01 µg/ml) was not found to be clastogenic against HepG2 cells. Our findings from both the Ames assay and the chromosome aberrations test provide evidence that photoactivated HYP is not genotoxic, which might be of great importance mainly in terms of its use in the photodynamic therapy. PMID:26891274

  1. Insecticidal, mutagenic and genotoxic evaluation of annonaceous acetogenins.

    PubMed

    Alvarez Colom, Olga; Salvatore, Analia; Willink, Eduardo; Ordóñez, Roxana; Isla, María I; Neske, Adriana; Bardón, Alicia

    2010-03-01

    Annonaceous acetogenins represent a class of bioactive compounds whose primary mode of action is the inhibition of NADH-ubiquinone oxidoreductase (Mitochondrial Complex I). Given the potential pesticidal use of these compounds, we evaluated the effects of seven acetogenins: squamocin (1), molvizarin (2), itrabin (3), almuñequin (4), cherimolin-1 (5), cherimolin-2 (6), and tucumanin (7) isolated from Annona cherimolia Mill. against Ceratitis capitata Wiedemann (Tephritidae). These acetogenins did not display insecticidal action at 250 microg of treatment per g of adult diet. However, the oviposition capacity of C. capitata females was significantly altered by some of the acetogenins at this concentration. The most potent compounds were itrabin, molvizarin and squamocin. Moreover, significant differences were detected in the preference of oviposition sites when itrabin and squamocin were spread on the surface of artificial fruits at doses of 30 microg/cm2. Additionally, we investigated the mutagenic effects displayed by itrabin, as well as the phytotoxic and genotoxic action of squamocin and itrabin. Both compounds displayed slight phytotoxic and genotoxic effects on roots of Allium cepa at 2.5 microg/mL though no mutagenic effects were detected at 0.25, 0.5 and 2.5 microg/mL on Salmonella typhimurium strains TA98 and TA100. PMID:20420314

  2. Genotoxic sensitivity of the developing hematopoietic system.

    PubMed

    Udroiu, Ion; Sgura, Antonella

    2016-01-01

    Genotoxic sensitivity seems to vary during ontogenetic development. Animal studies have shown that the spontaneous mutation rate is higher during pregnancy and infancy than in adulthood. Human and animal studies have found higher levels of DNA damage and mutations induced by mutagens in fetuses/newborns than in adults. This greater susceptibility could be due to reduced DNA repair capacity. In fact, several studies indicated that some DNA repair pathways seem to be deficient during ontogenesis. This has been demonstrated also in murine hematopoietic stem cells. Genotoxicity in the hematopoietic system has been widely studied for several reasons: it is easy to assess, deals with populations cycling also in the adults and may be relevant for leukemogenesis. Reviewing the literature concerning the application of the micronucleus test (a validated assay to assess genotoxicity) in fetus/newborns and adults, we found that the former show almost always higher values than the latter, both in animals treated with genotoxic substances and in those untreated. Therefore, we draw the conclusion that the genotoxic sensitivity of the hematopoietic system is more pronounced during fetal life and decreases during ontogenic development. PMID:27036061

  3. GENOTOXICITY OF TOBACCO SMOKE AND TOBACCO SMOKE CONDENSATE: A REVIEW

    EPA Science Inventory

    Genotoxicity of Tobacco Smoke and Tobacco Smoke Condensate: A Review
    Abstract
    This report reviews the literature on the genotoxicity of main-stream tobacco smoke and cigarette smoke condensate (CSC) published since 1985. CSC is genotoxic in nearly all systems in which it h...

  4. Identification of the direction and value of the wave length of each mode for a rotating tire using the phase difference method

    NASA Astrophysics Data System (ADS)

    Lee, Jongsuh; Wang, Semyung; Kindt, Peter; Pluymers, Bert; Desmet, Wim

    2016-02-01

    Natural frequencies, mode shapes and modal damping values are the most important parameters to describe the noise and vibration behavior of a mechanical system. For rotating machinery, however, the directivity of the propagation wave and the wave length of each mode should also be taken into account. Generally, the information on directivity and wave length is obtained on the basis of the mode shape result, which is estimated from several measurements measured at different locations. In this research, the accurate directivity and wave length results will be observed by calculating the phase difference at two different locations. The limitation of the proposed method, which arises from the difference between the assumed ring model and the real tire, will be explained, and a method to address the limitation is introduced. The proposed method is verified by applying it to experimental measurements, and a brief explanation of the obtained results is provided.

  5. Intensity modulation and direct detection Alamouti polarization-time coding for optical fiber transmission systems with polarization mode dispersion

    NASA Astrophysics Data System (ADS)

    Reza, Ahmed Galib; Rhee, June-Koo Kevin

    2016-07-01

    Alamouti space-time coding is modified in the form of polarization-time coding to combat against polarization mode dispersion (PMD) impairments in exploiting a polarization diversity multiplex (PDM) gain with simple intensity modulation and direct detection (IM/DD) in optical transmission systems. A theoretical model for the proposed IM/DD Alamouti polarization-time coding (APTC-IM/DD) using nonreturn-to-zero on-off keying signal can surprisingly eliminate the requirement of channel estimation for decoding in the low PMD regime, when a two-transmitter and two-receiver channel is adopted. Even in the high PMD regime, the proposed APTC-IM/DD still reveals coding gain demonstrating the robustness of APTC-IM/DD. In addition, this scheme can eliminate the requirements for a polarization state controller, a coherent receiver, and a high-speed analog-to-digital converter at a receiver. Simulation results reveal that the proposed APTC scheme is able to reduce the optical signal-to-noise ratio requirement by ˜3 dB and significantly enhance the PMD tolerance of a PDM-based IM/DD system.

  6. Mechanisms of non-genotoxic carcinogenesis.

    PubMed

    Shaw, I C; Jones, H B

    1994-03-01

    Until recently, the mechanism of carcinogenesis has been regarded as a two-stage phenomenon involving damage to the genetic material, which initiates the process, followed by a cell-division stimulus, which promotes the development of the tumour. However, exposure to some chemicals has been shown to result in carcinogenesis without involvement of the initiation step. The mechanism of non-genotoxic carcinogenesis is not fully understood, but is believed to involve stimulation of cell division with a consequent increased probability of a mutation occurring spontaneously. In this article, Ian Shaw and Huw Jones review the theories of non-genotoxic carcinogenesis with reference to specific examples of known non-genotoxic carcinogens. PMID:8184492

  7. Environmental genotoxicity: Probing the underlying mechanisms

    SciTech Connect

    Shugart, L.; Theodorakis, C.

    1993-12-31

    Environmental pollution is a complex issue because of the diversity of anthropogenic agents, both chemical and physical, that have been detected and catalogued. The consequences to biota from exposure to genotoxic agents present an additional problem because of the potential for these agents to produce adverse change at the cellular and organismal levels. Past studies in genetic toxicology at the Oak Ridge National Laboratory have focused on structural damage to the DNA of environmental species that may occur after exposure to genotoxic agents and the use of this information to document exposure and to monitor remediation. In an effort to predict effects at the population, community and ecosystem levels, current studies in genetic ecotoxicology are attempting to characterize the biological mechanisms at the gene level that regulate and limit the response of an individual organism to genotoxic factors in their environment.

  8. Evaluation of the genotoxic potential of alkylalkanolamines.

    PubMed

    Leung, H W; Ballantyne, B

    1997-09-18

    Three alkylalkanolamines, N,N-dimethylethanolamine, N-methyldiethanolamine, and tert-butyldiethanolamine, were evaluated for potential genotoxic activity using the Salmonella/microsome reverse gene mutation test, the CHO/HGPRT forward gene mutation test, a sister chromatid exchange test in cultured CHO cells, and an in vivo peripheral blood micronucleus test in Swiss-Webster mice. None of the three alkylalkanolamines produced any significant or dose-related increases in the frequencies of mutations, sister chromatid exchanges or micronuclei. These results indicate that N,N-dimethylethanolamine, N-methyldiethanolamine, and tert-butyldiethanolamine are not genotoxic in the tests conducted. PMID:9357557

  9. Exploring hydrocarbon-bearing shale formations with multi-component seismic technology and evaluating direct shear modes produced by vertical-force sources

    NASA Astrophysics Data System (ADS)

    Alkan, Engin

    It is essential to understand natural fracture systems embedded in shale-gas reservoirs and the stress fields that influence how induced fractures form in targeted shale units. Multicomponent seismic technology and elastic seismic stratigraphy allow geologic formations to be better images through analysis of different S-wave modes as well as the P-wave mode. Significant amounts of energy produced by P-wave sources radiate through the Earth as downgoing SV-wave energy. A vertical-force source is an effective source for direct SV radiation and provides a pure shear-wave mode (SV-SV) that should reveal crucial information about geologic surfaces located in anisotropic media. SV-SV shear wave modes should carry important information about petrophysical characteristics of hydrocarbon systems that cannot be obtained using other elastic-wave modes. Regardless of the difficulties of extracting good-quality SV-SV signal, direct shear waves as well as direct P and converted S energy should be accounted for in 3C seismic studies. Acquisition of full-azimuth seismic data and sampling data at small intervals over long offsets are required for detailed anisotropy analysis. If 3C3D data can be acquired with improved signal-to-noise ratio, more uniform illumination of targets, increased lateral resolution, more accurate amplitude attributes, and better multiple attenuation, such data will have strong interest by the industry. The objectives of this research are: (1) determine the feasibility of extracting direct SV-SV common-mid-point sections from 3-C seismic surveys, (2) improve the exploration for stratigraphic traps by developing systematic relationship between petrophysical properties and combinations of P and S wave modes, (3) create compelling examples illustrating how hydrocarbon-bearing reservoirs in low-permeable rocks (particularly anisotropic shale formations) can be better characterized using different Swave modes (P-SV, SV-SV) in addition to the conventional P

  10. Information Leakage Problem in Efficient Bidirectional Quantum Secure Direct Communication with Single Photons in Both Polarization and Spatial-Mode Degrees of Freedom

    NASA Astrophysics Data System (ADS)

    Liu, Zhi-Hao; Chen, Han-Wu; Liu, Wen-Jie

    2016-06-01

    The information leakage problem in the efficient bidirectional quantum secure direct communication protocol with single photons in both polarization and spatial-mode degrees of freedom is pointed out. Next, a way to revise this protocol to a truly secure one is given. We hope people pay more attention to the information leakage problem in order to design truly secure quantum communication protocols.

  11. "Aspartame: A review of genotoxicity data".

    PubMed

    Kirkland, David; Gatehouse, David

    2015-10-01

    Aspartame is a methyl ester of a dipeptide of aspartic acid and phenylalanine. It is 200× sweeter than sucrose and is approved for use in food products in more than 90 countries around the world. Aspartame has been evaluated for genotoxic effects in microbial, cell culture and animal models, and has been subjected to a number of carcinogenicity studies. The in vitro and in vivo genotoxicity data available on aspartame are considered sufficient for a thorough evaluation. There is no evidence of induction of gene mutations in a series of bacterial mutation tests. There is some evidence of induction of chromosomal damage in vitro, but this may be an indirect consequence of cytotoxicity. The weight of evidence from in vivo bone marrow micronucleus, chromosomal aberration and Comet assays is that aspartame is not genotoxic in somatic cells in vivo. The results of germ cell assays are difficult to evaluate considering limited data available and deviations from standard protocols. The available data therefore support the conclusions of the European Food Safety Authority (EFSA) that aspartame is non-genotoxic. PMID:26321723

  12. Method for protection against genotoxic mutagenesis

    DOEpatents

    Grdina, D.J.

    1996-01-30

    A method and pharmaceutical for protecting against genotoxic damage in irradiated cells are disclosed. Reduction of mutations at the hypoxanthine-guanine phosphoribosyl transferase locus is accomplished by administering an effective dose of a compound having protected sulfhydryl groups which metabolize in vivo to produce both free sulfhydryl groups and disulfides. 10 figs.

  13. ASSESSMENT OF HAZARDOUS WASTES FOR GENOTOXICITY

    EPA Science Inventory

    The authors have evaluated a group of short-term bioassays to identify those that may be suitable for screening large numbers of diverse hazardous industrial wastes for genotoxicity. Fifteen wastes (and dichloromethane extracts of these wastes) from a variety of manufacturing pro...

  14. GENOTOXICITY STUDIES OF BENZ(1)ACEANTHRYLENE

    EPA Science Inventory

    The genotoxicity of the cyclopenta-fused polycyclic aromatic hydrocarbon, benz(1)aceanthrylene (B(1)A),was evaluated in vitro using the L5178Y/T (K sup +/-) mouse lymphoma assay and in vivo using the mouse peripheral blood lymphocyte (PBL) culture system. The mutagenicity and sis...

  15. Method for protection against genotoxic mutagenesis

    DOEpatents

    Grdina, David J.

    1996-01-01

    A method and pharmaceutical for protecting against genotoxic damage in irradiated cells. Reduction of mutations at the hypoxanthine-guanine phosphoribosyl transferase locus is accomplished by administering an effective dose of a compound having protected sulfhydryl groups which metabolize in vivo to produce both free sulfhydryl groups and disulfides.

  16. Ground and Surface Water for Drinking: A Laboratory Study on Genotoxicity Using Plant Tests

    PubMed Central

    Feretti, Donatella; Ceretti, Elisabetta; Gustavino, Bianca; Zerbini, llaria; Zani, Claudia; Monarca, Silvano; Rizzoni, Marco

    2012-01-01

    Surface waters are increasingly utilized for drinking water because groundwater sources are often polluted. Several monitoring studies have detected the presence of mutagenicity in drinking water, especially from surface sources due to the reaction of natural organic matter with disinfectant. The study aimed to investigate the genotoxic potential of the products of reaction between humic substances, which are naturally present in surface water, and three disinfectants: chlorine dioxide, sodium hypochlorite and peracetic acid. Commercial humic acids dissolved in distilled water at different total organic carbon (TOC) concentrations were studied in order to simulate natural conditions of both ground water (TOC=2.5 mg/L) and surface water (TOC=7.5 mg/L). These solutions were treated with the biocides at a 1:1 molar ratio of C:disinfectant and tested for genotoxicity using the anaphase chromosomal aberration and micronucleus tests in Allium cepa, and the Vicia faba and Tradescantia micronucleus tests. The tests were carried out after different times and with different modes of exposure, and at 1:1 and 1:10 dilutions of disinfected and undisinfected humic acid solutions. A genotoxic effect was found for sodium hypochlorite in all plant tests, at both TOCs considered, while chlorine dioxide gave positive results only with the A.cepa tests. Some positive effects were also detected for PAA (A.cepa and Tradescantia). No relevant differences were found in samples with different TOC values. The significant increase in all genotoxicity end-points induced by all tested disinfectants indicates that a genotoxic potential is exerted even in the presence of organic substances at similar concentrations to those frequently present in drinking water. PMID:25170443

  17. Nanoceria have no genotoxic effect on human lens epithelial cells

    NASA Astrophysics Data System (ADS)

    Pierscionek, Barbara K.; Li, Yuebin; Yasseen, Akeel A.; Colhoun, Liza M.; Schachar, Ronald A.; Chen, Wei

    2010-01-01

    There are no treatments for reversing or halting cataract, a disease of the structural proteins in the eye lens, that has associations with other age-related degenerative conditions such as Alzheimer's disease. The incidence of cataract and associated conditions is increasing as the average age of the population rises. Protein folding diseases are difficult to assess in vivo as proteins and their age-related changes are assessed after extraction. Nanotechnology can be used to investigate protein changes in the intact lens as well as for a potential means of drug delivery. Nanoparticles, such as cerium oxide (CeO2) which have antioxidant properties, may even be used as a means of treating cataract directly. Prior to use in treatments, nanoparticle genotoxicity must be tested to assess the extent of any DNA or chromosomal damage. Sister chromatid exchanges were measured and DNA damage investigated using the alkaline COMET assay on cultured human lens epithelial cells, exposed to 5 and 10 µg ml-1 of CeO2 nanoparticles (nanoceria). Nanoceria at these dosages did not cause any DNA damage or significant increases in the number of sister chromatid exchanges. The absence of genotoxic effects on lens cells suggests that nanoceria, in the doses and exposures tested in this study, are not deleterious to the eye lens and have the potential for use in studying structural alterations, in developing non-surgical cataract treatments and in investigating other protein folding diseases.

  18. High-power 880-nm diode-directly-pumped passively mode-locked Nd:YVO₄ laser at 1342 nm with a semiconductor saturable absorber mirror.

    PubMed

    Li, Fang-Qin; Liu, Ke; Han, Lin; Zong, Nan; Bo, Yong; Zhang, Jing-Yuan; Peng, Qin-Jun; Cui, Da-Fu; Xu, Zu-Yan

    2011-04-15

    A high-power 880-nm diode-directly-pumped passively mode-locked 1342 nm Nd:YVO₄ laser was demonstrated with a semiconductor saturable absorber mirror (SESAM). The laser mode radii in the laser crystal and on the SESAM were optimized carefully using the ABCD matrix formalism. An average output power of 2.3 W was obtained with a repetition rate of 76 MHz and a pulse width of 29.2 ps under an absorbed pump power of 12.1 W, corresponding to an optical-optical efficiency of 19.0% and a slope efficiency of 23.9%, respectively. PMID:21499398

  19. Comparative efficacy of two microdoses of a potentized homoeopathic drug, Cadmium Sulphoricum, in reducing genotoxic effects produced by cadmium chloride in mice: a time course study

    PubMed Central

    Datta, Swapna S; Mallick, Palash P; Rahman Khuda-Bukhsh, Anisur AR

    2001-01-01

    Background Cadmium poisoning in the environment has assumed an alarming problem in recent years. Effective antimutagenic agents which can reverse or combat cadmium induced genotoxicity in mice have not yet been reported. Therefore, in the present study, following the homeopathic principle of "like cures like", we tested the efficacy of two potencies of a homeopathic drug, Cadmium Sulphoricum (Cad Sulph), in reducing the genotoxic effects of Cadmium chloride in mice. Another objective was to determine the relative efficacy of three administrative modes, i.e. pre-, post- and combined pre and post-feeding of the homeopathic drugs. For this, healthy mice, Mus musculus, were intraperitoneally injected with 0.008% solution of CdCl2 @ 1 ml/100 gm of body wt (i.e. 0.8 mcg/gm of bw), and assessed for the genotoxic effects through such studies as chromosome aberrations (CA), micronucleated erythrocytes (MNE), mitotic index (MI) and sperm head anomaly (SHA), keeping suitable succussed alcohol fed (positive) and CdCl2 untreated normal (negative) controls. The CdCl2 treated mice were divided into 3 subgroups, which were orally administered with the drug prior to, after and both prior to and after injection of CdCl2 at specific fixation intervals and their genotoxic effects were analyzed. Results While the CA, MNE and SHA were reduced in the drug fed series as compared to their respective controls, the MI showed an apparent increase. The combined pre- and post-feeding of Cad Sulph showed maximum reduction of the genotoxic effects. Conclusions Both Cad Sulph-30 and 200 were able to combat cadmium induced genotoxic effects in mice and that combined pre- and post-feeding mode of administration was found to be most effective in reducing the genotoxic effect of CdCl2 followed by the post-feeding mode. PMID:11737881

  20. In vivo genotoxicity of furan in F344 rats at cancer bioassay doses

    SciTech Connect

    Ding, Wei

    2012-06-01

    Furan, a potent rodent liver carcinogen, is found in many cooked food items and thus represents a human cancer risk. Mechanisms for furan carcinogenicity were investigated in male F344 rats using the in vivo Comet and micronucleus assays, combined with analysis of histopathological and gene expression changes. In addition, formamidopyrimidine DNA glycosylase (Fpg) and endonuclease III (EndoIII)-sensitive DNA damage was monitored as a measure of oxidative DNA damage. Rats were treated by gavage on four consecutive days with 2, 4, and 8 mg/kg bw furan, doses that were tumorigenic in 2-year cancer bioassays, and with two higher doses, 12 and 16 mg/kg. Rats were killed 3 h after the last dose, a time established as producing maximum levels of DNA damage in livers of furan-treated rats. Liver Comet assays indicated that both DNA strand breaks and oxidized purines and pyrimidines increased in a near-linear dose-responsive fashion, with statistically significant increases detected at cancer bioassay doses. No DNA damage was detected in bone marrow, a non-target tissue for cancer, and peripheral blood micronucleus assays were negative. Histopathological evaluation of liver from furan-exposed animals produced evidence of inflammation, single-cell necrosis, apoptosis, and cell proliferation. In addition, genes related to apoptosis, cell-cycle checkpoints, and DNA-repair were expressed at a slightly lower level in the furan-treated livers. Although a mixed mode of action involving direct DNA binding cannot be ruled out, the data suggest that furan induces cancer in rat livers mainly through a secondary genotoxic mechanism involving oxidative stress, accompanied by inflammation, cell proliferation, and toxicity. -- Highlights: ► Furan is a potent rodent liver carcinogen and represents a human cancer risk. ► Furan induces DNA damage in rat liver at cancer bioassay doses. ► Furan induces oxidative stress, inflammation and cell proliferation in rat liver. ► Expression of

  1. Genomic and gene expression responses to genotoxic stress in PAC2 zebrafish embryonic cell line.

    PubMed

    Šrut, Maja; Bourdineaud, Jean-Paul; Štambuk, Anamaria; Klobučar, Göran I V

    2015-11-01

    PAC2 cell line is, along most of the developed zebrafish cell lines, poorly characterized concerning its response to genotoxicants. To define the PAC2 cell line response to different forms of genotoxic stress, we exposed the cells to model genotoxic agents (benzo[a]pyrene, B[a]P, and ethyl methanesulfonate) and subsequently monitored DNA damage and alterations by using the battery of tests, including the Comet assay, quantitative random-amplified polymorphic DNA and amplified fragment length polymorphism. The expression of several DNA repair (xpc, xpd, hr23b, rad51, msh2) and oxidative stress response (sod (Cu/Zn)) genes was monitored as well. To obtain an indication of the PAC2 cell line metabolizing capacity, the expression of genes belonging to cyp1, cyp2 and cyp3 families was assessed upon exposure to B[a]P. Genotoxic responses were observed in all the used methods, and quantitative random-amplified polymorphic DNA and amplified fragment length polymorphism proved to be more sensitive by revealing DNA alterations even when the Comet assay indicated lack of significant damage. The PAC2 cell line demonstrated basal and B[a]P-induced expression of several cyp genes, suggesting its ability to metabolize indirect acting xenobiotics to a certain point. Based on these results, PAC2 cells seem to be sensitive zebrafish in vitro model in the genotoxicity assessment of the direct acting genotoxicant; however, they are less sensitive toward the indirect acting genotoxicant due to their limited metabolizing properties. PMID:25612249

  2. Comet assay evaluation of six chemicals of known genotoxic potential in rats.

    PubMed

    Hobbs, Cheryl A; Recio, Leslie; Streicker, Michael; Boyle, Molly H; Tanaka, Jin; Shiga, Atsushi; Witt, Kristine L

    2015-07-01

    As a part of an international validation of the in vivo rat alkaline comet assay (comet assay) initiated by the Japanese Center for the Validation of Alternative Methods (JaCVAM) we examined six chemicals for potential to induce DNA damage: 2-acetylaminofluorene (2-AAF), N-nitrosodimethylamine (DMN), o-anisidine, 1,2-dimethylhydrazine dihydrochloride (1,2-DMH), sodium chloride, and sodium arsenite. DNA damage was evaluated in the liver and stomach of 7- to 9-week-old male Sprague Dawley rats. Of the five genotoxic carcinogens tested in our laboratory, DMN and 1,2-DMH were positive in the liver and negative in the stomach, 2-AAF and o-anisidine produced an equivocal result in liver and negative results in stomach, and sodium arsenite was negative in both liver and stomach. 1,2-DMH and DMN induced dose-related increases in hedgehogs in the same tissue (liver) that exhibited increased DNA migration. However, no cytotoxicity was indicated by the neutral diffusion assay (assessment of highly fragmented DNA) or histopathology in response to treatment with any of the tested chemicals. Therefore, the increased DNA damage resulting from exposure to DMN and 1,2-DMH was considered to represent a genotoxic response. Sodium chloride, a non-genotoxic non-carcinogen, was negative in both tissues as would be predicted. Although only two (1,2-DMH and DMN) out of five genotoxic carcinogens produced clearly positive results in the comet assay, the results obtained for o-anisidine and sodium arsenite in liver and stomach cells are consistent with the known mode of genotoxicity and tissue specificity exhibited by these carcinogens. In contrast, given the known genotoxic mode-of-action and target organ carcinogenicity of 2-AAF, it is unclear why this chemical failed to convincingly increase DNA migration in the liver. Thus, the results of the comet assay validation studies conducted in our laboratory were considered appropriate for five out of the six test chemicals. PMID:26212309

  3. Comet assay evaluation of six chemicals of known genotoxic potential in rats

    PubMed Central

    Hobbs, Cheryl A.; Recio, Leslie; Streicker, Michael; Boyle, Molly H.; Tanaka, Jin; Shiga, Atsushi; Witt, Kristine L.

    2015-01-01

    As a part of an International validation of the in vivo rat alkaline comet assay (comet assay) initiated by the Japanese Center for the Validation of Alternative Methods (JaCVAM) we examined six chemicals for potential to induce DNA damage: 2-acetylaminofluorene (2-AAF), N-nitrosodimethylamine (DMN), o-anisidine, 1,2-dimethylhydrazine dihydrochloride (1,2-DMH), sodium chloride, and sodium arsenite. DNA damage was evaluated in the liver and stomach of 7- to 9-week-old male Sprague Dawley rats. Of the five genotoxic carcinogens tested in our laboratory, DMN and 1,2-DMH were positive in the liver and negative in the stomach, 2-AAF and o-anisidine produced an equivocal result in liver and negative results in stomach, and sodium arsenite was negative in both liver and stomach. 1,2-DMH and DMN induced dose-related increases in hedgehogs in the same tissue (liver) that exhibited increased DNA migration. However, no cytotoxicity was indicated by the neutral diffusion assay (assessment of highly fragmented DNA) or histopathology in response to treatment with any of the tested chemicals. Therefore, the increased DNA damage resulting from exposure to DMN and 1,2-DMH was considered to represent a genotoxic response. Sodium chloride, a non-genotoxic non-carcinogen, was negative in both tissues as would be predicted. Although only two (1,2-DMH and DMN) out of five genotoxic carcinogens produced clearly positive results in the comet assay, the results obtained for o-anisidine and sodium arsenite in liver and stomach cells are consistent with the known mode of genotoxicity and tissue specificity exhibited by these carcinogens. In contrast, given the known genotoxic mode-of-action and target organ carcinogenicity of 2-AAF, it is unclear why this chemical failed to convincingly increase DNA migration in the liver. Thus, the results of the comet assay validation studies conducted in our laboratory were considered appropriate for five out of the six test chemicals. PMID:26212309

  4. Development of a Quantitative Model Incorporating Key Events in a Hepatoxic Mode of Action to Predict Tumor Incidence

    EPA Science Inventory

    Biologically-Based Dose Response (BBDR) modeling of environmental pollutants can be utilized to inform the mode of action (MOA) by which compounds elicit adverse health effects. Chemicals that produce tumors are typically described as either genotoxic or non-genotoxic. One common...

  5. Production of multicharged ions and behavior of microwave modes in an electron cyclotron resonance ion source directly excited in a circular cavity resonator

    SciTech Connect

    Kato, Yushi; Furuki, Hideyuki; Asaji, Toyohisa; Sato, Fuminobu; Iida, Toshiyuki

    2006-03-15

    Electron cyclotron resonance ion sources (ECRIS) have been widely used for production of high-intensity multicharged ion beams. Making good use of microwave modes is proposed for enhancing the efficiency of ECR for production of multicharged ions (TAIKO II). We can assign the peak position of the electric field of the standing waves to the ECR zone in the directly excited cavity resonator, i.e., the vacuum chamber with the fixed and the mobile plates for selecting and tuning the modes. Periodicity of the extracted multicharged ion currents and plasma parameters is observed as the position of the mobile plate moves. We measure the intensity of the electric field in the ECR plasma by using the insulated semidipole probe and the standing waves are observed. The correlation between the production of multicharged ions and the microwave modes is clarified by measuring the electric field and plasma parameters in the circular cavity resonator.

  6. Mutagenic and Genotoxic Effect of Hydroxyurea

    PubMed Central

    Santos, Jean L.; Bosquesi, Priscila L.; Almeida, Adélia E.; Chin, Chung Man; Varanda, Eliana A.

    2011-01-01

    The hydroxyurea, a cytotoxic drug, is the mainly available therapeutical strategy for the treatment of sickle cell disease. This study aimed to evaluate the mutagenic and genotoxic potential of the hydroxyurea through the Salmonella/Microsome assay and micronucleus test in peripheral blood of mice. The doses were evaluated at 29.25-468 μmol/plate in Salmonella/Microsome assay in presence and absence of metabolic activation the drug. In the micronucleus test the doses were evaluated at 12.5; 25; 50; 75 and 100 mg/kg. The results show that hydroxyurea present mutagenic activity in TA98 and TA100 in doses above 117 μmol/plate and 234 μmol/plate respectively. The drug induced a significant increase in the frequency of micronuclei in reticulocytes of mice at concentrations of 50, 75 and 100 mg/kg, compared to negative control (water). These results demonstrated the mutagenic and genotoxic potential of hydroxyurea. PMID:23675245

  7. Electrochemical Genotoxicity Assay Based on a SOS/umu Test Using Hydrodynamic Voltammetry in a Droplet

    PubMed Central

    Kuramitz, Hideki; Sazawa, Kazuto; Nanayama, Yasuaki; Hata, Noriko; Taguchi, Shigeru; Sugawara, Kazuharu; Fukushima, Masami

    2012-01-01

    The SOS/umu genotoxicity assay evaluates the primary DNA damage caused by chemicals from the β-galactosidase activity of S. typhimurium. One of the weaknesses of the common umu test system based on spectrophotometric detection is that it is unable to measure samples containing a high concentration of colored dissolved organic matters, sediment, and suspended solids. However, umu tests with electrochemical detection techniques prove to be a better strategy because it causes less interference, enables the analysis of turbid samples and allows detection even in small volumes without loss of sensitivity. Based on this understanding, we aim to develop a new umu test system with hydrodynamic chronoamperometry using a rotating disk electrode (RDE) in a microliter droplet. PAPG when used as a substrate is not electroactive at the potential at which PAP is oxidized to p-quinone imine (PQI), so the current response of chronoamperometry resulting from the oxidation of PAP to PQI is directly proportional to the enzymatic activity of S. typhimurium. This was achieved by performing genotoxicity tests for 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide (AF-2) and 2-aminoanthracene (2-AA) as model genotoxic compounds. The results obtained in this study indicated that the signal detection in the genotoxicity assay based on hydrodynamic voltammetry was less influenced by the presence of colored components and sediment particles in the samples when compared to the usual colorimetric signal detection. The influence caused by the presence of humic acids (HAs) and artificial sediment on the genotoxic property of selected model compounds such as 4-nitroquinoline-N-oxide (4-NQO), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), 1,8-dinitropyrene (1,8-DNP) and 1-nitropyrene (1-NP) were also investigated. The results showed that the genotoxicity of 1-NP and MX changed in the presence of 10 mg·L−1 HAs. The genotoxicity of tested chemicals with a high hydrophobicity such as 1,8-DNP

  8. The potential for new methods to assess human reproductive genotoxicity

    SciTech Connect

    Mendelsohn, M.L.

    1987-09-01

    The immediate prospects are not good for practical methods for measuring the human heritable mutation rate. The methods discussed here range from speculative to impractical, and at best are sensitive enough only for large numbers of subjects. Given the rapid development of DNA methods and the current status of two-dimensional gel electrophoresis, there is some hope that the intermediate prospects may be better. In contrast, the prospects for useful cellular-based male germinal methods seem more promising and immediate. Effective specific locus methods for sperm are already conceivable and may be practical in a few years. Obviously such methods will not predict heritable effects definitively, but they will provide direct information on reproductive genotoxicity and should contribute significantly to many current medical and environmental situations where genetic damage is suspected. 22 refs.

  9. Genotoxic assessment of environmental tobacco smoke using bacterial bioassays

    SciTech Connect

    Claxton, L.D.; Morin, R.S.; Hughes, T.J.; Lewtas, J.

    1989-01-01

    The paper demonstrates that integrated chemical and bacterial mutagenicity information can be used to identify environmental tobacco smoke genotoxicants, monitor human exposure, and make comparative assessments. Approximately one-third of the environmental tobacco-smoke constituents for which there is quantitative analytical-chemistry information also have associated genotoxicity information. For example, 11 of the quantitated compounds are animal carcinogens. Work presented in this paper demonstrates that both the nonparticle-bound semi-volatile and the particulate-bound organic material contain bacterial mutagens. These environmental tobacco-smoke organics give an equivalent of about 86,000 revertants per cigarette. In addition, this article summarizes efforts to estimate environmental tobacco smoke bacterial mutagenicity, to use bacterial tests for the monitoring of environmental tobacco smoke-impacted indoor environments, and to use bacterial assays for the direct monitoring of human exposure.

  10. Metabolism, genotoxicity, and carcinogenicity of comfrey.

    PubMed

    Mei, Nan; Guo, Lei; Fu, Peter P; Fuscoe, James C; Luan, Yang; Chen, Tao

    2010-10-01

    Comfrey has been consumed by humans as a vegetable and a tea and used as an herbal medicine for more than 2000 years. Comfrey, however, produces hepatotoxicity in livestock and humans and carcinogenicity in experimental animals. Comfrey contains as many as 14 pyrrolizidine alkaloids (PA), including 7-acetylintermedine, 7-acetyllycopsamine, echimidine, intermedine, lasiocarpine, lycopsamine, myoscorpine, symlandine, symphytine, and symviridine. The mechanisms underlying comfrey-induced genotoxicity and carcinogenicity are still not fully understood. The available evidence suggests that the active metabolites of PA in comfrey interact with DNA in liver endothelial cells and hepatocytes, resulting in DNA damage, mutation induction, and cancer development. Genotoxicities attributed to comfrey and riddelliine (a representative genotoxic PA and a proven rodent mutagen and carcinogen) are discussed in this review. Both of these compounds induced similar profiles of 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP)-derived DNA adducts and similar mutation spectra. Further, the two agents share common mechanisms of drug metabolism and carcinogenesis. Overall, comfrey is mutagenic in liver, and PA contained in comfrey appear to be responsible for comfrey-induced toxicity and tumor induction. PMID:21170807

  11. Genotoxicity assessment in patients with thalassemia minor.

    PubMed

    Al-Sweedan, Suleimman A; Khabour, Omar; Isam, Ruba

    2012-05-15

    Thalassemia is an inherited blood disorder that affects both genders and results in reduced synthesis of hemoglobin, and thus causing anemia. Previous studies have shown that the severe form of this disease, thalassemia major, is associated with genotoxicity. This includes increases in the level of sister chromatid exchange (SCEs), chromosomal aberrations (CAs) and micronuclei. In this study, we assessed genotoxicity in the lymphocytes of thalassemia minor subjects using sister chromatid exchange (SCE) and chromosomal aberration (CA) assays. In addition, we investigated the level of oxidative DNA damage by measuring 8-hydroxy-2'-deoxyguanosine (8OHdG) biomarker in urine samples. Eighteen thalassemia minor subjects and eighteen matched normal healthy controls were volunteered in the study. In addition, seven thalassemia major patients were recruited as positive controls. The results showed increases in the frequency of SCEs (P<0.05) in thalassemia minor compared to healthy controls. However, no difference in CAs frequency was detected between thalassemia minor and controls (P>0.05). Both SECs and CAs in thalassemia major patients were significantly higher compared to other groups (P<0.05). Regarding urine 8OHdG levels, the result showed a slight increase in thalassemia minor compared to healthy controls but the difference was not significant (P>0.05). In conclusion, our results showed that thalassemia minor is associated with genotoxicity to blood lymphocytes as indicated by SCEs assay. PMID:22414564

  12. Cytotoxicity and genotoxicity of biogenic silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Lima, R.; Feitosa, L. O.; Ballottin, D.; Marcato, P. D.; Tasic, L.; Durán, N.

    2013-04-01

    Biogenic silver nanoparticles with 40.3 ± 3.5 nm size and negative surface charge (- 40 mV) were prepared with Fusarium oxysporum. The cytotoxicity of 3T3 cell and human lymphocyte were studied by a TaliTM image-based cytometer and the genotoxicity through Allium cepa and comet assay. The results of BioAg-w (washed) and BioAg-nw (unwashed) biogenic silver nanoparticles showed cytotoxicity exceeding 50 μg/mL with no significant differences of response in 5 and 10 μg/mL regarding viability. Results of genotoxicity at concentrations 5.0 and 10.0 ug/mL show some response, but at concentrations 0.5 and 1.0 μg/mL the washed and unwashed silver nanoparticles did not present any effect. This in an important result since in tests with different bacteria species and strains, including resistant, MIC (minimal inhibitory concentration) had good answers at concentrations less than 1.9 μg/mL. This work concludes that biogenic silver nanoparticles may be a promising option for antimicrobial use in the range where no cyto or genotoxic effect were observed. Furthermore, human cells were found to have a greater resistance to the toxic effects of silver nanoparticles in comparison with other cells.

  13. Anti-genotoxic hydrazide from Crinum defixum.

    PubMed

    Bordoloi, Manobjyoti; Kotoky, Rumi; Mahanta, Jiban J; Sarma, Tarun C; Kanjilal, Purnendu B

    2009-06-01

    Crinum defixum Ker-Gawl popularly known as Bon-naharu (meaning wild garlic) in Assam. It is found abundantly growing wild on riverbanks of Dhansiri River in Golaghat District of Assam. It is used as ethnomedicine in this part of India for a number of ailments. Bioassay guided chemical investigation of the bulbs of Crinum defixum Ker-Gawl afforded to isolate a new hydrazide derivative and its structure was determined as (E)-N'-[(E)-2-butenoyl]-2-butenoylhydrazide by spectroscopic methods. The compound was assayed for anti-genotoxic activity by onion root tip assay (by observing different types of chromosomal aberrations such as chromosomal bridges, stickiness, delayed anaphase, polyploidy and vagrant chromosome). The phyto-compound was found to have anti-genotoxic activity and imparted a clear dose dependent protective effect against the genotoxic effect of H(2)O(2). Further, the compound seems to be more effective against clastogenic aberrations than physiological aberration at the highest concentration used (250 ppm). PMID:18995928

  14. Genotoxicity of radiofrequency radiation. DNA/Genetox Expert Panel.

    PubMed

    Brusick, D; Albertini, R; McRee, D; Peterson, D; Williams, G; Hanawalt, P; Preston, J

    1998-01-01

    During the past several years, concerns have been raised regarding the potential adverse effects of exposures to nonionizing radiation, particularly in the extremely low frequency (ELF) range (50 to 60 MHz) and radiofrequency radiation (RFR) with frequencies ranging from 30 KHz to 30,000 MHz. One focus of concern has been potential DNA interactions. Publications reviewing the genotoxicity of ELF radiation [McCann et al. (1993): Mutat Res 297(1):61-95; Murphy et al. (1993): Mutat Res 296:221-240; NAS (1997)], have been uniform in concluding that the weight of evidence does not indicate any genotoxic risk from exposure to this type of radiation. Concern that RFR may be associated with adverse biological effects [WHO, 1993], including recent allegations that they may be involved in the production of brain tumors in humans [Elmer-Dewit (1993): Time, February 8:42], has resulted in the production of a large number of publications describing the effects of RFR on the integrity of nucleic acids. Data from studies conducted in a frequency range from 800 to 3,000 MHz were reviewed and subjected to a weight-of-evidence evaluation. The evaluation focused on direct toxicological effects of RFR as well as on studies addressing basic biological responses to RFR at the cellular and molecular level. The data from over 100 studies suggest that RFR is not directly mutagenic and that adverse effects from exposure of organisms to high frequencies and high power intensities of RFR are predominantly the result of hyperthermia; however, there may be some subtle indirect effects on the replication and/or transcription of genes under relatively restricted exposure conditions. PMID:9707093

  15. A predictive toxicogenomics signature to classify genotoxic versus non-genotoxic chemicals in human TK6 cells

    PubMed Central

    Williams, Andrew; Buick, Julie K.; Moffat, Ivy; Swartz, Carol D.; Recio, Leslie; Hyduke, Daniel R.; Li, Heng-Hong; Fornace, Albert J.; Aubrecht, Jiri; Yauk, Carole L.

    2015-01-01

    Genotoxicity testing is a critical component of chemical assessment. The use of integrated approaches in genetic toxicology, including the incorporation of gene expression data to determine the DNA damage response pathways involved in response, is becoming more common. In companion papers previously published in Environmental and Molecular Mutagenesis, Li et al. (2015) [6] developed a dose optimization protocol that was based on evaluating expression changes in several well-characterized stress-response genes using quantitative real-time PCR in human lymphoblastoid TK6 cells in culture. This optimization approach was applied to the analysis of TK6 cells exposed to one of 14 genotoxic or 14 non-genotoxic agents, with sampling 4 h post-exposure. Microarray-based transcriptomic analyses were then used to develop a classifier for genotoxicity using the nearest shrunken centroids method. A panel of 65 genes was identified that could accurately classify toxicants as genotoxic or non-genotoxic. In Buick et al. (2015) [1], the utility of the biomarker for chemicals that require metabolic activation was evaluated. In this study, TK6 cells were exposed to increasing doses of four chemicals (two genotoxic that require metabolic activation and two non-genotoxic chemicals) in the presence of rat liver S9 to demonstrate that S9 does not impair the ability to classify genotoxicity using this genomic biomarker in TK6cells. PMID:26425668

  16. Development of an automated dual-mode supercritical fluid chromatography and reversed-phase liquid chromatography mass-directed purification system for small-molecule drug discovery.

    PubMed

    Hettiarachchi, Kanaka; Kong, May; Yun, Andersen; Jacobsen, John R; Xue, Qifeng

    2014-04-01

    We report the development of a dual-mode mass-directed supercritical fluid chromatography and reversed-phase liquid chromatography purification system. The addition of a third pump allows for flexible mobile phase control between the two techniques, and enables operation of either chromatography mode within minutes by activation of a set of switching valves on a single system. Software control, fluidic pathways, interface to the mass spectrometer, and fraction collection have been modified for compatibility between both separation methods. The conditioning solvent and tuning parameters for the mass spectrometer were adjusted to achieve an ideal signal trace in either mode with good linearity (r(2) > 0.970) over a range of concentrations and minimal noise for accurate peak detection and isolation. The registration success rate is 90% and overall sample recovery for either technique is 80-90%. Combining two orthogonal separation and purification modes in one single system has improved the purification throughput of complex mixtures and has been a valuable, cost-saving tool in our laboratory. PMID:24470330

  17. Genotoxicity testing: moving beyond qualitative "screen and bin" approach towards characterization of dose-response and thresholds.

    PubMed

    Pottenger, Lynn H; Gollapudi, B Bhaskar

    2010-01-01

    For more than 40+ years, genotoxicity data have been interpreted in a qualitative, binary mode; a chemical is considered either positive or negative for a response in the test system. Although dose-response information is sometimes used in this decision, it is not routine to obtain the amount of information needed to inform risk assessment, for example to determine no-observed-genotoxic-effect-levels, primarily due to the historical view of genotoxic responses as "linear, no-threshold." Only recently have researchers begun to address this issue through robust experimental designs and application of statistical models. A growing body-of-evidence supports the existence of response thresholds for a number of mutagenic agents, in vitro and in vivo. Clearly, simple observation of a "hockey-stick" dose-response curve is not sufficient to establish a threshold. Collection of robust empirical data must be supported with an analysis of biological plausibility for the observed threshold. In this context, a chemical-specific mode-of-action (MOA) approach, which identifies key events responsible for the observed mutagenic effect, is extremely valuable. Biomarkers of key events, providing qualitative and quantitative information, can be integrated in a weight-of-evidence-based assessment of genotoxicity data from multiple test systems and used to identify data gaps to resolve/reduce uncertainties during the risk assessment process. To this end, specific recommendations on study design and data analysis are proposed. As the Environmental Mutagen Society celebrates its 40th anniversary, the field of genetic toxicology is marking a milestone on the path to a new paradigm, using a MOA, data-driven approach to answer questions about thresholds for genotoxic agents. PMID:20806283

  18. Direct measurement of loop gain and bandwidth of phase-locked loop for mode-locked laser.

    PubMed

    Hou, Dong; Tian, Jie; Sun, Fuyu; Huang, Xianhe

    2016-07-25

    A simple and robust technique for measuring the loop gain and bandwidth of a phase-locking loop (PLL) for mode-locked laser is proposed. This technique can be used for the real-time measurement of the PLL's real loop gain and bandwidth in a closed loop without breaking its locking state. The agreement of the experimental result and theoretical calculation proves the validity of the proposed technique for measuring the loop gain and bandwidth. This technique with a simple configuration can be easily expanded to other laser's locking system whose loop gain and bandwidth should be measured in advance. PMID:27464173

  19. Genotoxicity biomarkers for airborne particulate matter (PM2.5) in an area under petrochemical influence.

    PubMed

    Lemos, Andréia Torres; Lemos, Clarice Torres de; Flores, Andressa Negreiros; Pantoja, Eduarda Ozório; Rocha, Jocelita Aparecida Vaz; Vargas, Vera Maria Ferrão

    2016-09-01

    The effects of fine inhalable particles (PM2.5) were evaluated in an area under the influence of a petrochemical industry, investigating the sensitivity of different genotoxicity biomarkers. Organic extracts were obtained from PM2.5 samples at two sites, positioned in the first and second preferential wind direction in the area. The extracts were evaluated with Salmonella/microsome assay, microsuspension method, strains TA98, YG1021 and YG1024. The mammalian metabolization fraction (S9) was used to evaluate metabolite mutagenicity. The Comet Assay (CA) and Micronuclei Test were used in a Chinese hamster lung cell line (V79). All extracts showed mutagenicity in Salmonella, and nitrogenated compounds were strongly present. Genotoxicity were found in CA in almost all extracts and the micronuclei induction at the Site in the first (Autumn 1, Winter 1), and in the second (Spring 2) wind direction. V79 showed cytotoxicity in all samples. The three biomarkers were concordant in characterization Site NO with worse quality, compatible with the greater pollutants dispersion in the first wind direction. All PM2.5 concentrations were lower than those recommended by air quality standards but genotoxic effects were detected in all samples, corroborating that these standards are inadequate as quality indicators. The Salmonella/microsome assay proved sensitive to PM2.5 mutagenicity, with an outstanding influence of nitroarenes and aromatic amines. Analyses using CA and the micronucleus test broadened the levels of response that involve different damage induction mechanisms. Results show that the complex PM2.5 composition can provoke various genotoxic effects and the use of different bioassays is essential to understand its effects. PMID:27343868

  20. Cytotoxicity and genotoxicity of urban particulate matter in mammalian cells

    PubMed Central

    Dumax-Vorzet, Audrey F.; Tate, M.; Walmsley, Richard; Elder, Rhod H.; Povey, Andrew C.

    2015-01-01

    Ambient air particulate matter (PM)-associated reactive oxygen species (ROS) have been linked to a variety of altered cellular outcomes. In this study, three different PM samples from diesel exhaust particles (DEPs), urban dust standard reference material SRM1649a and air collected in Manchester have been tested for their ability to oxidise DNA in a cell-free assay, to increase intracellular ROS levels and to induce CYP1A1 gene expression in mammalian cells. In addition, the cytotoxicity and genotoxicity of PM were assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and alkaline comet assay, respectively. All PM samples catalysed the Fenton reaction in a cell-free assay, but only DEP resulted in the generation of ROS as measured by dichlorodihydrofluorescein diacetate oxidation in mammalian cells. However, there was no evidence that increased ROS was a consequence of polycyclic aromatic hydrocarbon metabolism via CYP1A1 induction as urban dust, the Manchester dust samples but not DEP-induced CYP1A1 expression. Urban dust was more cytotoxic in murine embryonic fibroblasts (MEFs) than the other PM samples and also induced expression of GADD45a in the GreenScreen Human Cell assay without S9 activation suggesting the presence of a direct-acting genotoxicant. Urban dust and DEP produced comparable levels of DNA damage, as assessed by the alkaline comet assay, in MEFs at higher levels than those induced by Manchester PM. In conclusion, results from the cytotoxic and genotoxic assays are not consistent with ROS production being the sole determinant of PM-induced toxicity. This suggests that the organic component can contribute significantly to this toxicity and that further work is required to better characterise the extent to which ROS and organic components contribute to PM-induced toxicity. PMID:26113525

  1. Compact diode-directly-pumped passively mode-locked TEM00 Nd:GdVO4 laser at 1341 nm using a semiconductor saturable absorber mirror

    NASA Astrophysics Data System (ADS)

    Liu, K.; Li, F. Q.; Liu, Y.; Cao, D.; Bo, Y.; Peng, Q. J.; Cui, D. F.; Zhang, J. Y.; Xu, Z. Y.

    2011-11-01

    We report on a compact 880-nm diode-directly-pumped passively mode-locked TEM00 Nd:GdVO4 laser at 1341 nm with a semiconductor saturable absorber mirror (SESAM) for the first time. Under the absorbed pump power of 14.6 W, the maximum output power of 1.27 W was obtained at the repetition rate of 85.3 MHz with the pulse width of 45.3 ps, corresponding to an optical-optical efficiency of 8.8% and the slope efficiency of 33.3%, respectively. The beam quality factor was measured to be M 2 = 1.18, indicating a TEM00 mode.

  2. High-power diode-directly-pumped tenth-order harmonic mode-locked TEM00 Nd:YVO4 laser with 1 GHz repetition rate

    NASA Astrophysics Data System (ADS)

    Li, F.-Q.; Zong, N.; Han, L.; Tian, C.-Y.; Bo, Y.; Peng, Q.-J.; Cui, D.-F.; Xu, Z.-Y.

    2011-02-01

    A high-efficiency high-power diode-directly-pumped tenth-order harmonic mode-locked TEM00 Nd:YVO4 laser with 1 GHz repetition rate was first demonstrated. The maximum output power was 10.4 W with optical-optical efficiency of 41.8% and slope efficiency of 78.1%, respectively, the pulse width was about 30 ps at the output power of 9.6 W. Based on the large third-order nonlinearity of Nd:YVO4, the tenth-order harmonic mode-locked pulses were induced by the intensity-dependent Kerr effect and the cooperative action of counter-propagating pulses colliding in the laser crystal for a colliding-pulse-modelocking-like cavity. The pulses were further modulated by a semiconductor saturable absorber mirror.

  3. Promising anticancer activity of a lichen, Parmelia sulcata Taylor, against breast cancer cell lines and genotoxic effect on human lymphocytes.

    PubMed

    Ari, Ferda; Ulukaya, Engin; Oran, Seyhan; Celikler, Serap; Ozturk, Sule; Ozel, Mustafa Zafer

    2015-05-01

    Plants are still to be explored for new anti-cancer compounds because overall success in cancer treatment is still not satisfactory. As a new possible source for such compounds, the lichens are recently taking a great attention. We, therefore, explored both the genotoxic and anti-growth properties of lichen species Parmelia sulcata Taylor. The chemical composition of P. sulcata was analyzed with comprehensive gas chromatography-time of flight mass spectrometry. Anti-growth effect was tested in human breast cancer cell lines (MCF-7 and MDA-MB-231) by the MTT and ATP viability assays, while the genotoxic activity was studied by assays for micronucleus, chromosomal aberration and DNA fragmentation in human lymphocytes culture. Cell death modes (apoptosis/necrosis) were morphologically assessed. P. sulcata inhibited the growth in a dose-dependent manner up to a dose of 100 μg/ml and induced caspase-independent apoptosis. It also showed genotoxic activity at doses (>125 μg/ml) higher than that required for apoptosis. These results suggest that P. sulcata may induce caspase-independent apoptotic cell death at lower doses, while it may be genotoxic at relatively higher doses. PMID:24676908

  4. Evaluation of toxicity and genotoxicity of 2-chlorophenol on bacteria, fish and human cells.

    PubMed

    Vlastos, Dimitris; Antonopoulou, Maria; Konstantinou, Ioannis

    2016-05-01

    Due to the extensive use of chlorophenols (CPs) in anthropogenic activities, 2-Chlorophenol (2-CP), among other CPs, can enter aquatic ecosystems and can be harmful to a variety of organisms, including bacteria, fish and humans, that are exposed directly and/or indirectly to such contaminated environments. Based on the existing knowledge and in order to move a step forward, the purpose of this study is to investigate the toxic and mainly the genotoxic effects of 2-CP using a combination of bioassays. The tests include the marine bacterium Vibrio fischeri and micronuclei induction in the erythrocytes of Carassius auratus as well as in cultured human lymphocytes. The results obtained reveal that 2-CP is able to induce dose-dependent toxic and genotoxic effects on the selected tested concentrations under the specific experimental conditions. PMID:26897408

  5. Evaluation of the genotoxicity of cellulose nanofibers

    PubMed Central

    de Lima, Renata; Feitosa, Leandro Oliveira; Maruyama, Cintia Rodrigues; Barga, Mariana Abreu; Yamawaki, Patrícia Cristina; Vieira, Isolda Jesus; Teixeira, Eliangela M; Corrêa, Ana Carolina; Mattoso, Luiz Henrique Caparelli; Fraceto, Leonardo Fernandes

    2012-01-01

    Background Agricultural products and by products provide the primary materials for a variety of technological applications in diverse industrial sectors. Agro-industrial wastes, such as cotton and curaua fibers, are used to prepare nanofibers for use in thermoplastic films, where they are combined with polymeric matrices, and in biomedical applications such as tissue engineering, amongst other applications. The development of products containing nanofibers offers a promising alternative for the use of agricultural products, adding value to the chains of production. However, the emergence of new nanotechnological products demands that their risks to human health and the environment be evaluated. This has resulted in the creation of the new area of nanotoxicology, which addresses the toxicological aspects of these materials. Purpose and methods Contributing to these developments, the present work involved a genotoxicological study of different nanofibers, employing chromosomal aberration and comet assays, as well as cytogenetic and molecular analyses, to obtain preliminary information concerning nanofiber safety. The methodology consisted of exposure of Allium cepa roots, and animal cell cultures (lymphocytes and fibroblasts), to different types of nanofibers. Negative controls, without nanofibers present in the medium, were used for comparison. Results The nanofibers induced different responses according to the cell type used. In plant cells, the most genotoxic nanofibers were those derived from green, white, and brown cotton, and curaua, while genotoxicity in animal cells was observed using nanofibers from brown cotton and curaua. An important finding was that ruby cotton nanofibers did not cause any significant DNA breaks in the cell types employed. Conclusion This work demonstrates the feasibility of determining the genotoxic potential of nanofibers derived from plant cellulose to obtain information vital both for the future usage of these materials in

  6. Direct observation of the core/double-shell architecture of intense dual-mode luminescent tetragonal bipyramidal nanophosphors.

    PubMed

    Kim, Su Yeon; Jeong, Jong Seok; Mkhoyan, K Andre; Jang, Ho Seong

    2016-05-21

    Highly efficient downconversion (DC) green-emitting LiYF4:Ce,Tb nanophosphors have been synthesized for bright dual-mode upconversion (UC) and DC green-emitting core/double-shell (C/D-S) nanophosphors-Li(Gd,Y)F4:Yb(18%),Er(2%)/LiYF4:Ce(15%),Tb(15%)/LiYF4-and the C/D-S structure has been proved by extensive scanning transmission electron microscopy (STEM) analysis. Colloidal LiYF4:Ce,Tb nanophosphors with a tetragonal bipyramidal shape are synthesized for the first time and they show intense DC green light via energy transfer from Ce(3+) to Tb(3+) under illumination with ultraviolet (UV) light. The LiYF4:Ce,Tb nanophosphors show 65 times higher photoluminescence intensity than LiYF4:Tb nanophosphors under illumination with UV light and the LiYF4:Ce,Tb is adapted into a luminescent shell of the tetragonal bipyramidal C/D-S nanophosphors. The formation of the DC shell on the core significantly enhances UC luminescence from the UC core under irradiation of near infrared light and concurrently generates DC luminescence from the core/shell nanophosphors under UV light. Coating with an inert inorganic shell further enhances the UC-DC dual-mode luminescence by suppressing the surface quenching effect. The C/D-S nanophosphors show 3.8% UC quantum efficiency (QE) at 239 W cm(-2) and 73.0 ± 0.1% DC QE. The designed C/D-S architecture in tetragonal bipyramidal nanophosphors is rigorously verified by an energy dispersive X-ray spectroscopy (EDX) analysis, with the assistance of line profile simulation, using an aberration-corrected scanning transmission electron microscope equipped with a high-efficiency EDX. The feasibility of these C/D-S nanophosphors for transparent display devices is also considered. PMID:26729043

  7. Genotoxicity of Anesthetics Evaluated In Vivo (Animals)

    PubMed Central

    Braz, Mariana G.; Karahalil, Bensu

    2015-01-01

    The anesthesia has been improved all over the years. However, it can have impact on health, in both patients and animals anesthetized, as well as professionals exposed to inhaled anesthetics. There is continuing effort to understand the possible effects of anesthetics at molecular levels. Knowing the effects of anesthetic agents on genetic material could be a valuable basic support to better understand the possible mechanisms of these agents. Thus, the purpose of this review is to provide an overview on the genotoxic potential, evaluated in animal models, of many anesthetics that have already been used and those currently used in anesthesia. PMID:26199936

  8. Information Leakage in Efficient Bidirectional Quantum Secure Direct Communication with Single Photons in Both Polarization and Spatial-Mode Degrees of Freedom

    NASA Astrophysics Data System (ADS)

    Zhang, Cai; Situ, Haozhen

    2016-06-01

    Recently, Wang et al. presented a bidirectional quantum secure direct communication protocol with single photons in both polarization and spatial-mode degrees of freedom (Int. J. Theor. Phys. 54(10): 3443-3453, 2015). They claimed that their protocol was efficient and removed the drawback of information leakage. However, we found that the information leakage actually exists in their protocol. In this paper, we analyze Wang et al.'s protocol in detail. In addition, we propose an improvement to avoid the information leakage. The security of the improved protocol has also been discussed.

  9. Direct observation of the core/double-shell architecture of intense dual-mode luminescent tetragonal bipyramidal nanophosphors

    NASA Astrophysics Data System (ADS)

    Kim, Su Yeon; Jeong, Jong Seok; Mkhoyan, K. Andre; Jang, Ho Seong

    2016-05-01

    Highly efficient downconversion (DC) green-emitting LiYF4:Ce,Tb nanophosphors have been synthesized for bright dual-mode upconversion (UC) and DC green-emitting core/double-shell (C/D-S) nanophosphors--Li(Gd,Y)F4:Yb(18%),Er(2%)/LiYF4:Ce(15%),Tb(15%)/LiYF4--and the C/D-S structure has been proved by extensive scanning transmission electron microscopy (STEM) analysis. Colloidal LiYF4:Ce,Tb nanophosphors with a tetragonal bipyramidal shape are synthesized for the first time and they show intense DC green light via energy transfer from Ce3+ to Tb3+ under illumination with ultraviolet (UV) light. The LiYF4:Ce,Tb nanophosphors show 65 times higher photoluminescence intensity than LiYF4:Tb nanophosphors under illumination with UV light and the LiYF4:Ce,Tb is adapted into a luminescent shell of the tetragonal bipyramidal C/D-S nanophosphors. The formation of the DC shell on the core significantly enhances UC luminescence from the UC core under irradiation of near infrared light and concurrently generates DC luminescence from the core/shell nanophosphors under UV light. Coating with an inert inorganic shell further enhances the UC-DC dual-mode luminescence by suppressing the surface quenching effect. The C/D-S nanophosphors show 3.8% UC quantum efficiency (QE) at 239 W cm-2 and 73.0 +/- 0.1% DC QE. The designed C/D-S architecture in tetragonal bipyramidal nanophosphors is rigorously verified by an energy dispersive X-ray spectroscopy (EDX) analysis, with the assistance of line profile simulation, using an aberration-corrected scanning transmission electron microscope equipped with a high-efficiency EDX. The feasibility of these C/D-S nanophosphors for transparent display devices is also considered.Highly efficient downconversion (DC) green-emitting LiYF4:Ce,Tb nanophosphors have been synthesized for bright dual-mode upconversion (UC) and DC green-emitting core/double-shell (C/D-S) nanophosphors--Li(Gd,Y)F4:Yb(18%),Er(2%)/LiYF4:Ce(15%),Tb(15%)/LiYF4--and the C/D-S structure

  10. Identification of the set of genes, including nonannotated morA, under the direct control of ModE in Escherichia coli.

    PubMed

    Kurata, Tatsuaki; Katayama, Akira; Hiramatsu, Masakazu; Kiguchi, Yuya; Takeuchi, Masamitsu; Watanabe, Tomoyuki; Ogasawara, Hiroshi; Ishihama, Akira; Yamamoto, Kaneyoshi

    2013-10-01

    ModE is the molybdate-sensing transcription regulator that controls the expression of genes related to molybdate homeostasis in Escherichia coli. ModE is activated by binding molybdate and acts as both an activator and a repressor. By genomic systematic evolution of ligands by exponential enrichment (SELEX) screening and promoter reporter assays, we have identified a total of nine operons, including the hitherto identified modA, moaA, dmsA, and napF operons, of which six were activated by ModE and three were repressed. In addition, two promoters were newly identified and direct transcription of novel genes, referred to as morA and morB, located on antisense strands of yghW and torY, respectively. The morA gene encodes a short peptide, MorA, with an unusual initiation codon. Surprisingly, overexpression of the morA 5' untranslated region exhibited an inhibitory influence on colony formation of E. coli K-12. PMID:23913318

  11. Non-linear infrared spectroscopy of the water bending mode: Direct experimental evidence of hydration shell reorganization?

    PubMed Central

    Chuntonov, Lev; Kumar, Revati

    2014-01-01

    The structure and dynamics of liquid water are further studied by investigating the bend vibrational mode of HDO/D2O and pure H2O via two-dimensional infrared spectroscopy (2D-IR) and linear absorption. The experimental findings and theoretical calculations support a picture in which the HDO bend is localized and the H2O bend is delocalized. The HDO and H2O bends present a loss of the frequency-frequency correlation in subpicosecond time scale. While the loss of correlation for the H2O bend is likely to be associated with the vibrational dynamics of a delocalized transition, the loss of the correlation in the localized HDO bend appears to arise from the fluctuations/rearrangements of the local environment. Interestingly, analysis of the HDO 2D-IR spectra shows the presence of multiple overlapping inhomogeneous distributions of frequencies that interchange in a few picoseconds. Theoretical calculations allow us to propose an atomistic model of the observed vibrational dynamics in which the different in homogeneous distributions and their interchange are assigned to water molecules with different hydrogen-bond states undergoing chemical exchange. The frequency shifts as well as the concentration of the water molecules with single and double hydrogen-bonds as donors derived from the theory are in good agreement with our experimental findings. PMID:24871901

  12. In situ assessment of genotoxicity using caged freshwater mussels

    SciTech Connect

    Black, M.C.; Westerfield, S.M.

    1995-12-31

    In recent years a decline in mussel populations has been documented in many areas, particularly in contaminated environments. Mussels are particularly vulnerable to exposure to xenobiotics in sediment and/or water because of their modes of feeding and respiration and close association with sediments. Because of this potential for exposure, their apparent sensitivity to xenobiotics, and their ease in collection and handling, mussels are an excellent species for in situ biomonitoring. Recently the authors have adapted an electrophoretic assay for detecting DNA strand breakage in freshwater mussels. Using this assay DNA damage was quantified in selected tissues in two mussel species, Quadrula quadrula and Anodonta grandis, following subchronic laboratory exposures to lead and benzo[a]pyrene. Current experiments involve exposing mussels in situ in polyethylene cages and exposure racks in several environments containing genotoxic agents, including a fly ash settling pond and a site contaminated with mercury. Mussels will be exposed for 1 week to 3 months and sampled at 2 to 4week intervals. Upon removal mussels will be dissected, and mantle, adductor muscle, and foot tissue will be analyzed for DNA strand breakage and xenobiotic residues. These data will be compared with laboratory exposures to single compounds conducted over the same exposure durations.

  13. Chemical morphology of Areca nut characterized directly by Fourier transform near-infrared and mid-infrared microspectroscopic imaging in reflection modes.

    PubMed

    Chen, Jian-Bo; Sun, Su-Qin; Zhou, Qun

    2016-12-01

    Fourier transform near-infrared (NIR) and mid-infrared (MIR) imaging techniques are essential tools to characterize the chemical morphology of plant. The transmission imaging mode is mostly used to obtain easy-to-interpret spectra with high signal-to-noise ratio. However, the native chemical compositions and physical structures of plant samples may be altered when they are microtomed for the transmission tests. For the direct characterization of thick plant samples, the combination of the reflection NIR imaging and the attenuated total reflection (ATR) MIR imaging is proposed in this research. First, the reflection NIR imaging method can explore the whole sample quickly to find out typical regions in small sizes. Next, each small typical region can be measured by the ATR-MIR imaging method to reveal the molecular structures and spatial distributions of compounds of interest. As an example, the chemical morphology of Areca nut section is characterized directly by the above approach. PMID:27374557

  14. Direction finding and suppression of vector-scalar sound signals in shallow water taking into account their correlation and mode structure

    NASA Astrophysics Data System (ADS)

    Belov, A. I.; Kuznetsov, G. N.

    2016-05-01

    The correlation of low-frequency sound signals from towed tonal low-frequency sources at the output of the scalar and vector channels is studied in shallow water. The correlation of the scalar field and signal received by a horizontally oriented vector receiver on average is 0.92-0.99; correlation with the signal received by a vertical vector receiver decreases to 0.66-85. When scalar fields or horizontal projections of the vibration velocity vector with application of the aperture synthesis algorithm are used, 3-5 normal waves are isolated; when the vertical component is used, 7-9 modes. It is demonstrated that the high signal correlation ensures direction-finding accuracy and suppression of strongly noise-emitting moving sources by 20-30 dB or more if the cardioid is directed at the source according to the zone of the minimum.

  15. Genotoxicity Studies Performed in the Ecuadorian Population

    PubMed Central

    Paz-y-Miño, César; Cumbal, Nadia; Sánchez, María Eugenia

    2012-01-01

    Genotoxicity studies in Ecuador have been carried out during the past two decades. The focuses of the research were mainly the area of environmental issues, where the populations have been accidentally exposed to contaminants and the area of occupational exposure of individuals at the workplace. This paper includes studies carried out in the population of the Amazon region, a zone known for its rich biodiversity as well as for the ecological damage caused by oil spills and chemical sprayings whose consequences continue to be controversial. Additionally, we show the results of studies comprised of individuals occupationally exposed to toxic agents in two very different settings: flower plantation workers exposed to pesticide mixtures and X-ray exposure of hospital workers. The results from these studies confirm that genotoxicity studies can help evaluate current conditions and prevent further damage in the populations exposed to contaminants. As such, they are evidence of the need for biomonitoring employers at risk, stricter law enforcement regarding the use of pesticides, and increasingly conscientious oil extraction activities. PMID:22496977

  16. Genotoxicity of dried Hoodia parviflora aerial parts.

    PubMed

    Lynch, Barry; Lau, Annette; Baldwin, Nigel; Hofman-Hüther, Hana; Bauter, Mark R; Marone, Palma Ann

    2013-05-01

    Hoodia parviflora is being developed commercially for use in weight loss food and dietary supplement products. Its effects are ascribed to a number of glycosides that have been shown to be present in plant extracts from several Hoodia species, the best known of which is H. gordonii. H. parviflora has been identified as an alternative to H. gordonii, and, as part of the process to develop H. parviflora, in vitro genotoxicity tests, as recommended by recent European Food Safety Authority guidance, were conducted on a dried powder preparation of H. parviflora aerial parts. The preparation was tested for reverse mutation at doses up to 5,000μg/plate in Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537, and in Escherichia coli WP2 uvrA TA, both in the presence and in the absence of an exogenous source of metabolic activation (rat liver S9). In addition, the dried powder was evaluated in an in vitro cytotoxicity chromosome aberration assay using human lymphocytes. Test conditions included both a 4 (up to 2500μg/mg) and 44-h exposure period (up to 1000μg/mg) and the incorporation of an exogenous source of metabolic activation (4-h exposure only). H. parviflora dried powder was non-genotoxic in both in vitro assays. PMID:23348409

  17. A novel PWM control for a bi-directional full-bridge DC-DC converter with smooth conversion mode transitions

    NASA Astrophysics Data System (ADS)

    Lorentz, V. R. H.; Schwarzmann, H.; März, M.; Bauer, A. J.; Ryssel, H.; Frey, L.; Poure, P.; Braun, F.

    2011-08-01

    A novel CMOS integrated pulse-width modulation (PWM) control circuit allowing smooth transitions between conversion modes in full-bridge based bi-directional DC-DC converters operating at high switching frequencies is presented. The novel PWM control circuit is able to drive full-bridge based DC-DC converters performing step-down (i.e. buck) and step-up (i.e. boost) voltage conversion in both directions, thus allowing charging and discharging of the batteries in mobile systems. It provides smooth transitions between buck, buck-boost and boost modes. Additionally, the novel PWM control loop circuit uses a symmetrical triangular carrier, which overcomes the necessity of using an output phasing circuit previously required in PWM controllers based on sawtooth oscillators. The novel PWM control also enables to build bi-directional DC-DC converters operating at high switching frequencies (i.e. up to 10 MHz and above). Finally, the proposed PWM control circuit also allows the use of an average lossless inductor-current sensor for sensing the average load current even at very high switching frequencies. In this article, the proposed PWM control circuit is modelled and the integrated CMOS schematic is given. The corresponding theory is analysed and presented in detail. The circuit simulations realised in the Cadence Spectre software with a commercially available 0.18 µm mixed-signal CMOS technology from UMC are shown. The PWM control circuit was implemented in a monolithic integrated bi-directional CMOS DC-DC converter ASIC prototype. The fabricated prototype was tested experimentally and has shown performances in accordance with the theory.

  18. Spectral Discrimination of Fine and Coarse Mode Aerosol Optical Depth from AERONET Direct Sun Data of Singapore and South-East Asia

    NASA Astrophysics Data System (ADS)

    Salinas Cortijo, S.; Chew, B.; Liew, S.

    2009-12-01

    Aerosol optical depth combined with the Angstrom exponent and its derivative, are often used as a qualitative indicator of aerosol particle size, with Angstrom exp. values greater than 2 indicating small (fine mode) particles associated with urban pollution and bio-mass burning. Around this region, forest fires are a regular occurrence during the dry season, specially near the large land masses of Sumatra and Borneo. The practice of clearing land by burning the primary and sometimes secondary forest, results in a smog-like haze covering large areas of regional cities such as cities Singapore, Kuala Lumpur and sometimes the south of Thailand, often reducing visibility and increasing health problems for the local population. In Singapore, the sources of aerosols are mostly from fossil fuel burning (energy stations, incinerators, urban transport etc.) and from the industrial and urban areas. The proximity to the sea adds a possible oceanic source. However, as stated above and depending on the time of the year, there can be a strong bio-mass component coming from forest fires from various regions of the neighboring countries. Bio-mass related aerosol particles are typically characterized by showing a large optical depth and small, sub-micron particle size distributions. In this work, we analyze three years of direct Sun measurements performed with a multi-channel Cimel Sun-Photometer (part of the AERONET network) located at our site. In order to identify bio-mass burning events in this region, we perform a spectral discrimination between coarse and fine mode optical depth; subsequently, the fine mode parameters such as optical depth, optical ratio and fine mode Angstrom exponents (and its derivative) are used to identify possible bio-mass related events within the data set.

  19. Development of an integrated sampler based on direct 222Rn/ 220Rn progeny sensors in flow-mode for estimating unattached/attached progeny concentration

    NASA Astrophysics Data System (ADS)

    Mishra, Rosaline; Sapra, B. K.; Mayya, Y. S.

    2009-11-01

    A flow-mode integrated sampler consisting of a wire-mesh and filter-paper array along with passive solid state nuclear track detectors has been developed for estimating unattached and attached fraction of 222Rn/ 220Rn progeny concentration. The essential element of this sampler is the direct 222Rn/ 220Rn progeny sensor (DRPS/DTPS), which is an absorber-mounted-LR115 type nuclear track detector that selectively registers the alpha particles emitted from the progeny deposited on its surface. During sampling at a specified flow-rate, the unattached progeny is captured on the wire-mesh; while the attached progeny gets transmitted and is captured on the filter-paper. The alpha particles emitted by the deposited progeny atoms are registered on the sensors placed at a specified distance facing the wire-mesh and the filter-paper, respectively. The various steps involved in the development of this flow-mode direct progeny sampler such as the optimization of the sampling rate and the distance between the sensor and the deposition substrate are discussed. The sensitivity factor of the DTPS-loaded sampler for 220Rn progeny deposited on the wire-mesh and filter-paper is found to be 23.77 ± 0.64 (track cm -2 h -1) (Bq m -3) -1 and 22.30 ± 0.18 (track cm -2 h -1) (Bq m -3) -1, respectively; while that of DRPS-loaded sampler for 222Rn progeny deposition, is 3.03 ± 0.14 (track cm -2 h -1) (Bq m -3) -1 and 2.08 ± 0.07 (track cm -2 h -1) (Bq m -3) -1, respectively. The highlight of this flow-mode sampler is its high sensitivity and that it utilizes the passive technique for estimating the unattached and attached progeny concentration, thus doing away with the alpha counting procedures.

  20. Genotoxicity assessment of five tremorgenic mycotoxins (fumitremorgen B, paxilline, penitrem A, verruculogen, and verrucosidin) produced by molds isolated from fermented meats.

    PubMed

    Sabater-Vilar, Monica; Nijmeijer, Sandra; Fink-Gremmels, Johanna

    2003-11-01

    A number of toxinogenic fungal species, particularly producers of tremorgenic mycotoxins, have been isolated from traditional fermented meats. Tremorgenic mycotoxins are a group of fungal metabolites known to act on the central nervous system, causing sustained tremors, convulsions, and death in animals. However, the mode of action of these mycotoxins has not been elucidated in detail, and their genotoxic capacity has hardly been investigated. Because genotoxicity is one of the most prominent toxicological end points in food safety testing, we assessed the genotoxicity of five tremorgenic mycotoxins (fumitremorgen B, paxilline, penitrem A, verrucosidin, and verruculogen) associated with molds found in fermented meats. The mycotoxins were tested in two short-term in vitro assays with the use of different genotoxic end points in different phylogenetic systems (the Ames Salmonella/mammalian-microsome assay and the single-cell gel electrophoresis assay of human lymphocytes). According to the results obtained in this study, all of the investigated mycotoxins except penitrem A exhibited a certain degree of genotoxicity. Verrucosidin appeared to have the highest toxic potential, testing positive in both assays. Verruculogen tested positive in the Salmonella/mammalian-microsome assay, and paxilline and fumitremorgen B caused DNA damage in human lymphocytes. The use of fungal starter cultures to avoid tremorgen contamination in fermented meats is recommended. PMID:14627292

  1. High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy.

    PubMed

    Hihath, Sahar; Santala, Melissa K; Cen, Xi; Campbell, Geoffrey; van Benthem, Klaus

    2016-01-01

    Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combination of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Our results allow for improved safety during laser ablation in manufacturing and medical applications. PMID:26965073

  2. High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy

    PubMed Central

    Hihath, Sahar; Santala, Melissa K.; Cen, Xi; Campbell, Geoffrey; van Benthem, Klaus

    2016-01-01

    Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combination of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Our results allow for improved safety during laser ablation in manufacturing and medical applications. PMID:26965073

  3. High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy

    DOE PAGESBeta

    Hihath, Sahar; Santala, Melissa K.; Cen, Xi; Campbell, Geoffrey; van Benthem, Klaus

    2016-03-11

    Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combinationmore » of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Ultimately, our results allow for improved safety during laser ablation in manufacturing and medical applications.« less

  4. High speed direct imaging of thin metal film ablation by movie-mode dynamic transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Hihath, Sahar; Santala, Melissa K.; Cen, Xi; Campbell, Geoffrey; van Benthem, Klaus

    2016-03-01

    Obliteration of matter by pulsed laser beams is not only prevalent in science fiction movies, but finds numerous technological applications ranging from additive manufacturing over machining of micro- and nanostructured features to health care. Pulse lengths ranging from femtoseconds to nanoseconds are utilized at varying laser beam energies and pulse lengths, and enable the removal of nanometric volumes of material. While the mechanisms for removal of material by laser irradiation, i.e., laser ablation, are well understood on the micrometer length scale, it was previously impossible to directly observe obliteration processes on smaller scales due to experimental limitations for the combination of nanometer spatial and nanosecond temporal resolution. Here, we report the direct observation of metal thin film ablation from a solid substrate through dynamic transmission electron microscopy. Quantitative analysis reveals liquid-phase dewetting of the thin-film, followed by hydrodynamic sputtering of nano- to submicron sized metal droplets. We discovered unexpected fracturing of the substrate due to evolving thermal stresses. This study confirms that hydrodynamic sputtering remains a valid mechanism for droplet expulsion on the nanoscale, while irradiation induced stress fields represent limit laser processing of nanostructured materials. Our results allow for improved safety during laser ablation in manufacturing and medical applications.

  5. Anti-genotoxic and free-radical scavenging activities of extracts from (Tunisian) Myrtus communis.

    PubMed

    Hayder, N; Abdelwahed, A; Kilani, S; Ammar, R Ben; Mahmoud, A; Ghedira, K; Chekir-Ghedira, L

    2004-11-14

    The effect of extracts from leaves of Myrtus communis on the SOS reponse induced by Aflatoxin B1 (AFB1) and Nifuroxazide was investigated in a bacterial assay system, i.e. the SOS chromotest with Escherichia coli PQ37. Aqueous extract, the total flavonoids oligomer fraction (TOF), hexane, chloroform, ethyl acetate and methanol extracts and essential oil obtained from M. communis significantly decreased the SOS response induced by AFB1 (10 microg/assay) and Nifuroxazide (20 microg/assay). Ethyl acetate and methanol extracts showed the strongest inhibition of the induction of the SOS response by the indirectly genotoxic AFB1. The methanol and aqueous extracts exhibited the highest level of protection towards the SOS-induced response by the directly genotoxic Nifuroxazide. In addition to anti-genotoxic activity, the aqueous extract, the TOF, and the ethyl acetate and methanol extracts showed an important free-radical scavenging activity towards the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. These results suggest the future utilization of these extracts as additives in chemoprevention studies. PMID:15474415

  6. In vitro evaluation of cytotoxicity and genotoxicity of a commercial titanium alloy for dental implantology.

    PubMed

    Velasco-Ortega, Eugenio; Jos, Angeles; Cameán, Ana M; Pato-Mourelo, Jesús; Segura-Egea, Juan J

    2010-09-30

    Titanium and its alloys have many applications in dentistry, being used in orthodontics, endodontics, prosthetics and implantology. But the use in the biomedical field depends on its biocompatibility, as the Council Directive 93/42/EEC of 14 June 1993 concerning medical devices has established. The aim of this study was to investigate the cytotoxicity and genotoxicity of a commercial titanium/aluminium/vanadium alloy (Ti-6Al-4V) developed by an innovative sand-blast process with aluminium oxide, and nitric-acid passivation. This procedure created a material with an average surface roughness of 1.73±0.16μm with applications in dental implants. International Organization for Standardization (ISO) procedures 7405:2008 and 10993-5:2009 were used to perform the cytotoxicity tests, and bacterial and cell-mutation assays to evaluate genotoxicity. The results show that this titanium alloy (Ti-6Al-4V) was neither cytotoxic nor genotoxic in any of the tests performed. It can be concluded that this new Ti-6Al-4V material with the roughness characteristics specified shows good biocompatibility and can be considered of choice in dental implantology. PMID:20615479

  7. Large-scale genotoxicity assessments in the marine environment

    SciTech Connect

    Hose, J.E.

    1994-12-01

    There are a number of techniques for detecting genotoxicity in the marine environment, and many are applicable to large-scale field assessments. Certain tests can be used to evaluate responses in target organisms in situ while others utilize surrogate organisms exposed to field samples in short-term laboratory bioassays. Genotoxicity endpoints appear distinct from traditional toxicity endpoints, but some have chemical or ecotoxicologic correlates. One versatile end point, the frequency of anaphase aberrations, has been used in several large marine assessments to evaluate genotoxicity in the New York Bight, in sediment from San Francisco Bay, and following the Exxon Valdez oil spill. 31 refs., 2 tabs.

  8. Large-scale genotoxicity assessments in the marine environment.

    PubMed

    Hose, J E

    1994-12-01

    There are a number of techniques for detecting genotoxicity in the marine environment, and many are applicable to large-scale field assessments. Certain tests can be used to evaluate responses in target organisms in situ while others utilize surrogate organisms exposed to field samples in short-term laboratory bioassays. Genotoxicity endpoints appear distinct from traditional toxicity endpoints, but some have chemical or ecotoxicologic correlates. One versatile end point, the frequency of anaphase aberrations, has been used in several large marine assessments to evaluate genotoxicity in the New York Bight, in sediment from San Francisco Bay, and following the Exxon Valdez oil spill. PMID:7713029

  9. Ultrafast direct modulation of transverse-mode coupled-cavity VCSELs far beyond the relaxation oscillation frequency

    NASA Astrophysics Data System (ADS)

    Dalir, Hamed; Koyama, Fumio

    2014-02-01

    A novel approach for bandwidth augmentation for direct modulation of VCSELs using transverse-coupled-cavity (TCC) scheme is raised, which enables us to tailor the modulation-transfer function. The base structure is similar to that of 3QW VCSELs with 980 nm wavelength operation. While the bandwidth of conventional VCSELs was limited by 9-10 GHz, the 3-dB bandwidth of TCC VCSEL with aperture diameters of 8.5×8.5μm2 and 3×3μm2 are increased by a factor of 3 far beyond the relaxation-oscillation frequency. Our current bandwidth achievement on the larger aperture size is 29 GHz which is limited by the used photo-detector. To the best of our knowledge this is the fastest 980 nm VCSEL.

  10. Evaluation of genotoxic and antigenotoxic effects of hydroalcoholic extracts of Zuccagnia punctata Cav.

    PubMed

    Zampini, Iris Catiana; Villarini, Milena; Moretti, Massimo; Dominici, Luca; Isla, María Inés

    2008-01-17

    Zuccagnia punctata Cav. (Fabaceae), a widely used plant species in Argentine folk medicine, has been shown to have a broad spectrum of antibacterial, antifungal, antioxidant and cytoprotective activities. In this study, the hydroalcoholic extract of Zuccagnia punctata and 2',4'-dihydroxychalcone isolated from it were investigated for genotoxicity/antigenotoxicity in the in vitro comet assay test on human hepatoma HepG2 cells. No acute toxicity of the extract could be determined. HepG2 cells were treated with three different concentrations (2.5, 5.0 and 10.0 microg/mL) or 2',4'-dihydroxychalcone (0.01, 0.10 and 1.00 microg/mL). To explore the potential mechanisms of action, two approaches were followed: co-treatment with 4-nitroquinoline-N-oxyde (4-NQO), a direct genotoxic compound, and a pre-treatment protocol with benzo[a]pyrene (B[a]P), an indirect genotoxic compound. The natural products neither affected cell viability nor induced DNA damage in the concentration range tested. Zuccagnia punctata tinctures were able to diminish the DNA damage induced in HepG2 cells by 4-NQO and B[a]P in 31% and 10%, respectively at 10 microg/mL. Pre-treatment of HepG2 cells with 2',4'-dihydroxychalcone was highly effective in decreasing B[a]P-induced DNA damage at a statistically significant level, with an almost clear dose-response relationship. The inhibition values were 28.2-43.9% for the tested concentrations of 0.01-1 microg/mL, respectively. The results clearly indicate that the phytoextract from Zuccagnia punctata, under the experimental conditions tested, is not genotoxic and that 2',4'-dihydroxychalcone contributes to a high degree to the antigenotoxic effects of Zuccagnia punctata tincture. PMID:18023546

  11. Evaluating microRNA profiles reveals discriminative responses following genotoxic or non-genotoxic carcinogen exposure in primary mouse hepatocytes.

    PubMed

    Rieswijk, Linda; Brauers, Karen J J; Coonen, Maarten L J; van Breda, Simone G J; Jennen, Danyel G J; Kleinjans, Jos C S

    2015-11-01

    Chemical carcinogenesis can be induced by genotoxic (GTX) or non-genotoxic (NGTX) carcinogens. GTX carcinogens have a well-described mode of action. However, the complex mechanisms by which NGTX carcinogens act are less clear and may result in conflicting results between species [e.g. Wy-14,643 (Wy)]. We hypothesise that common microRNA response pathways exist for each class of carcinogenic agents. Therefore, this study compares and integrates mRNA and microRNA expression profiles following short term acute exposure (24 and 48h) to three GTX [aflatoxin B1 (AFB1), benzo[a]pyrene (BaP) and cisplatin (CisPl)] or three NGTX (2,3,7,8-tetrachloordibenzodioxine (TCDD), cyclosporine A (CsA) and Wy) carcinogens in primary mouse hepatocytes. Discriminative gene sets, microRNAs (not for 24h) and processes were identified following 24 and 48h of exposure. From the three discriminative microRNAs found following 48h of exposure, mmu-miR-503-5p revealed to have an interaction with mRNA target gene cyclin D2 (Ccnd2 - 12444) which was involved in the discriminative process of p53 signalling and metabolism. Following exposure to NGTX carcinogens Mmu-miR-503-5p may have an oncogenic function by stimulating Ccnd2 possibly leading to a tumourigenic cell cycle progression. By contrast, after GTX carcinogen exposure it may have a tumour-suppressive function (repressing Ccnd2) leading to cell cycle arrest and to increased DNA repair activities. In addition, compound-specific microRNA-mRNA interactions [mmu-miR-301b-3p-Papss2 (for AFB1), as well as mmu-miR-29b-3p-Col4a2 and mmu-miR-24-3p-Flna (for BaP)] were found to contribute to a better understanding of microRNAs in cell cycle arrest and the impairment of the DNA damage repair, an important hallmark of GTX-induced carcinogenesis. Overall, our results indicate that microRNAs represent yet another relevant intracellular regulatory level in chemical carcinogenesis. PMID:25976910

  12. High-throughput in vivo genotoxicity testing: an automated readout system for the somatic mutation and recombination test (SMART).

    PubMed

    Lombardot, Benoit; Oh, Chun-Taek; Kwak, Jihoon; Genovesio, Auguste; Kang, Myungjoo; Hansen, Michael Adsett Edberg; Han, Sung-Jun

    2015-01-01

    Genotoxicity testing is an important component of toxicity assessment. As illustrated by the European registration, evaluation, authorization, and restriction of chemicals (REACH) directive, it concerns all the chemicals used in industry. The commonly used in vivo mammalian tests appear to be ill adapted to tackle the large compound sets involved, due to throughput, cost, and ethical issues. The somatic mutation and recombination test (SMART) represents a more scalable alternative, since it uses Drosophila, which develops faster and requires less infrastructure. Despite these advantages, the manual scoring of the hairs on Drosophila wings required for the SMART limits its usage. To overcome this limitation, we have developed an automated SMART readout. It consists of automated imaging, followed by an image analysis pipeline that measures individual wing genotoxicity scores. Finally, we have developed a wing score-based dose-dependency approach that can provide genotoxicity profiles. We have validated our method using 6 compounds, obtaining profiles almost identical to those obtained from manual measures, even for low-genotoxicity compounds such as urethane. The automated SMART, with its faster and more reliable readout, fulfills the need for a high-throughput in vivo test. The flexible imaging strategy we describe and the analysis tools we provide should facilitate the optimization and dissemination of our methods. PMID:25830368

  13. High-Throughput In Vivo Genotoxicity Testing: An Automated Readout System for the Somatic Mutation and Recombination Test (SMART)

    PubMed Central

    Kwak, Jihoon; Genovesio, Auguste; Kang, Myungjoo; Hansen, Michael Adsett Edberg; Han, Sung-Jun

    2015-01-01

    Genotoxicity testing is an important component of toxicity assessment. As illustrated by the European registration, evaluation, authorization, and restriction of chemicals (REACH) directive, it concerns all the chemicals used in industry. The commonly used in vivo mammalian tests appear to be ill adapted to tackle the large compound sets involved, due to throughput, cost, and ethical issues. The somatic mutation and recombination test (SMART) represents a more scalable alternative, since it uses Drosophila, which develops faster and requires less infrastructure. Despite these advantages, the manual scoring of the hairs on Drosophila wings required for the SMART limits its usage. To overcome this limitation, we have developed an automated SMART readout. It consists of automated imaging, followed by an image analysis pipeline that measures individual wing genotoxicity scores. Finally, we have developed a wing score-based dose-dependency approach that can provide genotoxicity profiles. We have validated our method using 6 compounds, obtaining profiles almost identical to those obtained from manual measures, even for low-genotoxicity compounds such as urethane. The automated SMART, with its faster and more reliable readout, fulfills the need for a high-throughput in vivo test. The flexible imaging strategy we describe and the analysis tools we provide should facilitate the optimization and dissemination of our methods. PMID:25830368

  14. Genotoxicity testing of Maillard reaction products.

    PubMed

    Shibamoto, T

    1989-01-01

    Since the development of short-term genotoxicity tests such as the Ames assay, the mutagenicity of Maillard reaction products has been tested extensively. Some products have exhibited strong activity. For example, one of the earliest studies demonstrated some mutagenic activity in a dichloromethane extract of a D-glucose/ammonia Maillard model system. Many researchers have attempted to pinpoint the principal chemical(s) of mutagenicity of the Maillard products using various sugar-amino acid browning model systems over last two decades. However, no mutagenic individual Maillard product has been isolated and identified. Nitrite has been also used as a reactant in browning reaction model systems, primarily to investigate the formation of potentially mutagenic or carcinogenic N-nitroso compounds. Recently some potent mutagens isolated from pyrolyzed amino acids or proteins have begun to receive attention as Maillard reaction products. PMID:2675034

  15. Monitoring of genotoxicity in marine zooplankton induced by toxic metals in Ennore estuary, Southeast coast of India.

    PubMed

    Goswami, Prasun; Thirunavukkarasu, Subramani; Godhantaraman, Nallamuthu; Munuswamy, Natesan

    2014-11-15

    The present study provides preliminary in-situ data on genetic integrity of marine zooplankton. Paracalanus parvus, Oithona rigida and Euterpina acutifrons were collected during four different seasons (summer, pre-monsoon, monsoon and post-monsoon) from 2011 to 2012 in Ennore and Kovalum estuaries. DNA damage levels in different zooplankton were analyzed by comet assay and were correlated with different environmental stressors. Spatial and temporal variations in DNA damage was observed in all the species. Zooplankton from Ennore estuary showed significantly lower genetic integrity. Particulate, sediment, and zooplankton fractions of Pb, Ni, Cu, Cr and Co were associated with high DNA damage during the period of lowest pH, salinity and dissolved oxygen. Zn and Cd showed lower genotoxic impact than the other metals. Feeding modes strongly influenced the genetic integrity in the zooplankton species studied. These results support the use of comet assay as a tool in effectively monitoring genotoxicity in marine plankton communities. PMID:25287225

  16. THE GENOTOXICITY OF AMBIENT OUTDOOR AIR, A REVIEW: SALMONELLA MUTAGENICITY

    EPA Science Inventory

    The genotoxicity of ambient outdoor air, a review: Salmonella mutagenicity

    Abstract
    Mutagens in urban air pollution come from anthropogenic sources (especially combustion sources) and are products of airborne chemical reactions. Bacterial mutation tests have been used ...

  17. Titanium dioxide nanoparticles cause genotoxicity in human lung epithelial cells

    EPA Science Inventory

    The use of engineered nanoparticles in consumer products is steadily increasing. However, the health effects of exposure to these nanoparticles are not thoroughly understood. This study investigated the genotoxicity of six titanium dioxide and two cerium oxide nanoparticles of va...

  18. Genotoxic and mutagenic potential of nitramines.

    PubMed

    Fjellsbø, Lise Marie; Verstraelen, Sandra; Kazimirova, Alena; Van Rompay, An R; Magdolenova, Zuzana; Dusinska, Maria

    2014-10-01

    Climate change is one of the major challenges in the world today. To reduce the amount of CO2 released into the atmosphere, CO2 at major sources, such as power plants, can be captured. Use of aqueous amine solutions is one of the most promising methods for this purpose. However, concerns have been raised regarding its impacts on human health and the environment due to the degradation products, such as nitrosamines and nitramines that may be produced during the CO2 capture process. While several toxicity studies have been performed investigating nitrosamines, little is known about the toxic potential of nitramines. In this study a preliminary screening was performed of the genotoxic and mutagenic potential of nitramines most likely produced during amine based CO2 capture; dimethylnitramine (DMA-NO2), methylnitramine (MA-NO2), ethanolnitramine (MEA-NO2), 2-methyl-2-(nitramino)-1-propanol (AMP-NO2) and piperazine nitramine (PZ-NO2), by the Bacterial Reverse Mutation (Ames) Test, the Cytokinesis Block Micronucleus (CBMN) Assay and the in vitro Single-Cell Gel Electrophoresis (Comet) Assay. MA-NO2 and MEA-NO2 showed mutagenic potential in the Ames test and a weak genotoxic response in the CBMN Assay. AMP-NO2 and PZ-NO2 significantly increased the amount of DNA strand breaks; however, the level of breaks was below background. Most previous studies on nitramines have been performed on DMA-NO2, which in this study appeared to be the least potent nitramine. Our results indicate that it is important to investigate other nitramines that are more likely to be produced during CO2 capture, to ensure that the risk is realistically evaluated. PMID:25042035

  19. An Eco-Friendly Direct Injection HPLC Method for Methyldopa Determination in Serum by Mixed-Mode Chromatography Using a Single Protein-Coated Column.

    PubMed

    Emara, Samy; Masujima, Tsutomu; Zarad, Walaa; Kamal, Maha; Fouad, Marwa; El-Bagary, Ramzia

    2015-09-01

    A simple, rapid and environment-friendly direct injection HPLC method for the determination of methyldopa (MTD) in human serum has been developed and validated. The method was based on cleanup and separation of MTD from serum by mixed-mode liquid chromatography using a single protein-coated TSK gel ODS-80 TM analytical column (50 × 4.0 mm i.d., 5 µm). The protein-coated column exhibited excellent resolution, selectivity and functioned in two chromatographic modes: size-exclusion chromatography [i.e., solid-phase extraction (SPE) for serum proteins] and reversed-phase chromatography for the final separation of MTD. SPE and HPLC separation were carried out simultaneously with a green mobile phase consisting of acetate buffer (0.1 M, pH 2.4) at a flow rate of 1 mL/min and at room temperature (23 ± 1°C). The eluent was monitored at emission and excitation wavelengths of 320 and 270 nm, respectively. A calibration curve was linear over the range of 0.1-30 µg/mL with a detection limit of 0.027 µg/mL. This online SPE method was successfully applied to real samples obtained from patients receiving MTD therapy. PMID:25834172

  20. Structure of Bacillus subtilis γ-glutamyltranspeptidase in complex with acivicin: diversity of the binding mode of a classical and electrophilic active-site-directed glutamate analogue

    SciTech Connect

    Ida, Tomoyo; Suzuki, Hideyuki; Fukuyama, Keiichi; Hiratake, Jun; Wada, Kei

    2014-02-01

    The binding modes of acivicin, a classical and an electrophilic active-site-directed glutamate analogue, to bacterial γ-glutamyltranspeptidases were found to be diverse. γ-Glutamyltranspeptidase (GGT) is an enzyme that plays a central role in glutathione metabolism, and acivicin is a classical inhibitor of GGT. Here, the structure of acivicin bound to Bacillus subtilis GGT determined by X-ray crystallography to 1.8 Å resolution is presented, in which it binds to the active site in a similar manner to that in Helicobacter pylori GGT, but in a different binding mode to that in Escherichia coli GGT. In B. subtilis GGT, acivicin is bound covalently through its C3 atom with sp{sup 2} hybridization to Thr403 O{sup γ}, the catalytic nucleophile of the enzyme. The results show that acivicin-binding sites are common, but the binding manners and orientations of its five-membered dihydroisoxazole ring are diverse in the binding pockets of GGTs.

  1. Are genotoxic carcinogens more potent than nongenotoxic carcinogens?

    PubMed Central

    Parodi, S; Malacarne, D; Romano, P; Taningher, M

    1991-01-01

    In this report we have raised the question whether genotoxic carcinogens are more potent than nongenotoxic carcinogens when studied in long-term carcinogenicity assays in rodents. To build a large database of compounds for which both carcinogenicity and genotoxicity had been investigated, we have used a database produced by Gold and co-workers for carcinogenic potency data (975 chemicals) and a database produced by Würgler for genotoxicity data (2834 chemicals). Considering compounds positive or negative in at least three short-term tests and in at least 75% of available tests, we could define 67 genotoxic carcinogens and 46 nongenotoxic carcinogens. Carcinogenic potency of genotoxic carcinogens was about 50 times higher than carcinogenic potency of nongenotoxic carcinogens. Our results are different from the results of Tennant et al.; their database (24 genotoxic carcinogens and 12 nongenotoxic carcinogens compatible with our definition) seems to suggest that there is practically no difference in potency between genotoxic and nongenotoxic carcinogens. The two databases have only four compounds in common and are also different in terms of number of elements for different chemical classes. Nitrosocompounds, nitrogen mustards, hydrazine derivatives, and polycyclic aromatic hydrocarbons are not represented in the database of Tennant. The overall impression from our analysis is that the usefulness of short-term tests of genotoxicity could be significantly better than what has been suggested by the previous work of Tennant et al. because these tests tend to detect, at least for many important chemical classes, the most potent carcinogens. This consideration may not be valid for certain classes of chemicals. PMID:1821372

  2. Rapid fingerprinting of sterols and related compounds in vegetable and animal oils and phytosterol enriched- margarines by transmission mode direct analysis in real time mass spectrometry.

    PubMed

    Alberici, Rosana M; Fernandes, Gabriel D; Porcari, Andréia M; Eberlin, Marcos N; Barrera-Arellano, Daniel; Fernández, Facundo M

    2016-11-15

    Plant-derived sterols, often referred to as phytosterols, are important constituents of plant membranes where they assist in maintaining phospholipid bilayer stability. Consumption of phytosterols has been suggested to positively affect human health by reducing cholesterol levels in blood via inhibition of its absorption in the small intestine, thus protecting against heart attack and stroke. Sterols are challenging analytes for mass spectrometry, since their low polarity makes them difficult to ionize by both electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI), typically requiring derivatization steps to overcome their low ionization efficiencies. We present a fast and reliable method to characterize the composition of phytosterols in vegetable oils and enriched margarines. The method requires no derivatization steps or sample extraction procedures thanks to the use of transmission mode direct analysis in real time mass spectrometry (TM-DART-MS). PMID:27283681

  3. Direct chemical-analysis of uv laser-ablation products of organic polymers by using selective ion monitoring mode in gas-chromatography mass-spectrometry

    USGS Publications Warehouse

    Cho, Yirang; Lee, H.W.; Fountain, S.T.; Lubman, D.M.

    1994-01-01

    Trace quantities of laser ablated organic polymers were analyzed by using commercial capillary column gas chromatography/mass spectrometry; the instrument was modified so that the laser ablation products could be introduced into the capillary column directly and the constituents of each peak in the chromatogram were identified by using a mass spectrometer. The present study takes advantage of the selective ion monitoring mode for significantly improving the sensitivity of the mass spectrometer as a detector, which is critical in analyzing the trace quantities and confirming the presence or absence of the species of interest in laser ablated polymers. The initial composition of the laser ablated polymers was obtained by using an electron impact reflectron time-of-flight mass spectrometer and the possible structure of the fragments observed in the spectra was proposed based on the structure of the polymers.

  4. A 250 MHz, high power mode-locked Nd:GdVO4 oscillator with low timing jitter under 879 nm direct pumping

    NASA Astrophysics Data System (ADS)

    Zhang, F. F.; Zuo, J. W.; Wang, Z. M.; Yang, J.; Cheng, H. L.; Zong, N.; Yang, F.; Peng, Q. J.; Xu, Z. Y.

    2013-04-01

    We developed a high power mode-locked Nd:GdVO4 oscillator with low timing jitter directly pumped by an 879 nm diode. Under the absorbed pump power of 13.8 W, a maximum output power of 5.68 W at 1063 nm was obtained with a repetition rate of ˜250 MHz, corresponding to a slope efficiency of 78.7%. The measured pulse width and root mean square timing jitter at the output power of 5.35 W were 7.4 ps and 286 fs, respectively. To the best of our knowledge, this is the highest output power for a picosecond Nd:GdVO4 oscillator with low timing jitter.

  5. Correlations between embryotoxic and genotoxic effects of phenytoin in mice.

    PubMed

    Barcellona, P S; Barale, R; Campana, A; Zucconi, D; Rossi, V; Caranti, S

    1987-01-01

    The anticonvulsant drug phenytoin (DPH) has been suspected to produce embryotoxicity through an arene oxide intermediate. This drug was also found to be a genotoxic agent. These hypotheses were tested in pregnant mice modulating the phases I and II metabolizing enzymes. DPH was studied by assessing embryotoxicity, teratogenicity, and genotoxicity, the latter by the micronucleus test on the polychromatic erythrocytes of dams and fetuses. DPH embryotoxicity was potentiated by inhibiting both cytochrome P-450 and epoxide hydrase and decreased by inducing cytochrome P-450. Equivocal results were obtained by modulating cytochrome P-448. The main DPH metabolite, p-hydroxyphenytoin (HPPH), was ineffective both per se and after cytochrome induction or epoxide hydrase inhibition. DPH did not exert genotoxicity on the maternal organism, no matter which modulating agent was used. In the fetus, however, weak genotoxic effects were observed. These effects significantly increased with inhibition of epoxide hydrase; they disappeared with induction of both cytochromes P-448 and P-450 or with inhibition of the latter. No genotoxicity was exerted by HPPH, even when the enzymatic pattern was modulated. It is concluded that the major role in DPH embryotoxicity is played by the unchanged drug, while the presence of the arene oxide is determinant for genotoxic effects. PMID:2885938

  6. Evaluation of protective effect of amifostine on dacarbazine induced genotoxicity.

    PubMed

    Etebari, M; Jafarian-Dehkordi, A; Lame, V

    2015-01-01

    Anticancer therapy with alkylating agents has been used for many years. Dacarbazine (DTIC) as an alkylating agent is used alone or in combination with other chemotherapy drugs. In order to inhibit the formation of secondary cancers resulting from chemotherapy with DTIC, preventional strategies is necessary. The present study was undertaken to evaluate the genoprotective effect of amifostine on the genotoxic effects of DTIC in cell culture condition. To determine the optimum genotoxic concentration of DTIC, HepG2 cells were incubated with various DTIC concentrations including 5, 10 and 20 μg/ml for 2 h and the genotoxic effects were evaluated by the comet assay. The result of this part of the study showed that incubation of HepG2 cells with DTIC at 5 μg/ml was sufficient to produce genotoxic effect. In order to determine the protective effects of amifostine on genotoxicity induced by DTIC, HepG2 cells were incubated with different concentrations of amifostine (2, 3 and 5 mg/ml) for 1 h which was followed by incubation with DTIC at 5 μg/ml for 2 h. One hour incubation of cells with different concentrations of amifostine before incubation with DITC indicated that at least 5 mg/ml concentration of amifostine can prevent genotoxic effects induced by DTIC on HepG2 cells under described condition. In conclusion amifostine could prevent DNA damage induced by DTIC on HepG2 cells. PMID:26430459

  7. Quantification of umu genotoxicity level of urban river water.

    PubMed

    Kameya, T; Nagato, T; Nakagawa, K; Yamashita, D; Kobayashi, T; Fujie, K

    2011-01-01

    In recent years, the request of environmental safety management for carcinogenic substances, mutagenic substances and/or reproductive toxicity substances (CMR) has increased. This study focused on clarifying the genotoxicity level of environmental water and its release source by using the umu test provided in ISO13829. Although a genotoxicity index "induction ratio (IR)" is used in ISO13829, we normalised it to make it possible to compare various environmental water quantitatively to each other as a new index "genotoxic activity (GA=(IR-1)/Dose)". Sample water was collected and concentrated to 100 times or 1,000 times by a solid phase extraction method. As the test results, it was found that GA level in actual river water varied widely from less than the determination limit of 23 [1/L] to 1,100 [1/L] by quantitative comparison, and the value was also equivalent to more than 50 times the level of tap water. The GA level of household wastewater was not so high, but the levels of treated water from wastewater treatment plant (WTP) were from 220 [1/L] to 3,200 [1/L]. Raw sewage of some WTP shows high level genotoxicity. A part of genotoxicity substances, for example 50%, could be removed by conventional wastewater treatment, but it was not enough to reduce the water environmental load of genotoxicity. PMID:21278461

  8. Assessment of genotoxicity of Lannate-90® and its plant and animal metabolites in human lymphocyte cultures.

    PubMed

    Valencia-Quintana, Rafael; Gómez-Arroyo, Sandra; Sánchez-Alarcón, Juana; Milić, Mirta; Olivares, José Luis Gómez; Waliszewski, Stefan M; Cortés-Eslava, Josefina; Villalobos-Pietrini, Rafael; Calderón-Segura, María Elena

    2016-06-01

    This study evaluated direct and metabolic genotoxic effects caused by Lannate-90®, a methomyl-based formulation (90 % active ingredient), in human lymphocyte cultures using sister chromatid exchange assay (SCE). Two processes were used for the plant promutagens evaluation: in vivo activation, applying the insecticide systemically in plants for 4 h and subsequently adding plant metabolites containing extracts to lymphocyte cultures; and in vitro activation, where the insecticide was incubated with Vicia faba S10 mix plus human lymphocyte culture. Direct treatment with the insecticide significantly increased SCE frequency in human lymphocytes (250-750 mgL-1), with cellular death observed at 1000 mgL-1 concentration. Using the extracts of Vicia faba treated with Lannate-90® to treat human lymphocytes, a dose-response relationship was observed. In lymphocyte cultures treated directly with the insecticide for 2 h, a negative response was obtained. When S10 mix was added, SCE frequency did not change significantly. Meanwhile, a mixture of S9 mammalian metabolic mix and Lannate-90® increased the SCE frequency, with an observed concentration-dependent response. Although Lannate-90® induced cellular death at the highest concentrations, it did not cause a delay in cell proliferation in any of the treatments, confirming its genotoxic action. This study is one of the first to evaluate and compare the direct effect of Lannate-90® in two bioassays, animal and vegetal, and the effect of plant and animal metabolism on its genotoxic potential. PMID:27331299

  9. Genotoxic testing of titanium dioxide anatase nanoparticles using the wing-spot test and the comet assay in Drosophila.

    PubMed

    Carmona, Erico R; Escobar, Bibi; Vales, Gerard; Marcos, Ricard

    2015-01-15

    Titanium dioxide nanoparticles (TiO2 NPs) are widely used for preparations of sunscreens, cosmetics, food and personal care products. However, the possible genotoxic risk associated with this nano-scale material exposure is not clear, especially in whole organisms. In the present study, we explored the in vivo genotoxic activity of TiO2 NPs as well as their TiO2 bulk form using two well-established genotoxic assays, the wing spot test and the comet assay in Drosophila melanogaster. To determine the extent of tissue damage induced by TiO2 NPs in Drosophila larvae, the trypan blue dye exclusion test was also applied. Both compounds were supplied to third instar larvae by ingestion at concentration ranging from 0.08 to 1.60 mg/mL. The results obtained in the present study indicate that TiO2 NPs can reach and induce cytotoxic effects on midgut and imaginal disc tissues of larvae, but they do not promote genotoxicity in the wing-spot test of Drosophila. However, when both nano- and large-size forms of TiO2 were evaluated with the comet assay in Drosophila hemocytes, a significant increase in DNA damage, with a direct dose-response pattern, was observed for TiO2 NPs. The results obtained with the comet assay suggest that the primary DNA damage associated with TiO2 NPs exposure in Drosophila could be associated with specific physico-chemical properties of nano-TiO2, since no effects were observed with the bulk form. This study remarks the usefulness of using more than one genetic end-point in the evaluation of the genotoxic potential of nanomaterials. PMID:25726144

  10. Methylation of Lysine 9 in Histone H3 Directs Alternative Modes of Highly Dynamic Interaction of Heterochromatin Protein hHP1β with the Nucleosome*

    PubMed Central

    Munari, Francesca; Soeroes, Szabolcs; Zenn, Hans Michael; Schomburg, Adrian; Kost, Nils; Schröder, Sabrina; Klingberg, Rebecca; Rezaei-Ghaleh, Nasrollah; Stützer, Alexandra; Gelato, Kathy Ann; Walla, Peter Jomo; Becker, Stefan; Schwarzer, Dirk; Zimmermann, Bastian; Fischle, Wolfgang; Zweckstetter, Markus

    2012-01-01

    Binding of heterochromatin protein 1 (HP1) to the histone H3 lysine 9 trimethylation (H3K9me3) mark is a hallmark of establishment and maintenance of heterochromatin. Although genetic and cell biological aspects have been elucidated, the molecular details of HP1 binding to H3K9me3 nucleosomes are unknown. Using a combination of NMR spectroscopy and biophysical measurements on fully defined recombinant experimental systems, we demonstrate that H3K9me3 works as an on/off switch regulating distinct binding modes of hHP1β to the nucleosome. The methyl-mark determines a highly flexible and very dynamic interaction of the chromodomain of hHP1β with the H3-tail. There are no other constraints of interaction or additional multimerization interfaces. In contrast, in the absence of methylation, the hinge region and the N-terminal tail form weak nucleosome contacts mainly with DNA. In agreement with the high flexibility within the hHP1β-H3K9me3 nucleosome complex, the chromoshadow domain does not provide a direct binding interface. Our results report the first detailed structural analysis of a dynamic protein-nucleosome complex directed by a histone modification and provide a conceptual framework for understanding similar interactions in the context of chromatin. PMID:22815475